JPH08278820A - Damping method for servo control system - Google Patents

Abstract

PURPOSE: To provide a damping method which can damp a servo control system without adding particularly a mechanical detector to a driven part to detect the velocity of this driven part. CONSTITUTION: In a servo control system 10, the revolving angular velocity θm ' of the drive shaft of a motor 3 is detected by a detector 6 that is originally provided. On the other hand, the estimated value θa 'Λ of the revolving angular velocity of an arm that is driven by the motor 3 is calculated from the revolving angular velocity θm ' and a torque T given from the detector 6 and based on a model expression that is previously set in an arithmetic circuit 7. The estimated value θa 'Λ is fed back to the control command value of the motor 3 and the system 10 is damped. Therefore, it is not required to provide any mechanical detector on the arm to detect its revolving angular velocity, etc. As a result, the constitution of the arm can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention returns the speed of a driven portion such as a robot arm operated by a driving portion such as a servomotor to the control command amount of the driving portion, so that the driving portion and the driven portion can be controlled. The present invention relates to a vibration suppression method for suppressing vibration of a servo control system including a drive section, and particularly relates to a vibration suppression method for a servo control system which requires a simple structure.

[0002]

2. Description of the Related Art Many industrial robots have a cantilever structure whose mechanism is unstable. Also,
Between the motor and the arm of the robot, there is an elastic power transmission mechanism such as a speed reducer. In addition, the natural frequency of the robot mechanical system is often low. Therefore, when a large acceleration / deceleration is generated in the arm during the operation of the robot, the natural frequency of the mechanical system is excited and residual vibration remains, which may cause a functional problem. This problem becomes particularly noticeable when elastic deformation occurs in the power transmission mechanism between the arm and the motor. Further, not only the robot as described above, but also a system in which a driven part as an inertial load is driven by a driving part such as a motor through a power transmission mechanism in which elastic deformation cannot be ignored, a similar vibration problem occurs. . For such vibration, Japanese Patent Laid-Open No. 54-31877
In the technique disclosed in Japanese Patent Publication, the inertial load side is provided with each detector for detecting its displacement, speed and acceleration, and the detection result of the speed on the inertial load side is fed back to the control command amount on the drive section side. This increases the apparent rigidity and damping of the entire mechanical system, thereby suppressing vibration of the mechanical system. FIG. 3 shows a servo control system that is substantially equivalent to the technique disclosed above. The servo control system 10 _a illustrated in the drawing, similarly to the general configuration, detects the rotation angular velocity theta _m 'to the drive shaft of the motor 3, for example, a detector 6 made of tachometer, etc. are disposed. Further, the drive shaft is provided with a detector 5 such as a pulse transmitter for detecting the rotation angle θ _m . On the other hand, on the arm side, a detector 8 for detecting the rotational angular velocity θ _a ′ of the arm is provided. Therefore, in the servo control system 10 _a , the torque T as the control command amount given to the motor 3 is set so that the rotation angle θ _{m of the} motor becomes the preset rotation angle θ _d.
Is calculated and input to the motor 3. At this time, the motor 3
The rotational angular velocity θ _m ′ of the drive shaft is detected by the detector 6 and compared with the rotational angular velocity θ _a ′ of the arm detected by the detector 8. Then, the difference between the detected rotational angular velocity θ _m ′ of the drive shaft of the motor 3 and the rotational angular velocity θ _a ′ of the arm is made to approach 0, that is, the apparent rigidity of the mechanical system of the servo control system 10 _a , The value of the difference is fed back to the control command amount side of the motor 3 so as to increase the damping. Below, ‘(dash) attached to the right of each code
Indicates the first-order time differential value for that code, and "(2 dash) indicates the second-order time differential value.

[0003]

By the way, according to the prior art disclosed above, it is necessary to mount a mechanical detector for detecting the rotational angular velocity on the arm side of the robot. However, in the robot arm,
Generally, the space is small and it is preferable to reduce the number of built-in parts as much as possible. There is also a problem in that the wiring between the motor and the side becomes complicated when each of the detectors is mounted in the arm. Therefore, an object of the present invention is to provide a damping method of a servo control system capable of damping the system without providing a mechanical detector for detecting the speed of the driven part on the driven part. That is.

[0004]

In order to achieve the above object, the main means adopted by the present invention is the gist of the present invention, in which the speed of the driven part operated by the driving part is controlled by the driving command. In a vibration damping method for suppressing the vibration of a servo control system including the drive unit and the driven unit by returning the amount to the amount, at least a control command amount to the drive unit and an operation amount from the drive unit, A relationship for obtaining the speed of the driven part from the inertia of the driven part is set in advance, and based on the set relationship from the control command amount to the driving part and the operation amount from the driving part, It is configured as a vibration control method for a servo control system, which is characterized in that the speed of the driven portion is calculated.

[0005]

In the damping method for the servo control system according to the present invention, at least the control command amount to the drive unit, the operation amount from the drive unit, and the speed of the driven unit from the inertia of the driven unit are determined. The desired relationship is preset. Then, the speed of the driven part is calculated from the control command amount to the driving part and the operation amount from the driving part based on the set relationship. Therefore, the driven part does not need a mechanical detector for detecting the speed of the driven part.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not intended to limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing a robot used for applying a vibration damping method of a servo control system according to an embodiment of the present invention, and FIG. 2 is a servo control system for controlling while suppressing the vibration of the robot. 3 is a block diagram showing the configuration of FIG. However, Figure 3
The shown in the common with conventional servo control system 10 _a component, while using the same reference numerals, and a detailed description thereof will be omitted. In a mechanical system such as a robot to which the servo control system of the present embodiment is applied, as shown in FIG. 1, a motor 3 includes an arm 3 as an inertial load via a power transmission mechanism 2 such as an elastic speed reducer. It is designed to rotate.

The motor 3 is used in the present embodiment shown in FIG.
It is controlled by the example servo control system 10. In addition, in FIG.
The part surrounded by the broken line is a general speed control type servo motor.
It has the same configuration as the data driver. Current in this configuration
The minor loop has a sufficiently fast response, and
The motor 3 outputs the torque according to the control command value (torque T)
Suppose you do. The motor 3 has a rotation angle
Originally equipped with a degree detector 5 and a rotational angular velocity detector 6
It The servo control system 10 according to the present embodiment is shown in FIG.
As shown in FIG._aAnd basic
The conventional servo control system 10 has substantially the same structure. _aWhen
The difference is that the rotational angular velocity of arm 1 (driven part) is detected
The configuration without the mechanical detector 8 is adopted.
In place of the output device 8, at least the torque T to the motor 3
(Control command amount) and the motor 3 detected by the detector 6
Rotational angular velocity θ from_m′ (Manipulation amount) and the arm 1
Inertia I_aAnd the spring constant K of the power transmission mechanism 2
The rotational angular velocity θ of the arm 1_aOperation to calculate ′ ^
The circuit 7 is provided.

By the way, assuming that the damping rate of vibration of the mechanical system of the robot shown in FIG. 1 is very small, and ignoring this damping rate, the equation of motion of the mechanical system can be derived as follows. . I _a θ _a ″ + K (θ _a −θ _m ) = T (1) I _m θ _m ″ + K (θ _m −θ _a ) = 0 (2) where I _a : arm 1 Moment of inertia (inertia; converted value of drive shaft of motor 3) I _m : moment of inertia of motor 3 (inertia) θ _a : rotation angle of arm 1 (converted value of drive shaft of motor 3) θ _m : rotation angle of motor 3 K: Spring constant of the power transmission mechanism 2 (converted value of the drive shaft of the motor 3) T: Torque of the motor 3 (control command amount).

In this case, the rotational angular velocity θ _m ′ of the motor 3 can be detected by the detector 6 originally provided. on the other hand,
The rotation angle θ _a and the rotation angular velocity θ _a ′ of the arm 1 on the downstream side of the power transmission mechanism 2 such as the speed reducer in the power transmission direction are not actually provided with a mechanical detector for detecting them, so Although it cannot be detected, it is assumed that the parameters of the equations of motion of the above equations (1) and (2) can be obtained to some extent accurately by a parameter identification method or the like. Thereby, the rotational angular velocity on the arm 1 side can be estimated from the following balance equations (3) and (4). θ _a −θ _m = (T−I _a θ _a ″) / K (3) where θ _a ″ is the calculated rotational angular acceleration of the arm 1 and when the equation (3) is first-order differentiated. , Θ _a ′ ^ = (d / dt) ((T−I _a θ _a ″) / K) + θ _m ′ (4) where θ _a ′ ^: estimated rotational angular velocity θ of the arm 1 _m ′: Measured rotational angular velocity of the motor 3. However, it is desirable that the differential operation of the equation (4) is accompanied by a low-pass filter process in order to actually remove noise. Any of the relationships expressed by the expressions (4) to (4) is preset and stored as a program in a memory (not shown) of the arithmetic circuit 7 as a model expression.

Therefore, in the servo control system 10,
When the motor 3 is driven by the control command amount of the torque T,
The rotational angular velocity θ _m ′ of the drive shaft is detected by the detector 6 and input to the arithmetic circuit 7. This arithmetic circuit 7 is
From the rotational angular velocity θ _m ′ (operation amount) of the drive shaft of the motor 3 and the torque T (control command amount) to the motor 3, an estimated value of the rotational angular velocity of the arm 1 is calculated based on the relationship of the above equation (4). Calculate θ _a ′ ^. The above-calculated estimated value θ _a ′ ^ of the rotational angular velocity of the arm 1 is compared with the rotational angular velocity θ _m ′ of the drive shaft of the motor 3, so that the difference between them is
It is fed back to the control command amount side of the motor 3. This apparently increases the rigidity and damping of the mechanical system of the robot. As a result, the device of this embodiment does not provide a mechanical detector for detecting the rotational angular velocity of the arm 1 on the arm 1 which is a driven part, and calculates the rotational angular velocity of the arm 1 by calculation in the arithmetic circuit 7. Calculation can be performed, and vibration of the mechanical system can be suppressed by using this rotational angular velocity. Therefore, the internal structure of the arm 1 can be simplified.

By the way, in the industrial robot, the inertia of the arm 1 (inertial load) may change greatly depending on its posture. In order to deal with such a case, by applying a relational expression of the arithmetic circuit 7 in which the inertia I _a is variable according to the posture of the robot, the vibration control for the mechanical system in which the inertia changes as described above. It is possible to prevent a decrease in effect. In the above embodiment, the rotational angular velocity θ _m ′ of the motor 3 which is controlled based on the given torque T is detected by the detector 6. However, for example, the control command amount given to the motor 3 is When the speed command value is used instead of the torque T, the speed command value may be directly input to the arithmetic circuit 7 without using the detector 6.

[0012]

According to the present invention, the speed of the driven portion operated by the driving portion is returned to the control command amount of the driving portion, so that the servo control including the driving portion and the driven portion is performed. In a damping method for suppressing system vibration, at least a relationship for obtaining a control command amount to the drive unit, an operation amount from the drive unit, and a velocity of the driven unit from inertia of the driven unit is set in advance. Every time, the speed of the driven part is calculated from the control command amount to the driving part and the operation amount from the driving part, based on the set relationship, and a damping method of the servo control system. Will be provided. As a result, the vibration of the system can be suppressed without providing the driven part with a mechanical detector for detecting the speed of the driven part. As a result, the structure of the driven portion can be extremely simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a robot used for applying a vibration suppression method for a servo control system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a servo control system that controls while suppressing the vibration of the robot.

FIG. 3 is a block diagram showing a configuration of a conventional servo control system of a robot which is an example of the background of the present invention.

[Explanation of symbols]

1 ... arm (driven unit) 2 ... power transmission mechanism 3 ... motor (drive unit) 6 ... detector 7 ... arithmetic circuit 10, 10 _a ... servo control system T ... torque (control instruction amount) theta _m '... of the motor Rotational angular velocity (manipulation amount) θ _a ′ ... Estimated value of rotational angular velocity of arm I _a ... Inertia of arm

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G05D 3/00 G05D 3/00 X 13/62 13/62 E 19/02 19/02 D // B25J 9/16 B25J 9/16

Claims (1)

[Claims] 1. The vibration of a servo control system including the drive unit and the driven unit is suppressed by returning the speed of the driven unit operated by the drive unit to the control command amount of the drive unit. In the vibration damping method, at least a relationship for obtaining the speed of the driven portion from the control command amount to the driving portion, the operation amount from the driving portion, and the inertia of the driven portion is set in advance, and A method for damping a servo control system, wherein the speed of the driven part is calculated from the control command amount and the operation amount from the driving part based on the set relationship.