An upper limb robotic exoskeleton of three degrees of freedom (DOF) is designed for the patients who survived stroke and the elderly who have not enough strength to move their limbs freely. Particular attention is paid to the realization of a intention-driven robotic control approach, by which the robotic exoskeleton can assist the user moving his/her arm freely to where he/she intends to go. A force sensing system made of multiple force sensing resisters (FSRs) is embedded in the robotic exoskeleton. A static force model of the upper limb in a relaxed state is obtained when the user wears the exoskeleton. A hybrid model is proposed to describe the behavior modes of human upper limb motion. Filtering technology is designed to infer the intended moving direction of upper limb based on the measured force information and the static force model. The motion intention of user’s upper limb can be online estimated using the filter and a mode transition detector. Guided by the inferred intention, an admittance control strategy is assumed to control the motors of each DOF. The effectiveness of proposed robotic system and control approaches is evaluated by experiments.

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