Robot control scheme

• US 5,594,309 A
• Filed: 06/15/1994
• Issued: 01/14/1997
• Est. Priority Date: 06/15/1994
• Status: Expired due to Term

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: Jang, Wan-Shik, McConnell, Kenneth G.
• Primary Examiner(s): Cabeca, John W.
• Application Number:
  US08/260,305
• Time in Patent Office: 944 Days
• Field of Search: 318/632, 318/573, 318/574, 318/568.11, 318/568.12, 318/568.2, 318/568.22, 901/2, 901/14, 364/474.16, 364/474.19, 364/474.28, 364/474.35, 364/474.12, 395/88, 395/89
• US Class Current: 318/568.22
• CPC Class Codes: B25J 9/163 learning, adaptive, model based, rule based expert control
• CPC Class Codes: B25J 9/1651 acceleration, rate control

Abstract

A simple open loop control scheme that minimizes both robot response time and the resulting residual vibration while requiring little computational effort through the intelligent use of conventional servo control technology and the robot'"'"'s vibration characteristics.

Claims

1. A method of controlling a moving robot arm to minimize vibrations, comprising the steps of:

determining a maximum step distance the robot arm can move in a single step;

determining a total task distance the robot arm is required to move to complete a specified task, wherein the total task distance is less than or equal to the maximum step distance;

applying a series of discrete step inputs of varying magnitudes in a timed sequence to the robot arm, the series comprising;

applying a first step input of a magnitude corresponding to approximately one-half the total task distance;

measuring the time it takes the robot arm to move one-half of the total task distance, wherein a measured time and a measure velocity are determined;

estimating robot arm damping using the measured time and the measured velocity;

calculating and applying a second step input magnitude and application time and a third step magnitude and application time, wherein the magnitude and application time of both the second and third step inputs are based on the estimated robot damping, and further wherein the third step input magnitude is approximately equal to the magnitude of the first step input less the second step input magnitude.

2. The method of claim 1, wherein the specified task is fixed.

3. The method of claim 1, wherein the specified task is variable.

4. The method of claim 2, wherein the total task distance is included in a predetermined set of instructions for minimizing vibrations of the robot arm.

5. The method of claim 3, wherein the total task distance is estimated by a human operator to correspond to the variable task as perceived by the operator.

6. The method of claim 5, wherein the operator closes a loop in an open loop operator-controlled system in response to the operator'"'"'s perception.

7. A method of controlling a moving robot and to minimize vibrations, comprising the steps of:

determining a maximum step distance the robot arm can move in a single step;

determining a total task distance the robot and is required to move to complete a specified task, wherein the total task distance is greater than the maximum step distance;

applying a series of discrete step inputs of varying magnitudes in a timed sequence to the robot arm, the series comprising;

analyzing the total task distance to determine a constant velocity displacement and to estimate a linear rise time;

applying a first step input of a magnitude resulting in the highest constant velocity, the first step input having a magnitude of the maximum step distance divided by two;

measuring the time it takes the robot arm to move one-half the maximum step distance;

measuring the robot arm velocity at one-half the maximum step distance;

estimating robot arm damping using the measured time and the measured robot arm velocity;

applying a linear input motion to provide for linear motion of the robot arm based on the actual robot arm velocity at the one-half maximum step distance; and

calculating and applying a second step input magnitude and application time and a third step magnitude and application time, wherein the magnitude and application time of both the second and third step inputs are based on the estimated robot damping, and further wherein the third step input magnitude is approximately equal to the magnitude of the first step input less the second step input magnitude.

8. The method of claim 7, wherein the specified task is fixed.

9. The method of claim 7, wherein the specified task is variable.

10. The method of claim 8, wherein the total task distance is included in a predetermined set of instructions for minimizing vibrations of the robot arm.

11. The method of claim 9, wherein the total task distance is estimated by a human operator to correspond to the variable task as perceived by the operator.

12. The method of claim 11, wherein the operator closes a loop in an open loop operator-controlled system in response to the operator'"'"'s perception.