JPS63308603A - Oscillation reducing system for robot - Google Patents

Abstract

PURPOSE:To reduce the oscillation of the arm of a robot by changing the gain of a servo system of the period only to execute the adjustable speed so that the accelerating time of a system including a load, an arm and a motor can be the integer-fold of 1/2 of the inherent oscillating period of the system. CONSTITUTION:A robot is equipped with a motor 1 and an arm 2, and the arm 2 holds and moves a load 3. At the time of the action, the load or arm are driven by a time pair speed characteristic line 1 like the graph shown in the figure. Corresponding to it, the acceleration speed of the load, etc., is changed in correspondence like a line 12 as shown in the figure. Due to the change of the acceleration, the oscillation occurs at the system of the arm, etc., when rigidity is weaker. When the period to add the acceleration is T and the period of an inherent oscillation 13 of the system including the arm, etc., is 2t and T comes to be the integer-fold of (t), the amplitude of the oscillation can be minimized. The change of the inherent oscillation period can be changed by changing the servo system gain only at the period to execute the adjustable speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention includes some non-rigid elements that grip a load at one end of an arm and control the position of the load by driving the other end of the arm with an electric motor. This invention relates to a robot vibration reduction method for reducing load vibration during acceleration/deceleration control of a servo system.

[Conventional technology]

A robot that grips an object (load) and moves it to a specified position is composed of an arm that grips the load, an electric motor that drives the arm, and a servo control system.

There is no problem as long as the arm has high rigidity, but in reality, due to various restrictions, one with relatively low rigidity is used, and its natural vibration frequency is several hertz. When a load is accelerated or decelerated, the impact causes vibrations, and the vibrations may remain. As a countermeasure to this problem, the acceleration signal is filtered using a low-pass filter, but the response speed becomes slow.

[Problem that the invention seeks to solve]

An object of the present invention is to obtain a method for reducing vibrations of the arm and load during acceleration and deceleration of the load while maintaining response speed in a digital servo system for a robot arm including non-rigid elements.

[Means for solving problems]

In the present invention, the vibration of the load is reduced when controlling the acceleration/deceleration of a system including a non-rigid element that holds the load at one end of an arm and controls the position of the load by driving the other end of the arm with an electric motor. In the vibration reduction method for a robot/ ), the period during which acceleration/deceleration is performed so that the acceleration/deceleration time of the system including the load, arm, and electric motor is an integral multiple of A, the unique vibration period of the system. The only feature is that the unique vibration period of the servo system is changed by changing the gain of the servo system.

[For production]

Using the above method, during the acceleration and deceleration time of the robot,
By adjusting the gain of the servo system, the inherent vibration period of the system including the robot arm can be changed so that an integral multiple of the vibration period is equal to the acceleration/deceleration time, and the As a result, vibration of the robot arm can be reduced.

〔Example〕

FIG. 1 shows a block diagram of a control system for implementing a vibration reduction method for a robot as an embodiment of the present invention. FIG. 2 shows a configuration diagram of the robot, and FIG. 3 shows an example of a time chart of the control system shown in FIG. 1.

The control system of the robot shown in FIG. 1 will be explained.

A position command is added to the adder 21 from the left side of FIG. 1, and the difference from the position signal θ1 is determined and supplied to an amplifier 22 having a gain KP. The output of the amplifier 22 is added to the adder 23, and the difference between the output and the speed correction value (output of the amplifier Kvf29) is determined and the difference is supplied to the amplifier 24 having a gain Kv. By controlling this gain Kv, it is possible to change the inherent vibration period of the system including the robot's load, arm, and electric motor.

The output of amplifier 24 is applied to adder 25.

In the adder 25, the output of the amplifier Kif27 is fed back as a current, and the difference between the output and the output of the amplifier 24 is determined and supplied to the amplifier 26 having a gain Ki. Adder 28
Then, the difference between the output of the amplifier 26 and the signal fed back via the amplifier Ke30 is determined and supplied to the integral calculator 31. The integral calculator 31 calculates the coil resistance (ra) and coil inductance (1!a) of the armature of the electric motor.
), and one of its outputs is fed back to the adder 25 via the amplifier 27 mentioned above.

The other output is applied to an amplifier 32 with a gain of Kt.

The adder 33 calculates the difference between the output of the amplifier 32 and the feedback signal indicating the reaction force, and supplies the output to the arithmetic unit 34 . The integral calculator 34 integrates the inertia factor J1 of the drive system as a coefficient to obtain a speed signal a1. The signal d1 is fed back to the aforementioned amplifiers 29 and 30, and is also supplied to an integral calculator 35. The output of the integral calculator 35 is fed back to the adder 21 described above as a position signal θ1, and is also applied to the adder 36. The load position signal θ2 is fed back to the adder 36. The output of adder 36 is applied to amplifier 37 with gain K. Increase @
The output of the device 37 is sent to the adder 33 as a signal indicating the above-mentioned reaction force.
Hefeed back.

The output of the amplifier 37 is further supplied to an integral calculator 38,
It is integrated using the load inertia factor J2 as a coefficient to obtain a load speed signal i2. The signal a2 is further integrated by an integral calculator 39 to obtain a load position signal θ2. The signal θ2 is fed back to the adder 36 mentioned above.

As shown in FIG. 2, the robot includes an electric motor 1 and an arm 2, and the arm 2 moves while holding a load 3. During this operation, the load or arm is driven with a time vs. speed characteristic line 11 as shown in the upper graph of FIG. Correspondingly, the acceleration of the load, etc. changes as shown by line 12 in the lower graph. This change in acceleration causes vibrations if the system, such as the arm, has low rigidity.

When the period during which acceleration is applied is T, and the period of the natural vibration 13 of the system including the arm and the like is 2t, the amplitude of the vibration is reduced by making T an integral multiple of t.

As mentioned above, in order to reduce vibration, the acceleration/deceleration time T needs to be an integral multiple of the value t of A, which is the period of inherent vibration of the system such as the arm, but the acceleration is determined by the capacity of the amplifier. There is a limit because the acceleration/deceleration time is fixed, and it is difficult to change the acceleration/deceleration time due to response speed requirements. Therefore, it is necessary to respond by changing the period of natural vibration. The period of the natural vibration in this servo system can be controlled by changing the gain Kv of the amplifier 24 shown in FIG.

The above servo system is controlled by digital servo,
The gain K of the amplifier 24 is set only during the period when the servo system is accelerated or decelerated.
v can be changed.

〔Effect of the invention〕

According to the present invention, in a digital servo system for a robot arm that includes non-rigid elements, it is possible to reduce vibrations of the arm and load during acceleration and deceleration of the load while maintaining response speed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a control system of a robot that carries out the present invention, Fig. 2 is a diagram showing an example of the configuration of the robot shown in Fig. 1, and Fig. 3 is a time diagram of the control system of the robot shown in Fig. 1. It is a figure which shows a chart. In the figure, ■...Electric motor, 2...Arm, 3...Load, 21, 23, 25, 28, 33, 36.
・・・・・・・・・・・・Adder, 22, 24
, 26 , 27 , 29 , 30 , 32 , 37...
・Amplifier, 31, 34, 35, 38, 39...
・・・・・・・・・・・・ Integral calculator.

Claims (1)

[Claims] When controlling the acceleration/deceleration of a system including a non-rigid element that holds a load at one end of an arm and controls the position of the load by driving the other end of the arm with an electric motor, vibration of the load can be suppressed. In the robot vibration reduction method for reducing vibration, the period during which acceleration and deceleration is performed so that the acceleration and deceleration time of the system including the load, arm, and electric motor is an integral multiple of 1/2 of the inherent vibration period of the system. A robot vibration reduction method characterized by changing the gain of a servo system to change the unique vibration period of the system.