Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1997-04-24
1998-07-21
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
31856813, 31856811, 395 84, 395 99, 901 7, 901 9, G05B 1900, B25J 922
Patent
active
057839220
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This application is a 371 of PCT/JP96/02379 filed Aug. 26, 1996. The present invention relates to a control apparatus for an industrial robot, and more particularly, to a robot controller for improving safety of an operator in performing a lead-through teaching operation.
BACKGROUND ART
A small-sized robot and a robot having a balanced structure with respect to gravity (e.g., painting robots) often employ a teaching method in which an operator operates the robot by holding and moving a teaching handle mounted on a hand portion of a robot to thereby teaching the robot, and this method is called lead-through teaching. The following two method are known as the lead-through teaching. and a torque command for a servo control unit for drive motors of robot axes is set to zero by software processing while the servo control unit is kept in an operative state, to thereby enable the lead-through teaching. robot axes is set in an inoperative state by outputting an emergency stop signal and the mechanical brakes are released, to thereby enable the lead-through teaching.
However, in the method (1) where the servo control unit is kept ON, since the teaching handle is not provided with means i.e. an enable device for immediately and surely stopping the robot on an occasion where the robot makes an unexpected motion due to an erroneous operation of the servo control unit in the operative state, the operator cannot promptly cope with such an unexpected motion of the robot.
In the method (2) where the teaching operation is carried out while effecting the emergency stop, the unexpected motion of the robot resulting from an erroneous operation of the servo control unit can be prevented, but since the dynamic brakes of servomotors are automatically set effective by outputting the emergency stop signal, the operator is required to exert a great force to move the robot to be burdened with a heavy load in the lead-through teaching. To solve this problem, it is necessary to provide an additional circuit for electrically disconnecting the dynamic brakes from the servomotors in the lead-through-teaching to thereby make the dynamic brakes ineffective and also setting the servomotors inoperative, to cause an increase of cost.
Furthermore, according to the conventional methods, as the brakes remain released all the time in the lead-through-teaching, a robot having an imbalanced structure with respect to gravity will cause such problem that the robot arm greatly declines downward due to gravity when the operator releases the teaching handle.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a robot controller permitting an operator to perform a lead-through teaching easily and safely.
According to the present invention, an enable device of a deadman switch is provided on a teaching handle, thereby permitting the operator to stop the robot at any time.
A robot controller of the present invention comprises a main body having a servo control unit for controlling respective robot axes and a power source for supplying electric power to the servo control unit, and a lead-through-teach control circuit.
The lead-through-teach control circuit includes a servo on/off switching means for switching on and off the power supply from the power source to the servo control unit, a brake switching signal output means for outputting a signal for switching the mechanical brake to be effective/ineffective, the deadman switch provided on the teaching handle, and a lead-through-teach enabling switch provided on the main body.
When the lead-through-teach enabling switch is made effective and the deadman switch is operated by the operator, the brake switching signal output means outputs a signal for setting the mechanical brake ineffective and the servo on/off switching means turns on the power supply to the servo control unit. When the lead-through-teach enabling switch is turned effective and the deadman switch is not operated by the operator, the brake switching signal output means does not output the signal for
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Hashimoto Yoshiki
Tanabe Yoshikiyo
Fanuc Ltd.
Ip Paul
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