A Unified Gait Approach To Control Of Powered Lower-limb Prosthesis

The auxiliary function of the lower-limb prosthesis is very important to restore the motor function of the lower limb amputee.Compared with passive prosthesis,powered prosthesis can actively provide energy to reduce the consumption of amputees and improve the stability of amputees’ movements.Common control strategies will divide the amputee’s gait cycles into different phases according to different states to control.In clinical promotion,the configuration of such methods will be significantly improved with the increase of tasks,and there is a potential safety hazard of incorrect switching during switching between different phases.Therefore,this paper analyzes the movement trajectory of normal human legs and studies the unified gait control method for the motion control of the power prosthesis.The main research work is as follows:1.Amputees who have amputated thighs due to disease accidents need to wear power prosthesis with knee and ankle joints in order to restore normal athletic ability.The gait cycles of an amputee wearing a lower-limb prosthesis is similar to the bipedal movement of a normal human body,and the movement of the prosthesis and the movement of the amputee are coupled with each other.In order to design a unified gait control strategy,it is necessary to establish and analyze the kinetic and kinematics model of the prosthesis in use.The common modeling methods simplify the prosthesis into a two-dimensional model ignoring the impact of its lateral movement on the system.Therefore,this paper studies the complex kinetic and kinematics model by establishing and analyzing the prosthesis leg model in three-dimensional space,and analyzes the reasons for its segmented control and coupled movement.So as to lay a reasonable theoretical basis for the unified gait control of the bionic legs.2.When the lower-limb prosthesis assists amputee movement,it needs to cooperate with the patient’s movement to realize the coupled movement,and in order to ensure the continuity of the prosthesis gait cycles,a unified gait parameter should be used to describe the gait cycles of the human lower limb.Therefore,this paper collects and analyzes the trajectories of normal human lower limbs walking on flat ground,ascent stairs and descent stairs through Vicon equipment,and analyzes and studies them,and proposes a segmentation-based gait parameterization method.Using the trajectory of the hip joint in the sagittal plane and the coronal plane to design the gait parameter polynomial of the human movement,in order to describe the gait cycles of the amputee and serve as the driving amount of the prosthesis movement,to meet the relationship between the prosthesis and the amputee Coupling motion relationship.3.Aiming at the problem of segmented control of the motion process caused by the mixed kinetic characteristics of the prosthesis leg in the motion process,this paper uses a hybrid Zero Dynamics control strategy based on the concept of virtual constraints to design a motion controller for the prosthesis leg.Based on the discrete Fourier transform method,the normal human body trajectory is designed as the reference trajectory of the bionic leg motion regarding gait parameters to satisfy the relationship between the bionic nature of the prosthesis leg motion and the coupled motion.4.In the end,this paper verified the effectiveness of the unified gait control method for power prosthesis in the tasks of walking on flat ground,ascenting stairs and descending stairs through the simulation model of amputee built in WEBOTS simulation software.This method affects amputees during exercise.