Design Of Multi-degree-of-freedom Prosthetic Wrist And Research On Synchronized Control

The hand plays a very important role in the daily activities.In normal grip,the wrist is indispensable.Therefore,the study of upper limb prosthesis for disabled individuals is of great significance to restore their normal life.At present,commercial prosthetic wrists have the problems of less freedom and poor dexterity.Therefore,it is necessary to study multi-degree-of freedom prosthetic wrists with light weight and small size.As part of the national key R&D project "Intelligent Upper Limb Prosthesis with Bidirectional Neural Pathway"(Project No.2018YFB1307200),this paper has carried out research on the design and control of multi-degree-of freedom prosthetic wrists,including the following contents:This article first analyzed the movement characteristics of the human wrist,including the range of motion and weight of the human wrist,clarified the needs of the disabled to use prosthetic limbs,and designed the prosthetic wrist indicators based on actual needs.In the mechanism design and configuration selection,it analyzed and compared the advantages and disadvantages of various mechanisms,and finally chose the rotating motion matching differential gear mechanism.Starting from the design index of the prosthetic wrist,it selected the driving source and transmission mechanism.The linear drive was used as the driving source for the flexion/extension and abduction/adduction of the prosthetic wrist,and Crank Rocker Mechanism was used for transmission.The brushless DC motor and harmonic reducer was used in the rotating joint.Sensors configuration made the prosthetic wrists have force and position sensing functions.Then the forward and inverse kinematics analysis and statics analysis of the transmission mechanism were carried out for the designed three-degree-of-freedom wrist.First,the standard D-H parameter method was used to study the forward and inverse kinematics of the three-degree-of-freedom wrist mechanism.The D-H parameter table was established.The position and attitude expressions of the reference point of the wrist end in the base coordinate system were obtained,and the inverse kinematics was solved.In the kinematic analysis of the transmission mechanism,the relationship between the input displacement and the output displacement,and the relationship between the input force and the output force of the differential gear mechanism and the Crank Rocker Mechanism were established.Next,research on the synchronized control of the three-degree-of-freedom wrist was carried out.There is a synergistic relationship between the joint movements of the human wrist.In order to achieve the coordinated movement between the joints and improve the ability of each joint to track the planned trajectory,a synchronized control method was adopted.First,the conversion between movement space and measurement position of the wrist was established,and the mathematical model of the linear drive was established.In the study of synchronized control,starting from the goal of synchronized control,a synchronized error based on cross-coupling was established,which was combined with the position error.The coupling error was defined,and it was used as the feedback of position control.The synchronized control strategy was established based on crosscoupling.Finally,the simulation of mechanism and control were carried out.The kinematics of the mechanism was simulated and analyzed by Adams.The movement range and rotational speed of the wrist mechanism were simulated and verified,and the speed change law of the Crank Rocker Mechanism was simulated and analyzed.Simulink was used to simulate and analyze the synchronized control method.The effect of synchronized control was verified.