This week I made some key decisions regarding the physical robot implementation. Last week I wrestled with the dilemma that our original cheap Amazon robot chassis didn’t have proper encoder information. To determine next steps I weighed a lot of factors:
First, how necessary are encoders when we have an IMU? Quick search shows that encoder feedback data cannot be replaced by our 6DOF IMU units, and is very important to have long-run viable localization. Encoder data complemented by IMU data makes for the most accurate. Thus, I pursued encoder data further.
Secondly, how possible is it to jerry-rig optical sensors onto the bottom of the existing chassis? It’s cheap! 4-pack (one for each wheel) for $9 bucks on Amazon. But the footprint underneath the chassis is very small, and doesn’t allow for ample sensor room, additionally, there’s no where to mount them! I decided this solution is no easily replicable nor reliable, and this is important for the sake of SWARM since our goal is to have multiple identical robots at the end of the semester.
Lastly, we come to the option of buying a new chassis. What kit to get? Encoder motors and sufficient product specifications are necessary this time in order to make sure we don’t get misled by the advertising again. Between the two reliable suppliers that I found, HiWonder and Yahboom, they had high quality encoder motors, compatible motor drive boards, battery and battery charger kits, larger chassis footprint and mounting points, and much more security through documentation. The ultimate decision came down to drive train, where the Yahboom chassis had differential drive, vs. HiWonder’s Ackermann drive train. Ackermann drive train doesn’t enable turning in place, and we determined as a team that this was important for our 2D mapping use case, where a robot could find itself in a narrow corridor that it needs to get out from.
I updated the BOM with this new product, and returned a bunch of products that I bought for the old chassis to ECE Receiving.
Additionally, with the Design Document due date being this week, I spent the rest of my time towards this. Contributing writing to assorted sections in the doc, and creating new, more comprehensive hardware design visuals to add.