US 5,742,138 AGranted

Control method for servo system with adjustable softness in rectangular coordinate system

AssigneeFanuc Corporation

InventorsTetsuaki Kato, Yukinobu Tsuchida

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Abstract

A control method for a servo system capable of adjusting softness to provide a robot with a soft floating function for each axis of a rectangular coordinate system. A force (Fx, Fy, Fz) acting on a tool center point in the rectangular coordinate system .SIGMA..sub.0 is obtained using a position error in the rectangular coordinate system .SIGMA..sub.0 and set parameters (Kx, Ky, Kz). The obtained force (Fx, Fy, Fz) is transformed into data (Fx.sup.(n+1), Fy.sup.(n+1), Fz.sup.(n+1)) in a tool coordinate system .SIGMA..sub.n+1, using posture data of the robot. Further, according to the Newton-Euler method, premising (Fx.sup.(n+1), Fy.sup.(n+1), Fz.sup.(n+1) =(fx.sup.(n+1), fy.sup.(n+1), fz.sup.(n+1), a torque Ti for each axis is calculated to obtain an input value Ei=Ti/(Kp.multidot.Kv) for a position loop. The input value Ei is input to the position loop to perform the position loop process, and an output of the position loop process is input to a velocity loop process to perform the velocity loop process, to realize the soft floating function.

Claims5

Dependent claims

A control method for a servo system for performing processes including a position loop process and a velocity loop process for each of axes of a robot so as to control servomotors for driving the axes of the robot, said method comprising the steps of:

(a) calculating a force acting on a center point of a tool mounted on said robot in a rectangular coordinate system defined in a working space based on a set of parameter values representing a degree of softness of said servo system in the direction of each coordinate axis of the rectangular coordinate system and a position deviation in the direction of each coordinate axis of the rectangular coordinate system;
(b) calculating a torque Ti (i=1, 2, . . . , n, where n is the number of the robot axes) based on said force calculated in said step (a), using inverse dynamics;
(c) calculating an input value Ei based on said torque Ti calculated in said step (b) for each axis, a gain Kp of the position loop process and a gain Kv of the velocity loop process;
and
(d) inputting said input value Ei calculated in said step (c) to the position loop process for each axis, to perform the position loop process and the velocity loop process for each axis so that said servo system has the degree of softness in accordance with the parameter values.

2 more elements

Dependencies are inferred from the claim text.