JP2010098810A - Motor control device - Google Patents

Abstract

A motor control apparatus capable of controlling a motor by a new control method that does not use a rotation angle sensor.
A motor is driven by a γ-axis current I _γ in a γδ coordinate system which is a virtual rotating coordinate system. The γδ coordinate system is a coordinate system according to a control angle θ _C that is a control rotation angle. The difference between the control angle θ _C and the rotor angle θ _M is the load angle θ _L. Assist torque T _A is generated according to the load angle theta _L. On the other hand, the addition angle α is generated so that the steering torque T approaches the command steering torque T ^* . By this addition angle α is added to the previous value of the control angle _{θ C θ C (n-1} ), the current value θ _C (n) is calculated in the control angle theta _C. The command current value increase determination unit 27 generates a correction value for the γ-axis command current value I _γ ^* according to the detected steering torque T, the command steering torque T ^*, and the operating state of the limiter 24. The command current value correction unit 37 temporarily increases and corrects the γ-axis command current value I _γ ^* with the correction value.
[Selection] Figure 1

Description

  The present invention relates to a motor control device for driving a brushless motor. The brushless motor can be used, for example, as a drive source for a vehicle steering apparatus. An example of a vehicle steering device is an electric power steering device.

  A motor control device for driving and controlling a brushless motor is generally configured to control the supply of motor current in accordance with the output of a rotation angle sensor for detecting the rotation angle of the rotor. As the rotation angle sensor, a resolver that outputs a sine wave signal and a cosine wave signal corresponding to the rotor rotation angle (electrical angle) is generally used. However, the resolver is expensive, has a large number of wires, and has a large installation space. Therefore, there exists a subject that the cost reduction and size reduction of an apparatus provided with the brushless motor are inhibited.

Therefore, a sensorless driving method for driving a brushless motor without using a rotation angle sensor has been proposed. The sensorless driving method is a method for estimating the phase of the magnetic pole (electrical angle of the rotor) by estimating the induced voltage accompanying the rotation of the rotor. Since the induced voltage cannot be estimated when the rotor is stopped and when rotating at a very low speed, the phase of the magnetic pole is estimated by another method. Specifically, a sensing signal is injected into the stator, and a motor response to the sensing signal is detected. Based on this motor response, the rotor rotational position is estimated.
JP 2007-267549 Gazette

  The above sensorless driving method estimates the rotational position of the rotor using an induced voltage or a sensing signal, and controls the motor based on the rotational position obtained by the estimation. However, this drive system is not suitable for any application. For example, this drive system is used to control a brushless motor used as a drive source of an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle. The method has not been established yet. Therefore, realization of sensorless control by another method is desired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control apparatus that can control a motor by a new control method that does not use a rotation angle sensor.

The invention described in claim 1 for achieving the above object is a motor control device for controlling a motor (3) including a rotor (50) and a stator (55) opposed to the rotor. Current driving means (31 to 36) for driving the motor with an axial current value (I _γ ^* ) of a rotating coordinate system according to a control angle (θ _C ) which is a control rotation angle, and for each predetermined calculation cycle, Control angle calculation means (26) for obtaining the current value of the control angle by adding the addition angle (α) to the previous value of the control angle, and a restriction for limiting the addition angle based on a predetermined angle threshold value The motor control device includes means (24) and motor current value changing means (27, 37) for changing the motor current instruction value in accordance with the operation status of the limiting means. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.

  According to this configuration, the axis current value (hereinafter “virtual axis”) of the rotating coordinate system (γδ coordinate system, hereinafter referred to as “virtual rotating coordinate system”, the coordinate axis of this virtual rotating coordinate system being referred to as “virtual axis”) according to the control angle. While the motor is driven by the "shaft current value"), the control angle is updated by adding the addition angle every calculation cycle. Thus, the necessary torque can be generated by driving the motor with the virtual axis current value while updating the control angle, that is, while updating the coordinate axis (virtual axis) of the virtual rotation coordinate system. Thus, an appropriate torque can be generated from the motor without using a rotation angle sensor. The addition angle is preferably a value corresponding to a torque to be generated by the motor or a response of the motor to the virtual axis current value.

In the present invention, by adding an appropriate limit to the addition angle by the control means, it is possible to suppress an excessive addition angle from being added to the control angle compared to the actual rotation of the rotor. More specifically, the motor can be controlled more appropriately by adding a restriction so that the addition angle is set within a reasonable range with respect to the rotational speed range of the rotor.
For example, the limiting means may limit the absolute value of the addition angle to a value equal to or less than the limit value of the following equation. However, the “maximum rotor angular velocity” in the following equation is the maximum value of the rotor angular velocity in electrical angle.

Limit value = Maximum rotor angular velocity × Calculation cycle For example, when the rotation of the motor is transmitted to the steering shaft of the vehicle steering device via a reduction mechanism having a predetermined reduction ratio, the maximum rotor angular velocity is the maximum steering angular velocity ( Steering shaft maximum rotation angular velocity) × reduction ratio × pole pair number. The “number of pole pairs” is the number of magnetic pole pairs (pairs of N poles and S poles) that the rotor has.

  In the present invention, the motor command current value is changed according to the operation status of the limiting means as described above. When the necessary torque is not generated from the motor, the addition angle increases and reaches the limit value by the limiter. However, since the necessary steering torque cannot be obtained at any control angle if the motor current is insufficient, the addition angle is maintained at the limit value and cannot be converged to an appropriate control angle. . Therefore, in the present invention, the motor command current value is changed. More specifically, when the addition angle is limited by the limiting unit, the motor command current value is increased. Thereby, since a motor current becomes large, it becomes easy to obtain a required torque from a motor. As a result, the control angle can be converged to an appropriate value by removing from the situation where the addition angle is fixed to the limit value.

For example, the motor command current value may be corrected to increase for a certain time and then restored to the motor command current value before correction. Thereby, unnecessary power consumption can be suppressed, and overheating of the motor and its drive circuit due to a large current can be suppressed.
According to the second aspect of the present invention, there is provided an instruction torque setting means (21) for setting an instruction torque which is an instruction value of a torque to be applied to a driving object driven by the motor, and a torque for detecting a torque acting on the driving object. Detecting means (1), wherein the motor current value changing means is based on the sign of the indicated torque set by the indicated torque setting means and the sign of the change amount of the detected torque detected by the torque detecting means. The motor control device according to claim 1, wherein the motor instruction current value is changed.

  For example, when the sign of the amount of change in the detected torque is the same sign as the sign of the command torque (more specifically, when the sign of the detected torque is maintained at the same sign for a certain period of time), the motor command current value is increased and corrected. May be. In this case, since the detected torque is close to the command torque, it can be said that there is a positive correlation between the load angle and the detected torque. In this situation, if the motor command current value is increased and corrected to increase the generated torque of the motor, the detected torque can be led to the command torque. Thus, it is possible to quickly converge to an appropriate control angle.

  The increase in motor command current value may be corrected to increase the motor command current value in steps, or the motor command current value may be increased with time (for example, in proportion to the elapsed time). It may be corrected. Further, a map or a function that defines the relationship of the motor command current value with respect to time may be prepared, and the motor command current value may be corrected to increase with time according to these.

  Similarly, when the motor command current value that has been corrected to increase is restored to the value before correction, the motor command current value may be decreased stepwise, or as time elapses (for example, time elapses). The motor command current value may be decreased so as to decrease (in proportion). Furthermore, a map or a function that defines the relationship of the motor command current value with respect to the passage of time may be prepared, and the motor command current value may be reduced to a value before correction with the passage of time according to these.

A third aspect of the present invention is the motor control device according to the second aspect, further comprising means (31) for variably setting the motor command current value in accordance with the command torque set by the command torque setting means.
According to this configuration, since the motor command current value is set according to the required torque, the torque is less likely to be insufficient. That is, it becomes difficult for the addition angle to be limited by the limiting means. As a result, the control angle easily converges to an appropriate value, so that more appropriate motor control is possible. More specifically, the larger the required torque is, the larger the motor command current value is set, thereby prompting convergence to an appropriate control angle.

  The motor may provide a driving force to the steering mechanism (2) of the vehicle. In this case, the motor control device detects torque steering means (1) for detecting a steering torque applied to the operating member (10) operated for steering the vehicle, and command steering for setting command steering torque. Torque addition means (21), and the addition angle calculation means adds the angle according to a deviation between the command steering torque set by the command steering torque setting means and the steering torque detected by the torque detection means. It is preferable that the angle is calculated (22, 23).

  According to this configuration, the command steering torque is set, and the addition angle is calculated according to the deviation between the command steering torque and the steering torque (detected value). Thus, the addition angle is determined so that the steering torque becomes the command steering torque, and the control angle corresponding to the addition angle is determined. Therefore, by appropriately determining the instruction steering torque, it is possible to generate an appropriate driving force from the motor and apply it to the steering mechanism. That is, the deviation (load angle) between the coordinate axis of the rotating coordinate system (dq coordinate system) and the virtual axis according to the magnetic pole direction of the rotor is led to a value corresponding to the command steering torque. As a result, an appropriate torque is generated from the motor, and a driving force according to the driver's steering intention can be applied to the steering mechanism.

  In a vehicle steering device (for example, an electric power steering device) in which an operation member and a steering mechanism are mechanically coupled, the motor response (torque generated by the motor) to the virtual axis current value is the change in the detected steering torque. It appears. Therefore, in such a vehicle steering apparatus, it can be said that calculating the addition angle in accordance with the detected steering torque calculates the addition angle in accordance with the motor response to the virtual axis current value.

  The motor control device further includes a steering angle detection means (4) for detecting a steering angle of the operation member, and the instruction steering torque setting means indicates instruction steering according to a steering angle detected by the steering angle detection means. The torque is preferably set. According to this configuration, since the instruction steering torque is set according to the steering angle of the operation member, an appropriate torque according to the steering angle can be generated from the motor, and the steering torque applied to the operation member by the driver can be increased. The value can be derived according to the steering angle. Thereby, a favorable steering feeling can be obtained.

  The command steering torque setting unit may set the command steering torque according to the vehicle speed detected by the vehicle speed detection unit (6) that detects the vehicle speed of the vehicle. According to this configuration, since the command steering torque is set according to the vehicle speed, so-called vehicle speed sensitive control can be performed. As a result, a good steering feeling can be realized. For example, an excellent steering feeling can be obtained by setting the command steering torque to be smaller as the vehicle speed is higher, that is, at higher speeds.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram for explaining an electrical configuration of an electric power steering device (an example of a vehicle steering device) to which a motor control device according to an embodiment of the present invention is applied. This electric power steering apparatus includes a torque sensor 1 for detecting a steering torque T applied to a steering wheel 10 as an operation member for steering the vehicle, and a steering assist force via a speed reduction mechanism 7 to the steering mechanism 2 of the vehicle. The motor 3 (brushless motor) that gives the power, the steering angle sensor 4 that detects the steering angle that is the rotation angle of the steering wheel 10, the motor control device 5 that drives and controls the motor 3, and the electric power steering device are mounted. And a vehicle speed sensor 6 for detecting the speed of the vehicle.

The motor control device 5 drives the motor 3 according to the steering torque detected by the torque sensor 1, the steering angle detected by the steering angle sensor 4, and the vehicle speed detected by the vehicle speed sensor 6, thereby responding to the steering situation and the vehicle speed. Realize appropriate steering assistance.
In this embodiment, the motor 3 is a three-phase brushless motor. As schematically shown in FIG. 2, the rotor 50 as a field and a U-phase, V arranged in a stator 55 facing the rotor 50, V Phase and W phase stator windings 51, 52, 53. The motor 3 may be of an inner rotor type in which a stator is disposed facing the outside of the rotor, or may be of an outer rotor type in which a stator is disposed facing the inside of a cylindrical rotor.

Three-phase fixed coordinates (UVW coordinate system) are defined in which the U, V, and W axes are taken in the direction of the stator windings 51, 52, and 53 of each phase. Also, a two-phase rotational coordinate system (dq coordinate system) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 50 and the q axis (torque axis) is taken in the direction perpendicular to the d axis in the rotation plane of the rotor 50. The actual rotating coordinate system) is defined. The dq coordinate system is a rotating coordinate system that rotates with the rotor 50. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 50, the d-axis current may be set to zero and the q-axis current may be controlled according to the desired torque. The rotation angle (rotor angle) θ _M of the rotor 50 is the rotation angle of the d axis with respect to the U axis. The dq coordinate system is an actual rotating coordinate system according to the rotor angle θ _M. By using this rotor angle θ _M , coordinate conversion between the UVW coordinate system and the dq coordinate system can be performed.

On the other hand, in this embodiment, a control angle θ _C representing a control rotation angle is introduced. The control angle θ _C is a virtual rotation angle with respect to the U axis. A virtual two-phase rotating coordinate system (γδ coordinate system, virtual rotating coordinate system) is defined with a virtual axis corresponding to the control angle θ _C as a γ axis and an axis advanced by 90 ° with respect to the γ axis as a δ axis. Define. When the control angle θ _C is equal to the rotor angle θ _M , the γδ coordinate system that is the virtual rotation coordinate system and the dq coordinate system that is the actual rotation coordinate system coincide. That is, the γ-axis as the virtual axis matches the d-axis as the real axis, and the δ-axis as the virtual axis matches the q-axis as the real axis. The γδ coordinate system is a virtual rotating coordinate system according to the control angle θ _C. Coordinate conversion between the UVW coordinate system and the γδ coordinate system can be performed using the control angle θ _C.

The difference between the control angle θ _C and the rotor angle θ _M is defined as the load angle θ _L (= θ _C −θ _M ).
When the γ-axis current I _γ is supplied to the motor 3 according to the control angle θ _C, the q-axis component of the γ-axis current I _γ (orthographic projection on the q-axis) contributes to the torque generation of the rotor 50 and the q-axis current I _q Become. That is, the relationship of the following formula (1) is established between the γ-axis current I _γ and the q-axis current I _q .
I _q = I _γ · sinθ _L (1)
Refer to FIG. 1 again. The motor control device 5 detects a current flowing in a microcomputer 11, a drive circuit (inverter circuit) 12 that is controlled by the microcomputer 11 and supplies electric power to the motor 3, and a stator winding of each phase of the motor 3. And a current detection unit 13.

The current detection unit 13 uses phase currents I _U , I _V , I _W (hereinafter, collectively referred to as “three-phase detection current I _UVW ”) flowing through the stator windings 51, 52, 53 of each phase of the motor 3. To detect. These are current values in the coordinate axis directions in the UVW coordinate system.
The microcomputer 11 includes a CPU and a memory (such as a ROM and a RAM), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a command steering torque setting unit 21, a torque deviation calculation unit 22, a PI (proportional integration) control unit 23, a limiter 24, a control angle calculation unit 26, and a command current value generation unit. 31, a current deviation calculation unit 32, a PI control unit 33, a γδ / UVW conversion unit 34, a PWM (Pulse Width Modulation) control unit 35, and a UVW / γδ conversion unit 36. Further, the plurality of function processing units include an instruction current value increase determination unit 27, an instruction current value correction unit 37, a current limiting unit 38, and a current value integration unit 39.

The command steering torque setting unit 21 sets the command steering torque T ^* based on the steering angle detected by the steering angle sensor 4 and the vehicle speed detected by the vehicle speed sensor 6. For example, as shown in FIG. 4, for example, when the steering angle is a positive value (a state of steering to the right), the command steering torque T ^* is set to a positive value (torque to the right), and the steering angle is The instruction steering torque T ^* is set to a negative value (torque to the left) when the value is negative (steering to the left). Then, the command steering torque T ^* is set so that the absolute value of the steering angle increases as the absolute value of the steering angle increases (in the example of FIG. 4, the absolute value increases nonlinearly). However, the command steering torque T ^* is set within a predetermined upper limit value (positive value, for example, +6 Nm) and lower limit value (negative value, for example, −6 Nm). Further, the command steering torque T ^* is set such that the absolute value thereof decreases as the vehicle speed increases. That is, vehicle speed sensitive control is performed.

The torque deviation calculation unit 22 includes a command steering torque T ^* set by the command steering torque setting unit 21 and a steering torque T detected by the torque sensor 1 (hereinafter referred to as “detected steering torque T” for distinction). Deviation (torque deviation) ΔT. The PI control unit 23 performs a PI calculation on the torque deviation ΔT. That is, the torque deviation calculation unit 22 and the PI control unit 23 constitute torque feedback control means for guiding the detected steering torque T to the command steering torque T ^* . The PI control unit 23 calculates the addition angle α for the control angle θ _C by performing PI calculation for the torque deviation ΔT.

  The limiter 24 is a limiting unit that limits the addition angle α obtained by the PI control unit 23. More specifically, the limiter 24 limits the addition angle α to a value between a predetermined upper limit value UL (positive value) and a lower limit value LL (negative value). The upper limit value UL and the lower limit value LL are determined based on the maximum steering angular velocity. The maximum steering angular velocity is a maximum value that can be assumed as the steering angular velocity of the steering wheel 10 and is, for example, about 800 deg / sec.

The change speed of the electrical angle of the rotor 50 at the maximum steering angular speed (the angular speed at the electrical angle. The maximum rotor angular speed) is the maximum steering angular speed, the reduction ratio of the speed reduction mechanism 7, and the rotor 50 as shown in the following equation (2). Given by the product of the number of pole pairs. The number of pole pairs is the number of magnetic pole pairs (pairs of N poles and S poles) that the rotor 50 has.
Maximum rotor angular speed = Maximum steering angular speed x Reduction ratio x Number of pole pairs (2)
The maximum value of the electrical angle change amount of the rotor 50 (the maximum value of the rotor angle change amount) during the calculation (control cycle) of the control angle θ _C is the value obtained by multiplying the maximum rotor angular velocity by the calculation cycle as shown in the following equation (3). It becomes.

Maximum value of rotor angle change = Maximum rotor angular speed x Calculation cycle
= Maximum steering angular velocity x reduction ratio x number of pole pairs x calculation cycle (3)
The maximum value of the rotor angle change amount is the maximum change amount of the control angle θ _C allowed during one calculation cycle. Therefore, if the maximum value of the rotor angle change is expressed as ω _max (> 0), the upper limit value UL and the lower limit value LL of the addition angle α can be expressed by the following equations (4) and (5), respectively.

UL = + ω _max (4)
LL = −ω _max (5)
The limiter 24 compares the addition angle α obtained by the PI control unit 23 with the upper limit value UL, and substitutes the upper limit value UL for the addition angle α when the addition angle α exceeds the upper limit value UL. Therefore, the upper limit value UL (= + ω _max ) is added to the control angle θ _C. On the other hand, if the addition angle α obtained by the PI control unit 23 is less than the lower limit value LL, the lower limit value LL is substituted into the addition angle α. Therefore, the lower limit LL (= −ω _max ) is added to the control angle θ _C. If the addition angle α obtained by the PI control unit 23 is not less than the lower limit value LL and not more than the upper limit value UL, the addition angle α is used for addition to the control angle θ _{C as} it is.

In this way, the addition angle α can be limited between the upper limit value UL and the lower limit value LL, so that the control can be stabilized. More specifically, even if a control unstable state (a state where the assist force is unstable) occurs at the time of current shortage or at the start of control, it is possible to quickly transition from this state to a stable control state. Thereby, a feeling of steering can be improved.
The addition angle α after the restriction processing is added to the previous value θ _C (n−1) (n is the number of the current calculation cycle) of the control angle θ _C in the adder 26A of the control angle calculation unit 26 (Z ^-1 represents the previous value of the signal). However, the initial value of the control angle θ _C is a predetermined value (eg, zero).

The control angle calculation unit 26 includes an adder 26A that adds the addition angle α given from the limiter 24 to the previous value θ _C (n−1) of the control angle θ _C. That is, the control angle calculation unit 26 calculates the control angle θ _C at every predetermined calculation cycle. Then, the control angle θ _C in the previous calculation cycle is set as the previous value θ _C (n−1), and this value is used to obtain the current value θ _C (n) that is the control angle θ _C in the current calculation cycle.
The command current value generation unit 31 generates a current value to be passed through the coordinate axis (virtual axis) of the γδ coordinate system, which is a virtual rotation coordinate system corresponding to the control angle θ _C that is a control rotation angle, as the command current value. Is. Specifically, a γ-axis command current value I _γ ^* and a δ-axis command current value I _δ ^* (hereinafter, collectively referred to as “two-phase command current value I _γδ ^* ) are generated. The unit 31 sets the γ-axis command current value I _γ ^* to a significant value and sets the δ-axis command current value I _δ ^* to 0. More specifically, the command current value generation unit 31 includes the torque sensor 1. The γ-axis command current value I _γ ^* is set based on the detected steering torque T detected by the command, the command steering torque T ^* set by the command steering torque setting unit 21, and the vehicle speed detected by the vehicle speed sensor 6. .

Examples of setting the γ-axis command current value I _γ ^* with respect to the detected steering torque T are shown in FIGS. 5A and 5B. 5A shows the characteristics of the basic value of the γ-axis command current value I _γ ^* , and FIGS. 5B and 5C show the torque gain and the vehicle speed gain that are multiplied by the basic value obtained according to the characteristics of FIG. 5A, respectively.
As shown in FIG. 5A, a dead zone NR is set in a region where the detected steering torque T is near zero. The basic value of the γ-axis command current value I _γ ^* is set so as to rise steeply in a region outside the dead zone NR and to be a substantially constant value above a predetermined torque. Thereby, when the driver is not operating the steering wheel 10, the energization to the motor 3 is stopped, and unnecessary power consumption is suppressed.

Furthermore, as shown in FIG. 5B, the torque gain multiplied by the basic value of the γ-axis command current value I _γ ^* is determined so as to increase as the command steering torque T increases. More specifically, the command steering torque section is divided into a low torque section, a middle torque section, and a high torque section. In the low torque section, the torque gain is fixed to the lower limit value, and in the high torque section, the torque gain is the upper limit. The value is fixed to a value, and is set to increase monotonously (linearly in this embodiment) from the lower limit value to the upper limit value according to the command steering torque T ^* in the middle torque section. Thereby, the γ-axis command current value I _γ ^* corresponding to the required assist torque can be set, and the necessary and sufficient γ-axis command current value I _γ ^* can be set, so that energy saving can be improved. The low torque section is a section that requires a current for generating an assist torque for suppressing the steering torque T because the steering torque T may be changed by an external force although the command steering torque T ^* is small. The middle torque section is a section in which the command steering torque T ^* is large and there is a high possibility that a large assist torque is required. The high torque section is a section that requires a large assist torque but should suppress an increase in current for motor protection and the like. The characteristics shown in FIG. 5B are merely examples, and it is sufficient that the torque gain tends to increase as the command steering torque T ^* increases.

Further, as shown in FIG. 5C, the vehicle speed gain multiplied by the basic value of the γ-axis command current value I _γ ^* is a characteristic that tends to decrease as the vehicle speed increases. More specifically, the entire vehicle speed section is divided into a low speed section, a medium speed section, and a high speed section. In the low speed section, the vehicle speed gain is fixed to the upper limit value, and in the high speed section, the vehicle speed gain is fixed to the lower limit value. In the middle speed section, the vehicle speed gain is set with a characteristic that decreases monotonously (linearly in this embodiment) as the vehicle speed increases. Thereby, it is possible to perform vehicle speed sensitive control in which the assist torque is reduced as the vehicle speed is higher, and an excellent steering feeling can be realized.

Thus, the γ-axis command current value I _γ ^* is set by multiplying the basic value of the γ-axis command current value I _γ ^{* by} the torque gain and the vehicle speed gain. However, only one of the torque gain and the vehicle speed gain may be applied, or the basic value may be used as it is as the γ-axis command current value I _γ ^* without applying any of these gains.
In order to determine the torque gain, the command steering torque T ^* may be used as it is, but the command steering torque T ^{* is} subjected to filter processing (for example, a low pass filter, a band pass filter, a moving average filter, etc.). A value from which noise has been removed may be obtained, and the torque gain may be determined according to this value.

The command current value correction unit 37 corrects the γ-axis command current value I _γ ^* generated by the command current value generation unit 31. More specifically, the command current value correction unit 37 temporarily increases and corrects the γ-axis command current value I _γ ^* according to the determination result by the command current value increase determination unit 27. The command current value increase determination unit 27 generates a correction value for the γ-axis command current value I _γ ^* according to the detected steering torque T, the command steering torque T ^*, and the operating state of the limiter 24, and the command current value correction unit 37. To give.

The current limiting unit 38 limits the γ-axis command current value I _γ ^* to a predetermined value in response to the current limit command from the current value integrating unit 39. The current value integration unit 39 acquires the two-phase detection current I _γδ from the UVW / γδ conversion unit 36 and integrates it. When the integration result reaches a predetermined threshold value, a current limit command is given to the current limiter 38. The predetermined threshold value is set to a value smaller than an integrated current value when the motor 3 or the drive circuit 12 is overheated by continuous energization of the motor 3.

The current deviation calculation unit 32 includes a deviation I _γ ^* −I _γ of the γ-axis detected current I _γ with respect to the γ-axis indicated current value I _γ ^* and a δ-axis detected current I with respect to the δ-axis indicated current value I _δ ^* (= 0). calculates the deviation I _δ ^* -I _δ of _[delta]. The γ-axis command current value I _γ ^* input to the current deviation calculation unit 32 is generated by the command current value generation unit 31, corrected by the command current value correction unit 37, and limited by the current limiting unit 38 as necessary. Value. The γ-axis detection current I _γ and the δ-axis detection current I _δ are supplied from the UVW / γδ conversion unit 36 to the deviation calculation unit 32.

The UVW / γδ conversion unit 36 converts the three-phase detection current I _UVW (U-phase detection current I _U , V-phase detection current I _V and W-phase detection current I _W ) of the UVW coordinate system detected by the current detection unit 13 to γδ. Two-phase detection currents I _γ and I _{δ in the} coordinate system (hereinafter collectively referred to as “two-phase detection currents I _γδ ”). These are supplied to the current deviation calculation unit 32. For the coordinate conversion in the UVW / γδ conversion unit 36, the control angle θ _C calculated by the control angle calculation unit 26 is used.

The PI control unit 33 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 32 to thereby provide a two-phase instruction voltage V _γδ ^* (γ-axis instruction voltage V _γ ^* and δ-axis instruction to be applied to the motor 3. Voltage V _δ ^* ). This two-phase instruction voltage V _γδ ^* is _supplied to the γδ / UVW conversion unit 34.
The γδ / UVW converter 34 generates a three-phase instruction voltage V _UVW ^* by performing a coordinate conversion operation on the two-phase instruction voltage V _γδ ^* . The three-phase command voltage V _UVW ^* includes a U-phase command voltage V _U ^* , a V-phase command voltage V _V ^*, and a W-phase command voltage V _W ^* . The three-phase instruction voltage V _UVW ^* is given to the PWM control unit 35.

The PWM control unit 35 includes a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM having a duty corresponding to the U-phase instruction voltage V _U ^* , the V-phase instruction voltage V _V ^*, and the W-phase instruction voltage V _W ^* , respectively. A control signal is generated and supplied to the drive circuit 12.
The drive circuit 12 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 35, so that a voltage corresponding to the three-phase instruction voltage V _UVW ^* is a stator winding 51, 52 for each phase of the motor 3. , 53 is applied.

The current deviation calculation unit 32 and the PI control unit 33 constitute a current feedback control unit. By the function of the current feedback control means, the motor current flowing through the motor 3 is controlled so as to approach the two-phase command current value I _γδ ^* set by the command current value generation unit 31.
FIG. 3 is a control block diagram of the electric power steering apparatus. However, in order to simplify the description, the function of the limiter 24 is omitted.

By the PI control (K _P is a proportional coefficient, K _I is an integral coefficient, and 1 / s is an integral operator) with respect to a deviation (torque deviation) between the command steering torque T ^* and the detected steering torque T, the addition angle α is Generated. It is obtained by adding the addition the addition angle alpha control angle theta previous value of _{C θ C (n-1)} , the current value of the control angle _{θ C θ C (n) =} θ C (n-1) + α is Desired. At this time, the deviation between the control angle θ _C and the actual rotor angle θ _M of the rotor 50 is the load angle θ _L = θ _C −θ _M.

Therefore, when the γ-axis current I _γ is supplied according to the γ-axis command current value I _γ ^* to the γ-axis (virtual axis) of the γδ coordinate system (virtual rotation coordinate system) according to the control angle θ _C , the q-axis current I _q = I _γ sinθ _L This q-axis current I _q contributes to the torque generated by the rotor 50. That is, the value obtained by multiplying the torque constant K _T of the motor 3 by the q-axis current I _q (= I _γ sin θ _L ) is used as the assist torque T _A (= K _T · I _γ sin θ _L ) via the speed reduction mechanism 7. And transmitted to the steering mechanism 2. _A value obtained by subtracting the assist torque TA from the load torque _TL from the steering mechanism 2 is the steering torque T that the driver should apply to the steering wheel 10. As the steering torque T is fed back, the system operates so as to guide the steering torque T to the command steering torque T ^* . That is, the addition angle α is obtained so that the detected steering torque T matches the command steering torque T ^* , and the control angle θ _C is controlled accordingly.

In this way, while the current is passed through the γ-axis that is the virtual axis for control, the control angle θ _C is updated with the addition angle α obtained according to the deviation ΔT between the command steering torque T ^* and the detected steering torque T. As a result, the load angle θ _L changes, and a torque corresponding to the load angle θ _L is generated from the motor 3. As a result, a torque corresponding to the command steering torque T ^* set based on the steering angle and the vehicle speed can be generated from the motor 3, so that an appropriate steering assist force corresponding to the steering angle and the vehicle speed can be applied to the steering mechanism 2. Can be given. That is, the steering assist control is executed such that the steering torque increases as the absolute value of the steering angle increases, and the steering torque decreases as the vehicle speed increases.

In this way, an electric power steering apparatus that can appropriately control the motor 3 without using a rotation angle sensor and perform appropriate steering assistance can be realized. Thereby, a structure can be simplified and cost reduction can be aimed at.
Figure 6 is a diagram showing an example of a change of the detected steering torque T with respect to the load angle theta _L. Since the q-axis current is changed by changing the control angle θ _C to change the load angle θ _L , the torque generated by the rotor 50 changes in a sine wave shape. In response to this, the detected steering torque T also varies sinusoidally. In a situation where the detected steering torque T (driver's steering burden) is larger than the command steering torque T ^{*, the} assist torque (steering assist force) applied from the motor 3 to the steering mechanism 2 may be insufficient. In this case, the assist torque can be increased by bringing the load angle θ _L close to 90 degrees or 270 degrees. However, when there is a great need assist torque may not be able to achieve its assist torque in either of the load angle theta _L. In this case, the detected steering torque T cannot be matched with the command steering torque T ^* . In this situation, since the PI control unit 23 increases the addition angle α, the limiter 24 operates and the addition angle α is fixed to the upper limit value UL. As a result, the control angle θ _C does not converge to an appropriate value, and cyclic fluctuations are repeated.

Therefore, in this embodiment, the command current value increase determination unit 27 operates to temporarily increase and correct the γ-axis command current value I _γ ^* when the limiter 24 operates.
FIG. 7 is a flowchart for explaining the operations of the command current value increase determination unit 27 and the command current value correction unit 37. The command current value increase determination unit 27 determines whether or not the limiter 24 is in operation (step S1). If the limiter 24 is in operation (step S1: YES), one of the following conditions A or B is satisfied. It is determined whether or not (steps S2 and S3). However, the “torque change amount” in the condition B is a change amount of the detected steering torque T between the previous control cycle and the current control cycle.

Condition A: A period within a certain time (for example, 0.001 second) after the limiter is activated.
Condition B: The torque change amount and the command steering torque T ^* have the same sign for a certain time (for example, 0.001 second).
When condition A or condition B is satisfied (step S2: YES; step S3: YES), the command current value increase determination unit 27 generates a correction value for correcting the γ-axis command current value I _γ ^* (step S2). S4). Command current value correcting unit 37, the gamma axis command current value preparation unit 31 to generate the command current value I _gamma ^*, by adding the correction value to correct the gamma -axis command current value I _gamma ^* (step S5 ). If the limiter 24 is not operating (step S1: NO), no correction value is generated and no correction is performed on the γ-axis command current value I _γ ^* . Even when the limiter 24 is in operation, when neither the condition A nor the condition B is satisfied (step S2: NO, step S3: NO), no correction value is generated, and therefore the γ-axis command current No correction is made to the value I _γ ^* .

Since the addition angle α is changed so that the detected steering torque T reaches the command steering torque T ^* , the absolute value of the addition angle α increases, and during the period immediately after the limiter 24 is activated, the load angle θ _It is considered that there is a positive correlation between _L and the detected steering torque T. Therefore, by correcting the increase in the γ-axis command current value I _γ ^* when the condition A is satisfied, it is possible to increase the motor torque in the direction in which the detected steering torque T approaches the command steering torque T ^* .

On the other hand, when the sign of the torque change amount and the sign of the command steering torque T ^* match, the detected steering torque T changes toward the command steering torque T ^* , and the load angle θ _L and the detected steering torque T It is thought that there is a positive correlation with Therefore, by correcting the increase in the γ-axis command current value I _γ ^* when the condition B is satisfied, it is possible to increase the motor torque in the direction in which the detected steering torque T approaches the command steering torque T ^* .

Note that it is not necessary to apply both the conditions A and B, and the increase correction of the γ-axis command current value I _γ ^* may be performed using only one of the conditions.
FIG. 8 is a diagram illustrating an example of a time change of the γ-axis command current value I _γ ^* due to the functions of the command current value increase determination unit 27 and the command current value correction unit 37. Step When the limiter 24 is activated by the correction value to the gamma -axis command current value I _gamma ^* is added, the gamma -axis command current value I _gamma ^*, from the uncorrected value I _.gamma.1 to the corrected value I _.gamma.2 It changes in shape. The command current value increase determination unit 27 holds the correction value at the upper limit value for a fixed time (for example, 3 seconds), and then monotonously decreases to zero with time (decreases linearly in the example of FIG. 8). Thus, the gamma -axis command current value I _gamma ^*, was changed stepwise to the corrected value I _.gamma.2, held only on the value I _.gamma.2 the predetermined time, then, before the correction over time The value gradually decreases monotonically to the value I _γ1 . In this way, the γ-axis command current value I _γ ^* is temporarily corrected to be increased.

The torque generated by the motor 3 increases as the γ-axis command current value I _γ ^* is temporarily increased and corrected. Thereby, the detected steering torque T can be set to a level substantially equal to the command steering torque T ^* at any control angle θ _C. As a result, the control angle θ _C converges to an appropriate value, and the state where the assist torque is insufficient is eliminated.
Incidentally, gamma -axis command current value I _gamma ^* increase correction may be a stepwise gamma -axis command current value I _gamma ^* corrected to increase as shown in Figure 8, with time The γ-axis command current value I _γ ^* may be corrected so as to increase (for example, in proportion to the elapsed time). Further, it is also possible to time advance to prepare a map or a function that defines the gamma -axis command current value I _gamma ^* relationship to lapse, the increase correction with the gamma -axis command current value I _gamma ^* over time in accordance with these .

Similarly, when returning the increased corrected γ-axis command current value I _γ ^* to the value before correction, the γ-axis command current value I _γ ^* may be decreased stepwise, as shown in FIG. As shown in FIG. 6, the γ-axis command current value I _γ ^* may be decreased so as to decrease with the passage of time (for example, in proportion to the passage of time). Further, a map or a function that defines the relationship of the γ-axis command current value I _γ ^* with respect to time is prepared, and the γ-axis command current value I _γ ^* is reduced to a value before correction with time. It is good as well.

When correcting the γ-axis command current value I _γ ^* , it is preferable to further reset or decrease the internal holding value of the integrator provided in the PI control unit 23. Thereby, the state where the addition angle α is fixed to the limit value in the limiter 24 can be quickly resolved.
FIG. 9 is a flowchart for explaining the contents of processing by the current value integrating unit 39 and the current limiting unit 38. The current value integration unit 39 acquires the two-phase detection current I _γδ (step S11), and integrates the two-phase detection current value I _γδ (step S12). The current limiting unit 38 calculates the estimated temperature of the motor control device 5 based on the current integrated value obtained by the current value integrating unit 39 (step S13). The motor control device 5 rises in temperature mainly due to heat generated from the drive circuit 12, and the temperature rise increases if a large current continues to flow. Then, the current limiter 38 obtains a current limit value based on the calculated estimated temperature (step S14), and limits the γ-axis command current value I _γ ^* to be equal to or less than the current limit value (step S15).

FIG. 10 is a characteristic diagram illustrating a setting example of the current limit value with respect to the estimated temperature. A constant current limit value is set for an estimated temperature below a certain threshold. In the range exceeding the threshold value, the current limit value is decreased monotonously (linearly in this embodiment) as the estimated temperature increases. In the range above the predetermined upper limit temperature, the current limit value is set to zero. By limiting the γ-axis command current value I _γ ^* with such a current limit value, it is possible to prevent the power elements provided in the motor 3 and the drive circuit 12 from being destroyed by overheating.

As shown in FIG. 11, the current limit value for the γ-axis command current value I _γ ^* is set according to the control continuation time of the motor 3 (the continuation time of γ-axis command current value I _γ ^* ≠ 0). It may be. In a situation where the γ-axis command current value I _γ ^* can be regarded as substantially constant, the continuous energization time and the heat generation amount are proportional. Therefore, an appropriate current limit value can be set based on the control duration time. Thereby, since a complicated temperature estimation calculation can be omitted, the calculation load of the microcomputer 11 can be reduced.

Instead of performing the temperature estimation calculation and the control duration time, the motor temperature may be directly measured using a temperature sensor, and the current limit value may be determined according to the measured value.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the configuration in which the motor 3 is driven exclusively by sensorless control without the rotation angle sensor has been described. However, the rotation angle sensor such as a resolver is provided, and when the rotation angle sensor fails, as described above. It is good also as a structure which performs a sensorless control. Thereby, since the drive of the motor 3 can be continued even when the rotation angle sensor fails, the steering assist can be continued.

In this case, when using the rotation angle sensor, the command current value generation unit 31 may generate the δ-axis command current value I _δ ^* according to a predetermined assist characteristic in accordance with the steering torque and the vehicle speed.
When using the output signal of the rotation angle sensor, it is not necessary to introduce the control angle θ _C because the rotor angle θ _M is obtained, and it is not necessary to use a virtual rotation coordinate system according to the control angle θ _C. That is, the d-axis current and the q-axis current may be controlled. However, if both a γδ current control unit that performs current control according to the γδ axis and a dq current control unit that performs current control according to the dq axis are provided, many of the memories (ROM) for storing programs in the microcomputer 11 Will use space. Therefore, it is preferable to share the γδ current control unit and the dq current control unit by sharing the angle variable. Specifically, the angle variable of the common current control unit may be switched so as to be used as the dq coordinate angle when the rotation angle sensor is normal and to be used as the γδ coordinate angle when the rotation angle sensor fails. Thereby, since the amount of memory used can be suppressed, the memory capacity can be reduced accordingly, and the cost can be reduced.

  Further, in the above-described embodiment, the example in which the present invention is applied to the electric power steering apparatus has been described. However, the present invention is not limited to the motor control for the electric pump type hydraulic power steering apparatus or the power steering apparatus. It can be used for control of a brushless motor provided in a steer-by-wire (SBW) system, a variable gear ratio (VGR) steering system and other vehicle steering devices. Of course, the motor control device of the present invention can be applied not only to the vehicle steering device but also to control a motor for other purposes.

  In addition, various design changes can be made within the scope of matters described in the claims.

1 is a block diagram for explaining an electrical configuration of an electric power steering apparatus to which a motor control device according to an embodiment of the present invention is applied. FIG. It is an illustration figure for demonstrating the structure of a motor. It is a control block diagram of the electric power steering device. It is a figure which shows the example of a characteristic of the instruction | indication steering torque with respect to a steering angle. It is a figure for demonstrating the example of a setting of (gamma) axis instruction | indication electric current value. It is a figure which shows an example of the change of the detection steering torque with respect to a load angle. It is a flowchart for demonstrating operation | movement of a command current value increase determination part and a command current value correction | amendment part. It is a figure which shows an example of the time change of the (gamma) -axis command current value by the function of the command current value increase determination part and the command current value correction part. It is a flowchart for demonstrating the content of the process by a current value integrating | accumulating part and a current limiting part. It is a characteristic view which shows the example of a setting of the current limiting value with respect to estimated temperature. It is a characteristic view which shows the example of a setting of the current limiting value with respect to control continuation time.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 3 ... Motor, 4 ... Steering angle sensor, 5 ... Motor control apparatus, 11 ... Microcomputer, 26 ... Control angle calculating part, 50 ... Rotor, 51, 52, 52 ... Stator winding, 55 ... Stator

Claims (3)

A motor control device for controlling a motor including a rotor and a stator facing the rotor,
Current driving means for driving the motor with an axial current value of a rotating coordinate system according to a control angle that is a control rotation angle;
Control angle calculation means for obtaining the current value of the control angle by adding the addition angle to the previous value of the control angle for each predetermined calculation cycle;
Limiting means for limiting the addition angle based on a predetermined limit value;
A motor control device including motor current value changing means for changing a motor command current value in accordance with an operation state of the limiting means. An instruction torque setting means for setting an instruction torque that is an instruction value of a torque to be applied to a drive target driven by the motor;
Torque detecting means for detecting torque acting on the drive target;
The motor current value changing means changes the motor instruction current value based on a sign of the indicated torque set by the indicated torque setting means and a sign of a change amount of the detected torque detected by the torque detecting means. The motor control device according to claim 1, wherein   The motor control device according to claim 2, further comprising means for variably setting a motor command current value in accordance with a command torque set by the command torque setting means.

Images