Process control systems and methods having learning features

• US 8,412,357 B2
• Filed: 11/23/2010
• Issued: 04/02/2013
• Est. Priority Date: 05/10/2010
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Seem, John E.
• Primary Examiner(s): Bahta, Kidest
• Application Number:
  US12/953,283
• Publication Number:
  US 20110276180A1
• Time in Patent Office: 861 Days
• Field of Search: 700/28, 700 31- 33, 700/37, 700/43, 700275-274, 318/609, 623/05, 62/39, 621/84, 621/86, 702/85
• US Class Current: 700/38
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: G05B 13/0265 the criterion being a learning criterion
• CPC Class Codes: G05B 13/042 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

A system for operating a process includes a processing circuit that uses a self-optimizing control strategy to learn a steady-state relationship between an input and an output. The processing circuit is configured to switch from using the self-optimizing control strategy to using a different control strategy that operates based on the learned steady-state relationship.

Claims

1. A system for controlling a cooling tower that cools condenser fluid for a condenser of a chiller, comprising:

a cooling tower fan system that controllably varies a speed of at least one fan motor;

an extremum seeking controller that receives inputs of power expended by the cooling tower fan system and of power expended by the chiller, wherein the extremum seeking controller provides an output to the cooling tower fan system that controls the speed of the at least one fan motor, wherein the extremum seeking controller determines the output by searching for a speed of the at least one fan motor that minimizes the sum of the power expended by the cooling tower fan system and the power expended by the chiller;

a model-based controller for controlling the speed of the at least one fan motor;

a processing circuit configured to store process characteristics associated with a steady-state of the extremum seeking controller;

wherein the processing circuit is further configured to switch from using the extremum seeking controller to using the model-based controller to control the fan speed and wherein the processing circuit operates the model-based controller using the stored process characteristics.

2. The system of claim 1, wherein the processing circuit is configured to use the extremum seeking controller during an initial training period.

3. The system of claim 2, wherein the stored process characteristics associated with the steady state of the extremum seeking controller and used by the model-based controller comprise the part-load ratio at which the cooling tower operates at its capacity and the slope of the relative cooling tower airflow versus the part-load ratio.

4. The system of claim 3, wherein the processing circuit is configured to store the maximum part load ratio (PLR_max) during the training period and the minimum part load ratio (PLR_min) during the training period.

5. The system of claim 4, wherein the processing circuit is configured to monitor the part load ratio during the model-based control and wherein the processing circuit is configured to switch back to using the extremum seeking controller if the part load ratio exceeds PLR_max or drops below PLR_min during operation using the model-based controller.