JPS58181590A - Method of controlling robot arm - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a robot arm using a feedback control system.

The position of the tip of an industrial robot's arm has conventionally been detected in the following manner. That is, when the arm a is angularly displaced as shown in FIG. When the arm moves in the axial direction, it is detected by a position detector C such as a linear potentiometer connected to the base end of the arm.

By the way, the tip of the arm aperture is deflected in the manner shown by the @ line, and the amount of deflection varies depending on the arm's own weight, the amount of the workpiece loaded on the arm tip, the operating position of the arm, etc. If such intoxication occurs, the detector btFi
A discrepancy occurs between the position detected by C and the actual arm tip position.For this reason, conventionally, the position of the arm tip was feedback-controlled based on the detector sumata ueO river power signal. It was not possible to accurately position the tip of the arm.

In order to prevent the above-mentioned deflection, K should increase the rigidity of the arm a by enlarging its shape, but this increases the weight of the arm and reduces its controllability. It becomes necessary to take measures such as adding a balance mechanism.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling a robot arm, which enables accurate positioning of the tip of the arm even when a lightweight arm is used.

In order to achieve this object, the present invention detects the amount of deflection at the tip of the arm as an electrical signal, and uses this detection signal to correct the position detection error of the feedback system.

Hereinafter, the present invention will be described in detail with reference to the drawings.

The control force method according to the present invention is implemented using the apparatus illustrated in FIG.

In FIG. 2, the acceleration detector 2 attached to the tip of the robot arm 1 has its detection direction aligned with the direction of the swinging force of the arm 1.

Among the acceleration components of the arm 1 detected by the acceleration detector 2, the low frequency components (for example, below IHz) are considered to be based on the acceleration of gravity. The output signal of the (configured to pass a frequency) is indicative of the gravitational acceleration & for the direction of the swinging force of the arm 1. However, the acceleration of the lever changes sinusoidally in the manner shown in FIG. 4 with respect to the angle change of the arm 10.

Now, if the arm 1 is deflected by acceleration J of gravity as shown by the chain line in FIG. 5, the deflection angle t of this arm is
The angle θ shown in the same figure, which is the angle (--θ') formed by the tangent at the tip na of the bent arm and the arm shown in the unflexed state, is the angle θ shown in the figure, which is the angle θ made by the position detector 4 shown in FIG. (corresponding to the angle detector shown in Figure 1),
Further, since the angle -' is detected from the output signal of the low-pass filter 3, the deflection angle 1 can be obtained from both output signals.

By the way, the amount of deflection δ caused by the deflection of arm 1 is
, that is, the actual size of the arm 1 with deflection (component 6) and the component δ based on the zero weight (concentrated load) K at the tip of the arm 1
, and the deflection angle t4. 1 of each ingredient based on the individual weights listed above.

It can be approximated by the sum of and l. In other words, δkiδ
, +δ*, i=i, +1° Therefore, as shown in FIG. Letting the distances to the end and the tip of the arm be stone and t, respectively, each component of the amount of deflection of the arm 10 at the above installation point J I'*δ,',F
Based on the well-known formula for determining the deflection and deflection of i, δ, ′=-・tl・i, (1
1, so the above deflection t- is ζ-J,
It is expressed as +Jkan-J+'+δ,'+t,·l. Therefore, since the weight of the arm 1 is known, the angle lI shown in the above equation (3) can be calculated from the rotation angle of the base O of the arm 10 obtained by the position detection @2.

The arithmetic circuit 5tj shown in FIG. 3, the output signal of the rotor ζ filter 30 and the output signal (angle signal) of the position detector 4
The above-mentioned deflection angle it is calculated based on the above-mentioned deflection angle it, and the above-mentioned angle 1+ is calculated from the output signal of the above-mentioned position detector 4.Furthermore, based on the results of these calculations, the above-mentioned deflection angle A signal corresponding to the amount JK is output.

Thus, the output signal of the arithmetic circuit 5 is added to the output signal of the position detector 4 at the addition point 6, thereby correcting the output signal of the detector 4. That is, the output signal of the detector 4 indicates the position #Pn shown in FIG. 5, but since the signal corresponding to the deflection amount J is input to the addition point 6, A signal indicating the actual arm tip position P is output.

The output signal of the summing point 6 is inputted to the summing point 7 together with the target value for commanding the position of the arm l, and the summing point 7 outputs the deviation between the two. Then, this deviation is added to the output signal of the speed detector 10 detected at the speed J[1 of the motor 9 at the addition point 8 (1t-+), and then calculated using the well-known PID (Preportbnalintegra
l Diff@r@neiml) is input to the motor 9 via the control circuit 11 . As a result, the arm 1 is rotated via the speed reducer 12 in a direction in which the deviation becomes zero, and thereby the tip of the arm 10 is positioned at the towing position corresponding to the target value by exactly 1X.

Since the deviation f9 is a value that takes into account the amount of deflection J of the arm 10, highly accurate positioning is performed by correcting the amount of deflection aYt.

Note that the output signal of the speed detector IO input to the addition point 8 is the speed I of the motor 9 when the speed of the motor 9 is high.
Acts to lower IL. Also, this detector 10
The output signal of the above PID is
The signal is not input to a differential circuit (not shown) in the control circuit 11.

Above 5N! 111@, the low frequency component of the output signal of the acceleration detector 2 is detected by the O-pass filter 3, and the low frequency component indicating the gravitational acceleration in the swinging direction of the arm 7 is shown in FIG. Alternatively, by using an inclination detector (inclinometer) in place of the acceleration detector 2, the angle θ' can be obtained directly from the output signal of the inclination detector. In this case, the filter 3 is of course not required.

Furthermore, although the F'1PID control circuit 11 is used in the above embodiment, the present invention can also be applied to a feedback system that does not use the circuit 11. It can also be effectively applied to an arm that operates in the manner shown in .

As described above, according to the control method according to the present invention, the position detection error based on the robot arm deflection is corrected.
Even when a lightweight arm is used, the tip of the arm can be precisely positioned and controlled.

[Brief explanation of drawings]

1 and 2 are conceptual diagrams showing the position detection error and deflection of the zero-bot arm, respectively. FIG. 3 is a block diagram showing an example of a device for carrying out the method of the present invention. The figure is a conceptual diagram showing how the gravitational acceleration changes with respect to the direction of the swinging force of the arm, and FIGS. 5 and 6 are conceptual diagrams showing the relationship between the deflection angle and the deflection amount caused by the deflection of the arm. 1.-Robot arm, 2.. Acceleration detector, 3..
-Low pass filter, 4...Position detector, 5...Arithmetic circuit, ■1.-PID control circuit. Figure 1 Figure 2 Figure 4 Figure 5 Figure 8 Figure 6

Claims (2)

[Claims] (1) In a method of controlling a robot arm using feedback control '4, the amount of deflection at the tip of the arm is detected as an electrical signal, and this detection signal is used to correct position detection errors in the feedback control system. A method of controlling a robot arm that allows you to see what you are doing. (2) Detect the acceleration in the direction of the swinging force of the arm at the tip of the arm, extract the low frequency component of the acceleration, and adjust the deflection based on the low frequency component and the position feedback signal in the feedback control system. The method for controlling a robot arm according to claim α)g4, characterized in that the amount is detected.