Solenoid Valve Switching Point Detection with First-Derivative Analysis
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Solution Overview
Problem
Existing methods for determining the switching point of a solenoid valve, such as through current profile analysis, often result in signal interference and require multiple parameter settings, leading to inaccurate identifications due to the need for second derivatives, which degrades signal quality.
Innovation Solution
The method involves analyzing the first time derivative of the current profile using overlapping periods with predefined temporal length to calculate a product of minimal and maximal values, determining the switching point based on the mean value of these points, thereby simplifying parameter selection and maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If second time derivative of current profile is formed to identify switching point, then switching point identification is achieved, but signal quality deteriorates due to interference amplification
Solution Approach 1:
The patent changes the evaluation parameter from second time derivative to first time derivative of the current profile. This parameter change reduces the amplification of signal interferences while still enabling switching point detection through characteristic curve maxima, thus resolving the contradiction between measurement precision and signal quality.
2Measurement precision
If multiple parameters are set for accurate switching point determination, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system automatically determines optimal evaluation parameters (temporal length, offset duration) based on the measured current profile characteristics without requiring manual parameter setting. The processing unit self-adjusts to find the maximum of the first time derivative within automatically defined periods, eliminating the need for complex parameter configuration while maintaining high measurement precision.
3Object-affected harmful factors
If first time derivative is used instead of second derivative, then signal quality is maintained, but switching point detection accuracy may be compromised
Solution Approach 1:
The patent defines predetermined periods with specific temporal lengths and offset durations before evaluating the first time derivative. This preliminary structuring of the evaluation window ensures that the maximum of the first derivative reliably corresponds to the switching point, maintaining detection accuracy while using only the first derivative and avoiding second derivative interference amplification.
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 accurately identifies the switching point with reduced signal interference and fewer required parameters, making it more adaptable and effective for specific applications like fuel injectors.
Implementation Method 1
Solenoid valves include a solenoid coil and a solenoid armature, which is raised or lifted by energizing the coil—a certain voltage is typically applied for this purpose
Implementation Method 2
the switching point may be recognized on the basis of the current profile through the solenoid coil, since the movement of the armature results in a steeper increase or kink in the current profile
Data Source
AI summary
A method for determining a switching point of a solenoid valve. A solenoid coil is energized to raise a solenoid armature to unblock a flow opening. For a signal profile characteristic of a current profile in the solenoid coil, multiple periods each different from one another and each having the same predefined temporal length are determined. Within each period, a minimal and a maximal value of the signal profile and associated points in time are ascertained and a product of a difference between the maximal and minimal value and a difference between the associated points in time are ascertained. On the basis of the points in time of the minimal and maximal value of that period, which corresponds to a maximal value of the product, the switching point is determined.