Saving our vacations – one robot at a time

This Monday, children in Switzerland are flocking back to school after seven weeks of staying and learning at home. Of course, there was the vacation around Easter our two girls had been looking forward to, but alas: Horseriding camp for Ayana: Cancelled. Robot programming course for Sofiya: Cancelled.

Not having a horse, compensating Ayana for her lost week of vacation, was difficult. But we did find to fulfill at least Sofiya's wish and make Ayana happy as well.

We had looked at the Thymio robot earlier, but this time we ordered a used one on eBay. Thymio is is a small differential-drive mobile robot. It has five infrared sensors on the front and two on the back to detect obstacles, and two on the bottom to identify ground. There are five buttons on the top, a three-axis accelerometer, a microphone, a remote control and a thermometer. The robot also has RGB LEDs on its top and bottom body, so it can shine in any color chosen, and a sound synthesizer. Thymio had been initially developed at Swiss universities ETH Zurich and EPF Lausanne, and both its hardware schematics and software are open source (see https://thymio.org).

We introduced the girls to the visual programming language (VPL) and gave them little challenges they had to sort out themselves. One of the exercises was to program Thymio to follow a child’s hand. It took the children a moment to figure out that the trigger to set the robot in motion was any one of the front proximity sensors, but then they did it: As soon as one sensor detected the hand approaching, the two motors had to move so Thymio was approaching the hand, until the hand moved in another direction, upon which another one of the five sensors would trigger. Another challenge made them build a control system to have the Thymio escape from a maze of books, first by merely pushing directional buttons, but the next day by finding its way out by itself.

Soon enough, the girls got frustrated by the relatively monotonous task of combining triggers and actions, as they wanted to simplify their code and to make their Thymio smarter. Now we introduced them to the advanced programming mode, in which it is possible to have the Thymio react differently to a trigger depending on what condition had been set before.

To our surprise, the most fascinating feature of the Thymio proofed to be the small hole in the center of the Thymio’s body, where a felt pen could be mounted that would draw a line on the floor as the Thymio progressed. Suddenly, we were deep in linear geometry: If you wanted to draw a square, how long would the Thymio have to advance before it stopped? And once come to a halt, how long would it have to turn to describe a 90 degrees angle before it could start moving again.

So this is how a little plastic robot saved our children’s vacation. Almost. On the last day of our two weeks’ course, the girls converted the Thymio into a hotel shuttle, following a black line drawn on the floor: On the curved scenic route following the shore from the airport to the hotel, then, after unloading some and loading other Lego characters, on the straight motorway directly back to the airport.

There is still hope.

PS: I believe in Open Source. Should you be interested in a short description of the challenges and a copy of the VBL scripts, just send me a direct message.