Functional Characteristics of Pneumatic Muscle Actuated Rehabilitation Equipment for the Joints of the Inferior Limb

Applying passive exercising as part of the recovery programme of patients with post-traumatic disabilities of the bearing joints of the inferior limbs requires the development of new high performance equipment. Human-friendly rehabilitation devices characterized by variable stiffness entail a structure including compliant actuators. Variable stiffness actuators are designed and implemented because of their ability to minimize large forces caused by shocks, and to safely interact with the user. Bio-inspired actuation systems, like pneumatic muscles, meet such requirements, due to their adaptive compliant behaviour, materialized by the possibility of continuous stiffness variation. The paper presents a variant of rehabilitation equipment the novelty of which consists in the utilization of compliant (soft) fluidic actuators of linear type and variable stiffness. The construction of this equipment is presented, the structure of its positioning system, its performance, as well as the motion characteristics, revealing its advantages compared to equipment endowed with electric-mechanical linkages. The proposed rehabilitation equipment benefits from a cost efficient, simple and robust construction, and allows the programming of single or multiple cycles of exercises.