Chapter three

Introduction to feedback

Section one: Introduction to Feedback

This chapter is on the theme of linear feedback control. For example, with G(s) representing a system, M(s) a compensator and d an input disturbance signal:

This section focuses on an introduction to the concepts of feedback. Why is it needed? How do we conceptualise and implement feedback? What is the impact on behaviour and hence, through examples, some motivation for more systematic analysis.

1. Why is feedback important?

A number of simple examples illustrating how the use of feedback is everywhere and essential to ensure effective functioning of our world and devices we use.

A talk through video is on YouTube. Read the notes (PDF, 652KB).

2. Human feedback

A simplistic insight into how humans use feedback to control the world around them. The concepts learnt here underpin how we could implement automated feedback to save human labour and improve efficacy.

A talk through video is on YouTube. Read the notes (PDF, 477KB).

3. Feedback implementation

This section illustrates the components and structures needed to implement and automate a typical feedback loop.

A talk through video is on YouTube. Read the notes (PDF, 504KB).

4. Impact of feedback

This section demonstrates through simple examples how introducing feedback changes the way systems behave. It is mostly focussed on concepts and some simple engineering illustrations.

Two talk through videos are on YouTube (video one, video two).

Feedback has an impact notes (PDF, 647KB).

Feedback impact case study notes (PDF, 578KB).

5. Feedback impact analysis

An introductory and concise overview of how simple proportional feedback changes the behaviour of first, second and high order systems. Use the analysis section to see more detail and derivations.

Impact on first order systems video and notes (PDF, 494KB).

Impact on second order systems video and notes (PDF, 593KB).

Impact on high order systems video and notes (PDF, 587KB).

6. MATLAB tools

This section summarises some basic MATLAB commands that can be used to help in the analysis of simple feedback systems.

MATLAB commands for feedback notes (PDF, 522KB).

Slower and more detailed explanations.