A novel spring-assisted modular and reconfigurable robot (SA-MRR) has been recently developed at our laboratory to reinforce its performance, and to enable safe and dexterous operations in human environments. A power spring is inserted between the brake rotor and the motor shaft through a decoupling bearing. With the spring engaged, the working range of the joint is mechanically limited for safe operations, and such a limited working range can be established at any joint position. The safety aspect of the SA-MRR is investigated by operating the robot in a
limited workspace created by activating the spring. The trajectory tracking capability of the SA-MRR is explored by comparing trajectories followed by a conventional MRR and SA-MRR in a restricted workspace, while lifting a heavy payload. Trajectory tracking is performed with various payloads to demonstrate the SA-MRR’s superior payload handling capacity performance due to addition of the spring-generated moment. These algorithms have been implemented on a 3-DOF SA-MRR and numerical simulations have been carried out to investigate the improved tracking accuracy and safety features due to addition of the spring-brake system.