Glow Plug Temperature Control via Resistance Gradient Adaptation
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Solution Overview
Problem
Existing methods for closed-loop control of glow plug surface temperature in internal combustion engines, particularly with ceramic glow plugs, suffer from poor precision due to manufacturing variations, making it difficult to accurately assign temperature to resistance and predict hot glow plug behavior based on cold resistance measurements.
Innovation Solution
The glow plug control device initializes by adapting the temperature model to the specific behavior of the installed glow plug, using measured resistances and resistance gradients to account for manufacturing tolerances, allowing for precise temperature control by estimating the momentary surface temperature during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a temperature model based on cold resistance is used for glow plug control, then the control system can be simplified, but the temperature control precision deteriorates due to manufacturing variations in ceramic glow plugs
Solution Approach 1:
The patent applies preliminary action by performing an initialization phase before normal operation where the actual hot resistance of the glow plug is measured and used to adapt the temperature model. This preliminary measurement of the actual resistance value and calculation of adaptation factors allows the system to compensate for manufacturing variations before precise temperature control begins, thereby achieving both simplified control structure and improved temperature precision.
Solution Approach 2:
The patent changes parameters by introducing adaptation factors (kR, kT) that modify the standard temperature model parameters based on the actual measured resistance. Instead of using a fixed temperature-resistance relationship from the ideal model, the system dynamically adjusts the model parameters to match the specific glow plug instance, resolving the contradiction between using a simple model and achieving precise temperature control.
2Measurement precision
If the temperature model is adapted to each individual glow plug, then the temperature control precision is improved, but the initialization process becomes more complex
Solution Approach 1:
The patent applies feedback by measuring the actual resistance of the installed glow plug during initialization and using this measured value to calculate adaptation factors that customize the temperature model. This feedback loop from measurement to model adaptation enables precise temperature control for each specific glow plug while keeping the initialization process structured and manageable through automated calculations.
3Difficulty of detecting and measuring
If cold resistance measurements are used to predict hot glow plug behavior, then the measurement process is simplified, but the prediction accuracy deteriorates due to strong variations in cold resistance from manufacturing
Solution Approach 1:
The patent substitutes the mechanical approach of relying on cold resistance measurements with an electrical measurement approach by directly measuring the hot resistance of the glow plug during initialization. This substitution replaces the indirect prediction method (cold resistance → temperature model) with a direct measurement method (hot resistance → adapted temperature model), thereby achieving both simplified measurement and improved prediction accuracy.
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 method enables accurate surface temperature control up to ±40°C, improving upon existing methods by accounting for manufacturing deviations and ceramic glow plug variations, ensuring precise temperature regulation without requiring additional engine operating variables.
Implementation Method 1
A model temperature is established in accordance with these input variables and corresponds to the surface temperature of the glow plug. A target resistance for the glow plug is established from the deviation of the model temperature from a target temperature and the current resistance of the glow plug is controlled to the target resistance
Implementation Method 2
the glow plug control device acts on the glow plug connected thereto with a pulse-width-modulated effective voltage
Data Source
AI summary
A method for controlling the surface temperature of any glow plug in an internal combustion engine. A glow plug control device carries out an initialization at the installed and connected glow plug to adapt the temperature model to the behavior of the connected glow plug before the engine is started. Upon initialization, the glow plug is acted on by at least two different voltages and the resistances of the glow plug with these voltages are measured. A resistance gradient is calculated therefrom and the temperature model is adapted to the behavior of the connected glow plug. During the control process during operation of the engine, the momentary surface temperature of the glow plug is estimated by a model temperature, which is established using the temperature model. The effective voltage acting on the glow plug is changed in accordance with the deviation of the model temperature from a target temperature.