US 4,530,062 A · Method and apparatus for controlling industrial robots

Abstract

An industrial robot control method and apparatus having a pulse distributing circuit for executing a pulse distribution operation on the basis of positional command data from taught data to generate distributed pulses, a pulse coder for generating a feedback pulse each time the industrial robot moves a predetermined amount along the Z-axis, an error register for storing the difference between the number of distributed pulses and the number of feedback pulses, and positional control circuitry for positionally controlling the industrial robot in such a manner that said difference approaches zero, compensation being effected for an amount of bending .DELTA.Z of an arm when a workpiece of weight W is gripped. The industrial robot control apparatus includes a memory for storing an amount of bending .DELTA.Z.sub.o of the arm when a workpiece having a predetermined weight W.sub.o is gripped at an arm length l.sub.o, an arithmetic circuit for computing an amount of bending .DELTA.Z when a workpiece of weight W is gripped at an arm length l, said computation being performed using .DELTA.Z.sub.o, l.sub.o, W.sub.o, l and W, and an adding circuit for adding .DELTA.Z and an incremental commanded amount of movement Z.sub.d along the Z-axis and for delivering the sum of the pulse distributing circuit, the pulse distributing circuit generating distributed pulses corresponding to (Z.sub.d +.DELTA.Z), whereby a positional error due to bending is corrected.

Claims12

Dependent claims

In an industrial robot control method for actuating an industrial robot in accordance with taught data, said robot having an arm of variable length, the improvement comprising the steps of:

measuring and storing beforehand an amount of bending .DELTA.Z.sub.o of the arm when a workpiece having a predetermined weight W.sub.o is gripped at an arm length l.sub.o ;
computing an amount of bending .DELTA.Z when a workpiece having a weight W which differs from said weight W.sub.o is being gripped at an arm length l, said computation being performed using said stored amount of bending .DELTA.Z.sub.o as well as additional parameters including l.sub.o and W.sub.o ;
and correcting the position of the arm on the basis of said computed amount of bending .DELTA.Z.

In an industrial robot control method for controlling an industrial robot in accordance with taught data and for controlling the position of a variable-length arm of said industrial robot by executing a pulse distribution operation on the basis of positional command data from the taught data, said method being of the type which includes the steps of storing in an error register the difference between the number of distributed pulses provided by said pulse distribution operation and the number of feedback pulses generated each time the industrial robot moves by a predetermined amount, and DA-converting said difference and controlling the position of the arm in accordance with the DA-converted output, the improvement comprising the steps of:

measuring and storing beforehand the amount of bending .DELTA.Z.sub.o of the arm when a workpiece having a predetermined weight W.sub.o is gripped at an arm length l.sub.o ;
determining and storing beforehand a table of corresponding relationships between said difference stored in the error register and the weight of a workpiece;
reading an actual workpiece weight W using the difference stored in the error register;
computing an amount of bending .DELTA.Z when a workpiece having a weight W is gripped at an arm length l, said computation being performed using said stored amount of bending .DELTA.Z.sub.o as well as additional parameters including l.sub.o and W.sub.o ;
and correcting the position of the arm on the basis of said computed amount of bending .DELTA.Z.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for controlling industrial robots

Life of this patent

Method and apparatus for controlling industrial robots

Life of this patent

Abstract

Claims12