Three-Dimensional Stability Criterion of Integrated Locomotion and Manipulation
Kan Yoneda and Shigeo Hirose
Department of Mechano-Aerospace Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguroku, Tokyo 152, Japan
This article discusses judging robot stability in manipulation and locomotion. The conventional relationship between center-of-gravity projection points and grounding points is easy to use but gives no consideration to counterforce manipulation. Theoretically, the ZMP concept of standard dynamic stability can handle counterforce manipulation, but moments considered are limited to two-dimensional planes, making it applicable only to flat land or areas which have two or more ground points at the same height and therefore not applicable to ordinary uneven land. We propose a “tumble stability” concept that deals with three-dimensional stability, taking into consideration tumble directions when grounding points, other than a certain pair, disappear virtually. If any such ground points can generate support for controlling tumbling, the locomotive mechanism would not tumble. If no such single grounding point can generate support for curbing tumbling, then the mechanism would tumble in a way similar to reality. Given this, stability during manipulation can be judged by handling counterforce manipulation as external, for flat land and for manipulation in three-dimensional uneven contours, walls, and ceilings. We introduces the counterforce manipulation limit concept as an index for indicating manipulability. This is the limit of counterforce against which manipulation can be stably effected and an effective method for raising manipulative capability may be to take grounding points opposed to manipulation at far areas.