Study On Dynamic Characteristics Of Multi-joint Low Damping Lower Limb Exoskeleton

Under the environment of weightlessness in space,the astronaut's muscle force is always reduced,and the workload is decreased.The main reason is the long-term exposure to weightlessness environment,resulting in a variety of adverse physiological effects,such as muscle atrophy and bone loss.These changes would extremely affect the health and work ability of astronauts.So,feasible measures should be taken to fight against the adverse effects of weightlessness in astronaut's body.Wearable robot,combining with some parts and joints shape of human,is a mechatronic system possessing advanced technology which compensates,improves and replaces human's partial function.Basically,the exoskeleton is designed to realize the special properties which can provide people with physical support,extra power and enhanced human's function.If change this power into resistance,loading low damping at each joint of lower limb for a longtime,under the premise of the range of human body's movement unlimited,overcoming the damping provided by the device,and it is possible to induce the decrement of muscle force caused by long-term weight loss,and to reduce the adverse effects of reduced exercise capacity.But this wearable multi-joint low resistance lower extremity exoskeleton structure should have a good ergonomic design,mechanical structure and distribution of degree of freedom,motion space should have a good agreement with human joint structure and movement characteristics,which need to meet the requirements of different types of human body.However,there are some troubles to be overcomed in the exoskeleton design phrase.Such as the imperfection of design theory,the unreasonable of structural design,and the joints of exoskeleton without a good control ability.Based on the requirements mentioned above,the kinematical equation of man-machine exoskeletons has been established in with differential geometry and homogeneous coordinate's equation in this paper.The trajectory of ankle has been deduced by using MATLAB.In the aspect of the human lower extremity exoskeleton and lower limb movement in the presence of interference problems,establish the equations of shortest distance of no coplanar lines,and solved the equations with the condition of the shortest distance between lower extremity exoskeleton thigh and human thigh is greater than the human thigh muscle,obtained the relation of the distance of rotary axial between human lower limbs and lower extremity exoskeletons.Adopting the Newton-Euler dynamics mechanism,the dynamics equations for lower limb have been modeled to calculate the joint torque.According to the body parameters,the thigh length,the shank length and their masses and its center have been obtained.The Vicon 3D data acquisition equipment has been employed to acquire the movement parameters at the different gaits.The revolution curves of the hip-joint angle,the knee-joint angle have been descripted in the paper.To run the established equations with the mined data in the trails,the values of torque in the each joint have been calculated with MATLAB software.In this way,the torque evolutions of the hip and knee joint at two different gaits have been disclosed.Then the 3D human model has been established to import into ADAMS,setting the model parameters,adding constraints conditions and importing joint driven parameters,then the gait simulation jobs of human body at different speeds have been finished.Torque characteristics curves of hip,knee and ankle joint gait under the condition of different speeds have been obtained to provide the supports for the selection design of exoskeleton dampers.Finally,with the ergonomic,the 3D model of the exoskeleton structure has been finished which met the requirements of wear comfort and length adjustable.The model of dampers has been selected based on the simulation results of ADAMS.By adopting above-mentioned process,the structure design of the exoskeleton and the model selection of the dampers have been completed,providing an available theoretical method for further study in the subsequent design work.