Vehicle Speed Measurement Using Sensor Fusion
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Solution Overview
Problem
Existing autonomous emergency braking systems in vehicles face inaccuracies in determining vehicle speed during slip conditions or unfavorable weather, leading to potential premature termination of emergency braking interventions due to reliance on wheel speed sensors.
Innovation Solution
The implementation of a multi-sensor system that includes wheel speed sensors, a distance sensor, an optical sensor, a GPS sensor, and a video camera, which use sensor fusion to independently determine vehicle speed, combining signals from these sources to ensure accurate speed calculation even during autonomous braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed sensors are used to determine vehicle speed during autonomous emergency braking, then the system is simple and cost-effective, but the speed measurement becomes inaccurate during wheel slip conditions
Solution Approach 1:
The patent combines multiple speed determination methods (wheel speed sensors, GPS receiver, and optical flow measurement from video camera) into a unified system that selects or fuses data sources based on current driving conditions. This merging allows the system to maintain simple operation while achieving high measurement precision by using the most reliable sensor under each specific condition.
Solution Approach 2:
The system dynamically changes the parameters used for speed determination based on detected conditions. When wheel slip is detected or during conditions where wheel speed sensors are unreliable, the system switches to using GPS data or optical flow measurements instead, thereby maintaining accurate speed measurement without requiring all sensors to operate continuously at full complexity.
2Reliability
If multiple sensors and sensor fusion are implemented to accurately determine vehicle speed during slip conditions, then speed measurement accuracy is maintained, but the device complexity and cost increase
Solution Approach 1:
The patent implements a dynamic sensor fusion system that adaptively selects and weights data from different sensors based on current operating conditions. Rather than continuously processing all sensor inputs equally, the system dynamically adjusts which sensors are active and how their data is weighted, maintaining high reliability while reducing computational complexity during normal operating conditions.
Solution Approach 2:
The control unit acts as an intermediary that processes and fuses data from multiple sensors (wheel speed sensors, GPS receiver, video camera). This intermediary component coordinates the complex interactions between sensors, managing the data flow and fusion algorithms to achieve reliable speed determination without requiring each sensor to independently handle the full complexity.
3Force
If autonomous emergency braking is initiated with maximum force to reduce kinetic energy, then accident consequences are mitigated, but wheel slip occurs leading to inaccurate speed determination
Solution Approach 1:
The system performs preliminary actions by continuously monitoring wheel slip conditions and preparing alternative speed measurement methods before they are needed. During normal braking, the system uses wheel speed sensors, but has pre-configured GPS and optical flow measurement as ready alternatives that can be immediately activated when wheel slip is detected, ensuring continuous accurate speed determination throughout the braking process.
Solution Approach 2:
The system implements feedback by continuously monitoring wheel speed and comparing it with expected vehicle deceleration patterns. When wheel slip is detected through this feedback mechanism, the system automatically switches to alternative speed determination methods, creating a closed-loop control system that maintains measurement accuracy despite the harsh braking conditions that cause wheel slip.
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 allows for reliable and precise determination of vehicle speed, enhancing the accuracy of risk assessment and timely intervention in emergency braking scenarios, even under adverse conditions.
Implementation Method 1
own vehicle speed determined on the basis of speed signals from a GPS receiver
Implementation Method 2
distance data being recorded by the radar sensor
Implementation Method 3
speed signals from wheel speed sensors
Data Source
Figure 1
AI summary
A method for autonomous emergency braking in a road vehicle to avoid or reduce the severity of an accident includes measuring the speed of the vehicle during autonomous emergency braking and additionally determining vehicle speed independent of the wheel rotational speeds of the vehicle. In this way, the vehicle speed can be determined sufficiently accurately even in the cases in which, as a result of sharp autonomous braking, the vehicle speed is higher than the wheel rotational speeds.