Analysis and implementation of a 6 DOF Steward platform-based force sensor for passive compliant robotic assembly

The kinematic analysis of a 6-DOF (six-degree-of-freedom) force sensor whose design is based on the mechanism of the Stewart platform is presented. The force sensor is used to measure forces/torques and to provide passive compliance during part assembly. It is mainly composed of two platforms, the payload platform and the end-effector platform, coupled by six spring-loaded pistons whose length variations are measured by six linear voltage differential transformers mounted along the pistons. The forces and torques applied to the end-effector platform are computed by using the inverse and forward kinematic transformations of the Stewart platform, the known spring constants, and the piston length variations. Results of experiments conducted to evaluate the sensing capability of the force sensor used during the mating and demating of space-rated connectors are reported