Analytic Inverse Kinematics Model and Trajectory Planning for an 18 DoF Quadruped Robot

Kinematics modelling of robotic systems is a fundamental requirement used by the underling control system. In this paper, we introduce a complete and analytic direct and inverse kinematic model for an 18 DoF quadruped robot. The proposed solution, based on simple trigonometric functions, is analytically determined, allowing the full control of the translation and orientation of the footholds and of the body. Considering the fact that the dynamic model of the robot requires position, velocity and angular acceleration profiles as references, this article also presents the applicability of a trajectory generator with zero initial and zero final conditions for the first and second derivatives. As performance evaluation, we have determined the accuracy of the model by implementing a static gait controller on a A1 Unitree quadrupped robot, where the trajectory of each foot is calculated based on B-splines, given as reference to the inverse kinematics model