Robot system, robot controller, and method for producing to-be-worked material

A robot system comprising:

• a conveyor configured to convey a workpiece at a conveyance speed;
• a robot configured to work on the workpiece while the workpiece is conveyed by the conveyor;
• a speed calculation circuit configured to calculate the conveyance speed;
• a robot control circuit configured to control a working speed of the robot according to the conveyance speed calculated by the speed calculation circuit;
• and
• a camera configured to pick up an image of the workpiece continuously while the workpiece is conveyed by the conveyor,
• wherein the robot comprises an end effector to work on the workpiece,
• wherein the end effector includes a spot welding gun,
• wherein the working speed is a speed of a movement of the end effector,
• wherein an operation performed by the robot comprises a first operation of making a relative speed of the robot relative to the workpiece constant for a period of time,
• wherein in the first operation, the robot is configured to make a leading end of the robot contact the workpiece,
• wherein the robot is configured to perform the first operation on a plurality of portions of the workpiece,
• wherein the robot is configured to work at an initial working speed,
• wherein the robot control circuit comprises a correction circuit configured to correct the initial working speed such that the initial working speed is substantially equal to the working speed,
• wherein the robot control circuit comprises a detection circuit configured to detect a position displacement of the workpiece and a posture displacement of the workpiece based on the image picked up by the camera, and
• wherein the correction circuit is configured to correct, based on the position displacement and the posture displacement detected by the detection circuit, a motion of the robot relative to the workpiece.