One of the most popular adaptive control techniques is gain scheduling technique. The overall gain of an open loop process is usually given as
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(V.33) |
It is customary to keep the overall gain constant. In case of changes in the process (or valve characteristics or measuring element), Kc should be tuned in such a manner that overall gain remains constant.
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(V.34) |
The above is called the gain scheduling control law.
When the process is poorly known, one cannot rely much on the correctness of the value of KÞ In such cases, the self-adaptive control may be helpful. A self adaptive controller optimizes the value of certain objective function (criterion) in order to obtain updated controller parameters. Two examples of self adaptive controllers are Model Reference Adaptive Control (MRAC) and Self-Tuning Regulator (STR)
V.7.1 Model Reference Adaptive Control
The following figure shows the schematic of a Model Reference Adaptive Controller.
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Fig. V.16: Model Reference Adaptive control |
