Hi All, apart from getting the Mega to work correctly with any IMU, from the playing around with cheap IMU's l wish for better accuracy on tilt compensated Yaw for a yacht auto pilot. The BNO055 does not work as hoped, from testing and forums, l see that they aren't correcting properly for velocity, great reading stationary tilted yaw, but when moving the IMU drifts really badly, or can't correct properly to a 90 degree turn. I imagine Jim (hi Jim, it's Kevin from the post in Pololu forum) will say the BNO055 works extremely well, but Jack Edwards (inventor of this AP) also agrees that it doesn't work as hoped. His fails the 90 degree test, mine when l could get it to stay going, would just hold the same bearing when the boat was turning and l have read posts on the Adafruit forum where this issue has been raised by others with Adafruit failing to respond. The only cheaper IMU l have found that gives any dynamic accuracy in spec isn't in the cheap range UM7 from CH Robotec (US$150) this is dynamic Yaw +-8 degrees. Hence l am asking if anyone knows of a better unit, may need to go to military spec and at what $. I have looked on the net, but they won't give price without talking to them. I can buy a Airmar H2183 (dynamic +- 2 degrees) for AU$1200 but would like to pay less for something better?what are my chances. Regards Kevin
Spend some more time looking on the net. I did some research a couple of years ago, and if I recall correctly, you can get a commercial IMU with better than 0.1 degree absolute accuracy for less than $50,000. Perhaps now it would be $10,000.
Multiply the price by roughly a factor of ten for each factor of 10 improvement in absolute accuracy.
I believe there's some South African manufacturers making some good units. The benefit of sourcing it from them is they aren't subject to the same export restrictions as a USA-based manufacturer. Once you get up to that military-grade level then you have to either be a military or have some fast-talking lawyers. Otherwise they won't even talk to you, let alone sell you the equipment.
Hi Jim and MorganS, thanks for the info, maybe $10,000 is just outside my budget by $9,600. I thought the Military accuracy stuff, would be limited too who can get hold of them. I have know purchased a dynamic yaw+-1 degree, heading compass from a AP manufacturer. They have got there using standard IMU bits but spent 2 years getting the algorithms to work. Also the designer of the compass has said that off the shelve IMU's Mag's won't work correctly in the Southern Hemisphere, as they had to spend a lot of time incorporating algorithms to enable boats to travel in both Hemispheres, this has been a question l have raised numerous times but no one thought it would be an issue, looks like it is. There Mag compass they have designed also won't work as well as it could, down were l live in Tasmania due to they low mag field, but they have the ability to put a GPS input for North, that then becomes the North Heading above 2 knots. Of course this is not a miniature IMU, but the size of a heading compass and not suitable for robotic's. Thanks for your response Regards Kevin. PS - How about some suggestion re my other post IMU locking up the Mega. Is there any likely hood that the library of the IMU's aren't suitable for the Southern Hemisphere and some how are locking up the Mega