Servo Control And Compliance Control Of Hydraulic Quadruped Robot

Due to its non-continuous ground support, flexibility, obstacle capacity, environmental adaptability and other characteristics, legged robot shows broad application prospects in numerous fields. To construct bionic quadruped robot with large load capacity, highly dynamic vesatility and complex environmental adaptability has become a hot topic in recent years.Aim to improve quadruped robot dynamic performance and complex environmental adaptability, and promote its application, this thesis conducted a research in quadruped robot structural optimization, valve-cylinder dynamics modeling, high-performance hydraulic servo control and compliance control.Starting from design goals and condition analysis, "symmetry installation" and "large stroke and small bore" principles are proposed after a detailed analysis on hydraulic cylinder dimensions and installation parameters. Multi-objective optimization of leg length and joint range under non-linear constraints has been fulfilled, which not only increases leg configuration space, but also significantly reduces robot weight and leg weight.Based on reasonable simplification, valve-cylinder dynamics model has been established, and model parameters have been identified experimentally. Frequency response characteristics, stability and steady-state error of position PID control are analyzed in detail. To improve system damping and consequently position servo performance, hydraulic force feedback correction loop is implemented. Model-based velocity compensation algorithm and feedback linearization algorithm are presented to cope with inherent load feedback and nonlinearity of hydraulic actuation. Experiment results show that force response time and tracking error are reduced consequently.Compliance control methods, such as virtual model control, computed torque control, impedance control, are fully analyzed and implemented. To reduce control performance deterioration caused by dynamics nonlinearity and coupling, inverse dynamics compensation is added. Simulation and experiment results demonstrated that inverse dynamics compensation can enhance robot compliance without sacrificing position tacking accuracy. Experiments carried out on robot leg platform demonstrate that model-based compliance control algorithm can improve robot control performance and significantly reduce impact force.This thesis not only completed quadruped robot structural optimization, but also implemented high-performance hydraulic servo and compliance controller. It is helpful for improving quadruped robot dynamic performance in complex environments.