Research On Trajectory Planning And Coordinated Control Of Hydraulically Driven Hexapod Robot

Natural disasters such as fires and earthquakes have caused huge damage to the terrain.However,common wheeled rescue vehicles cannot work properly,which greatly increases the difficulty of rescue work.But the foot movement has stronger adaptability to complex environments and plays an irreplaceable role in complex environments.Therefore,research on the hexapod robot as one of its representatives has great significance and effect.Aiming at the problem of hexapod robot's weak antijamming ability on non-ideal ground,this paper focuses on the research of foot trajectory planning based on low impact and continuous speed and foot force impedance control.According to the mechanical structure characteristics of the hydraulically driven hexapod robot,the D-H parameter method is used to establish the single-leg kinematics model of the hexapod robot.The purpose is to obtain the relationship between the foot trajectory coordinates and the rotation angle of each joint,and then get the relationship between it and the displacement of the hydraulic cylinder.Lagrange dynamic equations are used to establish the single-leg dynamics model of the hexapod robot to determine the relationship between the rotation angle of each joint and the torque,laying the foundation for subsequent trajectory optimization and coordinated control.Large hydraulically driven hexapod robots will produce a great impact during the movement,which affects the strength of the mechanical structure and the stability of the hexapod robot.In response to the above problems,polynomial interpolation is used in the normal and tangential directions to plan the foot motion trajectory based on low impact and continuous speed,which ensure that there are no sudden changes in the angular velocity and angular acceleration of each joint during the movement and reduce the impact of the movement.At the same time,the speed change is completed before the support phase and swing phase of the hexapod robot alternate to ensure the continuity of speed and avoid "stuck" phenomenon.Finally,trajectory of the foot-end that can reduce the impact and ensure continuous speed is planned.For the problem that the hydraulically driven hexapod robots has weak antiinterference ability against the dynamic environment,the foot force distribution and impedance control algorithms are applied to control the hexapod robot.Based on the energy-optimized foot force distribution algorithm,the foot force distribution algorithm is improved by changing the position of the center of mass.In terms of impedance control,the parameters of impedance control are analyzed to provide a theoretical basis for the modification of impedance control parameters later.Combining the above two aspects,the coordinated control of the hydraulically driven hexapod robots is realized,so that the hexapod robot can walk stably in a dynamic environment.In order to verify the correctness and effectiveness of the above-mentioned theories,the planned trajectory and control algorithm were simulated and verified by prototype experiments.By establishing a co-simulation platform of ADAMS and MATLAB,the correctness of kinematics and dynamics were verified.Through simulation and analysis of different environments on flat and rugged ground,the effectiveness of foot force distribution and impedance control is verified.Then,the prototype experiment further verified the practicability of the planned trajectory and control algorithm.