Variable structure systems, or sliding mode control systems, are non-linear automatic control systems whose structures are deliberately allowed to change, so that robust performance is obtained. It allows the design of high performance control systems that can be reliably and easily implemented at low cost. Although the basic theory is mature, the theory and the associated control system design methodologies are less well known to many control engineers. This new text seeks to redress the gap, and is split into three parts: the basics of sliding mode control, new trends in sliding mode control and applications of sliding mode control. The book will be of interest to all engineers working with control systems. Mathematical and engineering concepts are discussed thoroughly and many numerical design examples are included so that readers can quickly understand the design methodologies and their application to practical problems.