This book was created for the Ryerson course ELE639: Control Systems, a third year course in Electrical & Computer Engineering Program at Ryerson University. The book has been adapted from the ELE639 Course Notes as they evolved over the years, and is organized to reflect the content taught in this introductory course in control theory. It covers the following topics: system modeling, simulation, analysis and controller design; transfer function representation of linear, time-invariant, continuous time systems, block diagrams and signal flows; dynamic properties in time and frequency domains; performance specifications; basic properties of feedback; stability analysis: Routh-Hurwitz criterion, Root Locus method, Bode gain and phase margins, Nyquist criterion; classical controller design in time and frequency domain: lead, lag, lead-lag compensation, rate feedback, and PID controller.

**Definitions:**

**System** – a collection of objects arranged in an orderly fashion, which is goal-oriented. The system is also referred to as the plant, or process. Examples of systems – industrial robot, car, power turbine, induction furnace, motor, but also human body, corporation, and traffic flow. Systems differ from objects (such as tools) in that they have a certain level of complexity and a power source.

**Control** – used whenever some quantity, such as temperature, altitude or speed, must be made to behave in some desirable way over time. For example, control methods are used to make sure that the temperature in our homes stays within acceptable levels in both winter and summer; so that airplanes maintain desired heading, speed and altitude; and so that automobile emissions meet specifications.