Introduction

The term automation is used to describe the automatic operation or control of a process. In modem manufacturing there is an ever increasing use of automation, e.g., automatically operating machinery, perhaps in a production line with robots, which can be used to produce components with virtually no human intervention. Also, in appliances around the home and in the office there is an ever increasing use of automation. Automation involves carrying out operations in the required sequence and controlling outputs to required values.

The following are some of the key historical points in the development of automation, the first three being concerned with developments in the organization of manufacturing which permitted the development of automated production:

1. Modern manufacturing began in England in the 18th century when the use of water wheels and steam engines meant that it became more efficient to organize work to take place in factories, rather than it occurring in the home of a multitude of small workshops. The impetus was thus provided for the development of machinery.

2. The development of powered machinery in the early 1900s meant improved accuracy in the production of components so that instead of making each individual component to fit a particular product, components were fabricated in identical batches with an accuracy which ensured that they could fit any one of a batch of a product. Think of the problem of a nut and bolt if each nut has to be individually made so that it fitted the bolt and the advantages that are gained by the accuracy of manufacturing nuts and bolts being high enough for any of a batch of nuts to fit a bolt.

3. The idea of production lines followed from this with Henry Ford, in 1909, developing them for the production of motor cars. In such a line, the production process is broken up into a sequence of set tasks with the potential for automating tasks and so developing an automated production line.

4. In the 1920s developments occurred in the theoretical principles of control systems and the use of feedback for exercising control. A particular task of concern was the development of control systems to steer ships and aircraft automatically.

5. In the 1940s, during the Second World War, developments occurred in the application of control systems to military tasks, such as radar tracking and gun control.

6. The development of the analysis and design of feedback amplifiers, including the paper by Bode in 1945 on Network Analysis and Feedback Amplifier design, was instrumental in further developing control system theory.

7. Numerical control was developed in 1952 whereby tool positioning was achieved by a sequence of instructions provided by a program of punched paper tape, these directing the motion of the motors driving the axes of the machine tool. There was no feedback of positional data in these early control systems to indicate whether the tool was in the correct position, the system being open-loop control.

8. The invention of the transistor in 1948 in the United States led to the development of integrated circuits, and, in the 1970s, microprocessors and computers which enabled control systems to be developed which were cheap and able to be used to control a wide range of processes. As a consequence, automation has spread to common everyday processes such as the domestic washing machine and the automatic focusing, automatic exposure, camera.

This chapter is an introduction to the basic ideas involved in designing control systems with sections 18.2 through 18.7 being an introduction to the basic idea of a control system and the elements used.