The Vectornav VN-100 IMU (they call it an Attitude Heading Reference System, for some reason) is out and it looks like the best device on the market in this price range. Here's the description from the site.
The VN-100 combines a 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, and a high performance processor onto a single surface mountable chip-sized module to create a high performance orientation sensor. Fully calibrated for bias, gain, and misalignment, the VN-100 accurately calculates orientation over the entire 360° range at 200 Hz. Filtered orientation data and inertial measurements are assessible via either a SPI or RS-232 serial interface.
With its small size, high performance, and low cost, the VN-100 has numerous potential applications. A development kit is available for the VN-100 which comes with a sensor pre-installed and gives easy access to all of the sensor's features.
Features and Benefits:
Complete Sensor Package
3-axis accelerometer
3-axis gyro
3-axis magnetometer
Multiple Output Types
Heading , Pitch, Roll
Quaternion / DCM
Acceleration, Angular Rates, Magnetic
High Precision
Heading accuracy < 1.0 (static)
Pitch/Roll accuracy < 0.5 (static)
< 3 deg dynamic
Fast Onboard Processor
Extended Kalman Filter
200 Hz update rate
Surface Mount Package
Hand solderable
30 pads
Ultra-Compact Size
22 x 24 x 3 mm
3 grams
Fully Calibrated
Scale Factor and Gain
Axis misalignment < 0.05 deg
Hard / Soft Iron Compensation
Digital Interface
Serial UART up to 921600 bps
SPI Interface up to 18 MHz
Low Cost
$400 - 500
*Price depends on quantity
I basically just went through the Quick Start Guide and started recording video. I would like to put one on a Scorsby Table for a while in the near future and see how it does. My hands are a little too shaky to get very good data ;)
jack, i am sure if you find a correct placement in the plane, your (mechanical) compass will have very very small error. I can see a lot of quadrotors with compass.
This tri rotor puts an exceptional amount of current through the wires & is way beyond what a commercial AHRS has to endure, but it shows how much a magnetometer can be affected by a hobby vehicle.
Hi Xander, i have placed my magnetometer about 15mm from 2200mAh 11.1v battery and about 180mm from motor.
i can see some interference, but it is very small and obviously it could be placed further than electrical systems.
i am using closed loop control using AHRS data (using 3 axis magnetometer) and all correct!
From what I've read, magnetometers on small UAVs can run into some pretty substantial interference from the electric motors. And unfortunately it's not just static interference from magnets, it actually changes as you throttle up and down. Still probably possible to compensate for, but it starts getting ugly.
200 Hertz for 9 degrees of freedom + filtering + DCM / Quaternion calculations is more than sufficient for anything I can think of, since the data is already filtered you need to take that into account.
(AHRS) Attitude Heading Reference System is an industry (marine is where I'm familiar with it) term for what this is.
Comments
https://www.youtube.com/watch?v=w-qEIkz90b4&fmt=18
I basically just went through the Quick Start Guide and started recording video. I would like to put one on a Scorsby Table for a while in the near future and see how it does. My hands are a little too shaky to get very good data ;)
I am grateful with you and your work!
This tri rotor puts an exceptional amount of current through the wires & is way beyond what a commercial AHRS has to endure, but it shows how much a magnetometer can be affected by a hobby vehicle.
i can see some interference, but it is very small and obviously it could be placed further than electrical systems.
i am using closed loop control using AHRS data (using 3 axis magnetometer) and all correct!
jlcortex
nmine.com
(AHRS) Attitude Heading Reference System is an industry (marine is where I'm familiar with it) term for what this is.
> than we do here on earth.
Next week's $30 IMU/AHRS will have star trackers.
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