Research On The Control Method Of Lower Limb Exoskeleton Walking Aid Robot

Regaining normal walking ability is an expectation for patients with lower extremity movement disorders,but the current technology can not fully meet their wishes.It is a problem to be solved urgently to help these people get the ability to walk again.The lower limb exoskeleton robot is a wearable intelligent device,which can not only enhance the strength of people,but also assist people to walk.When assisting the elderly and patients with spinal cord injury to walk,most exoskeleton robots need a caster walker or crutches or other devices to maintain balance.And the use of a caster walker or crutches requires users to have certain upper limb strength,and it is easy to make people feel tired.In order to solve the problem of stability in walking aid and to liberate the upper limb of the user,a method of walking aid control is studied in this paper.The method of the combination of pre-programmed control and on-line correction is adopted in the walking aid control.The robot drives the user to walk with the planned gait.On this basis,the software can get the center of gravity(COG)of the system in real time and adjust the joints angles to correct the error between the actual and planned COG value,realizing the closed loop control of the COG and ensuring the stability margin of the robot system.The main contents of this paper are as follows:Research on the static stable gait planning method for lower limb exoskeleton robot.Gait is the basis of robot motion.For the user with weak or no sports ability,the gait of the lower limb exoskeleton robot needs to be planned in advance,so as to drive the user to walk.In this paper,a static stable gait planning method was proposed based on the COG projection method.Under the constraint of geometric,the stable and smooth gait trajectory was planned,and the joints angles were obtained.The robot system realized the static and stable walk without other auxiliary equipment.Research on the joints angles correction control strategy based on linkage model.In order to correct the error between the actual and planned COG,the joints angles correction control strategy was proposed.It calculated the correction value of each joint according to the error between the actual and planned COG,which caused by the model error,mechanical transmission error and external disturbance,etc.Then the actual COG was corrected,so as to achieve the COG closed loop control and increase system stability margin.Hardware and software design of control system.The control system based on industrial computer and the motion control card was built.The two levels control mode was adopted,the upper computer responsible for the top level control strategy,and the lower computer responsible for motors servo control.A COG measurement module based on multiple pressure sensors was designed,so as to obtain the COG of the robot system in real time.And the control software was written.Experimental research.In order to verify the correctness of the proposed control method,experiments were carried out,including the COG measurement module calibration experiment,the motor servo control experiment,the robot no-load experiment,the walking aid experiment and the anti-disturbance experiment.The experimental results showed that the control method and the hardware and software experimental platform could realize the function of walking aid and verify the effectiveness of the method.