JP6871022B2 - Motor control system - Google Patents

Description

The present invention relates to a motor control system.

In recent years, for example, in order to drive a link constituting a robot arm with high accuracy, a servomotor has been adopted for a joint portion of the robot arm. Here, since the load member such as the link driven by the motor is connected to the motor via a low-rigidity member such as a gear, resonance occurs due to the inertia (moment of inertia) of the motor and the load member. Therefore, there is a problem that the control band cannot be expanded beyond the resonance frequency.

To solve such a problem, Patent Document 1 includes _{an encoder that detects the rotation angle θ M of the motor shaft and an encoder that detects the rotation angle θ L} of the output shaft fixed to the load member driven by the motor. The provided motor control system is disclosed. _{In Patent Document 1, a virtual rotation angle θ SRC} for self resonance cancellation control (SRC) is obtained based on the motor shaft rotation angle θ _M and the output shaft rotation angle θ _{L detected by the two encoders.} The generation is generated and the virtual rotation angle θ _SRC is fed back to suppress the occurrence of resonance.

Japanese Unexamined Patent Publication No. 2014-164498

The inventors have found the following problems with respect to the motor control system.
In the motor control system disclosed in Patent Document 1, _{since an encoder for detecting the output shaft rotation angle θ L} is provided, the configuration of the motor control system becomes large and the manufacturing cost increases. Further, the motor control system disclosed in Patent Document 1 cannot be applied to control the motor torque.

On the other hand, there is known a method of feedback-controlling the motor torque using the shaft torsional torque detected by the torque sensor without providing an encoder for detecting the _{output shaft rotation angle θ L.} However, the occurrence of the above-mentioned resonance cannot be suppressed by simply feeding back the shaft torsional torque detected by the torque sensor to control the motor torque.

The present invention has been made in view of such circumstances, and provides a motor control system capable of suppressing the occurrence of resonance while feedback-controlling the motor torque using the shaft torsional torque detected by the torque sensor. It is a thing.

The motor control system according to one aspect of the present invention is
With the motor
A torque sensor that detects the shaft torsional torque between the motor shaft of the motor and the output shaft fixed to the load member driven by the motor, and
A motor control unit that controls the motor torque of the motor is provided.
The motor control unit
It has a virtual torque generator that generates a virtual torque whose resonance is canceled out based on the shaft torsion torque detected by the torque sensor and the output motor torque.
The motor torque is controlled by feeding back the virtual torque.

In the motor control system according to one aspect of the present invention, a virtual torque whose resonance is canceled is generated based on the shaft torsion torque detected by the torque sensor and the output motor torque, and the virtual torque is fed back. Therefore, the motor torque is controlled. That is, since the virtual torque in which the resonance component of the shaft torsional torque detected by the torque sensor is reduced is used for the feedback control of the motor torque, the occurrence of resonance can be suppressed.

Even if the virtual torque is generated by weighting the shaft torsional torque detected by the torque sensor and the torque obtained by subtracting the shaft torsional torque from the output motor torque by a predetermined ratio and adding them together. Good. Such a configuration facilitates design.

The motor control unit further includes a low-pass filter into which the shaft torsional torque detected by the torque sensor is input and a high-pass filter in which the virtual torque is input, and outputs from the low-pass filter and the high-pass filter. The motor torque may be controlled by feeding back the generated torque signal. With such a configuration, the followability at a low frequency can be improved.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a motor control system capable of suppressing the occurrence of resonance while feedback-controlling the motor torque using the shaft torsional torque detected by the torque sensor.

It is a block diagram which shows the motor control system which concerns on 1st Embodiment. It is a control block diagram of the motor control system which concerns on 1st Embodiment. It is a control block diagram of the motor control system which concerns on the comparative example of 1st Embodiment. It is a detailed control block diagram of the motor control system which concerns on 1st Embodiment. It is a detailed control block diagram of the motor control system which concerns on 2nd Embodiment.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings have been simplified as appropriate.
The term "resonance is canceled" includes not only the case where the resonance is completely canceled but also the case where a part of the resonance remains.

(First Embodiment)
First, the motor control system according to the first embodiment will be described with reference to FIG.
FIG. 1 is a block diagram showing a motor control system according to the first embodiment. As shown in FIG. 1, the motor control system 1 according to the present embodiment includes a motor MT, a speed reducer RD, a motor shaft rotation angle sensor AS, a torque sensor TS, and a motor control unit MC. The link LN, which is a load member, is driven by the motor MT via the speed reducer RD.
The motor control system 1 according to the present embodiment is, for example, a servomotor control system provided at a joint portion of the robot arm in order to drive a link LN constituting the robot arm.

The motor MT is, for example, an AC (alternating current) servomotor. The motor MT is driven based on the control signal ctr output from the motor control unit MC. The control signal ctr is, for example, a PWM (Pulse Width Modulation) signal.
The motor MT internally includes a current sensor CS that detects three-phase AC currents (hereinafter referred to as motor currents) I _u , I _v , and I _{w flowing through the motor MT. The motor currents I u} , I _v , and I _w detected by the current sensor CS are fed back to the motor control unit MC.
Incidentally, in FIG. 1 also shows the torque i.e. the motor torque T _M acting on the motor shaft by the driving force by the motor MT is exhibited.

The speed reducer RD is, for example, a wave gear device, and is provided between the motor shaft of the motor MT and the output shaft fixed to the link LN. The speed reducer RD reduces the rotation speed of the motor shaft of the motor MT to 1 / r (r: reduction ratio) and transmits it to the output shaft fixed to the link LN.

The torque sensor TS detects the torsional torque T _S between the output shaft which is fixed to the motor shaft and the link LN of the motor MT. Torsional torque _{T S} is, for example, the product _{S · K strain} of stiffness coefficient _{K strain} of the strain amount S and the distortion measuring unit measured by the strain gauge torque sensor TS. Torsional torque T _S that is detected by the torque sensor TS is input to the motor control unit MC.

The torque sensor TS is not limited to the strain gauge type, and may be any type such as a thin film type or a magnetostrictive type. _{Further, in FIG. 1, the load torque TL} acting on the output shaft due to disturbance such as the link LN coming into contact with an external object and the rotation angle of the output shaft fixed to the link LN, that is, the output shaft rotation angle θ _L are also shown. It is shown.

The motor shaft rotation angle sensor AS is an encoder that detects the rotation angle of the motor shaft of the motor MT, that is, the rotation angle θ _{M of the motor shaft. The motor shaft rotation angle θ M} detected by the motor shaft rotation angle sensor AS is input to the motor control unit MC.

The motor control unit MC is torsional torque target value T _S ^ref acquired from the host controller (not ^shown), the motor current I _u detected by the current sensor _CS, I v, _{I w,} which is detected by the torque sensor TS torsional torque T _S, and based on the motor shaft rotation angle theta _M detected by the motor shaft rotation angle sensor AS, controls the motor MT.

Although not shown in FIG. 1, the motor control unit MC includes, for example, a calculation unit such as a CPU (Central Processing Unit), a RAM (Random Access Memory) in which various control programs and data are stored, and a ROM (Read Only Memory). It is equipped with a storage unit such as.

Furthermore, the motor controller MC includes a torsional torque _{T S} that is detected by the torque sensor TS, based on the motor torque _{T M,} the self-resonance cancellation control (SRC: Self Resonance Cancellation Control) for the SRC virtual torque _{T SRC} Is generated and the SRC virtual torque T _SRC is fed back to suppress the occurrence of resonance.
The motor torque T _M for generating SRC virtual torque T _SRC, may be used a torque command value generated by the motor controller MC. Alternatively, as the motor torque _{T M,} the motor current detected by the current sensor CS _{I u,} I v, it may be used the measured value obtained from _{I w.}

Referring now to FIG. 2, it will be described in detail feedback control of the motor torque T _M by the motor control unit MC. FIG. 2 is a control block diagram of the motor control system according to the first embodiment. In FIG. 2, s means derivative and 1 / s means integral. For simplification, the gear ratio r is omitted in FIG. In other words, FIG. 2 shows the case where the gear ratio r = 1.

As shown in FIG. 2, the motor control system according to the present embodiment, a torque sensor showing the product of the twist angle and the torsional rigidity K between the motor MT and the link LN as torsional torque T _S, in Figure 1 Detected by TS. In the example of FIG. 2, the twist angle is the difference theta _M - [theta] _L of the motor shaft rotation angle theta _M and the output shaft rotation angle theta _L. It should be noted that, in consideration of the gear ratio r, the twist angle is θ _M -r · θ _L.

As shown in FIG. 2, the motor shaft of the motor MT, _T M -T _S from the motor torque _{T M} obtained by subtracting the torsional torque _{T S} acts. Therefore, the equation of motion of the rotation of the motor MT from 2, the moment of inertia J _M of the motor _MT, by using the viscous friction coefficient B _M, can be expressed by the following equation (1).

Further, as shown in FIG. 2, the output shaft fixed to the link LN, it was added torsional torque T _S to the load torque T _L T _{L +} T _S acts. Therefore, from FIG. 2, the equation of motion of rotation in the link LN can be expressed by the following equation (2) using the _{moment of inertia J L} of the link LN and the viscous friction coefficient _BL.

As shown in FIG. 2, the motor control unit MC includes an SRC virtual torque generation unit 11 and a compensator 12.
SRC virtual torque generating unit 11, based on the torsional torque _{T S} that is detected by the torque sensor TS, a command value of the motor torque _{T M} output from the compensator 12 to generate the SRC virtual torque _{T SRC.} This SRC virtual torque T _SRC is a virtual torque in which resonance is offset. In other words, SRC virtual torque T _SRC, using the motor torque T _M containing little resonance component is the virtual torque signal with reduced resonance component of torsional torque T _S that is detected by the torque sensor TS .. Incidentally, as the motor torque _{T M} is input to the SRC virtual torque generator 11, the motor current detected by the current sensor CS _{I u,} I v, it may be used the measured value obtained from _{I w.}

The compensator 12, signal _T ^S ref _{-T SRC} obtained by subtracting the SRC virtual torque _{T SRC} from torsional torque target value _T ^{S ref} is input. Compensator 12 generates a command value of the motor torque _{T M} from the input signal _T ^S ref _{-T SRC.} The motor MT is driven, the command value of the motor torque T _M output from the compensator 12 is fed back to the SRC virtual torque generating unit 11 based on the command value of the motor torque T _M output from the compensator 12 ..

Here, FIG. 3 is a control block diagram of the motor control system according to the comparative example of the first embodiment. As shown in FIG. 3, in the motor control system according to the comparative example, by feeding back the torsional torque T _S that is detected by the torque sensor TS in the motor controller MC, and controls the motor torque T _M.

However, in the motor control system according to the comparative example, the motor control unit MC does not include the SRC virtual torque generation unit 11 that generates _{the SRC virtual torque T SRC.} Then, the compensator 12, signal _T ^S ref -T _S that simply subtracting the torsional torque _{T S} from torsional torque target value _T ^{S ref} is input. Compensator 12 generates a command value of the motor torque _{T M} from the signal _T ^S ref -T _S entered. Thus, in the motor control system according to the comparative example, the feedback control of the motor torque T _M, since the accept the torsional torque T _S including the resonance component, can not be suppressed the occurrence of resonance.

In contrast, in the motor control system according to the present embodiment, as shown in FIG. 2, the motor controller MC includes a torsional torque T _S that is detected by the torque sensor TS, based on the motor torque T _M, The SRC virtual torque generation unit 11 for generating the SRC virtual torque T _{SRC whose resonances are offset is provided.} Then, the feedback control of the motor torque T _M, due to the use of SRC virtual torque T _SRC with reduced resonance component of torsional torque T _S that is detected by the torque sensor TS, is possible to suppress the occurrence of resonance it can. That is, while the feedback control of the motor torque T _M with torsional torque T _S that is detected by the torque sensor TS, it is possible to suppress the occurrence of resonance. As a result, the control band can be expanded.

Next, with reference to FIG. 4, a detailed configuration of the motor control unit MC in the motor control system according to the present embodiment will be described. FIG. 4 is a detailed control block diagram of the motor control system according to the first embodiment. In FIG. 4, the configuration of the SRC virtual torque generation unit 11 is shown in more detail as compared with FIG. As shown in FIG. 4, the SRC virtual torque generation unit 11 according to the present embodiment includes weight multipliers 111 and 112.

Weight multiplier 111, a multiplier for multiplying the weight coefficient α on the torque T _S that acts on the output shaft fixed to the link LN. _{Here, the load torque TL} acting on the output shaft due to the disturbance is ignored. On the other hand, weight multiplier 112, a multiplier for multiplying the weighting factor 1-alpha in the torque _T M -T _S that acts on the motor shaft of the motor MT. And alpha · _{T S} outputted from the weight multiplier 111, and is outputted from the weight multiplier _{112 (1-α) (T} M -T S), by adding the, SRC virtual torque _{T SRC} is generated To torque.

That is, the SRC virtual torque T _SRC can be expressed by the following equation (3).

Thus, in determining the SRC virtual torque _{T SRC,} of the _{T S} that acts on the output shaft fixed to the link LN, weighting coefficient the ratio of _T M -T _S that acts on the motor shaft of the motor MT alpha Design is easy because it can be determined directly by the value. Further, in the motor control system according to the present embodiment, the parameter to be set by the designer is only one of the weighting coefficient α.

Here, the value of the weighting coefficient α is 0 ≦ α <0.5 or 0.5 <α <1.
For alpha = _0.5, it contains no _T SRC = _{T M} becomes, SRC virtual torque _{T SRC} is torsional torque _{T S} that is detected by the torque sensor TS, alpha = 0.5 is excluded. Further, when α = 0.5, the resonance component is completely removed, so that the resonance cannot be suppressed. On the other hand, α = 0.5 from which the resonance component is completely removed serves as a reference when determining the value of the weighting coefficient α.
For alpha = 1, since the same manner _T SRC = _{T S} and the comparative example illustrated in FIG. 3, alpha = 1 is excluded. In this case, since the resonance component of the torsional torque T _S is not removed at all, it is impossible to suppress the resonance.

Specifically, the value of the weighting coefficient α is preferably a value slightly smaller than 0.5 in which the resonance component is completely removed. Finally, the magnitude and resonance frequency of the resonance are confirmed using the Nyquist diagram and Bode diagram, and the settling time and the magnitude of the overshoot are confirmed using the graph of the step response, and the value of the weighting coefficient α is confirmed. To determine. Further, the larger the value of the weighting coefficient α, the better the followability, but the more likely it is to become unstable.

(Second Embodiment)
Next, with reference to FIG. 5, a detailed configuration of the motor control unit MC in the motor control system according to the second embodiment will be described. Also in the motor control system according to the second embodiment, FIG. 1 is common to the first embodiment. FIG. 5 is a detailed control block diagram of the motor control system according to the second embodiment. The motor control unit MC according to the second embodiment shown in FIG. 5 includes a low-pass filter LPF and a high-pass filter HPF in addition to the SRC virtual torque generation unit 11 and the compensator 12 shown in FIG.

It is preferable that _{the cutoff frequency ω c} of the low-pass filter LPF and the high-pass filter HPF is common. The cutoff frequency ω _c is a frequency lower than the resonance frequency. Specifically, the cutoff frequency ω _c is preferably a frequency slightly lower than the resonance frequency.

As shown in FIG. 5, the low pass filter LPF, the torsional torque T _S that is detected by the torque sensor TS is inputted. On the other hand, the SRC virtual torque T _SRC output from the SRC virtual torque generation unit 11 is input to the high-pass filter HPF. _{Then, the feedback torque T FB,} which is the sum of the torque signal output from the low-pass filter LPF and the torque signal output from the high-pass filter HPF, is fed back.

That is, the feedback torque T _FB can be expressed by the following equation (4).

_{Further, by substituting the equation (3) into the SRC virtual torque T SRC} in the equation (4), the following equation (5) is obtained.

Here, in the motor control unit MC according to the first embodiment shown in FIG. 4, the SRC virtual torque T _SRC whose resonance is canceled at all frequencies is fed back.
On the other hand, in the motor control unit MC according to the second embodiment shown in FIG. 5, the SRC virtual torque T _SRC is fed back at a _{frequency higher than the cutoff frequency ω c where resonance can occur.} On the other hand, at frequencies below the cutoff frequency omega _c resonance can not occur, the torsional torque T _S that is detected by the torque sensor TS is fed back.

With such a configuration, the motor control system according to the present embodiment is superior in followability at a frequency lower _{than the cutoff frequency ω c, as compared with the motor control system according to the first embodiment.}
Further, in the motor control system according to the present embodiment, the designer should set only two _{parameters, the weighting coefficient α and the cutoff frequency ω c.}

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.
For example, the motor is not limited to an electric motor, but may be a pressure motor such as a hydraulic motor or any other motor.

1 Motor control system 11 Virtual torque generator 12 Compensator 111 Multiplier 112 Multiplier AS Motor shaft rotation angle sensor CS Current sensor HPF High-pass filter LN link LPF Low-pass filter MC Motor control MT Motor T _FB Feedback torque _TL Load torque T _M Motor Torque T _S Shaft Torque Torque TS Torque Sensor T _SRC SRC Virtual Torque T _S ^ref Shaft Torque Torque Target Value

Claims (2)

With the motor
A torque sensor that detects the shaft torsional torque between the motor shaft of the motor and the output shaft fixed to the load member driven by the motor, and
A motor control unit that controls the motor torque of the motor is provided.
The motor control unit
It has a virtual torque generator that generates a virtual torque whose resonance is canceled out based on the shaft torsion torque detected by the torque sensor and the output motor torque.
From feeding back the virtual torque, it controls the motor torque,
The virtual torque generator
The virtual torque is generated by weighting the shaft torsional torque detected by the torque sensor and the torque obtained by subtracting the shaft torsional torque from the output motor torque by a predetermined ratio and adding them together.
Motor control system. With the motor
A torque sensor that detects the shaft torsional torque between the motor shaft of the motor and the output shaft fixed to the load member driven by the motor, and
A motor control unit that controls the motor torque of the motor is provided.
The motor control unit
It has a virtual torque generator that generates a virtual torque whose resonance is canceled out based on the shaft torsion torque detected by the torque sensor and the output motor torque.
From feeding back the virtual torque, it controls the motor torque,
The motor control unit
A low-pass filter into which the shaft torsional torque detected by the torque sensor is input, and
It further has a high-pass filter into which the virtual torque is input.
The motor torque is controlled by feeding back the torque signals output from the low-pass filter and the high-pass filter.
Motor control system.

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