Scratched record…

To get Zoe or Phoebe any better, I need more sensors.

  1. GPS: I’ve heard that while GPS may only have an accuracy of 10m, the resolution is a lot finer and is stable; that could be good for outdoors but useless for indoors.
  2. My various laser tracking solution should be good for indoors.  My current best idea is 2 down-facing lasers on the frame and one hand held also pointing at the floor; combined with the RaspiCam could give height and and a simple degree of line tracking.  Probably not good enough for use outside in bright sunlight however.
  3. The ultrasonic range finder could provide height indoors and out, but can’t help with horizontal drift
  4. The barometer is a chocolate teapot to me – despite high resolution, indoor air-pressure fluctuations will spoil it
  5. The compass could be useful for yaw, but only becomes worth its weight in gold alongside GPS: orientation and location

Currently, 2 sounds the most viable, useful, simple and cool – imagine taking a quadcopter for a walk indoors following the 3 laser dots on the floor trying to keep them in an equilateral triangle of fixed size.  Except…

Zoe Pi Zero doesn’t have a camera connector so that rules her out.

Phoebe’s A+ is powered solely by the LiPo to make space underneath her for the camera and URF.  That makes it much harder to run the code without also running the motors, so I need to sort that out to test the new idea safely.  Then there’s the issue that I think the laser processing will a separate CPU to process the pictures – i.e. the A3 due for delivery some time this year.

Oh, and then I’ve just found this.

It might be time to take a break?


2 thoughts on “Scratched record…

  1. You don’t need a break, you need more sensors! 🙂
    How about using the raspi camera pointing downwards and using the motion vectors for horizontal movement tracking? With info from the gyro you could extrapolate if the motion vectors show angular or linear movement. Add a sonar (or lidar) for the distance and you can figure out how much the quad actually moved.

    The GPS is ok given a clear view of the sky. I’ve been playing with a Neo M8N and it’s very nice (when it’s not jammed by the camera that is). When filtered through a Kalman with data from the accelerometer I managed to improve the precision from the 3-4m to 40-50cm. But you do need a very good signal.
    Then there is rtklib that can give you centimeter precision outside but it’s pricey. Emlid has the cheapest device AFAIK at around 500 euros.

    For indoors you could also use 6 sonars (or more) pointing in all directions (up/down, left/right, front/back) and use that both for horizontal and vertical positioning. With MaxSonar you get around 6-10m range and they can be triggered simultaneously at 10hz. You could even rotate them to get mode data in.

    There is the kinect or similar 3D sensors that you could use to build a 3D representation of the surroundings. The RPI3 might have enough cpu for this task.

    In any case, I also considered taking a brake and doing smth else – like cars – but they are a bit boring… After trying to balance a flying machine with 4 rotating knives powered by a bomb essentially, anything else looks a bit too easy.


    • I’ve often talked about taking a break – it normally lasts less than a week as something new comes along or I get really bored! I’m already thinking in more detail about the 3 lasers idea. I’ve got enough spares – think about taking a quadcopter for a walk around the house like a dog on a leash but in this case it’s a laser pointer shining at the ground. But I really have to concentrate on the kids educational tutorial kits in time for the Cotswold Jam at the end of April. But walking a quadcopter on a laser leash sounds so much cooler, doesn’t it?

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