HVAC Loop Monitoring With Auto Retuning for Control Degradation
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Solution Overview
Problem
HVAC control loops often deteriorate due to lack of proper tuning, seasonal changes, hardware malfunctions, and disturbances, leading to compromised comfort, energy wastage, and premature actuator wear, necessitating automatic monitoring and re-tuning to maintain optimal performance.
Innovation Solution
A monitoring and diagnosis system that evaluates controller and loop performance using Predictability and Offset Indices, distinguishing between internal and external causes of poor performance, and triggering automatic re-tuning to maintain optimal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual tuning and maintenance are performed by installers, then control loops can be initially configured, but control quality deteriorates over time due to lack of proper tuning and maintenance
Solution Approach 1:
The control system performs self-diagnosis and self-tuning by automatically monitoring its own performance metrics and adjusting controller parameters without human intervention. The system evaluates control quality indicators, detects deterioration, and triggers retuning sequences autonomously, eliminating the need for manual maintenance while sustaining control reliability.
Solution Approach 2:
The system continuously monitors control loop performance using multiple indicators (offset index, predictability index, oscillation detection) and feeds this information back to automatically trigger retuning when quality deterioration is detected. This closed-loop feedback mechanism ensures control quality is maintained over time without requiring manual intervention.
2Reliability
If control loops are properly tuned initially, then control performance is optimal, but performance deteriorates due to seasonal changes, plant non-linearity, and hardware malfunctions
Solution Approach 1:
The control system dynamically adapts to changing conditions by continuously evaluating performance indicators and automatically retuning controller parameters in response to seasonal changes, plant non-linearity, and disturbances. The system transitions from static initial tuning to dynamic adaptive tuning, maintaining optimal performance across varying operating conditions.
Solution Approach 2:
The system autonomously detects performance deterioration caused by environmental changes and hardware issues, and self-corrects by triggering retuning sequences or generating maintenance alerts, eliminating the need for external intervention to adapt to changing conditions.
3Reliability
If automatic monitoring and re-tuning systems are implemented, then control quality is maintained over time, but system complexity increases
Solution Approach 1:
The monitoring and diagnosis system serves multiple functions: it evaluates control quality, detects oscillations, generates performance indicators, triggers retuning sequences, and provides maintenance alerts. By consolidating these diverse functions into a single integrated system, the patent reduces overall complexity while achieving reliable control quality maintenance.
Solution Approach 2:
The control system performs self-diagnosis and self-tuning, eliminating the need for external monitoring equipment and manual maintenance personnel. This self-service capability reduces system complexity by removing separate monitoring components while maintaining control quality through autonomous operation.
Data Source
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AI summary
A controller and loop performance monitoring system is coupled to a controller, detects loop performance degradation in time, and diagnoses a cause of the loop performance degradation. If the cause of loop performance degradation is poor controller tuning, a re-tuning mechanism is triggered. If the cause of loop performance degradation is external to the controller (a disturbance acting on the loop, hardware malfunction etc.), an action defined in control strategy is taken, or the user is informed via alarm, user interface, or upper layer software that collects the performance measures. The monitoring itself is designed to be recursive and with low memory demands, so it can be implemented directly in the controller, without need for data transfer and storage. The monitoring is modular, consisting of oscillation detection and diagnosis part, performance indices part, internal logic part, and triggering part, easily extensible by other performance indices or parts (e.g. for overshoot monitoring). The oscillation detection and diagnosis part includes controller output oscillation monitoring, the performance indices part includes predictability index and offset index. The outputs of the controller and loop performance monitoring are overall loop performance together with loop diagnosis information, and overall controller performance together with controller diagnosis. The outputs of the controller and loop performance monitoring are used as parts of controller and loop performance monitoring user interface.