JPS62166796A - Control system for dc servo motor - Google Patents

Abstract

PURPOSE:To suppress current ripples due to PWM control, by a method wherein, at the OFF mode, one switching circuit is held to the ON state and induction current flows without passing through a DC power source. CONSTITUTION:Output of a comparator 5p is inverted in a logic inverter 9p and the output is inputted to a pulse amplifier 72 through a delay circuit 10p, and output of a delay circuit 8p is inputted to a pulse amplifier 71. Output of a comparator 5N is inverted in a logical inverter 9N and the output is inputted to a pulse amplifier 74 through a delay circuit 10N, and output of a delay circuit 8N is inputted to a pulse amplifier 73. Consequently, at the OFF mode, even after the transistor (Tr) 11 is turned off, the transistor 14 is continued on, and induction current of the motor 4 flows in the passage from the Tr 14 to the diode 22 thereby the induction current flows until the motor voltage becomes zero irrespective of voltage of a DC power source 3.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention is directed to a control system for a direct redundant servo motor for a manipulator.

B0 Summary of the Invention The present invention controls the current of a DC servo motor by connecting a switch circuit in which transistors and diodes are arranged in antiparallel as a bridge, and driving the switch circuits in the same position with pulse width variation iJ (PWM). In the case of an on mode in which two switch circuits can be turned on, and
By repeating the OFF mode, which controls the unilateral OFF of the two switch circuits, the control voltage suitable for torque control,
It is designed to be easy to understand.

C5 Conventional technology In electric masks and slave manipulators, DC servo motors are often used as actuators, and the slave side, which follows the operation on the mask side, acts on the operation target, and the force exerted on the object is also reflected on the mask side. Many methods are adopted.

Unlike the position and speed control of a servo motor, the Koushita manibulator uses torque control to control the mask,
The motor currents of the arm and slave arm are controlled.

FIG. 3 shows nine parts of a conventional servo motor control circuit. In the main circuit, power transistors 11 to 14 are bridge-connected, and flywheel diodes 21 to 24 are connected in antiparallel to each transistor 11 to 14, and a voltage E is applied from a DC power supply 3 to the bridge circuit, and the output terminal A DC servo motor 4 is connected to. The PWM control circuit has a pair of comparators 5p and 5N that receive and receive an iIj flow command value Vs given from a torque control amplifier (not shown) and a triangular wave (carrier wave) signal VT, and output signals according to the positive or negative polarity of the command value VS. A PWM waveform control signal is obtained from one of the comparators 5p and 5N. The on/off ratio of this control signal corresponds to the level of the command value vs.

Both comparators 5p and 5N are configured to drive one of power transistors 11 and 14 or 12 and 13 with an iPWM waveform via AND gates 6P and 6N and pulse amplifiers 71 to 74, respectively. An1° gates 6P and 6N are gated by delay circuits 8P and 8N, and the upper and lower transistors 11 and 12 or 13 and 4 are simultaneously activated when switching between the comparators 5P and 5N, that is, when the motor 4 is switched between forward and reverse directions. A dead time is provided to prevent turning on.

In such a configuration, if the current command value vs is of positive polarity (normal rotation of the motor 4), the comparator 5P1: The command value V
A PWM pulse output with an on/off ratio corresponding to s is taken out, and this output controls transistors 11+14 to be turned on and off simultaneously, and the servo motor 41 is supplied with a PWM waveform DC lightning current (arrow route). . In detail, as shown in Fig. 4, when the transistors 11 and 14 are in the ON operation period (mode ■), current flows along the path shown by the solid line in Fig. 4 (8), and when the transistors 11 and 14 are in the OFF operation period In (mode ■), a flywheel lightning current flows along a path as shown in FIG.

D4 Problems that the invention aims to solve In the conventional servo motor control system, transistors 11+ 14 and 12+ 13 in the main circuit are controlled on and off by drive pulses of the same PWM waveform. The regenerative W flow can flow from a state where the induced voltage V is greater than E to a state where V=E with respect to the voltage E of the power supply 3.

However, in a state where the conduction rate is low and the current is on its side, flow or disconnection occurs during the period from mode ■ to mode ■.In other words, the motor current becomes an intermittent current that is not continuous, and the ripple component becomes large in the motor current. There was a problem with torque pulsation. This phenomenon becomes more pronounced as the flow rate decreases, and it deteriorates the operability when descending which requires a delicate operating force, and in the case of the pirate system, it appears as a vibration reaction force on the operator side, further impairing the operability.

In addition, the average lj current of the motor with respect to the conduction rate has a nonlinear characteristic as shown by characteristic A in Fig. 5, and there is also the problem that the current change rate near the corner point of this characteristic fluctuates greatly, resulting in poor operability. Ta.

Means and operation for solving the E0 problem The present invention has been made in view of the above problems, and in the on mode, both transistors of the switch circuit are controlled to be turned on, and in the off mode, only one of both transistors is controlled to be turned off. It is equipped with a control circuit, and even in the off mode, the induced current flowing to the DC servo motor after the on mode continues to flow down through a path that passes through the diode of the switch circuit that faces the transistor that remains on control and goes down.

F. Example FIG. 1 is a circuit diagram showing one embodiment of the present invention.

3 and 14 in the same figure, the output of the comparator 5P is inverted by the logic inverter 9P, this output is input to the pulse amplifier 72 via the delay circuit LOp, and the output of the delay circuit BP! A pulse amplifier 710 is input.

Then, the output of the comparator 5N is output from the logic inverter 9N.
This output is input to the pulse amplifier 74 via the delay circuit ION, and the output of the delay circuit 8N is input to the pulse amplifier 73.

With such a PWM control circuit, the transistor 11+
14 or 12+13, in the on mode (corresponding to the conventional mode I), both transistors are controlled to be turned on at the same time, and in the off mode (corresponding to the conventional mode ■), the transistor 11 or 13 is controlled to be off, and the transistor 12 or 14 is controlled to be turned on. be done. As a result, in the on mode, the current path is the same as the conventional one, but in the off mode, as illustrated in FIG. 14 through the path of the diode 22, and the lightning of the DC power supply 3.

Regardless of the current, the induced current can be allowed to flow until the motor snow pressure becomes zero. At this time, if the conduction rate is 10% or more, the W current becomes continuous, and compared to the conventional method where the current is continuous at a conduction rate of about 60% or more, a continuous current can be obtained from a low conduction rate. . In addition, the conduction rate, average DC current, and current characteristics are linear characteristics as shown as characteristic B in FIG. 5, and are characteristics suitable for torque control compared to nonlinear characteristics in the conventional system.

In the embodiments, it goes without saying that the design of the PWM control circuit may be changed as appropriate to obtain equivalent control characteristics.

G0 Effects of the Invention As described above, according to the present invention, in the off mode, one switch circuit is held in an on state so that the induced current path of the DC servo motor flows down without passing through the DC power supply. It can suppress current and current ripples through control, and when applied to the control of DC servo motors for manipulators that use torque control, it has the effect of reducing torque ripples and improving operability by making the average DC characteristics relative to the conduction rate linear. .

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
Figure 3 is a diagram of the main part control circuit of a conventional servo motor, Figure 4 (8) is a diagram of the current path in off mode in the figure, Figure 4 (B) is a current route diagram of the conventional mode ■. 5 is a diagram of the current path of the conventional mode ①, and FIG. 5 is a characteristic diagram of the conduction rate and average DC current in the conventional and conventional modes. 11+14...Transistor, 21+24...Diode, 3...DC power supply, 4...DC servo motor, 5P, 5N...Comparator, 71.72...Pulse amplifier, 8P, 8N. 10p, ION...Delay circuit, 9P, 9N ・
...Logic inverter. Figure 2

Claims (1)

[Claims] The main circuit consists of a bridge-connected switch circuit in which transistors and diodes are connected in anti-parallel, and a DC servo motor is connected to the output end, and the transistors in the opposite switch circuits among the four switch circuits in this main circuit are pulse-width modulated. and a PWM control circuit driven by a signal, wherein the control circuit controls both transistors of the switch circuit to be turned on in an on mode, and controls only one of the two transistors to be turned off in an off mode. Servo motor control method.