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In this chapter we present a collection of examples spanning many different fields of science and engineering. These examples will be used throughout the text and in exercises to illustrate different concepts. First time readers may wish to focus only on a few examples with which they have the most prior experience or insight to understand the concepts of state, input, output, and dynamics in a familiar setting.
This chapter describes a collection of examples that illustrate some of the diverse applications of feedback.
The cruise control system of a car is one of the most common control systems encountered in everyday life. The system attempts to keep the speed of the car constant in spite of disturbances caused by changing slope of the road and variations in the wind and road conditions. The system measures the speed of the car and adjusts the throttle.
The dynamics of a bicycle provide an example of how simple models can be used to give important insights into the behavior of a complex system. Using simple models, we can understand how tilting a bicycle affects its motion and stability properties.
The operational amplifier (op amp) is a modern implementation of Black's feedback amplifier. It is a universal component that is widely used for for instrumentation, control, and communication. It is also a key element in analog computing.
Web server admission control is used to help regulate the flow of requests to a web server and insure good performance even under high load. A continuous time model can be used to understand nonlinear feedback strategies for improving the performance of the system.
Atomic force microscople are used to provide molecular-scale imaging by moving an atomically sharp tip across a sample. Feedback is used to maintain a constant force on the sample and provide a signal that describes the height of the surface.
Drug administration involves maintaining the concentration of a drug in one's body by control the rate at which drugs are given. Compartment models allow analysis of the rate of diffusion of the drug in the body.
Population dynamics allow prediction of species populations in controlled and natural ecosystems. The models for these systems are often nonlinear in nature and include effects such as birth rates, environmental capacity limits and predators.