Motor control device

Abstract

A motor control device (11) controls a motor (11) of a machine device (13). The motor control device (11) comprises: a command value calculation unit (31) for calculating a command value (I*) for controlling a motor (12); and a disturbance observer unit (33) for estimating, on the basis of the command value (I*) and the rotation information (ωm) of the motor (12), a disturbance (TId) applied to the machine device (13) and correcting the command value (I*) on the basis of the estimated disturbance (TId). The disturbance observer unit (33) has parameters (L1, β) to be adjusted for compensating the effect of the disturbance (TId) having a specific frequency to be suppressed. The parameters (L1, β) are adjusted so that a disturbance (TIast) applied to the machine device (13) after the effect of the disturbance (TId) is compensated has frequency characteristics corresponding to the anti-resonance characteristics of the machine device (13).

Description

[Technical Field]

[0001] The present invention relates to a motor control device. [Background technology]

[0002] Conventionally, electric power steering devices have been available. Electric power steering devices (hereinafter referred to as "EPS") assist steering of the steering wheel by applying torque from a motor to a steering mechanism. The EPS control device calculates a target current value according to the steering torque applied to the steering wheel, and controls the power supply to the motor based on the calculated target current value. This causes the motor to generate torque according to the steering torque.

[0003] In an EPS, vibrations caused by torque ripple in the motor or reducer are easily transmitted to the steering wheel. Therefore, torque differential control, such as that described in Patent Document 1, is performed. The control device calculates a torque differential value by differentiating the steering torque detected by the torque sensor, and corrects the target current value in accordance with the calculated torque differential value. This suppresses vibrations caused by torque ripple. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-224129 Summary of the Invention [Problem to be solved by the invention]

[0005] By performing torque differential control, it is certainly possible to suppress vibrations caused by torque ripple. However, torque differential control may not be able to suppress vibrations caused by torque ripple to the required level. For this reason, there is a need for a more appropriate method of suppressing vibrations caused by torque ripple. Furthermore, motors are used not only in electric power steering devices but also as drive sources for various mechanical devices. There is also a need to reduce vibrations caused by torque ripple in the motors of these mechanical devices. [Means for solving the problem]

[0006] A motor control device according to one aspect of the present disclosure controls a motor of a mechanical device. The motor control device includes a command value calculation unit configured to calculate a command value for controlling the motor, and a disturbance observer unit configured to estimate a disturbance acting on the mechanical device based on the command value and rotation information of the motor, and to correct the command value based on the estimated disturbance. The disturbance observer unit has parameters that are adjusted to compensate for the effect of the disturbance having a specific frequency to be suppressed. The disturbance acting on the mechanical device after the effect of the disturbance has been compensated is a compensated disturbance, and the parameters are adjusted so that the compensated disturbance has a frequency characteristic corresponding to the anti-resonance characteristic of the mechanical device. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of an embodiment of a motor control device. [Figure 2] FIG. 2 is a block diagram of the motor control device of FIG. 1. [Figure 3] 10 is a graph showing frequency characteristics of disturbances. DETAILED DESCRIPTION OF THE INVENTION

[0008] A motor control device 11 according to one embodiment will be described.

[0009] As shown in FIG. 1, a motor control device 11 controls a motor 12. The motor 12 generates torque for driving a mechanical device 13 on which the motor 12 is mounted. The motor 12 is, for example, a three-phase brushless motor. The motor 12 has a rotation angle sensor 12A. The rotation angle sensor 12A detects a rotation angle θ of the motor 12. The rotation angle θ of the motor 12 is rotation information of the motor 12.

[0010] The motor control device 11 includes a microcomputer 21, an inverter 22, and a current sensor 23.

[0011] The microcomputer 21, which is a processing circuit, has a command value calculation unit 31 and a feedback calculation unit 32. These calculation units are functional parts realized by the CPU (Central Processing Unit) of the microcomputer 21 executing a control program. The microcomputer 21 includes a memory for storing the control program. The memory includes computer-readable media such as RAM (Random Access Memory) and ROM (Read Only Memory). However, realizing each calculation unit by software is just one example, and at least some of the calculation units may be realized by hardware circuits such as logic circuits.

[0012] The command value calculation unit 31 calculates, for example, a state variable S sv Based on this, the current command value I * The feedback calculation unit 32 calculates the current command value I calculated by the command value calculation unit 31. * and the value of the current Im of the motor 12 detected by the current sensor 23. The feedback calculation unit 32 calculates the difference between the current command value I * and the value of the current Im of the motor 12.

[0013] The inverter 22 operates based on a drive signal generated by a feedback calculation unit 32. The inverter 22 has a plurality of switching elements. These switching elements are switched on and off based on the drive signal, thereby generating a current command value I * The power generated by the inverter 22 is supplied to the motor 12 via a power supply path formed by a bus bar or a cable. As a result, the motor 12 is driven in accordance with the current command value I * A torque corresponding to the

[0014] <Disturbance observer> As shown in the block diagram of Fig. 2, the motor control device 11 has a disturbance observer unit 33. The disturbance observer unit 33 detects a disturbance T applied to a plant P, which is a control target. ld and estimate the disturbance T ld Compensation for the effects of disturbances refers to reducing the effects of disturbances in the control of a system that is subject to disturbances, taking into account the characteristics of the disturbances. ld is a nonlinear torque. ld is, for example, the torque ripple of the motor 12. The torque ripple is a disturbance that occurs periodically in response to the rotation of the motor 12.

[0015] The control system of the motor 12 controls the state variable S of the mechanical device 13. sv Based on this, the current command value I * It is a feedback control system that determines the current command value I * As a result of the current being supplied from the inverter 22 to the motor 12 in accordance with the above, the motor 12 rotates at a predetermined angular velocity ω m Therefore, the current command value I * from the angular velocity ω of motor 12 m The angular velocity ω of the motor 12 is controlled by the feedback control system. m is rotation information of the motor 12. The plant P includes a mechanical device 13.

[0016] When the inertia number of the mechanical device 13 is "1" and the mechanical device 13 and the motor 12 are considered to be coupled via an elastic element, the controlled object can be considered as a two-inertia system in which two moments of inertia are coupled by an elastic element. In this case, the controlled object has frequency characteristics including one set of resonance characteristics and anti-resonance characteristics.

[0017] Furthermore, if the number of inertia of the mechanical device 13 is "2" and the mechanical device 13 and the motor 12 are considered to be connected via an elastic element, the controlled object can be considered to be a three-inertia system in which three moments of inertia are connected by elastic elements. In this case, the controlled object has frequency characteristics that include two sets of resonance characteristics and anti-resonance characteristics.

[0018] The disturbance observer 33 calculates the current command value I * and the output of the plant P. An example of the output of the plant P is the angular velocity ω m Angular velocity ω m is obtained by differentiating the rotation angle θ of the motor 12 detected by the rotation angle sensor 12A. * and the angular velocity ω of the motor 12 m Based on the disturbance T ld The disturbance observer 33 estimates the disturbance T ld The first correction value I to cancel out c1 Calculate the following.

[0019] The disturbance observer unit 33 has an estimator 33A, a multiplier 33B, and a subtractor 33C. The disturbance observer unit 33 may be configured by a hardware circuit such as a logic circuit. The disturbance observer unit 33 may also be called a disturbance observer circuit. The disturbance observer unit 33 may also be a functional part realized by the CPU of a computer executing a control program.

[0020] The estimator 33A has a nominal plant Pn, a first observer gain L1, and a second observer gain L2. The nominal plant Pn is a model that simulates the plant P that is the control target. The estimator 33A calculates the angular velocity ω of the motor 12, which is obtained as the output of the plant P, as shown in the following equation (1): m and the estimated angular velocity ω of the motor 12 obtained as the output of the nominal plant Pn. m The difference Δω from ^ is calculated. "^" indicates an estimated value.

[0021] Δω=ω m -ω m ^ …(1) The estimator 33A calculates the angular velocity ω of the motor 12 as shown in the following equation (2): m and the estimated angular velocity ω of the motor 12 m The estimated disturbance T is obtained by multiplying the difference Δω between ^ and the second observer gain L2. ld ^ Differential value dT ld Calculates ^.

[0022] dT ld ^=Δω·L2 …(2) The estimator 33A estimates the disturbance T ld ^ Differential value dT ld Disturbance T is estimated by integrating ^ ld The nominal plant Pn is calculated by subtracting the estimated disturbance T ld ^, a value obtained by multiplying the value of the difference Δω by the first observer gain L1, and the viscosity coefficient C of the motor 12 are used to calculate the angular velocity ω m The estimated value of ω m Calculates ^.

[0023] The multiplier 33B multiplies the estimated disturbance T calculated by the estimator 33A. ld ^ Differential value dT ld The first correction value I is obtained by multiplying ^ by the gain β. c1 The first correction value I c1 is the disturbance T ld This is the current value required to cancel out the vibration caused by the

[0024] The subtractor 33C subtracts the current command value I * to the first correction value I c1 By subtracting the disturbance T ld The current command value I * Calculate the following.

[0025] The disturbance observer 33 detects the disturbance T ld The disturbance T applied to the machine 13 after the effect of ld After compensation, the disturbance T last That's what they say.

[0026] Compensated disturbance T last is expressed by the following equation (3).

[0027] T last =T ld -β dT ld ^={Js 2 +(-L2·β)+L1·J)s+L2}·T ld / {Js 2 +(-L2·C+L1·J)s+L2}·Js …(3) where "J" is the inertia coefficient that models the moment of inertia of the mechanical device 13. "C" is the viscosity coefficient that models the friction of the mechanical device 13. "s" is the Laplace operator. "L1" is the first observer gain. "L2" is the second observer gain. "β" is the gain.

[0028] As shown in the graph in Figure 3, the compensated disturbance T last has a spike-like notch in its frequency characteristic. last has a frequency characteristic corresponding to the anti-resonance characteristic of the plant P.

[0029] The first observer gain L1 is expressed by the following equation (4).

[0030] L1=2·ω·α …(4) where "ω" is the frequency, and "α" is the first parameter.

[0031] The second observer gain L2 is expressed by the following equation (5).

[0032] L2=J·ω 2 …(5) Here, "J" is an inertia coefficient that models the moment of inertia of the mechanical device 13. "ω" is a frequency.

[0033] The gain β is expressed by the following equation (6).

[0034] β=α / ω·2·γ …(6) Here, "α" is the first parameter, "ω" is the frequency, and "γ" is the second parameter. The second parameter γ is a value equal to or less than "1" and can be set in increments of, for example, "0.1."

[0035] The value of the frequency ω is the disturbance T ld The disturbance to be suppressed, T, is set to the frequency ld The frequency of, for example, the disturbance T ld The center frequency of the notch at f c is.

[0036] In addition, by adjusting the value of the first observer gain L1, the disturbance T ld Notch width W n It is possible to adjust the value of the first observer gain L1 by adjusting the value of the first parameter α in equation (4).

[0037] In addition, by adjusting the value of the gain β, the disturbance T ld Notch depth D n It is possible to adjust the value of the gain β by adjusting the value of the second parameter γ in equation (6).

[0038] The first observer gain L1 and the gain β are set to a value that represents a disturbance T having a specific frequency to be suppressed. ldThe first observer gain L1 and the gain β are adjusted to suppress the vibration caused by the disturbance T ld The value of the first observer gain L1 and the value of the gain β are used to adjust the transmission ratio of the compensated disturbance T last is adjusted to have a frequency characteristic corresponding to the anti-resonance characteristic of the plant P. The compensated disturbance T last is input to the plant P, and a disturbance T with a specific frequency is suppressed. ld Theoretically, it is possible to make the amplitude of vibration of the mechanical device 13 caused by the above to be "0".

[0039] By substituting equations (4), (5), and (6) into equation (3), the following equation (7) is obtained.

[0040] T last ={s 2 +2·ω·α·(1-γ)·s+ω 2}·T ld / {s 2 +2·ω·α·s+ω 2}…(7) When the value of the second term in the curly brackets in the numerator of equation (7), "2·ω·α·(1-γ)·s", is "0", the disturbance T with a specific frequency that is to be suppressed is ld The transmission ratio of the disturbance T to the plant P is "0". Therefore, by setting the value of the second parameter γ to "1", the disturbance T having a specific frequency to be suppressed is ld In addition, by adjusting the value of the second parameter γ between "0 and 1" in increments of, for example, "0.1", it is possible to cancel out the vibration caused by the disturbance T ld It is possible to adjust the transmission ratio of the disturbance T with a specific frequency to be suppressed. The smaller the value of the second term in the curly brackets in the numerator of equation (7), "2·ω·α·(1-γ)·s", the more easily the disturbance T with a specific frequency to be suppressed is transmitted. ld The transmission ratio to the plant P becomes smaller.

[0041] Note that the second term in the curly brackets in the numerator of equation (7), "2 ω α (1-γ) s," corresponds to the second term in the curly brackets in the numerator of equation (3), "(-L2 β) + L1 J)s." Adjusting the value of the second parameter γ also means adjusting the value of the gain β.

[0042] <Effects of the embodiment> According to this embodiment, the following effects can be obtained.

[0043] (1) The disturbance observer 33 uses a nominal plant Pn, which is a model that simulates the plant P, to measure the disturbance T ld and estimate the estimated disturbance T ld Based on the current command value I * The disturbance observer 33 corrects the disturbance T ld By adjusting this parameter, the disturbance T having a specific frequency to be suppressed can be suppressed. ld The parameter is the post-compensation disturbance T last is adjusted to have a frequency characteristic corresponding to the anti-resonance characteristic of the plant P. The compensated disturbance T last is input to the plant P, the vibrations occurring in the plant P can be suppressed or cancelled.

[0044] (2) The disturbance observer 33 calculates the current command value I * and the angular velocity ω of motor 12 m The disturbance T applied to the mechanical device 13 based on ld Unlike when the rotation angle θ of the motor 12 is used, there is no need to calculate the midpoint of the motor 12. The midpoint of the motor 12 is the rotation angle θ of the motor 12 that corresponds to the reference operating state of the mechanical device 13. For this reason, the motor control device 11 does not need to have a function for calculating the midpoint of the motor 12.

[0045] (2) The disturbance observer unit 33 calculates the estimated disturbance T ld^ Differential value dT ld The current command value I is calculated by multiplying ^ by the gain β. * The first correction value I c1 Calculate the differential value dT ld Since it is only necessary to multiply ^ by the gain β, the first correction value I c1 can be easily calculated.

[0046] (3) Disturbance T ld The post-compensation disturbance T applied to the plant P after the effect of last has a transfer characteristic expressed by the following equation (A), which is based on the previous equation (3).

[0047] {Js 2 +(-L2·β)+L1·J)s+L2} / {Js 2 +(-L2·C+L1·J)s+L2}·Js …(A) When the value of the second term in the numerator of equation (A), "(-L2·β)+L1·J)s", is "0", the disturbance T to the plant P is ld Theoretically, the transmission rate of the disturbance T is "0". Therefore, the value of the gain β of the disturbance observer unit 33 is adjusted so that the value of the second term in the numerator of the formula (A) becomes "0" or a value close to "0". By adjusting the value of the gain β, the disturbance T can be more appropriately ld can be suppressed.

[0048] <Other embodiments> This embodiment may be modified as follows.

[0049] As shown by the two-dot chain line in Fig. 2, the disturbance observer unit 33 may have a disturbance feedback controller 33D and an adder 33E. The disturbance feedback controller 33D calculates the estimated disturbance T ld ^ Differential value dT ld ^ is taken in, and the estimated disturbance T ld ^ Differential value dT ld ^ Based on the second correction value I c2 The second correction value I c2is the estimated disturbance T ld The adder 33E is a current value corresponding to the disturbance ld The current command value I obtained after compensating for the influence of * The second correction value I c2 By adding * The feedback calculation unit 32 calculates the final current command value I * In this way, the value of the current supplied to the motor 12 is more quickly adjusted to the current command value I * Follow.

[0050] The mechanical device 13 may be an electric power steering device. The motor 12 is an assist motor. The assist motor generates an assist torque that is applied to a steering mechanism of the vehicle. The assist torque is a torque that assists the steering of the steering wheel. The steering mechanism includes a steering shaft connected to the steering wheel and a turning shaft that turns the steered wheels of the vehicle. The assist torque is applied to the steering shaft or the turning shaft. The command value calculation unit 31 calculates the steering torque T detected by the torque sensor. h The current command value I for the assist motor is * Calculate the steering torque T h is the torque applied to the steering wheel. Steering torque T h is the state variable S that indicates the steering state of the steering device. sv is.

[0051] The mechanical device 13 may be a steer-by-wire type steering device. The motor 12 is a reaction motor or a steering motor. The reaction motor generates a steering reaction torque that is applied to a steering shaft of the vehicle. The steering reaction torque is a torque in the opposite direction to the steering direction of the steering wheel. The command value calculation unit 31 calculates the steering torque T detected by a torque sensor. h The current command value I for the reaction motor is *The steering motor generates a steering torque for steering the steered wheels of the vehicle. Command value calculation unit 31 calculates a current command value I for the steering motor in accordance with the steering angle of the steering wheel. * The steering angle is calculated based on the rotation angle θ of the motor 12 detected by the rotation angle sensor 12A, for example. The steering torque T h and the steering angle is expressed by the state variable S sv is.

[0052] As shown by the two-dot chain line in FIG. 2, when the motor 12 is an assist motor or a reaction motor, the motor control device 11 may be configured as follows. That is, the motor control device 11 has a compensator 34 and a multiplier 35. The compensator 34 multiplies the steering torque T detected by the torque sensor by h The torque differential value is calculated by differentiating the torque, and the disturbance T ld The compensation amount dT to compensate for the effect of ca The multiplier 35 calculates the compensation amount dT ca The third correction value I is obtained by multiplying it by the gain β. c3 The third correction value I c3 is the current value. The subtractor 33C calculates the third correction value I c3 current command value I * This adds to the steering torque T h This improves the responsiveness of the motor torque to changes in the steering angle, resulting in a smoother steering feel. It also has the effect of suppressing disturbances such as reverse input vibrations from the steered wheels and brake vibrations that occur when braking.

[0053] When the mechanical device 13 is a steering device of a vehicle and the motor 12 is an assist motor or a reaction motor, the disturbance observer unit 33 may be configured as follows. That is, when vibrations caused by torque ripples of the motor 12 are unlikely to appear in the steering device, the disturbance observer unit 33 detects the disturbance T ldFor example, the vibration caused by the torque ripple is easily transmitted to the steering device when the vehicle speed is extremely low. For this reason, the disturbance observer unit 33 may be configured to stop the disturbance compensation control when the vehicle speed exceeds a vehicle speed threshold value. The speed threshold value is a criterion for determining whether the vehicle speed is extremely low. Furthermore, the vibration caused by the torque ripple is easily transmitted to the steering device when the angular velocity ω of the motor 12 is exceeded. m When the angular velocity ω is extremely low, it is easily transmitted to the steering device. m The disturbance compensation control may be stopped when the value of exceeds the angular velocity threshold. m This is the criterion for determining whether the angular velocity ω of the motor 12 is extremely low. m reflects the steering speed of the steering wheel.

[0054] The motor control device 11 may have a function to detect an abnormality in itself, the motor 12, or the mechanical device 13. In this case, the disturbance observer unit 33 may stop disturbance compensation control when an abnormality in the motor control device 11, the motor 12, or the mechanical device 13 is detected. It is pointless to execute compensation control when an abnormality in the motor control device 11, the motor 12, or the mechanical device 13 is detected.

[0055] The command value calculation unit 31 may be configured as follows: That is, the command value calculation unit 31 calculates a state variable S sv The torque command value is calculated based on the calculated torque command value, and the current command value I * The torque command value is the torque to be generated by the motor 12. In this case, the estimator 33A calculates the torque command value and the angular velocity ω of the motor 12, which is the output of the plant P. m The estimator 33A takes in the torque command value and the angular velocity ω of the motor 12. m Based on the estimated disturbance T ld ^ Differential value dT ld The multiplier 33B calculates the estimated disturbance Tld ^ Differential value dT ld The torque correction value is calculated by multiplying ^ by a predetermined gain. The torque correction value is a correction value for the torque command value. The subtractor 33C corrects the torque command value by subtracting the torque correction value from the torque command value. Even in this way, the disturbance T having a frequency to be suppressed is ld It is possible to compensate for the effect of

[0056] The disturbance observer unit 33 may be configured as follows: That is, the disturbance observer unit 33 calculates the difference between the rotation angle θ of the motor 12 obtained as the output of the plant P and the estimated rotation angle of the motor 12 obtained as the output of the nominal plant Pn, and calculates the disturbance T based on the calculated difference. ld The rotation angle θ of the motor 12 is rotation information of the motor 12.

[0057] The mechanical device 13 is not limited to a steering device of a vehicle. The mechanical device 13 may be, for example, a machine tool driven by a motor.

Claims

1. A motor control device for controlling a motor of a mechanical device, a command value calculation unit configured to calculate a command value for controlling the motor; a disturbance observer unit configured to estimate a disturbance acting on the mechanical device based on the command value and rotation information of the motor, and to correct the command value based on the estimated disturbance; the disturbance observer unit has a parameter that is adjusted to compensate for the effect of the disturbance having a specific frequency that is to be suppressed, the disturbance applied to the mechanical device after the effect of the disturbance has been compensated for is a compensated disturbance, A motor control device in which the parameters are adjusted so that the compensated disturbance has a frequency characteristic corresponding to an anti-resonance characteristic that appears in the control of the motor in the mechanical device.

2. The motor control device according to claim 1 , wherein the rotation information of the motor is an angular velocity of the motor.

3. The disturbance observer unit calculating a differential value of the disturbance based on the command value and the angular velocity of the motor; 3. The motor control device according to claim 2, wherein the first correction value for the command value is calculated by multiplying the calculated differential value of the disturbance by a gain.

4. When "J" is the inertia coefficient of the mechanical device, "C" is the viscosity coefficient of the mechanical device, "s" is the Laplace operator, "L1" is the first observer gain of the disturbance observer unit, "L2" is the second observer gain of the disturbance observer unit, and "β" is the gain, The compensated disturbance is expressed by the following equation (A): {Js ２ +(-L2・β)+L1・J)s+L2} / {Js ２ +(-L2・C+L1・J)s+L2}・Js …(A) and the value of the gain "β" is adjusted so that the value of the second term in the numerator of equation (A) is zero or as close to zero as possible.

5. The disturbance observer unit calculating a differential value of the disturbance based on the command value and the angular velocity of the motor; 5. The motor control device according to claim 2, wherein a second correction value for the command value is calculated based on the calculated differential value of the disturbance.

6. The mechanical device is configured to operate also by application of an external torque; The disturbance observer unit calculating a compensation amount for compensating for the influence of the disturbance in accordance with a differential value of a torque externally applied to the mechanical device; 6. The motor control device according to claim 1, wherein a third correction value for the command value is calculated based on the calculated compensation amount.

7. The mechanical device is a steering device of a vehicle, 7. The motor control device according to claim 1, wherein the motor generates torque that is applied to the steering device.

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