JPH03285586A - Controller for servomotor - Google Patents

Abstract

PURPOSE:To prevent oscillation and/or generation of vibration by a method wherein the result of the operation of a speed is compared with a predetermined value when a speed commanding signal has become lower than a given value and when the result of the operation of speed is higher than the predetermined value, the speed commanding signal is replaced with the result of operation of speed to output it and effect the operation of a torque command by this value. CONSTITUTION:A speed signal correcting and processing unit 13 judges whether the absolute value of a speed commanding signal Ei is higher than a given value or not and when the absolute value is higher than the given value, the speed signal of the result of operation is judged whether it is higher than the predetermined value of speed. When the speed signal is higher than the predetermined value of speed, the speed signal is replaced with the speed commanding signal Ei to output it to a torque commanding and operating unit 14. Accordingly, the speed signal, having a small difference between the speed commanding signal Ei, is inputted into the torque commanding and operating unit 14 and, therefore, a speed control loop will never responds excessively and oscillation and/or the generation of vibration can be prevented even when the load of a servomotor 16 is reduced suddenly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for a servo motor connected to a load having play such as backlash.

BACKGROUND OF THE INVENTION FIG. 3 shows the configuration of a conventional control device for a servo motor of this type. In FIG. 3, 1 is a speed control section, which has a speed calculation section 2 and a torque command calculation section 3. 4
is a current side (company) section, which drives the servo motor 5 by restricting the current to obtain a predetermined torque from the torque command calculation section 3 of the speed control section I11. Reference numeral 6 denotes a current detector for detecting the current flowing through the armature of the servo motor 5 and feeding it back to the current control section 4. Reference numeral 7 denotes a load having play, such as a hack run, which is connected to the rotating shaft of the servo motor 5. 8 is an encoder connected to the rotation shaft of the servo motor 5, and detects the rotation angle of the servo motor 5. Reference numeral 9 denotes a feedback circuit for feeding the pulses output from the encoder 8 to the speed calculating section 2.

Next, the operation of the conventional example will be explained. Current control section 1
When the servo motor 5 rotates in response to current supplied from the servo motor 5, the current flowing through the armature of the servo motor 5 is detected by the current detector 6
The pulses are detected by the encoder 8 and are feedback-controlled according to the load 7, and the pulses output from the encoder 8 are manually inputted to the speed calculation unit 2 via the feedback circuit 9, where the pulses within a predetermined time (cycle) are The number of rotational speeds of the servo motor 5 is determined, and this is compared with the speed command signal Ei, and a current value is determined in the torque command calculation section 3 so that there is no difference between the two, and based on this current value. Then, the current control section 4 controls the speed of the servo motor 5 by 1vIJ while performing the feedback control described above.

In this way, even in the conventional servo motor 1Jall device, the speed can be accurately controlled according to the load of the motor.

Problems to be Solved by the Invention However, in the conventional device, the speed command signal Ei
In such a case, the load torque may suddenly become lighter due to the play in the load, and the speed may suddenly increase over several periods of the speed calculation period. At this time, there is a problem in that the speed control responds excessively, causing oscillations and vibrations.

The present invention solves these conventional problems, and prevents the occurrence of oscillations and vibrations in a servo motor connected to a load with play, even when the load on the motor suddenly decreases. The object of the present invention is to provide a servo motor control device that can perform the following functions.

Means for Solving the Problems In order to achieve the above object, the present invention compares the speed calculation result with a predetermined value when the speed command signal becomes less than a certain value, and if the result is greater than or equal to the predetermined value, In this case, the speed command signal is replaced with the speed calculation result and outputted, and the torque command calculation is performed using this value.

Effect of the Invention With the above-described configuration, the present invention can reduce the deviation between the speed command signal and the speed signal in the torque command calculation even when the load on the motor suddenly decreases, thereby reducing the oscillation of the servo motor. It is possible to prevent the occurrence of vibrations and vibrations.

Embodiment FIG. 1 shows the structure of an embodiment of the present invention. In FIG. 1, 11 is a speed side @ part, a speed calculation part 12,
It has a speed signal correction processing section 13 and a torque command calculation section 14. Reference numeral 15 denotes a current control section, which controls the current from the torque command calculation section 14 of the speed control section 11 to obtain a predetermined torque, thereby driving the servo motor 16. Reference numeral 17 denotes a current detector for detecting the current flowing through the armature of the servo motor 16 and feeding it back to the current control section 15.

Reference numeral 18 denotes a load having play, such as a pack run, which is connected to the rotating shaft of the servo motor 16. An encoder 19 is connected to the rotating shaft of the servo motor 16, and detects the rotation angle of the servo motor 160. 20 is encoder 1
This is a pulse multiplier circuit that converts the pulse signal generated by the pulse train 9 into a pulse train and outputs the pulse train to the speed calculation section 12.

Next, the operation of the above embodiment will be explained. Current control section 1
When the servo motor 16 rotates in response to the current supplied from the servo motor 1, the current flowing through the armature of the servo motor 16 is detected by the current detector 17, and feedback control is performed so that the torque is constant according to the load 18. be done. On the other hand, the pulse signal output from the electric recorder 19 is converted into a pulse train by the pulse multiplier circuit 20, and the pulse signal is converted into a pulse train by the speed calculation unit 12.
Output to. The speed calculation section 12 calculates the actual speed by counting the output from the pulse multiplier circuit 20 at a predetermined time, and outputs the speed signal ωn to the speed signal correction processing section 13.

In the speed signal correction processing section 13, calculations are performed according to the operation shown in FIG. That is, step 2
1, the absolute value of the speed command signal Ei is constant 1f! E
It is determined whether or not it is equal to or greater than i1, and if so, it is determined in step 22 whether or not the speed signal ωn as a result of the calculation is equal to or greater than a predetermined velocity value 011, and if so, in step 23 , speed signal ωn
is replaced with the speed command signal Ei and the torque command calculation unit 14
Output to. Therefore, the torque command calculation unit 14 receives the speed signal ωn that has a small deviation from the speed command signal Ei, so that the speed control loop does not respond excessively.
Oscillation and vibration of the servo motor 16 are prevented from occurring.

Effects of the Invention As described above, according to the present invention, when the speed command signal becomes less than a certain value, the speed calculation result is compared with a predetermined value, and if this is greater than the predetermined value, the speed command is Since the signal is replaced with the speed calculation result and output, and this value is used to calculate the torque command, even if the load on the motor suddenly decreases, the speed command signal and speed signal used in the torque command calculation can be changed. The deviation from the servo motor can be reduced, and oscillation and vibration of the servo motor can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram of a servo motor control device showing an embodiment of the present invention, Fig. 2 is a flowchart showing the allocation operation in the same device, and Fig. 3 is an example of a conventional servo motor control device. FIG. 11... Speed control section, 12... Speed calculation section, 13.
...Speed signal correction processing unit, 14...Torque command calculation unit, 15...Current control unit, 16...Servo motor, 1
7... Current detector, 18... Load, 19... Encoder, 20... Pulse multiplier circuit.

Claims (1)

[Claims] In a servo motor control device that calculates a torque command at a speed calculation cycle from a speed command signal to a servo motor connected to a load with play and a speed signal fed back from the servo motor, the encoder connected to the servo motor a pulse multiplier circuit that converts the pulse signal of the pulse signal into a pulse train; a speed calculation means that calculates the actual speed by counting the output from the pulse multiplier circuit within a predetermined time;
When the speed command signal is below a certain value, the speed calculated by the speed calculation means is compared with a predetermined value, and when the speed is above the predetermined value, the speed command signal is output as a speed signal and a torque command is calculated. A servo motor control device comprising speed signal correction processing means.