| The hydraulic drive quadruped bionic robot objected to the four-legged mammalcan be used for exploration, transportation, rescue and military aiding in the complexfield environment, having a broader application prospect and becoming a hotspot ofthe robot research. In the kinemics control of the quadruped robot, the force close-loopof each joint is a typical control strategy, and to ensure a higher power density, eachjoint is driven by the highly integrated hydraulic drive unit. Therefore, the forcecontrol performance has a direct influence on the force control result of eachquadruped robot joint. Moreover, how to ensure the high force control performance ofthe hydraulic drive unit under the complex and variable loading condition is one ofproblems that should be solved urgently.In this paper, the focus work has three aspects including the force control systemcharacteristics, the loading character simulation and the control compensation method,the research work as following:(1) The force control system model would be built and the hydraulic drive unitcharacteristics are analyzed. To get a more accurate force control model for the forcecontrol performance and the control method study of the hydraulic drive unit, themechanism modeling method is applied. The force control mathematic model of thehydraulic drive unit involved with servo pressure-flow characteristics is derived andthe system simulation model is built on the MATLAB/Simulink platform. The testplatform mechanism and composition of the hydraulic unit are introduced, and throughcomparing the testing and simulating curves, the force control system model isverified, the system dynamic characteristics being analyzed.(2) The hydraulic drive unit simulation method with variable load stiffness anddamping characteristics is researched. To simulate the loading condition accurately forthe targeted selection and verification of the hydraulic drive force compensationcontrol method, basing on the impedance control theory of the traditional electricmotor drive robot, targeting on the loading principle of the hydraulic drive unit testing platform, the force control loading characteristics simulation method whose stiffnessand damping parameter that is dynamically adjustable is designed. And the experimentand the simulation of the load characteristics simulation with variable stiffness anddamping under different force response characteristics are analyzed, then the loadingcharacteristics simulation result is derived.The force compensation control method of the hydraulic drive unit with variableload stiffness and damping characteristics is researched. Using the critical ratiomethod is to optimize the PI controller parameter under the certain load stiffness anddamping characteristics, to get the better force control performance of the hydraulicdrive unit under the certain working condition. To ensure the optimized controller withvariable load stiffness and damping have certain robustness, the compensation controltheory of the force control system with variable load stiffness and damping is designed,and the compensation control theory model is derived. Then, the simulation andexperiment research are conducted, and the result of the force compensation controlsystem with variable load stiffness and damping characteristics is got. |
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