Open Source IMU designed for FIRST robotics

[slibert]

Team 2465 (Kauaibots) has completed initial development of the Nav6 Open source IMU. This project includes:

- Open source hardware (Eagle PCB file, Bill of Materials)
- Open source hardware (Arduino-compatible source code)
- Software to integrate the IMU into a C++-based CRio robot project

The "nav6" inertial measurement unit (IMU) was developed to provide sophisticated inertial navigation capabilities easily available to student robotics teams, including the FIRST Robotics Challenge (FRC). This low-cost circuit board enables a 4-wheel omni-directional drive robot to be driven in "field-oriented" drive mode by accurately measuring the robots "pose" - the amount of tip, tilt and rotation - relative to the field. Additionally, the nav6 can be used to implement robot balancing algorithms.

The nav6 features the powerful Invensense MPU-6050 IC which includes a 3-axis accelerometer, a 3-axis gyroscope and an on-chip digital motion processor. The nav6 employs sophisticated motion processing algorithms provided by the "Digital Motion Processor" (DMP) included with the MPU-6050. The result: highly accurate tip/tilt, and accurate yaw that exhibits minimal drift of approximately 1 degree per minute. The sensor provides a 200Hz update rate, excellent for use in robotic systems.

The nav6 also includes a Honeywell HMC5883L 3-axis magnetometer. Although the magnetometer compass readings are unreliable when robot motors are energized, it is useful for establishing absolute orientation at the beginning of a competition. Combined with the nav6 "pose" and this initial orientation, a robot's absolute orientation throughout a competition match can be maintained.

The nav6 has been designed specifically to enable easy integration into a FRC robotics control system: it's power connection connects directly to an unregulated 12V output on the Power Distribution Board and it's data connection connects directly to the cRio serial port. Additionally, source code for easy integration into the FRC cRio controller is also provided.

As an added bonus, the nav6 is Arduino-compatible, and can be re-programmed by anyone via the free Arduino Integrated Development Environment (IDE).

Links to the open source hardware/software project, and the CRio software to interface with this IMU, are at: https://code.google.com/p/nav6/

Advanced soldering skills are required if you want to build it, but I'd be happy to indicate where you can get the board fabricated and provide some guidance on how assemble it with a minimum of tools. I'm also open to having some assembled for a low cost if there's enough interest.

As an alternative, it should also be possible to adapt the firmware to run on open-source boards w/the MPU-6050 and the HMC5883L, these can be found at Sparkfun. The ArduIMU +V3 (https://www.sparkfun.com/products/11055) is $79.95 and features almost identical ICs, however it doesn't have the on-board RS-232 IC/connector so you'd need to take care of that detail.

If you have any questions, please let me know.

Cheers,

- scott

Scott Libert
Control System Mentor
Team 2464 (Kauaibots)