1 - The Basics

Abstract

A control system is a system that does tasks with minimum efforts. This chapter introduces two types of control systems: automatic and closed-loop control systems. Automatic control systems range from the highly intelligent and complex to absurdly simple ones. Each one of these systems automatically performs its task without direct operator intervention. A closed-loop control system measures its own output to determine what drive to apply to itself. Though the closed-loop control has some advantages, it presents some profound difficulties to the control system designer. The most dramatic disadvantage is instability. The chapter describes the parts of a closed-loop embedded control system. The software generates commands that are translated into an analog signal by the digital-to-analog converter (DAC). This low-power signal is amplified and applied to the plant. The plant contains an actuator to convert the electrical drive from the amplifier into some useful action in the plant. The plant output is connected to a sensor whose output is applied to an analog-to-digital converter (ADC). The ADC value is read by the control software, which uses this information and the command signal to determine the next drive command to the DAC.