JP5440845B2 - Motor control device and vehicle steering device - Google Patents

Description

  The present invention relates to a motor control apparatus for driving a brushless motor and a vehicle steering apparatus including the motor control 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.

Japanese Patent Laid-Open No. 10-243699

  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, and a vehicle steering device that includes the motor control device.

In order to achieve the above object, the invention according to claim 1 is a motor control device (5) for controlling a motor (3) including a rotor (50) and a stator (55) facing the rotor. A current driving means (31-36A, 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 An addition angle calculation means (22, 23) for calculating an addition angle (α) to be added to the angle, and an addition angle calculated by the addition angle calculation means for each predetermined calculation cycle is added to the previous value of the control angle. A control angle calculation means (26) for obtaining a current value of the control angle, an angular speed calculation means (43) for calculating the angular speed of the rotor at predetermined time intervals based on the drive value of the motor, The amount of change in the motor drive value When the change amount of the drive value of the motor becomes equal to or greater than the predetermined value, the change amount of the drive value becomes equal to or greater than the predetermined value. According to the rotor angular speed (ω0) calculated immediately before by the angular speed calculating means and the rotor angular speed (ωn) calculated by the angular speed calculating means after the amount of change in the drive value exceeds the predetermined value, Angular velocity correction means (42, 71 to 75) for calculating a typical rotor angular velocity (ωF), and addition angle correction means for correcting the addition angle based on the final rotor angular velocity calculated by the angular velocity correction means ( 41). 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 referred to as “virtual axis”) of the rotational coordinate system (γδ coordinate system, hereinafter referred to as “virtual rotational coordinate system”, which is 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.

  Further, according to the present invention, the angular velocity calculating means calculates the angular velocity of the rotor at predetermined time intervals based on the driving value of the motor. Further, it is determined whether or not the change in the motor drive value is equal to or greater than a predetermined value. That is, it is determined whether or not the motor drive value has suddenly changed. When the amount of change in the drive value of the motor exceeds a predetermined value, the rotor angular velocity calculated by the angular velocity calculating means immediately before the amount of change in the drive value exceeds the predetermined value and the amount of change in the drive value are the predetermined value. After that, the final rotor angular speed is calculated according to the rotor angular speed calculated by the angular speed calculating means. Then, the addition angle is corrected based on the final rotor angular velocity.

  When the change in the motor drive value exceeds a predetermined value, that is, when the motor drive value changes suddenly, the accuracy of the rotor angular speed calculated by the angular speed calculating means may be reduced. In this invention, when the amount of change in the drive value of the motor exceeds a predetermined value, the rotor angular velocity calculated by the angular velocity calculating means immediately before the amount of change in the drive value exceeds the predetermined value and the change in the drive value. The final rotor angular velocity is calculated according to the rotor angular velocity calculated by the angular velocity calculating means after the amount becomes equal to or greater than the predetermined value. As a result, a highly accurate rotor angular velocity can be obtained as the final rotor angular velocity. Since the addition angle is corrected based on the highly accurate rotor angular speed, the motor control performance can be improved.

  According to a second aspect of the present invention, the angular velocity correction unit is configured such that the rotor angular velocity calculated by the angular velocity calculating unit immediately before the change amount of the drive value becomes equal to or greater than the predetermined value is ω0, and the change amount of the drive value is the The rotor angular velocity calculated by the angular velocity calculating means after reaching a predetermined value or more is set to ωn, and when the drive value becomes a predetermined value or more, it is set to 0, and then the weight gradually increased to 1 is finally set as ξ. The motor control device according to claim 1, wherein the rotor angular velocity ωF is calculated based on the following equation (a).

ωF = ω0 · (1-ξ) + ωn · ξ (a)
In this configuration, when the change amount of the drive value becomes equal to or greater than the predetermined value, immediately after that, the rotor angular velocity ω0 calculated by the angular velocity calculating means immediately before the change amount of the drive value becomes equal to or greater than the predetermined value is large. The final rotor angular velocity ωF is obtained by assigning a weight, and thereafter, the final rotor angular velocity ωF is obtained by gradually increasing the weight of the rotor angular velocity ωn calculated by the angular velocity calculating means. In such a final method of calculating the rotor angular velocity ωF, the accuracy of the rotor angular velocity ωn calculated by the angular velocity calculating means temporarily deteriorates when the drive value changes suddenly, but thereafter gradually recovers. It is suitable to go. For this reason, the final rotor angular velocity ωF calculated by the angular velocity correcting means is higher in accuracy than the rotor angular speed ωn calculated by the angular velocity calculating means.

  A third aspect of the present invention is a vehicle steering apparatus including a motor that applies a driving force to a steering mechanism of a vehicle and the motor control apparatus according to the first or second aspect that controls the motor. According to this configuration, even when the driving value of the motor changes suddenly, a highly accurate rotor angular velocity can be obtained, so that the vehicle can improve the control performance of the motor that applies the driving force to the steering mechanism of the vehicle. A steering device is obtained. Thereby, the steering apparatus for vehicles with a good steering feeling can be provided.

The motor control device includes a torque detection means (1) for detecting a torque (T) other than the motor torque applied to a drive target driven by the motor, and an instruction torque (T ^* ) to be applied to the drive target ^. : Command torque setting means (21) for setting torque command value other than motor torque). In this case, for example, the addition angle calculation means operates to calculate the addition angle so that the torque detected by the torque detection means matches the indicated torque. As a result, the motor torque is controlled such that a torque (torque other than the motor torque) corresponding to the command torque is applied to the drive target. The motor torque corresponds to a load angle that is a deviation amount between the coordinate axis of the rotating coordinate system (dq coordinate system) according to the magnetic pole direction of the rotor and the virtual axis. The load angle is represented by the difference between the control angle and the rotor angle. Control of the motor torque is achieved by adjusting the load angle, and this adjustment of the load angle is achieved by controlling the addition angle.

  The motor control device further includes a current detection means (13) for detecting a current flowing in the stator winding of the motor, and the current driving means generates an instruction current that generates a current value to be passed through the virtual axis as an instruction current value. Depending on the value generation means (31), the detected current value detected by the current detection means, the indicated current value generated by the indicated current value generation means, and the control angle, the value is applied to the stator winding of the motor. It may include instruction voltage generation means (32, 33, 34A, 34B, 36A, 36B) for generating a power instruction voltage. The command current value generation unit may generate a command current value based on the torque detected by the torque detection unit, for example.

  In this case, the drive value of the motor includes, for example, an instruction current value, a detected current value, an instruction voltage value, and the like. When voltage detection means for detecting the voltage applied to the stator winding of the motor is provided, the drive value of the motor includes a detected voltage value detected by the voltage detection means. The angular velocity calculation means may calculate the angular velocity of the rotor at predetermined time intervals based on the detected current value and the command voltage value, or based on the detected current value and the detected voltage value, for example. The angular velocity of the rotor may be calculated every predetermined time interval.

  The determination means may determine, for example, whether the change amount of the indicated current value is equal to or greater than a predetermined value, or determine whether the change amount of the detected current value is equal to or greater than a predetermined value. You may do. Alternatively, the determination means monitors the amount of change in both the indicated current value and the detected current value, and when the amount of change in either one becomes equal to or greater than a predetermined value, the amount of change in the motor drive value is equal to or greater than the predetermined value. It may be determined that

For example, the addition angle correction unit may correct the addition angle so as to be a value within a predetermined range determined based on a final rotor angular velocity calculated by the angular velocity correction unit. Further, the addition angle correction means may include means for comparing the instruction torque and the detected torque and increasing or decreasing the addition angle according to the comparison result.
The control angle changes by the addition angle between calculation cycles. That is, the change in the control angle per calculation cycle is equal to the addition angle. Assuming that the angular velocity calculation means calculates the angular displacement of the rotor per calculation cycle as the rotor angular velocity, the load angle increases when the addition angle is larger than the rotor angular velocity. Therefore, when there is a positive correlation between the load angle and the motor torque, the motor torque increases as the load angle increases. Further, when there is a negative correlation between the load angle and the motor torque, the motor torque decreases as the load angle increases. Thus, there is a correlation between the load angle and the motor torque.

  When a certain torque is to be applied to the drive target as a whole (for example, when the insufficient torque is compensated for by the motor torque), the torque other than the motor torque applied to the drive target decreases as the motor torque increases. Therefore, the detected torque is reduced. On the other hand, if the motor torque decreases, the torque other than the motor torque applied to the drive target increases, so the detected torque increases. Therefore, if the magnitude relationship between the command torque and the detected torque and the magnitude relationship between the rotor angular velocity and the addition angle are appropriate, the detected torque can be brought close to the command torque. Therefore, the addition angle correction means corrects the addition angle so that the detected torque becomes a value within a predetermined range determined based on the rotor angular velocity according to the comparison result with the instruction torque.

  More specifically, when there is a positive correlation between the load angle and the motor torque, the addition angle correction means calculates the addition angle by the angular velocity correction means when the detected torque is larger than the command torque. When the detected torque is smaller than the indicated torque, the added angle is corrected to a value less than the final rotor angular speed calculated by the angular speed correcting means. preferable.

  When there is a positive correlation between the load angle and the motor torque, if the detected torque is greater than the command torque, the detected torque is reduced if the added angle is larger than the rotor angular displacement (rotor angular velocity) per calculation cycle. It is possible to approach the indicated torque. Therefore, the addition angle correction means corrects the addition angle to a value greater than or equal to the rotor angular velocity when the detected torque is larger than the command torque and the addition angle is smaller than the rotor angular velocity. When the detected torque is smaller than the command torque, the detected torque can be brought close to the command torque if the addition angle is smaller than the rotor angular velocity. Therefore, the addition angle correction means corrects the addition angle to a value equal to or less than the rotor angular velocity when the detected torque is smaller than the command torque and the addition angle is larger than the rotor angular velocity.

In this way, since the addition angle can be corrected to an appropriate value in accordance with the magnitude relationship between the detected torque and the command torque, it is possible to perform appropriate control so that the detected torque approaches the command torque. .
Also, when there is a positive correlation between the load angle and the motor torque, when the detected torque is larger than the command torque and the added angle is excessively larger than the rotor angular speed, the added angle converges to an appropriate value. take time. Further, when the detected torque is smaller than the command torque, if the added angle is excessively smaller than the rotor angular speed, it takes time to converge the added angle to an appropriate value. Therefore, when the detected torque is greater than the command torque, the addition angle correction means has a value equal to or less than a value larger than the final rotor angular speed calculated by the angular speed correction means by a predetermined change limit value. When the detected torque is smaller than the command torque, the added angle is corrected to a value equal to or larger than a value smaller than the final rotor angular velocity calculated by the angular velocity correcting means by a predetermined change limit value. It is preferable. As a result, the addition angle easily converges to an appropriate value, so that the control can be stabilized and the return to the normal state can be effectively promoted even when a control abnormality occurs.

  On the other hand, when there is a negative correlation between the load angle and the motor torque, the addition angle correction means, when the detected torque is smaller than the command torque, the final calculation result of the addition angle calculated by the angular velocity correction means. Preferably, the value is corrected to a value equal to or higher than the rotor angular velocity, and when the detected torque is larger than the command torque, the added angle is preferably corrected to a value equal to or smaller than the final rotor angular velocity calculated by the angular velocity correcting means.

  If there is a negative correlation between the load angle and the motor torque, if the detected torque is smaller than the command torque, the detected torque is commanded if the added angle is larger than the rotor angular displacement (rotor angular velocity) per calculation cycle. It can be close to torque. Therefore, the addition angle correction means corrects the addition angle to a value greater than or equal to the rotor angular velocity when the detected torque is smaller than the command torque and the addition angle is smaller than the rotor angular velocity. Further, when the detected torque is larger than the command torque, the detected torque can be brought close to the command torque if the addition angle is smaller than the rotor angular velocity. Accordingly, the addition angle correction means corrects the addition angle to a value equal to or less than the rotor angular velocity when the detected torque is larger than the command torque and the addition angle is larger than the rotor angular velocity.

In this way, since the addition angle can be corrected to an appropriate value in accordance with the magnitude relationship between the detected torque and the command torque, it is possible to perform appropriate control so that the detected torque approaches the command torque. .
In addition, when the load angle and the motor torque have a negative correlation, and the detected torque is smaller than the command torque, if the added angle is excessively larger than the rotor angular speed, the added angle converges to an appropriate value. take time. Further, when the detected torque is larger than the command torque, if the addition angle is excessively smaller than the rotor angular speed, it takes time to converge the addition angle to an appropriate value. Therefore, when the detected torque is smaller than the command torque, the addition angle correction means has a value equal to or less than a value larger than the final rotor angular speed calculated by the angular speed correction means by a predetermined change limit value. When the detected torque is larger than the command torque, the added angle is corrected to a value equal to or greater than a value smaller than the final rotor angular speed calculated by the angular speed correcting means by a predetermined change limit value. It is preferable. As a result, the addition angle easily converges to an appropriate value, so that the control can be stabilized and the return to the normal state can be effectively promoted even when a control abnormality occurs.

The motor control device may further include addition angle limiting means for limiting the addition angle with a predetermined limit value (ω _max ). By adding an appropriate limit to the addition angle, it is possible to suppress an excessive addition angle from being added to the control angle as compared to the actual rotation of the rotor. Thereby, a motor can be controlled appropriately.
The limit value may be a value determined by the following equation, for example. However, the “maximum rotor angular velocity” in the following equation is the maximum value of the rotor angular velocity in electrical angle.

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

The addition angle calculation means may include feedback control means (22, 23) for calculating the addition angle so that the detected torque approaches the command torque.
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 in accordance with a deviation between the instruction steering torque set by the instruction torque setting means and the steering torque detected by the torque detection means. .

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

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

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

1 is a block diagram for explaining an electrical configuration of an electric power steering device to which a motor control device according to an embodiment of the present invention is applied. FIG. It is an illustration figure for demonstrating the structure of a motor. It is a control block diagram of the electric power steering device. It is a figure which shows the example of a characteristic of the instruction | indication steering torque with respect to a steering angle. It is a figure for demonstrating the effect | action of a steering torque limiter. It is a figure which shows the example of a setting of (gamma) axis instruction | indication electric current value. It is a flowchart for demonstrating the effect | action of an addition angle limiter. It is a flowchart for demonstrating the function of an addition angle guard. It is a flowchart for demonstrating the function of an addition angle guard. It is a block diagram for demonstrating the structure of an induced voltage estimation part and a rotation angle estimation part. It is a block diagram for demonstrating the structure of a rotor angular velocity correction | amendment part. It is a flowchart for demonstrating the rotor angular velocity correction process by a rotor angular velocity correction | amendment part. It is a figure for demonstrating the function of a rotor angular velocity correction | amendment 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 assist force via a speed reduction mechanism 7 to the steering mechanism 2 of the vehicle. The motor 3 (brushless motor) that gives the power, the steering angle sensor 4 that detects the steering angle that is the rotation angle of the steering wheel 10, the motor control device 5 that drives and controls the motor 3, and the electric power steering device are mounted. And a vehicle speed sensor 6 for detecting the speed of the vehicle.

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

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

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

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

The current detection unit 13 uses phase currents I _U , I _V , I _W (hereinafter, collectively referred to as “three-phase detection current I _UVW ”) flowing through the stator windings 51, 52, 53 of each phase of the motor 3. To detect. These are current values in the coordinate axis directions in the UVW coordinate system.
The microcomputer 11 includes a CPU and a memory (such as a ROM and a RAM), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a steering torque limiter 20, an instruction steering torque setting unit 21, a torque deviation calculation unit 22, a PI (proportional integration) control unit 23, an addition angle limiter 24, and a control angle calculation unit. 26, induced voltage estimation unit 28, rotation angle estimation unit 29, rotor angular displacement calculation unit 30, command current value generation unit 31, current deviation calculation unit 32, PI control unit 33, and γδ / αβ conversion. 34A, αβ / UVW converter 34B, PWM (Pulse Width Modulation) controller 35, UVW / αβ converter 36A, αβ / γδ converter 36B, torque deviation monitoring unit 40, and addition angle guard 41 The rotor angular velocity correction unit 42 is included. The induced voltage estimation unit 28, the rotation angle estimation unit 29, and the rotor angular displacement calculation unit 30 constitute a speed estimation observer (angular velocity calculation means) 43 for estimating the angular velocity of the rotor 50.

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 a command steering torque T ^* set by the command steering torque setting unit 21 and a steering torque T detected by the torque sensor 1 and subjected to a limiting process by the steering torque limiter 20 (hereinafter, for distinction). A deviation (torque deviation) ΔT (= T ^* −T) from “detected steering torque T” is obtained. The PI control unit 23 performs a PI calculation on the torque deviation ΔT. That is, the torque deviation calculation unit 22 and the PI control unit 23 constitute torque feedback control means for guiding the detected steering torque T to the command steering torque T ^* . The PI control unit 23 calculates the addition angle α for the control angle θ _C by performing PI calculation for the torque deviation ΔT. Therefore, the torque feedback control means constitutes an addition angle calculation means for calculating the addition angle α.

More specifically, the PI control unit 23 includes a proportional element 23a, an integral element 23b, and an adder 23c. However, _{K P} is a proportional gain, _{K I} is an integral gain, 1 / s is an integration operator. The proportional element (proportional calculation value) of the proportional integral calculation is obtained by the proportional element 23a, and the integral term (integral calculation value) of the proportional integral calculation is obtained by the integral element 23b. These calculation results (proportional term and integral term) are added by the adder 23c, whereby the addition angle α is obtained.

The addition angle limiter 24 is addition angle limiting means for limiting the addition angle α obtained by the PI control unit 23. More specifically, the addition angle limiter 24 limits the addition angle α to a value between a predetermined upper limit value UL (positive value) and a lower limit value LL (negative value). The upper limit value UL and the lower limit value LL are determined based on a predetermined limit value ω _max (ω _max > 0, for example, ω _max = 45 degrees). The predetermined limit value ω _max is determined based on, for example, the maximum steering angular velocity. The maximum steering angular velocity is a maximum value that can be assumed as the steering angular velocity of the steering wheel 10 and is, for example, about 800 deg / sec.

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

Maximum value of rotor angle change = Maximum rotor angular speed x Calculation cycle
= Maximum steering angular velocity x reduction ratio x number of pole pairs x calculation cycle (3)
The rotor angle variation maximum value is the maximum variation of the control angle theta _C that is permitted within one calculation cycle. Therefore, the maximum value of the rotor angle change may be set to the limit value ω _max . Using the limit value ω _max , the upper limit value UL and the lower limit value LL of the addition angle α can be expressed by the following equations (4) and (5), respectively.

UL = + ω _max (4)
LL = −ω _max (5)
The addition angle α after the limit processing by the addition angle limiter 24 is added to the previous value θ _C (n−1) (n is the number of the current calculation cycle) of the control angle θ _C in the adder 26A of the control angle calculation unit 26. (Z- ¹ represents the previous value of the signal). However, the initial value of the control angle θ _C is a predetermined value (for example, zero).

The control angle calculation unit 26 includes an adder 26A that adds the addition angle α given from the addition angle limiter 24 to the previous value θ _C (n−1) of the control angle θ _C. That is, the control angle calculation unit 26 calculates the control angle θ _C every predetermined calculation cycle. Then, the control angle θ _C in the previous calculation cycle is set as the previous value θ _C (n−1), and the current value θ _C (n), which is the control angle θ _C in the current calculation cycle, is obtained.
The induced voltage estimation unit 28 estimates an induced voltage generated by the rotation of the motor 3. Then, the rotational angle estimation unit 29, based on the induced voltage estimated by the induced voltage estimation unit 28, and thereby calculates the estimated value of the rotation angle of the rotor 50 (the estimated rotation angle) theta _E. Specific examples of the induced voltage estimation unit 28 and the rotation angle estimation unit 29 will be described later.

The rotor angular displacement calculation unit 30, by determining the amount of change in the estimated rotational angle theta _E between calculation cycle to obtain the angular displacement Δθ of the rotor 50 in the calculation cycle (a value corresponding to the rotational angular velocity .omega.n). That is, the speed estimation observer 43 including the induced voltage estimation unit 28, the rotation angle estimation unit 29, and the rotor angular displacement calculation unit 30 has a rotation angular velocity ωn of the rotor 50 for each calculation cycle (the angle of the rotor 50 per calculation cycle). Displacement Δθ) is calculated. The rotational angular speed (hereinafter referred to as “rotor angular speed”) ωn of the rotor 50 calculated by the speed estimation observer 43 is used to correct the addition angle α.

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 αβ / γδ conversion unit 36B to the deviation calculation unit 32.

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 32. For the coordinate conversion in the αβ / γδ conversion unit 36B, 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 / 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 control angle θ _C calculated by the control angle calculation unit 26 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 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.
The torque deviation monitoring unit 40 determines the magnitude relationship between the command steering torque T ^* and the detected steering torque T by monitoring the sign of the torque deviation ΔT calculated by the torque deviation calculation unit 22. The determination result is given to the addition angle guard 41.

The rotor angular speed correction unit 42 corrects the rotor angular speed ωn (angular displacement Δθ of the rotor 50 per calculation period) calculated by the speed estimation observer 43. When the command current value (two-phase command current value I _γδ ^* ) generated by the command current value generation unit 31 changes suddenly, it has been found that the speed estimation accuracy of the speed estimation observer 43 temporarily decreases. Yes. Specifically, the sudden change in the command current value is caused by the change in the detected steering torque T, so that the γ-axis command current value I _γ ^* changes from the inner region to the outer region of the dead zone NR in FIG. This occurs when the region changes from the outer region to the inner region. More specifically, the γ-axis command current value I _γ ^* changes suddenly when the steering wheel 10 at the neutral position is steered or when the steering wheel 10 at a position other than the neutral position is returned to the neutral position. .

When the command current value I _γ ^* changes suddenly, the speed estimation accuracy of the speed estimation observer 43 decreases, so the rotor angular speed ωn calculated by the speed estimation observer 43 is used as it is for correcting the addition angle. Is not preferred. Therefore, when the command current value I _γ ^* changes suddenly, the rotor angular velocity correction unit 42 performs the required period (a constant or variable period), and the rotor calculated by the speed estimation observer 43 before the command current value suddenly changes. The final rotor angular speed ωF is calculated based on the angular speed and the rotor angular speed calculated by the speed estimation observer 43 after a sudden change in the command current value. A specific example of the rotor angular velocity correction unit 42 will be described later.

The addition angle guard 41 is for performing an addition angle guard process on the addition angle α generated by the PI control unit 23. In the addition angle guard process, when the addition angle α generated by the PI control unit 23 conflicts with the magnitude relationship between the command steering torque T ^* and the detected steering torque T, the addition angle α is set so as to eliminate this contradiction. Is a process of correcting the above. More specifically, the addition angle guard 41 is based on the final rotor angular velocity ωF (corresponding to the angular displacement of the rotor 50 per calculation period) calculated by the rotor angular velocity correction unit 42 when necessary. α is corrected.

FIG. 3 is a control block diagram of the electric power steering apparatus. However, for the sake of simplicity, the functions of the addition angle guard 41 and the addition angle limiter 24 are omitted.
Command steering torque T ^* and the deviation (torque deviation) of the detected steering torque T PI control for the [Delta] T (K _P is a proportionality coefficient, K _I is an integration coefficient, 1 / s is an integration operator.) By the addition angle α Is generated. It is obtained by adding the addition the addition angle alpha control angle theta previous value of _{C θ C (n-1)} , the current value of the control angle _{θ C θ C (n) =} θ C (n-1) + α is Desired. At this time, the deviation between the control angle θ _C and the actual rotor angle θ _M of the rotor 50 is the load angle θ _L = θ _C −θ _M.

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

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

In this way, an electric power steering apparatus that can appropriately control the motor 3 without using a rotation angle sensor and perform appropriate steering assistance can be realized. Thereby, a structure can be simplified and cost reduction can be aimed at.
In this embodiment, as the load angle theta _L is adjusted in a region having a load angle theta _L and the motor torque (assist torque) Tadashi Toga correlation, the addition angle α is controlled. Specifically, since the q-axis current I _q = I _γ sinθ _L , the addition angle α is controlled so that −90 ° ≦ θ _L ≦ 90 °. Of course, as the load angle theta _L in a region where the load angle theta _L and the motor torque (assist torque) has a negative correlation is adjusted, it is also possible to control the addition angle alpha. In this case, the addition angle α is controlled so that 90 ° ≦ θ _L ≦ 270 °. When the gain of the PI control unit 23 is positive, control is performed in a positive correlation region, and when the gain of the PI control unit 23 is negative, control is performed in a negative correlation region.

FIG. 7 is a flowchart for explaining the operation of the addition angle limiter 24. The addition angle limiter 24 compares the addition angle α generated by the PI control unit 23 and corrected by the addition angle guard 41 with the upper limit value UL (step S1), and when the addition angle α exceeds the upper limit value UL ( In 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 generated by the PI control unit 23 and corrected by the addition angle guard 41 is equal to or less than the upper limit value UL (step S1: NO), the addition angle limiter 24 further sets the addition angle α to 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.

If the addition angle α generated by the PI control unit 23 and corrected by the addition angle guard 41 is not less than the lower limit value LL and not more than the upper limit value UL (step S3: NO), the addition angle α is directly applied to the control angle θ _C. Used for addition.
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. 8A is a flowchart for explaining the addition angle guard process. However, as the load angle theta _L and the motor torque (assist torque) load angle theta _L in the area having a positive correlation transgressions are adjusted, the addition angle α is processing example is shown if you controlled.
The torque deviation monitoring unit 40 monitors the sign of the torque deviation ΔT calculated by the torque deviation calculation unit 22, and provides the addition angle guard 41 with information regarding the magnitude relationship between the command steering torque T ^* and the detected steering torque T. .

When the detected steering torque T is larger than the command steering torque T ^* (step S11: YES), the addition angle guard 41 is the final one in which the addition angle α obtained by the PI control unit 23 is calculated by the rotor angular velocity correction unit 42. It is determined whether it is smaller than the typical rotor angular velocity ωF (corresponding to the rotor angular displacement per calculation cycle) (step S12). If this determination is affirmed, the addition angle guard 41 substitutes the rotor angular velocity ωF for the addition angle α (step S13). That is, the addition angle α is corrected to the rotor angular speed ωF. If the addition angle α is greater than or equal to the rotor angular velocity ωF (step S12: NO), the addition angle guard 41 further sets the addition angle α to a predetermined change limit value A (A> 0 from the rotor angular velocity ωF, for example A = It is compared with a larger value (ωF + A) by 7 deg) (step S14). When the addition angle α is larger than the value (ωF + A) (step S14: YES), the addition angle guard 41 substitutes the value (ωF + A) for the addition angle α (step S15). If the addition angle α is equal to or smaller than the value (ωF + A) (step S14: NO), the addition angle α is not corrected.

On the other hand, when the detected steering torque T is smaller than the command steering torque T ^* (step S11: NO, step S16: YES), the addition angle guard 41 has the addition angle α obtained by the PI control unit 23 based on the rotor angular velocity ωF. Is also larger (step S17). If this determination is affirmative, the addition angle guard 41 substitutes the rotor angular velocity ωF for the addition angle α (step S13), and corrects the addition angle α to the rotor angular velocity ωF. If the addition angle α is equal to or less than the rotor angular velocity ωF (step S17: NO), the addition angle guard 41 further sets the addition angle α to a value (ωF−A) smaller than the rotor angular velocity ωF by the change limit value A. Compare (step S18). When the addition angle α is smaller than the value (ωF−A) (step S18: YES), the addition angle guard 41 substitutes the value (ωF−A) for the addition angle α (step S19). If the addition angle α is equal to or greater than the value (ωF−A) (step S18: NO), the addition angle α is not corrected.

Further, when the detected steering torque T is equal to the command steering torque T ^* (determinations in steps S11 and S16 are both negative), the addition angle α is not corrected.
The addition angle α is the amount of change in the control angle θ _C during the calculation cycle, and is equal to the angular displacement (corresponding to the rotation speed) per calculation cycle of the γδ coordinate axis. Therefore, the addition angle α is larger if the load angle theta _L than the rotor angular velocity ωF corresponding to the rotor angular displacement calculation cycle is increased, if smaller load angle theta _L is smaller than the addition angle α is rotor angular velocity ωF . When there is a positive correlation to the load angle theta _L and the motor torque (assist torque), the motor torque becomes larger the larger the load angle theta _L is smaller motor torque becomes smaller load angle theta _L is Become.

On the other hand, the case where the detected steering torque T is larger than the command steering torque T ^* is a state where the motor torque (assist torque) is insufficient. Therefore, in order to increase the motor torque by increasing the load angle theta _L. That is, if the addition angle α is equal to or greater than the rotor angular velocity ωF, the detected steering torque T can be brought close to the command steering torque T ^* . Therefore, in this embodiment, when the detected steering torque T is larger than the command steering torque T ^* by the processing of steps S11 to S13 in FIG. 8A, the addition angle guard processing is performed to limit the addition angle α to the rotor angular velocity ωF or more. Done. In other words, even if the detected steering torque T is larger than the command steering torque T ^* , if the addition angle α is less than the rotor angular velocity ωF, it does not match the purpose of the control and a contradiction occurs. For example, such a situation may occur depending on the responsiveness of the PI control unit 23. In such a case, the addition angle α is corrected to a value equal to or greater than the rotor angular velocity ωF (in this embodiment, a value equal to the rotor angular velocity ωF). Of course, the addition angle α may be corrected to a value larger than the rotor angular velocity ωF (for example, a value larger by a predetermined value (a value smaller than the change limit value A)).

Similarly, when the detected steering torque T is smaller than the instruction steering torque T ^* , the motor torque (assist torque) is excessive. Therefore, in order to reduce the motor torque, it is sufficient to reduce the load angle theta _L. That is, if the addition angle α is equal to or less than the rotor angular velocity ωF, the detected steering torque T can be brought close to the command steering torque T ^* . Therefore, in this embodiment, when the detected steering torque T is smaller than the command steering torque T ^* by the processing of steps S16, S17, and S13 in FIG. 8A, the addition angle guard that limits the addition angle α to the rotor angular velocity ωF or less. Processing is performed. In other words, even if the detected steering torque T is smaller than the command steering torque T ^* , if the addition angle α exceeds the rotor angular velocity ωF, it does not match the purpose of the control and a contradiction occurs. For example, such a situation may occur depending on the responsiveness of the PI control unit 23. Therefore, in such a case, the addition angle α is corrected to a value equal to or less than the rotor angular velocity ωF (in this embodiment, a value equal to the rotor angular velocity ωF). Of course, the addition angle α may be corrected to a value smaller than the rotor angular velocity ωF (for example, a value smaller by a predetermined value (a value smaller than the change limit value A)).

Further, in this embodiment, when the detected steering torque T is larger than the command steering torque T ^* (step S11: YES), when the addition angle α is larger than the value obtained by adding the change limit value A to the rotor angular velocity ωF ( Step S12: NO, Step S14: YES), the addition angle α is corrected to ωF + A (Step S15). This is because if the addition angle α is excessively larger than the rotor angular velocity ωF corresponding to the rotor angular displacement per calculation cycle, it takes time to converge the addition angle α to an appropriate value. When the detected torque T is smaller than the command torque T ^* (step S16: YES), if the addition angle α is smaller than the value obtained by subtracting the change limit value A from the rotor angular velocity ωF (step S17: NO) (Step S18: YES), the addition angle α is corrected to ωF-A (Step S19). This takes time to converge the addition angle to an appropriate value if the addition angle α is excessively smaller than the rotor angular velocity ωF corresponding to the rotor angular displacement per calculation cycle. By performing such correction, the addition angle α easily converges to an appropriate value, so that the control can be stabilized and the return to the normal state can be effectively promoted even when a control abnormality occurs. Can do.

8A, when the detected steering torque T is greater than the command steering torque T ^* , the addition angle α is limited to the range of ωF + A ≧ α ≧ ωF, and the detected steering torque T becomes the command steering torque T. When smaller than ^* , the addition angle α is limited to a range of ωF ≧ α ≧ ωF−A. Thus, the addition angle α can take a reasonable value according to the rotor angular velocity ωF.

As the load angle theta _L and the motor torque and (assist torque) is the load angle theta _L in the area having a negative correlation is adjusted, the example of the addition angle guard process when the addition angle α is controlled in FIG. 8B Show. In FIG. 8B, steps in which the same processing as that shown in FIG. 8A is performed are denoted by the same reference numerals as in FIG. 8A.
In the process shown in FIG. 8B, the process according to the magnitude relationship between the detected steering torque T and the command steering torque T ^* is opposite to the process in FIG. 8A. That is, when the detected steering torque T is smaller than the command steering torque T ^* (step S11A: YES), the addition angle guard 41 has an addition angle α that is greater than the final rotor angular velocity ωF calculated by the rotor angular velocity correction unit 42. Is also smaller (step S12). If this determination is affirmed, the addition angle guard 41 substitutes the rotor angular velocity ωF for the addition angle α (step S13). That is, the addition angle α is corrected to the rotor angular speed ωF. If the addition angle α is greater than or equal to the rotor angular velocity ωF (step S12: NO), the addition angle guard 41 further compares the addition angle α with a value (ωF + A) that is larger than the rotor angular velocity ωF by the change limit value A (ωF + A) ( Step S14). When the addition angle α is larger than the value (ωF + A) (step S14: YES), the addition angle guard 41 substitutes the value (ωF + A) for the addition angle α (step S15). If the addition angle α is equal to or smaller than the value (ωF + A) (step S14: NO), the addition angle α is not corrected.

On the other hand, when the detected steering torque T is larger than the command steering torque T ^* (step S11A: NO, step S16A: YES), the addition angle guard 41 determines whether or not the addition angle α is larger than the rotor angular velocity ωF ( Step S17). If this determination is affirmative, the addition angle guard 41 substitutes the rotor angular velocity ωF for the addition angle α (step S13), and corrects the addition angle α to the rotor angular velocity ωF. If the addition angle α is equal to or less than the rotor angular velocity ωF (step S17: NO), the addition angle guard 41 further sets the addition angle α to a value (ωF−A) smaller than the rotor angular velocity ωF by the change limit value A. Compare (step S18). When the addition angle α is smaller than the value (ωF−A) (step S18: YES), the addition angle guard 41 substitutes the value (ωF−A) for the addition angle α (step S19). If the addition angle α is equal to or greater than the value (ωF−A) (step S18: NO), the addition angle α is not corrected.

Further, when the detected steering torque T is equal to the command steering torque T ^* (the determinations in steps S11A and S16A are both negative), the addition angle α is not corrected.
If there is a negative correlation to the load angle theta _L and the motor torque (assist torque), the motor torque is decreased the greater the load angle theta _L is the load angle theta _L is familiar motor torque increases if smaller.

On the other hand, when the detected steering torque T is smaller than the command steering torque T ^* , the motor torque (assist torque) is excessive. Therefore, in order to reduce the motor torque by increasing the load angle theta _L. That is, if the addition angle α is equal to or greater than the rotor angular velocity ωF, the detected steering torque T can be brought close to the command steering torque T ^* . Therefore, in this embodiment, when the detected steering torque T is smaller than the instructed steering torque T ^* by the processing in steps S11A to S13 in FIG. 8B, the addition angle guard process for limiting the addition angle α to the rotor angular speed ωF or more is performed. Done. In other words, even if the detected steering torque T is smaller than the command steering torque T ^* , if the addition angle α is less than the rotor angular velocity ωF, it does not match the purpose of the control and a contradiction occurs. In such a case, the addition angle α is corrected to a value equal to or greater than the rotor angular velocity ωF (in this embodiment, a value equal to the rotor angular velocity ωF). Of course, the addition angle α may be corrected to a value larger than the rotor angular velocity ωF (for example, a value larger by a predetermined value (a value smaller than the change limit value A)).

Similarly, when the detected steering torque T is larger than the command steering torque T ^* , the motor torque (assist torque) is insufficient. Therefore, in order to increase the motor torque, it is sufficient to reduce the load angle theta _L. That is, if the addition angle α is equal to or less than the rotor angular velocity ωF, the detected steering torque T can be brought close to the command steering torque T ^* . Therefore, in this embodiment, the addition angle guard that limits the addition angle α to the rotor angular velocity ωF or less when the detected steering torque T is larger than the command steering torque T ^* by the processing of steps S16A, S17, and S13 in FIG. 8B. Processing is performed. In other words, even if the detected steering torque T is greater than the command steering torque T ^* , if the addition angle α exceeds the rotor angular velocity ωF, the control purpose is not met and a contradiction occurs. Therefore, in such a case, the addition angle α is corrected to a value equal to or less than the rotor angular velocity ωF (in this embodiment, a value equal to the rotor angular velocity ωF). Of course, the addition angle α may be corrected to a value smaller than the rotor angular velocity ωF (for example, a value smaller by a predetermined value (a value smaller than the change limit value A)).

Further, in the process of FIG. 8B, when the detected steering torque T is smaller than the command steering torque T ^* (step S11A: YES), when the addition angle α is larger than the value obtained by adding the change limit value A to the rotor angular velocity ωF. (Step S12: NO. Step S14: YES), the addition angle α is corrected to the speed ωF + A (step S15). This is because if the addition angle α is excessively larger than the rotor angular velocity ωF per calculation cycle, it takes time to converge the addition angle α to an appropriate value. When the detected torque T is larger than the command torque T ^* (step S16A: YES), if the addition angle α is smaller than the value obtained by subtracting the change limit value A from the rotor angular velocity ωF (step S17: NO) (Step S18: YES), the addition angle α is corrected to ωF-A (Step S19). This is because if the addition angle α is excessively smaller than the speed ωF corresponding to the rotor angular displacement per calculation cycle, it takes time to converge the addition angle to an appropriate value. By performing such correction, the addition angle α easily converges to an appropriate value, so that the control can be stabilized and the return to the normal state can be effectively promoted even when a control abnormality occurs. Can do.

By performing such processing, when the detected steering torque T is smaller than the commanded steering torque T ^* , the addition angle α is limited to the range of ωF + A ≧ α ≧ ωF, and the detected steering torque T becomes the commanded steering torque T ^*. Is larger, the addition angle α is limited to a range of ωF ≧ α ≧ ωF−A. Thus, the addition angle α can take a reasonable value according to the rotor angular velocity ωF.

FIG. 9 is a block diagram for explaining the configuration of the induced voltage estimation unit 28 and the rotation angle estimation unit 29. The induced voltage estimation unit 28 estimates the induced voltage of the motor 3 based on the two-phase detection current I _αβ and the two-phase command voltage V _αβ ^* . More specifically, the induced voltage estimation unit 28 has a form as a disturbance observer that estimates the induced voltage of the motor 3 as a disturbance based on a motor model that is a mathematical model of the motor 3. The motor model can be expressed as, for example, (R + pL) ⁻¹ . Here, R is an armature winding resistance, L is an αβ axis inductance, and p is a differential operator. It can be considered that the two-phase command voltage V _αβ ^* and the induced voltage E _αβ (α-axis induced voltage E _α and β-axis induced voltage E _β ) are applied to the motor 3.

The induced voltage estimation unit 28 receives the two-phase detection current I _αβ as an input and estimates a motor voltage, which is an inverse motor model (inverse model of the motor model) 65, a motor voltage estimated by the inverse motor model 65, and a two-phase indication voltage A voltage deviation calculation unit 66 for _obtaining a deviation from V _αβ ^* may be used. The voltage deviation calculator 66 obtains a disturbance with respect to the two-phase indicating voltage V _αβ ^* . As is apparent from FIG. 9, this disturbance is an estimated value E ^ _αβ (α-axis induced voltage corresponding to the induced voltage E _αβ. The estimated value E ^ _α and the β-axis induced voltage estimated value E ^ _β (hereinafter collectively referred to as “estimated induced voltage E ^ _αβ ”) The reverse motor model 65 is represented by R + pL, for example.

The induced voltage E _αβ can be expressed by the following equation (6). However, K _E is the induced voltage constant, the theta _M rotor angle, omega is the rotor rotational angular speed.

Therefore, if the estimated induced voltage E ^ _.alpha..beta is determined, according to the following equation (7), it is obtained estimated rotational angle theta _E. This calculation is performed by the rotation angle estimation unit 29.

FIG. 10 is a block diagram for explaining the configuration of the rotor angular velocity correction unit 42. The rotor angular velocity correction unit 42 includes an instruction current value monitoring unit 71, a pre-current sudden change estimated speed holding unit 72, a first multiplication unit 73, a second multiplication unit 74, and an addition unit 75.
The command current value monitoring unit 71 monitors the amount of change ΔI _γ ^* per calculation cycle of the γ-axis command current value I _γ ^* , and the estimated speed holding unit 72 before the sudden current change, the first multiplication unit 73, and the second multiplication. The unit 74 is controlled. The pre-current sudden change estimated speed holding unit 72, when the command current value monitoring unit 71 detects that the γ-axis command current value I _γ ^* has suddenly changed, the rotor angular speed calculated by the speed estimation observer 43 immediately before that. ωn is held as the pre-current sudden change estimated speed ω0. The first multiplication unit 73 multiplies the rotor angular velocity ωn calculated by the speed estimation observer 43 by a weighting coefficient ξ (0 ≦ ξ ≦ 1) controlled by the command current value monitoring unit 71. The second multiplying unit 74 multiplies the estimated speed before current sudden change ω0 held in the estimated speed holding part before sudden current change 72 by the weight (1-ξ). The adding unit 75 calculates the final rotor angular velocity ωF by adding the multiplication result of the first multiplication unit 73 and the multiplication result of the second multiplication unit 74. Note that the command current value monitoring unit 71, gamma ^{when *} -axis command current value I _gamma ^* change amount [Delta] I _gamma is equal to or greater than a predetermined threshold value Th, gamma ^{that *} -axis command current value I _gamma is suddenly changed Is detected.

In other words, the rotor angular velocity correction unit 42, the speed estimated rotor angular velocity calculated by the velocity estimation observer 43 just before the gamma -axis command current value I _gamma ^* suddenly changed .omega.0, ^{after *} gamma -axis command current value I _gamma is suddenly changed If the rotor angular velocity calculated by the observer 43 is ωn and the weighting coefficient is ξ, the final rotor angular velocity ωF is calculated based on the following equation (8).
ωF = ω0 · (1-ξ) + ωn · ξ (8)
The weighting coefficient ξ is normally set to 1. When it is detected that the γ-axis command current value I _γ ^* has suddenly changed, the weighting coefficient ξ is set to 0 and then gradually increased to 1.

FIG. 11 is a flowchart for explaining the rotor angular velocity correction processing by the rotor angular velocity correction unit 42. This rotor angular velocity correction process is repeated every calculation cycle. The initial value of the weighting coefficient ξ is 1.
First, it is determined whether or not a flag F for storing that correction processing based on a sudden change in the γ-axis command current value I _γ ^* is being executed is set (F = 1) (step S21). The initial value of this flag F is 0. When the flag F is not set (step S21: NO), it is determined whether or not the change amount ΔI _γ ^* per calculation cycle of the γ-axis command current value I _γ ^* is greater than or equal to a predetermined threshold Th. (Step S22). When the change amount ΔI _γ ^* is less than the threshold value Th (step S22: NO), the final rotor angular speed ωF is calculated based on the equation (8) (step S23). In this case, since the weight coefficient ξ is 1, ωF = ωn. That is, the rotor angular speed ωn calculated by the speed estimation observer 43 is output as it is as the final rotor angular speed ωF. When the process of step S23 is performed, the process in the current calculation cycle ends.

When it is determined in step S22 that the change amount ΔI _γ ^* per calculation cycle of the γ-axis command current value I _γ ^* is equal to or greater than the threshold value Th (step S22: YES), the γ-axis command current value is determined. It is determined that I _γ ^* has changed suddenly, and flag F is set (F = 1) (step S24). Further, the weight coefficient ξ is set to 0 (step S25). Further, the rotor angular speed ωn calculated by the speed estimation observer 43 before one calculation cycle is set as the pre-current sudden change estimated speed ω0 (step S26).

  Then, the final rotor angular velocity ωF is calculated based on the equation (8) (step S27). When the process proceeds from step S26 to S27, the weighting coefficient ξ is 0, so ωF = ω0. That is, when the process proceeds from step S26 to S27, the rotor angular speed ωn (estimated speed ω0 before sudden current change) calculated by the speed estimation observer 43 one calculation period before is used as the final rotor angular speed ωF.

  Thereafter, the weighting coefficient ξ is increased by a predetermined increment Δξ (0 <Δξ <1) (step S28). At this time, when the weighting coefficient ξ is increased by the increment Δξ and the weighting coefficient ξ exceeds 1, ξ = 1. Next, it is determined whether or not the weight coefficient ξ has reached 1 (step S29). If the weighting coefficient ξ has not reached 1 (step S29: NO), the processing in the current calculation cycle ends. On the other hand, if the weighting coefficient ξ has reached 1, after the flag F is reset (F = 0) (step S30), the processing in the current calculation cycle ends.

  If it is determined in step S21 that the flag F is set (step S21: YES), the process proceeds to step S27. In step S27, the final rotor angular velocity ωF is calculated based on the equation (8). When the process proceeds from step S21 to S27, since the weighting coefficient ξ is 0 <ξ <1, ωF is a value obtained by multiplying ωn by the weight ξ and ω0 by a weight (1-ξ). It is the sum of the calculated values.

Since the weight coefficient ξ is gradually increased to 1 as time passes, the weight ξ multiplied by ωn is gradually increased and the weight (1-ξ) multiplied by ω0 is gradually decreased. That is, when the γ-axis command current value I _γ ^* changes suddenly, immediately after that, the final rotor angular velocity ωF is set with a large weight on the rotor angular velocity ω0 calculated by the speed estimation observer 43 before the sudden change. After that, the weight of the rotor angular speed ωn calculated by the speed estimation observer 43 is gradually increased to obtain the final rotor angular speed ωF. In such a final calculation method of the rotor angular velocity ωF, the accuracy (estimation accuracy) of the rotor angular velocity ωn calculated by the speed estimation observer 43 temporarily deteriorates when the γ-axis command current value I _γ ^* changes suddenly. However, after that, it is suitable for gradually recovering. Therefore, the final rotor angular speed ωF calculated by the rotor angular speed correction unit 42 is more accurate than the rotor angular speed ωn calculated by the speed estimation observer 43.

For example, as shown in FIG. 12A, it is assumed that the rotor angular speed ωn calculated by the speed estimation observer 43 changes as indicated by a solid line because the γ-axis command current value I _γ ^* changes suddenly at time t1. That is, when the γ-axis command current value I _γ ^* changes suddenly, the speed estimation accuracy of the speed estimation observer 43 deteriorates, and the rotor angular speed ωn calculated by the speed estimation observer 43 becomes unreliable.

  In this case, the weighting coefficient ξ changes from 1 to 0 at time t1, as shown by a broken line L1 in FIG. 12B, and then gradually increases to 1 at time t2. That is, the weight coefficient ξ gradually increases from 0 to 1 over the period T. Accordingly, the final rotor angular speed ωF calculated by the rotor angular speed correction unit 42 is the rotor angular speed ωn calculated by the speed estimation observer 43 immediately before time t1, as shown by a broken line in FIG. And then gradually approaches the rotor angular speed ωn calculated by the speed estimation observer 43. At the time point t2, the final rotor angular speed ωF becomes equal to the rotor angular speed ωn calculated by the speed estimation observer 43.

In addition, based on the absolute value D of the difference between the first extreme value of the rotor angular velocity ωn after the γ-axis command current value I _γ ^* suddenly changes and the rotor angular velocity ω0 immediately before the sudden change, the increment per operation cycle of the weighting coefficient ξ Δξ may be variably controlled. That is, as the absolute value D increases, the increment Δξ per operation period of the weighting coefficient ξ is reduced so that the rotor angular speed correction period becomes longer. When the increment Δξ is made smaller than the specified value (increment Δξ when changing from 0 to 1 in the period T) according to the absolute value D, the weighting coefficient ξ is, for example, as shown by the broken line L2 in FIG. The rotor angular speed correction period becomes longer.

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 rotor angular velocity correction unit 42 monitors the command current value (γ-axis command current value I _γ ^* ), and is calculated by the speed estimation observer 43 when the command current value suddenly changes. The rotor angular velocity ωn is corrected. However, the rotor angular velocity correction unit 42, in addition to or instead of the above-described correction, detects the current value detected by the current detection unit 13 (flows through the stator windings 51, 52, 53 of each phase of the motor 3). The detected value of the phase current I _UVW or its coordinate conversion value I _αβ ) may be monitored, and the rotor angular speed ωn calculated by the speed estimation observer 43 may be corrected when the detected current value changes suddenly. The detected current value may change suddenly due to disturbance from the road surface, for example.

In the above-described embodiment, the configuration in which the motor 3 is driven exclusively by sensorless control without the rotation angle sensor has been described. However, the rotation angle sensor such as a resolver is provided, and when the rotation angle sensor fails, as described above. It is good also as a structure which performs a sensorless control. Thereby, since the drive of the motor 3 can be continued even when the rotation angle sensor fails, the steering assist can be continued.
In this case, when using the rotation angle sensor, the command current value generation unit 31 may generate the δ-axis command current value I _δ ^* according to the predetermined assist characteristic according to the steering torque and the vehicle speed.

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

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

  DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 3 ... Motor, 5 ... Motor control apparatus, 11 ... Microcomputer, 26 ... Control angle calculating part, 43 ... Observer for speed estimation, 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,
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;
An angular velocity calculating means for calculating the angular velocity of the rotor at predetermined time intervals based on the driving value of the motor;
Determination means for determining whether or not the amount of change in the drive value of the motor is equal to or greater than a predetermined value;
When the change amount of the drive value of the motor becomes equal to or greater than the predetermined value, the rotor angular velocity calculated by the angular velocity calculation means immediately before the change amount of the drive value becomes equal to or greater than the predetermined value, and the drive value Angular velocity correction means for calculating a final rotor angular speed in accordance with the rotor angular speed calculated by the angular speed calculation means after the change amount of
A motor control device comprising: an addition angle correction unit that corrects the addition angle based on a final rotor angular velocity calculated by the angular velocity correction unit. The angular velocity correction means sets the angular velocity of the rotor calculated by the angular velocity calculation means to ω0 immediately before the change amount of the drive value becomes equal to or greater than the predetermined value, and the change amount of the drive value becomes equal to or greater than the predetermined value. The final rotor angular velocity ωF is expressed by the following equation, where ωn is the rotor angular velocity calculated by the angular velocity calculating means, 0 is set when the driving value becomes a predetermined value or more, and ξ is a weight gradually increased to 1. The motor control device according to claim 1, wherein the calculation is based on (a).
ωF = ω0 · (1-ξ) + ωn · ξ (a) A motor for applying a driving force to the steering mechanism of the vehicle;
A vehicle steering apparatus, comprising: the motor control apparatus according to claim 1, which controls the motor.

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