Workpiece transfer system

A work transfer system, comprising:

• a robot having a hand configured to hold a workpiece at a distal end of the robot and having a sensor capable of detecting external force acting on the hand;
• a balancer connected to the hand that is configured to generate lifting force for lifting the hand in a vertically upward direction;
• a shape measuring device which conducts measurement of a shape of the workpiece;
• and
• a controller which controls the robot and the balancer based on the shape of the workpiece measured by the shape measuring device, wherein
• the controller adjusts a holding position of the workpiece by the hand based on the shape of the workpiece measured by the shape measuring device, and controls the lifting force generated by the balancer so that an absolute value of the external force in a vertical direction detected by the sensor becomes equal to or smaller than a predetermined first threshold;
• the controller is configured to adjust the holding position of the workpiece around a horizontal axis line detected by the sensor;
• a moment of the workpiece becomes equal to or smaller than a predetermined second threshold when the robot holds, using the hand, the workpiece at the holding position;
• the holding position is set based on the shape of the workpiece;
• and
• the workpiece is lifted.