Notes on Control with Delay

We gather together some introductory and tutorial material on control systems with delay. Delay is especially pernicious in feedback systems, and some form of modeling and prediction is essential to overcome its effects. After a short introduction to tbe issues, we present four basic techniques for overcoming delay and compare their performance through simulation. The four techniques are the following. • Predictive techniques to cancel the delay within the loop. • Cancel negative feedback to obtain open-loop characteristics. • Smith prediction, which uses a model of the plant. • System inversion techniques, which use a model of the controller and the plant. In each of these techniques, predictive filters can be used to overcome latency by providing approximate dynamic predictions of waveforms within the system, such as input and control signals. This material is based on work supported by the National Science Foundation under Grants numbered IRI-8920771 and CDA-8822724. The government has certain rights in this material.