Research On Control System Of Single Joint Lower Limb Assisted Exoskeleton

Assistive exoskeleton robot is a wearable device mainly aiming to strengthen human body.The research object in this paper is the exoskeleton robot designed for knee joint.The main work in this paper is as follows:(1)Designing the whole control strategy for the knee joint exoskeleton.First,the law of human lower limb movement in normal gait is researched.Then According to the motion of knee joint,we propose four control modes,including zero control,active power,passive power and servo control mode.The core is the active power control mode,which is divided into three stages according to the thought of anthropomorphic: event triggered,desired trajectory generation and impedance position control.(2)Building the model of human joint.At first,we establish the model of human skeletal muscle spring-contraction based on Hill model.We assume that the contraction state of muscle can be divided into three stages,including constant contraction,isometric contraction and isometric contraction.Then,the mechanical properties of skeletal muscle were analyzed in detail.At last,we apply skeletal muscle model into a simple two link model of human knee joint and simulate the motion trajectory of knee joint under the action of expected muscle tension.(3)Designed the knee joint exoskeleton controller,realized the impedance position control of the active power control mode.First,the human machine system of the knee joint is introduced.Then,the Human-Robot interaction is analyzed.At last,we employ the impedance control strategy based on force feedback in order to reduce the stiffness of the assistive exoskeleton robot,which has a characteristic of viscous damping.At last,experiments on the whole assistive exoskeleton robot system are conducted.The result shows that the gait period can be accurately recognized through plantar force sensor.What's more,the force feedback impedance control leads to an compliance tracking of the desired position.To sum up,the active power control mode of the knee joint is studied in this paper,and the flexible control of the knee joint is realized.