Research On Decoupling Control Based On M-G Modal Space For Electro-hydraulic Driven Lower Limb Exoskeleton

With the progress of society and the development of science and technology,exoskeleton robot,as a new robot combining mechanical power and human intelligence,is widely used in military,disaster relief,medical and other fields.Among them,it has become an urgent need in the medical field to assist the paralyzed patients with standing and walking and assist the patients with rehabilitation training along the designated gait path through the lower limb extremity exoskeleton robot.However,the mechanical mechanism of exoskeleton robot leads to its complex nonlinear dynamic model and dynamic coupling between the joints.It is difficult to realize the independent control of each joint channel,which greatly reduces the trajectory tracking performance of the lower limb exoskeleton robot.Therefore,this paper proposes a new decoupling control strategy based on mass and gravity(M-G)modal space sliding mode decoupling control,which can not only realize joint decoupling but also reduce chattering of sliding mode controller.In this paper,the decoupling control strategy of the electro-hydraulic driven lower limb exoskeleton are researched.The main research contents are as follows.1.The structure and movement characteristics of human lower limbs are analyzed.The structural parameters and range of motion of lower limbs are found out,and the freedom and range of motion of lower limb exoskeleton joints are determined.The design scheme of exoskeleton structure is completed.2.The exoskeleton kinematic model is established based on the geometric relationship of the exoskeleton structure.The exoskeleton dynamic model is established based on the Lagrange equation.The valve controlled asymmetrical cylinder model is established based on the electro-hydraulic servo theory.On this basis,the whole model of electro-hydraulic driven exoskeleton robot system is established and lays the foundation for the modal theory research.3.The vibration mechanical equation is established and the essential characteristic of the dynamic coupling of the exoskeleton is analyzed.The M-G modal space structure of the exoskeleton system is constructed.The mapping relationship between the M-G modal space and the physical space is established,and the decoupling characteristics of each channel in the M-G modal space is analyzed.The decoupling conditions of the physical space are studied,and the relationship between the control performance of the M-G modal channel and the physical channel is analyzed.4.The design method of M-G modal space controller is researched.In order to overcome the model error and improve the tracking performance of the modal channel.The M-G modal sliding mode control method is proposed and the stability of M-G modal sliding mode control structure is analyzed by using Lyapunov theory..5.The control system of exoskeleton prototype based on x PC Target is established,and the following experimental verification studies are carrie d out: the decoupling properties of M-G mode space,physical space decoupling conditions and the relationship between M-G mode space and physical space control performance are verified;the effectiveness of the proposed M-G modal space sliding mode controller to improve trajectory tracking performance and suppress chattering is verified.