This book offers control engineers and researchers a unified framework for dynamic modeling and tracking control design of constrained mechanical systems. The final application of the framework is the development of a new tracking strategy, which is referred to as the model reference tracking control for programmed motion. It is dedicated to tracking tasks specified by equations of programmed constraints. This tracking strategy provides a unified approach to motion tracking for both holonomic and nonholonomic mechanical systems. It is based on two dynamic models. One is a reference model, which is a constrained dynamic model for a system subjected to arbitrary order nonholonomic constraints, and the second is a dynamic control model that includes material constraints only.