by Joe Spall
This September, RoboJackets will be participating in our first entry of evGrand Prix Autonomous, the go-kart scaled autonomous racing competition. Even though this might be the first time at EVGP, the RoboRacing team has acquired autonomous racing experience over eight years of competition in the likes of IARRC and Sparkfun AVC. The experience brings with it the understanding (and frustration) that things won’t always go as planned. This has led RoboJackets to have a heavy influence in the planning of the competition, with a focus on safety and control.
The evGrand Prix competition was started in 2009 at Purdue University with the focus on manual electric go-kart racing. The competition has since grown over the years in participants and in scope with the introduction of the Autonomous division in 2018. This division has many of the same goals as the original but with the added twist of the go-karts having to drive themselves! With the cancellation of Sparkfun AVC (which served as a large car competition) after the 2018 season, RoboRacing coincidently found themselves looking at evGrand Prix as the next larger vehicle project just as the autonomous division was taking off.
Rules existed for the EVGP Autonomous division, covering topics such as platform requirements and safety, but they seemed to be missing aspects that accounted for the lack of a human driver sitting in the seat, who acts as a final failsafe in the event of malfunction. This lack of a human driver presents important safety concerns that are not as easily handled, such as the car driving uncontrollably at a wall many yards away. With the team’s previous competition experience, this is not a far-fetched situation. Additional complications are that these are approximately 200 lbs robots that could go upwards of 30 mph and the goal is to have multiple cars on the track at once!
RoboRacing set out to propose a safety and control system to try to account for these aspects, championed by the electrical and software subteam members over the past two years. The first component is the Team Safety Remote. This wireless radio remote is designed to turn off motors and apply emergency braking and is to be used by the teams if they identify a loss of control. The next component is the Master Safety Remote. This wireless radio remote is similar to the Team Safety remote, but it is to be used by the competition officials. Both of these remotes provide a hardware level redundant safety control with a focus on simplicity.
The final piece of the proposal is the Race Control System. This system provides high-level race management of the go-karts. Each kart follows a predefined state machine that mirrors the use case in the competition, from being in the garage to finishing the race. Each state has specific requirements such as how soon the kart should be ready to drive and when the kart should stop to reduce unexpected behaviors. It is designed to be used over a wireless network, relying on TCP connections between the karts and a central computer. Brian Cochran, a RoboRacing alumni, has helped develop a cross-platform open source GUI to manage the race to be run on the central computer. The interface allows the management of each individual kart and overall race status, similar to racing flags in F1 or NASCAR. For example, using the green flag in a race indicates the start of competition with our GUI having a direct parallel of the “GREEN_GREEN;” state. You can check out the project for yourself on GitHub, where you can find the GUI software and full proposal! You can also check out a video of the GUI in action on YouTube!
Outside of the safety and control system proposal, the team has taken part in many discussions with the competition officials and the other participating schools. We have worked through ideas such as AprilTags (like a barcode for robots) for improved kart detection, a unified network configuration, and even race track changes. Overall, the team is excited to see how the 2021 evGrand Prix will play out and can’t wait to learn and improve both the karts and competition for next year!