Two dimensional dynamic stability for reconfigurable robots designed to traverse rough terrain

Robots must be designed with consideration for reconfiguring body pose during operation if they are to address more challenging environments. Researchers have mostly relied on static stability methods to monitor the possibility of rollover in stationary or slow moving vehicles. However, little research in dynamic stability is being conducted for robots capable of reconfiguring their pose to overcome obstacles encountered in challenging terrains. A multi-degree-of-freedom robot with the capability to vary its center of gravity is discussed in this paper. It is designed to improve mobility over rough terrain and is used in this paper as an example to address one aspect of dynamic stability. A complete understanding of the dynamic behaviour of a multiple degree of freedom robot in unstructured terrain is a difficult problem to solve. It is too complex to solve completely and therefore a reduced aspect of the problem is addressed. The robot will only have the ability to vary its center of gravity in the plane parallel to its direction of forward motion. In addition the robot will only move on flat terrain and encounter an immovable linear step feature. The result of the research is that once the center of gravity is specified by selection of robot body pose, and a maximum obstacle considered, platform stability can be ensured with a maximum allowable velocity. In other words, a maximum allowable velocity of the robot is governed by the position of the center of gravity relative to the wheel in contact with the linear step feature. If the robot is traveling below the predetermined maximum velocity then the robot is guaranteed to remain upright.