Research On The Bionic Hand Based On The Surface Electromyogram And Control Strategy

Surface electromyogram(EMG)is the comprehensive performance of potential muscle action on the surface of the skin.It is a kind of non-stationary signal,and the strength is usually proportional to the degree of muscle activity.Therefore,it can be used to analyse the movement intentions transmitted by the muscle,such as the posture and force of the wrist and finger.The myoelectric hand is a kind of artificial hand that decodes the surface EMG signals characteristics of the residual limb and controls the motion of the bionic dexterous hand.Because of the advantages of flexible control,convenient use,and strong intuitiveness,the myoelectric hand device is a modern bionic upper limb solution with research and development value.At present,due to the high price,low accuracy of gesture recognition,susceptibility to external interference,and poor adaptability for patients,myoelectric hand can't fully satisfy the needs of patients for artificial prosthesis.By improving the "dexterity","robustness" and "instinct" of the myoelectric hand,the amputees can increase the autonomy and independence in daily tasks.The main research contents and conclusions of this paper are as follows.(1)The multi-channel and high-precision surface EMG acquisition module is developed according to the characteristics of surface EMG signal.The resolution is 16 bits,the sampling rate is 2 khz,the common-mode rejection ratio is less than 70 db,the short-circuit noise is less than 1.5 uv.This module provides a high-precision signal source for analysis and recognition based on surface EMG.(2)The recognition framework of GFI-EMG was proposed to realize the gesture and strength recognition of hand joints based on surface EMG signals.In order to improve the recognition accuracy of gestures based on surface EMG signals,a new CWT-EMGNet Pro model was proposed for gesture recognition,and the recognition accuracy of 8 kinds gestures was reached to 96.79%.(3)As to the problem of multiple disturbances of multi-finger grasping objects,robust anti-disturbance coordinated control for multiple fingers was proposed.The disturbance observer and adaptive control methods are used to weaken the common time-varying disturbances and the random disturbances,respectively.The stability of the control model was analysed through the Lyapunov stability theory,and its effectiveness was verified by numerical simulation.(4)According to the state equation of random switching saturation control system,two theorems of the stability judgment for a kind of random switching system with the saturation control were proposed based on the Gronwall inequality and matrix theory.It can effectively solve the problem of random system switching and input saturation in the process of grasping objects by artificial hands.(5)A virtual 3D simulation training platform was established using Muscle Skeleton Modeling Software(MSMS),which can promote patients to adapt to the control of myoelectric hand as soon as possible.In order to build a test system for myoelectric hand,the various modules of the prosthesis have been developed,including the acquisition module of surface EMG,the force sensor,the electrical stimulation tactile feedback module and the mechanical structure of the prosthesis.A novel threedimensional microconformal graphene electrode for ultrasensitive and tunable flexible capacitive pressure sensors was developed,and the high-performance capacitive pressure sensor with high sensitivity(7.68 k Pa-1),fast response(30 ms),ultralow detection limit(1 mg),was obtained.This type of tactile sensor with high flexibility and high stability improve the tactile detection sensitivity and response speed of the artificial hand.To sum up,a high precision acquisition module of surface EMG was developed firstly,and then the attitude and intensity recognition algorithm based on surface EMG signal was studied,and the anti-interference coordinated motion control algorithm of artificial hand was researched.Finally,the simulation training and test system was built.This study provides the theoretical principle and technical means for the realization of the high-performance myoelectric hand.