Impulsive Manipulation

Impact is a complicated phenomenon. A collision lasts for only a short period of time but results in tremendous forces and accelerations during that time. The fact that so many sports and games involve impact reflects the both the power and the difficulty in using it. This thesis studies the use of impulsive forces to manipulate objects in order that the methods, techniques, and strategies of this mode of manipulation can be transferred to robotic manipulators. The particular form of impulsive manipulation that I have studied in this thesis is tapping planar objects which then slide on a support surface, coming to rest due to friction. The mechanics of impact and friction are first analyzed in order to plan single taps that achieve some desired translation and rotation. This solution is then extended to plan multiple tap sequences and to characterize the controllability of objects under this form of manipulation. The analysis culminates with the study of vibratory manipulation — the use repeated impacts for manipulation, particularly a high frequency low amplitude series of impacts. Experiments are a major part of this work. The experimental effort started with the design of specialized tapping devices that deliver a single controlled repeatable impact. Over the course of this work, a number of different devices were designed, built, and tested; this thesis describes these devices and the issues that were important in their design. The first experiments were single tap experiments, designed to test how well the models predict object motion for a variety of different objects and support surfaces. The next experiments demonstrated positioning via tapping. These experiments required the adaptation of the basic planning method developed in the analysis in order to explicitly consider practical issues such as errors and tapping device limitations. The resulting planning methods lie somewhere in between traditional planners and feedback control systems. The culmination of the experimental effort was a demonstration that it is possible to position an object via tapping more precisely than the tapping device itself is positioned.