Controller–observer design and dynamic parameter identification for model-based control of an electromechanical lower-limb rehabilitation system

ABSTRACT

Rehabilitation is a hazardous task for a mechanical system, since the device has to interact with the human extremities without the hands-on experience the physiotherapist acquires over time. A gap needs to be filled in terms of designing effective controllers for this type of devices. In this respect, the paper describes the design of a model-based control for an electromechanical lower-limb rehabilitation system based on a parallel kinematic mechanism. A controller–observer was designed for estimating joint velocities, which are then used in a hybrid position/force control scheme. The model parameters are identified by customising an approach based on identifying only the relevant system dynamics parameters. Findings obtained through simulations show evidence of improvement in tracking performance compared with those where the velocity was estimated by numerical differentiation. The controller is also implemented in an actual electromechanical system for lower-limb rehabilitation tasks. Findings based on rehabilitation tasks confirm the findings from simulations.

KEYWORDS:

• Lower-limb rehabilitation
• model-based control
• parameter identification
• controller–observer design
• parallel kinematic mechanism

Acknowledgments

M. Díaz-Rodriguez wants to thank Fondo Nacional de Ciencia y Tecnología e Innovación (FONACIT-Venezuela). Also, we want to appreciate our gratitude to the Editor and the anonymous reviewers for their constructive comments on the paper.

Disclosure statement

The authors declare that the research was conducted in the absence of any commercial, financial or personal relationships that could be construed as a potential conflict of interests.

Additional information

Funding

This work was partially financed by the Plan Nacional de I+D, Comisión Interministerial de Ciencia y Tecnología (FEDER-CICYT) under the project DPI2013-44227-R and by the Instituto U. de Automática e Informática Industrial (ai2) of the Universitat Politècnica de València.