Research On Compliant Human Knee Joint Actuator Based On Smart Materials

With the rapid promotion of science and technology,the new areas of technical exploitation of robotics systems has recently set new trends for the robotic actuation by demanding more versatile systems,which can cope with unpredictable interactions within not well defined environments and actively sharing workspace with the human beings to help deal with various tasks involving human-computer interaction in the environment.Therefore,in order to meet the requirements of its development,robots should have to demonstrate the same level of capabilities embedded in biological systems(humans).However,the joint motion of the robot is generally lack of adaptability and flexibility,it cannot be realized that human neuro-musculo-skeletal system achieves a flexible and stable walking with minimum energy consumption by changing the stiffness and damping in joints by rigid structure.In order to slove the shortcomings of the previous studies,in this paper,the human knee joint is taken as the research object and the intelligent material is used.According to the bionics idea,the design of a new compact compliant actuator with integrated variable physical damping was presented,and carried out the following research work:(1)The domestic and foreign research and application status of humanoid robot flexible joint driving is reviewed,the three key points need for future study is listed.The importance of smart materials is summarized.Then,the concept and classification of smart materials are introduced.The design idea of flexible joint driving by intelligent materials is presented.(2)The mechanism of the knee joint is expounded in the two detail aspects: the physiological structure and the movement form,obtaining the simplified knee mechanical model.According to the performance of Magnetorheological fluid,the design and analysis of MR damper is completed.With the Bingham model,the calculation of the initial damping force of MR damper is completed.(3)The specific part of the compliant actuator in this paper is introduced.According to design and analysis of the former,we design the structure of MR damper,then the driving mode and transmission mode of the actuator are selected to complete the overall structure design.(4)Based on the selected mechanical model,we completed the modeling and simulation of MR damper.Then the kinematic mathematical model of the lower limb is established by D-H matrix.The curve of the angle and torque of the knee in the cycle is obtained,which laid the foundation for the following motion control.(5)The virtual prototype for humanoid knee joint is established.The PI control for Magnetorheological control is proposed.ADAMS and MATLAB/Simullink is chosen to set up joint simulation platform,the simulation experimental data transfer through the MATLAB interface.The analysis results show that the designed variable damping and variable stiffness actuator has good motion flexibility.The last is the development of the prototype,which is convenient for the later experimental research.