Design And Performance Analysis Of Series-Parallel Hybrid Transfemoral Prosthetic Mechanism

Transfemoral prosthetic mechanism is an auxiliary equipment for the amputee to recover their lost motion ability of hip and knee joints,and provides a guarantee for the amputee to carry out their autonomous movement.There are few researches on transfemoral prostheses and the existing knee-ankle prostheses in market have simple structure and single movement function,which will cause asymmetrical gait and secondary injury to skeletal muscles of the amputee.The late beginning of prosthetic technology in China and its technical limitations make the prostheses difficult to meet the requirements of motion function versatility for the amputee.How to propose the design method of prosthetic mechanisms with diversified motion functions and self-adaptive ability to complex road,as well as realize the energy saving objective in their movement,which are the urgent problems to be solved in the structural design of prosthetic mechanisms.Besides,how to evaluate the compatibility between the amputee and prosthetic mechanisms during human-machine interaction after the amputee are integrated with the prosthetic mechanisms,and how to optimize the structural design of prosthetic mechanisms through human function prediction,which is an important problem at human-machine system level.The objective of this study is to restore the autonomous movement ability of the lost knee and ankle for the transfemoral amputee.A kind of configurations of parallel mechanism with human-like motion performance are proposed which combined with the advantages of parallel mechanisms with simple structures,strong bearing capacity and multiple degrees-of-freedom,and a design method was formed for the transfemoral prosthtic mechanism with novel configuration and mechanical self-adaptivity.The feasibility of structural design of the transfemoral prosthetic mechanism and the correctness of its modeling method were verified,the effects of prosthetic mechanisms on human physiological function was explored in human-machine interaction,and the structural design of the transfemoral prosthtic mechanism was optimized on the premise of people-oriented.The control system application of finite state machine based on three closed-loop PI control system was studied in transfemoral prosthetic mechanism.The research results provide the feasible solutions for the structural design of transfemoral prosthetic mechanisms with multiple motion functions and mechanical self-adaptive ability,which is benefit to the development of portable and wearable transfemoral prosthetic mechanisms and even the medical rehabilitation equipments.Specific research contents are as follows:Configuration design of the transfemoral prosthetic mechanism with multiple gait characteristics.The signal data about lower-limbs kinesiology and plantar pressure from healthy subjects were captured and analyzed based on gait experimental testing platform,using the parallel mechanism without spherical pair as the support carrier,a design method of series-parallel hybrid transfemoral prosthetic mechanism was proposed to simulate the multiple degrees-of-freedom motion characteristics of human knee and ankle joints.Meanwhile,due to the series-parallel hybrid configuration,the ankle-foot prosthetic mechanism can be disengaged and used to the transtibial amputee,so that the designed prosthetic mechanism can be used for a variety of lower-limb amputees.Design of bionic energy device and adaptive module.Based on the mapping relationship between human lower-limb kinesiology and energy production of its skeletal muscles,a wearable energy clutchable device conformed to the gait rhythm of knee and ankle energy devices based on multi-link mechanisms were developed.The function of continuous energy storage-release was realized to the transfemoral prosthetic mechanism,which reduce the energy consumption of the prosthesis and also improve its autonomous flexibility and impact ability.Due to the designed mechanical adaptive device,the adaptive ability of transfemoral prosthetic mechanism to the external environment was improved,the kinematic coordination of human-machine model was realized and improve its walking stability.Human-machine modeling and interaction analysis.To explore the physical condition of the amputee when they interacts with transfemoral prosthetic mechanism,a gait-driven human-machine modeling method was proposed,different from the existing models,the relative contributions of human skeletal muscles,ground reaction force and metabolic consumption was taken into account in this model.A more comprehensive and accurate human physiological indicators were explored during the model walking,including human muscles force,muscles activities and metabolic consumption,and the requirements of joints moments and power in transfemoral prosthetic mechanism.The economical metabolic consumption of human was taken as optimization objective,the optimal numerical model between the muscle recruitment method of lower-limbs and the spatial position of prosthetic joints was established to eliminate the joints position error and assembly error in human-machine modeling,the structural design of the transfemoral proshteitc mechanism was improved under the minimized human metabolic consumption.Gait simulator platform construction with multiple motion functions.In order to solve the problem of falling to find a suitable transfemoral amputee,a gait simulator device with multiple motion funtions was designed to imitate the human-like hip flexion-extension and adduction-abduction in the process of the human forward.A series of hip parallel mechanism with high stiffness and multiple degrees-of-freedom was synthesized based on screw theory,the kinematic and dynamical results verified that the parallel mechanism can be used as a hip simulator,and motion modes of hip flexion-extension and adduction-abduction provided a variety of prototype function verification.Control system design and walking function verification of the prototype.Finite state machine control system based on three closed-loop PI control was designed to track the power output of transfemoral prosthetic mechanism in human support phase and its joint position in human swing phase,the simulation results verify the correctness of the theoretical calculation and the feasibility of the designed control system used in the transfemoral prosthetic mechanism.The prototype platform of transfemoral prosthetic mechanism was built and the design scheme of its control system were formulated,the multiple motion modes function of the prototype was verified based on gait simulator,the experimental results showed that the prosthetic knee and ankle joints of the prototype can meet the expected design requirements of multiple motion functions.