JP2010213547A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller capable of controlling a motor by a new control method without using a rotation angle sensor. <P>SOLUTION: The motor is driven on a γ-axis current I<SB>γ</SB>of a γδ coordinate system as an imaginary rotation coordinate system. The γδ coordinate system is a coordinate system conforming to a control angle θ<SB>C</SB>as a rotation angle in control. An assist torque arises that corresponds 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>. On the contrary, an addition angle α is generated by a PI control section 23 so that a detection steering torque T may approximate to an indicated steering torque T<SP>*</SP>. The addition angle α is added to a previous value θ<SB>C</SB>(n-1) of the control angle θ<SB>C</SB>, thereby obtaining the current time value θ<SB>C</SB>(n) of the control angle θ<SB>C</SB>. The addition angle α is limited by an addition angle limiter 24. When a proportional term of PI operation becomes an abnormal value, the indicated current value I<SB>γ</SB><SP>*</SP>is reduced for correction, an integral term of the PI operation is initialized and the limited value by the addition angle limiter 24 is changed into a value smaller than a predetermined value. <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, a brushless motor used as a drive source for an electric power steering apparatus or other vehicle steering apparatus that applies a steering assist force to a steering mechanism of a vehicle. A method for applying to control 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 (30 to 36) for driving the motor with an axis current value (I _γ ^* ) of a rotating coordinate system in accordance with a control angle (θ _C ) which is a control rotation angle, and a predetermined calculation cycle Control angle calculation means (26) that obtains the current value of the control angle by adding the addition angle to the previous value of the control angle every time, and the motor torque that is applied to the drive target (2) driven by the motor Torque detecting means (1) for detecting the torque of the motor, instruction torque setting means (21) for setting the instruction torque to be applied to the drive target, the instruction torque and the torque set by the instruction torque setting means Inspection An addition angle calculation means (22, 23) for calculating the addition angle to be added to the control angle by proportional integration control based on a torque deviation from the torque detected by the means, and a proportional calculation value in the proportional integration control A motor control device including an abnormality detection means (25) for detecting an abnormality. 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.

  In the present invention, the command torque to be applied to the drive target (the command value of torque other than the motor torque) is set by the command torque setting means, while the torque other than the motor torque applied to the drive target is set by the torque detection means. Detected. Then, the addition angle is calculated by proportional-integral control based on the deviation (torque deviation) between the command torque and the detected torque. That is, feedback control means for calculating the addition angle so as to bring the detected torque closer to the command torque is configured. Thereby, a control angle can be controlled appropriately and a motor torque according to an instruction torque can be generated from a motor.

  For example, when the motor current is insufficient with respect to the motor load, the control angle may not be properly controlled. In such a situation, the deviation between the command torque and the detected torque becomes large, and therefore, the proportional calculation value in the proportional-integral control becomes an abnormal value (for example, an absolute value is very large). Therefore, in the present invention, the abnormality of the proportional calculation value is monitored. Thus, when an abnormality occurs in the control of the control angle, this can be detected.

  The invention according to claim 2 is the motor control device according to claim 1, further comprising current correction means (31) for reducing the shaft current value when the abnormality detection means detects an abnormality of the proportional calculation value. is there. According to this configuration, when an abnormality occurs in the proportional calculation value in the proportional-integral control, the shaft current value is corrected to decrease by the current correction unit. Thereby, generation | occurrence | production of the undesired motor torque can be suppressed. The current correction means may make the shaft current value zero. In this case, when an abnormality occurs in the proportional calculation value, the generation of the motor torque can be prohibited, so that an undesired motor torque can be prevented from being applied to the drive target when the control is abnormal.

  The invention according to claim 3 further includes initialization means (28) for initializing an integral calculation value in the proportional integral control when the abnormality detection means detects an abnormality of the proportional calculation value. 2. The motor control device according to 2. According to this configuration, when an abnormality of the proportional calculation value is detected, the integral value in the proportional integral control is initialized (for example, reset to zero), thereby stabilizing the control.

According to a fourth aspect of the present invention, there is provided addition angle limiting means (24) for limiting the absolute value of the addition angle by a predetermined limit value (ω _max ), and when the abnormality detection means detects an abnormality in the proportional calculation value. The motor control according to any one of claims 1 to 3, further comprising limit value changing means (24) for reducing the limit value in the addition angle limiting means to a value smaller than a default value at normal time. Device.

  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, when an abnormality of the proportional calculation value is detected, the limit value is changed to a value smaller than a predetermined value (a value that is applied in normal time when there is no abnormality in the proportional calculation value). 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, when an abnormality occurs in the proportional calculation value and a sign of control abnormality appears, the limit value is changed from a predetermined value to a value smaller than the predetermined 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.

  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.

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 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 relevant to the abnormality of a proportional term.

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. 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 proportional term monitoring unit. 25, a control angle calculation unit 26, a limit value changing unit 27, an initialization unit 28, a command current value generation unit 30, a command current value correction unit 31, a current deviation calculation unit 32, and 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.

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.

More specifically, 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 proportional element (proportional calculation value) of the proportional integral calculation is obtained by the proportional element 23a, and the integral term (integral calculation value) of the proportional integral calculation is obtained by the integral element 23b. These calculation results (proportional term and integral term) are added by the adder 23c, whereby the addition angle α is obtained.

  The proportional term monitoring unit 25 monitors the proportional term calculated by the proportional element 23a. More specifically, the proportional term monitoring unit 25 determines whether the absolute value of the proportional term is greater than or equal to a predetermined threshold value. Then, when the absolute value of the proportional term is equal to or greater than the threshold value, the proportional term monitoring unit 25 determines that an abnormality has occurred in the proportional term, and the determination result is used as the limit value changing unit 27 and the initialization unit 28. Then, the instruction current value correction unit 31 is notified.

The initialization unit 28 initializes (resets to zero) the integral calculation value in the integral element 23b. Specifically, when the proportional term monitoring unit 25 notifies the abnormality of the proportional term, the initialization unit 28 initializes the integral calculation value in response thereto.
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, the default value of ω _max = 45 degrees). The predetermined value of 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 limit value changing unit 27 changes the limit value ω _max between the default value and a value smaller than the default value. Specifically, the limit value changing unit 27 sets the limit value ω _max according to the determination result by the proportional term monitoring unit 25. That is, at the normal time when no abnormality occurs in the proportional term, the limit value changing unit 27 sets the limit value ω _max as the default value. On the other hand, when an abnormality occurs in the proportional term, the limit value changing unit 27 changes the limit value ω _max to a value smaller than the predetermined value.

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 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 proportional term monitoring unit 25 determines that the proportional term of the PI calculating unit 23 is equal to or greater than the threshold value, the limit value changing unit 27 sets the limit value ω _max to a value smaller than a predetermined value. change.
The command current value generation unit 30 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 30 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 30 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.

When the proportional term monitoring unit 25 determines that an abnormality has occurred in the proportional term, the command current value correcting unit 31 receives this to decrease and correct the command current value. In this embodiment, the command current value correction unit 31 corrects a decrease in the γ-axis command current value I _γ ^* . More specifically, the instruction current value correction unit 31 does not perform correction on the instruction current value (predetermined value) generated by the instruction current value generation unit 30 at normal time when no abnormality occurs in the proportional term. The current deviation calculation unit 32 is given. On the other hand, when an abnormality occurs in the proportional term, the command current value correction unit 31 corrects the γ-axis command current value I _γ ^* generated by the command current value generation unit 30 so as to reduce the command current value ( A corrected γ-axis command current value I _γ ^* ) is generated. This abnormal instruction current value is given to the current deviation calculation unit 32. The command current value correction unit 31 corrects a decrease in the γ-axis command current value I _γ ^* by multiplying the γ-axis command current value I _γ ^* generated by the command current value generation unit 30 by a gain of less than 1. May be. The command current value correction unit 31 may generate a predetermined constant current value (for example, zero) as the corrected γ-axis command current value I _γ ^* .

The current deviation calculation unit 32 generates a deviation I _γ ^{* of the} γ-axis detected current I _γ with respect to the γ-axis command current value I _γ ^* generated by the command current value generation unit 30 and corrected by the command current value correction unit 31 as necessary ^. -I _γ and a deviation I _δ ^* -I _δ of the δ-axis detected current I _δ with respect to the δ-axis command current value I _δ ^* (= 0) are 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 the current feedback control means, the motor current flowing through the motor 3 approaches the two-phase command current value I _γδ ^* set by the command current value generation unit 30 and corrected by the command current value correction unit 31 as necessary. To be controlled.
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 an operation related to the abnormality of the proportional term in the PI control unit 23. The proportional term monitoring unit 25 compares the proportional term obtained by the proportional element 23a of the PI calculating unit 23 with a predetermined threshold value (step S11). If the proportional term is greater than or equal to the threshold value (step S11: YES), the proportional term monitoring unit 25 determines that an abnormality has occurred. In response to this, the command current value correction unit 31 reduces and corrects the command current value generated by the command current value generation unit 30 to generate an abnormal current value (step S12). Further, the initialization unit 28 resets the integration value accumulated in the integration element 23b to zero (step S13). Further, the limit value changing unit 27 changes the limit value ω _max from its default value (for example, 45 degrees) to a smaller value (for example, 5 degrees) (step S14).

When the proportional term is less than the threshold value (step S11: NO), the proportional term monitoring unit 25 determines that no abnormality has occurred. In this case, the command current value correction unit 31 does not perform the correction operation, and accordingly, the command current value (predetermined value) generated by the command current value generation unit 30 is given to the current deviation calculation unit 32 (step S15). Further, the limit value changing unit 27 sets the limit value ω _max as a default value (step S16). The initialization term is not initialized by the initialization unit 28.

When it is determined that there is an abnormality in the proportional term and the processing of steps S12 to S14 is performed, if the proportional term is less than the threshold value (step S11: NO), the command current value and the limit value are returned to the predetermined values. (Steps S15 and S16).
As described above, when an abnormality occurs in the proportional term, the motor current (assist torque) is reduced by correcting the instruction current value to be reduced, so that an undesired assist torque is prevented from being applied to the steering mechanism 2. it can. When the command current value is corrected to zero, the steering assist is stopped. Thus, it is possible to realize a fail-safe operation that suppresses or stops the steering assist operation when an abnormality occurs in the control.

When an abnormality occurs in the proportional term, the integral term is initialized. The situation in which the proportional term is abnormal is a situation in which the absolute value of the deviation (torque deviation) ΔT between the command steering torque T ^* and the detected steering torque T is large. Therefore, the integral term obtained by integrating the torque deviation ΔT having a large absolute value may also have an abnormal value. Therefore, by initializing the integral term, convergence to a reasonable addition angle α can be promoted, and early recovery from an abnormal state can be promoted.

Further, when an abnormality occurs in the proportional term, the control angle θ _C varies in small increments by limiting the limit value ω _max in the addition angle limiter 24 to a value smaller than a predetermined value. As a result, the control angle θ _C can take a value approximated to an appropriate value, so that the convergence of the control angle θ _{C to} the appropriate value can be promoted.
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 case where the absolute value of the proportional term is large is when the system cannot follow the command steering torque T ^* , resulting in a control abnormality or a sign of a control abnormality appearing. 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 an abnormality is recognized in the proportional term, the limit value ω _max is set to a value smaller than the predetermined value, and 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.

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, when the proportional term is abnormal, correction of the command current value, initialization of the integral term, and change of the addition angle limit value ω _max are performed as abnormal time processing. Only one of the above may be performed as an abnormal time process, or any two may be combined and performed as an abnormal time process.

In the above-described embodiment, the proportional term calculated by the proportional element 23a is monitored. However, by monitoring the absolute value of the torque sensor ΔT obtained by the torque deviation calculating unit 22, the proportional term is substantially monitored. Can also be done.
Furthermore, in the above-described embodiment, the addition angle α is obtained by the PI control unit 23. However, instead of the PI control unit 23, the addition angle α is obtained using a PID (proportional / integral / derivative) operation unit. You can also

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 the rotation angle sensor is used, the command current value generation unit 30 may generate the δ-axis command current value I _δ ^* according to a 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, 23 ... PI control part, 23a ... Proportional element, 23b ... Integration element, 26 ... Control angle calculating part, 50 ... Rotor, 51, 52 , 52 ... Stator winding, 55 ... Stator

Claims (4)

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;
A torque detection means for detecting a torque other than the motor torque, which is applied to the drive target driven by the motor;
Command torque setting means for setting command torque to be applied to the drive target;
An addition angle calculation means for calculating the addition angle to be added to the control angle by proportional-integral control based on a torque deviation between the instruction torque set by the instruction torque setting means and the torque detected by the torque detection means; ,
A motor control device comprising: an abnormality detection means for detecting an abnormality of the proportional calculation value in the proportional-integral control.   The motor control device according to claim 1, further comprising a current correction unit that decreases the shaft current value when the abnormality detection unit detects an abnormality of the proportional calculation value.   3. The motor control device according to claim 1, further comprising an initialization unit that initializes an integral calculation value in the proportional integral control when the abnormality detection unit detects an abnormality of the proportional calculation value. Addition angle limiting means for limiting the absolute value of the addition angle with a predetermined limit value;
2. A limit value changing unit that reduces the limit value in the addition angle limiting unit to a value smaller than a normal default value when the abnormality detection unit detects an abnormality in the proportional calculation value. The motor control apparatus as described in any one of -3.

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