Research On Force Distribution Method Of Large Heavy-duty Hexapod Robot Based On Dynamics

The large-scale heavy-duty hexapod robot has high carrying capacity,strong stability and good passability,it can adapt to the complex mountainous environment and replace vehicles to carry out material transportation because of discontinuous environmental contact characteristics,therefore,it has important research value and significance.Largescale heavy-duty hexapod robots may have large force impact during walking due to their own reasons such as large size and heavy weight,or protruding and recessed terrain in the environment,resulting in damage to the mechanical components of the legs,or causing the transient current to be too large and damage the driver.At the same time,the imbalance of ground reaction force may cause the posture change of the robot when walking,which may cause the robot to overturn.In view of the above problems,this paper studies the key technology of large-scale heavy-duty hexapod robot.Based on the actual characteristics of the research object,a force-position hybrid control framework is designed for large-scale heavy-duty hexapod robot,and the continuous and stable motion control system of the research object is realized.First,in view of the structural characteristics of the quasi-pantograph leg,the kinematics and dynamics modeling of the leg are carried out,and the problem of the inverse kinematics is solved,and a single leg dynamic model was established,which laid the foundation for subsequent control system design.At the same time,a swing phase trajectory is designed which can effectively reduce the impact of the force and meet the optimal energy consumption constraints.The validation control system is built,the correctness of the modeling method is verified by simulation,and the tracking of the planning trajectory is achieved.Secondly,the method of gait generation and switching for hexapod robots is analyzed.A gait representation method which can effectively describe the motion state of the robot with time is given,and the problem of the top layer time slice planning in the process of robot walking is solved.At the same time,the force situation of the robot is analyzed when the leg is in different mode of motion.The force distribution scheme based on the lever principle is given in different situations,which realizes the stable motion of the robot and the tracking of the speed and acceleration.In order to solve the challenge posed by environmental uncertainty to the stability of robot walking and control system,the robot is abstracted and the impedance control model is hypothesized.The parameters tuning and corresponding control effects of impedance control are discussed through numerical simulation,and the top-level control framework is given.Finally,in order to verify the correctness and effectiveness of the theoretical analysis,the internal control framework of the single leg force control system and the force distribution control system of the whole machine is built on the basis of the calculation moment method,and the prototype experiment is carried out.On this basis,through the single leg simulation experiment,the correctness of the dynamic calculation and the effectiveness of the control system are verified.The good tracking effect of the single leg to different motion tracks is realized,and the simulation and analysis are carried out for the different working conditions,such as the standing and acceleration,the upper and lower slope of the flat ground.The effectiveness of the force distribution method and the practicability of the control system are verified comprehensively.Finally,the actual experimental platform is built,and the stable walking and switching of the robot are realized through physical experiments.The correctness of the force distribution theory of large-scale heavy-duty hexapod robot proposed in this paper is further testified.