Control of flow regulating device
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Solution Overview
Problem
Flow regulating devices in heating systems, such as valves, experience oscillations due to significant delays in actuating means when load conditions approach their limits, leading to inefficiencies and control issues.
Innovation Solution
A method using pulse width modulated control signals that adjust the open and closed periods based on load thresholds, ensuring the actuating means remains active even when the device is supposed to be closed at low loads and partially open at high loads, with thresholds varying by ambient temperature, and incorporating temperature sensors for feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control signals are used with actuating means having significant delay, then the flow regulating device can be controlled to adjust fluid flow, but oscillations occur when load approaches limits (valve near closing or full open position)
Solution Approach 1:
The patent applies periodic action by using pulse width modulated (PWM) control signals that switch between open and closed states in periodic cycles. The control signal is divided into full cycle periods with defined open periods (Po) and closed periods (Pc), creating a rhythmic switching pattern that prevents the actuator from lingering in intermediate states and eliminates oscillations near operational limits
Solution Approach 2:
The patent implements preliminary action by introducing dead time compensation that anticipates the actuator's delayed response. The controller pre-adjusts the control signal timing to account for the known delay characteristics of the actuating means, ensuring the valve reaches the desired position at the correct moment rather than reacting after oscillations have already occurred
2Adaptability or versatility
If the control signal reaches 0% or 100% at load limits, then the flow regulating device can be fully closed or fully open, but oscillations are triggered due to actuator delay
Solution Approach 1:
The patent applies local quality by implementing different control strategies for different operating ranges. Within the normal operating range (above low load threshold and below high load threshold), conventional control signals are used. However, when approaching the limits (below threshold or above threshold), the control signal transitions to PWM mode with specific open/closed period ratios, creating locally optimized control behavior for boundary conditions
Solution Approach 2:
The patent implements dynamics by making the control signal characteristics adaptive rather than static. The controller dynamically switches between conventional control and PWM control based on the current load position relative to thresholds. The open period (Po) and closed period (Pc) are dynamically adjusted based on whether the load is below the low threshold or above the high threshold, allowing the system to adapt its control behavior to current operating conditions
Data Source
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AI summary
A method to control a fluid flow regulating device being regulated through a control signal ranging from 0-100% during a normal operational load, defined as being within a given load threshold, where said control signal is 0% when said flow regulating device is to be closed and 100% when it is to be open, but when said load gets outside said load threshold the control enters a modified control where said control signal either is never at 0% and/or is never at 100%. A controller including said control method.