Recreating planar free-floating environment via model-free force-feedback control

Force-feedback control can be used to recreate a free-floating environment to test Space Robots (SRs). An SR is mounted on a force and torque sensor attached to the end effector of a Robotic Platform (RP), which is controlled to nullify the measured forces and torques. This eliminates external forces acting on the SR through the mount, hence conserving linear and angular momentum of the SR when no external forces are present. The advantage of the proposed method with respect to previous approaches is that free-floating conditions are recreated without any knowledge of the SR's equations of motion, as the only inputs to the controller are the forces and torques measured by the transducer at the mount. The force-feedback control method can also handle external forces such as those arising from contact disturbances and the thrusters without having any SR control input knowledge since the forces and torques that are generated transfer through the spacecraft body into the sensor at the mount. Simulation results collected using the proposed new strategy are compared against previously used free-floating environment recreation methods such as position and orientation tracking control of simultaneous hardware-in-the-loop (HIL) simulation. On average, the comparison between trajectories shows a position RMS error reduction of over 90% and an orientation RMS error reduction of over 96%.