JPS6039397A - Controller for motor - Google Patents

Abstract

PURPOSE:To suppress the twisting vibration due to torque ripple by associating a notch filter having a gain characteristic reverse to the gain characteristic near a resonance point due to a machine system in a speed control loop. CONSTITUTION:A notch filter circuit is composed of resistance values of variable resistors VR1, VR2, VR3 and capacitors C1, C2, C3 of equal capacity so that the central frequency of the notch filter coincides with the resonance frequency of a machine system. The notch filter (transfer function KF) having such caracteristics is associated between a speed regulator AN (S) of a speed loop and a torque converter KT, thereby suppressing the twisting vibration due to the torque ripple in a frequency band near the resonance point of a speed control loop.

Description

[Detailed description of the invention] The present invention relates to a control device for an electric motor.

Recently, with the progress of transistor inverter technology, maintenance-free, robust, and inexpensive induction motors with AC servo drives, that is, AC servo motors, have become widespread and are replacing conventional DCC morphs. This ACC servo motor, also known as
As it is called a "different liquid type drive motor", it has torque ripples of various frequencies. An AC servo motor drive system in which these A and C servo motors are connected to a mating machine forms a torsional vibration system, and the aforementioned motor torque ripple occurs in the frequency band near the resonance peak of this torsional vibration system. If this happens, this torque ripple will increase abnormally, vibration noise will increase, and stable and quiet operation will not be possible.

FIG. 1 is a schematic configuration diagram of such an ACC servo drive system. 1 is an ACC servo motor 2 is a control device that drives the ACC servo morph; 3 is a three-phase AC power supply input to the control device 2; and 4 is a mating machine connected to and driven by the AC servo motor 1 through A6. FIG. 2 is a block diagram of the speed control loop of the A and C servo drive systems of FIG. δref is the rotation speed command signal, A
N(S) is the transfer function of the speed regulator 3IT is the torque component current, 1 (T is the transfer function of the torque converter, τ is the torque, △ is the disturbance torque, KM is the mechanical system (rotor of motor 1, cup (composed of a ring 6 and a mating machine 5).

δ is the rotational speed signal, and KN is the transfer function of the resolver 4. Now, the rotating chamber of the AC servo motor is modeled, and the block diagram of the speed control loop is shown in Figure 4 (1), and its gain characteristics have a resonance peak at frequency fn, as shown in Figure 5 (1). have. Therefore, the control became unstable, and when there was a torque ripple at 2Δf near the resonance point of the bracket, large torsional vibrations occurred. However, as shown in FIG. 3(2), conventionally, the torsional rigidity k of the coupling 6 was assumed to be infinite, that is, the rotor of the motor 1 and the mating machine 5 were connected as a rigid body. In this case, the speed control loop is shown in Figure 4 (2), and the gain characteristic is shown in Figure 5.
The result is as shown in Figure (2).

In this way, although the mechanical system is actually composed of a spring and an inertial body, and is a dynamically unstable system with a resonance point, it is Since the gain characteristics were set based on the assumption that the

Therefore, an object of the present invention is to provide a control device for an electric motor that suppresses torsional vibration of a mechanical system due to torque ripple of the electric motor.

The present invention suppresses torsional vibration caused by torque ripple by incorporating a notch filter having a gain characteristic in the opposite direction to the gain characteristic near the resonance point of the mechanical system into the speed control loop of the control device.

The present invention will be described below with reference to drawings of embodiments.

FIG. 6 is a circuit diagram of a notch filter constituting the motor control device of the present invention. In this notch filter circuit, the resistance values of the variable resistors VRI and VR2pVR3 and the capacitances of the 05 capacitors C1, C2, and C3 are equal. The center frequency fn of the notch filter should be matched with the resonance frequency of the mechanical system using this resistance value R and capacitance C.
is (y1==−2πRCi where k: torsional stiffness of coupling 6 (Kg, q
, m, e: S, , e, l:: ] ■2; Moment of inertia of the partner machine 5 (Kg - Cm cSe', 0.'''J.

If the distribution ratio of the variable resistor ■R4 is I, the depth Q of the notch (valley) of the notch filter is n - (2) 4 (1 - K) Just L/, 2 △f; In the operating frequency of the notch filter (1
-1z).

The gain characteristics of the notch filter are VOUT1+R2C2S2 □d□・・・・・・・・・(3) VIN 1+QRC80R2c2S However, S = 2πfj (f; frequency (Hz)).

j: imaginary unit) It is. OP is an operational amplifier.

FIG. 7 is a diagram showing the gain characteristics of this notch filter. Notch filter with such characteristics (transfer function 1
When <F) is incorporated between the speed regulator and torque converter of the conventional speed loop in Fig. 4 (Fig. 8), the gain of the speed control loop with a resonance peak as shown in Fig. 5 (1) is obtained. The characteristics are flattened as shown in FIG. 9, and torsional vibration due to torque ripple in the frequency band near the resonance point of this speed control loop is suppressed, allowing stable and quiet operation of the motor.

The present invention incorporates a notch filter having a gain characteristic in the opposite direction to the gain characteristic near the resonance point of the mechanical system in the speed control loop of the control device, so that torsional vibration due to torque ripple is suppressed and stable. In addition, quiet operation of the electric motor is possible.

Conventionally, methods for suppressing this torsional vibration include (1) changing the structure of the electric motor, coupling, and mating machine to shift the resonance point; (il)) reducing the size of the clip itself; however, the present invention It has the advantage that it can be realized easily and at low cost compared to these.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional AC servo motor drive system, Figure 2 is a block diagram of the speed control loop in Figure 1, Figure 3 is a model diagram of the mechanical system in Figure 1, and Figure 4 is a block diagram of the speed control loop in Figure 1. FIG. 3 is a block diagram of the speed control loop corresponding to the mechanical system model shown in FIG. 3. FIG. 5 is a diagram showing the gain characteristics corresponding to the mechanical system model shown in FIG. 3. FIG. The circuit diagram of the filter, Figure 7 shows its gain characteristics, Figure 8 is a block diagram of the speed control loop incorporating the notch filter shown in Figure 6, and Figure 9 shows the gain characteristics of the speed control loop shown in Figure 8. FIG. 1: Electric motor 2: Control device 3: 3-phase AC power supply 4: Resolute sensor 5: Mating machine 6: Coupling AN(S): Transfer function of speed regulator KF: Transfer function of notch filter KT: ) Lurk converter Transfer function KM: Mechanical system transfer function KN: Resolver transfer function.

Claims (1)

[Claims] A gain near the resonance point of a mechanical system that inputs the output signal of a speed detector that detects the rotational speed of a machine connected to the output shaft of an electric motor and a deviation signal between a speed command signal and outputs a current command signal to the electric motor. 1. A control device for an electric motor, comprising a notch filter having a gain characteristic opposite to the characteristic.