QxDesign--Observers in Control Systems

You can use observers to
improve your control system.

Published by Academic Press in September, 2002.

Observers in Control Systems shows how you can use observers to improve control system performance. Observers are algorithms that combine sensor outputs with system knowledge to measure feedback signals better than the sensor can alone. When used in control systems, observers can produce results that are far superior to traditional structures. Observers have been used in selected industries for years, but most books use abstract mathematics to apply them to highly complex systems. This book uses intuitive discussion, software experiments, and supporting analysis to show how observers can improve common control systems. If you are working in controls and want to improve your systems, observers could be the technology you need and this book will give you a clear, thorough explanation of how they work and how to use them.

Features of this book:

Teaches observers from an intuitive approach; avoids unnecessary mathematics
Numerous practical applications of observers to control systems
Based on virtual laboratory--key topics are demonstrated with over two dozen models of control systems.
The models are written in Visual ModelQ, a fully-graphical modeling environment that is available free of charge via the Internet to every reader with a PC
Provides discussion of electronic motion control including details on how motors and motor feedback devices work, causes and cures mechanical resonance, and shows how position loops work

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Download the Visual ModelQ companion to Observers in Control Systems

Errata

From the Introduction of Observers for Control Systems

Control systems are used to regulate an enormous variety of machines, products, and processes. They control quantities such as motion, temperature, heat flow, fluid flow, fluid pressure, tension, voltage, and current. Most concepts in control theory are based on having sensors to measure the quantity under control. In fact, control theory is often taught assuming the availability of near-perfect feedback signals. Unfortunately, such an assumption is often invalid. Physical sensors have shortcomings that can degrade a control system.

There are at least four common problems caused by sensors. First, sensors are expensive. Sensor cost can substantially raise the total cost of a control system. In many cases, the sensors and their associated cabling are among the most expensive components in the system. Second, sensors and their associated wiring reduce the reliability of control systems. Third, some signals are impractical to measure. The objects being measured may be inaccessible for such reasons as harsh environments and relative motion between the controller and the sensor (for example, when trying to measure the temperature of a motor rotor). Fourth, sensors usually induce significant errors such as stochastic noise, cyclical errors, and limited responsiveness.

Observers can be used to augment or replace sensors in a control system. Observers are algorithms that combine sensed signals with other knowledge of the control system to produce observed signals. These observed signals can be more accurate, less expensive to produce, and more reliable than sensed signals. Observers offer designers an inviting alternative to adding new sensors or upgrading existing ones.

This book is written as a guide for the selection and installation of observers in control systems. It will discuss practical aspects of observers such as how to tune an observer and what conditions make a system likely to benefit from their use. Of course, observers have practical shortcomings, many of which will be discussed here as well. Many books on observers give little weight to practical aspects of their use. Books on the subject often focus on mathematics to prove concepts that are rarely helpful to the working engineer. Here the author has minimized the mathematics while concentrating on intuitive approaches.

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