A Functional Electrical Stimulation System of High-Density Electrodes with Auto-Calibration for Optimal Selectivity

Surface functional electrical stimulation (FES) is a well-recognized technique for motor function rehabilitation of some paralyzed patients. Finding the proper positions of the electrodes on the forearm for selective control of finger movements is a challenge for FES applications. This work developed a FES system towards hand rehabilitation based on customised high-density electrodes in order to achieve optimal selective stimulation. The proposed system is composed of a customised multi-channel electronic stimulator, an electrode array of 32 electrode pads with each electrode pad size of 1.2 cm ×1.5 cm, and motion feedback sensors. An auto-calibration algorithm was developed to determine the optimal stimulation parameters and electrode pads automatically. The algorithm was based on the prior knowledge gained through manual stimulation. The FES system was tested on eight healthy subjects. The results indicated that the auto-calibration algorithm could obtain the optimal electrode pads for the activation of at least three fingers for six subjects in an isolated manner, and the time required for optimal electrode pads and stimulation parameters detection was significantly reduced, demonstrating the potential for finger movement control in hand rehabilitation.