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Yeah, I think the biggest factor preventing such a simple design from working well on Mars would be the (current) lack of anything equivalent to GPS. In order

Yeah, I think the biggest factor preventing such a simple design from working well on Mars would be the (current) lack of anything equivalent to GPS. In order to navigate safely, especially during takeoff and landing, you need a reasonable idea of your absolute velocity relative to the ground. You can't get that from an IMU (except over very short timescales) because of integration errors. A barometer would work for the vertical axis, but getting the horizontal component is a lot trickier. GPS solves this nicely, especially since velocity can be derived from relative measurements, which are much more accurate than absolute ones. It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide.

NovemberWhiskey 6y ago
>It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide. I believe that for Ingenuity they are actually doing this in software; but at this point, you can just buy off-the-shelf an optical flow odometry ASIC with a built-in camera and lens system that draws <5mA, fits in a 4x5mm footprint and gives you delta-X and delta-Y. e.g. https://www.pixart.com/products-detail/108/PAA3905E1-Q https://www.pixart.com/products-detail/108/PAA3905E1-Q Kinda mind-blowing.
- hoseja 6y ago
  Is that kind of like optical mouse sensor?
  - NovemberWhiskey 6y ago
    Yes it is! Obviously it's a slightly harder problem if you don't know the distance from the surface and you can't provide your own illumination.
walrus01 6y ago
At the relatively low heights ingenuity is flying at, a single point LIDAR rangefinder aimed straight down would also be well suited to maintaining a certain altitude.
XorNot 6y ago
That's one of those missions I'm actually really hoping I live to see: a whole sequence of launches putting a GPS constellation into orbit around Mars.

NovemberWhiskey 6y ago

>It looks like Ingenuity uses visual odometry from a downward-facing camera, which is likely to require a lot more processing than something like an STM32 could provide. I believe that for Ingenuity they are actually doing this in software; but at this point, you can just buy off-the-shelf an optical flow odometry ASIC with a built-in camera and lens system that draws <5mA, fits in a 4x5mm footprint and gives you delta-X and delta-Y. e.g. https://www.pixart.com/products-detail/108/PAA3905E1-Q https://www.pixart.com/products-detail/108/PAA3905E1-Q Kinda mind-blowing.

hoseja 6y ago
Is that kind of like optical mouse sensor?
- NovemberWhiskey 6y ago
  Yes it is! Obviously it's a slightly harder problem if you don't know the distance from the surface and you can't provide your own illumination.

walrus01 6y ago

At the relatively low heights ingenuity is flying at, a single point LIDAR rangefinder aimed straight down would also be well suited to maintaining a certain altitude.

XorNot 6y ago

That's one of those missions I'm actually really hoping I live to see: a whole sequence of launches putting a GPS constellation into orbit around Mars.