Deformable Object Manipulation – Study on Passive Tracing by Robot

Deformable object manipulation is important for robots, especially home service robots. This is because unlike factory robots that handle rigid objects most of the time, these robots also need to be able to handle soft objects like clothes, rubber, paper etc. This paper proposes a unique tracing method for clothes manipulation by robots. The tracing method is used to reveal a second corner of a rectangular towel for spreading purposes, assuming that a first corner has been successfully grasped. Tracing in this paper's context is tracing the towel's edge, with the robot movement based on feedback from sensors. Using tracing method to find a second corner has been proven to be efficient in finding a second corner next to the first corner and not apposite it, resulting in the robot properly spreading the towel. The clothes manipulation system consists of two robot arms equipped with robot grippers, a CCD camera and an image processing board. Passive tracing is a method where the tracing gripper is static while the gripper holding the first corner maneuvers according to the feedback from sensors inside the static gripper so that it pulls the towel appropriately for the static gripper to trace the edge of the towel. Movement pattern is based on the sensors feedback inside the static gripper. Basically, the movement pattern is divided into two: inward the towel when the static gripper is too near to the edge of the towel and away from the towel when the gripper is too deep inside the towel. Force control is also applied to the static gripper during tracing so that it doesn't grip the towel too hard or vice versa. The CCD camera is used from time to time to check whether the static gripper has reached the second corner or not. Tracing experiments were conducted to evaluate the proposed method.