Control Of Quadruped Robot In Trotting Gait Based On SLIP Model

After thousands of years of natural selection, four-legged mammalian can runat different speed on different terrains driven by the elastic muscle and tendons withattitude stability. Quadruped robots which imitate the mammalian also shows greatpotential for applications in a complex environment and become a hot topic inrobotics research. Mountain transportation and other applications need the robot tocarry more loads and cross the complex terrain faster, while trotting gait is a kind offast motion pattern which is widely used by different size mammals in differentterrain conditions. But from a point of view of topology, four-legged robot is amulti-branched mechanism, with time-varying topology geometry. The impactswhich happen in feet landing when robot travels also increase the difficluty in robotdesign and control. As a representative of the redundant transmission, the couplingof multiple degrees of freedom in branched locomotion kinematic bring morechallenge in the robot multi-joint coordinated motion and real-time dynamic balancecontro.In this paper, using four-legged mammals as a template, quadruped bionic robottrotting gait control methods was propsed based on analysis and summary of themorphological and biological dynamics research, a quadruped bionic robot systemwas also built based on hydraulically actuated. Firstly, based on the research of thespring-loaded pendulum passive dynamics, the control algorithm to regulate thevelocity and attitude of troso in3D straight leg quadruped robot model in a trot gaitwas proposed; Subsequently, based on the joint functional decomposition ideas andintroduction biological characteristics to joint movement in robot legs, accordancebetween the joints in leg was achieved; Finally, under the experimental study ofsimulation and prototype, effectiveness of the control algorithm and the correctnessof robotic systemsdesign were verified.Based on the analysis of mammalian biomorphic, this paper establish a modelof quadruped bionic robo, and based on biological dynamics analysis, a series ofstraight legs whicih simplify the original model was established. The motion ofsimplified model in sagittal plane was divided to pitch, running forward andjumpping, the control method of each degree of freedom was developed based onthe spring-loaded pendulum passive dynamics. On this basis, the control strategys ofquadruped robot traverse, roll and yaw DOF were developed by expanding themethod above. the multi-freedom quadruped robot cooperative control strategy wasproposed by summing up the various degrees of freedom control method andverified by simulation and prototype experiment. To solve the problem of redundant drive in bionic leg mechanism, biologicalmotion features and control method of straight leg model were analysed, multi-jointin bionic leg cooperative control algorithms were proposed based on the functionaldecomposition strategy. In this method, each joint of the bionic leg assign differentfunctions, and control the degree of freedom on torso respectively when robot runs.On this basis, more biological characteristics were introduced to improve thequadruped robot performance, such as forward speed and ground adaptability.Cause the heavey load on robot may bring large impact when robot moving fastans adversely affected the robot, a control strategy of trot gait without fight phasewas proposed based on joint or foot trajectory method. Considering the traditionaltrajectory planning approach had many defects such as lacking the body control,ignoring foot ground interaction, under the analysis of flexible joints, straight legmodel control methods and joint function decomposition strategy, this paperproposed the control strategy on lateral hip joint which regulate the roll, yaw andtraverse motion cooperatively, the knee joint trajectory adjustment method in stancephase based on force feedback of the ground, and the foot trajectory planningmethod in flight phase. In the simulation study, virtual prototype quadruped robotkept balance under lateral perturbations and fastly crossed a rugged terrain.Finally, under the analysis and summary of virtual prototype simulation results,the joint driver mechanism based on crank-rocker mechanism and hydraulic cylinderwas built. On this basis, bionic leg was developde and verified by1D leg bouncingexperiment. A cableless quadruped robot prototype experiment platform wasestablished after the design of body structure, control systems and power units.Many experiment such as the lateral disturbance, flat surface walking and treadmillwalking were carried out, and the results verified that the control algorithm iseffective.