Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
2000-04-18
2001-11-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S095000, C700S164000, C700S186000, C700S245000, C700S258000, C700S262000, 56, 56, 56, 56, 56, 56, C901S041000, C901S047000, C414S730000
Reexamination Certificate
active
06317653
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a robot control system which is capable of feedback controlling each articulated joint so as to equalize the detected position to a position command. More specifically, the present invention gives adequate compliance characteristics to the robot control system.
The industrial robots are used in various stages of manufacturing, e.g., in an assembling process or in a machining process, in which the robot is often subjected to an operation for pressing a workpiece on a designated surface.
For example, a workpiece needs to be fitted into a chuck of a lathe. To this end, the robot performs a shifting operation of the workpiece in the following manner. First, the robot moves a workpiece toward the chuck and stops it when the workpiece hits the front surface of the chuck. Next, the robot changes the shifting direction of the workpiece (usually perpendicularly) so that the workpiece slides along the chuck surface under a significant pressing force until the workpiece engages in position with the chuck.
In general, each industrial robot handles or carries various kinds of workpieces. Hence, in the above-described shifting operation of the robot, the stop position of the working end at the moment the workpiece hits the chuck surface varies depending on the size of each workpiece.
Using a visual device or a sensor for detecting the size of each workpiece may be preferable to adjust the stop position of the working end of the robot. However, the cost increases.
The unexamined Japanese patent publication No. 6-39760 discloses an impedance control system for feedback controlling a pressing force of the workpiece acting on the designated surface. However, the robot receives a reaction force which varies depending on the impedance parameter and a position change amount. This makes it difficult to finely adjust the reaction force. Furthermore, when the present position is largely offset from the target position, the reaction force may increase excessively.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a robot control system which realizes an easy adjustment of the reaction force acting on the working end of the robot and also prevents the reaction force from increasing excessively.
In order to accomplish this and other related objects, the present invention provides a first robot control system comprising a position detecting means for detecting a present position of each articulated joint of a robot, and an actuating means for feedback controlling the articulated joint of the robot to shift a working end of the robot to a target position based on the present position detected by the position detecting means. According to the first robot control system of the present invention, a reaction force detecting means is provided for detecting a reaction force acting on the working end of the robot. A position correcting means is provided for setting a position correcting amount corresponding to the reaction force detected by the reaction force detecting means. An adding means is provided for producing a target position by adding the position correcting amount obtained by the position correcting means to a given provisional target position. A provisional target position correcting means is provided for obtaining a virtual position of the working end of the robot based on a present target position generated from the adding means. The virtual position is a position where the reaction force detected by the reaction force detecting means becomes equal to a predetermined limit value. A switching means is provided for sending the virtual position obtained by the provisional target position correcting means to the adding means, instead of sending the given provisional target position, when the reaction force detected by the reaction force detecting means exceeds a predetermined value smaller than the limit value.
Furthermore, the present invention provides a second robot control system comprising an impedance control section and an action interrupt section.
The impedance control section comprises a reaction force detecting means for detecting a reaction force acting on the working end of the robot, a position correcting means for setting a position correcting amount corresponding to the reaction force detected by the reaction force detecting means, a target position generating means for producing a target position of the working end of the robot based on the position correcting amount obtained by the position correcting means, a position command generating means for sending a designated position of each articulated joint of the robot based on the target position of the working end, a position detecting means for detecting a present position of each articulated joint of the robot, and an actuating means for feedback controlling the articulated joint to eliminate a difference between the designated position sent from the position command generating means and the present position detected by the position detecting means.
The action interrupt section comprises an action interrupt judging means for checking whether the reaction force exceeds a predetermined threshold. A provisional target position correcting means is responsive to the judgement of the action interrupt judging means for obtaining a virtual position of the working end of the robot when the reaction force exceeds the predetermined threshold. And, a switching means is responsive to the judgement of the action interrupt judging means for sending the virtual position obtained by the provisional target position correcting means to the target position generating means when the reaction force exceeds the predetermined threshold.
Preferably, in the second robot control system, the virtual position is a position where the reaction force detected by the reaction force detecting means becomes equal to a predetermined limit value.
Preferably, in the second robot control system, the threshold is smaller than the limit value.
REFERENCES:
patent: 5291112 (1994-03-01), Karidis et al.
patent: 5451924 (1995-09-01), Massimino et al.
patent: 5668453 (1997-09-01), Muto et al.
patent: 5860900 (1999-01-01), Dunning et al.
patent: 5917726 (1999-06-01), Pryor
patent: 5923139 (1999-07-01), Colgate et al.
patent: 6-39760 (1994-02-01), None
patent: 6-246673 (1994-09-01), None
Ito et al., A standing posture control based on grond reaction force, 2000, IEEE, pp. 1340-1345.*
Lee et al., Force-guided robotic assembly basedon perturbation/correlation, 1997, IEEE, p 75.*
Lee et al., A pertubation/correlation method for force guided robot assembly, 1999, IEEE, pp. 764-773.*
Lee et al., Assembly automation using petubation/correlation, 1997, IEEE, pp. 661-667.*
Lee et al., Assembly of parts with irregular surfaces using actuve force sensing, 1994, IEEE, pp. 2369-2644.
Cuchlinski Jr. William A.
Denso Corporation
Law Offices of David G. Posz
Marc McDieunel
LandOfFree
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