Diode Noise Filter for Helicopter Speed Sensor
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Solution Overview
Problem
Mechanically-induced electrical noise from high power gear trains in helicopters' speed sensors leads to erroneous signal readings, particularly during target nulls, affecting the accuracy of rotational speed and direction measurements.
Innovation Solution
A system comprising diode pairs and a processor connected in parallel with a resistor, which filters mechanically-induced signal noise from an inductive speed sensor by receiving and processing signals from a rotating shaft with radially oriented target groups, allowing for accurate determination of rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic pickup speed sensor is used to measure rotational speed, then speed measurement capability is provided, but mechanically-induced electrical noise causes erroneous signal readings during target nulls
Solution Approach 1:
A diode noise filter circuit is introduced as an intermediary component between the magnetic pickup speed sensor and the signal processing system. The filter circuit selectively attenuates high-frequency noise signals while allowing the useful low-frequency speed measurement signals to pass through, thereby resolving the contradiction between maintaining measurement capability and eliminating mechanically-induced electrical noise
Solution Approach 2:
The diode noise filter operates by changing the electrical parameters (impedance, conductivity) in response to signal amplitude. During target nulls when noise dominates, the filter's electrical characteristics change to suppress high-frequency noise, while during valid signal conditions, the filter maintains signal integrity, thus improving measurement precision without losing the speed measurement function
2Power
If the high power gear train drives the propeller, then rotational power is transmitted, but high frequency vibration is generated that corrupts sensor signals
Solution Approach 1:
The diode noise filter converts the harmful high-frequency vibration signals into beneficial information by using the vibration characteristics to control filter switching. The filter detects the presence of vibration-induced noise and automatically adjusts its filtering characteristics, transforming the harmful vibration into a control signal that enhances overall system performance
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
The system effectively reduces signal noise, resulting in more accurate rotational speed measurements by filtering out vibrations-induced errors, enhancing the reliability of speed sensor data in helicopter applications.
Implementation Method 1
A magnetic pick up speed sensor may be used to measure the speed of a rotating shaft in speed sensing electronics by measuring a change of magnetic flux inside of a sensor as magnetic targets on the rotating shaft pass the sensor position
Implementation Method 2
The high frequency vibration can result in an erroneous electrical signal at the frequency of the gear train during target nulls that are required to measure rotational direction
Data Source
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AI summary
A system for filtering mechanically-induced signal noise from a speed sensor (102) may include a rotating member (110) having at least one target group (202) radially oriented about a center of the rotating member, an inductive speed sensor (102) configured to sense the at least one target group, and two diode pairs (104, 106) each having a first diode (104a, 106a) and a second diode (104b, 106b). The two diode pairs may be operatively connected to the inductive speed sensor and configured to receive a signal having the mechanically-induced signal noise. The system may also include a resistor (108) connecting the diode pairs, a processor (118) connected in parallel with the resistor and configured to receive a signal from the inductive speed sensor. The processor may be configured to receive a signal having reduced signal noise via the diode pairs, and determine a rotational speed of the rotating member based on the signal having reduced signal noise.