Falling Edge Discrimination for Aerosol LIDAR Obstacle Detection
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Solution Overview
Problem
Current technologies face challenges in effectively detecting obstacles within aerosol clouds during helicopter operations, particularly in brownout and whiteout conditions, due to the difficulty in discriminating between aerosol and object returns using existing LIDAR and radar systems.
Innovation Solution
A remote sensing system utilizing pulsed signals and a signal processor to correlate and compare the falling edge of return signals with thresholds, distinguishing between aerosol cloud and object reflections, thereby discarding aerosol-related range data and providing accurate range information for objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LIDAR uses shorter wavelengths to achieve high sensitivity and resolution, then measurement precision is improved, but the system becomes highly sensitive to aerosols causing false detections
Solution Approach 1:
The patent applies dynamics by making the receiver's field of view (FOV) adjustable and variable during operation. The FOV is dynamically changed from a first value when detecting objects to a second value when detecting aerosols. This dynamic adjustment allows the system to optimize between spatial resolution and aerosol sensitivity based on operational needs, resolving the contradiction between high resolution and aerosol susceptibility.
Solution Approach 2:
The patent changes the operational parameters of the LIDAR system by varying the receiver FOV. When the FOV is set to the first value, the system achieves high spatial resolution for object detection. When changed to the second value, the system becomes more sensitive to aerosols for characterization. This parameter change enables the system to address both requirements at different times.
2Length of stationary object
If LIDAR transmits high power pulses to penetrate aerosol clouds, then range detection capability is improved, but false alarms from aerosol returns increase
Solution Approach 1:
The patent uses dynamic FOV adjustment to manage the trade-off between detection range and false alarm rate. When high power pulses are transmitted for long-range detection, the FOV is set to the first value to maintain spatial resolution and reduce false alarms from scattered aerosol returns. When characterizing aerosols, the FOV is changed to the second value to increase aerosol signal collection.
Solution Approach 2:
The patent replaces the mechanical approach of increasing transmit power to penetrate aerosols with an optical system approach of dynamically adjusting the receiver FOV. This substitution allows the system to maintain high power transmission for range detection while using FOV adjustment to filter out false alarms from aerosol scattering.
3Quantity of substance
If the receiver field of view is increased to detect more aerosol signal, then aerosol detection capability is improved, but spatial resolution for object detection deteriorates
Solution Approach 1:
The patent implements dynamic FOV adjustment where the receiver FOV is set to the second value (wider) when the primary goal is aerosol detection and characterization, allowing more aerosol signal to be collected. When object detection is the priority, the FOV is set to the first value (narrower) to maintain high spatial resolution. This dynamic switching resolves the contradiction between aerosol signal strength and spatial resolution.
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 approach enhances the ability to safely navigate through aerosol clouds by improving the discrimination between aerosol and object returns, reducing false alarms and enhancing the detection of obstacles, thus improving helicopter landing and hovering operations in adverse conditions.
Implementation Method 1
an object's range is calculated by measuring the time delay or time of flight (TOF) between transmission of a pulse and detection of a reflection thereof off of the object
Implementation Method 2
LIght Detection And Ranging (LIDAR), an optical remote sensing technology that measures properties of scattered collimated light to find range and/or other information of a distant object, typically using laser pulses
Implementation Method 3
measures properties of scattered collimated light
Implementation Method 4
detection of a reflection thereof off of the object
Data Source
AI summary
A LIDAR optical remote sensing system and method analyzes the falling edge profile of a return LIDAR signal that may be indicative of an object or an aerosol cloud, which is generally more diffuse. Using the falling edge profile permits burnthrough to an object that may be obscured by the aerosol cloud. The profile is compared against at least one threshold that may correspond, in various embodiments, to a negative slope of the falling edge, an integrated power under the falling edge, or a range estimate error for varying transmitted power values, varying transmitted pulse lengths and/or varying receiver detector field of view values.