Force Capabilities of Two Degree of Freedom Serial Robots Equipped With Passive Isotropic Force Limiters

Abstract

This paper proposes the use of passive force and torque limiting devices to bound the maximum forces that can be applied at the endeffector or along the links of a robot, thereby ensuring the safety of human–robot interaction. Planar isotropic force limiting modules are proposed and used to analyze the force capabilities of a twodegreeoffreedom (2DOF) planar serial robot. The force capabilities at the endeffector are first analyzed. It is shown that, using isotropic force limiting modules, the performance to safety index remains excellent for all configurations of the robot. The maximum contact forces along the links of the robot are then analyzed. Force and torque limiters are distributed along the structure of the robot in order to ensure that the forces applied at any point of contact along the links are bounded. A power analysis is then presented in order to support the results. Finally, examples of mechanical designs of force/torque limiters are shown to illustrate a possible practical implementation of the concept.