JP2012083279A - Torque detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a torque detection accuracy by detecting a rotation angle with high accuracy that is not influenced by an ambient temperature of a resolver even when one detection coil of two phases is disconnected.
A abnormality calculates the square root of the sum of the squares of the amplitudes of the sin phase and cos phase of the second resolver does not occur as a resolver amplitude _{K 2 · E 2 (S31)} , to the resolver amplitude _K 2 · _{E 2} The resolver amplitude K ₁ · E ₁ of the first resolver in which the abnormality has occurred is calculated by multiplying by the amplitude ratio r ₁₂ (S32). Subsequently, the arc cosine of the value obtained by dividing the amplitude Ac1 of the detection coil (normal detection coil) paired with the detection coil where the abnormality has occurred by the resolver amplitude K ₁ · E ₁ is calculated, and this calculated value is calculated. The first rotation angle θ ₁ is calculated by dividing by the shaft multiple angle N.
[Selection] Figure 7

Description

  The present invention relates to a torque detector that includes two resolvers and detects torque based on a rotation angle detected by each resolver.

  2. Description of the Related Art Conventionally, there is known an electric power steering device that applies a steering assist torque to a driver's steering operation. The electric power steering device detects a steering torque acting on the steering shaft by a torque detection device, calculates a target assist torque that increases as the steering torque increases, and obtains the calculated target assist torque. Feedback control of the energization amount. Therefore, in the electric power steering device, the reliability of the torque detection device is particularly required.

The torque detection device calculates a steering torque proportional to the torsion angle by detecting the torsion angle of the torsion bar provided on the steering shaft. For example, the torque detection device proposed in Patent Document 1 employs a configuration that detects the twist angle of a torsion bar using two resolvers. In this torque detection device, a first resolver is provided on one end side of the torsion bar, and a second resolver is provided on the other end side. The first rotation angle (θ ₁ ) detected by the first resolver and the second resolver The steering torque is detected from the difference from the detected second rotation angle (θ ₂ ).

  Each resolver includes an excitation coil that is supplied with an excitation AC signal and energizes the rotor coil, and a pair of detection coils (sin phase detection coil, cos phase detection coil) provided around the torsion bar. The pair of detection coils are assembled with an electrical angle shifted by 90 degrees (π / 2). The sin phase detection coil outputs an AC signal having an amplitude corresponding to the sin value of the rotation angle of the rotor, and the cos phase detection coil outputs an AC signal having an amplitude corresponding to the cos value of the rotation angle of the rotor. Therefore, the rotation angle of the rotor detected by the resolver can be calculated based on the arctangent value obtained by dividing the amplitude of the output signal of the sin phase detection coil by the amplitude of the output signal of the cos phase detection coil.

The torque detection device proposed in Patent Document 1 is disconnected when the rotation angle detected by a normal resolver is within a predetermined angle range even when one of the detection coils in one resolver is disconnected. The rotation angle is estimated using the output signal of the other detection coil that is paired with the detected coil. This is because the mechanical angle difference between the first rotation angle (θ ₁ ) detected by the first resolver and the second rotation angle (θ ₂ ) detected by the second resolver is always below a certain value. If the rotation angle detected by a normal resolver is within a predetermined angle range, the rotation angle is uniquely determined from the output signal of the other detection coil paired with the disconnected coil. It uses what can be done. As a result, the steering torque can be detected from the difference between the first rotation angle (θ ₁ ) and the second rotation angle (θ ₂ ).

JP 2003-315182 A

  However, when the rotation angle is estimated from the output signal of the detection coil on one side as described above, good detection accuracy cannot be obtained. This is because the transformation ratio of the resolver changes due to a change in the ambient temperature of the resolver. The resolver outputs an AC signal from a detection coil (sin phase detection coil, cos phase detection coil) at a predetermined transformation ratio with respect to the excitation AC signal supplied to the excitation coil. If the detection coil is not disconnected, the arc tangent of the ratio of the amplitude values of the two-phase detection signals is calculated, and the effect of such a change in the transformation ratio does not appear in the calculation result of the rotation angle. However, when one of the two phases of the detection coil is disconnected, the rotation angle is calculated based on the output signal of the detection coil on the non-disconnected side. In the case where there is a deviation from the set transformation ratio used in the calculation formula, the larger the deviation, the larger the rotation angle detection error. Along with this, the detection accuracy of the steering torque is lowered.

  The present invention has been made to cope with the above problem, and detects a rotation angle with high accuracy that is not influenced by the ambient temperature of the resolver even if one of the two phases is disconnected. The purpose is to improve the torque detection accuracy.

In order to achieve the above object, a feature of the present invention is that a first resolver (110) having a pair of detection coils for outputting a two-phase detection signal corresponding to a first rotation angle that is a rotation angle on the input side of the shaft. And a second resolver (120) having a pair of detection coils for outputting a two-phase detection signal corresponding to a second rotation angle that is a rotation angle on the output side of the shaft, Amplitude detection means (S12) for detecting the amplitude of the two-phase detection signal output from the first resolver and the amplitude of the two-phase detection signal output from the second resolver, and the detected output of the first resolver Rotation angle calculation means (S15) that calculates the first rotation angle based on the amplitude of the two-phase detection signal to be calculated and calculates the second rotation angle based on the detected two-phase detection signal output from the second resolver. ) The torque calculating means (S16) for calculating the torque acting on the shaft based on the difference between the first rotation angle and the second rotation angle, and either the first resolver or the second resolver, An abnormality detection means (S13) for detecting that an abnormality has occurred on one side, and rotation of an abnormal side resolver having a detection coil in which the abnormality is detected when an abnormality is detected on one of the detection coils In the torque detection device comprising the abnormal rotation angle estimation means (S30, S40) for estimating the angle,
The abnormal rotation angle estimation means includes an amplitude of a detection signal output from the first resolver and an amplitude of a detection signal output from the second resolver when the first resolver and the second resolver are normal. And a resolver relationship information storage means (33) for storing relationship information representing the relationship between the normal side resolver and the normal side resolver not having the detection coil in which the abnormality is detected when an abnormality is detected in one of the detection coils. The amplitude of the detection signal output from the pair of detection coils, the amplitude of the detection signal output from the detection coil in which the abnormality of the abnormal resolver is not detected, and the relationship information stored in the resolver relationship information storage means And an abnormal-side resolver rotation angle calculating means (S30, S40) for calculating the rotation angle of the abnormal-side resolver.

  In the present invention, the first resolver is provided on the input side of the shaft, and the second resolver is provided on the output side. The first resolver receives an excitation AC signal, and a two-phase detection signal corresponding to a first rotation angle that is a rotation angle on the shaft input side from a pair of detection coils (sin phase detection coil, cos phase detection coil). Is output. Similarly, the second resolver receives an excitation AC signal, and from a pair of detection coils (sin phase detection coil, cos phase detection coil), a two-phase signal corresponding to the second rotation angle that is the rotation angle on the shaft output side. A detection signal is output. The two-phase detection signal is an AC voltage signal generated by the input AC signal for excitation, and depends on the sin phase detection signal whose amplitude changes depending on the sin value of the rotation angle and the cos value of the rotation angle. And a cos phase detection signal whose amplitude changes. Therefore, in each resolver, a sin phase detection signal is output from one detection coil, and a cos phase detection signal is output from the other detection coil.

  The amplitude detector detects the amplitude of the two-phase detection signal output from each resolver. The rotation angle calculation means calculates the first rotation angle based on the amplitude of the two-phase detection signal output from the first resolver, and calculates the second rotation angle based on the two-phase detection signal output from the second resolver. To do. For example, the rotation angle can be calculated based on an arc tangent value obtained by dividing the amplitude of the sin phase detection signal by the amplitude of the cos phase detection signal. The torque calculation means calculates the torque acting on the shaft based on the difference between the first rotation angle and the second rotation angle thus calculated. That is, by detecting the twist angle of the shaft, a torque proportional to the twist angle is calculated. In this case, it is preferable to use a torsion bar as the shaft.

  When the energization circuit of the resolver detection coil is disconnected, a normal detection signal is not output from the detection coil. At this time, if there is an abnormality in only one of the pair of detection coils, the rotation angle may be estimated based on the detection signal output from the other detection coil. For example, when detecting the torque of a device in which the limit of the angle difference between the first rotation angle and the second rotation angle is set (or assumed), depending on the rotation angle of the resolver in which no abnormality has occurred, The rotation angle can be uniquely determined only from the detection signal output from the detection coil. Also, depending on the situation where the torque is working, the rotation angle may be uniquely determined only from the detection signal output from the other detection coil.

  Therefore, in the present invention, the abnormality detection means determines whether an abnormality has occurred in one of the pair of detection coils by either the first resolver or the second resolver. When it is detected that an abnormality has occurred in one of the pair of detection coils, the abnormal rotation angle estimation means estimates the rotation angle of the abnormal resolver having the detection coil in which the abnormality is detected. In this case, if the rotation angle is calculated based only on the amplitude of the detection signal of the other detection coil (normal detection coil) paired with the detection coil in which an abnormality is detected, an accurate rotation angle is calculated. Can not. This is because the transformation ratio of the resolver changes according to the ambient temperature of the resolver, so that the amplitude of the detection signal changes.

  In order to cope with such a problem, the abnormal rotation angle estimation means includes a resolver related information storage means and an abnormal side resolver rotation angle calculation means. The resolver relationship information storage means stores relationship information indicating the relationship between the amplitude of the detection signal output from the first resolver and the amplitude of the detection signal output from the 2 resolver when the first resolver and the second resolver are normal. Pre-stored. This relationship information can be stored, for example, as a ratio between the amplitude of the detection signal output from the first resolver and the amplitude of the detection signal output from the second resolver. In this case, for example, the ratio of the square root of the square sum of the amplitude of the sin phase and the amplitude of the cos phase in the first resolver and the second resolver can be applied. In addition, it is possible to apply the amplitude ratio between the sin phases and the amplitude ratio between the cos phases in the first resolver and the second resolver when the first rotation angle and the second rotation angle are the same. it can.

  When the abnormality is detected in one of the detection coils, the abnormal-side resolver rotation angle calculation means calculates the amplitude of the detection signal output from the pair of detection coils of the normal-side resolver that does not have the detection coil in which the abnormality is detected. The rotation angle of the abnormal side resolver is calculated based on the amplitude of the detection signal output from the detection coil in which no abnormality of the abnormal side resolver is detected and the relationship information stored in the resolver relationship information storage means. When the ambient temperature of the resolver unit changes, the transformation ratio in the first resolver and the transformation ratio in the second resolver change accordingly. On the other hand, since the relationship information stored in the resolver relationship information storage means is the relationship between the amplitudes of the detection signals of the two resolvers, it does not change according to the ambient temperature. For this reason, from the amplitude of the detection signal output from the pair of detection coils of the normal resolver and the related information, the amplitude that should be output from the resolver in which an abnormality has occurred, for example, the amplitude of the sin phase and the amplitude of the cos phase The square root of the sum of squares can be estimated. As a result, the abnormal-side resolver rotation angle calculation means can detect a rotation angle with high accuracy that is not affected by the ambient temperature of the resolver even when an abnormality occurs in one of the two detection coils. . Thereby, according to this invention, a torque detection precision can be improved.

  Another feature of the present invention is that the resolver-related information storage means is configured such that the resolver amplitude is defined as a square root of a sum of squares of an amplitude of a sin phase detection signal and an amplitude of a cos phase detection signal in each resolver. An amplitude ratio corresponding to the ratio between the resolver amplitude of the resolver and the resolver amplitude of the second resolver is stored as the relation information, and the abnormal-side resolver rotation angle calculation means is based on the amplitude detected by the amplitude detection means. The resolver amplitude of the normal side resolver is calculated (S31, S41), and based on the resolver amplitude of the normal side resolver and the amplitude ratio stored in the relation information storage means, the resolver amplitude of the abnormal side resolver Is provided with an abnormal-side resolver amplitude estimating means (S32, S42), and no abnormality is detected in the abnormal-side resolver. Based on the amplitude of the detection signal output from the output coil and the resolver amplitude of the abnormal resolver estimated by the abnormal resolver amplitude estimating means, the rotation angle of the abnormal resolver is calculated (S34, S35, S44). , S45).

  In the present invention, the amplitude ratio is stored as the relationship information in the resolver relationship information storage means. This amplitude ratio is the difference between the resolver amplitude of the first resolver and the resolver amplitude of the second resolver when the square root of the square sum of the amplitude of the sin phase detection signal and the amplitude of the cos phase detection signal in each resolver is defined as the resolver amplitude. It is a value corresponding to the ratio. The abnormal-side resolver rotation angle calculating means includes abnormal-side resolver amplitude estimating means for estimating the resolver amplitude in the abnormal-side resolver.

  The abnormal side resolver amplitude estimating means calculates the resolver amplitude of the normal side resolver based on the amplitude detected by the amplitude detecting means. That is, the square root of the square sum of the amplitude of the sin phase detection signal of the normal side resolver and the amplitude of the cos phase detection signal is calculated. Then, the resolver amplitude of the abnormal resolver is estimated based on the calculated resolver amplitude of the normal resolver and the amplitude ratio stored in the resolver related information storage means. When the resolver amplitude of the normal resolver is multiplied (or divided) by the amplitude ratio, the resolver amplitude of the abnormal resolver can be estimated. The resolver amplitude of the abnormal side resolver corresponds to the resolver amplitude when it is assumed that the detection coil in which the abnormality is detected normally outputs the detection signal.

  The abnormal-side resolver rotation angle calculation means is based on the amplitude of the detection signal output from the detection coil in which no abnormality of the abnormal-side resolver is detected and the resolver amplitude of the abnormal-side resolver estimated by the abnormal-side resolver amplitude estimating means. The rotation angle of the abnormal resolver is calculated using a trigonometric function. For example, if the detection coil in which an abnormality is detected is a sin phase, the rotation angle of the abnormal side resolver is based on the arc cosine value obtained by dividing the amplitude of the other cos phase detection signal by the resolver amplitude of the abnormal side resolver. Can be calculated. Similarly, if the detection coil in which an abnormality is detected is a cos phase, the rotation of the abnormal side resolver is based on the arc sine value obtained by dividing the amplitude of the other sin phase detection signal by the resolver amplitude of the abnormal side resolver. The corner can be calculated.

  As a result, according to the present invention, the rotation angle of the abnormal resolver can be appropriately calculated using the amplitude ratio, and a highly accurate torque that is not affected by the ambient temperature of the resolver can be detected.

  In the above description, in order to help the understanding of the invention, the reference numerals used in the embodiments are attached to the configuration of the invention corresponding to the embodiments in parentheses. It is not intended to be limited to the embodiment defined by.

It is a schematic block diagram of the electric power steering device provided with the torque detection apparatus as an embodiment. It is a circuit block diagram of a torque sensor unit. It is a figure showing the range in which a rotation angle is calculated | required uniquely, Comprising: (a) represents the range from which a rotation angle is uniquely determined from the detection signal of only a cos phase, (b) is rotated from the detection signal of only a sin phase. Represents a range where the corner is uniquely determined. It is a graph showing the change of the amplitude with respect to the rotation angle of a detection signal, (a) shows the amplitude change with respect to the rotation angle in preset temperature conditions, (b) shows the rotation angle when the coil temperature changes. Represents amplitude change. It is a graph showing the relationship between a resolver amplitude and the amplitude of the detection signal of each phase. It is a flowchart showing a steering torque detection routine. It is a flowchart showing a 1st rotation angle calculation routine (subroutine). It is a flowchart showing a 2nd rotation angle calculation routine (subroutine).

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electric power steering device for a vehicle including a torque detection device as an embodiment.

  The electric power steering device includes a steering mechanism 10 that steers the left and right front wheels FW1 and FW that are steered wheels by steering the steering handle 11, a power assist unit 20 that is provided in the steering mechanism 10 and generates steering assist torque, An assist control device 50 (hereinafter referred to as an assist ECU 50) for driving and controlling the electric motor 21 of the power assist unit 20 and a resolver unit 100 are provided.

  The steering mechanism 10 includes a steering shaft 12 that is connected to a steering handle 11 so as to integrally rotate at an upper end, and a pinion gear 13 is connected to a lower end of the steering shaft 12 so as to rotate integrally. The pinion gear 13 meshes with rack teeth formed on the rack bar 14 to constitute a rack and pinion mechanism. Left and right front wheels FW1, FW2 are connected to both ends of the rack bar 14 via a tie rod and a knuckle arm (not shown) so as to be steerable. The left and right front wheels FW1 and FW2 are steered to the left and right according to the axial displacement of the rack bar 14 as the steering shaft 12 rotates about the axis.

  A power assist unit 20 is assembled to the rack bar 14. The power assist unit 20 includes a steering assist electric motor 21 (for example, a three-phase DC brushless motor) and a ball screw mechanism 22. The rotating shaft of the electric motor 21 is connected to the rack bar 14 through the ball screw mechanism 22 so as to be able to transmit power, and assists the steering of the left and right front wheels FW1, FW2 by the rotation. The ball screw mechanism 22 functions as a speed reducer and a rotation-linear converter, and decelerates the rotation of the electric motor 21 and converts it into a linear motion and transmits it to the rack bar 14. The electric motor 21 is provided with a rotation angle sensor 61 for detecting the rotation angle of the rotation shaft. The rotation angle sensor 61 is connected to the assist ECU 50. Instead of assembling the electric motor 21 to the rack bar 14, the electric motor 21 is assembled to the steering shaft 12, and the rotation of the electric motor 21 is transmitted to the steering shaft 12 via the speed reducer so that the shaft 12 is axially connected. You may comprise so that it may drive around.

  The steering shaft 12 is provided with a torsion bar 12a at an intermediate position in the axial direction. In the steering shaft 12, a portion connecting the upper end of the torsion bar 12a and the steering handle 11 is called an input shaft 12in, and a portion connecting the lower end of the torsion bar 12a and the pinion gear 13 is called an output shaft 12out.

A resolver unit 100 is provided on the steering shaft 12. The resolver unit 100 includes a torsion bar 12a, a first resolver 110 assembled to the input shaft 12in, and a second resolver 120 assembled to the output shaft 12out. The first resolver 110 outputs a signal corresponding to the rotation angle of the input shaft 12in (the rotation angle at one end position of the torsion bar 12a and corresponding to the first rotation angle of the present invention), and the second resolver 120 A signal corresponding to the rotation angle of the output shaft 12out (the rotation angle at the other end position of the torsion bar 12a and corresponding to the second rotation angle of the present invention) is output. When the steering handle 11 is turned, torque acts on the steering shaft 12 and the torsion bar 12a is twisted. The torsion angle of the torsion bar 12a is proportional to the steering torque acting on the steering shaft 12. Therefore, the steering torque acting on the steering shaft 12 is detected by obtaining the difference between the first rotation angle θ ₁ detected by the first resolver 110 and the second rotation angle θ ₂ detected by the second resolver 120. Can do. The first resolver 110 and the second resolver 120 are connected to the assist ECU 50.

  The assist ECU 50 includes a calculation unit 30 including a microcomputer and a signal processing circuit, and a motor drive circuit 40 (for example, a three-phase inverter circuit) configured by a switching circuit. The calculation unit 30 includes an assist calculation unit 31, a torque calculation unit 32, and a storage unit 33. The torque calculator 32 is connected to the resolver unit 100 and detects the steering torque acting on the steering shaft 12 by calculation. In addition, the assist calculation unit 31 is connected with a warning lamp 65 for notifying the driver of the abnormality, and turns on the warning lamp 65 when disconnection is detected, which will be described later. A configuration including the resolver unit 100, the torque calculation unit 32, and the storage unit 33 corresponds to the torque detection device of the present invention. The assist calculation unit 31 calculates a control amount of the electric motor 21 based on the steering torque detected by the torque calculation unit 32 and outputs a control signal corresponding to the control amount to the motor drive circuit 40. The storage unit 33 includes a memory that stores various control programs, control data, and the like.

  The motor drive circuit 40 receives the PWM control signal from the assist calculation unit 31 and adjusts the energization amount to the electric motor 21 by controlling the duty ratio of the internal switching element. The motor drive circuit 40 is provided with a current sensor 41 that detects a current flowing through the electric motor 21.

  The assist calculation unit 31 connects a current sensor 41, a vehicle speed sensor 60, and a rotation angle sensor 61. The vehicle speed sensor 60 outputs a vehicle speed detection signal representing the vehicle speed vx. The assist calculation unit 31 inputs the calculation result of the steering torque calculated by the torque calculation unit 32.

  Next, the steering assist control performed by the assist calculation unit 31 will be briefly described. The assist calculation unit 31 acquires the vehicle speed vx detected by the vehicle speed sensor 60 and the steering torque Tr calculated by the torque calculation unit 32, and calculates the target assist torque based on the acquired vehicle speed vx and the steering torque Tr. To do. The target assist torque is set so as to increase as the steering torque Tr increases and to decrease as the vehicle speed vx increases with reference to an assist map (not shown). The assist calculation unit 31 calculates a target current required to generate the target assist torque, and calculates a PI control (proportional integral control) equation based on the deviation between the actual current detected by the current sensor 41 and the target current. The target command voltage is used to calculate, and a PWM control signal corresponding to the target command voltage is output to the motor drive circuit 40. The assist calculation unit 31 acquires the rotation angle (electrical angle) of the electric motor 21 detected by the rotation angle sensor 61, and the three-phase (U-phase, V-phase, W-phase) PWM control signal corresponding to the rotation angle. The three-phase drive voltage is applied to the electric motor 21 by generating Thus, a target current in a direction rotating in the same direction as the driver's steering direction flows through the electric motor 21 by current feedback control. As a result, the driver's steering operation is appropriately assisted by the torque generated by the electric motor 21.

  Next, the resolver unit 100 will be described. FIG. 2 shows a schematic circuit configuration of the resolver unit 100. The first resolver 110 includes an input shaft 12in as a rotor. A first excitation coil 111 wound along the circumferential direction of the rotor is fixedly provided on the stator on the outer peripheral side of the input shaft 12in. A first rotor coil 114 is fixedly provided on the input shaft 12in serving as a rotor. The first rotor coil 114 rotates as the rotor rotates. The first rotor coil 114 is electrically connected to the first excitation coil 111 in a non-contact manner via a transformer (not shown) provided in the rotor, and is energized by an AC voltage applied to the first excitation coil 111. Is done. Although not shown, a plurality of first rotor coils 114 are arranged at equiangular intervals so that the electrical angle is N times the mechanical rotation angle of the rotor in order to increase the resolution of the rotation angle. .

  The first resolver 110 includes a first sin phase detection coil 112 and a first cos phase detection coil 113 on a stator on the outer peripheral side of the input shaft 12in. The first sin phase detection coil 112 and the first cos phase detection coil 113 are arranged at positions where the electrical angles are shifted from each other by π / 2.

  The first sin phase detection coil 112 and the first cos phase detection coil 113 are arranged on the rotation plane of the first rotor coil 114 and output an alternating voltage signal by the magnetic flux generated by the first rotor coil 114. The amplitude value of the AC voltage signal generated in the first sin phase detection coil 112 and the first cos phase detection coil 113 varies depending on the rotational position of the first sin phase detection coil 112 and the first cos phase detection coil 113 with respect to the first rotor coil 114. To do. That is, the first sin phase detection coil 112 outputs an AC voltage signal having an amplitude corresponding to the sin value of the rotation angle of the input shaft 12in, and the first cos phase detection coil 113 sets the cos value of the rotation angle of the input shaft 12in. An AC voltage signal having a corresponding amplitude is output.

  One end of the first excitation coil 111 is connected to the first excitation signal output port 50pe1 of the assist ECU 50 via the first excitation line 210. Further, one end of the first sin phase detection coil 112 is connected to the first sin phase signal input port 50ps1 of the assist ECU 50 via the first sin phase detection line 212. One end of the first cos phase detection coil 113 is connected to the first cos phase signal input port 50pc1 of the assist ECU 50 via the first cos phase detection line 213. In the figure, reference numeral 100pe1 is a first excitation signal input port of the resolver unit 100, reference numeral 100ps1 is a first sin phase signal output port, and reference numeral 100pc1 is a first cos phase signal output port. Therefore, the portion that becomes the wire harness includes the first excitation line 210 between the first excitation signal output port 50pe1 and the first excitation signal input port 100pe1, the first sin phase signal output port 100ps1, and the first sin phase signal input port 50ps1. And a first cos phase detection line 212 between the first cos phase signal output port 100pc1 and the first cos phase signal input port 50pc1.

  The other end of the first excitation coil 111, the other end of the first sin phase detection coil 112, and the other end of the first cos phase detection coil 113 are connected to the ground port 50pg of the assist ECU 50 via the common ground line 240. In the figure, reference numeral 100pg denotes a ground port of the resolver unit 100. Therefore, the common ground line 240 between the ground port 50pg and the ground port 100pg is a wire harness portion.

  The second resolver 120 includes an output shaft 12out as a rotor. A second excitation coil 121 wound along the circumferential direction of the rotor is fixedly provided on the stator on the outer peripheral side of the output shaft 12out. A second rotor coil 124 is fixedly provided on the output shaft 12out serving as a rotor. The second rotor coil 124 rotates as the rotor rotates. The second rotor coil 124 is electrically connected to the second excitation coil 121 in a non-contact manner via a transformer (not shown) provided in the rotor, and is energized by an AC voltage applied to the second excitation coil 121. Is done. Although not shown, a plurality of second rotor coils 124 are arranged at equal angular intervals so that the electrical angle is N times the mechanical rotation angle of the rotor in order to increase the resolution of the rotation angle. .

  The second resolver 120 includes a second sin phase detection coil 122 and a second cos phase detection coil 123 on the outer peripheral side of the output shaft 12out. The second sin phase detection coil 122 and the second cos phase detection coil 123 are arranged at positions where the electrical angles are shifted from each other by π / 2.

  The second sin phase detection coil 122 and the second cos phase detection coil 123 are arranged on the rotation plane of the second rotor coil 124, and output an AC voltage signal by the magnetic flux generated by the second rotor coil 124. The amplitude value of the AC voltage signal generated in the second sin phase detection coil 122 and the second cos phase detection coil 123 varies depending on the rotational position of the second sin phase detection coil 122 and the second cos phase detection coil 123 with respect to the second rotor coil 124. To do. That is, the second sin phase detection coil 122 outputs an AC voltage signal having an amplitude corresponding to the sin value of the rotation angle of the output shaft 12out, and the second cos phase detection coil 123 sets the cos value of the rotation angle of the output shaft 12out. An AC voltage signal having a corresponding amplitude is output.

  One end of the second excitation coil 121 is connected to the second excitation signal output port 50pe2 of the assist ECU 50 via the second excitation line 220. Also, one end of the second sin phase detection coil 122 is connected to the second sin phase signal input port 50ps2 of the assist ECU 50 via the second sin phase detection line 222. One end of the second cos phase detection coil 123 is connected to the second cos phase signal input port 50pc2 of the assist ECU 50 via the second cos phase detection line 223. In the figure, reference numeral 100pe2 is a second excitation signal input port of the resolver unit 100, reference numeral 100ps2 is a second sin phase signal output port, and reference numeral 100pc2 is a second cos phase signal output port. Accordingly, the portion that becomes the wire harness includes the second excitation line 220 between the second excitation signal output port 50pe2 and the second excitation signal input port 100pe2, the second sin phase signal output port 100ps2, and the second sin phase signal input port 50ps2. And a second cos phase detection line 222 between the second cos phase signal output port 100pc2 and the second cos phase signal input port 50pc2.

  The other end of the second excitation coil 121, the other end of the second sin phase detection coil 122, and the other end of the second cos phase detection coil 123 are connected to the ground port 50pg of the assist ECU 50 via the common ground line 240.

The assist ECU 50 includes a coil drive circuit 52. The coil drive circuit 52 includes a first excitation coil drive circuit 521 and a second excitation coil drive circuit 522. The first excitation coil drive circuit 521 outputs an excitation AC voltage having a constant period and amplitude from the first excitation signal output port 50pe1. Hereinafter, the excitation AC voltage outputted from the first excitation signal output port 50pe1 referred to as a first excitation signal, referred to the voltage value of the first excitation signal and the first excitation voltage V _1. The first excitation voltages V _1, when the amplitude and E _1, represented by the following equation.
V ₁ = E ₁ · sin (ωt) (1)

Further, the second excitation coil drive circuit 522 applies the excitation AC voltage set to have the same frequency and the same phase as the excitation AC voltage output from the first excitation coil drive circuit 521 to the second excitation. Output from the signal output port 50pe2. Hereinafter, the excitation AC voltage outputted from the second excitation signal output port 50pe2 called the second excitation signal, referred to the voltage value of the second excitation signal and the second excitation voltage V _2. Second excitation voltage V _2, when the amplitude and E _2, is expressed by the following equation.
V ₂ = E ₂ · sin (ωt) (2)

The amplitudes E ₁ and E ₂ of the first excitation voltage V ₁ and the second excitation voltage V ₂ are set according to the characteristics of the first resolver 110 and the second resolver 120. In addition, the first excitation coil drive circuit 521 and the second excitation coil drive circuit 522 are shared, and an excitation signal is supplied to the resolver unit 100 from one excitation coil drive circuit (for example, the first excitation coil drive circuit 521). You may do it. In this case, the first excitation line 210 and the second excitation line 220 can be made one.

  When the first excitation coil 111 of the first resolver 110 is excited by the first excitation signal, an alternating voltage is generated in the first sin phase detection coil 112 and the first cos phase detection coil 113. Further, when the second excitation coil 121 of the second resolver 120 is excited by the second excitation signal, an AC voltage is generated in the second sin phase detection coil 122 and the second cos phase detection coil 123.

The AC voltage signal output from the first sin phase detection coil 112 is referred to as a first sin phase detection signal, and the voltage value is referred to as a first sin phase detection voltage Es1. The AC voltage signal output from the first cos phase detection coil 113 is referred to as a first cos phase detection signal, and the voltage value is referred to as a first cos phase detection voltage Ec1. The first sin phase detection voltage Es1 and the first cos phase detection voltage Ec1 are expressed by the following equations.
_{Es1 = K 1 · E 1 ·} sin (N · θ 1) · sin (ωt + α) ··· (3)
_{Ec1 = K 1 · E 1 ·} cos (N · θ 1) · sin (ωt + α) ··· (4)

The AC voltage signal output from the second sin phase detection coil 122 is referred to as a second sin phase detection signal, and the voltage value is referred to as a second sin phase detection voltage Es2. The AC voltage signal output from the second cos phase detection coil 123 is referred to as a second cos phase detection signal, and the voltage value thereof is referred to as a second cos phase detection voltage Ec2. The second sin phase detection voltage Es2 and the second cos phase detection voltage Ec2 are expressed by the following equations.
Es2 = K ₂ · E ₂ · sin (N · θ ₂ ) · sin (ωt + α) (5)
Ec2 = K ₂ · E ₂ · cos (N · θ ₂ ) · sin (ωt + α) (6)

Here, θ ₁ is the angle of the rotor of the first resolver 110 directly connected to the input shaft 12 in, θ ₂ is the angle of the rotor of the second resolver 120 directly connected to the output shaft 12 out, K ₁ is the transformation ratio of the first resolver 110, K ₂ is the transformation ratio of the second resolver 120, N is the shaft multiple angle of the first resolver 110 and the second resolver 120, α is the phase delay amount (input / output phase difference) with respect to the excitation signal, ω is the excitation frequency, and t is the time. To express.

  The assist ECU 50 converts the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase detection signal into the first sin phase detection line 212, the first cos phase detection line 213, and the second sin phase detection line 222, respectively. , Input via the second cos phase detection line 223. The assist ECU 50 inputs the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase detection signal to the amplifiers 51s1, 51c1, 51s2, and 51c2, and amplifies the voltage of each detection signal with respect to the ground potential. Then, the amplified voltage signal is converted into a digital value by an A / D converter (not shown), and the digital value is input to a microcomputer to perform torque calculation processing.

  The torque calculation unit 32 in the assist ECU 50 includes a circuit that amplifies the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase detection signal, converts them into digital signals, and inputs them to the microcomputer, and coil driving The circuit 52 and a functional unit that performs torque calculation processing by a microcomputer are included.

A method for calculating the steering torque will be described. First, the method of detecting the rotor angles θ ₁ and θ ₂ of the first resolver 110 and the second resolver 120 will be described. Since both are calculated by the same method, here, a method of detecting the first rotation angle θ ₁ of the first resolver 110 will be described as an example.

ここで、ｆ_i，t_iは、それぞれサンプリングされた値と時間（サンプリング周期）の離散値である。 The amplitude of the _first sin phase detection signal is represented by K ₁ · E ₁ · sin (N · θ ₁ ) from the equation (3). Further, the amplitude of the _first cos phase detection signal is expressed by K ₁ · E ₁ · cos (N · θ ₁ ) from the equation (4). Here, the amplitude of the first sin phase detection signal is assumed to be As1 (As1 = K ₁ · E ₁ · sin (N · θ ₁ )). Further, the amplitude of the first cos phase detection signal is Ac1 (Ac1 = K ₁ · E ₁ · sin (N · θ ₁ )). The torque calculation unit of the assist ECU 50 samples the voltage values of the first sin phase detection signal and the first cos phase detection signal at a cycle shorter than the cycle of the first excitation signal. For example, the voltage value of each detection signal is sampled four times at equal time intervals for one cycle of the first excitation signal. Since the sampled voltage value is a discrete value, the amplitudes As1 and Ac1 can be calculated by the following equations (7) and (8) using the least square method.

Here, f _i and t _i are discrete values of the sampled value and time (sampling period), respectively.

こうして、第１回転角θ_１は、次式（１０）により計算することができる。

Therefore, the following equation (9) can be calculated from the calculated values of these two equations.

Thus, the first rotation angle θ ₁ can be calculated by the following equation (10).

ここで、Ａs2は第２ｓｉｎ相検出信号の振幅（Ａs2＝Ｋ_２・Ｅ_２・ｓｉｎ（Ｎ・θ_２））であり、Ａc2は第２ｃｏｓ相検出信号の振幅（Ａc2＝Ｋ_２・Ｅ_２・ｃｏｓ（Ｎ・θ_２））である。 Similarly, the second rotation angle θ ₂ of the second resolver 120 can be calculated by the following equation (11).

Here, As2 is the amplitude of the _second sin phase detection signal (As2 = K ₂ · E ₂ · sin (N · θ ₂ )), and Ac2 is the amplitude of the second cos phase detection signal (Ac2 = K ₂ · E ₂ · cos (N · θ ₂ )).

When the first rotation angle θ ₁ and the second rotation angle θ ₂ are thus obtained, the steering torque Tr can be calculated by the following equation (12).
Tr = Kb · (θ ₁ −θ ₂ ) (12)
Here, Kb is a proportionality constant (spring constant) determined according to the torsional characteristics of the torsion bar 12a, and is stored in the storage unit 33 in advance.

Next, a method of detecting the rotation angle θ ₁ (θ ₂ ) when an abnormality occurs in either the sin phase or the cos phase coil in each of the resolvers 110 and 120 will be described. First, the case where an abnormality occurs in the sin phase of the first resolver 110 (when the first sin phase detection signal cannot be detected normally) will be described as an example. The abnormality of the coil is not only the abnormality of the coils 112, 113, 122, and 123 itself, but also the first sin phase detection line 212, the first cos phase detection line 213, the second sin phase detection line 222, and the second cos phase detection line 223. This means a state in which the sin phase detection signal or the cos phase detection signal is not normally input to the assist ECU 50, such as disconnection.

As described above, the first rotation angle θ ₁ is obtained by calculation using the above equation (10) from the amplitude As1 of the first sin phase detection signal and the amplitude Ac1 of the first cos phase detection signal. For this reason, when the amplitude As1 cannot be detected, it cannot be calculated as it is. However, even if you only know only the amplitude Ac1, if the following conditions are met, it is possible to calculate a first rotation angle theta ₁ from only the amplitude Ac1.

The torsion bar 12a provided on the steering shaft 12 is twisted by a steering operation, but the twisting angle has a limit, and is less than 6 ° (mechanical angle) in a normal steering operation, for example. That is, the difference between the first rotation angle θ ₁ that is the angle of the rotor of the first resolver 110 and the second rotation angle θ ₂ that is the angle of the rotor of the second resolver 120 is less than 6 °. Expressing this as the electrical angle of the resolver, when the axial multiplier angle N of the resolver is 8 (N = 8), the electrical angle θe ₁ (= N · The difference between θ ₁ ) and the electrical angle θe ₂ (= N · θ ₂ ) of the second resolver 120 is less than 48 °.
| Θe ₁ −θe ₂ | <48 ° (13)

On the other hand, the reason why the rotation angle θe ₁ is uniquely determined only from the amplitude Ac1 of the cos phase is that the rotation angle θe ₁ is in the range from 0 ° to 180 ° as in the following equations (14) and (15). Alternatively, it is a case where it is known in advance that the angle is in the range of 180 ° to 360 °.
0 ° <θe ₁ <180 ° (14)
180 <θe ₁ <360 ° (15)

Therefore, from the relationship of Expression (13), if the electrical angle θe ₂ of the second resolver 120 is in the range of the following Expressions (16) and (17), the rotation angle θe ₁ is uniquely determined only from the cos phase amplitude Ac1. Determined.
0 ° + 48 ° <θe ₂ <180 ° -48 ° (16)
180 + 48 ° <θe ₂ <360-48 ° (17)
To summarize this, when the conditions of the following expressions (18) and (19) are satisfied, the rotation angle θe ₁ can be uniquely obtained from only the amplitude Ac1.
48 ° <θe ₂ <132 ° (18)
228 ° <θe ₂ <312 ° (19)
FIG. 3A shows the range where this condition is satisfied in a solid color.

Similarly, when an abnormality occurs in the cos phase of the first resolver 110, even if only the amplitude As1 is known, the first rotation is performed only from the amplitude As1 when the following conditions are satisfied. The angle θ ₁ can be calculated.

The reason why the rotation angle θe ₁ is uniquely determined only from the amplitude As1 of the sin phase is that the rotation angle θe ₁ is in a range from −90 ° to 90 ° as in the following equations (20) and (21). Or it is a case where it is known beforehand that it is the range to 90 degrees-270 degrees.
−90 ° <θe ₁ <90 ° (20)
90 <θe ₁ <270 ° (21)

Therefore, from the relationship of Expression (13), if the electrical angle θe ₂ of the second resolver 120 is in the range of the following Expressions (22) and (23), the rotation angle θe ₁ is uniquely determined only from the amplitude As1 of the sin phase. Determined.
−90 ° + 48 ° <θe ₂ <90 ° -48 ° (22)
90 + 48 ° <θe ₂ <270-48 ° (23)
To summarize this, when the conditions of the following equations (24) and (25) are satisfied, the rotation angle θe ₁ can be uniquely obtained from only the amplitude As1.
−42 ° <θe ₂ <42 ° (24)
138 ° <θe ₂ <222 ° (25)
FIG. 3 (b) shows the range where this condition is satisfied in a solid color.

Similarly, when an abnormality occurs in either the sin phase or cos phase coil of the second resolver 120, the electrical angle θe ₁ is set in advance based on the electrical angle θe ₁ of the first resolver 110. range when entering the (rotation angle .theta.e ₂ ranges uniquely determined), it is possible to calculate the second rotation angle theta ₂ from only the amplitude As2 or amplitude Ac2.

By the way, when the coil temperature changes due to a change in ambient temperature or the like, the transformation ratio of the first resolver 110 and the second resolver 120 changes according to the coil temperature. For this reason, as can be seen from the equations (3) to (6), the output characteristics of the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase detection signal change. In this case, if both the first resolver 110 and the second resolver 120 are normal, calculating the rotation angles θ ₁ and θ ₂ using equations (10) and (11) cancels the influence due to the change in coil temperature. Therefore, accurate rotation angles θ ₁ and θ ₂ are obtained. However, when the one-side phase coil is abnormal, if the rotation angle is estimated from the amplitude of the normal phase, the coil temperature is affected, and an accurate rotation angle cannot be obtained.

For example, as a method for estimating the rotation angle from the amplitude of the coil on one side phase, in relation to the sum of the square value of the amplitude of the square value and cos phase of the amplitude of the sin phase and the constant value ^{(As1 2 + As2 2 = const} ) On the basis of this, a method is conceivable in which the amplitude of the abnormal phase is estimated from the amplitude of the normal phase and the rotation angle is calculated from the equations (10) and (11). However, in this method, as shown in FIG. 4, when the coil temperature changes from a preset condition temperature, the amplitude of the normal phase changes due to the change in the transformation ratio, and accordingly, the abnormal phase Since the estimated amplitude value changes, an incorrect rotation angle is calculated. In FIG. 4, (a) represents an amplitude change with respect to the rotation angle under a preset temperature condition, and (b) represents an amplitude change with respect to the rotation angle when the coil temperature changes. In either case, the upper stage represents the amplitude with respect to the rotation angle of the cos phase detection signal that is the normal phase, and the middle stage and the lower stage represent the two estimated values of the sin phase amplitude with respect to the rotation angle.

Therefore, in the present embodiment, an appropriate rotation angle is calculated using the following method regardless of changes in the coil temperature. Here, the ratio r ₁₂ between the amplitude of the first resolver 110 and the amplitude of the second resolver 120 can be calculated by the following equation (26).

The amplitude ratio _{r 12} has a square sum of the 1cos phase detection voltage Ec1, which is the output of the 1sin phase detection voltage Es1 and the 1cos phase detection coil 113 which is the output of the 1sin phase detection coil 112 in the first resolver 110, The square root of the ratio of the second sin phase detection voltage Es2 that is the output of the second sin phase detection coil 122 and the second sum of squares of the second cos phase detection voltage Ec2 that is the output of the second cos phase detection coil 123 in the second resolver 120 is calculated. It is what I have sought. Therefore, the amplitude ratio r ₁₂ is determined in advance by measuring the detection voltages Es1, Ec1, Es2, and Ec2 of the detection coils 112, 113, 122, and 123 of each phase when the first resolver 110 and the second resolver 120 are normal. You can ask for it. The amplitude ratio r _12, the coil temperature becomes a constant value without changing vary.

これにより、第１レゾルバ１１０の振幅に相当する値Ｋ_１’・Ｅ_１を次式（３０）により推定することができる。
Ｋ_１’・Ｅ_１＝ｒ_１２・Ｋ_２’・Ｅ_２ ・・・（３０） Consider a case where the transformation ratio of the first resolver 110 changes to K ₁ ′ and the transformation ratio of the second resolver 120 changes to K ₂ ′ due to a change in ambient temperature of the resolvers 110 and 120. In this case, the amplitudes As2 ′ and Ac2 ′ can be obtained by sampling the output voltages of the second sin phase detection signal and the second cos phase detection signal of the second resolver 120 and using the least square method described above. The amplitudes As2 ′ and Ac2 ′ are expressed by the following equations (27) and (28).
As2 ′ = K ₂ ′ · E ₂ · sin (N · θ ₂ ) (27)
Ac2 ′ = K ₂ ′ · E ₂ · cos (N · θ ₂ ) (28)
Therefore, the value K ₂ ′ · E ₂ corresponding to the amplitude of the second resolver 120 can be calculated by the following equation (29).

Thereby, the value K ₁ ′ · E ₁ corresponding to the amplitude of the first resolver 110 can be estimated by the following equation (30).
K ₁ '· E ₁ = r ₁₂ · K ₂ ' · E ₂ (30)

Hereinafter, the square root of the square sum of the amplitude As1 ′ of the first sin phase detection signal and the amplitude Ac1 ′ of the first cos phase detection signal is defined as the resolver amplitude K ₁ ′ · E ₁ of the first resolver 110, and the second sin phase detection signal The square root of the square sum of the amplitude As2 ′ and the amplitude Ac2 ′ of the second cos phase detection signal is defined as the resolver amplitude K ₂ ′ · E ₂ of the second resolver 120. The relationship between the resolver amplitude K ₁ ′ · E _{1 of} the first resolver 110, the amplitude As1 ′ of the first sin phase detection signal, and the amplitude Ac1 ′ of the first cos phase detection signal is as shown in FIG. The relationship between the resolver amplitude K ₂ ′ · E _{2 of} the second resolver 120, the amplitude As2 ′ of the second sin phase detection signal, and the amplitude Ac2 ′ of the second cos phase detection signal is as shown in FIG. is there. Therefore, the amplitude ratio r ₁₂ corresponds to the ratio between the resolver amplitude K ₁ ′ · E _{1 of} the first resolver 110 and the resolver amplitude K ₂ ′ · E _{2 of} the second resolver 120.

ここで、右辺のアークコサインの分母は、式（３０）により求められた値を用いる。 Here, a case where the sin phase of the first resolver 110 is abnormal will be described. In this case, the output voltage of the first cos phase detection coil 113 of the first resolver 110 is sampled, and the amplitude Ac1 ′ of the first cos phase detection signal is obtained using the above-described least square method. This amplitude Ac1 ′ can be expressed by the following equation (31).
Ac1 ′ = K ₁ ′ · E ₁ · cos (N · θ ₁ ) (31)
Therefore, the first rotation angle θ ₁ of the first resolver 110 can be calculated by the following equation (32).

Here, the value obtained by the equation (30) is used as the denominator of the arc cosine on the right side.

Thus, when an abnormality occurs in the one-sided coil of one resolver, an abnormality occurs in the resolver amplitude (K ₂ '· E ₂ ) of the resolver in which no abnormality has occurred and the amplitude ratio r _12. The rotation angle (θ ₁ ) of the resolver in which an abnormality has occurred can be calculated based on the amplitude (Ac1 ′) of the normal phase in the resolver that is operating. According to this operation, even the coil temperature changes, since by using the amplitude ratio r _12, corrects the resolver amplitude of the resolver abnormality has occurred, it is possible to determine the correct angle of rotation.

  Next, the steering torque detection process executed by the torque calculator 32 will be described. FIG. 6 is a flowchart showing a steering torque detection routine. The steering torque detection routine is stored in the storage unit 33 as a control program. The steering torque detection routine is repeatedly executed at a predetermined short period during a period in which the ignition key is in the on state. The torque calculator 32 operates the coil drive circuit 52 together with the start of the steering torque detection routine, and the first excitation signal and the second excitation signal from the first excitation signal output port 50pe1 and the second excitation signal output port 50pe2. Starts output.

  In step S11, the torque calculation unit 32 determines the first sin phase detection voltage Es1, the first cos phase detection voltage, which are voltage values of the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase detection signal. Ec1, the second sin phase detection voltage Es2, and the second cos phase detection voltage Ec2 are read. The torque calculator 32 is a sampling routine different from the steering torque detection routine, and samples the instantaneous values of the detected voltages Es1, Es1, Es2, and Ec2 at, for example, four sampling periods per period of the excitation signal. In step S11, the detection voltages Es1, Es1, Es2, and Ec2 sampled by the sampling routine are read. Subsequently, in step S12, the first sin phase detection signal, the first cos phase detection signal, the second sin phase detection signal, and the second cos phase are detected using the least square method based on the read detection voltages Es1, Ec1, Es2, and Ec2. The detection signal amplitudes As1, Ac1, As2, and Ac2 are calculated.

  Subsequently, in step S13, the torque calculation unit 32 checks the coil abnormality based on the detected voltages Es1, Ec1, Es2, and Ec2. The coil abnormality is caused not only by the coil abnormality in the resolver but also by disconnection of the first sin phase detection line 212, the first cos phase detection line 213, the second sin phase detection line 222, the second cos phase detection line 223, and the like. This is mainly due to disconnection of the wire harness and disconnection of the connector. When such a coil abnormality occurs, the detection voltages Es1, Ec1, Es2, and Ec2 deviate from the normal range. For example, the detection voltages Es1, Ec1, Es2, and Ec2 may be offset, or the AC voltage signal may not be detected. Step S13 identifies the presence or absence of a coil abnormality, the resolver in which the coil abnormality has occurred, and its abnormal phase, based on whether or not these detection voltages Es1, Ec1, Es2, and Ec2 are out of the normal range. To do.

In step S14, the torque calculation unit 32 determines whether or not a coil abnormality has occurred based on the coil abnormality check result. If no coil abnormality has occurred (S14: No), in step S15. The first rotation angle θ _{1 of} the first resolver 110 and the second rotation angle θ ₂ of the second resolver 120 are calculated using the above equations (10) and (11).

  Subsequently, the torque calculation unit 32 calculates the steering torque Tr using the above formula (12) in step S16, and then outputs the calculated steering torque Tr to the assist calculation unit 31 in step S17. The assist calculation unit 31 calculates a target assist torque using the steering torque Tr, and outputs a PWM control signal to the motor drive circuit 40 so that a target current corresponding to the target assist torque flows to the electric motor 21. Thereby, an appropriate steering assist torque is generated from the electric motor 21.

  When the torque calculation unit 32 performs the process of step S17, the steering torque detection routine is temporarily ended. Then, the steering torque detection routine is repeated at a predetermined short cycle. When such a process is repeated and a coil abnormality is detected in step S13, the determination in step S14 is “No”. In this case, the torque calculation unit 32 advances the process to step S18 and turns on the warning lamp 65 of the vehicle. Thereby, it can be made to recognize that abnormality has arisen with respect to a driver. The means for notifying the driver of the abnormality is not limited to the warning lamp 65, and an abnormality message may be notified using a speaker, a display screen, or the like.

  Subsequently, in Step S19, the torque calculation unit 32 determines whether or not there is one coil abnormality (one phase). If there are a plurality of coil abnormalities, the steering torque Tr cannot be detected, and therefore a torque detection impossible signal is output to the assist calculation unit 31 in step S20. Thereby, the assist calculation unit 31 stops the steering assist control.

On the other hand, if there is only one coil abnormality (S19: Yes), it is determined in step S21 whether or not the first resolver 110 is causing the coil abnormality. If it is the first resolver 110, at step S22, the second rotation angle theta ₂ of the second resolver 120 is calculated using the above equation (11). Subsequently, the torque calculation unit 32, in step S23, the first rotation angle theta ₁ of the first resolver 110 determines whether uniquely determined. As described above, this processing is performed, for example, when the coil abnormality occurs in the sin phase, the electrical angle of the second resolver 120 in which the first rotation angle θe ₁ is uniquely determined only from the amplitude Ac1 of the cos phase. Since the range of θe ₂ is known (expressions (18) and (19)), whether or not the angle θe _{2 obtained} by converting the second rotation angle θ ₂ calculated in step S22 into an electrical angle is within this range. Judgment based on. Similarly, when the coil abnormality occurs in the cos phase, the range of the electrical angle θe ₂ of the second resolver 120 in which the first rotation angle θe ₁ is uniquely determined only from the sin phase amplitude As1 is known. Therefore (Equations (24) and (25)), the determination is made based on whether or not the angle θe _{2 obtained} by converting the second rotation angle θ ₂ calculated in step S22 into an electrical angle is within this range.

Torque calculating unit 32, if conditions uniquely determined first rotation angle theta ₁ of the first resolver 110 (S23: Yes), in step S30, calculates a first rotation angle theta ₁ of the first resolver 110 . This process will be described later using the flowchart of FIG. When the first rotation angle θ _{1 of} the first resolver 110 is calculated in step S30, the steering torque Tr is calculated based on the first rotation angle θ ₁ and the second rotation angle θ ₂ calculated in step S22. (S16), the steering torque Tr is output to the assist calculator 31 (S17).

On the other hand, if the status uniquely determined first rotation angle theta ₁ of the first resolver 110 (S23: No), in step S26, the steering torque calculated by the steering torque detection routine immediately preceding (one control cycle ago) Tr (n-1) is set to the current steering torque Tr, and the steering torque Tr is output to the assist calculation unit 31 (S17).

If it is determined in step S21 that the coil abnormality has not occurred in the first resolver 110, that is, if the second resolver 120 has detected a coil abnormality, in step S24, the first resolver 110 A first rotation angle θ ₁ of 110 is calculated using the above equation (10). Subsequently, the torque calculating section 32, at step S25, the second rotation angle theta ₂ of the second resolver 110 determines whether uniquely determined. This process is similar to the process of step S23. For example, when a coil abnormality occurs in the sin phase, the electrical angle of the first resolver 110 is determined by the rotation angle θe ₂ uniquely from only the amplitude Ac2 of the cos phase. Since the range of the angle θe ₁ is known (range in which θe ₂ is replaced by θe ₁ in the equations (18) and (19)), the angle obtained by converting the first rotation angle θ ₁ calculated in step S24 into an electrical angle Judgment is made based on whether or not θe ₁ is within this range. Similarly, when the coil abnormality occurs in the cos phase, the range of the electrical angle θe ₁ of the first resolver 110 is known from which the rotation angle θe ₂ is uniquely determined only from the sin phase amplitude As2. (A range in which θe ₂ is replaced by θe ₁ in equations (24) and (25))) Whether the angle θe _{1 obtained} by converting the first rotation angle θ ₁ calculated in step S24 into an electrical angle is within this range. Judgment is based on whether or not.

Torque calculating unit 32, if a situation where the second rotation angle of the second resolver 120 theta ₂ is uniquely determined (S25: Yes), in step S40, calculates a second rotation angle theta ₂ of the second resolver 110 . This process will be described later using the flowchart of FIG. When the second rotation angle θ _{2 of} the second resolver 120 is calculated in step S40, the steering torque Tr is calculated based on the second rotation angle θ ₂ and the first rotation angle θ ₁ calculated in step S24. (S16), the steering torque Tr is output to the assist calculator 31 (S17).

Next, the calculation process of the first rotation angle θ ₁ of the first resolver 110 in step S30 will be described. FIG. 7 is a flowchart showing a first rotation angle calculation routine (subroutine) incorporated as step S30 in the steering torque detection routine.

この第２レゾルバ１２０のレゾルバ振幅Ｋ_２・Ｅ_２は、レゾルバユニット１００の周囲の温度により変化するコイル温度に応じた値となる。 When the first rotation angle calculation routine is activated, the torque calculator 32 first calculates the resolver amplitude K ₂ · E ₂ of the second resolver 120 by the following equation (33) in step S31. The resolver amplitude K ₂ · E ₂ is calculated as the square root of the square sum of the amplitudes of the sin phase and the cos phase of the second resolver 120. K ₂ shown here is an actual transformation ratio of the second resolver 120 and corresponds to K ₂ ′ described above.

The resolver amplitude K ₂ · E ₂ of the second resolver 120 is a value corresponding to the coil temperature that varies depending on the ambient temperature of the resolver unit 100.

Subsequently, in step S32, the resolver amplitude K ₁ · E ₁ of the first resolver 110 is calculated by the following equation (34). The resolver amplitude K ₁ · E ₁ of the first resolver 110 is obtained by multiplying the resolver amplitude K ₂ · E ₂ of the second resolver 120 by the amplitude ratio r ₁₂ . The amplitude ratio r ₁₂ has been calculated by the equation (26), it is previously stored in the storage unit 33. Also, K ₁ shown here is an actual transformation ratio of the first resolver 110, corresponding to K _{1 'described} above.
K ₁ · E ₁ = r ₁₂ · K ₂ · E ₂ (34)
The resolver amplitude K ₁ · E ₁ of the first resolver 110 is a value estimated to be detected when the first resolver 110 is normal. In this case, since the resolver amplitude K ₂ · E _{2 of} the second resolver 120 is in accordance with the coil temperature, the resolver amplitude K ₁ · E _{1 of} the first resolver 110 is also a value in accordance with the coil temperature. .

Subsequently, in Step S33, the torque calculation unit 32 determines whether or not the coil abnormality has occurred in the sin phase. If the coil abnormality has occurred in the sin phase (S33: Yes), The first rotation angle θ ₁ of the first resolver 110 is calculated by the following equation (35) using the amplitude Ac1 of the 1 cos phase detection signal and the resolver amplitude K ₁ · E ₁ of the first resolver 110.

Further, if the coil abnormality has occurred in the cos phase (S33: No), the amplitude As1 of the 1sin phase detection signal by using a resolver amplitude _K 1 · _{E 1} of the first resolver 110, the following equation ( 36), the first rotation angle θ ₁ of the first resolver 110 is calculated.

After calculating the first rotation angle θ ₁ of the first resolver 110 in this manner, the torque calculation unit 32 proceeds to step S16 of the steering torque detection routine that is the main routine. In the above equation, there are two solutions for the first rotation angle θ ₁ , but the solution with which the difference from the second rotation angle θ ₂ is less than the maximum angle difference of 6 ° should be adopted. That's fine.

The following describes the second rotation angle theta ₂ of the calculation process of the second resolver 110 in step S40. FIG. 8 is a flowchart showing a second rotation angle calculation routine (subroutine) incorporated as step S40 in the steering torque detection routine.

この第１レゾルバ１１０の振幅Ｋ_１・Ｅ_１は、レゾルバユニット１００の周囲の温度により変化するコイル温度に応じた値となる。 When the second rotation angle calculation routine is activated, the torque calculator 32 first calculates the resolver amplitude K ₁ · E ₁ of the first resolver 110 by the following equation (37) in step S41. The resolver amplitude K ₁ · E ₁ is calculated by the square root of the sum of squares of the amplitudes of the sin phase and the cos phase of the first resolver 110.

The amplitude K ₁ · E ₁ of the first resolver 110 is a value corresponding to the coil temperature that varies depending on the ambient temperature of the resolver unit 100.

Subsequently, in step S42, the resolver amplitude K ₂ · E ₂ of the second resolver 110 is calculated by the following equation (38). The resolver amplitude K ₂ · E ₂ of the second resolver 120 is obtained by multiplying the resolver amplitude K ₁ · E ₁ of the first resolver 120 by the reciprocal of the amplitude ratio r ₁₂ .
K ₂ · E ₂ = (1 / r ₁₂ ) · K ₁ · E ₁ (38)
The resolver amplitude K ₂ · E ₂ of the second resolver 110 is a value estimated to be detected when the second resolver 120 is normal. In this case, since the resolver amplitude K ₁ · E _{1 of} the first resolver 110 is in accordance with the coil temperature, the resolver amplitude K ₂ · E _{2 of} the second resolver 120 is also a value in accordance with the coil temperature. .

Subsequently, in step S43, the torque calculation unit 32 determines whether or not the coil abnormality has occurred in the sin phase. If the coil abnormality has occurred in the sin phase (S43: Yes), The second rotation angle θ ₂ of the second resolver 120 is calculated by the following equation (39) using the amplitude Ac2 of the 2 cos phase detection signal and the resolver amplitude K ₂ · E ₂ of the second resolver 120.

Further, when the coil abnormality occurs in the cos phase (S43: No), the following equation ( ₂ ) is used by using the amplitude As2 of the second sin phase detection signal and the resolver amplitude K ₂ · E _{2 of} the second resolver 120. 40), the second rotation angle θ ₂ of the second resolver 120 is calculated.

After calculating the second rotation angle θ ₂ of the second resolver 120 in this way, the torque calculator 32 proceeds to step S16 of the steering torque detection routine that is the main routine. In the above equation, there are _two solutions for the second rotation angle θ ₂ , but the solution with which the difference from the first rotation angle θ ₁ is less than the maximum angle difference of 6 ° is adopted. That's fine.

In the torque detection device of the present embodiment described above, even when a coil abnormality occurs in one of the two resolvers 110 and 120, when the electrical angle of the normal resolver falls within a predetermined range, The rotation angle can also be calculated in the abnormal side resolver. In this calculation, the resolver amplitude (K ₂ · E ₂ , K ₂ · E ₂ ) of the abnormal resolver is calculated from the amplitude ratio r ₁₂ of the two resolvers and the actual resolver amplitude (K ₁ · E ₁ or K ₂ · E ₂ ) of the normal resolver. Alternatively, K ₁ · E ₁ ) is estimated by calculation. This estimated resolver amplitude represents the resolver amplitude when the abnormal-side resolver is normal. Then, the estimated resolver amplitude (K ₂ · E ₂ or K ₁ · E ₁ ) of the abnormal side resolver and the actual amplitude (As2 or Ac2 or As1 or Ac1) of the normal phase of the abnormal side resolver Based on this, the rotation angle is calculated (see FIG. 5).

Therefore, even if the transformation ratios K ₁ and K ₂ change due to the influence of the ambient temperature of the resolver unit 100, the influence does not appear in the calculation result of the rotation angle. For this reason, the calculation accuracy of the rotation angle of the abnormal side resolver increases. Thereby, the detection accuracy of the steering torque Tr is improved, and the reliability of the electric power steering apparatus is improved.

  In addition, if the electrical angle of the normal resolver does not fall within the specified range and the rotational angle of the abnormal resolver cannot be determined uniquely, it is calculated in the steering torque detection routine of the previous time (one control cycle before). Since the steering assist is continued using the steering torque Tr (n-1), the steering assist is not interrupted and the operability is improved. When a coil abnormality occurs, the warning lamp 65 is lit, so that the driver can be made aware of the abnormality while continuing the steering assist. Thereby, since repair is performed at an early stage, the probability of falling into a situation where the steering assist is stopped due to a double failure can be extremely reduced.

  Although the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present invention.

For example, in the present embodiment, the rotation angle of the abnormal resolver is estimated when the condition that the rotation angle can be uniquely detected even when an abnormality occurs in one of the detection coils. The condition is set by the rotation angle of the normal resolver determined on the assumption that the difference between the first rotation angle θ ₁ and the second rotation angle θ ₂ is within a predetermined angle. There is no need. For example, a condition that the rotation angle can be uniquely detected may be set on the assumption that the steering speed is equal to or lower than a predetermined speed.

DESCRIPTION OF SYMBOLS 12 ... Steering shaft, 12in ... Input shaft, 12out ... Output shaft, 12a ... Torsion bar, 20 ... Power assist part, 21 ... Electric motor, 31 ... Assist calculating part, 32 ... Torque calculating part, 33 ... Memory | storage part, 40 ... Motor drive circuit, 50 ... Assist ECU, 51s1, 51c1, 51s2, 51c2 ... Amplifier, 52 ... Coil drive circuit, 100 ... Resolver unit, 110 ... First resolver, 111 ... First excitation coil, 112 ... First sin phase detection coil 113 ... 1st cos phase detection coil, 114 ... 1st rotor coil, 120 ... 2nd resolver, 121 ... 2nd excitation coil, 122 ... 2nd sin phase detection coil, 123 ... 2nd cos phase detection coil, 124 ... 2nd rotor Coil, 212 ... first sin phase detection line, 213 ... first cos phase detection line, 222 ... The 2sin phase detection line, 223 ... first 2cos phase detection line, As1, Ac1, As2, Ac2 ... amplitude, EsI, Ec1, Es2, Ec2 ... detection voltage, _{K 1,} K 2 _... transformation _ratio, K 1 · _E 1, K ₂ · E ₂ ... resolver amplitude, N ... axis multiple angle, r ₁₂ ... amplitude ratio, Tr ... steering torque, θ ₁ ... first rotation angle, θ ₂ ... second rotation angle.

Claims (2)

A first resolver having a pair of detection coils for outputting a two-phase detection signal corresponding to a first rotation angle that is a rotation angle on the input side of the shaft, and a second rotation angle that is a rotation angle on the output side of the shaft. A resolver unit comprising a second resolver having a pair of detection coils for outputting a corresponding two-phase detection signal;
Amplitude detecting means for detecting the amplitude of the two-phase detection signal output from the first resolver and the amplitude of the two-phase detection signal output from the second resolver;
A first rotation angle is calculated based on the detected amplitude of the two-phase detection signal output from the first resolver, and a second rotation is performed based on the detected two-phase detection signal output from the second resolver. Rotation angle calculating means for calculating the angle;
Torque calculating means for calculating a torque acting on the shaft based on a difference between the calculated first rotation angle and second rotation angle;
An abnormality detection means for detecting that an abnormality has occurred in one of the pair of detection coils in either the first resolver or the second resolver;
In a torque detection apparatus comprising: an abnormal rotation angle estimation means that estimates a rotation angle of an abnormal resolver having a detection coil in which the abnormality is detected when an abnormality is detected in one of the detection coils,
The abnormal rotation angle estimation means includes
Relationship information representing the relationship between the amplitude of the detection signal output from the first resolver and the amplitude of the detection signal output from the second resolver when the first resolver and the second resolver are normal is stored in advance. Resolver-related information storage means,
When an abnormality is detected in one of the detection coils, the amplitude of a detection signal output from a pair of detection coils of a normal-side resolver that does not have the detection coil in which the abnormality is detected, and the abnormality-side resolver An abnormal-side resolver rotation angle that calculates the rotation angle of the abnormal-side resolver based on the amplitude of the detection signal output from the detection coil in which no abnormality is detected and the relationship information stored in the resolver-related information storage means A torque detection apparatus comprising: an arithmetic means. The resolver related information storage means defines the resolver amplitude of the first resolver and the second resolution when the square root of the square sum of the amplitude of the sin phase detection signal and the amplitude of the cos phase detection signal in each resolver is defined as the resolver amplitude. An amplitude ratio corresponding to the ratio of the resolver to the resolver amplitude is stored as the relation information.
The abnormal-side resolver rotation angle calculation means is
While calculating the resolver amplitude of the normal side resolver based on the amplitude detected by the amplitude detection unit, based on the resolver amplitude of the normal side resolver and the amplitude ratio stored in the relationship information storage unit, Comprising an abnormal side resolver amplitude estimating means for estimating a resolver amplitude of the abnormal side resolver,
Based on the amplitude of the detection signal output by the detection coil in which no abnormality of the abnormal side resolver is detected, and the resolver amplitude of the abnormal side resolver estimated by the abnormal side resolver amplitude estimating means, the abnormal side resolver The torque detection device according to claim 1, wherein the rotation angle is calculated.

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