Ultrasonic Sensor Air Temperature Determination via Reflection Ellipses
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Solution Overview
Problem
Ultrasonic sensor systems in vehicles face challenges in accurately determining air temperature, which affects distance measurements, due to the influence of air pressure, humidity, and temperature on sound speed, leading to incorrect distance calculations, especially in autonomous driving where precision and reliability are critical.
Innovation Solution
A method using at least three ultrasonic sensors to calculate the speed of sound based on an initial temperature value, emitting and receiving ultrasonic signals to determine transit times, and adjusting reflection ellipses' size parameters to find a common intersection or tangential plane, thereby identifying the correct air temperature for precise distance determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If air temperature is determined using conventional methods, then the determination process is simple, but the temperature determination accuracy is insufficient leading to incorrect distance measurements
Solution Approach 1:
The patent implements an iterative feedback mechanism where the ultrasonic sensor system continuously measures transit times, calculates reflection ellipses, checks for common intersection points, and adjusts the temperature value accordingly. The system feeds the determined temperature back into the speed of sound calculation to improve distance measurement accuracy, creating a closed-loop system that self-corrects temperature determination errors.
Solution Approach 2:
The patent transitions from one-dimensional temperature measurement (single sensor or simple thermocouple) to a multi-dimensional approach using at least three ultrasonic sensors arranged in space. By creating reflection ellipses in three-dimensional space and finding their common intersection point, the system adds spatial dimensions to the temperature determination process, significantly improving accuracy through geometric triangulation.
2Measurement precision
If ultrasonic sensors are used for distance measurement, then distance can be measured, but incorrect air temperature leads to incorrect speed of sound calculation and inaccurate distance measurements
Solution Approach 1:
The patent dynamically changes the speed of sound parameter based on the determined air temperature. Instead of using a fixed or estimated speed of sound, the system calculates the actual speed of sound using the formula c = 331.5 + 0.606 * T, where T is the determined temperature in degrees Celsius. This parameter adaptation ensures accurate distance measurements across varying temperature conditions.
Solution Approach 2:
The patent performs preliminary temperature determination using the ultrasonic sensor system before conducting distance measurements. By first establishing the accurate air temperature and corresponding speed of sound through the reflection ellipse method, the system prepares the correct acoustic parameters in advance, ensuring that subsequent distance measurements are performed with accurate speed of sound values.
3Measurement precision
If at least three ultrasonic sensors are used to determine air temperature through reflection ellipses, then temperature determination accuracy improves, but the calculation complexity and processing time increase
Solution Approach 1:
The patent implements a dynamic iterative process where the system starts with an initial temperature estimate, calculates reflection ellipses, checks for common intersection points, and adjusts the temperature value in successive iterations. The process dynamically converges to the accurate temperature value, balancing computational effort with measurement precision by stopping when the common intersection point is found or a maximum iteration limit is reached.
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 allows for precise air temperature determination and accurate distance measurement by ensuring the correct speed of sound is calculated, improving the reliability of ultrasonic sensor systems in vehicles, especially in autonomous driving applications.
Implementation Method 1
calculating a speed of sound for ultrasonic signals based on the initial temperature value
Implementation Method 2
receiving sensor data from the ultrasonic sensors of an ultrasonic signal emitted by one of the at least three ultrasonic sensors and reflected by at least one object
Implementation Method 3
receiving sensor data from the ultrasonic sensors of an ultrasonic signal emitted by one of the at least three ultrasonic sensors and reflected by at least one object
Data Source
AI summary
A method for determining an air temperature for an ultrasonic sensor system, in particular for a vehicle, is disclosed. The method includes determining the intersection points and/or tangential lines and/or tangential planes between the reflection ellipses. If there is a common intersection point and/or a common tangential line and/or a common tangential plane between all reflection ellipses, then identifying the output temperature value as the current air temperature. If there is no common intersection point and/or no common tangential line and/or no common tangential plane between all reflection ellipses, then (i) varying size parameters of the reflection ellipses until a common intersection point and/or a common tangential line and/or a common tangential plane exists between all reflection ellipses, and (ii) calculating a temperature value for the reflection ellipses with a common intersection point and/or a common tangential straight line and/or a common tangential plane and identifying the temperature value as the current air temperature.