Walking Energy Cost Analysis And Compliant Walking Control Of Biped Robot

During the past half century,the motion ability of biped robot is getting better and better.However,the energy cost and robustness problems have been the outstanding obstacle in the biped robot's pragmatistic process.In this dissertation,a five-link planar biped robot with point feet is selected as the research object.In order to decrease the energy cost of biped walking and enhance its robustness,the walking energy cost and compliant contact control are discussed.The main contributions of the dissertation are as follows:1.To deal with the non-realistic problem of hypotheses used in most research,a nonlinear spring-damp model is used to model the foot-ground contact process,which avoids the discontinuity of contact force in linear model.Additionally,A 3D biped robot is built to get more realistic parameters of all the biped robot's links.Simulation results demonstrate the availability of the built simulation platform for biped walking.2.Considering the hybrid feature of biped walking,orbit stability is more valid to estimate the long time performance of biped walking.To cope with the problem that the accurate analytical solution of spring-load inverted pendulum mode is inaccessible.A virtual constraint type solution is proposed,in which the vertical position of the point mass is expressed by the function of the horizontal position.Simulation results show the approximate error is acceptable for a walking task.The step taking controllers are designed for the Variable Spring-Load Inverted Pendulum and Linear Inverted Pendulum model to realize orbit stable,respectively.The availability of the controllers are validated by simulation results.3.In order to deal with the problem that the actuator's energy cost has been ignored when the angular velocity is zero in traditional work based energy cost calculating method.A novel energy cost calculating method is proposed based on impulse.With this method,the energy costs of the stance leg and the swing leg are studied respectively.Simulation results show that the stance leg consumes less energy when the hip moves as LIP model,and the swing leg consumes less energy when the swing foot is lifted to the maximum height in the second half supporting phase.4.To cope with the problem that the structure may be damaged or become unstable by huge impact force when walking on uneven terrain,a position and posture control strategy with contact force control as the inner loop for under actuated system is proposed.With this control strategy,the balance and posture angle tracking control of a two link single leg are realized.At last,with the designed step taking controller for Linear inverted Pendulum and the results of energy cost analysis,stable biped walking on uneven ground is realized.