چكيده به لاتين
Abstract
Paralysis occurs after acute spinal cord injury due to interrupts in the communication link between the brain and peripheral nerves. Functional Electrical Stimulation (FES) utilizes artificial stimulation of motor nerves in individuals with spinal cord injury as a means of restoring function to their paralyzed muscles. Intraspinal microstimulation (ISMS) is a novel approach to FES that shows near normal recruitment order. ISMS can reduce fatigue, has low stimulation current and can produce linear recruitment curve. Different studies has shown the ability of ISMS in producing stepping like movement but closed-loop control of movement via ISMS yet has to be accomplished. The main goal of this study is the closed-loop control of movement by independent control of rat’s hindlimb joints. Besides the effect of stimulation parameters (pulse width (PW), current amplitude (PA), frequency) and stimulation strategy (single-electrode and multi-electrode stimulation) on movement characteristics (selectivity, range of motion, speed and fatigue) has been studied.
The results shows that current amplitude has a bigger effect on range of motion and recruitment curve slope than pulse width. The results shows that electrical stimulation with lower PA activates small and slow muscle fibers while stimulation with higher PA activates large and fast muscle fibers. Selective muscle stimulation is an important issue in the control of movements. This study presents a method for selective stimulation of muscles based on multi-electrode stimulation. The results shows that multi-electrode stimulation of spinal cord can improve range of motion, selectivity, repeatability and fatigue.
This study presents three control structures for control of movements based on multi-electrode stimulation. The tracking error was 7.1% for multi-electrode fuzzy control of ankle joint angle. Sliding mode control has been presented as a robust controller against uncertainties. The mean of tracking errors using multi-electrode sliding mode control were 9.5% and 12.7% for the ankle and knee joints, respectively. Tracking error for multi-electrode stimulation had 100% percent improvements over single-electrode stimulation.
Also in this study a 16 channel implantable neuromuscular electrical stimulator also has been designed and fabricated. This system receive data and power from external module wirelessly and it can control stimulation parameters via PC or external module.
Key Words: Functional Electrical Stimulation, Intraspinal microstimulation, multi-electrode stimulation, fuzzy control, sliding mode control, implantable neuromuscular stimulator
