Estimation of External Forces and Moments Acting on the End-Effector in a Singular Configuration of a Robot Arm without a Force Sensor

This paper proposes a method to estimate external forces and moments without a force sensor when the robot is in the wrist singular configuration. External forces and moments are estimated with Jacobian matrix and joint torques by the equation of statics. When the robot is in a singular configuration, however, Jacobian matrix becomes rank deficient and it becomes difficult to obtain estimated values. In the proposed method, external forces and moments are estimated by using the singular value decomposition. Experiments show that the proposed method is valid for estimation of external forces and moments in the wrist singular configuration.