Stimulation time determination for lower limb FES by using gait event and a "delay".

Lower limb neuroprostheses for motor function rehabilitation, especially the drop foot stimulator, uses sensors to turn on or off stimulus pulse sequence during hemiplegic patient's locomotion. This triggering method with fixed stimulus pulse output control may result in uncoordinated limb movement in the lower limb rehabilitation training. The purpose of this paper was to investigate the reliability of stimulus onset determination using inertial measurement units (IMUs), and a dynamic control algorithm based on gait event detection and walking speed was proposed. In our study, two different equipments were employed to record surface EMG (sEMG) of synergist muscles (tibialis anterior and medial gastrocnemius) and IMU sensor signals. Several detection methods for muscle activity onset-time were compared and analyzed to obtain a suitable onset detection method. A dynamic "Delay" time between heel strike event and muscle activity onset was obtained through an algorithm, and its relationship with walking speed was determined using data fitting.