A CLASS OF OPTIMAL FEEDBACK CANAL CONTROLLERS, INCLUDING PROPORTIONAL- INTEGRAL AS A LIMITING CASE

Authors: Clemmens, Albert; SCHUURMANS, J - UNIV OF TWENTE, NETH

Submitted to: Workshop on Modernization of Irrigation Water Delivery Systems
Publication Type: Proceedings
Publication Acceptance Date: 10/21/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Water is becoming a scarce resource, and water districts are under pressure to use water more judiciously. Improved operation of water resources facilities, such as canals and reservoirs, has been touted as necessary for making proper use of these limited water supplies. Operation of irrigation- water delivery systems can be improved by providing canal operators with better tools for determining control actions. One such tool is computerize automatic control of canal gates. While canal automation may appear simple in concept, it is actually a complex technical problem. This complexity has led to a large gap between theory and practice. This paper presents a method for designing and tuning a variety of simple canal controllers. The method can be used to help determine the level of controller complexity required for a particular canal. These results should be of use to irrigation districts, consultants, and the Bureau of Reclamation.

Technical Abstract: There have been two basic approaches to the development and tuning of downstream canal control algorithms. The first is the use of a series of classical or heuristic controllers in series, one per canal pool. The main limitations of these methods are that the controllers need to be tuned manually, which is difficult, and the resulting performance is not very good. Second is the use of models and optimization to define the controlle (e.g., Linear Quadratic Regulators or LQR). The main limitations of this method are 1) it appears to the operator as a "black box," whose logic cannot be understood, and 2) it does not take input limitations into account, which may lead to operating problems. A new class of optimal controllers is proposed that can vary from a series of individual proportional-integral (PI) controllers (one per pool) to fully centralized controllers. Since these controllers are tuned for the entire canal (i.e., centrally), a series of simple, local individual-pool PI controllers can b tuned optimally. A variety of different controllers can be directly compared without simulation since the same criteria are used to tune each controller. An example is provided.