Vehicle Wastewater Level Measurement Using Binary Bubble Signals
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Solution Overview
Problem
Conventional methods for determining the filling level of wastewater in vehicle tanks, such as capacitive meshes and pressure sensors, face challenges like measuring errors due to deposits and temperature dependencies, especially in small tanks, leading to inaccuracies.
Innovation Solution
A method using binary filling signals from multiple measuring positions, where the filling level is determined as a sum of a basic filling quantity and an inflow quantity, with the basic quantity selected based on active signals and the inflow quantity calculated from flushing processes, allowing for precise measurement through interpolation and accounting for uncertainties in flushing quantities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive measuring meshes are used for filling level measurement, then the measurement can be implemented in waste water tanks, but deposits on the tank walls give rise to measuring errors
Solution Approach 1:
The patent replaces capacitive electrical measurement with a mechanical/physical approach using pressure sensors and bubble generation. Instead of measuring electrical capacitance changes that are sensitive to deposits, the system uses air bubbles rising through the waste water to physically indicate the filling level, substituting an electrical field-based measurement with a mechanical fluid dynamics approach that is insensitive to tank wall deposits.
Solution Approach 2:
The patent introduces air bubbles as an intermediary medium between the measurement system and the waste water. The bubbles rise through the waste water and their behavior (formation, rise rate, detection) serves as an indirect indicator of filling level, allowing measurement without direct contact between the sensor and the deposit-prone tank walls.
2Measurement precision
If pressure sensors are used for filling level measurement, then continuous measurement is possible, but the sensors have relatively large measuring errors and are dependent on ambient temperature changes
Solution Approach 1:
The patent replaces direct pressure sensing with a bubble-based mechanical indicator system. Instead of measuring pressure changes that are affected by temperature and require calibration, the system uses the physical behavior of air bubbles (formation at specific heights, rise through the column) which provides a more stable and temperature-independent indication of filling level.
Solution Approach 2:
The patent changes the measurement parameter from pressure (which is temperature-dependent) to bubble formation height and rise characteristics. By monitoring where bubbles form and how they rise, the system obtains filling level information that is less sensitive to temperature variations, effectively changing the physical parameter being measured to one that is more stable under varying environmental conditions.
3Measurement precision
If multiple measuring positions are used with binary filling signals, then the filling level can be determined more accurately, but the system complexity increases
Solution Approach 1:
The patent divides the waste water column into multiple segments by generating bubbles at different heights or monitoring bubble behavior in different zones. Each zone provides a binary signal (bubble present/absent or rising/not rising) that corresponds to a specific filling level range, segmenting the continuous measurement problem into discrete, easily detectable zones that simplify the overall measurement system.
Solution Approach 2:
The patent uses periodic bubble generation instead of continuous sensing. Air is introduced at regular intervals to create bubbles that rise through the waste water column, and the presence or absence of bubbles at different heights during these periodic cycles provides filling level information. This periodic approach simplifies the system compared to continuous multi-sensor monitoring, as it uses time-multiplexed measurement at fewer physical locations.
Data Source
AI summary
In a method for determining a filling level (F) of waste water (8) in a tank (6) of a vehicle (2), wherein a respective flushing quantity (P) of waste water (8) is fed to the tank (6) by means of flushing processes, a binary filling signal (La-e) (waste water (8) present or not) is determined at at least two measuring positions (20a-e) at the tank (6) with known filling quantities (Ma-e), the filling level (F) is determined as a sum of a basic filling quantity (B) and an inflow quantity (Z), wherein the basic filling quantity (B) is selected as zero or as the greatest filling quantities (Ma-e) of active filling signals (La-e) at a starting time (A), and the inflow quantity (Z) is determined as a sum of all the fed-in flushing quantities (P) from the starting time (A).A measuring arrangement (12) for determining the filling level (F) contains an evaluation module (14) with an interface (16) for the flushing signals (S), and at least two sensors (18a-e) for the filling signals (La-e), wherein the evaluation module (14) is designed to determine the filling level (F) according to the method according to the invention.A waste water arrangement (4) with the tank (6) and at least one flushing device (10) contains a measuring arrangement (12) according to the invention.