Research Of A Dual Stage Bending Dexterous Robotic Hand With EMG Control

In order to meet the requirement of heavy load and high precision,traditional rigid dexterous robotic hand have been lucubrated.With the improvement of application requirement and severer environment,soft dexterous robotic hand has been paid attention gradually.The difference between soft and rigid dexterous robotic hand are mainly reflected in material、drive mode、structure design.active accommodation and so on.The material of soft dexterous robotic hand mostly have excellent chemical stability,unaffected by lights temperature or other environment changes.Different from traditional electromagnetism actuator,soft dexterous robotic hand select smart material like EAP、Dielectric elastomers、Ionic polymer metal composite、IPMC as drive mode,these smart material compatible with soft material and they were design as composite structure.The composite structure are also take the responsibility of support and execute part beside of deformation.Soft material based on electric field can realize self-feedback control system,reduce the dependence on sensors,tight structure also provide surplus space for additional functions.When soft dexterous robotic hand collide with other environment objects,it can absorb impact energy and reduce the damage of environment object,these character decide soft dexterous robotic hand has more outstanding adaptation.The essence of EMG signals is the accumulation of motion potentials of muscle fibers in time and space,its application in the biomedical field is typically mature.Nowadays its body motion recognition and surface EMG signal decomposition can be used in the field of human-computer interaction,providing a more natural,convenient and efficient control,more applications in prosthetic control,mobile device control,sign language recognition,combat command and other fields.Compared with the traditional visual images and data gloves,EMG signal control of the soft dexterous robotic hand doesn’t rely on the high precise sensor system,the system structure and design are more simplified,it isn’t vulnerable to strong light,reflection and other effects,image process means large amount of data and long processing time,EMG signal control are more smooth and natural.This paper designs a dual bending dexterous robotic hand based on EMG control,focus on three aspects:soft composite structure,dual stage bending deformation and EMG control.The main research contents and achievements are as follows:(1)Research on bionic design and fabrication technology of soft dexterous robotic hand.The analysis of the human hand structure,design of the skeleton-tendon-muscle finger structure model,each finger is an independent movement unit,including the rigid metacarpal structure and soft composite phalanx structure,size and parameters are based on bionic design.The flexible phalanx structure includes the composite structure of the driving layer,the recovery layer and the soft layer,and the design of the continuous deformation body based on the shape memory alloy wire is realized.According to the characteristics of human joint movement,designed hinge bending structure,it is responsible for the relative movement of the phalanx and metacarpal.The design of the external bone of the metacarpal bone makes the action of grasp more natural and powerful.In the process of fabrication,the rigid metacarpal structure is not only used as a support structure,but also as a part of mold and connected with soft composite phalanx structure.Layered pouring ensures the multi-layer structural characteristics of the finger driver,and ensure the controllability of distance between the drive layer and the recovery layer.Integration of communication unit,control unit,power supply and soft dexterous robotic hand.(2)Kinematic analysis and thermodynamics simulation modeling of soft composite finger.Soft composite finger is a continuous deformation,different from the rigid rod connection,the D-H method for modeling analysis can’t be applied.The bending movement in this paper is divided into dual stage,the hinge bending structure and the soft composite finger.Bending angle and the displacement of the actuators are used to describe the deformation.The relation between bending angle、displacement and shrinkage of SMAs are analyzed.According to the theoretical shrinkage change of the SMA wires,the distribution point cloud are realized in MATLAB.The shape memory effect and superelasticity of SMAs were analyzed,and the alloy wires used in this paper were subjected to DMA and DSC tests.Based on the finite element method,the thermodynamics analysis and modeling of soft composite finger actuator is carried out.(3)The motion performance and output force experiment of soft dexterous robotic hand and the gesture realization with EMG control.Test the ability of dual stage bending system and analyze the deformation range.Research the influence of the hinge bending structure and the preload setting on the deformation of the five actuators.Combining the experiment results with theoretical analysis.Analyze the influence of length of the shape of the shape memory alloy wire,the length of the phalanx bone,the length of the phalanx bone and hinge bending structure on the bending force output of actuator.Introduce the control principle and experimental device of EMG signal,and expound the theoretical feasibility and advantages.Realizing the cooperation between EMG signal acquisition device and soft dexterous robotic hand with Bluetooth communication,adjusting PWM wave duty cycle to ensure the five actuators has the same motion period.Complete the experiment of gestures realization of soft dexterous robotic hand with EMG control and ensure real-time synchronization and continuous,each gestures have been decomposed in the state and time of the movement.Exploring the realization of the complex gesture with EMG control and the feasibility of the artificial prosthesis control.