JPH01310889A - Controller for industrial robot - Google Patents

Abstract

PURPOSE:To suppress the destruction of a work by detecting the collision of the work with the external field with high precision by installing a means for outputting a signal for stopping the operation of a robot on the basis of the result of the comparison of the allowable torque which is set by an allowable torque setting means which restricts the output torque of a motor within an allowable torque and the output torque of the motor in drive. CONSTITUTION:The necessary torque of a motor 3 for driving joints is obtained by a calculating means 6 from the holding torque of a joint in the case when a robot is held at a prescribed position and the state of the aimed operation of the robot. The allowable torque is set arbitrarily on the basis of the necessary torque value, and the output torque of the motor is restrained within the pertinent allowable torque by a setting means 7. Then, the allowable torque set by the setting means 7 and the output torque of the motor 3 in drive are compared by a comparison calculation means 10, and a robot stop signal is outputted from a robot stop signal generating means 11 to the robot according to the result of the comparison. Therefore, the destruction due to the collision with the external field of a work, tool, or the robot can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a control device for an industrial locomotive with improved safety.

(Prior Art) When an industrial robot (hereinafter referred to as a robot) performs assembly or transportation, the robot follows a taught path according to a pre-made program and repeats positioning operations to taught points. However, if the size or shape of the workpiece being transported by the robot is different, or if the teaching position and the actual working position deviate due to a malfunction in the robot's peripheral equipment, etc., the workpiece may be hit by a tool or prying may occur. . Then, robots 1
The positional deviation and speed difference with respect to the target operation of ~ will increase within the zarpo-lube of the drive motor, and as a result, the output torque of the motor will increase. Furthermore, work, which is the product of torque and time, also increases.

Therefore, upper limits are generally set for the above-mentioned positional deviation and motor work, and if a collision or prying occurs during robot operation, this upper limit condition is detected and the operation is stopped. There is also a method of detecting a collision of the hand by installing a force or torque sensor in the attachment part of the tool of the robot I-.

By the way, in normal operation of the robot, even if a predetermined load is attached and the robot is operated at a predetermined maximum acceleration and maximum speed, the above-mentioned positional deviation and motor work do not reach their current values. Further, when operating at low acceleration or low speed, there is less torque to accelerate the arm or motor, so the required torque is less, and the margin up to the above-mentioned upper limit is relatively large. Therefore, when the motor is operating at low acceleration or speed, if a collision or twist occurs and the motor torque increases, excessive torque will be transmitted to the arm. Furthermore, the time it takes for the position deviation and motor work to reach the limit values described above becomes longer, so even if the robot detects that the limit value has been reached and stops its operation, the workpiece, tool, etc.
Or the robot I~ is damaged. If the strength of the workpiece or tool is low, collisions cannot be detected and the tool will be damaged. Also,
It is not only uneconomical to provide a force or one-force sensor in the assembly section of a tool, but also requires complicated processing and control of signals from the sensor, and also requires the mechanism and wiring of the tool.

(Problem to be solved by the invention) In this way, in the past, when a workpiece or tool being transported by a four-pounder collides with the outside world or is twisted, an excessive driving force is generated in the robot's joints after the collision. The workpiece, tool or robot mechanism will be damaged.

The purpose of the present invention is to detect with high sensitivity when a workpiece or tool being transported collides with the outside world or is twisted, prevents the generation of excessive driving force after the collision at the joint, and prevents the workpiece, tool, or robot from colliding with the outside. The object of the present invention is to obtain an industrial robot control device that can reduce mechanism damage.

[Structure of the Invention] (Means for Solving Task U) The industrial robot control device of the present invention has a holding torque that stores the torque of the joint drive motor when the robot is held at a predetermined position. Storage means and this memorized retention j
・Required torque calculation means for calculating the required torque of the joint drive motor from the robot's target motion state and the required torque calculation means, and arbitrarily permissible torque calculation means based on the required torque value calculated by the required torque calculation means. A torque comparison calculation that compares the allowable torque set by the allowable torque setting means and the output torque of the motor during driving. and stop signal generating means for outputting a signal to stop the operation of the robot based on the comparison result of the torque comparison calculating means.

(Function) The control device for this industrial robot controls the movement of the joints when holding the robot in a predetermined position.
- The required torque of the joint drive motor for a predetermined motion of the robot is calculated from the state of the target motion, that is, the speed, acceleration, etc. of the arm, and the allowable torque of 1 to By setting the torque, the output torque of the motor is constrained within the permissible torque, and whether the state of being constrained to be equal to the actual operating torque or the allowable torque continues for a predetermined period of time. A robot stop signal is given to the robot according to the comparison result, so that the permissible torque can be accurately controlled.
In addition to being easy to set, it is possible to prevent excessive driving force from being generated in the joints after a workpiece being transported by the robot collides with the outside world.

(Example) Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of an industrial robot control device according to the present invention. The position control means 1 receives a target position input from a higher-level controller (not shown) and a robot
The speed command is output based on the position feedback signal from the servo motor 3 for driving the joints 1 to 1. The speed control means 4 calculates and outputs a torque command based on the speed command from the position control means 1 and the speed feed signal from the servo motor 3.

The holding torque storage means 5 stores the above-mentioned torque command when holding the robot in a predetermined position by storing it in a host controller (not shown).
The information is written to a storage device (not shown) of the roller. The required torque calculation means 6 calculates the required torque of the servo motor 3 from the holding torque stored in the holding torque storage means 5 and the state of the target operation. The allowable torque setting means 7 sets the allowable torque based on the required torque value determined by the required torque calculating means 6 and a setting input arbitrarily inputted from the outside, and sets the allowable torque to the servo motor 3.
The output torque of the motor is constrained within the permissible torque range. The limiter 8 restricts the torque of the servo motor 3 based on the allowable torque from the allowable torque setting means 7 . The current control means 9 controls the torque (that is, current) of the servo motor 3 based on the torque command from the speed control means 4 and the allowable torque setting value from the allowable torque setting means 7. The torque comparison calculation means 10 receives the allowable torque setting value from the allowable torque setting means 7, and
The torque command input from the speed control means 4 indicating the output torque of the servo motor 3 during driving is compared. The robot stop signal generation means 11 outputs a signal for stopping the operation of the robot (ie, the rotation of the servo motor 3) based on the comparison result of the torque comparison calculation means 10. Reducer 12
is for amplifying the output torque of the servo motor 3.

The operation of the robot control device having such a configuration will be described below. When performing teaching playback with Loch I~, when teaching the movement of the robot arm 2, the torque command for holding the robot arm 2 at the teaching point is shown in the holding torque storage means 5 in advance. It is written in the storage device (not shown) of the upper controller that will not be used.

At the time of grayback, a target position input for the robot arm 2 to perform a programmed desired target operation is input to the position control means 1.

Next, the operation of the required torque calculating means 6 will be explained. Generally, if the degree of freedom of the robot is n, then the required torque of the first servo motor 3 of the robot I- can be determined by the following formula.

τmi” Jmi et al., +D□1b□i+τji/Ni・
... (1) However, J□1 is the moment of inertia of the high-speed rotating part (motor),
δmi, "Bi is motor rotational angular velocity, angular acceleration, i/
N i is the reduction ratio of 71!12, D is the viscous friction coefficient of the high speed rotating part (motor, transmission mechanism, etc.), and τ is the joint drive torque.

Here, τ11 is the driving torque vector τ of the joints of the robot.
In the i-th component of fJ <n dimension), τj is expressed by the following formula.

10c <ej,) −=−−−−(2)
However, j ” ffl , 'j is the rotation angle, angular velocity, and angular acceleration vector (n-dimensional) of the robot's joints, M (
e, ) is the inertia matrix, H(e,, m, > is the centrifugal force, Coriolis, frictional force, and G l, ) is the gravity and its out-of-plane force.

By the way, the coefficient matrix in equation (2) is determined by the robot machine and is obtained through identification. Identification requires complex calculations and measurements, and tends to include errors.6 In particular, G (o and I) are not only affected by mechanical friction force, but also mechanical gravity compensation such as springs. When the mechanism is used, the error increases due to variations in the repulsion constant and nonlinear factors.In this embodiment, the required torque τ' of the servo motor 3 is determined as follows.

"mi""miθmi+Dmi"nli+7:M
d i + τ′Jl i/ N i ・・・・
... (3) However, if τhjdi is the above-mentioned memorized holding torque and the robot position is between the teaching point and another teaching point, each teaching point is held!・It is obtained by interpolating from the clock using an interpolation means (not shown). Here, τ'p1 is the i-th component of the robot drive torque vector c1 expressed as the following equation.

...... (4) Next, the required torque τ and the set human power τ calculated as above. The allowable torque τp□1 is set by adding the allowable torque setting means 7Il+ as follows, and the output torque of the servo motor 3 is equal to this allowable torque τΩ.
It is constrained within the upper and lower limits of l1li.

τ, QIIli−τ′1Ili+τoi (upper limit) τ′
−τ (lower limit) ・・・・・・(5)l′llll
01 Furthermore, the torque comparison calculation means 10 detects whether or not the state in which the robot is restrained such that the torque during actual operation is equal to the upper and lower clothes of the above-mentioned allowable torque continues for a predetermined time, and if It is determined that an external force is being applied to the robot due to a collision, a wrenching, etc., and the robot stop signal generating means 11 outputs a stop signal to the current control means and a host controller (not shown) to stop the robot.

On the other hand, the operation during teaching will be explained.

During teaching, the holding torque for holding the robot at a predetermined position is stored in the holding torque storage means 5, and at the same time, the required torque calculation means 6 is used until the next holding torque is stored. is input as is. The effect of G on the required torque calculating means 6 is the same as that described above.

FIG. 2 shows an example of the relationship between the required torque of the motor and the allowable torque described above, where a is the position input of the target operation, and b
is the required torque of the servo motor 3 calculated by the required torque calculation means 6, C is the allowable torque set by the allowable torque setting means 7, and d is the actual driving l·rook of the servo motor 3. That is, when robot 1~ collides with the outside world at point P in Figure 2, the driving torque increases as d', reaches the upper limit of allowable torque at point Q, and is constrained to be equal to allowable torque C. After a predetermined period of time has elapsed, a robot stop signal is issued at point R.

As a result, the control device for industrial robots 1 to 1 of this embodiment provides the following effects.

(a) The holding torque when holding the robot in a predetermined position is stored in the holding torque storage means 5, and this is used to calculate the required torque while the robot is operating, so the required torque can be calculated accurately and easily. can be asked for.

(b) The allowable torque can be set based on the above required torque, so even if the robot collides with the outside world when the drive torque is small, it can be detected with high sensitivity without using a special sensor, and excessive torque can be applied to the robot's joints. This can prevent damage to the robot mechanism and workpiece.

(C) By stopping the operation of the robot when the drive torque reaches the upper limit of the allowable torque for a predetermined time, it is possible to quickly recover from a collision state and reduce damage to the robot and workpiece.

(d) Since the allowable torque can be arbitrarily set from the outside, any allowable torque can be set for any operation.

In addition, in the above embodiment, when calculating the required torque, whether the joint drive torque vector τ' (Equation (4)) is calculated or
The movement of the robot to detect a collision is relatively slow,
When the acceleration is low, the centrifugal force and Coriolis are small, and the inertial force generated by the acceleration of the joint angles of lojo and yto is also small, so the centrifugal force in 1 and the joint drive torque in equation (3) are If the inertia force caused by driving Coriolis and other joints is simplified and calculated, the calculation for setting the allowable torque becomes easier.

Furthermore, in the above embodiment, the allowable torque τ, QIIi is (5)
It has the same effect as an expression or any other function. For example, when the absolute value of the calculated value of the required torque is less than a certain value, the calculation for setting the allowable torque becomes easier even if the allowable torque is set to a constant value.

[Effects of the Invention] According to the present invention, the required torque of the joint drive motor is calculated from the holding torque of the joint drive motor when the robot is held at a predetermined position and the target motion state of the robot. Then, arbitrarily set an allowable torque based on this required torque value to constrain the motor's output torque within the permissible torque, and compare this allowable 1 to torque with the motor's output torque during driving. Since a signal is given to the robot to stop its operation based on the comparison result, the allowable torque can be set accurately and easily, and it can also be used to prevent collisions between the robot, the workpiece or tool being transported, or the outside world. Therefore, it is possible to obtain a control device for an industrial robot that can detect with high sensitivity, prevent the generation of excessive driving force after a collision of robot joints, and reduce damage to workpieces, tools, and robots.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an industrial robot control device of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between required torque and allowable torque of the embodiment. 1...Position control means, 3...Servo motor, 4...
・Speed control means, 5...Holding torque storage means, 6...
- Required torque calculation means, 7... Allowable torque setting means,
9... Current control means, 10... Torque comparison calculation means, 11... Robot l~stop signal generation means, a... Target operation input, b... Required torque of motor, C・
...Allowable I-lux, d, d'...Driving torque.

Claims (1)

[Claims] A speed command is obtained based on a target position input given to the robot arm to perform a target motion and a position feedback signal from a motor for driving joints of the robot, and this speed command and the speed feedback signal from the motor are used to obtain a speed command. In the control device for an industrial robot configured to obtain a torque command based on the torque command and further control the current of the motor based on the torque command, the control device for the industrial robot is configured to obtain a torque command based on the torque command, and to control the current of the motor based on the torque command. a holding torque storage means for storing a holding torque; a required torque calculating means for calculating a required torque in the joint driving motor from the stored holding torque and a target motion state of the robot; an allowable torque setting means for arbitrarily setting an allowable torque based on the obtained required torque and constraining the output torque of the motor within the permissible torque; and an allowable torque set by the allowable torque setting means and the motor during driving. An industrial robot characterized by comprising: a torque comparison calculation means for comparing the output torque with the output torque of the robot; and a robot stop signal generation means for outputting a signal to stop the operation of the robot based on the comparison result of the torque comparison calculation means. Robot control device.