No abstract

No abstract

ISBN 0-7923-9133-0. Reviewed by Andres Soom 1Tribologists are accustomed to thinking in terms of the steady state behavior of sliding or rolling contacts with respect to load-carrying capacity, wear, and overall energy losses to friction. Although time-varying behavior is important in many applications, our ability to model such behavior, particularly during transitions between boundary, mixed, and full film lubrication, remains limited. One application area of considerable technological importance is motion and force control, wherein smooth and accurate actions may need to be achieved, during acceleration from rest and at low speeds. This timely Professor, and readable monograph by Professor Armstrong-Helouvry, is directed toward friction modeling for such applications.The treatment, which draws extensively from both the tribology and control engineering literature, combines experiments and comprehensive mathematical models to describe stick-slip behavior of a robot arm. However, the work has broader implications to transient friction modeling and points the way to a number of research topics relevant to control and other dynamic applications involving lubricated friction.It is shown how three effects: (i) the micro-slip region preceding gross slip (called the Dahl effect, here), (ii) a dwelldependent static or break-away torque, and (iii) temporal delays between changes in sliding speed and corresponding changes in friction cause deviations from steady friction behavior and influence the overall dynamic behavior of the system. A perturbation analysis that agrees with measured occurrence of stick-slip provides persuasive evidence of the roles played by these effects.Although this monograph cannot be considered to be a definitive work on the topic, it should be read by all tribologists interested in time-dependent friction phenomena.

The PUMA 560 robot is the white rat of robotics research -it has been studied and used in countless experiments over many years and in many laboratories. However, it remains a challenge t o assemble the complete data needed f o r model-based control of the robot.This paper presents a numerical comparison of kinematic, dynamic and electrical parameters f o r the PUMA 560 robot which have been reported in the literature. For the first time, data f r o m several experiments are presented in a single system of coordinates, which facilitates comparison. Diflerences in the data and ihe various methods of measurement are discussed. New data have been gathered and are presented where the record was incomplete.

No abstract