Hiranya Agarwal

Project 03 of 06 / Competition robotics

VEX Over Under

VEX is the world's largest school robotics competition, and Over Under was its 2023/24 game. Seven years of it ended with this robot: one machine that had to score, cross a barrier and climb, and a team that had to make it work twice on the same day.

Role
Captain and lead programmer
Team
41103A NextGen, seven students
Period
2018 to 2024
Result
Two time national champion
The 41103A competition robot on its case in the pit, with numbered markers identifying its mechanisms.
The Over Under robot, 2023 to 2024 season. Open the numbered notes below to explore the mechanisms.
Intake rollers

Pull triballs off the floor and transfer them to the scoring mechanism.

Team plate

41103A, Team NextGen from Pedare Christian College in Adelaide.

Gear train

High-strength gears on the scoring mechanism, packaged around the intake.

Pneumatics and wiring

Air lines connect the folding wings and end-game climb to mechanisms driven by the C++ control code I wrote.

Drivetrain

Encoders and an inertial sensor feed the autonomous control software.

The challenge

Build one robot that scores, traverses and climbs, and does it the same way every match.

Over Under asked for triball handling, movement across a central barrier and an end game elevation climb. Any one of those is a mechanism. All three at once is a packaging argument, and the autonomous routine only works if the robot ends up in the same place it did in practice.

The build

The pit, the seven people who ran it, and the trophies.

Photographs from the 2023/24 Over Under season, at the Australian national championship and at the world championship in Dallas.

The seven person team seated around a table with the robot and two VEX Robotics Competition trophies, in front of a national championship banner.
The sevenThe full team with the robot and the national championship trophies. Everyone here owned a part of the build.
The seven team members in suits standing in a row on a beachfront path, Hiranya in the centre in a checked jacket.
The seven, off the fieldSame seven people, no robot. Six years of building things together does that.
Team members in the pit area at the VEX World Championship in Dallas, standing beside the 41103A pit banner among hundreds of other team stands.
Pit floor, DallasThe world championship pit. Roughly 820 teams from more than 70 countries, and every one of them within walking distance of your bench.

Control stack

Fuse several imperfect sensors into one repeatable field position.

No single sensor on a VEX robot is trustworthy on its own. Encoders drift when a wheel slips, the inertial sensor drifts over a match, and neither of them knows where the field is. Combining them is what makes an autonomous routine survive contact.

The control loop that keeps the robot where it thinks it is A closed control loop. An inertial sensor supplies heading, drive encoders supply wheel movement and a colour sensor reads field state. The C++ code fuses those three into one estimate of where the robot is on the field, because no single one of them is trustworthy alone. That estimate feeds the autonomous routine or the driver's commands, which drive the motors, which move the robot, which changes what the sensors read. The loop closes back on itself. Sensors inertial, heading encoders, movement colour, field state Sensor fusionone field position C++ controlautonomous or driver Motorsdrive and mechanisms The robot on the fieldand whatever hits it measured again moves

Scroll sideways to see the whole diagram

Why fusion, and not one sensorEncoders drift the moment a wheel slips, the inertial sensor drifts across a match, and neither of them knows where the field is. Combined, they survive contact with another robot, which is the only condition that matters.

My contribution

Own the code, shape the mechanisms, run the team.

  1. Program the full control stack. Wrote the autonomous and driver control code in C++, including the sensor fusion the routines depend on.
  2. Design the pneumatic mechanisms. Developed the intake, scoring and elevation climb systems and the packaging that let all three coexist.
  3. Lead competition execution. Ran strategy, driver training and event preparation for a seven person team.
  4. Build capability around the team. Mentored junior teams and helped organise the 2022 Australian National VEX Championship.
National result
Back to back Australian titles
International result
Two world championship qualifications
2023-24 season
World Championship Sportsmanship Award
Venue
Dallas, Texas

Previous builds

Over Under was the last robot, not the first.

Six seasons came before it. Each game changed the scoring objects and the field, so each year the mechanisms were designed again from nothing, and each year the code and the drivetrain carried a little more of what the last one taught us. These two are earlier season robots from the same programme.

An earlier season robot lit with coloured light, showing the flywheel, the gear train, the drive motors and a NextGen name plate across the front of the chassis.
Earlier season robotA previous year's build. Flywheel and gear train on the upper deck, drive motors underneath, and the team plate across the front.
An earlier robot beside a home practice field, with pneumatic cylinders and a folding arm visible and scoring discs stacked on the floor nearby.
Home practice fieldAn earlier build next to the practice field it was tuned on. Most of the driving hours happened here rather than at events.

Coverage

What other people wrote about it.

Team 41103A, competing as NextGen out of Pedare Christian College, was the only South Australian team to qualify for the 2024 world championship. Two pieces of coverage from that season:

Press

SA VEX robotics team makes history at the World Championship in Texas
Glam Adelaide, 5 May 2024. The event drew roughly 117,000 competitors from more than 70 countries.

Radio

The Pedare robot, Adelaide Mornings
ABC Radio Adelaide. The team on air about the robot we took to Dallas.