Interesting. Is the movement of the glare image linked to the pod though? Seems like the pod rotation is more continuous.Let me know what you think of this 3D version of the Gimbal video.
Interesting. Is the movement of the glare image linked to the pod though? Seems like the pod rotation is more continuous.
What I think this demonstrates at the very least is how much the rotation rate of the outer lense changes as you approach 0 degrees.
The system tries to minimize turns of the outer gimbals, as they are heavy, vibration-inducing, and inaccurate. So most of the time it relies on the inner gimbaled mirrors to point the line of sight. It can't avoid some turns close to 0°, but the algorithm it uses to decide when to do this is unknown.
This is great! Do you plan to do do a side-by side with an overhead view?
Sorry if I missed something but how are you actually simulating the glare and and decoration mechanism in your video? I'm interested in how you did that.
I would be interesting to have a "pilot view" camera as well the pod view camera with glare.
Yea, it's perfectly understandable why people don't get it. It's very unintuitive. Even with graphics programming and 3D modelling/rendering experience it can make my head hurt following the various transforms.The more I describe this effect the more I understand why people aren't just "getting it"... It's a geometry problem and there's a bunch going on at once.
I'm just thinking about if we were to do a video with a breakdown using the glare effect might be seen as "cheating"
You almost need to start with showing the solving of the ATFLIR image issue (presenting a stable tracked zoomed image of a moving target filmed from a moving viewpoint to the MFD) so all the reasons for why the system is designed like that are apparent. Mick has done that in part with some of his videos, maybe a 3d recreation using F18 models etc would help.
This behavior actually became pretty clear when playing around in 3D. Here's the output of my tests. I think it shows where the pod is moving the outer gimbals and where it's using internal mirrors. Right now I have the pod automatically tracking an object set to follow the heading shown in the video. The "Simulated Lens Rotation" is the actual change in rotation of the gimbal lens in the normal direction facing the object, so that's how the glare would rotate in this model.
Great job Vizee. Very nice model.
Does the model align with the actual video in terms of amount of rotation observed?
Your model seems to predict an almost full 180° rotation in a single continuous movement but that is not what we see.
Is the yellow line in your graph below taken from the observed motion in the video? (Does it account for the aircraft varying it's bank angle slightly?) Why doesn't it align with the red line (prediction) by almost 50%?
The yellow line is the amount of rotation of the outer lens in the axis pointing at the object. If the camera was fixed to the outer lens that's how much the background/horizon would rotate over the course of the video.
We're seeing a difference because my simulation behaves as if the outer gimbal (the parts we can see moving) is used to track the object directly. In reality the actual targeting pod has a more percise internal mirror that can look up/down and left/right within the field of view of the outer gimbal's window. So what we see in that graph, especially at the end of the video, is the outer gimal moves in distinct steps to give that mirror a line of sight to the target while limiting the actual amount of time those heavy vibration inducing motors are running.
It's described in the patents that you saw in this thread:I see. What sources is this theory based off? Do we have proof that this is what actually happens on ATFLIR or is it just an educated guess?
You mean within the system there are mirrors that "point" the camera without moving the external window?
Yes, this patent describes them as "coelostat mirrors", also discusses not wanting to use the main roll axis.
Conventional airborne sensor systems generally have ability to maintain a desired pointing direction as the aircraft rolls and changes forward direction in azimuth. However, conventional systems generally cope poorly with significant changes in aircraft pitch. One approach to compensating for aircraft pitch uses the roll axis. However, as illustrated schematically in FIGS. 1A and 1B, there is typically significant hardware, including the complete afocal telescope 110, mounted on the roll axis. As a result, compensating for aircraft pitch by rotating the roll axis may require significant power to move the large associated mass, and also is not fast (or agile) and may not be particularly accurate. The problem is particularly challenging in the case of a multi-function airborne sensor, such as that discussed in U.S. PG Publication No. 2012/0292482, where alignment and pointing accuracy must be maintained for several different optical sub-systems performing different functions.
Aspects and embodiments are directed to an optical configuration for an airborne sensor that allows for agile compensation of platform pitch while also maintaining all the functionality and advantages of the multi-function airborne sensor disclosed in U.S. PG Publication No. 2012/0292482. In particular, aspects and embodiments include a dual coelostat airborne sensor configuration that enables level horizon pointing when the platform is pitched at large angles. Referring to FIGS. 2A and 2B, a gimbaled optical portion 310 a of an airborne sensor system according to one embodiment includes afocal foreoptics 110 optically coupled to a fold minor 210, a first coelostat mirror 220, and a second coelostat mirror 230. The first coelostat minor 220 corresponds to the coelostat minor 120 discussed above as used in a similar system. The afocal foreoptics 110, fold mirror 210, and first and second coelostat minors 220, 230 are mounted on a roll gimbal that rotates about an outermost roll axis 242 (first gimbal axis) that is generally parallel to the beam of electromagnetic radiation output by the afocal foreoptics 110. The first coelostat minor 220 rotates around a first rotation axis 244 (second gimbal axis) that is parallel to the beam of radiation 250 a reflected by the first coelostat minor 220, and perpendicular to the roll axis 242, as discussed above. The second coelostat mirror 230 rotates around a second rotation axis 248 (third gimbal axis) that is parallel to the beam of radiation 250 b reflected by the second coelostat mirror 220 and substantially perpendicular to the first rotation axis 244. This rotation of the second coelostat mirror 230 is used to compensate for pitching motion of the platform, thereby allowing the line of sight of the system to be maintained in a desired direction (determined by rotation of the first coelostat mirror 220 to a desired angle) even as the platform pitches over a relatively large angular range, as discussed further below. Rotation of the first coelostat minor 220 about a fourth gimbal axis 246 is used to compensate for a gimbal singularity, as also discussed above and further below.
This, basically, because the patent are both not easy to read, and often have various possible embodiments.