Control gain automation
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Solution Overview
Problem
Existing self-adapting controllers for HVAC systems face challenges in determining proportional, integral, and derivative parameters, particularly when dealing with zero actual flow, which can lead to division by zero errors, and require complex tuning processes.
Innovation Solution
A self-adapting controller that uses a characteristic function f(h) to determine valve stroke and employs a ratio of set-point flow to nominal flow, replacing actual flow with a nominal flow value when it reaches zero, and incorporates a microprocessor with analog-to-digital conversion and oversampling for precise flow measurement and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-adapting control algorithms use actual flow in the denominator to determine valve stroke, then control precision is improved, but division by zero errors occur when actual flow is zero
Solution Approach 1:
The patent introduces an intermediary variable (ratio of set-point flow to nominal flow) that mediates between the desired control precision and the avoidance of division by zero errors. This intermediary allows the system to maintain accurate valve stroke determination while preventing computational failures when actual flow is zero.
Solution Approach 2:
The patent changes the parameter used in the denominator from actual flow to nominal flow, which is a predetermined non-zero value. This parameter change ensures that the division operation remains valid while still allowing the control algorithm to adapt to actual flow conditions through the numerator (set-point flow).
2Measurement precision
If PID controller parameters are tuned to match specific environment, then control performance is improved, but tuning process becomes arduous and time-consuming
Solution Approach 1:
The patent implements self-service by enabling the controller to automatically determine its own PID parameters through the self-adapting algorithm. The controller uses the ratio of set-point flow to nominal flow to dynamically adjust proportional, integral, and derivative parameters without requiring manual tuning, thus eliminating the time-consuming tuning process while maintaining optimal control performance.
Solution Approach 2:
The patent applies dynamics by making the PID parameters dynamic rather than static. The controller continuously adapts the PID parameters based on the current operating conditions (ratio of set-point flow to nominal flow), allowing the system to automatically optimize control performance across different environments without manual intervention.
3Adaptability or versatility
If a generic control algorithm is designed to apply to wide range of fluid conveyors, then adaptability is improved, but complexity of handling zero flow cases increases
Solution Approach 1:
The patent achieves universality by designing a control algorithm that uses the ratio of set-point flow to nominal flow, which can be applied to any fluid conveyor regardless of its specific characteristics. The nominal flow serves as a universal reference value that exists for all conveyors, enabling the algorithm to handle zero flow cases uniformly across different applications without increasing complexity.
Data Source
Figure 1
AI summary
Control gain automation. A valve assembly comprising: a valve member (4) situated in a fluid path between an inlet port (2) and an outlet port (3), a flow sensor(7) for sensing one or more parameters related to a fluid flow through the fluid path; an actuator (5), a controller (9) for controlling the position of the valve member (4) via the actuator (5) in accordance with a set point, the controller (9) being configured to process signals to a flow rate, compare the flow rate to a predetermined threshold value indicative of substantially zero flow rate through the fluid path, and, if the measure of flow rate is less than or equal to the predetermined threshold value, determine a position of the valve member (4) irrespective of the position of the valve member (4) and (directly) based on a default flow rate, produce a control signal from the determined position.