Simplified motion modeling for snake robots

We present a general method of estimating a snake robot´s motion over flat ground using only knowledge of the robot´s shape changes over time. Estimating world motion of snake robots is often difficult because of the complex way a robot´s cyclic shape changes (gaits) interact with the surrounding environment. By using the virtual chassis to separate the robot´s internal shape changes from its external motions through the world, we are able to construct a motion model based on the differential motion of the robot´s modules between time steps. In this way, we effectively treat the snake robot like a wheeled robot where the bottom-most modules propel the robot in much the way the bottom of the wheels would propel the chassis of a car. Experimental results using a 16-DOF snake robot are presented to demonstrate the effectiveness of this method for a variety of gaits that have been designed to traverse flat ground.