Magnetorheological Effect Based Four-bar Linkage Prosthetic Knee And The Correspondingly Constituted Lower Limb Prosthesis

The lower limb prostheses are the primary apparatuses for above-knee amputees to recover the functions of their legs and appearance,and are the important auxiliary device to allow the above-knee amputees to return confidently to their social lives.As the most important components of lower limb prostheses,the prosthetic knees not only need to meet the basic walking functional requirements but also achieve coordination with the remaining limbs.Relative to the pneumatic or hydraulic prosthetic knees,the prosthetic knees based on magnetorheological(MR)effect have become one of the focus directions as the intelligent prostheses,as they have several obvious advantages such as fast response,controllable damping force,and low power consumption.However,in the existing prosthetic knees based on the MR effect,the commercial MR dampers are usually installed directly on the four-bar linkage prosthetic knees,which not only results in more occupied space but also causes the MR damper to swing relative to the prosthetic shank as the knee’s user walks.Therefore,the principle and method of the structure integration of the MR damper and the prosthetic knee,as well as the correspondingly control method,are worthy to be researched and developed.Aiming at solving the above mentioned problems,the principle and structure of the MR effect based four-bar linkage prosthetic knee(MRFLPK)are proposed and realized by individually integrating the upper and lower link rods of the four-bar linkage with the piston rod and the outer cylinder of the MR damper,and the prototype of the MRFLPK is designed and fabricated.Using the MRFLPK prototype,the MR lower limb prosthesis(MRLLP)is developed.On these bases,the needed damping force of the MR damper of the MRFLPK is simulated and analyzed.The control principle and method for the MRFLPK is proposed and studied.The rapid control prototype system and the experimental system for the MRLLP are respectively developed.On the developed experimental system,the MRFLPK is tested and analyzed.The major researches and innovations in this dissertation are summarized as follows1.In order to take full advantages of the characteristics that the four-bar linkages can simulate instantaneous rotation center of knee joints accurately and the controllable damping of the MR dampers,the principle and structure of the MRFLPK are proposed and realized by individually integrating the upper and lower link rods of the four-bar linkage with the piston rod and the outer cylinder of the MR damper.The upper end of the outer cylinder of the MR damper is unified directly with the lower end of the lower link rod of the four-bar linkage,and the piston rod of the MR damper is connected to the upper link rod via the swing link rod.The integrated MR damper has a double-ended structure.The prototype of the MRFLPK is designed and fabricated.Based on the developed MRFLPK,the MRLLP is developed.The MRLLP is composed of the developed MRFLPK,the prosthetic shank,the prosthetic foot,and the angle sensor.2.The kinematic and dynamic models of the MRFLPK and the correspondingly constituted MRLLP are established.Based on the established kinematic and dynamic models,the needed damping force of the MR damper is simulated and analyzed.The needed damping force of the MR damper is also simulated by the ADAMS software.According to the simulation results,the desired damping forces of the MR damper for controlling the swing of the MRFLPK are analyzed.3.The trajectory tracking control of the MRFLPK is introduced.In order to provide the reference curve for controlling the motion of the MRFLPK,the principle of the Rayleigh oscillator based reference curve generator(RORCG)is proposed and realized.According to the proposed principle of the RORCG,the corresponding experiment system is established.The effectiveness of the RORCG is verified and analyzed.The computed torque and PD feedback control algorithm for the MRFLPK is introduced.4.In order to test the MRFLPK,the rapid control prototype system for the MRLLP is established.The MRLLP is composed of the developed MRLLP,the control system,the angle sensor,and the controllable current driver.When doing experiments,the control system is established using a real-time simulation system(type: dSPACE DS1103).The swing angle of the MRFLPK is sensed by the angle sensor.The controllable current driver transforms the command voltage,which is supplied by the real-time simulation system,into the driving current in the coils in the integrated MR damper of the MRFLPK.5.In order to test the MRFLPK,the thigh simulator,which can simulate the motion of the lower limb of the humen,is proposed and developed.On this basis,the principle of the bio-inspired motion platform system(BIMPS)for testing prosthetic knees is proposed to simulate the actual gaits,and the prototype is fabricated.The bio-inspired control method is used to command the thigh simulator to track the motions of a tester’s thigh based on the real-time motion information of the healthy person acquired by the bio-inspired sensor.The ideal gaits of the thigh simulator and the ability of the prototype of the BIMPS to track the motions of the tester’s thigh is experimentally tested and analyzed.6.On the established experimental system for the MRLLP,the MRLLP with the rapid control prototype system is tested and analyzed.The MRFLPK with different constant currents is experimentally tested.Based on the thigh simulator,the MRFLPK with controlled currents by the control algorithm is experimentally tested in the constant walking speed.Based on the BIMPS,the MRFLPK with controlled currents by the control algorithm is experimentally tested in the acceleration and deceleration motion,respectively.The experimental results show that the MRFLPK with controlled currents by the control algorithm can realize the natural gaits.The research works in this dissertation has laid the foundations for researching and developing MRFLPKs and MRLLPs with the high-performances.