Book excerpt: This book discusses the dynamic analysis of rigid-flexible robots and multibody systems with serial as well as closed-loop architecture. The book presents a formulation of dynamic model of rigid-flexible robots based on the unique approach of de-coupling of natural orthogonal complements of velocity constraints. Based on this formulation, a computationally efficient and numerically stable forward dynamics algorithms for serial-chain and closed-loop robotic systems with rigid or flexible or rigid-flexible links is presented. The proposed algorithm is shown to be a numerically efficient for forward dynamics based on the investigation methodologies built on eigen value analytics. Precision and functionality of the simulation algorithms is presented/illustrated with application on different serial and closed-loop systems (both planar and spatial types). Some of the major robotic arms used to illustrate the proposed dynamic formulation and simulation algorithms are PUMA robot, Stanford robot arm, and Canadarm. It is envisaged that the book will be useful for researchers working on the development of rigid-flexible robots for use in defense, space, atomic energy, ocean exploration, and the manufacturing of biomedical equipment.