Autonomous Animation and Control of Four-Legged Animals

This paper develops a framework for the realistic autonomous animation and motion control of four-legged animals. Our system uses a combination of kinematics, dynamics and control theory. The input to our system, the velocity and heading of the animal, originates either from a simulated visual sensory system or a user. Based on this input we model walking, trotting, and simple behaviors such as target pursuit. we use a combination of kinematics, dynamics and control theory. A feedback controller, using the desired velocity and animal heading, computes the aggregate force and torque vector that should be applied to the body to achieve the given motion. This force and torque is distributed to the legs in contact with the ground through a linear programming algorithm. We then use forward dynamics to compute the actual body displacement. A kinematic gait controller is in charge of the stepping pattern. It arranges the stance and transfer phases of each leg depending on the current locomotion velocity, the turning rate and the ground conditions. Although we chose to focus on four-legged animals, the approach is generalizable to other multi-legged creatures or biped locomotion. Our motion system can currently simulate variable speed walking and trotting on flat or uneven terrain. Given its flexibility, the system can be used as a basis for more complex animations involving high level behaviors and interactions with other animals.