Vehicle Speed Measurement Using Dual Accelerometers
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Solution Overview
Problem
Conventional vehicle speed measurement methods are inaccurate due to reliance on wheel rotational speed and do not provide absolute values, requiring calibration and adaptation for each vehicle, and are difficult to mount, especially in safety-critical areas.
Innovation Solution
A measuring device with two acceleration sensors arranged perpendicularly to the wheel axis, which determine the acceleration in the direction of travel and angular acceleration, allowing for precise calculation of vehicle speed and wheel diameter without parameterization, and can be easily retrofitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional wheel rotational speed measurement methods are used, then the measurement can be implemented with existing systems, but the measurement precision is insufficient due to reliance on fixed wheel diameter values and disregard of wheel slip
Solution Approach 1:
The patent replaces the conventional mechanical speedometer drive system with an inertial measurement system using accelerometers. Instead of mechanically converting wheel rotational speed to vehicle speed, the invention uses sensors to directly measure acceleration in three orthogonal directions, which are then integrated to obtain velocity and position. This substitution eliminates the need for mechanical linkages and the assumptions about wheel diameter and slip, thereby improving measurement precision.
Solution Approach 2:
The patent introduces accelerometers as intermediary devices that indirectly measure vehicle speed through acceleration detection. Rather than directly measuring wheel rotation or vehicle speed, the system uses acceleration sensors as intermediaries to capture motion dynamics, which are then processed through integration and filtering to derive accurate speed and position information while compensating for wheel slip and varying wheel diameters.
2Measurement precision
If acceleration sensors are mounted on the wheel to measure vehicle speed, then absolute speed values can be obtained, but the device becomes difficult to mount as concealed parts of the vehicle must be accessed
Solution Approach 1:
The patent designs a mounting structure that serves multiple functions: it provides a secure attachment point for the accelerometer, incorporates a magnet for wheel speed synchronization, and includes a housing that protects the electronics. This multi-functional mounting bracket eliminates the need for separate mounting components and can be installed on various vehicle types without custom fabrication, thereby improving ease of manufacture and installation.
Solution Approach 2:
The patent positions the accelerometer at the wheel center, which is the equipotential point for rotational motion. By placing the sensor at this location, the system minimizes the effects of wheel rotation on the measurement, as the center point experiences only translational acceleration without rotational components. This strategic positioning simplifies the measurement model and improves accuracy without requiring complex compensation algorithms.
3Adaptability or versatility
If conventional speed measurement methods are used, then the system can operate without additional sensors, but the device must be parameterised and calibrated for each vehicle type
Solution Approach 1:
The patent implements a self-calibration system that automatically determines vehicle-specific parameters during normal operation. The microcontroller continuously monitors acceleration data and wheel speed signals, using them to calculate and store calibration factors such as wheel diameter and gear ratios. This self-service approach eliminates the need for manual parameterization and calibration procedures for each vehicle type, allowing the system to adapt automatically and reducing calibration time to minimal initial setup.
4Productivity
If bus systems are used to transmit vehicle speed information, then existing communication infrastructure can be utilized, but no measuring devices may be connected to these for safety-related reasons
Solution Approach 1:
The patent introduces a wireless communication module as an intermediary between the inertial measurement system and external devices. Instead of directly connecting to the vehicle's safety-critical bus systems, the system transmits processed speed and position data via wireless communication (such as Bluetooth or Wi-Fi). This intermediary approach allows data sharing with mobile devices and other external systems without compromising the integrity or safety of the vehicle's internal bus networks.
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
Provides precise, absolute speed measurements independent of conventional methods, allowing for accurate determination of vehicle speed and wheel diameter, and can be used without interfering with safety systems, with self-calibration and additional features like slip detection and tire pressure monitoring.
Implementation Method 1
a first sensor (10) for measuring the acceleration acting on the first sensor (10)
Implementation Method 2
a second sensor (20) for measuring the acceleration acting on the second sensor (20), wherein the second sensor (20) measures accelerations, which each act perpendicularly to the axis of the wheel and which are disposed at an angle to one another
Data Source
AI summary
A measuring device for measuring the speed of a vehicle running on wheels has a first sensor and a second sensor. The two sensors are arranged on the same wheel of a vehicle and rotate with this wheel. Both sensors are arranged in such a way that they measure forces which are each perpendicular to the axis of the wheel and at an angle to one another, and act on the same point. An evaluation device is provided to which the measured values of the two sensors are fed, with the evaluation device obtaining the acceleration of the vehicle in the direction of travel therefrom, and calculating the current vehicle speed from it.