This volume contain thirty-one papers based on talks delivered at the 4th Workshop of the Nonlinear Control Network (http://www.shef/?NCN4), held at The University of She?eld, 25¿28 June, 2001. We would like to emphasize one peculiarity of our ?eld: nonlinear control is an example of a theory situated at a crossroad between mathematics and engineering science. Due to this position, nonlinear control has its roots in both ?elds and, as we deeply believe, can bring new ideas and new results for both domains. The book re?ects very well this ¿double character¿ of nonlinear control theory: the reader will ?nd in it results which cover a wide varietyofproblems:startingfrompuremathematics,throughitsapplications to nonlinear feedback design, and all the way to recent industrial advances. The following delivered invited talks at the Workshop : Frank Allgower, Alessandro Astol?, Riccardo Marino Francoise Lamnabhi-Lagarrigue, Wei Lin and Malcolm Smith Altogether the book contains 31 papers and therefore it is impossible to mention here all the discussed topics.

The objective of the EU Nonlinear Control Network Workshop was to bring together scientists who are already active in nonlinear control and young researchers working in this field. This book presents selectively invited contributions from the workshop, some describing state-of-the-art subjects that already have a status of maturity while others propose promising future directions in nonlinear control. Amongst others, following topics of nonlinear and adaptive control are included: adaptive and robust control, applications in physical systems, distributed parameter systems, disturbance attenuation, dynamic feedback, optimal control, sliding mode control, and tracking and motion planning.