Research On Mechanism Design And Control Strategy Of The Lower Extremity Rehabilitation Exoskeleton

There is an urgent need for getting timely and effective rehabilitation for patients with hemiplegia or paraplegia. While the shortages of rehabilitation physicians and the outdated rehabilitation equipment are the major obstacles to the recovery of patients. Therefore, the current issues that need to be solved are designing rehabilitation robots to conduct rehabilitation for patients to substitute rehabilitation physicians, and developing effective rehabilitation control strategies. This work focuses two aspects, namely the mechanism design and control strategies of the lower extremity exoskeleton rehabilitation robot, the details are demonstrated below.Based on the human lower extremity movement mechanism, there are two aspects needed to be considered for developing the technical specifications of designing an anthropomorphic lower limb exoskeleton rehabilitation, that is, distribution of joint degrees of freedom and determination of the range of joint motion. By the comparison of lower extremity exoskeleton configurations, a new configuration is proposed to actuate joint rotation. Also, the overall structural design of a lower extremity exoskeleton robot with 6 DOF is presented based on the modular design. In parallel, based on the elastic beam structure and force sensor, a new interactive interface mechanism is designed to acquire interactive force information effectively and provide the basis for control strategies. Furthermore, the static analyses of the key parts are conducted to verify that the components meet the design requirements in terms of strength and stiffness.To analyses the relationship between the pose and the joint angle, a forward and inverse kinematics model of the lower extremity exoskeleton rehabilitation robot is set up. In addition, according to the characteristics of gait rehabilitation, the walking process is divided into two phases, i.e., standing and swing. The corresponding kinetic models are constructed using the Lagrange method, ADAMS-based simulation is performed to verify the accuracies. During the process of planning joint trajectory,researching motor selection and control algorithm, kinematics and dynamics offer the significant references and the theoretical basis.With the usage of Motion Analysis capture system, the human gait can be collected to get the reference trajectory of the robot by filtering and smoothing. On this basis, passive and active rehabilitation control methods are proposed depending on the patient’s rehabilitation phases are, which can help patients carry out step-by-step rehabilitations. In early rehabilitation, the adaptive iterative learning control algorithm is used to conduct tracking control, which is proved to be stable by using Lyapunov-like composite energy function and with good tracking performance by conducting simulation experiments. In the mid-term and late-term of the rehabilitation, a fuzzy adaptive impedance control algorithm is proposed to achieve the patient’s actively assisted training. Also to adjust flexibility of the lower extremity exoskeleton rehabilitation robot, the patient’s condition would be validated through absolute average trajectory error rate, security wall overlap rate and absolute average human interaction force in every period.An experiment platform of the lower limb exoskeleton rehabilitation robot is built to functional test control system software and hardware and the prototype of the robot. Furthermore, a series of experiments are conducted, including passive patient rehabilitation based on the trajectory tracking active patient rehabilitation based on fuzzy adaptive impedance control method. In addition, the reasonableness of the mechanism design and feasibility of our control method have been verified and therefore the expected demands have been fulfilled.