Modulating Valve Control Circuit for Gas Burner Hysteresis
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Solution Overview
Problem
Existing gas burner valve units suffer from hysteresis issues, leading to uncertainty in outlet pressure selection due to varying current values for the same force, and previous solutions like dithering require complex control circuits or non-constant dither signals, causing mechanical noise and wear.
Innovation Solution
A valve unit with a control circuit using a PWM signal generator that varies both duty cycle and frequency to maintain a constant amplitude of mechanical dither, ensuring precise pressure control by adjusting the duty cycle and frequency within an optimal range to minimize hysteresis and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dithering signal is applied to eliminate hysteresis, then pressure control precision is improved, but mechanical noise and wear increase due to non-constant dither amplitude
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the PWM frequency while maintaining a constant duty cycle during pressure transitions. This changes the operational parameters of the electromagnet to eliminate hysteresis effects without requiring variable amplitude dithering, thereby avoiding mechanical noise and wear associated with traditional dithering methods.
2Adaptability or versatility
If PWM frequency is varied to control electromagnet force, then pressure regulation flexibility is improved, but control circuit complexity increases
Solution Approach 1:
The patent implements dynamics by making the PWM frequency variable rather than fixed. The frequency is dynamically adjusted based on the required electromagnet force, allowing flexible pressure regulation. The control circuit responds to pressure sensor feedback and automatically modulates frequency, providing adaptive control without requiring complex external circuitry.
Solution Approach 2:
The patent employs feedback control where a pressure sensor continuously monitors the actual pressure and compares it with the target pressure. This feedback loop enables the control circuit to automatically adjust the PWM frequency to achieve the desired pressure, simplifying the overall control architecture while maintaining high flexibility.
3Reliability
If constant amplitude dithering is maintained during pressure transitions, then hysteresis is eliminated, but energy consumption increases
Solution Approach 1:
The patent applies periodic action through PWM modulation, where the electromagnet receives pulsed power rather than continuous power. By varying the PWM frequency, the system achieves the effect of dithering (periodic perturbation) to eliminate hysteresis while controlling the duty cycle to manage energy consumption. The periodic nature of PWM allows hysteresis elimination without requiring constant high-level power delivery.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates hysteresis effects, maintains precise control over gas outlet pressure, and reduces mechanical wear by ensuring the amplitude of mechanical dither remains constant, optimizing valve performance.
Implementation Method 1
the electromagnet (15) is supplied by a PWM signal generator (105) with a duty cycle and frequency which are varied in a controlled manner
Implementation Method 2
maintains a constant amplitude of mechanical dither, ensuring precise pressure control by adjusting the duty cycle and frequency within an optimal range to minimize hysteresis and wear
Data Source
Figure 1
Figure 2a~2b
Figure 3a~4b
AI summary
Valve unit (1) for controlling the feed of a combustible gas to a burner apparatus, comprising: a device (6) for regulating the pressure of the gas at the outlet of the unit, including a valve seat (7) associated with a plug (8), and an operating means (14) for causing the plug to move relatively to the corresponding valve seat, to regulate the outlet feed pressure (Pu) by modulation, the operating means comprising at least one electromagnet of the proportional type; a control circuit of the pressure regulating device including a PWM signal generator generating a PWM voltage signal adapted to generate a current signal in the electromagnet in order to move the plug as a function of the magnitude of the current signal and thus determine the outlet pressure, the magnitude of the current being a function of the duty cycle of the PWM signal; the PWM signal having a frequency such that the operating means is subjected to a mechanical dither having a specified amplitude at least for a specified time interval; the PWM signal generator including means of controlling the duty cycle and means of controlling the frequency of the PWM signal, the duty cycle control means varying the duty cycle of the PWM signal with the variation of the desired outlet pressure, and the frequency control means being adapted to vary the frequency of the PWM signal as a function of the variation of the duty cycle so as to keep the amplitude of the dither substantially constant, independently from the variations of the duty cycle of the PWM signal.