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A modified implanted drop foot stimulator that allows cyclic modulation of the stimulation pulse-width during gait has been developed. Stimulation was on two channels of a four-channel 12 polar cuff electrode. The stimulator allowed modulation of stimulation pulse-width, between 0 and 255µs, on both channels throughout the swing and stance phases of gait. Stimulation was applied between 17 and 40Hz. The clinician can specify an infinite range of stimulation profiles on a desktop TM computer, using a user-friendly LabVIEW interface. The desktop program generated a stimulation profile table of 100 values, which was then downloaded to the drop foot stimulator. As each phase of gait imposed different biomechanical demands on the ankle dorsifiexor muscles, different stimulation intensities were desirable, throughout gait, to match these demands. Moreover, as the gait of each person with hemiplegia is unique, the biomechanical demands imposed throughout the gait cycle for each user of a drop foot stimulator are unique. This stimulator architecture allowed the clinician to, specify stimulation intensities individually, at each phase of the gait cycle for each drop foot stimulator user. The stimulator was evaluated on a male hemiplegic subject. It was used to increase the stimulation pulse-width by 150% at 5% of gait cycle prior to heel strike. The system performed well, with the ankle angle at heel strike increasing by 5° owing to this increased pulse-width. [ABSTRACT FROM AUTHOR]

Finite state control is an established technique for the implementation of intention detection and activity co-ordination levels of hierarchical control in neural prostheses, and has been used for these purposes over the last thirty years. The first finite state controllers (FSC) in the functional electrical stimulation of gait were manually crafted systems, based on observations of the events occurring during the gait cycle. Subsequent systems used machine learning to automatically learn finite state control behaviour directly from human experts. Recently, fuzzy control has been utilised as an extension of finite state control, resulting in improved state detection over standard finite state control systems in some instances. Clinical experience over the last thirty years has been positive, and has shown finite state control to be an effective and intuitive method for the control of functional electrical stimulation (FES) in neural prostheses. However, while finite state controlled neural prostheses are of interest in the research community, they are not widely used outside of this setting. This is largely due to the cumbersome nature of many neural prostheses which utilise externally mounted gait sensors and FES electrodes. FES-based control of movement has been subject to the constraints of artificial sensor and FES actuator technologies. However, continued advances in natural sensors and implanted multi-channel stimulators are broadening the boundaries of artificial control of movement, driving an evolutionary process towards increasingly human-like control of FES-based gait rehabilitation systems. [ABSTRACT FROM AUTHOR]