| With the rapid development of human society,an increasing number of traffic accidents,work injuries,man-made and natural disasters,as well as war and diseases arise,which makes many able-bodied people physically disabled with amputation.As the most important part of rehabilitation aids,prosthetic knee joints can directly enable the physically disabled to recover from the movement disability to self-walk,thus achieving their physical and psychological social regression.Therefore,the research of prosthetic knee joint has important theoretical significance and application value,as well as great social benefits.To improve the deficiencies of insufficient bionic performance,high energy consumption and low driving efficiency in both the theoretical and practical aspects of the prosthetic knee joint,this paper proposed a new prosthetic knee joint based on the geared five-bar(GFB)mechanism.By means of size optimization of the GFB mechanism to provide the best centrode that most approximate to the centrode of the human knee joint,design optimization and performance analysis of nonlinear parallel and series elastic actuation based on the walking characteristics of the human knee joint,as well as the intelligent control and experimental study of the GFB prosthetic knee joint using the neural network,a new powered prosthetic knee joint of high bionic performance,low power consumption and high driving efficiency features is finalized.The main work of this paper is as follows:(1)Model establishment and size optimization of the GFB prosthetic knee joint.Firstly,the model of the GFB mechanism prosthetic knee joint is established.Then its relative instantaneous center of rotation(ICR)is solved by means of the“Angular Velocity Vector Method”,and its size parameters are optimized by means of the genetic algorithm.The influence of the gear ratio on the centrode of the GFB mechanism prosthetic knee joint is analyzed,and the GFB mechanism prosthetic knee joint is compared with the common four-bar and six-bar mechanism prosthetic knee joints.The study results show that: the GFB mechanism prosthetic knee joint is able to achieve better bionic performance with smaller size,and can fine-tune its centrode by adjusting the gear ratio,which lays a theoretical foundation of the miniaturization,light-weight and customization for the prosthetic knee joint.(2)Research on the walking following characteristics of the GFB mechanism prosthetic knee joint.Firstly,the walking following model of the GFB mechanism prosthetic knee joint is established.Then,based on the collected walking data of the able-bodied,the kinematics features as well as the theoretical gait of the GFB mechanism prosthetic knee joint are analyzed.On this basis,by means of modeling and analyzing the inverse dynamics of the GFB mechanism prosthetic knee in both the stance and the swing phase,its driving characteristics are revealed.The study results show that: the theoretical gait of the GFB mechanism prosthetic knee joint is very close to the ideal gait;there exists a best hinge to drive the GFB mechanism prosthetic knee joint with the minimum driving power.(3)Research on the nonlinear parallel elastic actuation of the GFB mechanism prosthetic knee.Firstly,the nonlinear parallel elastic actuating model of the GFB mechanism prosthetic knee is proposed based on the feature of nonlinear position transformation of two-point connection in the GFB mechanism.On this basis,by means of the general dynamics modeling and solving method which considered the installation of springs in random positions in the GFB mechanism,and the pre-processing that normalized different force conditions and different installation situations of springs,the optimal parameters of the nonlinear parallel elastic actuation are obtained by the improved genetic annealing algorithm with the optimization objective of reducing the driving torque and power of the GFB mechanism.The study results show that: the optimal nonlinear parallel elastic actuation of the GFB mechanism prosthetic knee joint is able to reduce its driving torque and power significantly;compared with the linear parallel elastic actuation,the nonlinear one is able to achieve better performance.(4)Research on the nonlinear series elastic actuation of the GFB mechanism prosthetic knee.Firstly,a new nonlinear elastic actuator using the conjugate cam mechanism is proposed based on the new nonlinear-transmission series elastic actuating theory.Then by taking the weighted minimum of the driving powers,fluctuations of the driving torques and the stiffness of linear springs as the optimization target for the single cam,with the penalty constraints for the cam profile and the minimum radius of its curvature considered,the two-objective Pareto optimal of the conjugate cam mechanism is realized with the use of the improved genetic annealing algorithm.The study results show that: By applying the new nonlinear series elastic actuator in the GFB mechanism prosthetic knee joint,it can achieve the advantages of smaller mechanical error,faster response speed,simpler control,and the phase-discrete driving.(5)Intelligent control and experimental study of the GFB mechanism prosthetic knee joint.Firstly,the prototype of the GFB mechanism prosthetic knee as well as the experimental platform is built.Then,the attitude acquisition and solution of the prosthetic knee joint is implemented by the Arduino,dual MPU-6050 sensors and the FSR pressure sensor,and the electric drive system of the prosthetic knee is achieved by the Maxon Epos 2 controller and the RE40 DC brush motor.By using the Lab VIEW parallel main program integrated with the BP neural network,the intelligent control of the GFB prosthetic knee joint is finally realized.The experiment results show that: the GFB prosthetic knee joint can perform well in the walking function,and is able to provide the gait close to the expected. |
