JP2010178547A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device capable of controlling a motor by a new controlling method not using a rotating angle sensor. <P>SOLUTION: The motor is driven by a γ-axis current I<SB>γ</SB>of a γδ coordinate system as an imaginary rotating coordinate system. The γδ coordinate system is a coordinate system conforming to a control angle θ<SB>C</SB>as a rotating angle in control. An assist torque corresponding to a difference (load angle θ<SB>L</SB>) between the control angle θ<SB>C</SB>and a rotor angle θ<SB>M</SB>is generated. Alternatively, a detected steering torque T is fed back and an additional angle α is generated so that the steering torque T can approximate to an instructed steering torque T<SP>*</SP>. The additional angle α is added to a previous value θ<SB>C</SB>(n-1) of the control angle θ<SB>C</SB>, thereby obtaining this time value θ<SB>C</SB>(n) of the control angle θ<SB>C</SB>. The additional angle α is limited by an additional angle limiter 24. When the detected steering torque T becomes a saturated state, a limit value changing section 27 changes the limit value to a value smaller than a predetermined angle by the additional angle limiter 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

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.

In order to achieve the above object, the invention according to claim 1 is a motor control device (5) for controlling a motor (3) including a rotor (50) and a stator (55) facing the rotor. A current driving means (31 to 36) for driving the motor with an axis current value (I _γ ^* ) of a rotating coordinate system according to a control angle (θ _C ) that is a control rotation angle; An addition angle calculation means (22, 23) for calculating an addition angle (α) to be added, and an addition angle calculated by the addition angle calculation means for each predetermined calculation cycle is added to the previous value of the control angle. A control angle calculation means (26) for obtaining the current value of the control angle, a torque detection means (1) for detecting a torque other than the motor torque applied to the drive target (2) driven by the motor, Torque detected by the torque detection means Depending and a changing means for changing the motor control mode (27,28,29,30,40,41) in a motor controller. 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.

Furthermore, in the present invention, torque other than the motor torque applied to the drive target is detected by the torque detection means. The motor control mode is changed according to the detected torque. Therefore, when there is a possibility that the detected torque becomes large and the control becomes unstable, the control can be stabilized by changing the control mode.
According to a second aspect of the present invention, in the motor control according to the first aspect, the changing means changes a motor control mode according to whether or not the torque detected by the torque detecting means is saturated. Device. For example, if the detected torque is not saturated, the normal motor control mode is set. If the detected torque is saturated, the control mode is changed to a control mode different from the normal motor control mode. Thereby, when the detected torque is saturated and a sign of control abnormality appears, the motor control mode can be changed. As a result, it is possible to suppress falling into a control abnormal state or to prompt early return from the control abnormal state.

The saturation of the detected torque specifically means that the absolute value of the detected torque is equal to or greater than a predetermined upper limit value (T _max ). The upper limit value in this case can be determined according to the specification of the torque detection means. That is, the upper limit value may be set in accordance with the boundary value of the reliable output signal range in the output signal of the torque detection means.
The invention according to claim 3 further includes addition angle limiting means (24) for limiting the addition angle added to the previous value of the control angle, and the changing means (27) is a limit value of the addition angle limiting means ( The motor control device according to claim 1 or 2, wherein (ω _max ) is changed.

  According to this configuration, by adding an appropriate limit to the addition angle, it is possible to suppress an excessive addition angle from being added to the control angle as compared to the actual rotation of the rotor. Thereby, a motor can be controlled appropriately. On the other hand, for example, when the detected torque is saturated, the limit value is changed. If the addition angle is limited by a certain limit value, there is a possibility that the control angle may cyclically take a finite number of values, which may make it difficult to converge the control angle to an appropriate value. Therefore, for example, when the detected torque is saturated or a sign of control abnormality appears, the limit value is changed from the default value, so that the control angle can be converged to an appropriate value. More specifically, the limit value may be changed from a predetermined default value to a value smaller than the default value. If the limit value is set large, the change range of the control angle is large, so that the control angle changes beyond the appropriate value, and as a result, it may be difficult to converge the control angle to the appropriate value. Therefore, when a sign of control abnormality appears, the limit value is changed to a value smaller than the default value, thereby effectively promoting the convergence of the control angle to an appropriate value.

The predetermined value may be a value determined by the following equation, for example. However, the “maximum rotor angular velocity” in the following equation is the maximum value of the rotor angular velocity in electrical angle.
Default value = maximum rotor angular velocity × computation 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.

A fourth aspect of the present invention is the motor control device according to the first or second aspect, wherein the changing means (28) changes a control gain of the addition angle calculating means. According to this configuration, it is possible to stabilize the control by appropriately changing the control gain of the addition angle calculation means according to the detected torque.
More specifically, the motor control device may include an instruction torque setting means (21) for setting an instruction torque (an instruction value of a torque other than the motor torque) to be applied to the motor drive target. Good. In this case, the addition angle calculation means may include feedback control means (22, 23) for calculating the addition angle so that the detected torque approaches the instruction torque. The changing means may change the gain of the feedback control means. For example, when the detected torque is saturated, the control can be stabilized by correcting the gain of the feedback control unit to decrease.

  A fifth aspect of the present invention is the motor control device according to the first or second aspect, wherein the changing means (29) initializes the addition angle calculating means. According to this configuration, the addition angle calculation means is initialized according to the steering torque, so that the control can be stabilized. For example, when it is considered that the detected torque is saturated and the addition angle becomes a large value and a control abnormality has occurred, the addition angle calculation means is initialized so that an early return from the control abnormality can be achieved. Can be urged. For example, when the feedback control means performs a feedback control operation including integral control (proportional integral control, proportional integral differential control, etc.), the changing means initializes (resets to zero) the integral value. May be. The changing means may initialize (add to zero) the addition angle in addition to the integral value. Specifically, the addition angle and the integral value can be initialized by initializing (reset to zero) both the proportional term and the integral term.

  A sixth aspect of the present invention is the motor control apparatus according to the first or second aspect, wherein the changing means (30) changes the shaft current value. According to this configuration, the control can be stabilized by changing the shaft current value supplied to the motor in accordance with the steering torque. For example, when it is considered that the detected torque is saturated and therefore the motor torque is insufficient, the shaft current value is corrected to be increased. Thereby, since the motor generated torque is increased, the detected torque is decreased accordingly. Therefore, control can be stabilized.

  The shaft current value does not necessarily need to be corrected for increase, and recovery from control abnormality can be promoted by correcting for decrease. For example, it is assumed that the detected torque is saturated and the absolute value of the addition angle has reached the predetermined value. At this time, as described above, several values with limited control angles may be cyclically taken, and as a result, it may be difficult to converge the control angle to an appropriate value. Therefore, when the shaft current is increased or decreased, the relationship between the necessary motor torque and the appropriate value of the control angle varies. As a result, the control angle is easily converged to an appropriate value, and the return from the control abnormality can be promoted to stabilize the control.

  A seventh aspect of the present invention is the motor control device according to the first or second aspect, wherein the changing means (40) sets a new control angle by adding a predetermined value to the control angle. According to this configuration, the operation of newly setting the control angle according to the detected torque is performed. For example, when it is considered that the detected torque is saturated and the control angle continues to take an inappropriate value, the control angle can be forcibly changed to stabilize the control. In particular, when the addition angle continues to take a constant value, the control angle may cyclically take a plurality of values with a finite number. In such a situation, there is a possibility that the state in which the control angle changes by jumping over the appropriate value according to the required torque may continue, and therefore the control angle may not be able to be a value close to the appropriate value. . Therefore, if the control angle is forcibly shifted, the possibility that the control angle takes a value close to an appropriate value increases, and accordingly, the control angle is easily converged to an appropriate value corresponding to the required torque. In this way, it is possible to prompt the return from the control abnormality.

  The motor may provide a driving force to the steering mechanism (2) of the vehicle. In this case, the torque detection means may detect a steering torque applied to the operation member (10) operated for steering the vehicle. The command torque setting means may set command steering torque as a target value of steering torque. The addition angle calculation means may calculate the addition angle according to a deviation between the instruction torque set by the instruction torque setting means and the steering torque detected by the torque detection means.

  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.

  The motor control device further includes a steering angle detection means (4) for detecting a steering angle of the operation member, and the instruction torque setting means is an instruction steering torque according to a steering angle detected by the steering angle detection means. 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 torque setting means may set the command steering torque according to the vehicle speed detected by the vehicle speed detection means (6) for detecting 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.

It is a block diagram for demonstrating the electric constitution of the electric power steering apparatus to which the motor control apparatus which concerns on 1st Embodiment of this invention is applied. 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 effect | action of a steering torque limiter. It is a figure which shows the example of a setting of (gamma) axis instruction | command electric current value. It is a flowchart for demonstrating the effect | action of an addition angle limiter. It is a flowchart for demonstrating the process by a steering torque monitoring part and a limit value change part. It is a block diagram for demonstrating the structure of the electric power steering apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the process by a steering torque monitoring part and a gain change part. It is a block diagram for demonstrating the structure of the electric power steering apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart for demonstrating the process by a steering torque monitoring part and an initialization part. It is a block diagram for demonstrating the structure of the electric power steering apparatus which concerns on 4th Embodiment of this invention. It is a flowchart for demonstrating the operation example of a steering torque monitoring part and a command electric current value correction | amendment part. It is a flowchart for demonstrating the other operation example of a steering torque monitoring part and a command electric current value correction | amendment part. It is a block diagram for demonstrating the structure of the electric power steering apparatus which concerns on 5th Embodiment of this invention. It is a flowchart for demonstrating the process by a steering torque monitoring part, a control angle correction | amendment part, and an addition angle reset part.

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 a first 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. A rotation angle (rotor angle) θ _M of the rotor 50 is a rotation angle of the d-axis with respect to the U-axis. dq coordinate system is an actual rotating coordinate system that rotates in accordance with the rotor angle theta _M. With the use of the rotor angle theta _M, coordinate conversion may be made between the UVW coordinate system and the dq coordinate system.

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 axis corresponding to the control angle θ _C is a γ-axis, and an axis advanced by 90 ° with respect to the γ-axis is a δ-axis, and a virtual two-phase rotational coordinate system (γδ coordinate system, virtual rotational coordinate system) is defined. Define. When the control angle θ _C is equal to the rotor angle θ _M , the γδ coordinate system, which is a virtual rotation coordinate system, matches the dq coordinate system, which is an actual rotation coordinate system. 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. γδ coordinate system is an imaginary rotating coordinate system that rotates in accordance with the control angle theta _C. Coordinate conversion between the UVW coordinate system and the γδ coordinate system can be performed using the control angle θ _C.

A difference between the control angle θ _C and the rotor angle θ _M is defined as a 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 onto the q-axis) contributes to the q-axis current I _q that contributes to the torque generation of the rotor 50. 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 · sin θ _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 steering torque limiter 20, an instruction steering torque setting unit 21, a torque deviation calculation unit 22, a PI (proportional integration) control unit 23, an addition angle limiter 24, and a steering torque monitoring unit. 25, control angle calculation unit 26, limit value changing unit 27, command current value generation unit 31, current deviation calculation unit 32, PI control unit 33, γδ / UVW conversion unit 34, PWM (Pulse Width A Modulation) control unit 35 and a UVW / γδ conversion unit 36 are included.

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, 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 negative. The instruction steering torque T ^* is set to a negative value (torque in the left direction) when the value is in the state (steered in the left direction). 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 a non-linear manner in the example of FIG. 4). 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 steering torque limiter 20 outputs the output of the torque sensor 1 to a predetermined upper limit saturation value + T _max (+ T _max > 0. For example, + T _max = 7 Nm) and a lower limit saturation value −T _max (−T _max <0. For example, −T _max = -7 Nm). Specifically, as shown in FIG. 5, the steering torque limiter 20 outputs the detected steering torque T of the torque sensor 1 as it is between the upper limit saturation value + T _max and the lower limit saturation value −T _max . Further, the steering torque limiter 20 outputs the upper limit saturation value + T _max when the detected steering torque T of the torque sensor 1 is equal to or higher than the upper limit saturation value + T _max . Then, the steering torque limiter 20, the detected steering torque T from the torque sensor 1 is equal to or lower than the lower saturation value -T _max, and outputs the lower saturation value -T _max. The saturation values + T _max and −T _max define the boundary of the region (reliable region) where the output signal of the torque sensor 1 is stable. That is, the output signal of the torque sensor 1 is unstable in a section exceeding the upper limit saturation value T _max and a section lower than the lower limit saturation value −T _max and does not correspond to the actual steering torque. In other words, the saturation values + T _max and −T _max are determined according to the output characteristics of the torque sensor 1.

The torque deviation calculation unit 22 is detected by the command steering torque T ^* set by the command steering torque setting unit 21 and the steering torque T detected by the torque sensor 1 and subjected to the limiting process by the steering torque limiter 20 (hereinafter, for distinction). A deviation (torque deviation) ΔT (= T ^* −T) from “detected steering torque T” is obtained. 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. Therefore, the torque feedback control means constitutes an addition angle calculation means for calculating the addition angle α.

The addition angle limiter 24 is addition angle limiting means for limiting the addition angle α obtained by the PI control unit 23. More specifically, the addition angle 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 a predetermined limit value ω _max (ω _max > 0, for example, ω _max = 45 degrees). The predetermined limit value ω _max is determined based on, for example, 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 a 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 rotor angle variation maximum value is the maximum variation of the control angle theta _C that is permitted within one calculation cycle. Therefore, the maximum value of the rotor angle change may be set as a predetermined value of the limit value ω _max . Using the limit value ω _max , 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 addition angle α after the limit processing by the addition angle limiter 24 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 (for example, zero).

The control angle calculation unit 26 includes an adder 26A that adds the addition angle α given from the addition angle 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 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 the current value θ _C (n), which is the control angle θ _C in the current calculation cycle, is obtained.
The steering torque monitoring unit 25 monitors whether or not the detected steering torque T is a saturation value + T _max or −T _max, that is, whether or not it is in a saturated state. When the detected steering torque T is in a saturated state, the steering torque monitoring unit 25 notifies the limit value changing unit 27 that the control abnormality has occurred.

For example, the steering torque limiter 20 may notify the steering torque monitoring unit 25 when the output of the torque sensor 1 is equal to or higher than the saturation value + T _max or −T _max . Based on this notification, the steering torque monitoring unit 25 may determine whether or not the detected steering torque T is saturated. That is, the steering torque monitoring unit 25 may determine whether or not the detected steering torque T is saturated based on the operating state of the steering torque limiter 20. Of course, the steering torque monitoring unit 25 may monitor the detected steering torque T after the limit generated by the steering torque limiter 20, or monitor the detected steering torque T before the limit by the steering torque limiter 20. It may be. Further, the steering torque monitoring unit 25 sets the detected steering torque T before or after the limit to an upper limit threshold value slightly smaller than the upper limit saturation value + T _max and a lower limit threshold value slightly larger than the lower limit saturation value −T _max. And may be compared. In this case, the steering torque monitoring unit 25 may determine that the detected steering torque T is saturated when the detected steering torque T is equal to or higher than the upper threshold value or equal to or lower than the lower threshold value. .

The limit value changing unit 27 changes the limit value ω _max of the addition angle limiter 24 from a predetermined value (for example, 45 degrees) to a value (for example, 5 degrees) smaller than the predetermined value. Specifically, when the steering torque monitoring unit 25 determines that the detected steering torque T is saturated, the limit value changing unit 27 changes the limit value ω _max to a value smaller than a predetermined value.
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 referred to as “two-phase command current value I _γδ ^* ”) are generated. The command current value generation 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 zero. More specifically, the command current value generation unit 31 sets the γ-axis command current value I _γ ^* based on the detected steering torque T detected by the torque sensor 1.

A setting example of the γ-axis command current value I _γ ^* with respect to the detected steering torque T is shown in FIG. A dead zone NR is set in a region where the detected steering torque T is near zero. The γ-axis command current value I _γ ^* rises steeply in a region outside the dead zone NR, and is set 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.

The current deviation calculation unit 32 includes a deviation I _γ ^* −I _γ of the γ-axis detection current I _γ with respect to the γ-axis command current value I _γ ^* generated by the command current value generation unit 31 and a δ-axis command current value I _δ ^*. A deviation I _δ ^* −I _δ of the δ-axis detection current I _δ with respect to (= 0) is calculated. 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 command voltage V _γδ ^* (γ-axis command voltage V _γ ^* and δ-axis command to be applied to the motor 3. Voltage V _δ ^* ). This two-phase command voltage V _γδ ^* is _supplied to the γδ / UVW conversion unit 34.
The γδ / UVW conversion unit 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 ^* becomes 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 this 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, for the sake of simplicity, the function of the addition angle limiter 24 is omitted.

Command steering torque T ^* and the deviation (torque deviation) of the detected steering torque T PI control for the [Delta] T (K _P is a proportionality coefficient, K _I is an integration coefficient, 1 / s is an integration operator.) By 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.

Accordingly, 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 to the q-axis current _{I q (= I γ sinθ L} ) is, as the assist torque _{T A (= K T · I} γ sinθ L), via a 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, in order to make the detected steering torque T coincide with the command steering torque T ^* , the addition angle α is obtained, and the control angle θ _C is controlled accordingly.

In this way, while a current is passed through the γ axis, which is a 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. by going, the load angle theta _L is changed, the torque corresponding to the load angle theta _L is adapted to generate 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.
FIG. 7 is a flowchart for explaining the operation of the addition angle limiter 24. The addition angle limiter 24 compares the addition angle α obtained by the PI control unit 23 with the upper limit value UL (step S1), and when the addition angle α exceeds the upper limit value UL (step S1: YES), The upper limit value UL is substituted for the addition angle α (step S2). Therefore, the upper limit value UL (= + ω _max ) is added to the control angle θ _C.

If the addition angle α obtained by the PI control unit 23 is equal to or smaller than the upper limit value UL (step S1: NO), the addition angle limiter 24 further compares the addition angle α with the lower limit value LL (step S3). If the addition angle α is less than the lower limit value (step S3: YES), the lower limit value LL is substituted for the addition angle α (step S4). Therefore, the lower limit LL (= −ω _max ) is added to the control angle θ _C.

The addition angle α obtained or lower than the lower limit LL or the upper limit UL by the PI control unit 23: if (step S3 NO), the addition angle α is used as is added to the control angle theta _C.
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 when the current is insufficient or the control is started, the transition from this state to the stable control state can be promoted.

FIG. 8 is a flowchart for explaining the change of the limit value ω _max . When the steering torque monitoring unit 25 detects the saturation of the detected steering torque T and notifies the occurrence of an abnormality accordingly (step S11: YES), the limit value changing unit 27 sets the limit value ω _max to its default value (for example, 45 degrees). ) To a smaller value (for example, 5 degrees) (step S12). As a result, the control angle θ _C fluctuates in small increments, so that a value approximate to the appropriate value can be taken, so that convergence to the appropriate value can be promoted. After the limit value ω _max is changed to a small value for a certain time (for example, 100 milliseconds) (step S13: YES), the limit value ω _max is returned to the default value (step S14).

If the predetermined value of the limit value ω _max is set to a small value, the control angle θ _C may not be allowed to follow when the steering wheel 10 is operated at high speed. Therefore, the default value of the limit value ω _max is set to a relatively large value so that the control angle θ _C can follow the maximum steering angular velocity with a good response. The limit value ω _max is preferably changed to a small value.

The time when the detected steering torque T is in a saturated state is when the magnitude of the steering torque applied to the steering wheel 10 by the driver is large. That is, when the system cannot follow the command steering torque T ^* , a control abnormality has occurred, or a sign of a control abnormality has appeared. At this time, the absolute value of the torque deviation ΔT is large, and accordingly, the absolute value of the addition angle α is large, and it is considered that the absolute value of the addition angle α exceeds the limit value ω _max. It is done. In this situation, since the absolute value of the addition angle α is limited to the limit value ω _max , the control angle θ _C changes by the limit value ω _max every control cycle. Therefore, for changing width of the control angle theta _C is large, the control angle theta _C changes jump over Tekichi, time increases the control angle theta _C until caused to converge to an appropriate value. For this reason, recovery from the control abnormality is delayed. In particular, when the limit value ω _max is set to a divisor of 360 degrees, such as 45 degrees, the control angle θ _C changes cyclically within the change width of the limit value ω _max , and the appropriate value It is even more difficult to converge.

Therefore, in this embodiment, when the detected steering torque T is saturated, the limit value ω _max is temporarily set to a value smaller than the predetermined value so that the control angle θ _C changes in small increments. As a result, it is possible to increase the possibility that the control angle θ _C takes a value in the vicinity of the appropriate value. As a result, the control angle θ _C can be converged to the appropriate value by removing the abnormal state as described above. it can. Thus, the steering assist force can be quickly released from the unstable state, so that the steering feeling can be improved.

FIG. 9 is a block diagram for explaining a configuration of an electric power steering apparatus according to the second embodiment of the present invention. In FIG. 9, the same reference numerals are given to the corresponding parts of the respective parts shown in FIG.
In this embodiment, a gain changing unit 28 that changes the gain of the PI control unit 23 is provided. When the detected steering torque T is saturated, the steering torque monitoring unit 25 notifies the gain changing unit 28 of the occurrence of a control abnormality. In response to this notification, the gain changing unit 28 corrects the gain of the PI control unit 23 to decrease.

The PI control unit 23 includes a proportional element 23a, an integral element 23b, and an adder 23c. However, _{K P} is a proportional gain, _{K I} is an integral gain, 1 / s is an integration operator. The addition angle α is obtained by adding the calculation results of the proportional element 23a and the integral element 23b by the adder 23c. The gain change unit 28, when required, the gain (proportional gain) _{K P} of the proportional element 23a, corrected to decrease the gain (integral gain) _{K I} of the integral element 23b.

  FIG. 10 is a flowchart for explaining processing by the steering torque monitoring unit 25 and the gain changing unit 28. The steering torque monitoring unit 25 determines whether or not the detected steering torque T is in a saturated state (step S21). When the detected steering torque T is saturated, the steering torque monitoring unit 25 notifies the gain changing unit 28 of the occurrence of an abnormality. In response to this, the gain changing unit 28 corrects the gain for calculating the addition angle α, that is, the gain (proportional gain and integral gain) of the PI control unit 23 by decreasing (step S22). After the gain is changed to a small value for a certain time (for example, 100 milliseconds) (step S23: YES), the gain is returned to the default value (step S24). If the determination in step S21 is negative, the gain of the PI control unit 23 is not corrected and the gain is held at a predetermined value.

When the gain of the PI control unit 23 is corrected to decrease, the absolute value of the addition angle α calculated by the PI control unit 23 becomes small. Thus, it is possible to escape from the abnormal state where the addition angle α continues limited by the addition angle limiter 24, the control angle theta _C is gradually varied in small amount of change than the limit value omega _max. As a result, the control angle θ _C can be changed in small increments, so that convergence to an appropriate value can be promoted.

In addition, it can replace with PI control part 23 and can also be set as the structure which calculates | requires addition angle (alpha) using a PID (proportional / integral / differential) calculating part. Even in this case, the gain reduction correction when an abnormality occurs may be performed for the proportional gain and the integral gain.
FIG. 11 is a block diagram for explaining the configuration of an electric power steering apparatus according to the third embodiment of the present invention. In FIG. 11, the same reference numerals are assigned to the corresponding parts of the respective parts shown in FIG.

In this embodiment, when the steering torque monitoring unit 25 detects the saturation of the detected steering torque and notifies the occurrence of an abnormality, an initialization unit 29 is provided that receives this and performs an initialization process.
FIG. 12 is a flowchart for explaining operations of the steering torque monitoring unit 25 and the initialization unit 29. When the steering torque monitoring unit 25 detects the saturation of the detected steering torque T (step S31) and notifies the occurrence of an abnormality accordingly, the initialization unit 29 performs a predetermined initialization process. In this embodiment, this initialization process is performed by (a) resetting the integral value (integral term of torque feedback control) in the PI control unit 23 (making the integral term zero), and (b) calculating by the PI control unit 23. Resetting the addition angle α (making the addition angle α zero), (c) resetting the previous value (control angle θ _C in the previous computation cycle) in the control angle computing unit 26 (making the previous value zero), and (d ) Including resetting the integral value (integral term of current feedback control) in the PI control unit 33 (making the integral term zero). The addition angle α can be reset by resetting the proportional term and the integral term in the PI control unit 23. In this case, the integral term of the PI control unit 23 is also reset at the same time.

By performing such initialization processing, it is possible to quickly escape from the state in which the addition angle α continues to be subjected to the restriction processing by the addition angle limiter 24 and to resume control. This makes it possible to promote the convergence of the optimum value of the control angle theta _C.
It is most preferable to perform all of the reset processes (a) to (d), but it is preferable to perform at least the process (a), and the reset process (b) (c) (d) One or more of them can be arbitrarily combined. Furthermore, it is more preferable to perform at least the processes (a) and (b), and one or both of (c) and (d) can be arbitrarily combined with this. Further, it is more preferable to perform at least the processes (a), (b), and (c), and the process (d) can be arbitrarily combined with this.

FIG. 13 is a block diagram for explaining a configuration of an electric power steering apparatus according to the fourth embodiment of the present invention. In FIG. 13, the same reference numerals are given to the corresponding parts of the respective parts shown in FIG.
In this embodiment, when the steering torque monitoring unit 25 detects the saturation of the detected steering torque T and notifies the occurrence of an abnormality accordingly, the command current value correction unit 30 that receives this and corrects the command current value is provided. It has been. In this embodiment, the command current value correction unit 30 corrects the γ-axis command current value I _γ ^* .

FIG. 14 is a flowchart for explaining an operation example of the steering torque monitoring unit 25 and the command current value correction unit 30. When the steering torque monitoring unit 25 detects the saturation state of the detected steering torque T and notifies the occurrence of an abnormality (step S41), the command current value correction unit 30 corrects the γ-axis command current value I _γ ^* . Specifically, the command current value correction unit 30 corrects the γ-axis command current value I _γ ^* to a value between the normal current value and the abnormal current value. The abnormal current value is a current value different from the normal current value, and may be a value larger than the normal current value or a value smaller than the normal current value.

When the saturation of the detected steering torque T is notified, the command current value correction unit 30 determines whether or not the current γ-axis command current value I _γ ^* is an abnormal current value (step S42). If it is not an abnormal current value (step S42: NO), the command current value correction unit 30 changes the γ-axis command current value I _γ ^* by a constant value toward the current value at the time of abnormality (step S43). By repeating this operation at every predetermined calculation cycle, the γ-axis command current value I _γ ^* gradually changes from the normal current value toward the abnormal current value. If the γ-axis command current value I _γ ^* reaches the abnormal current value (step S42: YES), the γ-axis command current value I _γ ^* is no longer corrected.

When the detected steering torque T is not saturated (step S41: NO), the command current value correction unit 30 determines whether or not the current γ-axis command current value I _γ ^* is a normal current value (step S44). If it is not the normal current value (step S44: NO), the command current value correction unit 30 changes the γ-axis command current value I _γ ^* by a constant value toward the normal current value (step S45). By repeating this operation for each calculation cycle, the γ-axis command current value I _γ ^* gradually changes toward the normal current value. When the γ-axis command current value I _γ ^* reaches the normal current value (step S44: YES), the γ-axis command current value I _γ ^* is no longer corrected.

By correcting the γ-axis command current value I _γ ^{* in} this way, even when the control angle θ _C is changing for each calculation cycle within a predetermined change width of the limit value ω _max , the detected steering When the torque T is in a saturated state, the torque generated by the motor 3 takes a value different from the normal time. Therefore, the load angle theta _L corresponding to the required assist torque becomes a value different from the normal current value. As a result, even if the control angle theta _C is not changed by the change width of the default limit omega _max, control angle theta _C can increase the probability of taking the appropriate value. In this way, the control angle θ _C easily converges to an appropriate value, so that it is possible to escape from the abnormal state where the addition angle α is continuously limited by the addition angle limiter 24.

Further, since the γ-axis command current value I _γ ^* gradually changes between the normal current value and the abnormal current value, the assist torque does not change suddenly. Thereby, since the uncomfortable feeling given to the driver can be reduced, the steering feeling is not impaired.
FIG. 15 is a flowchart for explaining another example of the operation of the steering torque monitoring unit 25 and the command current value correcting unit 30. In FIG. 15, steps corresponding to the steps shown in FIG. 14 are given the same reference numerals.

When the steering torque monitoring unit 25 detects the saturation state of the detected steering torque T (step S41), the steering torque monitoring unit 25 further determines whether the saturation of the detected steering torque T is due to a shortage of motor current (step S46). When it is determined that the detected steering torque T is saturated due to a shortage of the motor current (step S46: YES), the steering torque monitoring unit 25 is abnormal with respect to the command current value correcting unit 30. Notify the occurrence. In response to this, the command current value correction unit 30 corrects the γ-axis command current value I _γ ^* . Specifically, the command current value correction unit 30 changes the γ-axis command current value I _γ ^* from the normal current value to the abnormal current value. For example, the normal current value may be 20 amperes and the abnormal current value may be 40 amperes.

More specifically, in response to the notification of occurrence of abnormality, the command current value correction unit 30 determines whether or not the current γ-axis command current value I _γ ^* is a current value at the time of abnormality (step S42). If it is not an abnormal current value (step S42: NO), the command current value correction unit 30 changes the γ-axis command current value I _γ ^* to an abnormal current value (step S47). Unlike the operation example of FIG. 14, in this operation example, the γ-axis command current value I _γ ^* is changed from the normal current value to the current value at the time of abnormality. As a result, early recovery from the control abnormality is achieved.

When the detected steering torque T is not saturated (step S41: NO), the command current value correction unit 30 determines whether or not the current γ-axis command current value I _γ ^* is a normal current value (step S44). If it is a normal current value (step S44: YES), the following processing is not performed in the control cycle. On the other hand, if the current value is not the normal current value (step S44: NO), the command current value correction unit 30 further determines whether or not the current γ-axis command current value I _γ ^* is an intermediate current value (step S48). The intermediate current value is a value between the normal current value and the abnormal current value. For example, when the normal current value is 20 amperes and the abnormal current value is 40 amperes, the intermediate current value may be 30 amperes. If the γ-axis command current value I _γ ^* is not the intermediate current value (step S48: NO), the current γ-axis command current value I _γ ^* is an abnormal current value. Therefore, the command current value correction unit 30 changes the γ-axis command current value I _γ ^* from the abnormal current value to the intermediate current value (step S49). If the γ-axis command current value I _γ ^* is the intermediate current value (step S48: YES), the process of step S49 is omitted.

The command current value correction unit 30 further determines whether or not a certain time (for example, 0.005 seconds) has elapsed since the γ-axis command current value I _γ ^* was changed to the intermediate current value (step S50). If this fixed time has not elapsed (step S50: NO), the processing in the control cycle is finished. When the fixed time has elapsed after the γ-axis command current value I _γ ^* is changed to the intermediate current value (step S50: YES), the command current value correction unit 30 converts the γ-axis command current value I _γ ^* to the normal current value. (Step S51). Thus, since the γ-axis command current value I _γ ^* is returned in steps from the abnormal current value to the normal current value, deterioration of the steering feeling can be suppressed.

As described above, when the control abnormality due to current shortage occurs, the γ-axis command current value I _γ ^* is increased and corrected to the current value at the time of abnormality, so that the control angle θ _C is calculated with a predetermined change width of the limit value ω _max. Even when the detected steering torque T is in a saturated state, the generated torque of the motor 3 takes a value different from the normal value even when the detected steering torque T is saturated. In addition, since the γ-axis command current value I _γ ^* is increased, the required assist torque can be easily obtained, and the control angle θ _C is more easily converged to an appropriate value, so that the addition angle α is continuously increased. It is possible to escape from the abnormal state that is limited by the limiter 24.

Determination of whether the cause of the control abnormality is due to a shortage of the motor current (step S46) is performed using, for example, the difference | I _γ ^* −I _γ | between the γ-axis command current value I _γ ^* and the γ-axis detected current _γ. Can be done. If this difference | I _γ ^* −I _γ | is smaller than a predetermined threshold value, it can be determined that the motor current is insufficient. Further, if the difference | I _γ ^* −I _γ | is equal to or greater than the threshold value, it can be determined that a counter electromotive force is generated by high-speed steering, thereby preventing current from flowing through the motor 3. In such a case (step S46: NO), it is possible to recover from the control abnormality by switching to another motor driving method suitable for high speed steering and performing drive control of the motor 3. As an example of a motor driving method suitable for high-speed steering, a disturbance observer method or the like is used to estimate the induced voltage of the motor 3, and from this, the rotation angle of the motor 3 is estimated, and this estimated rotation angle is used to estimate the motor. 3 can be mentioned.

FIG. 16 is a block diagram for explaining a configuration of an electric power steering apparatus according to the fifth embodiment of the present invention. In FIG. 16, the same reference numerals are assigned to the corresponding portions of the respective portions shown in FIG.
In this embodiment, a control angle correction unit 40 and an addition angle reset unit 41 are provided. Control angle correction unit 40, the steering torque observation unit 25 detects the saturation of the detected steering torque T, when notified of the abnormality accordingly, to correct the control angle theta _C receives this. In response to the notification of the occurrence of abnormality from the steering torque monitoring unit 25, the addition angle reset unit 41 resets the calculation (particularly the integral term) of the PI control unit 23, and resets the addition angle α to a constant value (eg, zero). . In this embodiment, the control angle correction unit 40 corrects the control angle θ _C by adding (or subtracting) a fixed correction value Δθ to the control angle θ _C. The addition of the correction value Δθ is performed in the adder 26B of the control angle calculation unit 26.

FIG. 17 is a flowchart for explaining processing by the steering torque monitoring unit 25, the control angle correction unit 40, and the addition angle reset unit 41. The steering torque monitoring unit 25 determines whether or not the detected steering torque T is saturated (step S61). If it is determined that the vehicle is saturated, the steering torque monitoring unit 25 notifies the control angle correction unit 40 and the addition angle reset unit 41 of the occurrence of an abnormality. In response to this, the control angle correction unit 40 performs correction by adding (or subtracting) the predetermined value Δθ to the control angle θ _C in the control angle calculation unit 26 (step S62). The addition angle reset unit 41 resets the addition angle α (step S63). If the detected steering torque T is not saturated state (step S61: NO), reset the correction and the addition angle α of the control angle theta _C is not performed.

As described above, the detected steering torque T is saturated when the state in which the addition angle α is subjected to the limiting process by the addition angle limiter 24 continues. In this case, since the control angle θ _C changes by the limit value ω _max every calculation cycle, the amount of change is large. In addition, since the control angle θ _C changes by a certain limit value ω _max , the control angle θ _C is in a state of taking a finite number of values cyclically. In particular, when the limit value ω _max is a divisor of 360 degrees (for example, 45 degrees), the control angle θ _C cyclically takes a small number of values. In such a state, the control angle θ _C may not be able to take a value close to an appropriate value for bringing the detected steering torque T close to the command steering torque T ^* . That is, the control angle θ _C continues to fluctuate beyond the appropriate value.

Therefore, in this embodiment, when the detected steering torque T is in a saturated state, it is determined that the abnormal state as described above has occurred, and the control angle θ _C is forcibly shifted by a predetermined value Δθ. . As a result, it is possible to increase the possibility that the control angle θ _C takes a value in the vicinity of the appropriate value. As a result, the control angle θ _C can be converged to the appropriate value by removing the abnormal state as described above. it can. In addition, in this embodiment, since the addition angle α is reset, the fluctuation range of the control angle θ _C can be reduced, so that the control angle θ _C can be more effectively converged to an appropriate value. Can do. Thus, the steering assist force can be quickly released from the unstable state, so that the steering feeling can be improved.

In this embodiment, it is not always necessary to reset the addition angle α when the detected steering torque T is saturated, and a certain effect can be obtained only by correcting the control angle θ _C.
As mentioned above, although five 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 the predetermined assist characteristic according to the steering torque and the vehicle speed.
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.

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

Claims (7)

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;
An addition angle calculation means for calculating an addition angle to be added to the control angle;
Control angle calculation means for obtaining the current value of the control angle by adding the addition angle calculated by the addition angle calculation means to the previous value of the control angle for each predetermined calculation cycle;
A torque detection means for detecting a torque other than the motor torque, which is applied to the drive target driven by the motor;
A motor control device including a changing means for changing a motor control mode in accordance with a detected torque of the torque detecting means.   The motor control device according to claim 1, wherein the changing unit changes a motor control mode according to whether or not the torque detected by the torque detecting unit is saturated. Further comprising addition angle limiting means for limiting the addition angle added to the previous value of the control angle,
The motor control apparatus according to claim 1, wherein the changing unit changes a limit value of the addition angle limiting unit.   The motor control device according to claim 1, wherein the changing unit changes a control gain of the addition angle calculating unit.   The motor control device according to claim 1, wherein the changing unit initializes the addition angle calculating unit.   The motor control device according to claim 1, wherein the changing unit changes the shaft current value.   The motor control device according to claim 1, wherein the changing unit sets a new control angle by adding a predetermined value to the control angle.

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