| With the rapid development of bionics,robotics,control theory and Internet,the development strategy of Industry 4.0 is put forward,and the development of robots industry has been more and more concerned by the academia.As the carrier of artificial intelligence,robots can be widely used in military,industrial,medical and other fields.Especially in some high-risk,high-load application environment,robots are indispensable.And the study of control methods for robots has become a top priority.This article mainly studies the impedance control of hydraulic quadrupeds applied to industrial high-load environment.By researching conduct theoretical,mathematical derivation,designing control strategy,simulation optimization,comparing diffient control strategies and analysing simulation results of three-degree-of-freedom impedance control for the problems of concern robots control methods,to improve the the hydraulic quadrupeds' adaptability on complex roads,force characteristics,stability,displacement characteristics and compliance performance.According to the knowledge of robotics and physical kinematics,deduce the three-degree-of-freedom kinematics and dynamics of the robot,and the joint moment calculation formulas of the single-leg swing phase and the support phase are obtained,which lays a foundation for the research of impedance control.Study the single-leg impedance control.Analyze the posture angle,speed,and acceleration of one leg in a diagonal trot gait during a cycle,and analyze the relationship between the angles and forces from the three directions of the foot during the support phase through mathematical deductions to optimize the position-based control method and verify the important significance of the lateral freedom for robot stability through simulation.Then conduct a variety of tests based on force control methods on the single leg.And then design a force control method with inverse dynamic feedforward and PD controller compensation and build simulation platform,to compare the force and position characteristics of the hydraulic cylinder of simple force control with the ones of new control method during the swing phase.At the same time,perform support phase simulation,and optimize the force control strategy,to adapt it to the large load during the support phase.At last,build the impact force test platform to test the compliance performance during the swing phase with the impact force under the new force-based control method.The impedance control research of the quadruped robot is carried out.First,build a full-torque control simulation framework for the robot to compare the control characteristics of two control methods which is based on position and force.Verify the effectiveness and superiority of the force-based control method.In order to further compare the control performance based on position control and force control,study the control method of the quadrupeds' diagonal trot with variable step sizes.And then design a suitable walking style with variable step sizes,and build the control simulation platform to compare the robot's walking speed characteristics of position control with the ones of force control through simulation and verify that the impedance control based on force control has better speed stability.The target of this topic mainly include the following points.First,the impedance control research is considered in three degrees of freedom,and the important significance of the lateral force for robot's stability is verified through joint simulation;Secondly,a new force-based impedance control method is proposed,that is inverse dynamic feedforward and PD controller compensation,and optimize it to adapt it to the large load during the support phase,and verify its feasibility through simulation;Finally,the control methods of the diagonal trot with variable step sizes is studied,and the simulation verifies that compared with the position impedance control,the force impedance control method has better speed stability. |
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