Pattern Recognition Adaptive Control (PRAC+) Overview - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

Controller Tool Help

Johnson Controls
Product name
Controller Configuration Tool
Document type
User Guide
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PRAC+ is the Johnson Controls patented adaptive tuning algorithm that works with the Metasys PID control. PRAC+ examines the control loop output and system response when the PID is active, and continuously adapts the tuning parameters of proportional band and integral time. If there is a large oscillatory response (hunting), the tuning parameters are adjusted to make the response slower. If there is a small response and large error, the tuning parameters are adjusted to make the response faster. PRAC+ adaptive tuning responds when loads change due to any of the following:
  • time of day
  • day of week
  • season
  • heat exchanger or chiller fouling
  • general wear and tear of system components, such as valves and dampers
  • setpoint change

This process is completed by monitoring the process variable for patterns that contain tuning information, extracting features from those patterns, and using the features to determine the optimal tuning parameters. PRAC+ then steps the tuning parameters toward those optimal values—an amount based on the relative size of the present pattern (compared to past patterns).