Development And Research On Safety Control Strategy Of Lower Extremity Exoskeleton For Disabled People

The exoskeleton system,as a wearable robotic device,is more adaptable to complex terrain than wheeled equipment and is therefore widely used in the area of military,rescue,industrial and medical rehabilitation.The light exoskeleton system designed by this subject is mainly for people with dysfunction of lower extremity,such as the elderly,to help them strengthen the lower limb strength and motion capacity,and reduce the physical exertion during walking,sitting down,standing up,etc.For the target user and application situation,this paper discusses the design of exoskeleton system,including the design of mechanical structure and sensing and controlling system,the research on control algorithm and strategy and related experimental testing and verification.Considering that the target user is people with dysfunction of lower extremity such as the elderly,the design of the exoskeleton of this subject adopts an anthropomorphic method,on the basis of ensuring that the degree of freedom and joint space,output torque and joint angular velocity meet the requirements,through the use of carbon fiber materials and reasonable structural design to reduce the mass of the exoskeleton and improve the convenience and comfort of wearing.The stable and reliable sensing and controlling system with high detection accuracy is the prerequisite for the exoskeleton system to achieve the target function and have good practicability.A sensing system consisting of a inclinometer,joint angle sensors,torque sensors,and pressure sensors is designed and integrated for the exoskeleton proposed in this subject to provide the necessary motion information for the control of the exoskeleton.Using PC104 as the controller of the exoskeleton system,a real-time simulation system with master-slave structure is established,which has high programming efficiency and high calculation speed.The sensing and controlling system adopts the communication mode of CAN bus,which has high communication efficiency and reliability.Considering that the target user is people with dysfunction of lower extremity,the control strategy of the exoskeleton system needs to meet the requirements of both power enhancement and safety.In this subject,the floating coordinate base is used as the origin of the joint space coordinate system,and a unified dynamics model is established,so that there is no need to distinguish between the support phase and the swing phase when calculating the control torque.Combined with the sensitivity amplification method,the feedforward control of the human-machine coupling system is established to provide assistance for the wearer's movement.Based on ZMP and capture point theory,a safety control strategy is integrated in the exoskeleton control system to evaluate the equilibrium state of the system in real time during the movement,and to provide correction torque for the exoskeleton system joints when the dynamic imbalance is about to happen,helping the wearer to maintain balance and improve security.Finally,the assembly and integration of the exoskeleton system was completed.For the application situation of the exoskeleton,the performance and control strategy proposed in this subject were verified by related experiments.The flat ground walking,stair climbing,and sit-up experiments were carried out to verify the assist performance of the exoskeleton and the effectiveness and stability of the feedforward control method.Balance experiments were carried out to analyze the balance state during standing and walking,to verify the effectiveness of the proposed equilibrium state assessment and balance recovery strategy.