Position Tracking

Tags: Control, Innovate, and Software
Personhours: 4
Position Tracking By Abhi

Task: Design a way to track the robot's location

Throughout the Relic Recovery season, we have had many issues with the autonomous being inaccurate simply because the scoring was dependent on perfectly aligning the robot on the balancing stone. This was prone to many issues as evidenced by numerous matches in which our autonomous failed. Thus far, we had relied on the encoders on the mecanum chassis to input distances and such. Though this worked to a significant degree, the bot was still prone to loss from drift and running into the glyph pit. We don't know if glyphs will be reused or not but we definitely needed a better tracking mechanism on the field to be more efficient.

After some investigation online and discussing with other teams, I thought about a way to make a tracker. For the sake of testing, we built a small chassis with two perpendicular REV rails. Then, with the help of new trainees for Iron Reign, we attached two omni wheels on opposite sides of the chassis, as seen in the image above. To this, we added axle encoders to track the movement of the omni wheels.

The reason the axles of these omnis was not dependent of any motors was because we wanted to avoid any error from the motors themselves. By making the omni wheels free spinning, no matter what the encoder reads on the robot, the omni wheels will always move whichever direction the robot is moving. Therefore, the omni wheels will generally give a more accurate reading of position.

To test the concept, we attached the apparatus to ARGOS. With some upgrades to the ARGOS code by using the IMU and omni wheels, we added some basic trigonometry to the code to accurately track the position. The omni setup was relatively accurate and may be used for future projects and robots.

Next Steps

Now that we have a prototype to track position without using too many resources, we need to test it on an actual FTC chassis. Depending on whether or not there is terrain in Rover Ruckus, the use of this system will change. Until then, we can still experiment with this and develop a useful multipurpose sensor.

Written on July 18, 2018