Leg Structure Optimization And Analysis Of Unmanned Metamorphic Vehicle

The purpose of this paper is to design an unmanned metamorphic vehicle which can be used in complex terrain.It can be used in mine detection,anti-terrorism and anti-riot,earthquake relief and other special environments to improve work efficiency and ensure personnel safety.The traditional wheeled vehicle control method is not very complicated,and the speed of movement is high.Unmanned metamorphic vehicle is flexible and energy-consuming,but traditional wheeled vehicles can not overcome such obstacles as trenches,terrain and so on.They can not drive well when they encounter higher ground protrusions,muddy ground and other conditions.Compared with wheeled vehicles,tracked vehicles have stronger adaptability to terrain,can adapt to steep terrain and complex environment,and have higher obstacle-surmounting ability and environmental adaptability in these environments.However,because of the great friction resistance and high energy consumption,it is especially unsuitable for long-distance movement.At the same time,because the tracked vehicle is composed of multiple components,it is not smooth enough to travel at high speed.In theory,the legged robot is the most flexible motion mechanism.The legged ground moving system is very suitable for crossing obstacles such as trenches and steps.But the biggest problem of the legged mechanism is that the center of gravity is too high and it is difficult to control.This paper takes the leg structure of metamorphic vehicle as the research object.Based on the preliminary design of the leg structure of the metamorphic vehicle,in order to meet the mechanical properties and lightweight requirements of the leg structure,the topology optimization of the hip,thigh,calf and ankle in the leg structure of the metamorphic vehicle is carried out.The multi-objective optimization of the hip,thigh,calf,ankle and foot is carried out,and the strength analysis of the optimized results is carried out to verify whether the optimized results meet the requirements.Firstly,the multi-body dynamics model of the metamorphic vehicle is established by Adams.Through simulation,the force curves of the metamorphic vehicle in the deformation process are obtained at the joints of the bottom plate and the hip,the hip and the cross tube,the cross tube and the thigh,the knee joint,the crus and ankles,the ankle and foot joints and the contact between the foot and the ground.Then,based on the basic theory of the variable density method of topology optimization,the Optistruct module in HyperMesh software is used to optimize the topology,and the feature identification of the results of topology optimization is carried out,and the mechanical structure of the leg is redesigned according to the identification results.In view of the chessboard problem encountered in the process of topology optimization,this paper sets reasonable parameters to solve the chessboard problem well.Finally,the ideal results of topology optimization are obtained.For the redesigned leg structure,multi-objective optimization is carried out with stress and quality as optimization objectives and thickness as optimization variables.The Pareto frontier can be obtained by design of experiment,simulation,establish approximation model and optimization.Then,according to the weight selection method proposed inthis paper,the ideal target point is selected from the Pareto front.According to the result of the selected point,the component is redesigned again,and the whole leg mechanism is designed and completed.Finally,the strength analysis of the redesigned structure is compared and verified.To select the optimal solution from Pareto frontier,this paper proposes a new and stylized method to select the optimal solution,which greatly improves the subjectivity of the previous selection,makes the selection of the optimal solution more standardized,more accurate and more ideal.