| Surface functional electrical stimulation is a potential method for the rehabilitation of patients with central nervous system lesions.Finding the optimal electrode size and position of the electrode on the forearm for selective control of finger movements are the major challenges for FES applications.Control over the human hand finger motions also provides diverse applications in human-computer interaction.To achieve optimal control of finger movements,selective stimulation was proposed.To this end,a programmable multi-channel surface Functional Electrical Stimulation device based on high-density electrodes was designed.The electrical stimulator generated biphasic constant current pulses(0-40mA)with a varying pulse width(0-500μs)and pulse frequency(1-200 Hz).The stimulation parameters were manipulated by the user interface which was developed as windows form application in C#.The high-density electrodes were screen-printed as a Flexible Printed Circuit.An electrode array of 32 electrode pads with an individual pad size of 1.2 × 1.5 cm was designed.To maintain conductivity,the hydrogel was used as an interface between the copper film substrate on the Flexible Printed Circuit electrode array and the skin.The gap size between the electrodes was kept 2mm to ensure that maximum area under the skin was covered.For automatic determination of stimulation parameters,an algorithm for auto-calibration was developed.The novel automation algorithm was based on the prior knowledge gained through manual stimulation.The algorithm used flex sensors’ data as motion feedback.To validate the performance of the algorithm,a manual repetitive trial for individual finger movement was performed.The whole selective FES system was tested on eight healthy subjects.The auto-calibration algorithm found the optimal electrode pads for the activation of at least 3 fingers for each subject in an isolated manner.The experimental results showed that the proposed system activated the finger movement-related muscles with improved selectivity proportion.The algorithm significantly reduced the required time for the determination of electrode pads and stimulation parameters for optimal selectivity.This thesis is divided into literature review,methodology and preliminary results of the proposed FES system,discussion,conclusion,and future work sections. |
