Systems and methods for improving building control systems via command compensation
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Solution Overview
Problem
HVAC systems face challenges in maintaining consistent water flow through valves due to pressure disturbances, leading to instability in temperature control, as existing systems struggle to adjust valve positioning accurately when the required flow is smaller than what the sensor can read.
Innovation Solution
A temperature control system incorporating a flow sensor, an actuator, and controllers that utilize a weighted linear combination of commands from temperature and flow controllers to adjust valve positioning, with the weighting based on the reliability of the flow sensor, ensuring reliable operation even when the sensor provides inaccurate readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow sensor is used to monitor fluid flow through the valve, then measurement precision is improved, but reliability deteriorates when the sensor provides inaccurate readings due to pressure disturbances
Solution Approach 1:
The patent introduces an intermediary computation process that combines multiple flow commands (first flow command from temperature controller and second flow command from flow controller) with weighted values based on sensor reliability. When the flow sensor provides inaccurate readings, the system automatically reduces its weight and relies more on the temperature controller's flow command, thereby mediating between conflicting control signals and maintaining system reliability.
Solution Approach 2:
The system dynamically changes the weighting parameter of the flow sensor based on its reliability assessment. The weight of the flow sensor's second flow command is adjusted according to whether the sensor is providing accurate or inaccurate readings. This parameter change allows the system to adapt to varying sensor reliability conditions and maintain optimal control performance.
2Quantity of substance
If the valve adjusts flow based solely on flow sensor feedback, then fluid flow control is improved, but temperature control stability deteriorates when pressure disturbances occur
Solution Approach 1:
The patent merges the control outputs from two separate controllers: the temperature controller (first controller) and the flow controller (second controller). The final control signal is a weighted combination of the first flow command from the temperature controller and the second flow command from the flow controller. This merging allows the system to benefit from both temperature-based and flow-based control strategies, maintaining temperature stability even when flow measurements are disturbed by pressure changes.
Solution Approach 2:
The system implements a feedback mechanism where the reliability of the flow sensor is continuously assessed based on the consistency between the flow sensor's measurements and the expected flow behavior. When pressure disturbances cause sensor inaccuracies, the feedback loop automatically reduces reliance on the flow sensor and increases reliance on the temperature controller's commands, thereby maintaining overall system stability.
3Manufacturing precision
If the system relies on flow sensor readings for control commands, then flow control accuracy is improved, but system reliability deteriorates when the sensor is consistently unreliable
Solution Approach 1:
The patent implements a dynamic control architecture where the weighting between different control commands changes in real-time based on sensor reliability. The system transitions from a static reliance on flow sensor feedback to a dynamic combination of multiple control strategies. When the flow sensor is consistently unreliable, the system dynamically shifts to rely more on the temperature controller's flow commands, ensuring continuous reliable operation.
Solution Approach 2:
The system prepares for potential sensor failures by having a pre-established alternative control path through the temperature controller. The weighted combination mechanism is designed in advance to automatically compensate for sensor unreliability without requiring manual intervention or system reconfiguration, providing beforehand cushioning against the harmful effects of sensor failures.
Data Source
AI summary
A temperature control system. The control system includes a flow sensor configured to monitor water flow through a valve, an actuator coupled to the valve, and a first controller configured to establish a setpoint for a second controller. The second controller monitors fluid flow through the valve and combines a weighted first command from the first controller and a weighted second command from the second controller to generate a control signal, wherein combining the weighted first command and the weighted second command is based on the reliability of the flow sensor. The second controller further controls the actuator based on the control signal.