Research On Dynamic Dimensional Synthesis Method And Its Application For A Waist Exoskeleton Robot

The lumbar spine is the main bearing structure of the spine.Under long-term physiological and external loading,it is extremely vulnerable to damage and degenerative changes,which leads to lumbar diseases.Therefore,the research on lumbar exoskeleton robots has received extensive attention.However,the current research on waist exoskeletons is mostly about powered exoskeleton robots,and their main application scenarios are load handling or military.These exoskeleton robots are difficult to be civilian used and marketized by their high cost,complex degree of freedom control,and power source technology limitations.At the same time,the research is mainly focused on their bearing performance,while ignoring the discussion on wearing comfort.In this thesis,aiming at the importance of reducing the lumbar motion load for its disease prevention and treatment,a research prototype of a multidegree-of-freedom bionic lumbar non-powered exoskeleton robot with human biomechanical characteristics is proposed.Then,aiming at the effective achievement of the motion-bearing bionic working mechanism,the dynamic dimensional synthesis based on the multi-rigid-flexible body dynamics is deeply carried.First,by analyzing the physiological structure of the human waist and its nosodochium,the design goal of reducing the waist movement load is established.On this basis,for reducing the load of the waist under the upright condition,which is of great significance to the prevention and treatment of its diseases,the exoskeleton armpit support frame is innovatively proposed,which can transmit the upper body load from the armpit to the exoskeleton,and then to the hip.Based on the physiological structure of the human lumbar spine,a multi-degree-of-freedom bionic lumbar spine is designed by using vertebral elements and universal joints to make it compatible with the movement of the human waist,and a snap is used to lock the exoskeleton when upright load working condition is required.For the individual differences of the wearer,the exoskeleton is also provided with a telescopic mechanism,which can change the length of the exoskeleton to make it adapt to different wearing individuals.Secondly,aiming at the effective achievement of dynamic dimensional synthesis of the waist exoskeleton robot,an equivalent model of the human lumbar spine is constructed based on the data of related in vitro experiments,and then a multi-rigidflexible body dynamic model of a human-machine parallel system is established on the sagittal plane.On this basis,a new dynamic evaluation index named bionic load-bearing comfort level is proposed,and the bionic performance optimization of the exoskeleton robot is deeply carried out by numerical simulation under the positive dynamic model.The simulation results verify that the lumbar exoskeleton robot has superior bionic comprehensive dynamic performance and the effectiveness of the research method.At the same time,it also shows that the performance indexes of exoskeletons are quite different before controlling system trajectory,which means that it is necessary to research system inverse dynamics.Finally,focusing on the complexity of the frequency domain method for the flexible body inverse dynamics,an equivalent strategy,which approximates the solution of inverse dynamics by linear iteration with optimization during the positive dynamics,is proposed in this paper to achieve the consistency of the thoracic spine trajectory before and after the exoskeleton is worn.Then,the dynamic dimensional synthesis of the exoskeleton with a human-machine parallel system is deeply carried out,and the optimal scale parameters set of the exoskeleton robot is obtained.The simulation results show that the trajectory error of the thoracic spine,which comes from the equivalent inverse dynamics,is extremely small in the sagittal plane,and the equivalent force of the human waist is significantly improved compared with that before wearing the exoskeleton.The wearing comfort indexes of the exoskeleton after optimization are significantly improved,which proves the reasonable effectiveness of the research methods.At the same time,the optimal scale parameters set are of great significance to the development of the physical prototype and the related experiments.