Speed Sensor Costas Loop Noise Resistance
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Solution Overview
Problem
Existing speed sensors face limitations in precision and noise sensitivity, particularly with square-wave signals, leading to errors and bandwidth limitations in frequency and angle measurements, which are disruptive in control processes, especially in applications like automobiles.
Innovation Solution
A speed sensor utilizing a Costas loop unit with a sigma-delta modulator and a numerically controlled oscillator (NCO) for digital signal processing, providing improved noise resistance and precision by generating frequency and phase output signals, and allowing for adaptive output signal properties and compensation for encoder errors and temperature influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If square-wave signals are used for speed measurement, then the signal is easy to generate and process, but noise sensitivity increases and measurement precision deteriorates
Solution Approach 1:
The patent introduces a sinusoidal reference signal as an intermediary between the square-wave sensor signal and the frequency measurement process. This reference signal serves as a mediator that enables precise frequency and phase measurement through correlation techniques, resolving the contradiction by maintaining the simple square-wave generation while adding a mediating sinusoidal component for accurate measurement
Solution Approach 2:
The patent transforms the measurement approach by changing from direct square-wave frequency counting to correlation-based measurement using sinusoidal parameters. By converting the measurement methodology from time-domain counting to frequency-domain correlation analysis, the system achieves high precision while maintaining simple signal generation
2Measurement precision
If high-resolution frequency measurement is implemented by counting many pulses, then measurement precision improves, but measurement delay increases and bandwidth decreases
Solution Approach 1:
The patent replaces the mechanical pulse-counting method with a signal processing approach using correlation techniques. Instead of mechanically counting pulses over a measurement interval, the system uses correlation of sinusoidal reference signals with the sensor output, enabling high-resolution frequency measurement without the time delay inherent in pulse counting methods
Solution Approach 2:
The patent employs periodic sinusoidal reference signals at the expected frequency to enable continuous frequency measurement. By using periodic correlation rather than continuous pulse counting, the system achieves high resolution while maintaining real-time bandwidth, as the periodic nature allows for continuous updating without accumulating measurement delay
3Measurement precision
If sinusoidal signals are used instead of square-wave signals, then noise filtering capability improves and measurement precision increases, but signal processing complexity increases
Solution Approach 1:
The patent introduces sinusoidal reference signals as intermediaries that enable noise filtering through correlation techniques. Rather than requiring complex filtering of the sensor signal itself, the sinusoidal reference acts as a mediator that selectively extracts the signal component at the expected frequency, filtering out noise while maintaining simple processing architecture
Solution Approach 2:
The patent implements a feedback mechanism where the measured frequency and phase information from the correlation process is used to adjust the sinusoidal reference signal parameters. This feedback loop enables adaptive tracking of frequency changes while maintaining noise resistance, achieving high precision measurement without requiring overly complex signal processing
Data Source
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Figure 2
Figure 3~4
AI summary
Speed sensor comprising at least one sensor element (1) and an analog-to-digital converter (2) that digitizes the output signals of the senor element/s, further comprising a Costas loop unit (3, 4, 5) that is connected to the output of the analog-to-digital converter (2).