Reducing positioning uncertainty of objects by robot pushing

Robotic applications often involve manipulation of objects where position and orientation are not perfectly known. Pushing an object for instance by a fence, can be employed to accurately align parts, reducing uncertainty to only one degree of freedom. In this paper a pushing task involving two fingers that completely constrains an object in a plane is proposed. The stability of orientation and position of an object being pushed is discussed. The solution obtained is unique despite the fact that the distribution of forces supporting the object cannot, in general, be known. The proposed task of pushing is simple although some preliminary information about the initial position and orientation of an object is required. An approach to avoid the ambiguity in orientation, owing to the effect of friction between the object and the pusher, by introducing up and down movement of the pusher is also presented