JP2010162954A - Electric power steering device - Google Patents

Abstract

To provide an electric power steering device capable of continuously and stably performing a steering operation even when a torque sensor is abnormal.
A current command value calculator 45 includes a converted steering angle calculator 51 for calculating a converted steering angle θcnv obtained by converting a rotation angle θm of a motor 21 into a steering angle θs of a steering, and the converted steering angle θcnv and steering. And a steering angle control unit 52 that executes position control calculation based on the angle θs. When abnormality of the torque sensor is detected, the current command value calculation unit 45 switches the control signal based on the current command value Iq * from the basic assist control amount Ias * to the steering angle control amount Ipo *. The rudder angle control unit 52 is provided with an offset calculation unit 56. And the offset calculating part 56 performs the correction | amendment which reduces the absolute value about steering angle (theta) s used as the foundation of the target steering angle calculation.
[Selection] Figure 2

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, power steering apparatuses for vehicles include an electric power steering apparatus (EPS) using a motor as a drive source. Normally, in such EPS, a steering torque input to the steering system is detected by a torque sensor, and an assist force target value to be applied to the steering system is calculated based on the steering torque. The operation of the motor is controlled by supplying drive power to the motor so as to generate a motor torque corresponding to the assist force target value.

  However, in such a configuration, when an abnormality occurs in the torque sensor, the power assist control based on the steering torque cannot be executed. Therefore, conventionally, a method for calculating the alternative assist force target value based on the steering angle detected by the steering sensor has been proposed.

  For example, Patent Document 1 discloses a method of giving hysteresis characteristics to the calculation of the assist force target value based on the determination result of the steering angle and steering direction. Patent Document 2 discloses a method for calculating the assist force target value by multiplying the steering speed by a coefficient corresponding to the steering angle. As a result, the assist force can be suitably applied even when the torque sensor is abnormal.

JP 2004-338562 A JP 2004-114755 A

  However, all of these conventional methods are positioned to calculate a target value that substitutes for the assist force target value based on the steering torque, and in a situation where the torque sensor that is the key to the feedback loop is lacking, the stability is stable. Questions remain about the possibility of continuous control. In other words, there is a problem that the actual torque cannot be detected by the torque sensor, which makes it more susceptible to disturbances such as changes in road surface conditions. In this respect, there is still room for improvement. It was.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an electric power steering device capable of continuously performing a stable steering operation even when a torque sensor is abnormal. There is.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a steering force assisting device that applies an assisting force for assisting a steering operation to a steering system using a motor as a driving source, and a driving power for the motor. Control means for controlling the operation of the steering force assisting device through supply; a torque sensor for detecting a steering torque input to the steering system; and an abnormality detecting means for detecting an abnormality of the torque sensor, the control means Corresponds to the assist force target value when an abnormality of the torque sensor is detected and the drive power is supplied to generate a motor torque corresponding to the assist force target value based on the steering torque. In the electric power steering apparatus for stopping the supply of the driving power for generating the motor torque to be A steering angle sensor that detects a rotation angle; and a rotation angle sensor that detects a rotation angle of the motor, and the control means detects a target steering angle based on the steering angle when an abnormality of the torque sensor is detected. And calculating a converted rudder angle obtained by converting the rotation angle of the motor into a steering angle of the steering, supplying the drive power to cause the converted rudder angle to follow the target rudder angle, and the target rudder The gist is to execute correction for reducing the absolute value of the steering angle, which is the basis for calculating the angle.

  According to the above configuration, even when the steering torque cannot be detected due to the abnormality of the torque sensor, the steering system can be motor-driven according to the steering operation. In addition, by forming a feedback loop for the steering angle of the steering, it is less susceptible to disturbances such as changes in road surface conditions. As a result, a stable steering operation can be performed continuously even when the torque sensor is abnormal.

  However, when the position control is executed, all the steering return force based on the self-aligning torque (SAT) is canceled out. And since the feeling of responsiveness at the time of steering operation disappears by this, it becomes impossible to switch back in the same sense as normal time using the return force, and the driver `` reduced steering rigidity feeling '' Or there is a problem that the steering feeling is lowered by recognizing it as “a feeling of flow at the end of cutting”.

  In this regard, as described above, the steering angle that is the basis of the target rudder angle calculation is corrected to reduce its absolute value, so that the target rudder angle in the position control is more in the steering neutral direction than the actual steering angle. Along with this, a force that rotates the steering in a neutral direction acts on the steering. That is, it is possible to reproduce the steering return force that the driver feels "responsive". As a result, it is possible to switch back in the same way as in normal times, and it is possible to avoid the deterioration of steering rigidity and the flow feeling at the end of cutting as described above. A good steering feeling can be maintained even in the continuous control when the sensor is abnormal.

The invention according to claim 2 is characterized in that the control means increases the amount of correction of the steering angle as the absolute value of the steering angle before correction detected by the steering angle sensor increases. .
According to the above configuration, the larger the cutting amount of the steering 2 is, the greater the return force is applied to the steering system. As a result, it is possible to set such that the feeling of response increases in accordance with the cut amount, and as a result, it is possible to realize a more suitable steering feeling.

The gist of the invention described in claim 3 is that vehicle speed detecting means for detecting the vehicle speed is provided, and the control means makes the correction amount of the steering angle smaller as the detected vehicle speed is higher.
That is, usually, when driving at high speed, the feeling of response during steering operation is reduced. Therefore, according to the above configuration, a more natural feeling of response can be reproduced.

The gist of the invention described in claim 4 is that the control means increases the correction amount of the steering angle as the detected steering speed increases.
The invention according to claim 5 includes acceleration detecting means for detecting lateral acceleration, wherein the control means increases the correction amount of the steering angle as the detected lateral acceleration is larger. And

  That is, it is desirable to set the feeling of response at the time of steering operation so that it becomes stronger as the steering speed is higher or the lateral acceleration (centrifugal force generated when the vehicle turns) is higher. Therefore, according to the above configuration, a more suitable steering feeling can be realized.

  According to the present invention, it is possible to provide an electric power steering device capable of continuously performing a stable steering operation even when the torque sensor is abnormal.

The schematic block diagram of the electric power steering apparatus (EPS) in this embodiment. The control block diagram of EPS in this embodiment. The flowchart which shows the process sequence of the offset calculation of the steering angle used as the foundation of target steering angle calculation. Explanatory drawing which shows the relationship between the steering angle before correction | amendment, and the correction value in offset calculation. Explanatory drawing which shows the relationship between a steering angle and a target rudder angle. The flowchart which shows the aspect of the offset calculation of another example. Explanatory drawing which shows the aspect of the offset calculation of another example. Explanatory drawing which shows the aspect of the offset calculation of another example. Explanatory drawing which shows the aspect of the offset calculation of another example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the electric power steering apparatus (EPS) 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4, and the steering The rotation of the steering shaft 3 accompanying the operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. That is, the traveling direction of the vehicle is changed.

  The EPS 1 is an EPS actuator 22 serving as a steering force assisting device that applies an assist force for assisting a steering operation to the steering system using the motor 21 as a drive source, and a control unit that controls the operation of the EPS actuator 22. ECU23.

  The EPS actuator 22 of the present embodiment is a so-called column type EPS actuator, and a motor 21 as a driving source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 24. The rotation of the motor 21 is decelerated by the speed reduction mechanism 24 and transmitted to the column shaft 8 so that the motor torque is applied as an assist force to the steering system.

  On the other hand, a vehicle speed sensor 27, a torque sensor 28, and a steering sensor (steering angle sensor) 29 are connected to the ECU 23. The ECU 23 is based on the output signals of these sensors, and the vehicle speed V, the steering torque τ, and the steering. The angle θs is detected. The torque sensor 28 of the present embodiment is a so-called twin resolver type torque sensor, and the ECU 23 controls the steering torque τ based on output signals Sa and Sb of a pair of resolvers provided at both ends of a torsion bar (not shown). Is calculated. Then, the ECU 23 calculates a target assist force based on each detected state quantity, and supplies the drive power to the motor 21 that is the drive source in order to cause the EPS actuator 22 to generate the target assist force. The operation of the EPS actuator 22, that is, the assist force applied to the steering system is controlled.

Next, an aspect of assist control in the EPS of the present embodiment will be described.
As shown in FIG. 2, the ECU 23 includes a microcomputer 41 that outputs a motor control signal, and a drive circuit 42 that supplies drive power to the motor 21 that is a drive source of the EPS actuator 22 based on the motor control signal. Configured.

  In the present embodiment, the ECU 23 includes a current sensor 43 for detecting the actual current value I supplied to the motor 21 and a rotation angle sensor 44 (see FIG. 1) for detecting the rotation angle θm of the motor 21. It is connected. The microcomputer 41 outputs to the drive circuit 42 based on each vehicle state quantity and the actual current value I and the rotation angle θm of the motor 21 detected based on the output signals of the current sensor 43 and the rotation angle sensor 44. A motor control signal is generated.

  Each control block shown below is realized by a computer program executed by the microcomputer 41. Then, the microcomputer 41 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks at every predetermined period.

  More specifically, the microcomputer 41 calculates a current command value calculation unit 45 that calculates a current command value Iq *, which is a target value for power supply to the motor 21, and a current command value Iq * calculated by the current command value calculation unit 45. And a motor control signal output unit 46 for outputting a motor control signal based on the motor control signal.

  The current command value calculation unit 45 is provided with a basic assist control unit 47 that calculates a basic assist control amount Ias * as a basic component of the assist force target value. In this embodiment, the basic assist control unit 47 is provided. Is input with a vehicle speed V and a steering torque τ.

  In this embodiment, the output signals Sa and Sb of the torque sensor 28 are input to a steering torque detector 49 provided in the microcomputer 41, and the basic assist controller 47 receives the same steering signal. The torque detector 49 receives a steering torque τ detected based on the output signals Sa and Sb. The basic assist control unit 47 is configured to calculate a basic assist control amount Ias * indicating that a larger assist force should be applied as the absolute value of the steering torque τ is larger and the vehicle speed V is smaller. Yes.

  In the present embodiment, the steering torque detector 49 is provided with a function as an abnormality detecting means for detecting an abnormality of the torque sensor 28 based on the output signals Sa and Sb of the torque sensor 28. The current command value calculator 45 determines a value based on the basic assist control amount Ias * when the abnormality detection function determines that the current state is the normal state, that is, when the torque sensor 28 is operating normally. The current command value Iq * is output to the motor control signal output unit 46.

  The motor control signal output unit 46 includes the current command value Iq * output from the current command value calculation unit 45, the actual current value I detected by the current sensor 43, and the motor 21 detected by the rotation angle sensor 44. The rotation angle θm is input. The motor control signal output unit 46 calculates a motor control signal by executing feedback control so that the actual current value I follows the current command value Iq *.

  Specifically, in the present embodiment, a brushless motor that rotates by supplying three-phase (U, V, W) driving power is used as the motor 21. Then, the motor control signal output unit 46 converts the phase current values (Iu, Iv, Iw) of the motor 21 detected as the actual current value I into d, q axis current values in the d / q coordinate system (d / q The current feedback control is performed by performing conversion.

  That is, the current command value Iq * is input to the motor control signal output unit 46 as a q-axis current command value, and the motor control signal output unit 46 determines the phase current value based on the rotation angle θm detected by the rotation angle sensor 44. (Iu, Iv, Iw) is d / q converted. Further, the motor control signal output unit 46 calculates the d and q axis voltage command values based on the d and q axis current values and the q axis current command value. Then, the phase voltage command values (Vu *, Vv *, Vw *) are calculated by performing d / q inverse conversion on the d and q axis voltage command values, and a motor control signal is generated based on the phase voltage command values. To do.

  The motor control signal generated in this way is output from the microcomputer 41 to the drive circuit 42, and the drive circuit 42 supplies three-phase drive power based on the motor control signal to the motor 21. When the motor torque corresponding to the current command value Iq * as the assist force target value based on the steering torque τ is generated, the assist force corresponding to the assist force target value is applied to the steering system. ing.

(Continuous control when torque sensor is abnormal)
Next, the continuation control when the torque sensor is abnormal in the present embodiment will be described.
As shown in FIG. 2, in addition to the basic assist control unit 47, the current command value calculation unit 45 of the present embodiment converts the rotation angle θm of the motor 21 into the steering angle of the steering 2, that is, the steering angle θs. A converted rudder angle calculator 51 that calculates the converted rudder angle θcnv and a rudder angle controller 52 that executes position control calculation based on the converted rudder angle θcnv and the steering angle θs are provided.

  Specifically, the converted steering angle calculation unit 51 changes the rotation angle θm of the motor 21 to the steering angle θs based on the reduction ratio of the reduction mechanism 24 that drives and connects the motor 21 and the steering shaft 3 (column shaft 8). The converted steering angle θcnv, which is a value when converted, is calculated. When the converted rudder angle is calculated in the converted rudder angle calculation unit 51, the twisting of the torsion bar constituting the torque sensor 28 is taken into consideration, and when the ignition is turned on, the steering sensor 29 and the rotation angle sensor 44 are aligned at the midpoint. Done. The current command value calculation unit 45 calculates a target steering angle θs * based on the steering angle θs detected by the steering sensor 29, and feeds back the converted steering angle θcnv to follow the target steering angle θs *. Execute control. Then, a steering angle control amount Ipo * is calculated as a basic component for performing position control based on the steering angle θs and the converted steering angle θcnv.

  Here, the current command value calculation unit 45 of the present embodiment is calculated by the basic assist control unit 47 when the abnormality of the torque sensor 28 is detected by the steering torque detection unit 49 as the abnormality detection means. The calculation of the current command value Iq * using the basic assist control amount Ias * as a basic component is stopped. The basic component of the current command value calculation is switched to the steering angle control amount Ipo * calculated by the steering angle control unit 52, and the current command value Iq * is calculated.

  More specifically, the current command value calculation unit 45 of the present embodiment is provided with a switching control unit 53, and the basic assist control amount Ias * calculated by the basic assist control unit 47 and the steering angle control unit. The steering angle control amount Ipo * calculated by 52 is input to the switching control unit 53. The switching control unit 53 is supplied with an abnormality detection signal Str output from the steering torque detection unit 49 as the abnormality detecting means, and the switching control unit 53 detects the input abnormality. When the signal Str indicates an abnormality of the torque sensor 28, the control signal to be output is switched from the basic assist control amount Ias * to the steering angle control amount Ipo *. Then, the current command value calculation unit 45 calculates a current command value Iq * as a target value for current control in the motor control signal output unit 46 based on the control signal output from the switching control unit 53.

  That is, when the torque sensor 28 is abnormal, the ECU 23 of the present embodiment stops power supply for generating a motor torque corresponding to the assist force target value in the normal state. And the supply form of the drive electric power with respect to the motor 21 is switched to the electric power supply for performing the position control for making rotation of the motor 21 follow rotation of the steering 2 accompanying steering operation.

  With such a configuration, even when the steering torque τ cannot be detected due to an abnormality of the torque sensor 28, the steering system can be motor-driven according to the steering operation. In addition, by forming a feedback loop for the steering angle θs of the steering 2, it is less susceptible to disturbances such as changes in road surface conditions. In this embodiment, the driver can continuously perform a stable steering operation even when the torque sensor 28 is abnormal.

  More specifically, the rudder angle controller 52 of the present embodiment includes a target rudder angle calculator 54 that calculates a target rudder angle θs * as its control target value, and a target rudder angle θs * and the converted rudder angle θcnv. In addition to the F / B control unit 55 that executes the feedback control calculation based on it, an offset calculation unit 56 that performs correction (offset) of the steering angle θs that is the basis of the target steering angle calculation is provided. Specifically, the offset calculation unit 56 executes correction for reducing the absolute value of the steering angle θs detected based on the output signal of the steering sensor (steering angle sensor) 29. The target rudder angle calculation unit 54 is configured to calculate the target rudder angle θs * based on the corrected steering angle θs ′.

  In other words, a self-aligning torque (SAT) that causes the steered wheels 12 to go straight, that is, returns the steering wheel 2 to the neutral position (θs = 0), acts on the vehicle that is traveling. Therefore, under normal circumstances, the steering operation by the driver is performed while feeling the return force of the steering wheel 2 based on the SAT as “response at the time of steering operation”, although there is a reduction by the power assist control.

  However, when the position control as described above is executed, all of the return force of the steering 2 is canceled out. As a result, it becomes impossible to switch back with the same feeling as normal using the return force, and the driver recognizes this loss of responsiveness as `` decrease in steering rigidity '' during steering, Alternatively, there is a problem that the steering feeling is greatly reduced by recognizing it as a so-called “feeling of flow at the end of turning” at the end of the steering operation.

  In view of this point, in the present embodiment, as described above, prior to the calculation of the target rudder angle θs *, correction is performed to reduce the absolute value of the steering angle θs that is the basis of the target rudder angle calculation. . That is, the corrected steering angle θs ′ is offset in the steering neutral direction from the actual steering angle θs. Then, by calculating the target steering angle θs * based on the corrected steering angle θs ′, it is configured to cope with “disappearance of responsiveness” at the time of position control as described above.

  That is, by correcting the steering angle θs that is the basis of the target steering angle calculation so that the target steering angle θs * in the position control is in a steering neutral direction rather than the actual steering angle θs, the steering 2 has the same A force for rotating the steering 2 in the neutral direction is applied. That is, the return force of the steering wheel 2 that the driver feels “responsive” can be reproduced. In the present embodiment, this makes it possible to perform switching back with the same feeling as normal, and avoids the deterioration of steering rigidity and the flow feeling at the end of cutting as described above. It is possible to ensure a good steering feeling.

  More specifically, as shown in FIG. 3, when the actual steering angle θs based on the output signal of the steering sensor (steering angle sensor) 29 is input, the offset calculation unit 56 of the present embodiment first performs this steering operation. A correction value α is calculated based on the angle θs (step 101).

  Specifically, as shown in FIG. 4, when the input steering angle θs is a positive value (θs> 0), the larger the absolute value, the larger the absolute value in the positive direction. When the input steering angle θs is a negative value (θs <0), the larger the absolute value, the larger the correction value α having a larger absolute value in the negative direction. To do. In the present embodiment, the offset value is calculated by subtracting the correction value α calculated in step 101 from the actual steering angle θs (step 102).

  That is, the offset calculation unit 56 of the present embodiment is configured such that the correction amount increases as the absolute value of the input actual steering angle θs increases, that is, the corrected steering angle θs ′ is An offset calculation is performed so that the value becomes larger (small absolute value) indicating the steering neutral side. Then, the offset calculation unit 56 of the present embodiment outputs the corrected steering angle θs ′ to the target steering angle calculation unit 54 (step 103), and the target steering angle calculation unit 54 receives the input steering angle. The target steering angle θs * having a value substantially proportional to θs ′ is calculated (see FIG. 5).

  As shown in FIG. 2, the target rudder angle θs * output from the target rudder angle calculation unit 54 is input to the subtractor 57 together with the converted rudder angle θcnv output from the conversion rudder angle calculation unit 51. The F / B control unit 55 executes the feedback control calculation by multiplying the deviation Δθs between the target steering angle θs * calculated by the subtractor 57 and the converted steering angle θcnv by a predetermined gain. The steering angle control unit 52 is configured to output a value based on the result of the feedback control calculation in the F / B control unit 55 as the steering angle control amount Ipo * which is a basic component for performing the position control. ing.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The current command value calculation unit 45 includes a converted steering angle calculation unit 51 that calculates a converted steering angle θcnv obtained by converting the rotation angle θm of the motor 21 into the steering angle θs of the steering 2, and the converted steering angle θcnv and the steering And a steering angle control unit 52 that executes position control calculation based on the angle θs. When abnormality of the torque sensor 28 is detected, the current command value calculation unit 45 switches the control signal based on the current command value Iq * from the basic assist control amount Ias * to the steering angle control amount Ipo *. The rudder angle control unit 52 is provided with an offset calculation unit 56. And the offset calculating part 56 performs the correction | amendment which reduces the absolute value about steering angle (theta) s used as the foundation of the target steering angle calculation.

  In other words, when the position control is executed, the return force of the steering 2 based on the self-aligning torque (SAT) is canceled out, so that the feeling of responsiveness during the steering operation is lost. As a result, it will not be possible to switch back in the same way as during normal times using the return force, and the driver will recognize this as `` decrease in steering rigidity '' or `` flow feeling at the end of cutting '' Therefore, there is a problem that the steering feeling is lowered.

  However, as described above, the steering angle θs, which is the basis of the target rudder angle calculation, is corrected to reduce its absolute value, so that the target rudder angle θs * in the position control is steered more than the actual steering angle θs. As a result of the offset in the neutral direction, a force that rotates the steering 2 in the neutral direction acts on the steering 2. That is, the return force of the steering wheel 2 that the driver feels “responsive” can be reproduced. As a result, it is possible to switch back in the same way as in normal times, and it is possible to avoid the deterioration of steering rigidity and the flow feeling at the end of cutting as described above. A good steering feeling can be maintained even in the continuous control when the sensor is abnormal.

  (2) The offset calculation unit 56 increases the correction amount as the absolute value of the detected steering angle θs before correction (actual steering angle) increases, that is, the corrected steering angle θs. An offset calculation is performed so that ′ becomes a value indicating a steering neutral side (small absolute value).

  According to the above configuration, the larger the cutting amount of the steering 2 is, the greater the return force is applied to the steering system. As a result, it is possible to set such that the feeling of response increases in accordance with the cut amount, and as a result, it is possible to realize a more suitable steering feeling.

In addition, you may change this embodiment as follows.
In the present embodiment, the offset calculation unit 56 calculates the correction value α based on the detected actual steering angle θs. However, the present invention is not limited to this, and the correction may be performed to reduce the absolute value so that the corrected steering angle θs ′ is offset in the steering neutral direction by a preset predetermined angle θ0. Good.

  Specifically, as shown in FIG. 6, when a predetermined angle θ0 as a correction amount is a positive value (θ0> 0), the steering angle θs before correction has a positive value (θs> 0, step 201: YES), a value obtained by subtracting the predetermined angle θ0 (positive value) from the steering angle θs (positive value) is set as a corrected steering angle θs (θs ′ = θs−θ0, step 202). . When the steering angle θs before correction has a negative value (θs <0, step 201: NO and step 203: YES), the steering angle θs (negative value) is set to a predetermined angle θ0 (positive value). ) Is used as the corrected steering angle θs (θs ′ = θs + θ0, step 204). When the steering angle θs before correction is “zero”, that is, at the steering neutral position (θ0 = 0, step 201: NO and step 203: NO), it is preferable that the offset correction is not performed (step 205). ).

  Further, the vehicle speed V detected by the vehicle speed sensor 27 as the vehicle speed detecting means, or the lateral acceleration (lateral) detected by the steering speed or acceleration detecting means (not shown) detected by the steering speed detecting means (not shown). G) may be used to calculate the correction value α.

  That is, when driving at high speed, the feeling of response during steering operation is reduced. Therefore, as shown in FIG. 7, the correction value α decreases as the vehicle speed V increases, and the correction amount of the steering angle θs decreases as the detected vehicle speed V increases. Thereby, a more natural feeling of response can be reproduced.

  In addition, as shown in FIG. 8, the absolute value of the correction value α is set to be larger as the absolute value of the detected steering speed or lateral acceleration is larger. That is, it is desirable to set the feeling of response at the time of steering operation to be stronger as the steering speed is higher or as the lateral acceleration (centrifugal force generated when the vehicle turns) is higher. Therefore, by adopting the above configuration, it is possible to realize a more suitable steering feeling by increasing the correction amount of the steering angle θs as the absolute value of the steering speed or the lateral acceleration increases. Note that when using a control signal such as a steering speed or a lateral acceleration with a large variation, it is preferable to set a dead zone in the minute region (region near “0”). Further, such a dead zone may be set also when the steering angle θs is used as in the present embodiment.

  -Furthermore, the structure which calculates correction value (alpha) based on several vehicle states may be sufficient. Specifically, for example, as shown in FIG. 9, a three-dimensional map 60 is formed by combining a configuration based on the steering angle θs (see FIG. 4) and a configuration based on the vehicle speed V (see FIG. 7). The correction value α may be calculated with reference to the three-dimensional map 60. As a result, it is possible to reproduce a more natural feeling of response and further improve the steering feeling. Needless to say, the vehicle state quantity used may be switched from the steering angle θs to the steering speed or the lateral acceleration, and the correction value α may be determined by a combination of three or more state quantities.

In the present embodiment, the present invention is embodied in a so-called column type EPS 1, but the present invention may be applied to a so-called pinion type or rack assist type EPS.
In the present embodiment, the target rudder angle calculation unit 54 calculates the target rudder angle θs * that is substantially proportional to the corrected steering angle θs ′. However, it does not necessarily have to be strictly proportional. For example, the corrected steering angle θs ′ may be used as the target steering angle θs * as it is.

  In addition, regarding the steering angle control unit 52, a dead zone map calculation unit for eliminating the influence of the midpoint error on the steering angle θs (target steering angle θs *), the converted steering angle θcnv, and the deviation Δθs, and feedback You may provide the stabilization filter etc. for improving the stability of control.

  Further, for example, if the vehicle includes a position control unit for steering or steered wheels such as an automatic parking function, the position control unit may be used as the steering angle control unit 52.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Steering, 3 ... Steering shaft, 12 ... Steering wheel, 21 ... Motor, 22 ... EPS actuator, 23 ... ECU, 27 ... Vehicle speed sensor, 28 ... Torque sensor, 29 ... Steering Sensor 41, microcomputer, 42 drive circuit 44 rotation angle sensor 45 current command value calculation unit 46 motor control signal output unit 47 basic assist control unit 49 steering torque detection unit 51 conversion Steering angle calculation unit, 52 ... Steering angle control unit, 53 ... Switching control unit, 54 ... Target steering angle calculation unit, 55 ... F / B control unit, 55 ... Offset calculation unit, Iq * ... Current command value, Ias * ... Basic assist control amount, Ipo *: rudder angle control amount, θs, θs' ... steering angle, θs * ... target rudder angle, θm ... rotation angle, θcnv ... converted rudder angle, Δθs ... deviation, V ... vehicle speed, τ ... steering Torque, Str ... Detection signal No., α ... correction value, θ0 ... predetermined angle.

Claims (5)

A steering force assisting device for assisting a steering system with assisting a steering operation using a motor as a drive source; control means for controlling the operation of the steering force assisting device through supply of driving power to the motor; A torque sensor for detecting a steering torque input to the system; and an abnormality detecting means for detecting an abnormality of the torque sensor, wherein the control means generates a motor torque corresponding to an assist force target value based on the steering torque. The electric power for supplying the driving power to stop the supply of the driving power for generating the motor torque corresponding to the assist force target value when the abnormality of the torque sensor is detected. In the steering device,
A steering angle sensor for detecting a steering angle of the steering;
A rotation angle sensor for detecting the rotation angle of the motor,
When an abnormality of the torque sensor is detected, the control means calculates a target steering angle based on the steering angle and a converted steering angle obtained by converting a rotation angle of the motor into a steering angle of the steering, In order to make the converted rudder angle follow the target rudder angle, the supply of the driving power is executed, and the steering angle that is the basis of the calculation of the target rudder angle is corrected to reduce its absolute value, An electric power steering device. The electric power steering apparatus according to claim 1, wherein
The electric power steering apparatus characterized in that the control means increases the correction amount of the steering angle as the absolute value of the steering angle before correction detected by the steering angle sensor increases. In the electric power steering device according to claim 1 or 2,
Vehicle speed detecting means for detecting the vehicle speed,
The control means reduces the steering angle correction amount as the detected vehicle speed increases;
An electric power steering device. In the electric power steering device according to any one of claims 1 to 3,
A steering speed detecting means for detecting the steering speed of the steering;
The electric power steering apparatus characterized in that the control means increases the correction amount of the steering angle as the detected steering speed increases. In the electric power steering device according to any one of claims 1 to 4,
Comprising acceleration detecting means for detecting lateral acceleration;
The electric power steering apparatus characterized in that the control means increases the correction amount of the steering angle as the detected lateral acceleration increases.

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