EMGB-Based Experimental Study Of Motor Function Rebuilding For Paralyzed Limbs And System Design Of Wearable EMGB For Lower Limbs

The restoration of the motor functions of paralyzed patients is a critical issue of rehabilitation medicine.Functional Electrical Stimulation(FES)induces muscle contraction to produce limb movement by applying a current stimulation to the peripheral nerves,motor points,and acupoints,which contribute to the rehabilitation of the motor function.The electromyography-bridge(EMGB)FES utilizes the surface electromyography(s EMG)signal acquired from the agonist muscles of the healthy limb of a paralyzed subject as control signal,then translates it into a corresponding dynamic stimulation pulse sequence containing voluntary motor intent information.The stimulation pulses are then applied to the identified stimulation points to produce muscle contraction.The EMGB-type FES,compared to other FES types,has the advantages of the enhancement of voluntary control of patients,being suitable for early rehabilitation training,and the online control of the stimulation amplitude.However,the EMGB-type FES also needs to resolve the stimulation electrode placement problems as well as other common and traditional FES.The EMGB system for walking developed in this paper has some difference from the EMGB system for upper limb motor functional rehabilitation,which are the control pattern of system and the dynamic determination of the timing of the stimulation pulse output.The specific works of this paper is presented as follows:1)The coordinate systems based on the bone proportional cun(B-Cun)method with respect to the anatomic landmarks were established on the skin surface over the target muscles.Then,applying the current stimulation pulses to scan the grid points to locate motor points for individual finger extension/flexion or knee extension.For the fingers,the movement angles produced by different motor points with different activation thresholds within the current range of the selective stimulation were measured in order to analyze and compare the variation trend of finger angles.For the knee extension,the knee angles produced by the motor points of quadriceps muscle within the specific current intensity range in the different electrode placement modes and different stimulation patterns were recorded,and then these knee angles were analyzed to investigate the variation trend of the knee extension angles.2)The B-Cun method was used to locate the acupoints on the target limb(forearm,hand,and thigh).Then,a certain current stimulation was applied to traverse the acupoints to determine acupoint combinations that induce finger extension/flexion or knee extension.The relative positional relationship between acupoints and motor points was compared and analyzed.The statistical analysis of movement angles of finger extension/flexion or knee extension produced by acupoint combinations and motor points were conducted to explore the differences between the inductions of limb movements.3)To acquire the control signals required for the rehabilitation of the knee extension function,8 single differential s EMG sensors were placed in one row for a total of 13 rows to record the the s EMG signal of agonist muscles during knee extension movement.The RMS value of the s EMG signals of 104 channels were calculated and then plotted as a heat map.This method contributes to the determination of s EMG detection point of quadriceps muscles.4)Healthy subject experiments of the upper limb and lower limb controlled lower limb EMGB were conducted to explore the knee extension motor function rebuilding in sitting posture based on the determined stimulation points(motor points and acupoint combinations)and s EMG detection points for knee extension.The EMGB system used in the experiments was the wired constant-current dual channel system designed by the research group in the early stage.5)Some patients with hemiplegia and incomplete paraplegia often show muscle weakness or paralysis of the ankle joint early after nervous system injury,resulting in failure to standing and walking.Therefore,an alternating s EMG controlled stimulation strategy was proposed for improving the muscle function of lower extremity ankle joints in a sitting posture.6)The walking pattern of lower limb is a kind of alternating periodic movement,so for the EMGB system used for lower limb walking function recovery,the time for applying the stimulation pulse to the target muscles should be determined dynamically in order to make the time of the paralyzed muscle activation in line with the time of physiological muscle activation.An algorithm for dynamically determining the output time of stimulation pulses was finally proposed.7)A wireless wearable EMGB system for motor function recovery of lower extremities was designed to realize synchronous/asynchronous motion control of the knee joint in the sitting posture and walking asynchronous EMGB control of ankle joint in the walking posture.A wireless multi-channel data acquisition system was designed to evaluate the performance of the wireless wearable EMGB system.