JPS59187484A - Drive for arm of industrial robot - 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 an arm drive device for an industrial robot that requires trajectory control at a constant linear velocity, such as an adhesive application robot.

As a method for driving the arm of this type of industrial robot, a driving method for digitally positioning the arm has been developed. In this drive method, as shown in Fig. 4, the difference between the position command value that gives the rotation angle corresponding to the preset target position and the position detection value corresponding to the rotation angle of the arm becomes zero. A D/A conversion (digital-to-analog conversion) output voltage of speed command value data corresponding to the difference is applied to a servo motor (4) (hereinafter referred to as motor) via a drive circuit. Also, the motor (
The speed in 4) is also constantly detected from the position detection value, and this detected speed value is compared with the speed command value. When the motor reaches a speed higher than the speed command value due to the influence of inertia, etc., the difference is returned. is applied, and the voltage supply is suppressed. In the arm drive method described above, when an attempt is made to move the arm at high speed along a predetermined trajectory, the voltage supplied to the motor increases in accordance with the position command value, until the motor follows this voltage and rotates. The error from the position command value during this period also increases accordingly.Especially when driving the arm of an articulated robot, the follow-up characteristics of each arm to the position command value are different, so the arm movement appears as a composite movement of each arm. There are drawbacks such as the trajectory of the tip of the device deviating from a predetermined trajectory.

The present invention aims to eliminate the above-mentioned drawbacks and to accurately move the arm along a predetermined trajectory even in high-speed arm trajectory control.

Examples will be described below with reference to the drawings. In Figure 1,
(1) is a single articulated industrial cobot, which has a first arm (2) and a second arm (3). The first arm (2) is held rotatably around the column (5) by a first servo motor (4) (hereinafter referred to as the first motor), and the upper part of the first motor (4) is A first pulse encoder (6) is attached to detect the rotation angle of the first arm (2) according to the angle. Said first arm (2)
A second arm (3) is held at the tip of the arm (3), which is rotatable by a second servo motor (8) (hereinafter referred to as "second motor") about the first rotating shaft (7).

Further, a second pulse encoder (9) is attached to the upper part of the second motor (8) so as to detect the rotation angle of the second arm (3) according to the rotation angle of the second motor (8).

Furthermore, a working unit (work unit) is provided at the tip of the second arm (3).
(10) is installed, and this work unit (1
0) is configured such that the first arm (2) and the second arm (3) are respectively moved to a desired position by driving the first motor (4) and the second motor (8).

The industrial robot l=(:l) has an arm drive device (11) for each of the first arm (2) and the second arm (3), and has a first motor (4) and a second motor (8). (10) is configured to control the movement of the work unit (10). (Hereinafter, the first arm (2) has a dual function as a puller.) The position control loop includes a position command generator (12) that sends out a position command value corresponding to the target position of the first arm (2) as a digital value. ), a subtraction section (13) that looks at the difference between the position command value of the position command generation section (12) and a position detection value corresponding to the rotation angle of the first motor (4), and the output of the subtraction section (13) as the speed It has a speed converter (14) that converts it into a command value, and an integration counter (I8) counts the output from the first pulse encoder (6), and the value becomes the position detection value and is converted to the subtracter (14). 13).

The speed control loop includes a speed detection section (19) that differentiates the position detection value to obtain a speed detection value, a subtraction section (20) that takes the difference between the speed command value and the speed detection value, and converts the value of this difference into an analog voltage. The motor is comprised of an I)/A converter (16) that converts the voltage into an I)/A converter (16), and a drive circuit (17) that drives the first motor (4) according to the analog voltage.

Furthermore, a differentiation circuit (21) for differentiating the position command value is connected to the position command generation section (12), and the output of this differentiation circuit (21) is passed through the addition section (22) to the position command value. It is configured to be added to the subtraction unit (13) together with the value. Differential constant Kl of the differentiating circuit (21)
is the transfer constant of the speed detection section (19) of 3 and the speed conversion section (1
4) is equal to the ratio of 2 to the conversion constant of Kl = 3
/ is set to 2.

Therefore, when the drive device (11) is shown in FIG. 3 as a block diagram of the transfer function, the equivalent transfer function G of the part (a)
I(S) is expressed as follows.

Gl(S)=KI S+ 1 KIS: Transfer function of the differential circuit Next, the equivalent transfer function G2(S) of the part (b) is expressed as follows.

3S: Transfer function of the speed detection section 4: Conversion constant T of the D/A converter and drive circuit (5/S2: Transfer function of the motor, pulse encoder, and integration counter Here, if you increase the value of 3 for the constant, The denominator time constant is 1
/ becomes 3・Kl・K5(1, transfer function G2 (S)
is approximated as follows.

1 Further, the transfer function G3(S) of the part (C) can be expressed as follows using the approximate transfer number G2(S).

1<2: Conversion constant of speed converter Therefore, the equivalent transfer function Go(S) between the position command room Xr and the detected position value XO is expressed as follows in the above equation.
Since Kl = 3/2, the position command value X' and the detected position value XO are equal regardless of the frequency of the position command value Xr.

In other words, if the differential constant is set equal to 1 to 3/2, then when the position command value changes from time to time, the position The differential amount of the command value is extra supplied, and the speed deviation in position control is reduced. Therefore, it is possible to make the locus of the work unit that appears as a composite movement of each arm (2×3) coincide with a predetermined locus. The differentiation function is realized by storing the current value and the value one pulse before each in two registers that store input data in synchronization with clock pulses, and calculating the difference between these two values. can do.

As explained above, the present invention corrects the speed of the position command value by adding the differential value to the position command value that changes from time to time, so it is possible to reduce the speed deviation that occurs in position control. , it is possible to not only improve the tracking characteristics of each arm alone, but also to reduce errors in the trajectory of the work unit given as a composite motion of a plurality of arms.

[Brief explanation of drawings]

FIG. 1 is a front view of an industrial robot according to the present invention, FIG. 2 is a block diagram of the present invention, FIG. 3 is a block diagram using the transfer function according to the present invention, and FIG. 4 is an arm showing a conventional example. It is a block diagram of a drive device. (1) Industrial robot, (2) 1st arm, (3) 2nd arm, (4) 1'+j-bo motor (5> pillar, (6) 1st pulse encoder, (7) 1st rotation axis , (8) Second servo motor (9
) second pulse encoder,

Claims (1)

[Claims] In an industrial robot that has multiple arms that are driven by the rotation of a motor, a pulse encoder that detects the rotation angle according to the given position command value and the rotation of the arm so that the tip of the arm moves along a desired trajectory. Compare the position detection value from the pulse encoder, and further compare the speed command value corresponding to the difference with the speed detection value from the pulse encoder,
An arm driving device characterized in that an output of the difference is applied to a motor via a drive circuit, and a differential value of the position command value is added to the position command value.