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Unread 31-12-2014, 21:32
Richard100 Richard100 is offline
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FRC #0836 (RoboBees)
Team Role: Mentor
 
Join Date: Nov 2009
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Got Gyro drift? Try Sensor Fusion !

The RoboBees release a simple Inertial Measurement Unit (IMU) based Attitude and Heading Reference System (AHRS), written in LabVIEW.

There are several commercial, automotive grade devices available that are IMU-based and maintain good quality orientation (Roll, Pitch, and Yaw) information over time. Some are within reach of well-financed FRC teams. Here’s some free code that lowers the entry cost for teams that would like to eliminate the drift associated with KoP Rate Gyroscope sensors and try their hand at integrating a basic AHRS into their next robot design. This code is compatible with the AdaFruit.com 9-DoF IMU, product ID 1714, which runs about $20 (no affiliation). This breakout board contains a triaxial Accelerometer, Rate Gyroscope, and Magnetometer, powered by 5 VDC and interfaced over the I2C bus (cRIO and RoboRIO compatible).

The Magnetometer sensor is likely to be new to many teams, and challenges remain in successfully integrating it on an FRC bot, but its contribution is critical to stabilize what is arguably a robot’s most important rotation - Yaw. The simple Complementary Filter is applied to fuse the three sensors into a single composite sensor which provides accurate and stable rotation indications in all 3 dimensions (Roll, Pitch, and Yaw). This sensor fusion approach effectively combines the individual sensor's best respective properties while mitigating their individual shortfalls. Code runs on the cRIO with last year’s version of LabVIEW, and should easily port once FIRST releases this season’s LabVIEW version for the new RoboRIO.

IMU calibration can be involved and a bit esoteric … the code guides you through a simplified calibration process to help you get the most out of your sensor. The various IMU code modules are patterned after the familiar WPI sensor VIs. There’s no coprocessor to integrate or soldering/assembly. The concept behind the released demonstration project is to have you up and running by simply plugging in the IMU and supplying your FRC Team number to the LabVIEW Project file.

The files have a bunch of comments for how the code works, equation references, and implementation considerations to promote learning about this powerful technology. Bug reports are welcome!

Best wishes to all FRC teams this season, the RoboBees are excited about seeing you out on the field!

The RoboBees FRC Team 836

[Edit:Code updated 1 Jan 15 to include all required dependencies.]
Attached Files
File Type: zip AdaIMU.zip (568.1 KB, 648 views)

Last edited by Richard100 : 01-01-2015 at 12:28.
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