Embedded Digital Control with Microcontrollers

11Adaptive Control

Adaptive control provides another perspective to design a controller for the system at hand. Therefore, it deserves special consideration. In this chapter, we will explain adaptive control concepts starting from general layout. Then, we will continue with parameter estimation. Afterward, we will introduce indirect self-tuning regulator (ISTR) and model-reference adaptive control (MRAC) as two different approaches in adaptive control. Finally, we will provide an end of chapter application as the real-time parameter estimation of a given system, the DC motor for our case.

11.1 What is Adaptive Control?

A well-designed closed-loop controller can work efficiently in most applications. However, there may be changes in the system or environment during operation. As the first case, system characteristics may change over time. So, it may not be possible to control it as desired. Therefore, controller parameters should be adjusted to compensate variations of the system. The first step here should be finding the new parameter values. To do so, parameter estimation can be applied on the fly. This is system identification, as explored in Section 11.2, now in real-time. Then, the controller can be modified for the changed parameters. As the second case, the environment may change. There, we may need to update the controller to compensate these changes. For both cases, the controller should adopt itself to changing conditions. Hence, we will have the adaptive controller. ...