JP2011015594A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller capable of controlling a motor by a new controlling method not using a rotating angle sensor at rotating angle sensor failure.SOLUTION: When a sensor failure determining part 40 detects abnormality of an output signal of a resolver 8, it switches a motor control mode from a second mode to a first mode. In the first mode, the motor is driven by a γ-axis current Iof a γδ coordinate system as an imaginary rotating coordinate system. An assist torque corresponding to a difference (load angle θ) between the control angle θand a rotor angle θis generated. Alternatively, an additional angle α is generated by a PI controlling part 23 so that a detected steering torque T can approximate an instructed steering torque T. An initial value of the control angle at control mode switching is obtained from the sum of a load angle corresponding to a required motor torque at the switching, a detected value of the resolver immediately before resolver failure detection, and rotation of the rotor during a period from the occurrence of the resolver failure to the detection of the failure by the sensor failure determining part.

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. However, if the rotation angle sensor fails, the motor control cannot be continued.
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 use. For example, a brushless motor used as a drive source of 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 device that can control a motor by a new control method that does not use a rotation angle sensor when the rotation angle sensor fails.

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 36B) for driving the motor with an axial current value (I _γ ^* ) of a rotating coordinate system in accordance with a control angle (θ _C ) which is a control rotation angle, and the control angle An addition angle calculation means (23) for calculating the addition angle to be added, and 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 control angle calculation means (26) for obtaining a current value; a load angle control means including a rotation angle sensor (8) for detecting the rotation angle of the rotor; and detecting that the rotation angle sensor has failed. A failure detection means (40) and the rotation angle sensor; Switching means for switching the control mode from the motor control (second mode) based on the detection value of the rotation angle sensor to the motor control (first mode) based on the load angle control means when a malfunction of the motor is detected (40, 41, 42), and the initial value (θ _C0 ) of the control angle when the control mode is switched by the switching means, the load angle (θ _L0 ) corresponding to the motor torque required at the time of switching. , The detected value (θ _Mbefore ) of the rotation angle sensor immediately before the failure detection of the rotation angle sensor and the rotor between the occurrence of the failure of the rotation angle sensor and the detection of the failure by the failure detection means And a switching initial value calculation means (29) obtained by the sum of the rotation amount (Δθ _M ) of the motor control device. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.

  According to this configuration, when a failure of the rotation angle sensor is detected, the motor control (second mode) based on the detection value of the rotation angle sensor is changed to the motor control (first mode) based on the load angle control means. The control mode is switched. That is, when the rotation angle sensor failure is not detected, the motor control in the second mode is performed, and when the rotation angle sensor failure is detected, the motor control in the first mode is performed.

  When the motor is controlled in the first mode, the axial current of the rotating coordinate system (γδ coordinate system; hereinafter referred to as “virtual rotating coordinate system”, which is referred to as “virtual axis”) according to the control angle. While the motor is driven by a value (hereinafter referred to as “virtual axis 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. That is, an appropriate torque is generated by introducing a deviation amount (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 to an appropriate value.

On the other hand, when the motor is controlled in the second mode, the motor is driven by performing energization control on the motor based on the rotation angle of the rotor detected by the rotation angle sensor.
In the present invention, the initial value (θ _C0 ) of the control angle when the control mode is switched from the second mode to the first mode is “the load angle (θ _L0 ) corresponding to the motor torque required at the time of the switching”. And “the detected value (θ _Mbefore ) of the rotation angle sensor immediately before the detection of the failure of the rotation angle sensor” and “between the occurrence of the failure of the rotation angle sensor and the detection of the failure by the failure detection means”. It is determined by the sum of the amount of rotor rotation (Δθ _M ).

The load angle (θ _L ) is defined as the difference between the control angle (θ _C ) and the rotor rotation angle (θ _M ). The motor generates a torque corresponding to the load angle (θ _L ). The "detection value (θ _Mbefore ) of the rotation angle sensor immediately before the failure detection of the rotation angle sensor" is set to "the value of the rotor between the occurrence of the failure of the rotation angle sensor and the detection of the failure by the failure detection means". When the “rotation amount (Δθ _M )” is added, “the rotation angle of the rotor (θ _M0 ) at the time of switching” is obtained. Further, when “the load angle (θ _L0 ) corresponding to the motor torque required at the time of switching” is added to “the rotor rotation angle (θ _M0 ) at the time of switching”, the load angle (θ _L ) is A control angle (θ _C0 ) for setting to “the load angle (θ _L0 ) corresponding to the motor torque required at the time of the switching” is obtained. Therefore, when the control mode is switched from the second mode to the first mode, the necessary motor torque can be immediately generated at the switching time.

“Rotation amount of the rotor (Δθ _M ) from when the failure of the rotation angle sensor occurs until the failure is detected by the failure detection means” is, for example, “rotational angular velocity of the rotor immediately before failure detection (ω _before ) ”May be multiplied by“ failure detection time (Δt) ”. More specifically, the rotational angular velocity of the rotor may be calculated from the rotor rotational angle detected by the rotational angle sensor in the second mode. In this case, the rotational angular velocity of the rotor calculated immediately before failure detection can be used as “rotational angular velocity of the rotor immediately before failure detection (ω _before )”. The “failure detection time (Δt)” is a time required from when a failure occurs until the failure is detected by the failure detection means, and is a known value.

  According to a second aspect of the present invention, the load angle control means includes a torque detection means for detecting a torque other than the motor torque applied to a drive target driven by a motor, and an instruction torque to be applied to the drive target. Instruction torque setting means for setting the addition angle calculating means, wherein the addition angle calculation means adds the value according to a torque deviation between the instruction torque set by the instruction torque setting means and the torque detected by the torque detection means. The motor control device according to claim 1, which calculates an angle.

  In this configuration, in the first mode, 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 motor torque other than the motor torque applied to the drive target is set. Torque is detected by torque detection means. Then, the addition angle is calculated according to the deviation (torque deviation) between the command torque and the detected torque. That is, in the first mode, 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.

According to a third aspect of the invention, a load angle corresponding to a motor torque required at the time of switching is calculated from a torque detected by the torque detecting means and an indicated torque set by the indicated torque setting means. The motor control device according to claim 2, wherein the motor control device has a load angle corresponding to torque. According to this configuration, “the load angle θ _L0 corresponding to the motor torque required at the time of switching” can be obtained as follows. That is, first, the motor torque required at the switching time is obtained based on the torque detected by the torque detection means at the switching time and the command torque set by the command torque setting means. And the load angle according to the obtained motor torque is calculated | required.

  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, in the first mode, 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, in the first mode, the command steering torque is set according to the steering angle of the operation member, so that an appropriate torque according to the steering angle can be generated from the motor, and the driver can operate The steering torque applied to the member can be led to a value corresponding 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, in the first mode, the command steering torque is set according to the vehicle speed, so that 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 the (gamma) axis instruction | indication current value in a 1st mode. It is a figure which shows the example of a setting of the q-axis command electric current value in 2nd mode. It is a flowchart for demonstrating the effect | action of an addition angle limiter. It is a flowchart for demonstrating the operation | movement accompanying switching of a 1st mode and a 2nd mode. It is a figure for demonstrating the function of a switch initial value setting 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 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 assisting force via a speed reduction mechanism 7 to the steering mechanism 2 of the vehicle. Motor 3 (brushless motor) that gives a steering angle, a steering angle sensor 4 that detects a steering angle that is the rotation angle of the steering wheel 10, a resolver 8 (rotation angle sensor) that detects the rotation angle of the rotor in the motor 3, and a motor 3 and a vehicle speed sensor 6 for detecting the speed of the vehicle on which the electric power steering device is mounted. The resolver 8 generates a sine wave signal and a cosine wave signal corresponding to the rotor rotation angle (rotor rotation position).

The motor control device 5 drives the motor 3 according to the output signal of the resolver 8, 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. Realize appropriate steering assistance according to the situation and vehicle speed.
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 control angle calculation unit. 26, a rotation angle calculation unit 27, an angular velocity calculation unit 28, a switching initial value setting unit 29, a first command current value generation unit 31, a second command current generation unit 32, a current deviation calculation unit 30, PI controller 33, γδ / αβ converter 34A, αβ / UVW converter 34B, PWM (Pulse Width Modulation) controller 35, UVW / αβ converter 36A, αβ / γδ converter 36B, and sensor A failure determination unit 40, an indicated current value switching unit 41, and an angle switching unit 42 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, 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 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).

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.
Rotation angle calculating section 27 calculates the rotation angle theta _E of the rotor 50 based on the output signal of the resolver 8. Angular velocity calculating section 28, by differentiating the rotor rotation angle theta _E time, we obtain the rotation angular velocity ω of the rotor 50.

The angle switching unit 42 selects one of the control angle θ _C obtained by the control angle computing unit 26 and the rotor rotation angle θ _E obtained by the rotation angle computing unit 27, and performs coordinate conversion. and outputs as the transformation angle theta _S.
The first command current value generation unit 31 uses, as the command current value, a current value to be passed through the coordinate axis (virtual axis) of the γδ coordinate system that is a virtual rotation coordinate system corresponding to the control angle θ _C that is a control rotation angle. Is to be generated. 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 first 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 first 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 and subjected to the limiting process by the steering torque limiter 20. To do.

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 second command current value generation unit 32 generates a current value to be passed through the coordinate axes of the dq coordinate system as the command current value. Specifically, a d-axis command current value I _d ^* and a q-axis command current value I _q ^* (hereinafter, collectively referred to as “two-phase command current value I _dq ^* ”) are generated. More specifically, the second command current value generation unit 32 sets the q-axis command current value I _q ^* to a significant value and sets the d-axis command current value I _d ^* to zero. More specifically, the second command current value generation unit 32 sets the q-axis command current value I _q ^* based on the detected steering torque T detected by the torque sensor 1 and subjected to the limiting process by the steering torque limiter 20. To do.

A setting example of the q-axis command current value I _q ^* with respect to the detected steering torque T is shown in FIG. For the detected steering torque T, for example, the torque for steering in the right direction is a positive value, and the torque for steering in the left direction is a negative value. The q-axis command current value I _q ^* is a positive value when a steering assist force for rightward steering is to be generated from the motor 3, and a steering assist force for leftward steering is generated from the motor 3. When power is to be negative. The q-axis command current value I _q ^* is positive for a positive value of the detected steering torque T, and is negative for a negative value of the detected steering torque T. When the detected steering torque T is a very small value (torque dead zone) in the range of -T1 to T1 (for example, T1 = 0.4 N · m), the q-axis command current value I _q ^* is set to zero. The q-axis command current value I _q ^* is set to have a smaller absolute value as the vehicle speed detected by the vehicle speed sensor 6 is higher. As a result, a large steering assist force can be generated during low-speed traveling, and the steering assist force can be reduced during high-speed traveling.

The command current switching unit 41 includes a two-phase command current value I _γδ ^* generated by the first command current value generation unit 31 and a two-phase command current value I _dq ^* generated by the second command current value generation unit 32. Is selected and supplied to the current deviation calculation unit 30.
The sensor failure determination unit 40 determines whether or not the resolver 8 has failed, and switches the control mode of the motor 3 according to the determination result. That is, the sensor failure determination unit 40 functions as a failure detection unit and a switching unit. For example, the sensor failure determination unit 40 detects a failure of the resolver 8, a disconnection failure of the signal line of the resolver 8, and a ground failure of the signal line of the resolver 8 by monitoring a signal derived to the signal line of the resolver 8. be able to. The sensor failure determination unit 40 switches the control mode between the first mode and the second mode according to the determination result of whether or not the resolver 8 has failed, and generates a mode switching command. In response to this mode switching command, switching in the command current value switching unit 41 and the angle switching unit 42 is executed.

Specifically, when the sensor failure determination unit 40 determines that the resolver 8 has not failed (normal time), the sensor failure determination unit 40 sets the control mode to the second mode. On the other hand, when it is determined that the resolver 8 has failed (at the time of failure), the sensor failure determination unit 40 switches the control mode from the second mode to the first mode. In the second mode, the command current value switching unit 41 selects and outputs the two-phase command current value I _dq ^* generated by the second command current value generation unit 32, and the angle switching unit 42 includes the rotation angle calculation unit 27. The generated rotor rotation angle θ _E is selected and output. In the first mode, the command current value switching unit 41 selects and outputs the two-phase command current value _γδ ^* generated by the first command current value generation unit 31, and the angle switching unit 42 is generated by the control angle calculation unit 26. The control angle θ _C to be selected is selected and output.

The switching command from the sensor failure determination unit 40 is also given to the switching initial value setting unit 29. When the switching command from the sensor failure determination unit 40 commands switching from the second mode to the first mode, the switching initial value setting unit 29 switches the control angle θ _C in response to the command. The initial value θ _C0 is calculated and set in the control angle calculation unit 26. Details of the calculation method of the switching initial value θ _C0 will be described later.

The current deviation calculation unit 30 calculates the two-phase detection current I _γδ (γ-axis detection current I _γ and δ-axis detection current I _δ ) for the instruction current value I _γδ ^* or I _dq ^* selected by the instruction current value switching unit 41. Calculate the deviation. Specifically, when the command current value switching unit 41 outputs the two-phase command current value I _γδ ^* , the current deviation calculation unit 30 determines the deviation I of the γ-axis detection current I _{γ from} the γ-axis command current value I _γ ^* . _γ ^* −I _γ and a deviation I _δ ^* −I _δ of the δ axis detection current I _δ with respect to the δ axis command current value I _δ ^* (= 0) are calculated. Further, when the command current value switching unit 41 outputs the two-phase command current value I _dq ^* , the current deviation calculation unit 30 deviates the γ-axis detection current I _{γ from} the d-axis command current value I _d ^* (= 0). I _d ^* −I _γ and a deviation I _q ^* −I _δ of the δ-axis detection current I _δ with respect to the q-axis command current value I _q ^* are calculated. The γ-axis detection current I _γ and the δ-axis detection current I _δ are supplied from the αβ / γδ conversion unit 36B to the deviation calculation unit 30. The UVW / αβ conversion unit 36A outputs the three-phase detection current I _UVW (the U-phase detection current I _U , the V-phase detection current I _V and the W-phase detection current I _W ) of the UVW coordinate system detected by the current detection unit 13. The two-phase detection currents I _α and I _β (hereinafter collectively referred to as “two-phase detection current I _αβ ”) in the αβ coordinate system, which is a phase-fixed coordinate system, are converted. As shown in FIG. 2, the αβ coordinate system defines the α axis and the β axis (in the example of FIG. 2, coaxial with the U axis) orthogonal to the rotation axis of the rotor 50 with the rotation center of the rotor 50 as the origin. It is a fixed coordinate system. The αβ / γδ converter 36B converts the two-phase detection current I _αβ into two-phase detection currents I _γ and I _δ (hereinafter collectively referred to as “two-phase detection current I _γδ ”) in the γδ coordinate system. These are supplied to the current deviation calculation unit 30. For the coordinate conversion in the αβ / γδ conversion unit 36B, the conversion angle θ _S selected by the angle switching unit 42 is used.

The PI control unit 33 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 30, so that the two-phase instruction voltage V _γδ ^* (γ-axis instruction voltage V _γ ^* and δ-axis instruction to be applied to the motor 3 is obtained. Voltage V _δ ^* ). This two-phase command voltage V _γδ ^* is _supplied to the γδ / αβ conversion unit 34A.
The γδ / αβ converter 34A converts the two-phase command voltage V _γδ ^* into a two-phase command voltage V _αβ ^* in the αβ coordinate system. For this coordinate conversion, the conversion angle θ _S selected by the angle switching unit 42 is used. The two-phase command voltage V _αβ ^* is composed of an α-axis command voltage V _α ^* and a β-axis command voltage V _β ^* . The αβ / UVW conversion unit 34B generates a three-phase instruction voltage V _UVW ^* by performing a coordinate conversion operation on the two-phase instruction voltage V _αβ ^* . 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 30 and the PI control unit 33 constitute a current feedback control unit. By the function of the current feedback control means, the motor current flowing through the motor 3 is controlled so as to approach the two-phase command current value I _γδ ^* or the two-phase command current value I _dq ^* selected by the command current value switching unit 41. The
FIG. 3 is a control block diagram of the electric power steering apparatus in the first mode. 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.

As described above, in the first mode, it is possible to appropriately control the motor 3 without using the rotation angle sensor and perform appropriate steering assistance.
On the other hand, in the second mode, the two-phase command current value I _dq ^* corresponding to the detected steering torque T is set, and feedback control is performed so that the current of the motor 3 converges to the two-phase command current value I _dq ^*. Done. Then, the rotation angle theta _E of the rotor 50 is determined on the basis of the output signal of the resolver 8, by using the rotation angle theta _E, the coordinate conversion in the ?? / .alpha..beta conversion unit 34A and .alpha..beta / the ?? conversion unit 36B is performed become. That is, in the second mode, appropriate steering assistance is performed by controlling the motor 3 using the resolver 8 which is a rotation angle sensor.

  The first control means (load angle control means) is configured by the components enabled in the first mode, and the second control means is configured by the components enabled in the second mode. The first control means includes a command steering torque setting unit 21, a steering torque limiter 20, a torque deviation calculation unit 22, a PI control unit 23, an addition angle limiter 24, a control angle calculation unit 26, a first command current value generation unit 31, a current The deviation calculating unit 30, the PI control unit 33, the γδ / αβ conversion unit 34A, the αβ / UVW conversion unit 34B, the PWM control unit 35, the UVW / αβ conversion unit 36A, and the αβ / γδ conversion unit 36B are configured. The second control means includes a rotation angle calculation unit 27, a steering torque limiter 20, a second command current value generation unit 32, a current deviation calculation unit 30, a PI control unit 33, a γδ / αβ conversion unit 34A, and an αβ / UVW conversion. 34B, PWM control unit 35, UVW / αβ conversion unit 36A and αβ / γδ conversion unit 36B. That is, the first and second control means include the steering torque limiter 20, the current deviation calculation unit 30, the PI control unit 33, the γδ / αβ conversion unit 34A, the αβ / UVW conversion unit 34B, the PWM control unit 35, and the UVW / αβ conversion. The unit 36A and the αβ / γδ converter 36B are shared.

FIG. 8 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. 9 is a flowchart for explaining an operation associated with switching between the first mode and the second mode.
The sensor failure determination unit 40 determines whether or not there is a failure in the resolver 8 (step S11). When it is determined that the resolver 8 has not failed (when no sensor failure is detected) (step S11: NO), the sensor failure determination unit 40 selects the second mode (step S12). ). In other words, the motor is controlled based on the rotation angle θ _E calculated by the rotation angle calculation unit 27 so that the two-phase command current value I _dq ^* corresponding to the detected steering torque T is achieved.

On the other hand, when it is determined that the resolver 8 has failed (when a sensor failure is detected) (step S11: YES), the sensor failure determination unit 40 selects the first mode (step S13). That is, the command steering torque T ^* is the control angle theta _C updated every calculation cycle adjusting motors controlling the load angle theta _L so as to achieve (load angle adjustment method) is executed.
When the control mode is switched from the second mode to the first mode (step S13), the switching initial value setting unit 29 calculates the control angle switching initial value θ _C0 and sets it in the control angle calculation unit 26.

Next, a method for calculating the control angle switching initial value θ _C0 will be described.
As shown in FIG. 1, the switching initial value setting unit 29 is given the rotor rotation angle calculated by the rotation angle calculation unit 27 and the rotor angular velocity ω calculated by the angular velocity calculation unit 28 in the second mode. . Further, the torque deviation ΔT (= T ^* −T) calculated by the torque deviation calculating unit 22 is given to the switching initial value setting unit 29 in the first mode.

The control angle switching initial value θ _C0 is expressed by the following equation (6).
θ _C0 = “Load angle θ _L0 corresponding to the assist torque required at the time of control mode switching”
+ “Rotor rotation angle θ _Mbefore immediately before failure detection”
+ “Rotation amount Δθ _M of rotor between occurrence of failure and failure detection” (6)
The “load angle θ _L0 corresponding to the assist torque required at the time of control mode switching” is obtained from the detected steering torque T and the command steering torque T ^* at the time of control mode switching, and is the assist torque required at the time of control mode switching. The load angle corresponding to _TA0 . The assist torque _TA0 required at the time of control mode switching is expressed by the following equation (7), for example.

T _A0 = −T ^* + T = −ΔT (7)
The switching initial value setting unit 29 calculates the assist torque T _A0 required at the time of control mode switching based on the torque deviation ΔT (= T ^* −T) given from the torque deviation calculation unit 22 at the time of control mode switching.
Figure 10 shows the relationship between the load angle theta _L and the assist torque T _A. As described using FIG. 2, in the second mode, the q-axis current I _q is given by I _q = I _γ sin θ _L (θ _L = θ _C −θ _M ) using the load angle θ _L. The assist torque is a value obtained by multiplying the q-axis current I _q by the torque constant of the motor 3. Therefore, change in the assist torque T _A with respect to the load angle theta _L is represented by a curve (sine curve) as shown in FIG. 10. Assist torque _{T A} becomes a -90 ° ≦ θ _L ≦ 90 section monotonically increases in A in °, the -270 ° <θ _L <-90 ° and 90 ° <θ _L <270 ° in the section B monotonically decreasing . The switching initial value setting unit 29 obtains a load angle corresponding to the assist torque T _A0 required at the time of control mode switching within the range of section A in FIG. The corresponding load angle θ _L0 ”.

The “rotor rotation angle θ _Mbefore immediately before failure detection” is calculated by the rotation angle calculation unit 27 immediately before the sensor failure determination unit 40 detects a sensor failure and is input to the switching initial value setting unit 29. It is a horn.
“Rotation amount Δθ _M of rotor between occurrence of failure and detection of failure” is expressed by the following equation (8).

Δθ _M = “rotational angular velocity ω _{before of} failure detection” × “failure detection time Δt” (8)
The “rotational angular velocity ω _before of failure detection” is calculated by the angular velocity calculation unit 28 immediately before a sensor failure is detected by the sensor failure determination unit 40 and is input to the switching initial value setting unit 29. It is a horn. The “failure detection time Δt” is a time required from when a sensor failure occurs until the sensor failure is detected by the sensor failure determination unit 40, and is a known time that can be examined and set in advance. is there. As the “failure detection time Δt”, for example, 30 msec is set.

In the equation (6), “rotor rotation amount Δθ _M from when a failure occurs until failure is detected” is added to “rotor rotation angle θ _Mbefore immediately before failure detection”. The rotation angle θ _M0 of the rotor 50 at the time of control mode switching is obtained. Also, the resulting "rotation angle theta _M0 of the rotor 50 in the control mode switching point", by the "load angle theta _L0 corresponding to the required assist torque in the control mode switching point" is added, the load angle theta _L control angle theta _C0 is required to be set to the "control mode according to the required assist torque in the switching time point load angle theta _L0" a.

That is, when the control mode is switched is the first mode from the second mode, the control angle for setting the load angle theta _L to "control mode load angle depending on the required assist torque in the switching time point theta _L0" theta _C0 Is determined, and this is set as the initial value for switching. Therefore, when the control mode is switched from the second mode to the first mode, an assist torque corresponding to the difference between the detected steering torque T and the command steering torque T ^* (an assist torque necessary at the time of control mode switching) is immediately generated. Therefore, the steering feeling at the time of mode switching 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, “the load angle θ _L0 corresponding to the assist torque required at the time of control mode switching” used to calculate the control angle switching initial value θ _C0 (see the above equation (6)). ) Is determined from the detected steering torque T and the command steering torque T ^{* at} the control mode switching time. However, the assist torque immediately before the control mode switching (just before the failure detection) may be used as the “assist torque required at the time of control mode switching”. The assist torque immediately before the failure detection can be obtained, for example, by multiplying the q-axis command current value I _q ^* immediately before the sensor failure determination unit 40 detects the sensor failure by a torque constant.

Further, 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
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, 26 ... Control angle calculating part, 40 ... Sensor failure determination part, 41 ... Indication current switching part, 42 ... Angle Switching unit, 50 ... rotor, 51, 52, 53 ... stator winding, 55 ... stator

Claims (3)

A motor control device for controlling a motor including a rotor and a stator facing the rotor,
A 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 calculating means for calculating an addition angle to be added to the control angle; and a predetermined calculation cycle A load angle control means including a control angle calculation means for obtaining a 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 time;
A rotation angle sensor for detecting the rotation angle of the rotor;
Failure detection means for detecting that the rotation angle sensor has failed; and
Switching means for switching a control mode from motor control based on a detection value of the rotation angle sensor to motor control based on the load angle control means when a failure of the rotation angle sensor is detected;
The initial value of the control angle when the control mode is switched by the switching means, the load angle corresponding to the motor torque required at the time of the switching, and the detected value of the rotation angle sensor immediately before detecting the failure of the rotation angle sensor And a switching initial value calculating means for obtaining the sum by the amount of rotation of the rotor from when the failure of the rotation angle sensor occurs until the failure is detected by the failure detecting means. The load angle control means includes
A torque detection means for detecting a torque other than the motor torque, which is applied to the drive target driven by the motor;
An instruction torque setting means for setting an instruction torque to be applied to the drive target;
2. The motor control device according to claim 1, wherein the addition angle calculation unit calculates the addition angle according to a torque deviation between an instruction torque set by the instruction torque setting unit and a torque detected by the torque detection unit. .   The load angle corresponding to the motor torque required at the time of switching is a load angle corresponding to the motor torque calculated based on the torque detected by the torque detection means and the instruction torque set by the instruction torque setting means. The motor control device according to claim 2, wherein

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