| The hand is one of the most critical moving organs of the human body,and it is also the basis of many social customs.The loss of one or two hands will significantly impact the life and heart of patients and significantly reduce their quality of life.Currently,the only way is relying on engineering and technical means to develop bionic artificial hands for patients who have lost their hands to help them restore the appearance and function of their hands as much as possible.Due to the highly complex structure of the human hand,it is still a challenge to design and manufacture a bionic artificial hand that can perfectly replace the human hand.There is still a limitation in tactile perception,structural design and optimization,and human-computer interaction of current prosthetic hands.For the problem that the practical prosthetic hands still lack fingertip tactile sensor with rich functions and high integration,a fingertip tactile sensor with all elements integrated into the distal phalanx is designed.The tactile sensor consists of a single polyvinylidene fluoride film and a single force-sensing resistor,then they are both wrapped into the polydimethylsiloxane,moreover,all elements were embedded into the distal phalanx.The proposed fingertip sensor can effectively measure the static pressure,identify the surface texture of objects,and identify the contact point location.The contact point location is achieved by pattern recognition,and the accuracy of contact point identification can reach more than 94% on 5 position with a spatial resolution of about 5 mm.For the poor dexterity of the thumb of the existing artificial hands and the lack of quantifiable optimization design method of the linkage driven hands,a novel quantitative metric to evaluate the grasping ability is proposed,then a bionic hand with a novel “311”thumb configuration is designed by using the optimization design method.The thumb of the bionic artificial hand has an extra pronation-supination joint between the adductionabduction joint and the flexion-extension joint.In this way,the thumb has an accompanying pronation during adduction.This movement can increase the contact area between the thumb and other fingers during opposition.To further improve the grasp quality and performance of the prosthetic hand,a new quantitative metric to evaluate the grasp quality of the prosthetic hand is also proposed.Then the geometric parameters of the linkage fingers have been optimized by maximizing the grasp quality.Experimental results showed that the grasping ability of the optimized prosthetic hand can be improved by more than 10%compared with the experience-based design method.For the robustness of the human-computer interaction control system of the prosthetic hand under the interference of electrode skin contact state change and user arm posture change,a novel hybrid surface electromyography(sEMG)-force myography(FMG)sensor is designed.The designed sEMG-FMG sensor adopts a floating metal dry electrode,which can collect the sEMG signal and FMG signal at the same position synchronously.Experimental results show that based on the designed sEMG-FMG sensor and the traditional pattern recognition methods,the gesture recognition system can maintain an accuracy of more than 98%(six types of gestures)when the electrode-skin impedance is exceptionally high.Based on the designed sEMG-FMG sensor,a sequential decision algorithm is proposed to improve the robustness of human-prosthesis interaction under the interference of arm position change.The algorithm uses the gated unit network for classification and the state transition model for output correction.The experimental results show that the designed sEMG-FMG sensor and the proposed sequential decision algorithm can effectively improve the robustness of the human-prosthesis interaction control system while the posture of the arm is changing.Generally speaking,this paper proposed an intelligent bionic prosthetic hand system with various fingertip tactile sensing capabilities,dexterous 5-joint thumb structure,anthropomorphic grasping behavior and mode,and robust human-machine interactive control system.Based on these studies,a bionic prosthetic hand system prototype is developed and tested. |
