Inductive Load Testing via Modulated Signal for Coil Defect Detection
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Solution Overview
Problem
Conventional continuity testing of motor coils in guided bombs cannot detect shorted or high inductance defects, leading to potential misidentification of coil conditions and improper bomb trajectory control.
Innovation Solution
A modulated signal test technique is applied to inductive loads, allowing for the identification of deviations in inductance values, thereby detecting shorted, normal, or abnormally high inductive states, which conventional tests may miss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional continuity test using DC voltage is applied to motor coils, then the test circuit can detect proper continuity and prevent launching with open circuits, but the test cannot detect shorted coils or high inductance defects because current flows through both proper and defective coils
Solution Approach 1:
The patent changes the test signal from DC voltage to a modulated AC signal (e.g., sinusoidal or square wave at specific frequencies). This parameter change allows the test to detect inductance deviations because the modulated signal's response characteristics (amplitude, phase) vary differently for shorted versus normal coils, enabling discrimination between proper and defective coils that DC testing cannot distinguish
2Device complexity
If a DC voltage source is used for continuity testing, then the testing circuit is simple and can identify open circuits, but it fails to identify shorted coils or high inductance defects resulting in potential improper bomb trajectory control
Solution Approach 1:
The patent employs periodic modulated signals (AC waves at specific frequencies) instead of continuous DC voltage. The periodic nature of the signal allows measurement of inductive reactance and phase relationships, which provide additional information about coil integrity. By analyzing the amplitude and phase of the current response to the periodic signal, the system can detect shorted coils and high inductance defects while maintaining reasonable circuit complexity through frequency-selective testing
3Ease of operation
If conventional continuity testing is performed, then bombs with open circuits are prevented from launching, but bombs with shorted or high inductance coils may launch with defective motors leading to trajectory control failures
Solution Approach 1:
The patent implements a feedback mechanism where the test circuit measures the current response to the modulated signal and compares it against expected characteristics. By analyzing the amplitude ratio and phase difference between the applied signal and the resulting current, the system receives feedback about the coil's actual electrical properties. This feedback loop enables the system to identify not just the presence but the type of defect (shorted, high inductance, or normal), providing comprehensive launch safety verification
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 method effectively identifies defective or improperly installed coils, ensuring accurate electromagnetic field generation and correct bomb trajectory control, preventing unintended damage and enabling cost savings through defect detection.
Implementation Method 1
testing an inductive load of a device using a modulated signal... capable of identifying deviations in the inductive load from a nominal value
Data Source
AI summary
A device has built-in inductive load testing capabilities. The device includes a device housing, an inductive load disposed within the device housing; and test circuitry disposed within the device housing. The test circuitry is constructed and arranged to effectuate application of a modulated test signal to the inductive load, and obtain a result signal in response to the application of the modulated test signal to the inductive load. The test circuitry is further constructed and arranged to generate an output signal indicating that the inductive load is in one of (i) a shorted inductive load state, (ii) a normal inductive load state, and (iii) an abnormally high inductive load state, based on the result signal. Such test circuitry is well-suited for testing a variety of devices having inductors/coils which are susceptible to defects (e.g., a solenoid, a motor winding, various actuator components, etc.).