Whole-body bound gait control of a quadruped robot equipped with an active spine joint

Official URL: https://risc01.sabanciuniv.edu/record=b2708488_(Table of contents)

Legged robots stand out with their maneuverability and terrain adaptability potential owing to their articulated limb structure. Quadrupeds have considerable advantages on rugged terrain over wheeled and tracked robotic land platforms. They have virtues when employed for tasks in diverse environments. Still, commissioning quadruped robots is not a straightforward process. These robots have not only high degrees of freedom but also complex and non-linear dynamics. Nature provides us knowledge about how animals choose and vary their gait according to their locomotion speed while keeping their balance and utilizing their energy efficiently. Hence, quadruped robots need to perform a variety of gaits, including static and dynamic ones, during their assignments. Spine articulation is mainly put to work for fast, dynamic animal gaits. Spinal motion is also instrumental in gait to gait transitions. Therefore, adding an active spine to a quadruped robot is an effective way to boost its dynamic motion performance. Nonetheless, the additional degrees of freedom increase the complexity of the system. A complicated set of challenges has to be met for employing spine joints effectively. This dissertation presents a study on the dynamic bound gait of a quadruped robot equipped with a spinal joint. Motion generation is carried out by forming reference contact forces. Contact forces are planned with linear and angular momentum laws and impulse equations. Suitable contact forces are produced by an optimization algorithm. As an optimization solver, sequential quadratic programming is utilized. A hybrid force-motion control framework is created in the operational space for tracking generated references. A gait phase transition method is devised for the application of force and position controllers. To test the proposed method, a full-dynamics 3D simulation environment is built. The equations of motion of the quadruped robot are obtained by the Newton-Euler and the Lagrangian approaches. A linear complementarity problem is cast to develop constraint-based contact physics for ground interaction modeling. Simulation results verify the performance of the proposed whole-body motion control method.