Ultrasonic Sensor Humidity Determination via Frequency Attenuation
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Solution Overview
Problem
Existing ultrasonic sensor systems for vehicles face challenges in determining relative humidity, particularly in vehicles without dedicated humidity sensors, which affects the accuracy of distance measurements and DPF regeneration control.
Innovation Solution
A method involving selecting an appropriate ultrasonic sensor, transmitting signals at different frequencies, determining attenuation values, and converting differences into relative humidity indications, while adjusting distance thresholds for DPF regeneration based on thermal conductivity calculated from humidity and temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If ultrasonic sensors are used for distance determination without dedicated humidity sensors, then device complexity is reduced, but measurement precision of relative humidity deteriorates
Solution Approach 1:
The ultrasonic sensor is designed to perform multiple functions: both distance determination and relative humidity measurement. By transmitting ultrasonic waves at multiple frequencies and analyzing attenuation characteristics, the single sensor system can derive humidity information without requiring a separate dedicated humidity sensor, thus reducing overall device complexity while maintaining measurement capability
Solution Approach 2:
The system changes the frequency parameter of the ultrasonic waves transmitted by the sensor. By transmitting at different frequencies (e.g., 40 kHz and 80 kHz) and measuring the differential attenuation, the system can calculate relative humidity. This parameter variation approach enables humidity measurement using the existing ultrasonic sensor infrastructure without adding dedicated humidity sensing hardware
2Ease of operation
If fixed distance thresholds are used for DPF regeneration control, then control simplicity is maintained, but reliability of regeneration control deteriorates due to environmental variations
Solution Approach 1:
The distance threshold for DPF regeneration control is made dynamic rather than fixed. The system adjusts the threshold based on real-time measurements of relative humidity and air temperature, which affect thermal conductivity. This dynamic adjustment ensures reliable regeneration control across varying environmental conditions while maintaining relatively simple control logic through automated parameter adaptation
3Reliability
If distance thresholds are adjusted based on thermal conductivity calculations from humidity and temperature, then reliability of DPF regeneration control improves, but device complexity increases
Solution Approach 1:
The system introduces thermal conductivity as an intermediary parameter that links the measured environmental conditions (humidity and temperature) to the DPF regeneration control decision. By calculating thermal conductivity from these measurements and using it to adjust the distance threshold, the system achieves reliable control without directly complexifying the control logic, as the intermediary parameter handles the environmental variations
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 improves the accuracy of relative humidity measurements and enhances the frequency of successful DPF regeneration events by optimizing sensor selection and distance threshold adjustments.
Implementation Method 1
an oscillated voltage may be applied to the piezo disc such that the piezo disc and membrane vibrate and generate ultrasonic waves
Implementation Method 2
The piezo disc attached to the membrane converts the vibration to voltage
Implementation Method 3
based on the timeframe of sending and receiving the ultrasonic wave, a distance determination to an object may be inferred
Implementation Method 4
transmitting two different frequencies, and estimate humidity based on a difference between attenuation losses obtained from the two different frequencies
Data Source
AI summary
Methods and systems are provided for conducting measurements of relative humidity via the use of an ultrasonic sensor. In one example, the ultrasonic sensor for conducting the relative humidity measurement is selected from a plurality of ultrasonic sensors positioned at various locations on the vehicle, and where the selecting is accomplished in some examples via the use of one or more onboard cameras configured to identify suitable objects that are stationary with respect to the vehicle. In this way, robustness and accuracy of relative humidity measurements may be improved, lifetime of individual ultrasonic sensors may be extended, and vehicle operating conditions that depend on accurate relative humidity measurements may be improved.