New parameterized foot trajectory shape for multi-gait quadruped locomotion with state machine-based approach for executing gait transitions

This paper presents a method of generating adjustable robot foot trajectories to provide forward open-loop locomotion for different gaits of a planar quadruped robot. The trajectory is described by a small set of tunable parameters that are related to the motion animals perform. This allows faster and easier adjusting of the foot trajectories for different quadruped robots. This method was tested on a simulation model while performing different type of gaits: walk, trot, pace and bound gait. The proposed trajectory shape exhibited great results in simulation. Robot locomotion speed was controlled by scaling the obtained trajectory execution time. This way robot can achieve a wide range of speeds over all of the observed gaits. Additionally, a state-machine based approach for controlling trajectory execution and gait switching is presented. By covering a certain amount of possible events along with ground contact feedback, a quadruped can execute gait transition in a controlled way at overlapping configurations between gaits. The gait transition is performed by defining a set of rules which must be satisfied in order for the gait transition to take place. The simulation results have confirmed that robot maintains stable locomotion after executing gait transition.