Key Techniques Of Bionic Rehabilitation Hand Based On Multi-Point Continuous Myoelectric Control

The bionic rehabilitation is core ideology in the field of rehabilitation medicine and equipment at this stage. Because of simple structure, fewer DOFs, singleness control strategy, less movement patterns, weak adaptability, poor flexibility and some other shortcomings, the development and application of traditional rehabilitation equipment is severely limited, especially for hand rehabilitation equipment. Simulating the arrangement, structure and size of human hand, bionic rehabilitation hand designed in this paper with multiple DOFs, multiple joints and multi-point continuous myoelectric control is a new type of hand rehabilitation equipment. And its flexible and adaptable structure, as well as its consecutive and biomimetic control strategy plays a positive role to promote research and development of hand rehabilitation equipment. Therefore bionic rehabilitation hand has both great research significance and application value.With the development of science and technology and the increment of patients’needs, the traditional rehabilitation hand with rigid structure driven by motor has turned up bottlenecks in both aspects of research and application. And bionic rehabilitation provides a new theoretical foundation and points out a new research direction of rehabilitation hand. Base on the shortcomings of existing rehabilitation hand summarized in this paper, a new type of bionic rehabilitation hand with rigid and flexible structure driven by gas is designed. It has good passive flexibility, makes up for the deficiencies of the existing rehabilitation hand in the aspect of control strategy and improves the bionic effect of rehabilitation hand.The main research work in this paper is as follows:(1) According to different requirement on the bending property of motion characteristics of human finger joints and limit to the structure size of joint, the single finger basic structure and the body structure of bionic rehabilitation hand have been designed. The single finger basic structure has two joints and two DOFs, while the body structure of bionic rehabilitation hand is designed with five fingers and ten DOFs. The structural parameters and layout scheme are optimized based on layout and actual size of human hand. On this basis, overall control scheme is designed. And characteristic of bionic rehabilitation hand designed in this paper is summarized.(2) A new type of pneumatic bending joint driven by double FPAs is designed to simulate bending movement of human hand. Base on the theory of statics and elasticity, force equilibrium equation of the FPA free end is analyzed. The static model of joint’s bending angle is obtained to analyze the influence of structural parameters on the flexural properties of joint. The simplified model is proposed and its error is analyzed. According to the first law of thermodynamics and the joint’s dynamic equation, joint’s angle dynamic equation is performed. Simulation is carried out to analyze the relationship between structural parameters and bending angle of joint. The result show:when inner pressure of FPA is in0.1Mpa～0.35Mpa, the deviation between actual bending angle and its theoretical value is smaller. With the increment of inner pressure, the deviation increases. When pressure reaches the theoretical maximum value, its corresponding deviation is7.5°and deviation rate is6.8%. Therefore, it can be considered that static characteristics agree with its theoretical model.(3) The feature reconstruction algorithm of sEMG signal is proposed based on the sparse theory. According to orthogonal matching pursuit algorithm, and combined with the adaptive atoms library structured by K-SVD, sEMG signal is decomposed. The relationship between sparse parameters and sparse result is analyzed to optimize the sparse result. Based on feature reconstruction algorithm, the feature of sparse result is extracted and reconstructed. The feature curve is compared with the actual bending angle of joint to verify the conformity of the feature curve, and to provide the theoretical basis for follow-up research. The advantage of feature reconstruction algorithm proposed in this paper can be proved by contrasting with the traditional average amplitude algorithm. And the reason of poor effect of traditional algorithm is analyzed.(4) Based on amplitude power theory, the preprocessing algorithm of sEMG signal is proposed. According to lumped parameter model of sEMG signal, theory evidence of preprocessing algorithm is analyzed. BP neural network classifier is designed for pattern recognition of sEMG signal base on artificial neural network theory and error back-propagation algorithm. The weighted effect of the preprocessing algorithm is proved by contrasting the training results and recognition rate of classifier. And the feature curve of sEMG signal is fixed based on the algorithm proposed.(5) According to characteristics of overall layout and structure of bionic rehabilitation hand, the multi-point continuous myoelectric control method is proposed based on traditional theory to imitate human movement rule. The connection and difference between two theories is elaborated. The mathematical model is deduced based on analyze of mapping relationship between feature parameters of sEMG signal and control signals of bionic rehabilitation hand. The control system is designed in the MATLAB and DELPHI complier environment. Experimental platform is built for experiment of bionic rehabilitation hand control system. The experimental results show:the system can identify the different action parts of the signal. The overall recognition rate is96.33%, while the overall control error is within5%. The average error value of control points is about0.5087°, and the maximum deviation is less than1°.A new type of bionic rehabilitation hand designed in this paper is directly driven by flexible pneumatic actuator developed by our research team. FPA has characteristics of simple structure, easy control, and easy miniaturization of overall structure and so on. It has better passive flexibility. Meanwhile, overall stiffness is ensured by rigid structure of the hand. Compared with the traditional strategy, multi-point continuous myoelectric control strategy is more in line with human hand movement rule. And this strategy not only can be applied to rehabilitation equipment, but also has positive significance for remote operation and bionic operation of other type of robots, such as industrial robot, agricultural picking robot.