Comparison of Current and Voltage Control Techniques for Neuromuscular Electrical Stimulation in the Anterior Thigh

A comparison between current control (CC) and voltage control (VC) techniques for functional electrical stimulation (FES) with different electrodes was done. A dependency on current of the ohmic resistance of the skin-electrode interface was found. A controllability study shows that the CC offers more controllability since both amplitude and pulse width (PW) of stimulation are suitable parameters for control, unlike VC, where only the amplitude is able to control the output for PWs bigger than 200 mu s. An efficiency study shows that large PWs are electrically inefficient since not all the applied energy is use for neuromuscular or muscular excitation and up to 50% of the energy is absorbed by the tissue. Based on these, basic suggestions for parameter selection are given to minimize the risk of tissue damage and improve electric efficiency at least for our specific set-up.