Four-Axis Gimbal Coelostat Sensor Pitch Compensation
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Solution Overview
Problem
Conventional airborne sensor systems face challenges in maintaining accurate pointing and alignment over wide angular ranges, especially when the aircraft pitches, and they struggle to provide simultaneous infrared search and track, targeting, and standoff reconnaissance functions effectively due to gimbal singularities and inadequate compensation for platform pitch.
Innovation Solution
A four-axis gimbaled dual coelostat optical configuration is employed, featuring afocal foreoptics, coelostat mirrors, and a derotation device, allowing for wide-angle fields of regard in azimuth and elevation while compensating for platform pitch and preventing gimbal singularities through additional gimbal axes, enabling agile and accurate line-of-sight maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional three-axis gimbal arrangement is used, then the device complexity is reduced, but the field of regard is limited and gimbal singularities occur
Solution Approach 1:
The patent transitions from a three-axis gimbal to a four-axis gimbal arrangement by adding a fourth rotation axis to the coelostat mirror. This dimensional expansion enables the system to achieve a field of regard exceeding 165 degrees in elevation and 140 degrees in azimuth while eliminating gimbal singularities that constrain conventional three-axis systems.
2Adaptability or versatility
If the field of regard is expanded to cover wide azimuth and elevation angles, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The patent segments the gimbal system into four independent rotation axes, with each axis performing a specific function: the first axis for azimuth rotation, the second axis for elevation rotation, the third axis for pitch compensation, and the fourth axis for gimbal singularity prevention. This segmentation allows the system to achieve wide field of regard while maintaining manageable complexity through functional decomposition.
Solution Approach 2:
The coelostat mirror serves multiple functions by being mounted on four rotation axes, enabling it to perform azimuth scanning, elevation scanning, pitch compensation, and gimbal singularity avoidance simultaneously. This multi-functionality reduces the need for separate mechanical systems for each function.
3Adaptability or versatility
If the aircraft pitches during operation, then the platform adaptability is improved, but the pointing accuracy deteriorates due to inadequate pitch compensation
Solution Approach 1:
The patent implements pitch compensation through a feedback mechanism where the third rotation axis of the coelostat mirror actively counteracts platform pitch movements. The system continuously adjusts the mirror orientation along the third axis to maintain accurate line-of-sight pointing despite aircraft pitch changes, ensuring pointing accuracy is preserved during dynamic platform operation.
4Measurement precision
If a four-axis gimbal arrangement is used, then the pointing accuracy is improved and pitch compensation is achieved, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into the four-axis gimbal system, combining azimuth scanning, elevation scanning, pitch compensation, and gimbal singularity avoidance into a single integrated mechanism. By consolidating these functions into one coordinated system rather than separate mechanisms, the patent achieves high pointing accuracy while managing overall device complexity through functional integration.
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 solution provides a multi-function airborne sensor system capable of maintaining accurate pointing and alignment over large angular ranges, including wide fields of regard in elevation and azimuth, and effectively compensates for platform pitch, enhancing the system's agility and accuracy in IRST, targeting, and standoff reconnaissance functions.
Implementation Method 1
an afocal foreoptics configured to receive electromagnetic radiation and to direct a collimated beam of the electromagnetic radiation
Implementation Method 2
a first coelostat mirror configured to rotate about a second axis substantially perpendicular to the first axis and to receive and reflect the electromagnetic radiation
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An optical sensor assembly in which a four axis gimbal and dual coelostat mirror configuration provide pointing of the sensor line of sight in azimuth and elevation, stabilized for platform pitch. One example of a sensor system includes a first optical sub- system including a first plurality of optical elements, and a second optical sub-system configured to rotate about a first axis relative to the first optical sub-system. The second optical sub-system includes afocal foreoptics configured to direct a collimated beam of electromagnetic radiation to the first optical sub-system, a first coelostat mirror configured to rotate about a second axis substantially perpendicular to the first axis, and a second coelostat mirror configured to rotate about a third axis substantially perpendicular to both the first axis and the second axis, and to receive electromagnetic radiation reflected by the first coelostat mirror and to direct the electromagnetic radiation to the afocal foreoptics.