| The heavy-duty assisted exoskeleton robot can effectively enhance the wearer’s load-bearing ability,and has high potential application value in field operation,individual combat and other fields.Hydraulic drive is widely used in the field of bionic robots such as exoskeleton because of its high power density and strong adaptability to extreme working conditions.The existing hydraulic exoskeleton mostly adopts centralized power oil source,and the servo valve is used at the joint to control the movement of the actuator.With the development of hydraulic drive technology towards energy saving and high efficiency,it is of great significance to study the decentralized power drive mode using pump controlled hydraulic cylinder.At the same time,higher energy efficiency also enables walking robots to obtain longer endurance time.The research objective of this thesis is the problem of lower extremity exoskeleton driving system and human-machine cooperative motion.The research contents are as follows:Design the structure of lower limb assist exoskeleton.The gait test and analysis system is used to obtain the lower limb joint angle and joint torque data during human walking.Based on this,the motion range,degree of freedom and active joint driving mechanism parameters of the lower limb exoskeleton joint are determined.With the help of genetic algorithm,the installation position and size of the hip joint and knee joint driving hydraulic cylinder are optimized,and the structural design of the negative heavy lower limb assisted exoskeleton is completed.Design of hydraulic drive and control system of lower limb exoskeleton.Based on the human gait data,the load force,load flow,load power and other information of the hydraulic drive system are determined,the calculation and selection of hydraulic system components are completed,the transfer function models of the servo motor and pump control cylinder system in the hydraulic pump control unit are built,and their time-domain and frequency-domain characteristics are simulated and analyzed in MATLAB.The experimental platform of exoskeleton joint pump control cylinder hydraulic drive system is built.By configuring the parameters of outer loop incremental PID controller,the joint position closed-loop characteristics and pressure closed-loop characteristics are tested,and the simulation results are verified.(1)Human computer interaction force control strategy of lower limb exoskeleton based on admittance control model.The mathematical model of admittance relationship in the form of mass,spring and damping is constructed,and the motion model of human lower limb is equivalent to a plane two degree of freedom connecting rod.The dynamic model of lower limb is established based on Lagrange equation,the gravity compensation component in the interaction force between exoskeleton and leg is obtained,and the discrete mapping relationship between the displacement of exoskeleton joint driven hydraulic cylinder and human-computer interaction force is established,the influence law of admittance coefficient on control performance is analyzed by simulation with Simscape tool.Lower limb assisted exoskeleton weight-bearing walking experiment.The lower limb exoskeleton experimental platform was built,and the joint fixed gait following experiment and joint admittance control experiment were carried out to verify the control performance of lower limb assisted exoskeleton following motion.The human-computer interaction force of exoskeleton is measured experimentally,and the admittance parameters are determined.The single leg swing motion experiment is carried out to verify the motion control performance of human-computer interaction force based on admittance model.The exoskeleton walking experiments under different load conditions were carried out,and the exoskeleton assistance performance and assistance effect were evaluated based on the driving system parameters such as load torque and output power. |
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