Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1998-06-10
1999-11-30
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318591, G05B 1904
Patent
active
059948647
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a control apparatus for a robot which executes operations while switching between a position control and a compliance control.
Further, the present invention relates to a compliance control apparatus for a robot and the like, more particularly to a compliance control apparatus for a robot which is capable of limiting a developing force of a servo motor for driving joints based on set values for a force and a torque at a working coordinate system. More particularly, the present invention relates to a compliance control apparatus for a robot which is capable of flexibly following an external force when it is applied thereto, by limiting a gain of a position speed control system or by limiting a developing force of a servo motor for driving joints based on a torque limitation value. More particularly, the present invention relates to a compliance control apparatus which controls a gain of a position speed control system or limits a developing force of a servo motor for controlling joints by torque control, whereby changing a flexibility of a compliance control system in an instrument for controlling the robot for an external force. Furthermore, the present invention relates to a compliance control apparatus of a robot of a servo control which is capable of monitoring a servo deviation during compliance control of a robot and interrupting an operation or changing the kind of an operation to another when the operation is not performed normally.
BACKGROUND ART
FIG. 1 illustrates a position/speed control system of a motor which has been widely used in controlling joints of a robot. Reference symbol s denotes a Laplace operator.
In this position/speed control system, a speed control loop gain Kv111 and a position loop gain Kp110 is set to be as high as possible, in order to perform a positioning in opposition to friction and external force. Furthermore, an integrator 113 is arranged in parallel with a proportional operator 112 whereby control is performed so as to improve its characteristics. With such a control system, the tip of the robot can be accurately positioned at their target positions even under conditions of external force.
However, the foregoing robot has no ability to cope with usage for performing an operation while absorbing a strong force applied from the outside. For example, in a case where the conventional position control robot aims to work in operations to flexibly receive the force applied from an external machine and in the usage of holding and pushing of parts by the robot, the accomplishment of the operations will be difficult.
Specifically, when operations involving a contact with works are performed in such control system, an output value of a speed control loop, that is, a torque reference value becomes large thereby creating an over load state when a positional shift of the works occurs, due to a gain set to a large value in order to enhance rigidity and action of the integrator. Thus, the operation execution will be difficult. In order to cope with such problems, a force control system has been adopted, in which either a float instrument for absorbing the force of an action or an exclusive use instrument such as an RCC having a mechanical flexibility is provided in a tip of the robot, or a force sensor is employed [Prior art No. 1]. For a method of performing a compliance control without adding a special instrument to the robot, a method for reducing a servo gain has been disclosed in Japanese Patent Application Laid Open No. 6-332538 [Prior art No. 2, see FIG. 2]. Moreover, a method capable of setting the flexibility in an operation coordinate system has been disclosed in Japanese Patent Application No. 7-20941 [Prior art No. 3, not shown].
The prior art No. 2 concerns a flexible servo control method which moves a driven body by means of human power, the driven body being driven by a servo motor and is kept away from obstacles. In this method, when a compliance control starts, the position gain Kp110a and the proportional gain Kv11
REFERENCES:
patent: 4985668 (1991-01-01), Nakazumi et al.
patent: 5241250 (1993-08-01), Nagasawa et al.
Inoue Yasuyuki
Nagata Hideo
Kabushiki Kaisha Yaskawa Denki
Leykin Rita
Shoop Jr. William M.
LandOfFree
Robot controller does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Robot controller, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Robot controller will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1676960