JP2010213550A - Motor control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control apparatus for controlling a motor by means of a new control system without using a rotational angle sensor. <P>SOLUTION: The motor control apparatus drives a motor with a γ-axis current I<SB>γ</SB>of a γδ coordinate system which is a virtual rotational coordinate system. The γδ coordinate system is a coordinate system which follows a control angle θ<SB>C</SB>which is a rotational angle on control. A difference between the control angle θ<SB>C</SB>and a rotor angle θ<SB>M</SB>is a load angle θ<SB>L</SB>. An assist torque T<SB>A</SB>corresponding to the load angle θ<SB>L</SB>occurs. Meanwhile, a steering torque T is fed back and an addition angle α is generated to bring the steering torque T near an indicated steering torque T<SP>*</SP>. By adding the addition angle α to a last value θ<SB>C</SB>(n-1) of the control angle θ<SB>C</SB>, a this-time value θ<SB>C</SB>(n) of the control angle θ<SB>C</SB>is obtained. The addition angle α is limited by the addition angle limiter 24. A limit value ω<SB>max</SB>of the addition angle limiter 24 is changed with a symbol of a multiplication value ΔT*T' obtained by multiplying a torque deviation ΔT by a steering torque differentiated value T'. <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.

The invention described in claim 1 for achieving the above object is a motor control device for controlling a motor (3) including a rotor (50) and a stator (55) opposed to the rotor. Current driving means (31 to 36) for driving the motor with a shaft current value (I _γ ^* ) of a rotating coordinate system according to a control angle (θ _C ) which is a control rotation angle, and to be added to the control angle Addition angle calculation means (22, 23) for calculating the addition angle (α), and the control angle by adding the addition angle calculated by the addition angle calculation means to the previous value of the control angle every predetermined calculation cycle. There is a positive correlation between the control angle calculation means (26) for obtaining the current value of the current value, the addition angle limiting means (24) for limiting the absolute value of the addition angle to a limit value or less, and the control angle and the motor torque. Depending on whether there is a negative correlation, the addition angle limiting means Limit value changing means for changing the limit value and a (27), a motor control device. 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. For example, the addition angle is set to a value corresponding to the torque to be generated by the motor.

  In the present invention, the addition angle is limited to a value equal to or less than the limit value by the addition angle limiting means (24). By adding an appropriate limit to the addition angle in this way, 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. More specifically, the motor can be controlled more appropriately by adding a restriction so that the addition angle is set within a reasonable range with respect to the rotational speed range of the rotor.

  Furthermore, in the present invention, the limit value of the addition angle limiting means is changed according to whether there is a positive correlation or a negative correlation between the control angle and the motor torque. More specifically, the control angle exists within an angle range in which the motor torque has a positive correlation with respect to the control angle, or the control angle exists within an angle range that has a negative correlation therebetween. The limit value of the addition angle limiting means can be set to an appropriate value depending on whether or not For this reason, a motor can be controlled more appropriately.

  According to a second aspect of the present invention, the limit value changing means reduces the limit value of the addition angle limiting means from a predetermined value when there is a negative correlation between the control angle and the motor torque. The motor control device according to claim 1. When the control angle exists within an angle range in which the motor torque has a negative correlation with the control angle, it is difficult to quickly converge the control angle to an appropriate value that provides an appropriate motor torque. This is because the motor torque may change in a direction away from the appropriate motor torque by adding the addition angle to the previous value of the control angle every calculation cycle.

Therefore, in the present invention, when the control angle exists within an angle range in which the motor torque has a negative correlation with the control angle, the limit value of the addition angle limiting means is decreased from a predetermined value. Thereby, since the absolute value of the addition angle added to the previous value of the control angle can be suppressed and the control angle can be suppressed from changing, an undesired change in the motor torque can be suppressed.
When the rotor is rotated by, for example, an external force while such a state is maintained, the relationship between the control angle and the rotor angle varies with the rotation of the rotor. This leads to a state in which the control angle exists within an angle range in which the motor torque has a positive correlation with the control angle. Therefore, thereafter, if the limit value is returned to the normal value (predetermined value), the control angle can be quickly converged to an appropriate value. In this way, it is possible to prompt a return from a state in which the motor torque has a negative correlation with respect to the control angle to a state in which the motor torque has a positive correlation with respect to the control angle. It is possible to quickly converge to an appropriate value and generate an appropriate motor torque.

The normal value of the limit value (predetermined value; the limit value applied when there is a positive correlation between the control angle and the motor torque) may be, for example, a value defined by the following equation. However, the “maximum rotor angular velocity” in the following equation is the maximum value of the rotor angular velocity in electrical angle.
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 motor control device detects torque steering means (1) for detecting a steering torque applied to the operating member (10) operated for steering the vehicle, and command steering for setting command steering torque. Torque addition means (21), and the addition angle calculation means adds the angle according to a deviation between the command steering torque set by the command steering torque setting means and the steering torque detected by the torque detection means. It is preferable to calculate an angle.

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

  In this case, the limit value changing means determines whether there is a positive correlation or a negative correlation between the control angle and the motor torque based on the command steering torque and the detected steering torque. Means (steps S11 to S13) and means (steps S14 and S15) for changing the limit value of the addition angle limiting means according to the determination result of the determination means.

  More specifically, the determination means includes a sign (ΔT) of a torque deviation obtained by subtracting the detected steering torque from the command steering torque, and a change amount of the detected steering torque (for example, a change amount during a calculation cycle. Based on the coincidence / non-coincidence of the value T ′) with respect to the control angle, the control angle exists in an angle range in which the motor torque has a positive correlation or the angle range in which they have a negative correlation It may be determined whether or not a control angle exists inside. For example, the determination means may determine that there is a negative correlation between the control angle and the motor torque if the sign of the torque deviation and the sign of the amount of change in the detected steering torque do not match. Good.

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

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

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 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 figure for demonstrating the effect | action of a control angle addition amount inhibitor. It is a figure for demonstrating the effect | action of a control angle addition amount inhibitor. It is a flowchart for demonstrating the process by a control angle addition amount inhibitor.

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 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, a control angle calculation unit 26, and a control angle addition. A quantity suppressor 27, an indicated current value generation unit 31, a current deviation calculation unit 32, a PI control unit 33, a γδ / UVW conversion unit 34, a PWM (Pulse Width Modulation) control unit 35, and a UVW / γδ conversion. Part 36 is 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, for example, when the steering angle is a positive value (a state of steering to the right), the command steering torque T ^* is set to a positive value (torque to the right), and the steering angle is The instruction steering torque T ^* is set to a negative value (torque in the left direction) when the value is negative (a state in which steering is performed 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 torque deviation calculation unit 22 is a commanded steering torque T ^* set by the commanded steering torque setting unit 21 and a steering torque T detected by the torque sensor 1 (hereinafter referred to as “detected steering torque T” for distinction). Deviation (torque deviation) ΔT. The PI control unit 23 performs a PI calculation on the torque deviation ΔT. That is, the torque deviation calculation unit 22 and the PI control unit 23 constitute torque feedback control means for guiding the detected steering torque T to the command steering torque T ^* . The PI control unit 23 calculates the addition angle α for the control angle θ _C by performing PI calculation for the torque deviation ΔT.

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 addition angle α is obtained by adding the calculation results of the proportional element 23a and the integral element 23b by the adder 23c.
The 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 the upper limit value UL (positive value) and the lower limit value LL (negative value). The upper limit value UL and the lower limit value LL are determined based on the limit value ω _max (ω _max > 0). The upper limit UL and the lower limit LL of the addition angle α can be expressed by the following equations (2) and (3), respectively.

UL = + ω _max (2)
LL = −ω _max (3)
The prescribed value (for example, 45 degrees) of the limit value ω _{max x} 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, the rotor 50, as shown in the following equation (4). 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 (4)
The maximum electrical angle change amount (rotor angle change amount maximum value) of the rotor 50 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 (5). 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 computation cycle (5)
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 specified value of the limit value ω _max .
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.
Control angle addition amount control unit 27, the previous value of the control angle theta _C is either the motor torque to the control angle theta _C (assist torque) is present within an angle range having a positive correlation or negative correlation The limit value ω _max of the addition angle limiter 24 is changed depending on whether it is within the angle range having

More specifically, the control angle addition amount control unit 27, when the assist torque to the control angle theta _C is within an angle range having a positive correlation, the previous value of the control angle theta _C is present, the addition The limit value ω _max of the angle limiter 24 is set as a specified value. On the other hand, the motor torque (assist torque) is within an angle range having a negative correlation with respect to the control angle theta _C, when the previous value of the control angle theta _C is present, the limit omega _max of the addition angle limiter 24 Make it smaller than the specified value. Details of the operation of the control angle addition amount suppressor 27 will be described later.

The command current value generation unit 31 generates a current value to be passed through the coordinate axis (virtual axis) of the γδ coordinate system, which is a virtual rotation coordinate system corresponding to the control angle θ _C that is a control rotation angle, as the command current value. Is. Specifically, a γ-axis command current value I _γ ^* and a δ-axis command current value I _δ ^* (hereinafter referred to as “two-phase command current value I _γδ ^* ”) are generated. The command current value generation unit 31 sets the γ-axis command current value I _γ ^* to a significant value, and sets the δ-axis command current value I _δ ^* to zero. More specifically, the command current value generation unit 31 sets the γ-axis command current value I _γ ^* based on the detected steering torque T detected by the torque sensor 1.

A setting example of the γ-axis command current value I _γ ^* with respect to the detected steering torque T is shown in FIG. A dead zone NR is set in a region where the detected steering torque T is near zero. The γ-axis command current value I _γ ^* rises steeply in a region outside the dead zone NR, and is set to be a substantially constant value above a predetermined torque. Thereby, when the driver is not operating the steering wheel 10, the energization to the motor 3 is stopped, and unnecessary power consumption is suppressed.

The current deviation calculation unit 32 includes a deviation I _γ ^* −I _γ of the γ-axis detection current I _γ with respect to the γ-axis command current value I _γ ^* generated by the command current value generation unit 31 and a δ-axis command current value I _δ ^*. A deviation I _δ ^* −I _δ of the δ-axis detection current I _δ with respect to (= 0) is calculated. The γ-axis detection current I _γ and the δ-axis detection current I _δ are supplied from the UVW / γδ conversion unit 36 to the deviation calculation unit 32.

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

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

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

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

Command steering torque T ^* and the PI control for the deviation (torque deviation) of the detected steering torque 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. 6 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.

7 and 8 are explanatory diagrams for explaining the function of the control angle addition amount suppressor 27. FIG. Figure 7 shows the relationship between the load angle theta _L and the assist torque. Figure 8 (a) and FIG. 8 (b) shows the relationship between the control angle theta _c and the assist torque.
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, as shown in FIG. 7, the change of the assist torque with respect to the load angle θ _L is monotonously increased in the section A where 0 ° ≦ θ _L <90 ° and 270 ° ≦ θ _L ≦ 360 °, and 90 ° ≦ θ _L In section B of <270 °, it decreases monotonously.

The q-axis current I _q is given by I _q = I _γ sin (θ _C −θ _M ) using the control angle θ _C and the rotor angle θ _M. Therefore, if there is no change in the rotor angle theta _M (fixed value), if the change is to be sufficiently slow, the change in the assist torque with respect to the control angle theta _C, for example, in FIG. 8 (a) (b) It is represented by a sinusoidal curve as shown. Therefore, there is a case where the control angle theta _C belongs to monotonously increasing segment A where the assist torque increases monotonously, and if they belong to the monotonically decreasing segment B which assist torque monotonously decreases. In the monotonically increasing section A, the assist torque increases as the control angle θ _C increases. That is, there is a positive correlation between the control angle theta _C and the assist torque. On the other hand, in the monotonically decreasing section B, the assist torque decreases as the control angle θ _C increases. That is, there is a negative correlation between the control angle theta _C and the assist torque.

FIG. 8A shows a case where the control angle θ _C belongs to the monotonously decreasing section B. In this situation, without changing the control angle theta _C, varying the rotor angle theta _M, for example, transitions to the situation shown in Figure 8 (b). In other words, the curve representing the change of the assist torque with respect to the control angle theta _C is, in accordance with a change in the rotor angle theta _M, is shifted in the direction of the coordinate axes of the control angle theta _C (horizontal axis). Accordingly, the monotonically increasing section A and the monotonically decreasing section B are also shifted in the horizontal axis direction of FIG. As a result, the state of FIG. 8A in which the control angle θ _C belongs to the monotonically decreasing section B transitions to the state of FIG. 8B in which the control angle θ _C belongs to the monotonically increasing section A.

In order to make the detected steering torque T coincide with the command steering torque T ^* , the PI control unit 23 increases the addition angle α when increasing the assist torque, and decreases the addition angle α when decreasing the assist torque. Works to let you. Therefore, in the monotonically increasing section A, the detected steering torque T can be quickly converged to the command steering torque T ^* by updating the control angle θ _C with the addition angle α every calculation cycle. On the other hand, in the monotonically decreasing section B, even if the addition angle α is added to the control angle θ _C for the purpose of increasing the assist torque, the assist torque may change in a direction away from the command steering torque T ^* . Operation may not be performed. That is, by repeating the addition of the addition angle α for each calculation cycle until the control angle θ _C reaches the monotonically increasing section A, the control angle θ _C can be led to an appropriate value corresponding to the desired assist torque for the first time. Therefore, in order to quickly match the detected steering torque T with the command steering torque T ^* , it is preferable to control the control angle θ _C in the monotonically increasing section A.

For example, when the steering wheel 10 is rotated, it is assumed that the control angle θ _C becomes the value θ 1 in the monotonously decreasing section B as shown in FIG. In this case, even if the control angle θ _C is increased by adding the positive addition angle α for the purpose of increasing the assist torque, the assist torque is decreased. Therefore, even if the control angle θ _C is changed in this state, the detected steering torque T cannot be quickly converged to the command steering torque T ^* .

Therefore, when the control angle addition amount suppressor 27 determines that the control angle θ _C falls into the monotonously decreasing section B, the control angle addition amount suppressor 27 suppresses the limit value ω _max of the addition angle limiter 24 to a value smaller than the specified value. That is, monotonic decrease by suppressing small change in the control angle theta _C in the section in B, and substantially inhibits the control operation as the detected steering torque T moves away from the command steering torque T ^*. When the steering wheel 10 rotates while the change in the control angle θ _C is suppressed in this way, the rotor rotates accordingly. As a result, the assist torque characteristic with respect to the control angle θ _C changes, and the control angle θ _C exists in the monotonically increasing section A as shown in FIG. Therefore, it is possible to quickly return from the state in which the control angle θ _C falls in the monotonically decreasing section B to the state in which the control angle θ _C exists in the monotonically increasing section A. When the angle position of the control angle θ _C is included in the monotonically increasing section A, the control angle addition amount suppressor 27 returns the limit value ω _max of the addition angle limiter 24 to the specified value. Thus, by updating the control angle θ _C with the addition angle α, a desired assist torque can be generated quickly, and the detected steering torque T can be quickly converged to the command steering torque T ^* .

FIG. 9 is a flowchart for explaining a process that the control angle addition amount suppressor 27 repeatedly executes every calculation cycle. The control angle addition amount suppressor 27 acquires a deviation (torque deviation ΔT = T ^* −T) between the command steering torque T ^* and the detected steering torque T from the torque deviation calculation unit 22 (step S11). Further, the control angle addition amount suppressor 27 obtains a steering torque differential value T ′ (specifically, a change amount of the detected steering torque T during the calculation cycle) that is a time differential value of the detected steering torque T (step S12). . Then, the control angle addition amount suppressor 27 multiplies the torque deviation ΔT and the steering torque differential value T ′, and checks the sign (step S13).

If the sign of the multiplication value ΔT · T ′ is a positive value or zero (step S13: YES), the control angle addition amount suppressor 27 determines that the control angle θ _C exists in the monotonically increasing section A, and adds the angle limiter. The limit value ω _{max of} 24 is set as a specified value (step S14). If the sign of the multiplied value [Delta] T · T 'is negative value (step S13: NO), the control angle addition amount control unit 27 determines that the control angle theta _C is present in monotonically decreasing Section B, the addition angle limiter 24 The limit value ω _max is changed to a value smaller than the specified value (step S15).

If the torque deviation ΔT (= T ^* −T) is negative (T ^* <T), the assist torque (motor torque is insufficient. Therefore, the PI control unit 23 increases the assist torque (motor torque). Therefore, for example, the addition angle α takes a positive value, and if the control angle θ _C belongs to the monotonically increasing section A, the assist torque (motor torque) is increased. As a result, the detected steering torque T (the steering torque that the driver should apply to the steering wheel 10) decreases, so the steering torque differential value T ′ becomes a negative value, so that the multiplication value ΔT · T ′ is In other words, if the multiplication value ΔT · T ′ is a positive value, the control angle θ _C belongs to the monotonically increasing section A, and a positive value is present between the change in the control angle θ _C and the motor torque. there will be a correlation. Conversely, the control angle θ If it belongs to monotonically decreasing Section B, the assist torque (motor torque) is reduced. Thus, because the detected steering torque T is increased, the steering torque differential value T 'is a positive value. Therefore, multiplication value In other words, if the multiplication value ΔT · T ′ is a negative value, the control angle θ _C belongs to the monotonically decreasing section B, and the change in the control angle θ _C and the motor torque When the torque deviation ΔT is positive (T ^* > T), the same consideration is made, and if the multiplication value ΔT · T ′ is a positive value, the control angle θ _C belongs to monotonously increasing segment a, the control angle theta _C multiplied value [Delta] T · T 'is equal negative value is found to belong to the monotonically decreasing segment B.

Therefore, by defining the limit value ω _max according to FIG. 9, when there is a positive correlation between the control angle θ _C and the motor torque, the limit value ω _max is set as the default value, while a negative correlation is established between them. When there is a limit value, the limit value ω _max can be set to a value smaller than the predetermined value to suppress the change in the control angle θ _C.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, when the control angle addition amount suppressor 27 determines that the sign of the multiplication value ΔT · T ′ is a negative value, in order to reduce the addition angle α (the addition amount to the control angle θ _C ), One or more of the following controls may be performed in addition to or in place of the above processing.
(I) The gain (proportional gain K _P and integral gain K _I ) of the PI control unit 23 is reduced.
(Ii) The integral value (integral term) in the PI control unit 23 is reduced.
(Iii) The previous value (control angle θ _C in the previous calculation cycle) in the control angle calculation unit 26 is reduced.

In the above-described embodiment, the control angle addition amount suppressor 27 sets the limit value ω _max of the addition angle limiter 24 to the specified value if the sign of the multiplication value ΔT · T ′ is a negative value (step S13: NO). Although the value is changed to a smaller value, the limit value ω _max of the addition angle limiter 24 is changed to a value smaller than the specified value when the sign of the multiplication value ΔT · T ′ is negative for a predetermined time. You may make it do.

Further, when the sign of the multiplication value ΔT · T ′ changes from the positive value to the negative value, the limit value ω _max of the addition angle limiter 24 is gradually decreased from the current value toward the predetermined lower limit value, and the multiplication value ΔT When the sign of T ′ changes from a negative value to a positive value, the limit value ω _max of the addition angle limiter 24 may be gradually increased from the current value toward the specified value.
In the embodiments described above, but a positive correlation negative correlation is determined whether or not there between the control angle theta _C and the motor torque by using the torque deviation ΔT and steering torque differential value T ' Other methods can also be applied. For example, the sign of the addition angle α represents the sign corresponding to the direction of change of the control angle theta _C, the steering torque differential value T 'has the opposite sign to the change in direction of the motor torque (assist torque). Therefore, it determines that the 'multiplication value alpha · T with' steering torque differential value T and the addition angle alpha is a positive correlation between the addition angle theta _C and the motor torque if negative. On the contrary, if the multiplication value α · T ′ is a positive value, it can be determined that there is a negative correlation between the addition angle θ _C and the motor torque.

Further, 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. The sensorless control may be performed. Thereby, since the drive of the motor 3 can be continued even when the rotation angle sensor fails, the steering assist can be continued.
In this case, when using the rotation angle sensor, the command current value generation unit 31 may generate the δ-axis command current value I _δ ^* according to the predetermined assist characteristic according to the steering torque and the vehicle speed.

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

Furthermore, in addition to the control described above, so-called weak magnetic flux control may be introduced. This will be described below.
There is a relationship of the following equation (6) between the current i flowing through the motor 3 and the voltage V applied to the motor 3.
V−K · ω = (R + sL) · i (6)
Here, K is an induced voltage constant, ω is a rotation speed of the motor, K · ω is an induced voltage, R is a stator winding resistance, L is an inductance, and s is a differential operator.

As understood from the equation (6), since the magnitude of the current i is determined by the value obtained by subtracting the induced voltage (K · ω) from the applied voltage V, the current i that can flow through the motor 3 decreases as the induced voltage increases. Become.
When the steering wheel 10 is rotated at a high speed, the motor 3 rotates at a high speed and a large induced voltage is generated. As a result, the current i that can be passed through the motor 3 decreases, and the assist torque may be insufficient. Therefore, in such a case, it is preferable to set the δ-axis current I _δ to a significant value other than zero, and to perform the flux weakening control in which current flows in a direction in which the field is weakened (a direction in which K is apparently reduced).

Specifically, a current correction means for correcting the δ-axis command current value I _δ ^* (zero in the above embodiment) generated by the command current value generation unit 31 is provided. The current correction means obtains the rotational speed of the steering wheel 10 based on the steering angle detected by the steering angle sensor 4, and calculates the rotational speed ω of the motor 3 therefrom. When the obtained motor rotation speed ω is equal to or higher than a predetermined value (during high-speed rotation), the δ-axis command current value I _δ ^* generated by the command current value generation unit 31 (zero in the above embodiment) By adding the correction value to δ, the δ-axis command current value I _δ ^* is made a significant value other than zero.

The correction value added to the δ-axis command current value I _δ ^* is a value dependent on the motor rotational speed ω obtained by calculation. For example, the correction value is set according to a characteristic that the correction value increases in a linear function as the motor rotation speed increases.
As described above, when the motor rotation speed ω becomes equal to or higher than the predetermined value, the flux-weakening control is performed, so that the induced voltage can be reduced. As a result, a large current can flow through the motor 3 even during high-speed rotation, so that an appropriate assist torque can be generated and a good steering feeling can be realized.

  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, 4 ... Steering angle sensor, 5 ... Motor control apparatus, 11 ... Microcomputer, 26 ... Control angle calculating part, 50 ... Rotor, 51, 52, 52 ... Stator winding, 55 ... Stator

Claims (2)

A motor control device for controlling a motor including a rotor and a stator facing the rotor,
Current driving means for driving the motor with an axial current value of a rotating coordinate system according to a control angle that is a control rotation angle;
An addition angle calculation means for calculating an addition angle to be added to the control angle;
Control angle calculation means for obtaining the current value of the control angle by adding the addition angle calculated by the addition angle calculation means to the previous value of the control angle for each predetermined calculation cycle;
Addition angle limiting means for limiting the absolute value of the addition angle to a limit value or less;
A motor control device comprising: a limit value changing unit that changes a limit value of the addition angle limiting unit according to whether there is a positive correlation or a negative correlation between the control angle and the motor torque.   2. The motor control according to claim 1, wherein the limit value changing unit is configured to reduce a limit value of the addition angle limiting unit from a predetermined value when there is a negative correlation between the control angle and the motor torque. apparatus.

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