Modeling and control of a 4-ADOF upper-body exoskeleton with mechanically decoupled 3-D compliant arm-supports for improved-pHRI

Abstract Safe physical human-robotic interaction is a crucial concern for worn exoskeletons where lower weight requirement limits the number and size of actuators to be used. A novel control strategy is suggested in this paper for the low degree of freedom exoskeletons, by combining proposed mechanically decoupled passive-compliant arm-supports with active compliance, to achieve an improved and safer physical-human-robotic-interaction performance, while considering the practical limitations of low-power actuators. The approach is further improved with a novel vectoral-form of disturbance observer-based dynamic load-torque compensator, proposed to linearize and decouple the nonlinear human-machine dynamics effectively. The design of a four-degree of freedom exoskeleton test-rig that can assure the implementation of the proposed strategy is also shortly presented. It is shown through simulation and experimentation, that the use of proposed strategy results in an improved and safer physical human-robotic interaction, for the exoskeletons using limited-power actuators. It is also shown both through simulation and experimentation, that the proposed vectoral-form of disturbance based dynamic load-toque compensator, effectively outperforms the other traditional compensators in compensating the load-torques at the joints of the exoskeleton.