Balance Control Of Quadruped Robot Under Sudden-instability State

Quadruped robots that take advantage of walking stably in complicated, variable and unknown environment have become a hot spot of the robot research field. However, due to lack of effective strategies that meet the challenge of unstructured terrains and impact in the external environment, actually there are few quadruped robots which can adapt to complicated external environment. Taking a trotting quadruped robot as the research object and focusing on the issue of balance control for robot’s sudden instability that results from lateral impact, this thesis puts forward corresponding balance recovery strategies, which are verified by movement simulation platform. In the thesis the following work is accomplished:Firstly, a quadruped robot with 3-DOF legs is designed based on bionics theory, and subsequently the mathematical model is established. Kinematics analysis is carried out by applying the D-H method and dynamics analysis by using the Lagrange equation, and it’s the analysis that lays a foundation for the following research work.Secondly, enlightened by the motion of the quadruped mammal in the movement cycle, the movement of the trotting quadruped robot is designed and amplitudes of the hip and knee joint movement are given. The robot’s static stability is analyzed according to the concept of stability margin. The SLIP model for the quadruped robot of trotting is built, and then forward and lateral dynamic stability of the robot are analyzed by employing the law of conservation of energy.Lastly, a simulation platform for the quadruped robot of dynamic walking is built based on ADAMS, whereafter the movement simulation of the trotting robot under none of interference and lateral impact is made on the platform. In consideration of the quadruped robot’s sudden instability that results from lateral impact, this thesis designs a balance recovery basic algorithm based on two methods of roll compensated by the support leg’s stretch and foothold searched by the swing leg’s step, and then three balance recovery strategies are proposed: the strategy of the support leg adjusting attitude, the strategy of the swing leg stepping,and the strategy of two kinds of legs combined. In the end the rationality and reliability of the proposed strategies are verified by the results of the Adams simulation experiments.