A classification of stability margins for walking robots

Throughout the history of walking robots several static and dynamic stability criteria have been defined. Nevertheless, different applications may require different stability criteria and, up to the authors ’ best knowledge, there is no qualitative classification of such stability measurements. Controlling a robot gait by means of using the wrong stability criterion may prevent the task from succeeding. By the other hand, if the optimum criterion is found the robot gait can also be optimized. In this work, the stability criteria that have been applied to walking robots with at least four legs are examined attending to the stability margin on different static and dynamic situations. As a result, a qualitative classification of stability criteria for walking machines is proposed so that the proper criterion can be chosen for every desired application.