Human-Following Utility Trailer

[Théo Gautier] thought that a human-following utility trailer would be helpful for people working on farms. He didn’t just think about it, however, he designed and built it as a final project at the Agrilab FabAcademy at the University UniLasalle Polytechnique in northern France. He took the idea from concept to fruition in six weeks.

His build log documents the project very well, and takes you through his design choices and their implementation. The brains of the cart are a SAMD21E board that he made himself, and its sensory perception of the world is provided by HC-SR04 ultrasonic sensors and a PixyCam 2. Locomotion is provided by four each 100W DC motor / gearbox assemblies. He’s put a lot of effort into the construction process and posted a lot of photos of the intermediate steps. One piece of advice that caught our eye was to measure the diagonals of your frame repeatedly when welding it together — things can and do shift around. If you don’t, you may have to rectify the mistake like [Théo] did, with a big hammer.

You can watch the final result in this short video, and see the trailer following him around the farm. In this version, the leader has to wear a red shirt to be properly tracked, but future versions can be made to track a variety of wardrobes. This project was a great learning experience, and could also be a great baseline for future cart-like robots. Do you have any ideas for expanding this design? [Théo] has already mentioned he wants more powerful motors. And if you are into this genre, check out this motorized 3000 W electric wheelbarrow we wrote about a few years ago or radio controlled electric wheelbarrow racing from 2019 (what could possibly go wrong with that?). Thanks to FabAcademy instructor [Luc Hanneuse] for sending in this tip.

27 thoughts on “Human-Following Utility Trailer

  1. For me it would be nice to have a chicken following vehicle. Since they are wandering freely it happens that predators are visiting them too… such following vehicle would prevent this (they are scared of anything bigger, non standard – like dog) . As a bonus this could take water and food on top…

      1. High vis collar would do it.

        It would probably be best if this thing was also set to follow a high vis vest that gets left with it. If you multiple you might need different vests though.

      1. Not so outlandish to think those companies that rent luggage carts at the airport could modernize their offering to support your suggested functionality…

        $1 cart rental, you push the cart with your luggage and the added burden of a battery and motors that aren’t doing anything
        $3 cart rental, it follows you through the airport with your luggage leaving you hands-free. After you’re done with it, the thing returns itself to the rental (charging) rack

    1. Wheels on one side turn more slowly, or opposite of, the other side. Works best on surfaces/wheels without too much grip since wheels have to slide sideways a bit. Especially when doing pivot steer (spin in place).

      1. From a quick reading of his posted code, the robot simply doesn’t turn. The motor control code is only able to run all four motors at 0, 50, or 100%. Given the amount of work to do in one semester, presumably while taking other classes, this seems pretty reasonable. Especially, if say, the student is in Bio and Ag Engineering and not computer science.

        So by “pinned forward”, I think snarkysparky meant “all the motors always receive the same command”. This is also how the user can walk to the side and then loop around to turn the device off. Otherwise, everytime you walked over to get something out of it, it would back away from you.

        Which would be “hilarious*. I think that is a mandatory next step. :-)

        I’m going to have to find a ready-made platform and try something like this. I think there’s something at Tractor Supply I could hack into shape. It would be rougher than this, but maybe good enough.

  2. I thought about building something like this for about 10 years now. And as always when it happens that someone manages to build something I have imagined for a while, I am at the same time offended, that someone did it before me and pleased that the idea itself works. So props to the builder! I just wish I had more time for projects.

  3. One interesting way to track the human is to make them wear a belt with a QR code. The rise and fall of QR code in the camera’s FOV will help how far the person is or how close. In addition to that a person wearing a red colored other than the owner wont confuse the robot as to whom to follow.

  4. Shrink it a little & turn it into a beach cart for those who insist on hauling a cooler, multiple umbrellas, chairs, towels, blankets& an absurd quantity of toys onto the beach. New word du jour – shoobies.

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