JPS6257008A - Positioning control system - Google Patents

Abstract

PURPOSE:To control vibrations of a mechanically movable part without any time delay even if the mechanically movable part vibrates abruptly by feeding the detection signal of an acceleration detector fitted to the mechanically movable part back to the control part for a servo-motor and controlling the servo- motor. CONSTITUTION:The acceleration detector A is fitted to the mechanically movable part MC and its detection signal is fed back to a speed control part through an amplifier AMP 3. The speed control part extracts a speed component from an acceleration signal to calculate the difference between this speed component and the detected speed information of an acceleration detector T1 which detects the rotating speed of the motor M, and drives the motor M to position the mechanically movable part MC. Thus, the acceleration of the mechanically movable part is detected and fed back to the speed control part or current control part for the servo-motor. Therefore, even if the mechanically movable part vibrates abruptly, the servo-motor is controlled without any time delay to correct the influence of the vibrations, thereby performing precise positioning control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a positioning control system for accurately positioning a numerically controlled machine.

(Prior Art) Conventionally, as a positioning control system for a numerically controlled machine, a system using a closed loop servo mechanism as shown in FIG. 5, for example, is known. As shown in the figure, this method detects the speed of a tachogenerator, etc. attached to a motor M. Detected speed information and detected position information of position detector R1 such as T1 and resolver are fed back to the input side and added to adders ADI and AD2,
In the adder ADI, the NC controller section C0NT
The command position information from the position detector R1 is compared with the detected position information from the position detector R1, and the difference signal is used as the speed command and sent to the amplifier AM.
In addition to the adder AD2 via P1, the adder AD2 compares this speed command with the detected speed information of the speed detector TI, and outputs a speed amplifier AMP2 so that the difference becomes zero.
The remoter M is driven by the rotor, and the feed screw V is rotated to position the mechanical movable part MC.

In this way, in the conventional system configured to take speed feedback from the motor M side, it is not possible to compensate for vibrations in the mechanical system that occur at the end of positioning due to various elements of the mechanical system, so accurate positioning is difficult. There may be cases where this is not possible. If the speed feedback is taken directly from the machine side, vibrations in the mechanical system can be suppressed, but in general, if the mechanical system is included in the speed feedback, the mechanical system's internal characteristics will have a negative impact on the speed control loop, causing the motor to Even in a steady state where there is no speed difference between M and the mechanical movable part MC, that is, no vibration occurs, the characteristics of the mechanical system are fed back and the loop becomes unstable, which is undesirable.

Therefore, in the past, attempts have been made to prevent vibrations in the mechanical system using a positioning control system having a configuration as shown in FIG. 6, for example. This method is based on the configuration shown in Fig. 5, in which the position information of the mechanical system is fed back separately, and the position detector R2 is attached to the mechanical movable part MC.
The amount of movement of the machine is detected, the -force command position information is added to the deviation setter SM, the rotation angle of the output shaft of the motor M is obtained, and the two are compared in the adder AD3 to determine the overall mechanical system. Detect errors. The detected error signal drives the pulse oscillator OCL to generate a correction pulse corresponding to the error, and the adder AD4 adds this correction pulse to the command position information from the NC controller C0NT to rotate the motor M. This corrects the angle by the amount of the error. The error signal of adder AD3 also includes errors caused by vibrations in the Ia mechanical system, so in principle it is possible to suppress vibrations in the mechanical system, but this method generally does not allow position errors such as backlash errors and pitch errors. The gain of the system including the position detector R2 is limited by the natural frequency of the mechanical system, so if the natural frequency is low, the gain for minute displacements will be low. , the response to minute displacements such as vibrations is essentially slow, and therefore vibrations cannot be suppressed sufficiently.Furthermore, it requires a deviation setting device SM, which has the disadvantage that it is not economical.

Therefore, the applicant proposed a positioning control system with further improved positioning accuracy in Japanese Patent Laid-Open No. 55-34716.

FIG. 7 is a block diagram of the positioning control method proposed in the above-mentioned publication, and shows the case where the present invention is applied to the positioning control (method) that takes normal position and speed feedback from the motor M, and T2 is the speed Detector, AD5.AD
6 is an adder, AMP 3 is an amplifier, and the same symbols as in FIG. 1 indicate the same parts.

The command position information of the NC controller 5 C0NT is compared with the detected position information of the position detector R1 in the adder ADI, and the difference signal is added as a speed command to the adder AD2 via the amplifier AMPI. The adder AD2 compares the speed command with the speed information detected by the speed detector T1, and the motor M is driven by the speed amplifier AMP2 so that the difference becomes zero. Such operations are performed in exactly the same manner as in the conventional case.

The speed detector T2, which consists of a combination of a tacho generator and a rack and pinion or a combination of a linear position detector such as an inductor and a frequency voltage converter, and is directly attached to the machine side, measures the moving speed of the 411 machine moving part MC. The detected speed information is added to an adder AD5, and the adder AD5 calculates the difference between this detected speed information and the detected speed information of the speed detector T1 that detects the rotational speed of the motor M. Desired. This difference signal is amplified by amplifier AMP3 and output to adder AD6, where it is compared with the output signal of adder AD2. The speed amplifier AMP2 drives the motor M so that the comparison signal of the adder AD6 becomes zero, thereby positioning the mechanical movable part MC.

When vibration occurs in the mechanical system at the end of positioning, the speed detector T2 detects the vibration and sends detected speed information corresponding to the vibration speed to the adder AD5.
The detected speed information becomes zero at this time. Therefore, adder A
An error signal corresponding to the vibration of the mechanical system is sent from D5,
The adder AD6 compares the signal of the adder AD2 with its error signal, and the speed amplifier AMP2 drives the motor M so as to eliminate the speed difference. This operation immediately corrects vibrations in the mechanical system, allowing accurate positioning.

(Problems to be Solved by the Invention) As described above, the conventional positioning control method detects the moving speed of the moving parts of the machine and corrects the vibration of the mechanical system, so the characteristics have not been sufficiently improved. There were cases where there was none.

That is, when sudden vibrations occur, the system of feeding back the moving speed to the control unit may not be able to correct the vibrations of the mechanical system due to a delay of one hour or the like.

Therefore, the present invention aims to solve the problems of the prior art.

(Means for solving the problem) The present invention detects vibration information of the mechanical moving part by attaching an acceleration detector to a mechanical moving part driven by a servo motor, and uses the detected acceleration signal to control the speed of the servo motor. This invention solves the problems of the prior art as described above by providing a positioning control method characterized by controlling the servo motor by returning to the current control section or the current control section to suppress vibrations of the moving parts of the machine. It is.

(Function) The present invention controls the servo motor by feeding back a detection signal from an acceleration detector attached to a mechanical movable part to a control part of the servo motor. Therefore, even if sudden vibration occurs in the mechanical movable part, the servo motor can be controlled without time delay to suppress the vibration of the mechanical movable part.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a block diagram of a first embodiment of the present invention. In the following description, the same parts as those in the prior art are denoted by the same reference numerals, and some adders and amplifiers are omitted for the sake of simplicity.

In FIG. 1, an acceleration detector A is provided in the mechanical movable part MC, and a detection signal is fed back to the speed control part via an amplifier AMP3. The speed control section extracts the speed component from the acceleration signal, and calculates the difference between this speed component and the speed information detected by the speed detector TI that detects the rotational speed of the motor M. The motor M is driven to position the mechanical movable part MC.

It should be noted that the acceleration signal of the mechanical movable part can also be configured to be fed back to the current control part, ie, the torque control part, to control the motor M.

FIG. 2 is a block diagram of a second embodiment of the invention.

In this embodiment, the motor is used to drive a load having a relatively low rigidity transmission system, and is different from the first embodiment in that it does not have a position control group.

FIG. 3 is a block diagram of a third embodiment of the present invention,
In the first embodiment, the detection signal of the acceleration detector A is loaded with a function of removing disturbance noise through a bandpass filter F.

FIG. 4 is a block diagram of a fourth embodiment of the present invention,
The detection signal of the acceleration detector A through the amplifier AMP3 is
Proportional (P), Proportional Integral (PI), Proportional Integral Differential (PID)
) etc., and a highly accurate signal is input to the speed control section.

(Effects of the Invention) As explained above, the present invention detects the acceleration of the moving parts of the machine and feeds it back to the speed control part or the current control part of the servo motor, so that sudden vibrations do not occur in the moving parts of the machine. Even in such cases, the servo motor can be controlled without time delay, the influence of vibration can be corrected, and positioning control can be performed with high precision.

[Brief explanation of the drawing]

Figures 1 to 4 are block diagrams of each embodiment of the present invention, and Figure 5 is a block diagram of each embodiment of the present invention.
7 to 7 are block diagrams of conventional examples. C0NT...NC controller section, M...motor,
A... Acceleration detector, F... Bandpass filter. Patent applicant: Representative of FANUC Co., Ltd. Patent attorney: Minoru Tsuji Figure 5

Claims (3)

[Claims] (1) An acceleration detector is attached to the moving part of the machine driven by the servo motor to detect vibration information of the moving part of the machine, and the detected acceleration signal is returned to the speed control part or current control part of the servo motor to control the servo motor. A positioning control method that controls the motor and suppresses vibrations in the moving parts of the machine. (2) The positioning control system according to claim (1), characterized in that the acceleration signal is fed back to the speed control section or current control section of the servo motor through a bandpass filter. (3) The acceleration signal is fed back to the speed control section or current control section of the servo motor through a proportional (P), proportional integral (PI) or proportional integral differential (PID) compensation circuit. The positioning control method described in scope item (1).