Fanuc Corporation

Koichi Okanda

Tetsuaki Kato

Takeaki Aramaki

Soichi Arita

Ryusuke Ogawa

A robot controller issues a command to move a servo tool unit to a servo tool unit detachment position. During this movement, a command is issued to stop power supply to an amplifier of the servo tool unit, and a process of invalidating a disconnection error of a power line and a signal line and a process of invalidating servo parameters are executed. The robot controller confirms that power supply has been stopped, and that the process of invalidating the disconnection error and the process of invalidating the servo parameters have been completed. When the robot arrives at a servo tool unit detachment position, a mechanical servo tool unit detachment process is executed. With the attachment of the servo tool unit, a software process required for attachment is executed during a next movement after mechanical attachment of the servo tool unit.

Servo tool unit attachment and detachment method

A spot welding system using a spot welding gun having a servomotor for driving welding tips capable of suppressing variation of pressing force due to influence of heat generated by welding current to obtain an uniform pressing force. A difference between the temperature T detected by a temperature sensor and an initial temperature Tis multiplied by a coefficient A to obtain a pressing force compensation amount &#x3b1;. A pressing force d estimated by an observer is subtracted from the compensated command pressing force p' and an obtained difference is multiplied by a constant Kto obtain a torque command (current command) &#x3c4; for driving the servomotor to press the objects by the welding tips. Since the commanded pressing force is compensated in accordance with the temperature, a constant and stable pressing force is produced without influence of the temperature variation.

Spot welding system and method of controlling pressing force of spot welding gun

A method of and device for automatically setting and updating a reference position of a welding tip of a servo spot welding gun to automatically compensate displacement of a distal end of a welding tip by abrasion thereof. A movable welding tip is moved towards a stationary welding tip to press the stationary welding tip until an estimated disturbance load reaches a fist threshold, and then moved in reverse direction away from the stationary welding tip until the disturbance load is reduced to a second threshold. The position of the movable welding tip when the disturbance load is reduced to the second threshold is set and updated as the reference position of an axis of the movable welding tip. The first threshold is set to be greater than a frictional force exerted on the axis of the movable welding tip in the motion towards the stationary welding tip, and the second threshold is set to be equivalent to the frictional force. The above setting and updating of the reference position is performed in cycles of spot welding operations to compensate the abrading of the welding tip. Since the reference position is automatically set and updated to compensate the abraded amount of the welding tip, the distal end of the movable welding tip is constantly positioned to a predetermined position for applying a predetermined pressure to the workpiece.

Method of and device for setting reference position for servo spot welding gun

An applied force Td is estimated by an observer. A gain A is multiplied by a value obtained by subtracting the estimated applied force Td from commanded force Fe. From this multiplied value, a product of a speed feedback amount and a gain Kv is subtracted to obtain a torque command. With this torque command Tc, a servo motor is driven. Since a feedback control of the applied force is performed, response is fast, and an applied force between welding tips and an object to be welded can be accurately controlled. Feedback control of an applied force, whose vibration is prevented, can be performed by adjusting the gains A and Kv.

Method for controlling force application with servo motor and appartus therewith

Axes used for posture alignment are selected from the axes of a work coordinate system W and a tool coordinate system T, and an angle of intersection between those selected axes are set. A robot is then driven so that the selected axes intersect with each other by the set angle of intersection in response to a posture alignment instruction, causing the tool to assume a target posture with respect to a workpiece. Further, angles for rotating the work coordinate system about each axis thereof are set, then the robot is automatically moved so that a coordinate system produced by rotating the work coordinate system by the set angle in response to a posture alignment instruction. Further, the tool coordinate system set at a movable part of a tool is automatically reset according to an amount of movement every time the movable part of the tool move, and the robot is manually fed based on the tool coordinate system thus reset.

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Yamanashi, Japan

Koichi Okanda