Theoretical Analysis And Experimental Research Of The Power-support Human Lower Extremity Exoskeleton

Power-support human lower extremity exoskeleton(HLEE,for short)is a kind of wearable intelligent robot that possesses the capability of carrying a payload and can supplement human intelligence with the strength.It can be used for marching soldiers to bear heavy payload,so it can reduce the burden of the wearer in real time.The research of HLEE was started early in some countries of Europe and America,the technologies are becoming more and more mature and the prototypes are gradually close to the practical requirements in those countries.However,at present,there is still large gap between the research results of all the power-support HLEE of our country and actual applications,and the understanding of the power-support HLEE is still not enough.In this article,the mechanical system of power-support HLEE was analyzed and designed;the kinematics and dynamics of HLEE are simulated and analyzed;a man-machine coupling simulation method was proposed to analyze the power-support effect of HLEE structure;an interaction force amplification control scheme for HLEE was designed based on the motor current loop;the mathematical modeling and simulation analysis of the man-machine-electromechanical integration system of HLEE was carried out;the PID controller parameters of the interaction force amplification control scheme was optimized by three intelligent algorithms;the HLEE prototype system was developed and some experiments were carried out to analyze the effects of the exoskeleton prototype.More details are as below:1.The design of the motor-direct-driven HLEE structure and the hydraulic-driven HLEE structure was completed.A novel translational-knee HLEE structure was proposed and designed,which can make the exoskeleton much simpler and more compact.And the translational-knee of the exoskeleton was directly implemented by hydraulic cylinder or electric push rod.2.The gait data of the HLEE simulation model were obtained by human motion capture,and then the study of the multi-body dynamics modeling and simulation was carried out by Adams software.The parameters of the HLEE with different loads were simulated and compared,and the results showed that the maximal torque and the maximum power(instantaneous parameter)could not effectively reflect the power-support effect of the HLEE.The motor drive system and hydraulic drive system parameters of the exoskeleton were obtained by simulation.The method of adding elastic elements and damping elements to exoskeleton joints was analyzed,it was found that the addition of elastic elements can reduce the absolute value of the maximal torque required by the joint of the exoskeleton,the damping element can improve the joint motion characteristics but produce additional energy consumption.And the analysis of the simulation results show that the control strategy based on the ZMP stability criterion is not applicable to the exoskeleton.3.The man-machine coordinating Adams-Simulink modeling and simulation study was carried out to obtain the joint driving torque and driving power curve of human body during the movement.The power-support effect of the HLEE was analyzed by contrasting simulation of different models.It was found that the reducing of the range of human joint torque is not very obvious by wearing the HLEE,but the HLEE can reduce the consumption of the extra torque-of-momentum and energy for carrying heavy payload.So it can be concluded that the power-support effect of the HLEE is reflected in the moment of momentum and energy(process parameters)rather than the torque range(instantaneous parameter).In addition,the similar power-support effect simulating analysis of the translational-knee HLEE was also carried out,and it was proved that the designed translational-knee HLEE structure can also achieve the goal of reducing the weight-bearing burden of human body during the process of walking.4.An interaction force amplification control scheme based on motor current loop was proposed,which regarded human body as the working environment of HLEE.The mathematical model of the man-machine-electromechanical interaction system was established,and the corresponding Simulink model was built and carried out on the basis of the mathematical model.The simulation results show that this interaction force amplification control scheme can greatly reduce the man-machine interaction force during the process of walking and achieve good man-machine coordination.5.The genetic algorithm,BP neural network algorithm and fuzzy adaptive algorithm were applied to optimize the traditional PID controller parameters used in the interaction force amplification control scheme,and the control effect of different optimization algorithms was simulated and analyzed.Through the comparison of the simulation results,it can be obtained that the three intelligent algorithm controllers can all achieve certain optimization results,in which the designed fuzzy adaptive control algorithm is the best.6.The experimental prototype system of the power-support HLEE was designed and developed.The power-support effect perfoormance and the man-machine coordination performance of the HLEE prototype were experimented and analyzed.The results showed that,under different walking speed and terrain,the human body only needs to provide about 25%of the extra energy and moment of momentum of the HLEE knee joint for moving the heavy payload and the knee angle deviation between human body and HLEE is within 10° in most time.So,it is proved that the designed prototype has good assisting effect and good man-machine coordination under different conditions of motion.