Simulation and Design of Two Tool Support Arm Exoskeletons with Gravity Compensation

We present and analyze two arm exoskeletons based on a pantograph linkage that allow for the support of 89~N (20~pounds) at the user's hand. Using a pantograph linkage allows for a constant force to be created at the hand in any orientation when a constant vertical force is supplied to the other side of the pantograph. We present several topologies and analyze them based on feasibility of manufacture and ability to provide a near vertical force to the pantograph linkage. Simulations are created using the best topologies and the resulting forces at the hand are reported. The mechanical design of an unpowered (passive) exoskeleton which uses a gas spring mechanism is presented. Additionally, simulations and block-CAD of a powered (active) exoskeleton which uses a motor for the supply of force are presented. The performance of the passive exoskeleton is qualitatively compared with simulations.