There are seven challenges at the in-person event for PiWars 2024, each with their own problems to solve. They are split in to three categories: Autonomous only, Autonomous/Remote, Remote Only. For the second of those, if you are in the Advanced/Professional category you have to attempt the challenge autonomously.

State of the Onion

NE-Five exists as a robot, the base hardware is all there and everything has met the minimum requirements as I’ve set them, the devil is in the detail though and integration hell is totally a thing. Also, perfect is the enemy of done and I really need to get a focus on what needs doing now vs what would be nice to have.

Motor control

Motor control has been overhauled with the switch from Red Robotics RedBoard hat to the Pimoroni Yukon. The big difference is the latter has support for encoders, but it also has on board processing which means that processing load is taken away from the overhead on the Raspberry Pi. I also have a ROS node for the Yukon so it can send and receive ROS messages such as motor velocity commands and odometry.

Servo Control

I’ve implemented a new ROS node that not only takes commands to move the robots arms but also provides joint state feedback to the wider ROS system, this also includes the neck servos as they are the same Dynamixel smart servos used in the wrists. The linear actuator that adjusts how high the robot is standing has also been hooked up to the Yukon, it has a feedback line that is factored in too. Each of the smart servos is independent of the Pi too as you give them a command and they do it, handling any PID loops and monitoring internally as needed.

Camera System

I’m still using the Luxonis FFC-3P camera system, with two wide angle global shutter cameras and a narrower field rolling shutter camera in the centre position. Luxonis have recently released a big update that includes on-device pointcloud generation. Previously I was trying to do this on the Pi and it was basically taking all the resources just to do that. Having this board run tasks itself and only providing the data the Pi needs is a big win for sure.

I’ve also been playing around with object recognition, it works and you can run custom neural networks on their which, again, means the Pi doesn’t have to do anything but use the data it produces.

Back to the Challenges…

The robot works great in remote control mode, it’s currently the only mode however which isn’t ideal. There are five challenges I’ll have to tackle autonomously so I’ll concentrate on those for now.

Lava Palava

This is a line following drag race, there is a course with a black floor and white strip down the middle which the robot has to follow as quickly as possible. The course has a chicane in it from previous years but this year will also have a speedhump.

With the motor encoders providing feedback with regards to distance travelled and the camera system able to detect objects, I intend to combine the two to have it aim for a goal that’s X meters in front of the robot and have it follow the line until it’s travelled that far. Or until I push the estop button if it tries to run away…


In this challenge you have to sort a number of red and green barrels in to blue or yellow areas of the arena. Starting in one corner of the arena, NE-Five should be tall enough to be able to detect all the objects it needs to look out for, the start position and two sorting zones are also known locations which helps. Using a similar setup to Lava Palava I should be able to use the detected barrels to position the robot relative to them so it can pick them up. Using odometry and being able to see the coloured sorting zones, it should be able to navigate to them to drop them as needed.

Escape Route

This challenge has to be run without the robot’s operator being able to see the arena directly. For remote control this means using cameras or have someone shouting out commands, for autonomous the operator needs to be behind a screen still but only press “go” and hope for the best.

The arena will be in a randomly selected configuration out of six possible layouts. There are three coloured blocks, each having known dimensions. The plan is that as soon as the challenge begins, the robot scans to see which block is closest and add a waypoint to get passed it. After it gets there, or while en route, it can look for the next block and figure out its next steps there too.

Similar to Lava Palava, where it’s aiming for a point a certain distance ahead, the end goal will be passed the yellow line with intermediate steps to get around each block. The depth camera already has an option to convert a depth image to laser scan so should be relatively easy to detect a clear path.


For this one, the robot will have to look for an illuminated red square and move to it. Once it has visited that square another will light up, the process repeats. As with Escape Route and Lava Palava I’ll be looking for the specific colour of the square but this time I’ll be setting it as the waypoint to move towards. Once it detects it’s on top of a red square, it’ll stop. Once the red switches off it’ll start looking around for anything of the same colour, with the wide angle stereo cameras this should give a good field of view for this and the odometry once again comes in to play.

Zombie Apocalypse

This one is currently the biggest unknown as I don’t have a projectile launcher for the robot yet, I do have a pile of parts however… Sample designs for the zombie targets have been released though, so I’m planning on trying to detect those to use for the coordinates. I have parts from an electrically fired Nerf gun so will mount that on a pair of servos for pan/tilt and use them to aim at the target. I also have a green laser for this, so hopefully will be able to detect when the laser is within an area in the centre of the target before firing.

If’s, But’s, And Maybe’s…

Other than for the last challenge, I pretty much have everything in place. The devil’s in the details with these things but I’m in a considerably better position than any previous competition which is a great feeling. What are the priorities though?

The Toad List

What needs doing?

  • Nerf gun and mounting hardware
  • Camera to provide coordinates of:
    • A white line, it’ll have length rather than being point data so probably just “make sure white line is in the middle of the view”
    • A zombie, there will be multiple at different heights, the higher ones having more points available. Primarily we’ll need the X,Y coordinates but detecting distance will help ensure were detecting the right things as they’ll all be on a plane.
    • Coloured boxes, these will be used as signposts and will need to be avoided. Depth to laserscan for obstacle detection.
    • Coloured barrels to pick up and navigate around, this will need pose estimation.
    • Coloured flooring, for both mine sweeper and Eco Disaster
  • Arm control to ensure coordinates are in the same system as the camera, this is for picking up the barrels
  • Waypoint system, hook in to odometry to have the robot follow a path.
  • Robot pose estimation, where is the robot and which way is it pointing?

There is a common theme in that a lot of the challenges have overlapping needs but there’s a lot of work to do.

Load’s of time though, right?