Mechatronics Control Devices

Mechatronic control devices are found everywhere; they are built into kitchen appliances, aircraft, cameras, computers, power stations, even in toilet cisterns. They may be built from micro-circuits, mechanical levers, hydraulic or magnetic devices. Though they come in diverse forms, the aim is the same—to regulate or control the behaviour of the machine or process they are part of. They often behave in strange ways, particularly when they go wrong. People often find them hard to understand. Fortunately, we can learn to understand their behaviour with a common set of fundamental principles. We can find examples of control devices in everyday life and learn to observe them to gain a better appreciation of these principles. Most reference material on control is highly technical and specialized, and often far removed from practical application. Control is a concept which extends beyond the boundaries of any one technical discipline. This article explains the fundamentals of control so that the reader can apply them, or learn more from detailed technical references. Examples of control devices are drawn from everyday life, with a few uncommon examples to extend the imagination. The reader will also be able to appreciate the practical limitations of control devices and what happens when they go wrong. Apart from working models, computers provide a useful way to explore control system behaviour. The article shows some simple ways to do this using software. Introduction To understand how servo and control devices work, we need to think about the machines or processes they regulate. We can then think of a control system 1 which comprises the control device and the regulated machine or process. When we drive a car, we form a control system comprising ourselves (controller) and the car on the road (process). Control engineering is the technology of control systems: it is a pervasive technology. It surrounds us and we rely on it for so many of our basic needs. Control systems keep electric generators turning at exactly the right speed to provide a constant frequency of alternating current in our electricity supply. Hydraulic and electrical control systems keep aircraft and transport systems running. Other systems ensure the continuity of our water supply, control the temperature and environment inside our buildings and regulate the production processes which produce the material goods we use in our everyday lives. Yet control is even more pervasive than this, for our own bodies contain control systems. …