The Study Of Stability In Omni-directional Static Walking Of The Quadruped Robot And The Simulation

Legged robots possess larger environmental adaptability comparedwith wheel robots and can move omni-directionally in complicatedenvironments.They can thus be used for life-saving in a disaster strickendistrict,and as an operating machine in a construction field. Thequadruped walking robot is one of the most practical locomotion machinesto move about on uneven terrain and can keep good stability while walkingin static state. In the former researches of static omni-directionalwalking theory ,static omni-directional walking on a horizontal plane hasbeen realized by a successive gait-transition method.But,in theexperiment by setting duty factor equal to 0.75 of omni-directional staticwalking,the tilt phenomenon had been found occasionally in the processof gait transition.Based on the theory of omni-directional static walking of a quadrupedrobot,the stability of omni-directional static walking isanalyzed.According to the reason of unstable factors ,the solution ofeliminating the unstable factor is proposed. Specific research works areas follows:(1) Stability analysis. In response to this unstable phenomenon thatappears between gait transition menthioned upside,according to thedifference of the gait transition,the stability has been analyzed.Thenthe reason of the unstable factor has been found.When the quadruped robotmoving to the supporting leg diagonal,the stability margin becomeszero.In some cases of gait transition,it gets to zero instantaneously.Inother cases,it continues into zero.Since the difference of the COG betweenthe real and simulation model existed, the torso leansoccasionally,especially in the process of gait transition when thestability margin lasts to be zero.The phenomenon of leaning of quadrupedrobot should not appear in the practical applications,or it will greatlyaffect the stability and precision in the actual process of operation.(2)Specific solutions.In order to eliminate the phenomenon of leaning,different methods for the relevant pattern of gait transition have beenproposed.The method that giving a 4 legs'supporting period by setting duty factor larger than 0.75 and moving the COG in the 4 legs'supportingperiod can keep the stability margin always lager than zero.The solutiongives different ways to move the COG according the pattern of gaittransition.(3)Simulation.In this paper,through walking experiments by asimulator,the validity of the proposed approach has been verified. Withincrease of duty factor,it has been found that the minimum of the stabilitymargin can be improved significantly in the process of gaittransition.Moreover,the result of comprehensive successive gaittransition experiment shows that the quadruped robot can walk withpositive stability margin,when the approach of moving the COG in the 4legs'supporting period has been applied.Through the proposed new way,thestability margin can always be kept in a positive value in the staticomni-directional walking.