JPH0522971A - Servo controller - Google Patents

Abstract

PURPOSE:To provide a servo control apparatus which reduces fluctuation in the number of rotations by applying, depending on the conditions, an ordinary speed controller and a PLL system speed controller. CONSTITUTION:Both an ordinary speed controller 2 and a PLL system speed controller 7 are provided and it is decided from which controller a current instruction signal is given to a current controller 3 with a signal switching apparatus 8, upon decision in a speed control switching decision unit 9 from the condition of a position instruction signal input to a position controller 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device equipped with a signal switching device capable of switching the control by adding a PLL type speed control device to a conventional servo control device.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional servo control device. In the figure, 1 is a position control device, 2 is a speed control device, 3 is a current control device, 4 is a servo motor, and 5 is a rotary encoder. Position control device 1 for controlling the position of servo motor 4 by a position command signal input from a higher-level control device and a feedback pulse from rotary encoder 5, a speed command signal from position control device 1 and feedback from rotary encoder 5. It is composed of a speed control device 2 for controlling the speed of the servo motor 4 by a pulse, and a current control device 3 for outputting the drive voltage of the motor by the current command signal from the speed control device 2 and the current feedback from the servo motor 4. It was a triple-loop control of position, speed, and current. In the speed control device 2, both the speed command signal from the position control device 1 and the feedback pulse from the rotary encoder 5 are U
Input to the P / DOWN counter and the UP / DOWN
The speed error value is calculated by periodically reading the value of the counter, and the speed control calculation is executed.

[0003]

However, in the case of the above-mentioned conventional speed control device, when trying to increase the speed loop gain, the dead time of the speed control system is too large or P
Due to the imbalance of ID velocity gain (proportional / integral / derivative) setting, the system became unstable and the required performance could not be obtained. Thus P
If the ID speed gain is not sufficiently increased, the servo motor may have uneven rotation due to the effect of torque unevenness such as cogging torque of the servo motor itself. In particular, it occurred not at the time of acceleration / deceleration but at a steady state in the low speed range of about several tens of rpm. The present invention solves the above conventional problems, and an object of the present invention is to provide an accurate servo control device with less uneven rotation.

[0004]

In order to achieve the above object, a servo control device of the present invention is a current output from a PLL type speed control device, a conventional speed control device and a current PLL type speed control device. A signal switching device that can switch the command signal to either one and a speed control switching determination device that determines whether to switch to the other depending on the state of the speed command signal are provided.

[0005]

According to the present invention, depending on the state of the speed command signal,
It is possible to switch between the conventional speed control device and the PLL type speed control device added this time, and it becomes possible to perform optimum speed control according to each state.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.
In the figure, 1 is a position control device, 2 is a speed control device, 3
Is a current control device, 4 is a servo motor, 5 is a rotary encoder, 6 is a pulse train conversion device, 7 is a PLL type speed control device, 8 is a signal switching device, and 9 is a speed control switching determination device. The PLL speed control device 7 is a control device that operates so as to match the phase of the frequency of the reference pulse train with the frequency to be compared. When the phases match, the frequency is inevitably synchronized. That is, the speed control of the PLL system operates so that the speed command signal of the pulse train and the feedback pulse from the rotary encoder attached to the servo motor match. Further, as a feature of this PLL system, some rotation unevenness remains or an oscillation state occurs during acceleration / deceleration, but in the steady state where the rotation speed of the servo motor is constant, the rotation unevenness can be suppressed and accurate rotation can be obtained. Is known.

In the present invention, the speed control switching judgment device 9 and the signal switching device 8 are provided so that the conventional speed control device and the current PLL system speed control device can be switched and operated depending on the state of the deceleration command signal. .. Speed control is performed using a conventional speed control device during acceleration / deceleration, and a PLL type speed control device in a steady state in which the rotation speed of the servo motor is constant. Next, the embodiment of FIG. 1 will be described. First, in the speed control switching determination device 9 based on the speed command signal output from the position control device 1, a value (acceleration) obtained by differentiating the speed command signal is used as a parameter, and the conventional speed control device is used during acceleration / deceleration. In a steady state in which the rotation speed of the servo motor is constant, the parameters are set so that speed control is performed using the PLL type speed control device. The signal switching device 8 operates according to the determination signal output from the speed control switching determination device 9, and either the speed control device 2 or the PLL type speed control device 7 is selected and the speed control is executed. The pulse train conversion device 6 converts the speed command signal from the position control device 1 into a pulse train speed command signal and inputs it to the PLL type speed control device 7 as a command value.

[0008]

As is apparent from the above description, the servo control device of the present invention has the following advantages.

(1) The servo system is stable during acceleration and deceleration, and the rotation unevenness of the servo motor in a steady state can be greatly reduced.

(2) In a steady state, the torque disturbance applied to the servo motor can be greatly reduced, and a servo system with high stability can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a servo control device of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional servo control device.

[Explanation of symbols]

 1 Position control device 2 Speed control device 3 Current control device 4 Servo motor 5 Rotary encoder 6 Pulse train conversion device 7 PLL type speed control device 8 Signal switching device 9 Speed control switching determination device

Claims (1)

Claims: 1. A servo motor, a rotary encoder directly connected to the servo motor, a position for controlling the position of the servo motor by a position command signal externally instructed and a feedback pulse from the rotary encoder. Control device, speed control device that controls the speed of servo motor by speed command signal output from position control device and feedback pulse from rotary encoder, current command signal output from speed control device and detected from servo motor A current control device for controlling the current of the servo motor from the current feedback signal, a pulse train conversion device for converting the speed command signal output from the position control device into a speed command signal of a pulse train, and a feedback pulse from the rotary encoder. Power from the pulse train converter A PLL type speed control device for controlling the speed of a servomotor by a speed command signal of a loose train, and a current command signal given to the current control device is made a current command signal from the speed control device, or this PLL system speed control Servo control provided with a signal switching device that can be switched to either a current command signal from the device or a speed control switching determination device that determines the switching direction of the signal switching device based on the state of the speed command signal. apparatus.