Research On Structure Optimization And Active Control Of Heavy-Duty Hexapod Robot Based On Rigid-Flexible Coupling Model

The heavy-duty hexapod robot has excellent terrain adaptability and load-bearing capacity,which is an important form of legged robot oriented to practical application.The heavy-duty hexapod robot not only includes a wide range of rigid body motion during walking,but also produces elastic deformation motion of flexible legs due to the high weight stiffness ratio.Due to the coupling between the flexible deformation movement of the legs of the hexapod robot and the rigid body movement of the whole machine,the trajectory tracking accuracy of the robot is reduced,and the vibration is inevitably generated.As a result,the swinging legs will touch the ground in advance,the body will tilt forward,and a large impact stress will be generated,which seriously affects the stability and safety of operation.In order to overcome the above flexible vibration problems effectively and improve its static and dynamic performance comprehensively,this paper takes a large heavy-duty hexapod robot as the research object,and conducts in-depth research on its rigid-flexible coupling multi-body system modeling,simulation,dynamic characteristics analysis,structure optimization,and active control strategy.Firstly,the kinematic and rigid-flexible coupling dynamic model of hexapod robots are constructed.The kinematics of the hexapod robot is analyzed,and the corresponding relationship between the foot velocity and the driving joint velocity is established according to Jacobian matrix.Based on the assumption mode method and floating coordinate system,the deformation of the flexible leg is described.The dynamics of flexible multibody system of the leg is established according to the Lagrange equation,and the driving torque expression of the leg joint of the hexapod robot is obtained by solving the foot force distribution.Secondly,the visual simulation model of rigid and flexible multibody systems of heavy-duty hexapod robot is established.By analyzing the dynamic characteristics of the two models,the influence of flexible connecting rod elastic deformation on robot vibration and trajectory tracking accuracy was revealed,and the necessity of flexible leg treatment was revealed.The end deformation and dynamic stress of the flexible parts are analyzed,and the strength and stiffness of the robot in the process of movement are broke down in all aspects.And correct simulation model is verified by dynamic stress-strain experiment.Thirdly,in order to solve the problem of inadequate leg stiffness and flexible deformation,a multi-objective optimization method based on the approximate model is proposed to integrate the multi-operating conditions,static and dynamic performance of the leg structure,and then the passive control strategy is studied,and the optimization scheme is designed,and the optimization platform and integrated system are built.On this basis,experiment design,parameter sensitivity analysis,approximate model establishment and multi-objective optimization are carried out,and the results are analyzed and verified by simulation.Finally,based on the rigid-flexible coupling model,an active control strategy based on feedforward compensation and PD feedback is proposed to solve the flexible deformation and vibration problems of the heavy-duty hexapod robot,which can accelerate the system response speed and improve the trajectory tracking accuracy.The co-simulation system of the control is further established,and the correctness of the control simulation model and the correctness of the proposed active control strategy are verified by simulation results.