A Comprehensive Framework for the Modelling of Cartesian Force Output in Human Limbs

Neuromuscular functional electrical stimulation represents a valid technique for functional rehabilitation or, in the form of a neuroprosthesis, for the assistance of neurological patients. However, the selected stimulation of single muscles through surface electrodes remains challenging particularly for the upper extremity. In this paper, we present the MyoCeption, a comprehensive setup, which enables intuitive modeling of the user’s musculoskeletal system, as well as proportional stimulation of the muscles with 16-bit resolution through up to 10 channels. The system can be used to provide open-loop force control, which, if coupled with an adequate body tracking system, can be used to implement an impedance control where the control loop is closed around the body posture. The system is completely self-contained and can be used in a wide array of scenarios, from rehabilitation to VR to teleoperation. Here, the MyoCeption’s control environment has been experimentally validated through comparison with a third-party simulation suite. The results indicate that the musculoskeletal model used for the MyoCeption provides muscle geometries that are qualitatively similar to those computed in the baseline model.

I. Introduction

Functional electrical stimulation (FES) for artificial generation and support of movements through application of electrical currents represents an integral part in the rehabilitation of neurological patients. In the early phase of rehabilitation, FES is an effective tool in a task-specific, restorative therapy program to foster neurological recovery [1]. In the chronic phase after a neurological disease or trauma, FES may be used as a neuroprosthesis for compensation of completely lost or very weak motor functions. Particularly in individuals with cervical spinal cord injury (SCI) and the associated impairments of the reaching and grasping function, FES has been successfully employed for assistance in activities of daily living (ADL), both using trans-cutaneous [2] and intramuscular electrodes [3].