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Self Driving Vehicle

Let's say you are standing somewhere in a room and would like to find the shortest path to a goal. You can see a few obstacles, such as a table, that you would like to avoid. The easiest way to solve the problem (if you are a computer) is to divide the room into many small squares (cells) and then use the common A* (A Star) search algorithm to find the shortest path.

But what if you are a car and can't turn around 360 degrees like a human can, then you have a problem! Well, at least until you learn the Hybrid A Star search algorithm. With that algorithm you will be able to find a fully drivable path to the goal!

Click for YouTube video of the algorithm in action:

Link to youtube video

If you just want to play around with it you can download a build of the project here for Windows: https://habrador.itch.io/hybrid-a-star

Tell how the algorithm works

You can read more about it here: https://blog.habrador.com/2015/11/explaining-hybrid-star-pathfinding.html

Is this something actually being used by car companies?

Yes! Tesla mentioned the algorithm in a Tesla AI Day presentation (roughly at 1 hour 20 minutes). So if you ever wondered how the Tesla "Smart Summon" feature works then now you know! Tesla has included a short description of the Smart Summon feature (which is part of the Full Self-Driving Capability (FSD) version of Tesla Autopilot) in the Model Y Manual. We can assume it's the same implementation for other Tesla models, such as Model S.

  • "Smart Summon works with the Tesla mobile app when your phone is located within approximately 6 meters of Model Y." My implementation works over distances of greater than 6 meters.

  • "Smart Summon may not stop for all objects (especially very low objects such as some curbs, or very high objects such as a shelf) and may not react to all traffic. Smart Summon does not recognize the direction of traffic, does not navigate around empty parking spaces, and may not anticipate crossing traffic." My implementation has fixed obstacles only, and they all have the same height. I actually planned to add moving objects and traffic lanes with direction, but will not do so because Tesla's implementation can't handle them.

  • "Touch the crosshair icon then drag the map to position the pin on a chosen destination. Press and hold the GO TO TARGET button. Model Y moves to the destination." My implementation is not just moving to a destination, but also with a specific target direction, such as the left door ends up infront of you.

FAQ

  • What software do I need? To make this project work you need Unity. I've used Unity 2017 and 2018 but other versions should work as well.

  • Is it working on a navmesh? No, it's not! The algorithm needs a grid with cells to be able to remove unnecessary nodes, or you will end up with an infinite amount of nodes.

TODO

  • Upgrade to latest Unity version
  • The car can follow the generated paths with great accuracy, but the truck with trailer is not that good at following the path. That has to be fixed!

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