Combustion Sensor Drift Compensation in Closed-Loop Air Control
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Solution Overview
Problem
Combustion sensors, particularly ionization electrodes, experience signal drift due to ageing, necessitating frequent drift tests that disrupt operation and are time-consuming, especially when conducted outside defined support points.
Innovation Solution
A closed-loop control system with a memory that stores support points, drift test values, and indices for determining when to perform drift tests, allowing interpolation and weighting of test results to adjacent support points, thereby updating the regulating curve without requiring operation at defined points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If drift tests are performed frequently to correct sensor ageing, then measurement precision is maintained, but productivity decreases due to operational disruptions and time consumption
Solution Approach 1:
The system performs drift tests at predetermined intervals based on operating hours stored in the memory, rather than waiting for significant drift to occur. This preliminary correction approach maintains measurement precision while reducing the frequency and disruption of tests compared to reactive correction methods.
Solution Approach 2:
The control facility automatically determines when drift tests are needed based on stored operating hour data, and automatically performs the correction without requiring manual intervention. The system serves itself by monitoring its own operational state and initiating corrective actions, thereby maintaining precision while minimizing productivity impact.
2Adaptability or versatility
If drift tests are conducted outside defined support points, then adaptability improves, but device complexity increases due to interpolation and weighting calculations
Solution Approach 1:
The system uses interpolation between defined support points to determine drift test values at intermediate positions. This intermediary approach allows drift tests to be performed at any operating point while using the established support points as reference, thereby achieving adaptability without requiring completely new calibration data for every possible position.
Solution Approach 2:
The system changes the parameter of test position from fixed support points to continuous variable positions by implementing interpolation and weighting calculations. This allows the drift test to adapt to any current operating point while the underlying support point structure remains unchanged, balancing adaptability with manageable complexity.
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 allows for continuous correction of the regulating curve, reducing operational disruptions and time requirements for drift tests, maintaining accurate sensor performance by applying weighted test results to adjacent support points.
Implementation Method 1
the ionization current through an ionization electrode. Firstly, an alternating voltage is applied to the combustion sensor, in particular to the ionization electrode, in this case. Owing to the rectifier effect of a flame, an ionization current flows as a direct current in only one direction.
Data Source
AI summary
Various embodiments include a combustion apparatus comprising: a control facility for open- and/or closed-loop control of the apparatus; a combustion chamber; an actuator adjusting an air supply; and a combustion sensor in a region of a flame of the chamber. The control facility stores a list of support points. A first air supply value is assigned to each support point. A drift test value and an index for ascertainment of a test result are assigned to each support point. The controller: generates a specified air supply; selects a support point as a function of the air supply; and decides on a test result using the index for the support point. To ascertain a test result: receives a signal from the combustion sensor; determines a new test result; ascertains a changed drift test value for the selected support point; and stores the changed drift test value as the drift test value.