Centerstage BTC robot

The third robot of the season, built to compete among the world's best at the last competition of the year.

Role: Team captain · mechanical
Team: FTC 24500 LITBOT · 2 people
Competition: Bucharest Twin CupCenterstage season, 2023–24

The Centerstage robot on practice field tiles, team number 24500 on the side panel — The finished robot, one day before departure.

The problem

The robot was built for the FIRST Centerstage season, where robots pick hexagonal pieces called PIXELS off the floor and score by placing them on the backdrop. Points also come from climbing the structural trusses at the end of the match, and from launching a paper airplane that has to land inside a designated area.

What I designed

Side profile of the full assembly in Onshape, with some components made transparent to reveal the inner layout of the robot.

An adaptive outtake basket that self-adapts to place PIXELS on the backdrop, giving around 10 cm of flexibility. This reduced the precision required from the driver, made cycles faster, and reduced the likelihood of knocking PIXELS off the backdrop.

The outtake basket held against the backdrop, with PIXELS placed on the board below it — The adaptive outtake placing PIXELS against the backdrop.

A pivoting intake with flexible surgical tubing brushes that could extend about 10 cm outside the robot's frame. That reach let it pick PIXELS out of corners, alongside the truss, and from the five-PIXEL pre-set stacks, all places a static intake inside the frame would struggle to reach.

Close-up of the pivoting intake: surgical tubing brushes on a chain-driven shaft in a laser-cut plywood frame — The pivoting intake: surgical tubing brushes on a chain-driven shaft.

Pull-up hooks mounted on the goBILDA Viper slides scored the 20 ascent points in under two seconds from activation. They doubled as the mounting base for the paper airplane launcher, which was integrated between them so the slides could lift it for the best shooting trajectory, and connecting the hooks together made the whole assembly sturdier.

How it was made

This was the first FTC robot built without access to our school's workshop, which was closed for the summer. The side plates are plywood, laser-cut at KTU's Circular Makerspace, and the majority of mounts, adapters and brush mountings were 3D printed in PLA and ABS. Motors and the control system had to be bought from official suppliers; the mecanum wheels and slides were bought because they needed high reliability over many use cycles, and development time was limited.

A bedroom used as a workshop, robot parts and subassemblies spread over two desks — My bedroom, temporarily converted into a workshop.

What was the hardest part to develop

The hardest component was the intake-to-transfer convergence point, where PIXELS go from an area as wide as the robot to a basket entrance just 90 mm wide. There the PIXELS jammed sideways, pushed each other into the wall, or jumped one on top of another.

Three PIXELS wedged against one another inside the transfer, between the chain-driven shafts — The failure itself: PIXELS jammed in the transfer on an earlier version of the robot, before the discs were added.

To solve it I designed a custom testing bench with adjustable walls, which let me tune the angles a few degrees at a time until one of the PIXELS would always slide, pushing the other out of its path. For the jumping, discs on the transfer shafts reduced vertical play to under 3 mm, so a PIXEL could no longer climb over its neighbour.

The testing bench: two PIXELS between adjustable walls bolted to a plywood board — The bench, walls adjustable a few degrees at a time.

Two 3D-printed spoked discs that mount on the transfer shafts — The discs that cut vertical play to under 3 mm.

What went wrong

We did not account for field tolerances. At home the autonomous period worked perfectly; at the competition we had consistency issues, especially on the later cycles, because the robot's position slowly drifted and we had no way to recalibrate it.

Result

We did not win. We were not second, or third. We were not last either: 10th of 17 alliances. Against a team with five years of experience to our one, holding the world number one ranking and every championship it had entered that season, we put up 258 points to their 306.

Jokūbas setting the robot up on the field at the Bucharest Twin Cup — Jokūbas setting up on the field at the Bucharest Twin Cup.