Research On Key Technologies Of Joint-Assisted Exoskeleton Robot In Active Spacesuit

In the future space exploration,many tasks(such as assembly and maintenance of space equipment,on-orbit capture and release of spacecraft,space cargo handling,collection of lunar rock specimens,scientific experiments in low gravity environments,etc.)require astronauts to carry a large number of equipment and specimens in a variety of complex terrains or gravity environments,and carry out long-term,wide-range,multi-task of EVAs(extravehicular activities).Different from traditional intravehicular activities,the current in-orbit operations and the future planetary exploration require astronauts to wear thick and heavy extravehicular spacesuits,as well as good mobility and flexibility of the spacesuits’ joint systems.However,due to the pressure protection,the multi-layer fabric structure of the spacesuit would produce an obvious resistant torque,which increases the extra physical energy expenditure and seriously affects the completion quality of future extravehicular missions.Therefore,the research on jointassisted exoskeleton robot in active spacesuit is firstly proposed.That is,the advanced exoskeleton robot technology is integrated on the basis of the existing extravehicular spacesuit,so that astronaut-spacesuit-exoskeleton robot becomes a highly coupled complex power-assisted system,as well as assist astronauts to reduce the influence of joint resistant torque and equipment load.The main research works of this dissertation are summarized as follows:1.Considering the requirement of matching the structure size with the existing extravehicular spacesuit,the research on the structural optimization of joint-assisted exoskeleton robot in active spacesuit is carried out.Firstly,the ergonomic requirements of active spacesuit and astronauts’ EVAs are probed into,the structural design scheme of the first-generation joint-assisted exoskeleton robot is completed by measuring the parameters of the wearer-spacesuit system.Then,according to the feedback,a structural improvement scheme is proposed,the static and modal analysis of the secondgeneration joint-assisted exoskeleton robot prototype under load condition is conducted.Finally,dimensional optimization design is used to further reduce the overall mass.Compared with the unoptimized second-generation and the first-generation prototype,the optimized overall mass decreased by 19.34% and 40.03% respectively,which verifies the feasibility of structural optimization scheme.2.In view of the difficulty in modeling the joint resistant torque of extravehicular spacesuit due to hysteresis characteristics,a simulation study on the hysteresis characteristics of the joint resistant torque in extravehicular spacesuit based on the modified Jiles-Atherton model is conducted.Firstly,based on the EMU(Extravehicular Mobility Unit)extravehicular spacesuit,the hysteresis relationship between the joint resistant torque and the motion angle of the spacesuit shoulder,elbow,hip and knee is obtained by the data-fitting of joint resistant torque.Secondly,the principle of the modified J-A(Jiles-Atherton)hysteretic model and its consistency with the hysteresis characteristics of joint resistant torque are analyzed,and a SA-PSO(Simulated annealing-particle swarm optimization)algorithm is proposed to identify the parameters of the modified J-A model,which verifies the effectiveness and performance advantages of the proposed algorithm compared with the existing optimization algorithm.In addition,the identified J-A model can predict the resistant torque of unknown joint motion.Finally,according to the characteristics of modeling error,a simple and effective error compensation function is designed to further reduce the prediction error of the unknown joint resistant torque.3.Considering the interaction torque and joint resistant torque existing in the HSI(Human-Spacesuit Interaction)system,a nonlinear dynamic model of joint-assisted exoskeleton robot for the lunar sample collection mission is firstly constructed.Firstly,by analyzing astronauts’ typical EVAs,a simulated lunar sample collection mission is designed,including walking on the moon,squatting and standing up to transfer the samples.Secondly,a suspended low-gravity simulation experiment equipment and a human motion information acquisition system are built,and joint motion studies are carried out to simulate the lunar sample collection mission.Finally,based on the established dynamic model,the absolute values joint required torque and work under three states of undressed,dressed and unpressured,and pressured is calculated.Among them,when walking and squatting in the lunar sample collection mission,the hip joint increased by 289.05% and 663.9% respectively.The theoretical calculation results verify the obstruction effect of the pressurized spacesuit on astronauts’ motion.4.Considering the modeling error of nonlinear dynamic model and uncertainties such as interference,equipment loads change and influence of different wearers in the HSI system,an adaptive admittance control method based on the wearer-active spacesuit interaction is proposed.Firstly,a position inner loop based on adaptive robust fuzzy control is designed to enhance the tracking effect for a given reference trajectory.Secondly,an adaptive RBF(Radial Basis Function)neural network control is designed for different wearers or the same wearer in different states,which can be used to approximate the variable HSI model as a whole.Then,a force impedance correction outer loop with time-varying stiffness parameters is designed to minimize the interaction force and tracking error in the HSI system,the feasibility and robustness of the proposed control algorithm are verified by simulating lunar sample collection mission.Finally,the theoretical simulation results prove the power-assisted effect of joint-assisted exoskeleton robot in active spacesuit.5.In order to verify the proposed control algorithms,the experimental platform of active spacesuit is built to carry out the SAT(Servo Augmentation Technology)test of joint-assisted exoskeleton robot.Firstly,active spacesuit is introduced from the aspects of the designed exoskeleton robot prototype,hardware platform and software platform.Then,in the normal ground test environment,the motion following test for multiple actions is completed,such as standing to transfer samples,normal walking and squatting,which verifies the excellent stability and following performance of the proposed control algorithm.Finally,in the simulated low-gravity test environment,the motion assistance test of standing to transfer samples is conducted.By collecting the heart rate values of the three experimenters in only wearing the simulated spacesuit and wearing active spacesuit,and according to the empirical formula of the heart rate value and oxygen consumption,the oxygen consumption of the three experimenters decreased by 9.72% at most,which theoretically prove the power-assisted effect of joint-assisted exoskeleton robot in active spacesuit.