Mechatronic design of a 3 degrees of freedom parallel kinematics manipulator with integrated force plate for human balance evaluation and rehabilitation✰

One of the main sequelae of stroke is hemiparesis or partial hemiplegia. This condition causes patients to undergo lengthy rehabilitation processes to recover balance and gait. Thus, it is required to have tools to systematize rehabilitation tasks while monitoring the evolution of the patient over time. This paper presents a new prototype based on a 3PRS parallel kinematic manipulator with a force plate in the end effector to rehabilitate and evaluate balance by measuring the Center of Pressure of the patient, a widely studied parameter in the field of posturography. The prototype has been designed to be able to measure in a reliable and repeatable way and, as it is a medical device, it includes design considerations related to ease of use, visual feedback and safety. The paper describes the kinematics, dynamics, mechatronic modelling and mechanical design of the parallel kinematics machine, as well as the design of the force plate in charge of determining the location of the Center of Pressure. Also, a formulation is proposed to correct the influence of the inertial and gravitatory forces on the top plate during the motion of the platform on the measurement. Finally, the prototype has been evaluated experimentally to compare the motion with the developed models and to determine the precision and robustness against noise and motion related effects.