JP5273465B2 - Motor control device - Google Patents

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, it can be applied to control of a brushless motor used as a drive source of an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle. There is room for improvement. Specifically, a method using a sensing signal applied when the rotor is stopped and when rotating at a very low speed does not necessarily provide a satisfactory steering feeling when used for a brushless motor as a drive source of an electric power steering apparatus.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control apparatus that can control a motor by a new control method that does not use a rotation angle sensor.

In order to achieve the above object, the invention according to claim 1 is a motor control device (5) for controlling a motor (3) including a rotor (50) and a stator (55) facing the rotor. The first control means (21, 22, 23, 24, 26, 31, 30, 33, 34A, 34B, 35, 36A, 36B) for controlling the motor, and the second control for controlling the motor. Means (27, 28, 32, 30, 33, 34A, 34B, 35, 36A, 36B), a first mode in which the motor is controlled by the first control means, and the motor is controlled by the second control means. Switching means (40, 41, 42) for switching the control mode to and from the second mode, wherein the first control means has a rotating coordinate system according to a control angle (θ _C ) that is a control rotation angle. Axial current value (I _γ ^* ) And the current driving means (31, 30, 33, 34A, 34B, 35, 36A, 36B) for driving the motor, and the addition angle (α) is added to the previous value of the control angle at every predetermined calculation cycle. A control angle calculation means (26) for calculating the current value of the control angle, and a torque detection means (1) for detecting torque (T) other than the motor torque applied to the drive target driven by the motor, An instruction torque calculating means (21) for calculating an instruction torque (T ^* ) to be applied to the drive target, and an addition for calculating the addition angle based on the detected torque and the instruction torque detected by the torque detecting means Angle calculation means (22, 23), and the second control means is obtained by induced voltage estimation means (27) for estimating the induced voltage of the motor and the induced voltage estimation means. Rotation angle estimation means (28) for estimating the rotation angle of the rotor based on the constant induced voltage, and controls the motor based on the estimated rotation angle estimated by the rotation angle estimation means. Further includes a switching initial value setting means (44) that uses the detected torque detected by the torque detection means when the mode is switched from the second mode to the first mode as an initial instruction torque at the switching time. It is 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, either the first mode in which the motor control is performed by the first control unit or the second mode in which the motor control is performed by the second control unit is selected, and the motor is controlled in the selected control mode. The When the motor is controlled by the first control means, an axis of a rotational coordinate system (γδ coordinate system, hereinafter referred to as “virtual rotational coordinate system”, which is referred to as a “virtual rotational coordinate system” according to the control angle). While the motor is driven by a current value (hereinafter referred to as “virtual axis current value”), the control angle is updated by adding the addition angle every calculation cycle. Thus, the necessary torque can be generated by driving the motor with the virtual axis current value while updating the control angle, that is, while updating the coordinate axis (virtual axis) of the virtual rotation coordinate system. Thus, an appropriate torque can be generated from the motor without using a rotation angle sensor. The addition angle is calculated based on the detected torque and the instruction torque (for example, based on the deviation between the instruction torque and the detection torque). More specifically, the addition angle calculation means can be constituted by torque feedback control means for calculating the addition angle so that the detected torque approaches the command torque. As a result, torque other than the motor torque that acts on the drive target is guided to the instruction torque, and the intended control can be realized.

On the other hand, the second control means estimates the induced voltage of the motor, and estimates the rotation angle of the rotor from the estimated induced voltage. Then, the motor is driven by performing energization control on the motor based on the estimated rotation angle.
In order for the estimated induced voltage to have an appropriate value, it is necessary that the motor is rotating. Therefore, the motor control by the first control means is appropriate when the motor is stopped and when rotating at a very low speed. On the other hand, in a state where the estimated induced voltage has a reasonable value, that is, in a state where the motor is rotating at a certain speed or more, motor control by the second control means is appropriate. More specifically, for example, when a motor is used as a drive source of the electric power steering apparatus, the control feeling by the second control means may be superior to the control by the first control means. is there.

  Therefore, in the present invention, either the first control means (first mode) or the second control means (second mode) is selected according to the situation and applied for controlling the motor. Since the first control means changes the control angle in accordance with the command torque, when the second control means (second mode) is switched to the first control means (first mode), a sudden change in motor generated torque occurs. There is a fear. Therefore, in the present invention, the detected torque at the time of switching is used as the initial instruction torque. Thereby, the continuity of the motor generated torque can be ensured. Therefore, when the motor control device of the present invention is applied to, for example, an electric power steering device, it is possible to avoid a sense of incongruity associated with switching of the control means, so that a good steering feeling can be realized.

According to a second aspect of the present invention, the command torque used in the addition angle calculation means is gradually changed from the initial command torque set by the switching initial value setting means to the command torque calculated by the command torque calculation means. The motor control device according to claim 1, further comprising means (43).
According to this configuration, when the second control unit (second mode) is switched to the first control unit (first mode), the command torque used in the addition angle calculation unit is changed from the initial command torque to the command. The torque is gradually changed to the command torque calculated by the torque calculation means. Thereby, the fluctuation | variation of a motor generation torque can be made still slower. Therefore, for example, in an electric power steering apparatus, a better steering feeling can be obtained.

The invention according to claim 3 further includes a rotation angular velocity calculation means (29) for calculating a rotation angular velocity of the motor, wherein the switching means sets the control mode to the first mode in the low rotation angular velocity region, and performs high rotation. The motor control device according to claim 1 or 2, wherein the control mode is set to the second mode in the angular velocity region.
According to this configuration, the first control means (first mode) is selected in the low rotational angular velocity range, and the second control means (second mode) is selected in the high rotational angular velocity range. Thus, the first and second control means (first and second modes) can be switched appropriately, so that the motor can be driven more appropriately. Therefore, for example, an excellent steering feeling can be realized in the electric power steering apparatus.

  The motor may provide a driving force to the steering mechanism (2) of the vehicle. In this case, the torque detecting means may be torque detecting means (1) for detecting a steering torque applied to the operating member (10) operated for steering the vehicle, and the indicated torque setting means. The command steering torque setting means (21) for setting the command steering torque may be used. Therefore, the addition angle calculation means is detected by the instruction steering torque set by the instruction steering torque setting means (the instruction torque subjected to the gradual change processing when switching from the second mode to the first mode) and the torque detection means. The added angle is calculated according to the steering torque to be applied (for example, according to the deviation thereof).

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

  The motor control device further includes a steering angle detection means (4) for detecting a steering angle of the operation member, and the instruction 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 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 in the first mode. 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 the (gamma) axis instruction | indication current value in a 1st mode. It is a figure which shows the example of a setting of the q-axis command electric current value in 2nd mode. It is a block diagram for demonstrating the structure of the induced voltage estimation part validated in 2nd mode, and a rotation angle estimation part. It is a flowchart for demonstrating the operation | movement accompanying switching of a 1st and 2nd mode. It is a figure for demonstrating the gradual change process of a command steering torque.

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 an induced voltage estimation. Unit 27, rotation angle estimation unit 28, angular velocity calculation unit 29, first command current value generation unit 31, second command current value generation unit 32, current deviation calculation unit 30, PI control unit 33, γδ / αβ converter 34A, αβ / UVW converter 34B, PWM (Pulse Width Modulation) controller 35, UVW / αβ converter 36A, αβ / γδ converter 36B, switching controller 40, instructions A current value switching unit 41, an angle switching unit 42, a gradual change unit 43, and a switching initial value setting unit 44 are included.

The command steering torque setting unit 21 sets the command steering torque T ^* based on the steering angle detected by the steering angle sensor 4 and the vehicle speed detected by the vehicle speed sensor 6. For example, as shown in FIG. 4, 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. The detected steering torque T has a positive sign for the right steering torque and a negative sign for the left steering torque.

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 (> 0). 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 27 estimates the induced voltage generated by the rotation of the motor 3. Then, the rotation angle estimation unit 28 calculates an estimated value (estimated rotation angle) θ _E of the rotation angle of the rotor 50 based on the induced voltage estimated by the induced voltage estimation unit 27. Specific examples of the induced voltage estimation unit 27 and the rotation angle estimation unit 28 will be described later.

Angular velocity calculating section 29, by differentiating the estimated rotation angle theta _E time, we obtain the rotation angular velocity ω of the rotor 50.
The angle switching unit 42 selects one of the control angle θ _C obtained by the control angle calculation unit 26 and the estimated rotation angle θ _E obtained by the rotation angle estimation unit 28, and is used for coordinate conversion. and outputs as the transformation angle theta _S.

The first command current value generation unit 31 uses, as the command current value, a current value to be passed through the coordinate axis (virtual axis) of the γδ coordinate system that is a virtual rotation coordinate system corresponding to the control angle θ _C that is a control rotation angle. Is to be generated. Specifically, a γ-axis command current value I _γ ^* and a δ-axis command current value I _δ ^* (hereinafter referred to as “two-phase command current value I _γδ ^* ”) are generated. The 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 second command current value generation unit 32 generates a current value to be passed through the coordinate axes of the dq coordinate system as the command current value. Specifically, a d-axis command current value I _d ^* and a q-axis command current value I _q ^* (hereinafter, collectively referred to as “two-phase command current value I _dq ^* ”) are generated. The second command current value generation unit 32 sets the q-axis command current value I _q ^* to a significant value and sets the d-axis command current value I _d ^* to 0. More specifically, the second command current value generation unit 32 sets the second command current value I _q ^* to zero. The current value generation unit 32 sets the q-axis command current value I _q ^* based on the detected steering torque T detected by the torque sensor 1.

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

The command current value switching unit 41 includes a two-phase command current value I _γδ ^* generated by the first command current value generation unit 31 and a two-phase command current value I _dq ^* generated by the second command current value generation unit 32 ^. Are selected and supplied to the current deviation calculation unit 30.
The switching control unit 40 switches the control mode between the first mode and the second mode according to the rotational angular velocity ω obtained by the angular velocity calculating unit 29, and generates a mode switching command. In response to this mode switching command, switching in the command current value switching unit 41 and the angle switching unit 42 is executed. In the first mode, the command current value switching unit 41 selects and outputs the two-phase command current value I _γδ ^* generated by the first command current value generation unit 31, and the angle switching unit 42 is controlled by the control angle calculation unit 26. The control angle θ _C to be generated is selected and output. In the second mode, the command current value switching unit 41 selects and outputs the two-phase command current value I _dq ^* generated by the second command current value generation unit 32, and the angle switching unit 42 includes the rotation angle estimation unit 28. The estimated rotation angle θ _E to be generated is selected and output.

The switching command from the switching control unit 40 is also given to the switching initial value setting unit 44. The switching initial value setting unit 44 receives the switching command in response to the command when the mode switching command from the switching control unit 40 commands switching from the second mode to the first mode. The detected steering torque T at the time is set in the gradual change unit 43 as the initial instruction steering torque T ₀ . Gradually changing portion 43 is typically, while passing the command steering torque T ^* set by the command steering torque setting unit 21 to the torque deviation calculation unit 22, the initial command steering torque T ₀ from the switching換初life value setting unit 44 When set, the command steering torque T ^* given to the torque deviation calculation unit 22 is gradually changed from the initial command steering torque T ₀ to the set value by the command steering torque setting unit 21.

The current deviation calculation unit 30 calculates the two-phase detection current I _γδ (γ-axis detection current I _γ and δ-axis detection current I _δ ) for the instruction current value I _γδ ^* or I _dq ^* selected by the instruction current value switching unit 41. Calculate the deviation. Specifically, when the command current value switching unit 41 outputs the two-phase command current value I _γδ ^* , the current deviation calculation unit 30 determines the deviation I of the γ-axis detection current I _{γ from} the γ-axis command current value I _γ ^* . _γ ^* −I _γ and a deviation I _δ ^* −I _δ of the δ axis detection current I _δ with respect to the δ axis command current value I _δ ^* (= 0) are calculated. Further, when the command current value switching unit 41 outputs the two-phase command current value I _dq ^* , the current deviation calculation unit 30 deviates the γ-axis detection current I _{γ from} the d-axis command current value I _d ^* (= 0). I _d ^* −I _γ and a deviation I _q ^* −I _δ of the δ-axis detection current I _δ with respect to the q-axis command current value I _q ^* are calculated. The γ-axis detection current I _γ and the δ-axis detection current I _δ are supplied from the αβ / γδ conversion unit 36B to the current deviation calculation unit 30.

The UVW / αβ conversion unit 36A outputs the three-phase detection current I _UVW (the U-phase detection current I _U , the V-phase detection current I _V and the W-phase detection current I _W ) of the UVW coordinate system detected by the current detection unit 13. The two-phase detection currents I _α and I _β (hereinafter collectively referred to as “two-phase detection current I _αβ ”) in the αβ coordinate system, which is a phase-fixed coordinate system, are converted. As shown in FIG. 2, the αβ coordinate system defines the α axis and the β axis (in the example of FIG. 2, coaxial with the U axis) orthogonal to the rotation axis of the rotor 50 with the rotation center of the rotor 50 as the origin. It is a fixed coordinate system. The αβ / γδ conversion unit 36B converts the two-phase detection current I _αβ into two-phase detection currents I _γ and I _δ (collectively referred to as “two-phase detection current I _γδ ”) in the γδ coordinate system. These are supplied to the current deviation calculation unit 30. For the coordinate conversion in the αβ / γδ conversion unit 36B, the conversion angle θ _S selected by the angle switching unit 42 is used.

The PI control unit 33 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 30, so that the two-phase instruction voltage V _γδ ^* (γ-axis instruction voltage V _γ ^* and δ-axis instruction to be applied to the motor 3 is obtained. Voltage V _δ ^* ). This two-phase command voltage V _γδ ^* is _supplied to the γδ / αβ conversion unit 34A.
The γδ / αβ converter 34A converts the two-phase command voltage V _γδ ^* into a two-phase command voltage V _αβ ^* in the αβ coordinate system. For this coordinate conversion, the conversion angle θ _S selected by the angle switching unit 42 is used. The two-phase command voltage V _αβ ^* is composed of an α-axis command voltage V _α ^* and a β-axis command voltage V _β ^* . The αβ / UVW conversion unit 34B generates a three-phase instruction voltage V _UVW ^* by performing a coordinate conversion operation on the two-phase instruction voltage V _αβ ^* . The three-phase command voltage V _UVW ^* includes a U-phase command voltage V _U ^* , a V-phase command voltage V _V ^*, and a W-phase command voltage V _W ^* . The three-phase instruction voltage V _UVW ^* is given to the PWM control unit 35.

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

The current deviation calculation unit 30 and the PI control unit 33 constitute a current feedback control unit. By the function of the current feedback control means, the motor current flowing through the motor 3 is controlled so as to approach the two-phase command current value I _γδ ^* or the two-phase command current value I _dq ^* selected by the command current value switching unit 41. The
FIG. 3 is a control block diagram of the electric power steering apparatus in the first mode. However, for the sake of simplicity, the function of the addition angle limiter 24 is omitted.

Command steering torque T ^* and the 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.

Thus, in the first mode, it is possible to realize an electric power steering apparatus that can appropriately control the motor 3 without using a rotation angle sensor and perform appropriate steering assistance. Thereby, a structure can be simplified and cost reduction can be aimed at. FIG. 7 is a block diagram for explaining the configuration of the induced voltage estimation unit 27 and the rotation angle estimation unit 28 enabled in the second mode. The induced voltage estimation unit 27 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 27 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 27 receives the two-phase detection current I _αβ as an input and estimates an inverse motor model (inverse model of the motor model) 65 that estimates the motor voltage, and the motor voltage and the two-phase indication voltage estimated by the inverse motor model 65. A voltage deviation calculation unit 66 for _obtaining a deviation from V _αβ ^* may be used. The voltage deviation calculation unit 66 obtains a disturbance with respect to the two-phase instruction voltage V _αβ ^* . As is apparent from FIG. 7, 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 28.

In the second mode, a two-phase command current value I _dq ^* corresponding to the detected steering torque T is set, and feedback control is performed so that the current of the motor 3 converges to the two-phase command current value I _dq ^*. . Then, the estimated induced voltage E ^ _.alpha..beta is estimated rotational angle theta _E of the rotor 50 with a demand, using the estimated rotational angle theta _E, the coordinate conversion in the ?? / .alpha..beta conversion unit 34A and .alpha..beta / the ?? conversion unit 36B is Will be done. Thus, even in the second mode, it is possible to appropriately control the motor 3 without using the rotation angle sensor and perform appropriate steering assistance. Thereby, a structure can be simplified and cost reduction can be aimed at.

  The components that are activated in the first mode constitute first control means, and the components that are activated in the second mode constitute second control means. Specifically, the first control means includes a command steering torque setting unit 21, a torque deviation calculation unit 22, a PI control unit 23, an addition angle limiter 24, a control angle calculation unit 26, a first command current value generation unit 31, a current The deviation calculating unit 30, the PI control unit 33, the γδ / αβ conversion unit 34A, the αβ / UVW conversion unit 34B, the PWM control unit 35, the UVW / αβ conversion unit 36A, and the αβ / γδ conversion unit 36B are configured. The second control means includes an induced voltage estimation unit 27, a rotation angle estimation unit 28, a second command current value generation unit 32, a current deviation calculation unit 30, a PI control unit 33, a γδ / αβ conversion unit 34A, and αβ / UVW. The conversion unit 34B, the PWM control unit 35, the UVW / αβ conversion unit 36A, and the αβ / γδ conversion unit 36B are configured. That is, the first and second control means include a current deviation calculation unit 30, a PI control unit 33, a γδ / αβ conversion unit 34A, an αβ / UVW conversion unit 34B, a PWM control unit 35, a UVW / αβ conversion unit 36A, and an αβ. The / γδ converter 36B is shared.

FIG. 8 is a flowchart for explaining an operation associated with switching between the first and second modes. The switching control unit 40 compares the rotational angular velocity ω calculated by the angular velocity calculating unit 29 with a predetermined switching threshold ω _th (for example, ω _th = 200 deg / sec) (step S1). When the rotational angular velocity ω is less than the switching threshold ω _th (step S1: YES), the switching control unit 40 selects the first mode (step S2). That is, the command steering torque T ^* is the control angle theta _C updated every calculation cycle adjusting motors controlling the load angle theta _L so as to achieve (load angle adjustment method) is executed. On the other hand, switching control unit 40, when the rotational angular velocity omega is equal to or higher than the switching threshold omega _th is (step S1: NO), selects the second mode (step S3). In other words, so that the detected steering torque two-phase command current value corresponding to T I _qd ^* is achieved, based on the estimated rotation angle theta _E, the motor 3 is controlled. That is, the first mode is selected in the low rotational angular velocity region, and the second mode is selected in the high rotational angular velocity region.

Since it is difficult to estimate the induced voltage in the low rotational angular velocity region, the motor 3 can be appropriately controlled by selecting the first mode. On the other hand, since the induced voltage can be accurately estimated in the high rotational angular velocity region, excellent steering feeling can be realized by selecting the second mode.
When the first mode is selected (step S2), the switching換初phase value setting unit 44 sets the gradually changing portion 43 detects steering torque T at that time as a switching換初life steering torque T ₀ (step S4). In response to this, the gradual change unit 43 executes a gradual change process for gradually changing the command steering torque T ^* from the switching initial steering torque T ₀ to the set value by the command steering torque setting unit 21 (step S5). . Thereby, since a sudden change in the steering torque can be suppressed or prevented, the steering feeling at the time of mode switching can be improved.

FIG. 9 is a diagram for explaining the processing by the gradual change unit 43, and shows an example of the time change of the command steering torque T ^* . When switching from the second mode to the first mode occurs, the detected steering torque T at that time becomes the switching initial steering torque T ₀ . The example of FIG. 9 shows a case where the set value (target command steering torque) of the command steering torque setting unit 21 is lower than the switching initial steering torque T ₀ . Therefore, the gradual change unit 43 gradually decreases the command steering torque T ^* from the switching initial steering torque T ₀ to the set value of the command steering torque setting unit 21. Then, when the command steering torque T ^* becomes equal to the set value of the command steering torque setting unit 21, the gradual change unit 43 thereafter outputs the set value as the command steering torque T ^* as it is.

  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 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 the rotation angle sensor is used, the command current value switching unit 41 selects the two-phase command current value I _dq ^* generated by the second command current value generation unit 32, and the γδ / αβ conversion unit 34A and αβ The output of the rotation angle sensor may be used for coordinate conversion in the / γδ converter 36B.
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, 4 ... Steering angle sensor, 5 ... Motor control apparatus, 11 ... Microcomputer, 26 ... Control angle calculating part, 41 ... Indication electric current value switching part, 42 ... Angle switching part, 50 ... Rotor , 51, 52, 52 ... stator winding, 55 ... stator

Claims (3)

A motor control device for controlling a motor including a rotor and a stator facing the rotor,
First control means for controlling the motor;
Second control means for controlling the motor;
Switching means for switching a control mode between a first mode in which the motor is controlled by the first control means and a second mode in which the motor is controlled by the second control means;
The first control means includes a current driving means for driving the motor with an axial current value of a rotating coordinate system according to a control angle that is a control rotation angle, and an addition angle to a previous value of the control angle for each predetermined calculation cycle. Control angle calculating means for calculating the current value of the control angle by adding, torque detecting means for detecting torque other than motor torque applied to the driving object driven by the motor, and being added to the driving object Instruction torque calculation means for calculating power instruction torque, and addition angle calculation means for calculating the addition angle based on the detected torque detected by the torque detection means and the instruction torque,
The second control means includes induced voltage estimation means for estimating the induced voltage of the motor, and rotation angle estimation means for estimating the rotation angle of the rotor based on the estimated induced voltage obtained by the induced voltage estimation means. , And controlling the motor based on the estimated rotation angle estimated by the rotation angle estimation means,
A switching initial value setting means that uses a detected torque detected by the torque detecting means when the control mode is switched from the second mode to the first mode as an initial instruction torque at the switching time;
Motor control device.   The gradual change means for gradually changing the command torque used in the addition angle calculation means from the initial command torque set by the switching initial value setting means to the command torque calculated by the command torque calculation means. The motor control apparatus described. A rotation angular velocity calculating means for calculating a rotation angular velocity of the motor;
3. The motor control device according to claim 1, wherein the switching unit sets a control mode to the first mode in a low rotation angular velocity region and sets a control mode to the second mode in a high rotation angular velocity region. .

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