Design Principle And Experimental Research Of The Human Knee Joint Energy Harvester

The metabolic energy of the human body is converted into mechanical,thermal and chemical energy when human moves.How to harvest the human joint kinetic energy and convert it into the electrical energy is a challenging problem in the field of wearable robots.Based on the movement principles of the human knee joint,the dissertation presents the design principle of the knee joint energy harvester.The main research contents are as follows:Based on the characteristics of the knee joint in anatomy and the results of human movement experiments with the help of multi-camera motion capture system,the movement and mechanical power characteristics of the knee joint in the sagittal plane in one gait cycle are analyzed.According to the characteristics of the muscle contraction,doing work and metabolic energy consumption and the relationship between the electromagnetic torque and the driving torque of the generator,the main reason of the knee joint energy harvester that can produce electrical power and increase the metabolic energy not too much is found.In order to guide the design of the knee joint biomechanical energy harvester,the dissertation establishes the relationship between the human-harvester parameters and the output electrical power.Based on the arrangement of flexion and extension forces of the knee joint in the sagittal plane,the musculoskeletal system of the knee joint is simplified into a pulley-cable mechanism.The design principle of the pulley-cable knee joint energy harvester is presented.In order to determine the parameters of the harvester,the dynamical model of the mechanical transmission is established.The experimental results demonstrate the advantages of high power density and low metabolic energy cost of the knee joint energy harvester.In order to investigate the influence of the human muscle activity and gait resulting from the knee joint energy harvester,the experimental paradigm of the surface electromyography and gait is established.The experimental results show that the muscle activity and step length do not change obviously in statistics in generating mode compared to that in the normal walking mode.Aiming at the problems of low efficiency and induced electromotive force of the permanent magnet synchronous generator in existing human joint energy harvesters,the design principle of the high efficient axial flux permanent magnet synchronous generator in low speed is presented.In order to solve the problem of high analytical errors of the air gap flux density analysis method based on the Maxwell equations resulting from the big air gap length and small backiron height,a new analysis method based on the Carter’s coefficient and model of the solenoid with current is presented.In order to optimize the performance of the generator and increase the efficiency and induced electromotive force,the analytical model of the printed circuit board wave winding resistance and induced electromotive force,which includes the shape information of the winding,are deduced.With the help of the nondominated sorted genetic algorithm,the optimal design method of the winding is presented.The finite element analysis and experimental results validate the above models and optimization results.The comparative experiments demonstrate the advantages of the axial flux permanent magnet generator in terms of high efficiency and induced electromotive force.