Research On Hydraulic Actuated Biped Robot And Its Dynamic Balance Motion Control

A hydraulic actuated biped robot's non-continuous contact motion characteristic prompts it to adapt to the complex roads in the field,and the fact that it has fewer legs makes it easy to cope with jungle conditions,as well the high power density ratio of its hydraulic system provides the necessary driving force in the harsh environment.These mean that hydraulic actuated biped robots have great advantages when moving in the field environments.However,due to the limited foot supporting area of the biped robot,it can easily fall down when suffering disturbance force,which greatly limits the application of biped robot in actual life.Standing and walking are the two most common motion states for biped robots,accordingly,the research on dynamic balance walking and standing of biped robots has important practical significance.A footed inverted pendulum model with walking and standing ability was established by simplifying human motion process.Through the dynamic analysis of the footed linear inverted pendulum model,obtained the relationships between body motion states and leg actions' including the stance hip torque,the step switch length,the stance ankle torque and the body height.These then provided a model and a theoretical basis for the dynamic balance walking and standing control for biped robots.Based on the Newton's laws of motion that the disturbed force will be transformed into the changes of body motion states,and according to the dynamic equations for the footed linear inverted pendulum model proposed in this paper,the corresponding control relationship between leg action and body motion were analyzed.Based on this,a framework for dynamic balance motion control for biped robots was established,which included controlling body postures by hip stance,controlling body height by knee stance,and controlling body level movement by the biped switching step length and ankle torque.The algorithm then was verified by simulation.Then,a method of extending the algorithm to three-dimensional space was illustrated,which provided a control algorithm for biped robot dynamic balance when the robot is in motion.A hydraulic biped robot with a force-position servo was developed by taking the human body as a reference.The mapping relationship was established between the footed linear inverted pendulum model and a hydraulic actuated biped robot.To decrease the hydraulic servo error imposing by joints coupling and touchdown impact of biped robots,a hydraulic cylinder assembly was developed with a PQ servo valve and force-position feedback.The mathematical relationship between the PQ servo valve input current and hydraulic cylinder output force and position was established.According to this relationship,a hydraulic servo system with feed-forward control was established,and improves the servo accuracy of the hydraulic biped robot,which provided a carrier for the biped dynamic balance walking and standing control algorithm.A hydraulic biped robot test platform,including electronic control boards and associated control software,was developed;a dynamic balance standing test was carried out,which verified the standing capability.A round-trip movement test of a biped robot was carried out to verify the walking ability of the control algorithm.Walking tests,with interference from dumbbells,hand-pushing,kicking and other forms of balance disruptions were carried out,which verified the dynamic balance walking capability.Through the above series of tests,it was verified that the control algorithm proposed in this paper could achieve dynamic balance walking and standing for biped robots.