One of important issues in modelling biomechanical and mechanical systems is presence of constraints which have to be considered in joints. These constraints cause all system's joint space points to be out of reach. This problem accompanies dynamic modelling and control of these systems with practical and theoretical complexities. In most studies and modellings it hasn't yet been accomplished accurately and completely. By not considering these constraints, system has been modelled and controlling methods have been applied on them. In this book, we want to analyse a constrained double pendulum and a constrained two-legged walking robot as samples of systems which this constraint exists in their movement. It will be shown that presence of selfimpact joint constraint in dynamical systems will improve their dynamical stability in compare with lack of this constraint. In this book for the first time multiple Lyapunov functions based switching control approach will be used for completecontrol of joint constrained walking robot. From controlling viewpoint with self-impact joint constraint two approaches will be of attention.