Natural Frequency Analysis Of Hydraulic Quadruped Robot And Impedance Control

Due to its ability to adapt to various complex ground conditions,flexible maneuverability,and high load capacity,hydraulic quadruped robots have received extensive attention as special military robots in recent years.However,how to ensure that quadruped robots can move stably and highly efficient is not yet determined.This article will start with the analysis of the hydraulic natural frequency and the impedance control algorithm to achieve a stable walking on the flat ground.Firstly,the kinematics and dynamics of the single leg of the robot in the swing state and the supporting state are respectively analyzed.The moment equations on each joint of the robot are obtained through the Lagrange equation,and the hydraulic natural frequency of each level of the department is calculated using the equivalent mass matrix and the equivalent stiffness matrix.Analyzes the influence of various structural parameters,and uses the model linearization method to obtain a simplified state equation under a certain posture,and further analyzes the influence of hydraulic natural frequency on the overall control characteristics of the robot.Then,do the study of single leg position control.Use ADAMS-Simulink to build a simulation platform and use it to evaluate the effect of the position controller.In the position control,two control algorithms,segmented PID control and feedforward control,are introduced to reduce the lag of the position response of the system.The validity of the two control algorithms is verified by simulation analysis.Next,a one-leg impedance control model based on position control is constructed.The external load at the end of foot is calculated by using the difference between the theoretical joint torque and the actual joint torque,using this to realize load tracking.Through this active compliance control,the ability of the robot's legs to adapt to changes in the environment is enhanced.Extend the single-leg impedance control model to the four legs of the robot.The impedance control reduces the interference of the body around the support point and other factors on the position control and realizes a long-distance stable linear walking of the robot.Finally,a one-leg impedance control experiment bench for the robot was built.Use Simulink Real-Time to build the real-time control system of the experiment bench.The position and output of the hydraulic cylinder were collected as feedback signals.The position tracking experiment and the impedance control experiment of the single leg of the robot were performed to verify the accuracy of the simulation.This topic analyzes the natural frequency of the hydraulic power mechanism of hydraulic quadruped robot and quantitatively analyzes the influence of the structural parameters of all parts of the quadruped robot on the overall dynamic performance of the robot under different working conditions,providing theoretical guidance for improving the dynamic response capability of the robot.In addition,the interference with environmental factors can be corrected by the cooperation with the impedance control algorithm,and the purpose of the long-distance walking of the quadrupedal robot can be achieved.