Research On The Key Techniques Of Load-carrying Lower Extremity Exoskeleton Based On Human-robot Interaction

Lower extremity exoskeleton is a new kind of wearable mechatronics robot with human-robot interaction characteristic.The research on lower extremity exoskeleton has scientific significance and great social application requirement in the fields of rehabilitation medicine,aid to the aged and the disabled,and individual combat,etc.It has been a hotspot in robotics research in recent years.As an important branch of lower extremity exoskeleton,the load-carrying lower extremity exoskeleton can reduce the burdens of wearer's limbs and augment wearer's carrying capacity.The technology challenges of this kind of exoskeleton includes optimized design method for a biomimetic structure that can give consideration to both flexibility and carrying capacity,achieving compliant exoskeleton joint actuation with variable stiffness ability,acquiring wearer's movement intentions and states effectively,and improving the endurance of exoskeleton,etc.Funded by the Nation Natural Science Fund(No.50775072 and No.51275170),this thesis aimed at the issues on under-actuated structure design,compliant joint actuation with variable stiffness ability and synergetic walking control strategy of load-carrying lower extremity exoskeleton.The relevant research has been carried out based on theoretical study,numerical simulation and prototype testing.The main research works are as follows:(1)An optimized adaptive exoskeleton structure design method with variable constraint hip joints has been proposed.By analysing the causes that are responsible for the uncontrollable state of under-actuated joints in the heavy loaded condition,the configuration of adaptive structure has been studied.The flexibility and bearing capacity of adaptive structure has also been demonstrated.(2)A kind of compliant exoskeletal joint actuation method with variable stiffness ability has been proposed,and a unidirectional variable stiffness hydraulic joint actuator has been developed.The torque control and passive stiffness control of exoskeleton knee joint has been realized by using a variable gain PID control strategy based on the theoretical model analysis.(3)A kind of active/passive hybrid walking control strategy with a control state machine based on poses and gait has been proposed.By study the stiffness adjusting behavior of human's biological joint,the control state machine based on poses and gait,and joint control modes corresponding to the states has been established.The exoskeleton walking mode switching between active and passive has been realized?and this led to a reduction in energy consumption of exoskeleton joint actuation.(4)A load-carrying lower extremity exoskeleton prototype actuated by variable stiffness actuators has been developed.The performance of the unidirectional variable stiffness hydraulic actuator has been tested.The feasibility of the walking control strategy and the carrying capacity of the prototype has been experimented and verified.The results of research and experiments indicated that the proposed adaptive exoskeleton structure design can meet the requirement for flexibility in lower extremity movement Force analysis indicated that this design has a bearing capacity at about 90%.The developed unidirectional variable stiffness hydraulic actuator has good performances in torque control and passive stiffness control of joint,and it can satisfy the requirement for variable stiffness compliant actuation of exoskeleton joints under an experiment condition with 26kg.preload.By using the proposed active/passive hybrid walking control strategy with the control state machine based on poses and gait,the experimental prototype can realize load-carrying walking with wearer synergistically.The results of level walking trial indicated that the experimental prototype can support about 80%of all carrying weights including itself and preload,and it can improve the pose and gait of wearer during load-carrying walking.The research results of this thesis have significant engineering application values to the performance improvement of load-carrying lower extremity exoskeleton.