Design And Experimental Research Of Soft Dexterous Hands Using SMA-based Artificial Muscles

As a robot's end-effector,the manipulator has always been one of the research hotspots in the field of robotics.With the increase in application requirements and the rise of new materials and new processes,soft humanoid dexterous hands gradually gain the attention of researchers.Compared to traditional robotic hands,the soft dexterous hands usually use flexible materials to make their support and appearance structure and adopt a new type of intelligent drive material to simulate the movement of human muscles,so the flexible dexterous hands are more lightweight,beautiful,safe and flexible.Based on the principle of human hand bionics,this paper uses shape memory alloy(SMA)wire as artificial muscle to design and manufacture a soft humanoid dexterous hand system with high simulation appearance,high fidelity and stable operation,long life,and low cost.The main research contents and achievements of this article are as follows:(1)Bionics research and structure design of soft humanoid dexterous hand.Through the study of human morphology and anatomy of bionics,the key structural parameters of human hands and the distribution of muscles are obtained,providing bionic basis for the design of soft finger actuators and humanoid dexterous hands.Through the test of the mechanical properties of the finger,the characteristic parameters of the finger tapping(such as the striking force frequency,the relationship between bending amplitude and striking force)are obtained.In addition,the bionic mechanism of finger tapping is preliminarily obtained to provide the basic parameters of the pulsed electric heating control algorithm for establishing a "knocking" motion of a soft finger.The SMA wires are used as the driving material,and the finger structure,bending characteristics,and mechanical parameters are obtained through bionics research.The muscle-stretch-skin structure is adopted,and based on the flexible casting and flexible paste techniques,a soft finger actuator and a soft humanoid dexterous hand are designed.A set of integrated circuit board integrated with STM32 controller,MOS tube switch circuit and bluetooth communication module was designed and manufactured to achieve high integration of control system and hardware circuit.(2)Modeling and simulation of kinematics and thermodynamics of the soft finger actuator module.The kinematic model of the soft finger actuator is established based on the SMA phase change kinetics.The influence of the structural parameters such as the number of SMA wires,the distance between the driver layer and the recovery layer on the flexural performance of the finger is analyzed by the MATLAB/Simulink simulation platform to determine the optimal parameters of the structural design.Thermodynamic modeling and simulation of the soft finger actuator is performed by the COMSOL Multiphysics platform.Firstly,the heat transfer and heat accumulation in the working process of SMA wire are analyzed.Secondly,the heat dissipation performance of different material elastic plates is compared.The results show that the spring steel has the best heat dissipation effect.Therefore,spring steel is used as the recovery layer in the new finger actuators.Finally,the cooling effect of the water circulation cooling system previously proposed by the laboratory is verified through the coupling of thermal field and flow field modeling and related experiments.(3)Performance test and related control strategy of soft humanoid dexterous hand.The performances of the soft humanoid dexterous hand are tested,mainly including the relationship between bending performance and parameter d,the soft finger's response time test,the soft finger's tap performance test,the soft finger's working life test,dexterous hand's high imitation gesture test,dexterous hand's percussion action test,dexterous hand's handshake interaction test.Based on the previous SMA resistance self-feedback control algorithm,the PD control strategy is added to achieve long-term retention of the finger state and provide a guarantee for the dexterous hand grasping the object.A gesture recognition interface is developed,and a simple interactive control of the dexterous hand is completed based on computer vision.The soft humanoid dexterous hand is fitted to the Kinova robotic arm.Based on the Tobii eye tracker system,the interactive control of robotic movement is achieved.(4)The performance optimization scheme of output force and displacement of the soft humanoid dexterous hand.Since the output force and displacement of the soft dexterous hand are not easy to control,the assumption of a linear artificial muscle matrix is proposed based on the principle of human skeletal muscles.The experimental verification of this idea is carried out.And the results show that there is a clear displacement and force superposition output phenomenon in the artificial muscle matrix,which proves the effectiveness of the artificial muscle matrix that can independently and controllably achieve force/displacement of the fractional output.Finally,the corresponding matrix control strategy is established.