Robot path planning method where bending owing to load is taken into consideration

• US 6,157,155 A
• Filed: 03/13/1995
• Issued: 12/05/2000
• Est. Priority Date: 03/16/1994
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Kobayashi, Hirohiko
• Primary Examiner(s): Nappl, Robert E.
• Assistant Examiner(s): San Martin, Edgardo
• Application Number:
  US08/402,606
• Time in Patent Office: 2,094 Days
• Field of Search: 318/568.2, 318/568.22, 318/646, 318/571, 318/634, 318/578, 318/570, 318/572, 318/573, 318/568.1, 364/474.35, 364/474.03, 364/474.28, 364/474.14, 364/474.09, 364/474.36, 395/80, 395/85, 395/87, 395/91, 395/95, 395/96, 901/3, 901/9, 901/15
• US Class Current: 318/568.22
• CPC Class Codes: B25J 9/1664 characterised by motion, path, trajectory planning
• CPC Class Codes: B25J 9/1674 characterised by safety, monitoring, diagnostic
• CPC Class Codes: G05B 2219/39364 Path, correction of path in function of load
• CPC Class Codes: G05B 2219/40523 Path motion planning, path in space followed by tip of robot
• CPC Class Codes: G05B 2219/41167 Control path independent of load

Abstract

The present invention relates to a robot path planning method for determining the path of a robot, taking into consideration the bending effect of the robot path when heavy tools are load onto the robot. Specifically, straight line P'"'"'-Q'"'"' to be actually drawn by the distal end of the robot tool is calculated by using the positions P and Q of the distal end of the tool at the start point and at the end point of the straight line recognized by the robot controller. And, the interpolation points H1'"'"', H2'"'"', H3'"'"', . . . are set on this line P'"'"'-Q'"'"'. Then, the bending amount Δθpj and Δθqj at the start point P'"'"' and at the end point Q'"'"' of this line P'"'"'-Q'"'"' are respectively determined. And, the bending amount at each interpolation point H1'"'"', H2'"'"', . . . are calculated from these bending amounts Δθpj and Δθqj, and the position on the line P'"'"'-Q'"'"' of each interpolation point. Then, the values obtained by subtracting from each interpolation point H1'"'"', H2'"'"', . . . corresponding bending amounts are set as the interpolation points H1, H2, H3, . . . to be actually used in the robot controller.

Claims

1. A robot path planning method where bending owing to load is taken into consideration, comprising steps of:

(a) calculating a linear section to be drawn by a distal end of a robotic tool, by using said distal end of said robotic tool at a starting point and at an ending point of said linear section as recognized by a robot controller;

(b) setting a first plurality of interpolation points on said linear section as calculated in step (a);

(c) determining a bending amount at said distal end of said robotic tool at said starting point and at said ending point, respectively, of said linear section;

(d) calculating said bending amount at said distal end of said robotic tool at each said first plurality of interpolation points, based on said bending amount of said distal end of said robotic tool at said starting point and at said ending point of said linear section as determined in step (c), and set a position of each of said first plurality of interpolation points on said linear section; and

(e) setting a second plurality of interpolation points to be used in said robot controller by subtracting said bending amount at said distal end of said robotic tool at each of said first plurality of interpolation points calculated in step (d), from each of said second plurality of interpolation points of step (e).

2. A robot path planning method using a robot controller, in which bending of a plurality of axes each having an axial value of a robot owing to load is taken into consideration, comprising steps of:

(a) determining bending amount of each axis at a starting point and at an ending point, based on a position data of said starting point and a position data of said ending point and a load parameter of the robot, which bending amount is added to each axial value corresponding to said position data of said starting point and said position data of said ending point, to determine each axial value corresponding to a position of said starting point and a position of said ending point, in which bending is taken into consideration for at least one section to which said position data of said starting point and said position data of said ending point are given;

(b) determining bending amount of each axis relating to said starting point and said ending point, based on said each axial value in which bending is taken into consideration and said load parameter of the robot;

(c) determining a plurality of corresponding coordinate values of the position of said starting point and of the position of said ending point of the robot, based on each axial value in which bending is taken into consideration as determined in step (a); and

determining positions of a plurality of interpolation points on the robot path connecting the starting and ending points given by the coordinate values,

(d) determining said bending amount of each axis relating to said positions of each interpolation point based on said bending amount relating to said starting point and said ending point as determined in step (b); and

(e) determining each coordinate value of each interpolation point as the data which represent target positions for a sequential movement, by calculating each axial value corresponding to an interpolation point based on said positions of said interpolation points, and subtracting said bending amount at each interpolation point as determined in step (d) from each of said calculated axial value.

3. The robot path planning method where bending owing to the load is taken into consideration according to claim 2, in which bending amount of each axis at each interpolation point on the robot path is given in a manner such as that in step (d), the bending amount of each axis relating to said starting point as determined in step (b) changes linearly according to a distance going away from said starting point on the robot path of step (c) to become the bending amount of each axis relating to the end point as determined by said step (b) at said ending point.

4. The robot path planning method where bending owing to the load is taken into consideration according to claim 2, in which bending amount of each axis at each interpolation point on said robot path is given in a manner such as that at said step (d), the bending amount of each axis relating to said starting point as determined in step (b) changes linearly according to a lapse of time which is required to move from said starting point toward said ending point on the robot path of step (c) to become the bending amount of each axis relating to said ending point as determined in step (b) at said ending point.

5. A method of compensating deviations of robot movement due to varying loads placed on a robot, comprising:

1) determining a first traveling path from a starting position to an ending position of a robot that has not been loaded with robotic tools;

2) determining a second traveling path from said starting position to said ending position of a robot that has been loaded with robotic tools;

3) determining amount of displacements between said first traveling path and said second traveling path;

4) determining an amount of angular adjustment to a plurality of axes of said robot that has been loaded with robotic tools so that it travels along said first traveling path.