Quadruped Robots Dynamic Modeling and Foot-Ground Contact Analysis by Using Reduced Multibody System Transfer Matrix Method

The dynamic analysis of quadruped robots is crucial for enhancing their motion control performance, and such analysis is reliant on the advanced multi body dynamics theory. The Reduced Multibody System Transfer Matrix Method (RMSTMM) distinguishes itself from other dynamics approaches as it does not necessitate the formulation of the global dynamic equation of the system. Additionally, this method offers advantages such as low matrix order, rapid computational speed, and high programmability. In this paper, the RMSTMM is employed to construct a 18 degrees of freedom quadruped robot full-body dynamic model, as well as the reduced transfer equations and recursive simplified transfer equations of each component. On this basis, the foot-ground contact force model under the condition of hard ground is established. The normal contact model between the foot and the ground of the quadruped robot can be described by the classical spring damping model. The smooth interpolation function based on the quintic polynomial is introduced to avoid the jump of the force. When calculating the tangential friction force, the regularization model is introduced on the basis of the basic Coulomb friction, so that the static friction force and the dynamic friction force can be expressed and calculated more accurately. The above analysis process verifies the accuracy of the model through simulation, which can be successfully applied to the whole body dynamics calculation of quadruped robot and the foot-ground contact research on hard ground.