Research Of Functional Electrical Stimulation Based On BCI Trigger To Achieve Hand Grasping

Background As the disease with the highest disability rate,sequelae of cerebral apoplexy afflicts tens of millions of families,and its characteristics such as long impact time,serious condition and difficulty in complete recovery have become the diseases that people urgently want to overcome.At present,the mainstream rehabilitation method is mechanical rehabilitation,but its characteristics,such as too much pain for patients and small scope of rehabilitation,prompt people to explore other effective methods.Functional electrical stimulation(FES),a new method for rehabilitation,has gradually entered people’s field of vision.Its safety and reliability and good rehabilitation effect stimulate people to study more details of operation and internal mechanism.In this study,the stimulation parameter law and muscle fatigue law of normal volunteers were studied to develop effective methods suitable for clinical treatment.Using the BCI system as the stimulation trigger mode not only realized the remote operation,but also effectively improved the therapeutic effect.Objective 1.Discovering the regularity of stimulation sites and related regularity of stimulation parameters.2.To explore the influence and regularity of electrical stimulation on muscle fatigue.3.Explore the possibility of EEG signal as trigger mode of electrical stimulation system.Method 1.Formulate and locate the coordinate system that fits the forearm by using the tibial and radial protrusions as the starting reference points of coordinates.Four muscles have eight electrode coordinates.Finally,the proportional relationship between the corresponding electrode position and forearm length or the thickest circumference of forearm is calculated respectively to find out whether the proportional relationship is relatively consistent.2.Dichotomy 1 is the basic method to determine the stimulus parameters for different stimulus pulse width,stimulus intensity and stimulus frequency,respectively.Number correlation detection and exploration of the most appropriate range and combination of electrical stimulation parameters;3.A joint study of electrical stimulation of flexor digitorum superficialis,acquisition and analysis of eigenvalues of electrical signals,and acquisition of maximum grip strength.The characteristic value,fatigue threshold and optimum stimulation interval of electrical stimulation-induced fatigue were discussed.4.Using frequency-domain method and signal energy change to analyze and judge the moment of motor imagery and explore the grasp of hand And two methods of distinguishing motion imagination,hand stretching.Result 1.The maximum error of all the electrode positions was 8% after positioning and processing,and the former of the subjects was 8%.The average arm length is 230 mm,so the maximum electrode position error is 1.8 cm.In this experiment,the diameter of the electrode is 2 cm,so it can be judged that the error of the electrode is small enough,which has practical significance.2.The suitable range of stimulation frequency is 25Hz-55 Hz,and the suitable range of current intensity is 3.5m A-8.3m A.The flow pulse width ranges from 0.15 ms to 0.5ms,and the other two parameters are negatively correlated when one of the three parameters is fixed.3.Through comparison,it is found that the overall trend of average rectifier value (ARV)from 0.018 to 0.067 is along with fatigue.Deepening and gradually increasing are suitable for muscle fatigue eigenvalue;when the eigenvalue rises to 0.035,the maximum grip strength will not decrease and the movement will be deformed,so we set it as fatigue threshold;using fatigue threshold to monitor the eigenvalue of normal experiment,we found that the fatigue eigenvalue is stable at 0.001-0.013 after five minutes rest after each stimulation group,because the fatigue threshold is smaller than the fatigue threshold.The rest time is set to five minutes to ensure that the experiment is not affected by muscle fatigue.4.When motor imagery is performed,the time-frequency domain analysis of EEG signals shows that the energy of 10 Hz band is 0.14±0.07.It can be used as a criterion for judging the moment of imaginary movement,because it can be promoted to 0.23±0.12(with statistical difference,P < 0.05,n=50).The energy of C3 channel beta band decreased to 0.14±0.03 during imagery grasping and increased to 0.17±0.05 during imagery stretching(P<0.05,n=6).Conclusion 1.The range of stimulation parameters and the regularity of stimulation sites can play a guiding role in clinical treatment and rehabilitation,which confirms the feasibility of functional electrical stimulation with surface electrodes.2.By revealing the fatigue factors and rules of electrical stimulation under specific stimulation parameters in this experiment,we strictly distinguish the fatigue boundary,and the experimental process will not be affected by muscle fatigue factors at all.3.Using the frequency domain change of 10 Hz and the energy change of beta wave to distinguish different motor imagery tasks effectively,a possibility of EEG controlled stimulation system is proposed.