A Functional Electrical Stimulation and Motor-Assisted Trike for Sport Rehabilitation Therapy

Cycling is a widely used rehabilitation method because it is safe and can be adapted to the needs of different users, from elderly to severely disabled people. When practiced outdoors, cycling becomes a model of sport therapy, promoting social integration and psychological well-being. This study aimed to design a Functional Electrical Stimulation (FES) and motor-assisted trike for sport-therapy rehabilitation. A commercially available passive recumbent trike was equipped with a DC brushed motor, an 8-channel neuro-muscular electrical stimulator, an encoder to measure the crank angle and a pair of power meter pedals. For those with no sensation in the lower limbs, a dual branch controller was developed: the electric motor kept a desired target cadence, while FES intensity was modulated to keep a desired target power at the pedals. For those with some residual capability, FES was modulated with a feedforward controller at an intensity level tolerated by the subject, the motor kept a desired target cadence, and the user was asked to voluntarily provide a desired target power through visual feedback. A feasibility study was conducted with two people with Spinal Cord Injury and five subjects without disabilities. Both controllers worked correctly and the setup demonstrated to be flexible and safe. Future work will focus on optimizing the control in order to better combine the motor assistance with the voluntary and/or FES-induced leg movement, and to study the possibility to compensate for movement asymmetry between the two legs, which could be crucial for some users, such as stroke survivors.