It is an important job for an adaptive industrial robot to search the unknown position of an object. We propose the searching method using pneumatic proximity sensors. That is, the robot with the sensors at the tips of his fingers can detect an object continuously without contact and with flexibility for various sizes of objects by scanning sensors in accordance with a certain rule.
In this paper, we discuss the control method to drive the robot hand exactly to the center of an object, in the case of cylindrical objects or round holes whose diameters are unknown. In this case it is required to scan sensors from the center of the hand to radial directions in order to search the position regardless of the diameter of the object. We show this searching principle, and give the theoretical analysis about the limit of positioning error for all of the initial conditions. And we also show the experimental results of position searching to verify the theoretical limit, and consider the function of this method.