Speed Detecting Device Using Lorentz Force Frequency Extraction
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Solution Overview
Problem
Existing speed detecting devices for moving vehicles face challenges in accurately measuring speed due to noise components produced by vehicle vibrations, which are not effectively mitigated by existing methods.
Innovation Solution
A speed detecting device comprising a magnetic flux producing unit, a stress detecting unit, a stress transmitting member, a frequency band extracting unit, and a speed estimating unit, which uses Lorentz forces and eddy currents to extract frequency components related to the moving or rotating speed, while filtering out noise components such as inertial forces and vibration noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic force detection method is used to detect vehicle speed, then non-contact speed detection is achieved, but noise components from vehicle vibration are not effectively reduced
Solution Approach 1:
The invention applies periodic vibration to the detection probe at a specific frequency range (100-1000 Hz). This intentional vibration creates a modulation effect on the electromagnetic force signal, allowing the useful speed-related components to be distinguished from random vibration noise through frequency analysis. The key is that the probe's controlled vibration occurs at a frequency different from the vehicle's natural vibration frequencies.
Solution Approach 2:
The detection probe is made to vibrate periodically at a predetermined frequency by applying alternating voltage to a piezoelectric element or using an electromagnetic actuator. This periodic action modulates the electromagnetic force signal, creating a characteristic frequency signature that can be extracted using band-pass filtering or Fourier analysis, thereby separating it from aperiodic noise components.
Solution Approach 3:
The invention replaces direct mechanical contact-based speed detection with a non-contact electromagnetic force detection method. Instead of using mechanical sensors that physically touch the moving object, the system uses electromagnetic fields to detect speed, thereby eliminating mechanical wear and reducing the impact of mechanical vibration noise.
2Measurement precision
If electromagnetic force detection is used, then traveling speed can be detected, but the detected forces contain noise components that reduce detection accuracy
Solution Approach 1:
The system continuously monitors the electromagnetic force signal and uses feedback control to adjust the probe's vibration frequency and amplitude. By analyzing the detected signal in real-time and adjusting the excitation parameters, the system optimizes the signal-to-noise ratio and maintains accurate speed detection even under varying vibration conditions.
Solution Approach 2:
The invention changes the operating parameters of the detection system, specifically the vibration frequency of the probe and the frequency range of the band-pass filter. By tuning these parameters to avoid the dominant frequencies of vehicle vibration, the system maximizes the signal-to-noise ratio for speed detection.
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 solution enables accurate detection of moving or rotating speed by isolating the frequency components related to the Lorentz force, thereby improving the precision of speed measurement and reducing the impact of disturbance noise.
Implementation Method 1
a magnetic flux producing unit spaced apart from a principal surface of a relative moving body and configured to change, at a predetermined frequency, magnetic flux passing over the principal surface of the relative moving body
Implementation Method 2
the eddy currents occurring on the relative moving body in accordance with a moving or rotating speed of the relative moving body
Implementation Method 3
a stress transmitting member for transmitting to the stress detecting unit a Lorentz force produced in the magnetic flux producing unit in accordance with magnetic flux produced by eddy currents
Data Source
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AI summary
A speed detecting device (1) includes: a magnetic flux producing unit (2) configured to change, at a predetermined frequency, magnetic flux passing over the principal surface of the relative moving body; a stress detecting unit (3) for detecting a stress and outputting an electric signal corresponding to the stress; a stress transmitting member (4) for transmitting to the stress detecting unit (3) a Lorentz force produced in the magnetic flux producing unit (2) in accordance with magnetic flux produced by eddy currents occurring on the relative moving body (7) in accordance with a moving or rotating speed of the relative moving body (7); a frequency band extracting unit (5) for extracting a frequency component related to the Lorentz force from the electric signal; and a speed estimating unit (6) for estimating the moving or rotating speed of the relative moving body (7) based on the extracted frequency component. The changing magnetic flux can be generated by a coil driven with an AC signal, or by a permanent magnet combined with a voice coil, and driven such that the gap between the magnet and the moving body changes at the predetermined frequency. It is also possible to use a differential arrangement of two stress detecting units, one being responsive to both Lorentz forces and external disturbances, the other only to the external disturbances. In this case, also a unit producing a constant magnetic flux may be employed.