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The Twike; half-bike & half-car powered by a Raspberry Pi

03 November 2016

The electric pedal cars with two seats will soon be a snap to drive thanks to a more efficient pedalling system and a compact on-board computer.

Adrien Hoffet in his Twike (Credit: Alain Herzog 2016)

The Twike, manufactured by FINE Mobile, is half-bike and half-electric car: it has an engine, pedals, a lightweight frame, and room for a passenger. All these factors make it ideal for city use, yet its interior remains a bit rudimentary. More specifically, Twikes could use a better on-board electronics system and improvements to the pedalling mechanism. Adrien Hoffet, now an EPFL graduate, went about improving the Twike for his Master’s project.

Embedded electronics for easier driving

For the Twike – “twin” and “bike” – to be taken seriously as an alternative form of urban transport, it needed a navigation system. So the electrical engineering student integrated a Raspberry Pi mini-computer. This compact device, connected to the serial bus that transmits signals and data, collects and displays useful information for drivers. Various parameters – such as speed, pedalling power and battery life – appear on the screen. It can also store data for statistical purposes or analysis. This system was implemented on the current version of the vehicle – the Twike 3 – but it’s actually designed to exploit even more data on the new Twike that should come out in the next year or two.

Pedalling fast, not hard

Another significant problem with the Twike is that its drivetrain is similar to that of a bicycle (gear and chain), which complicates the vehicle’s mechanics and maintenance and makes it noisy. “Since Twikes have only five speeds, you end up having to pedal too fast at higher speeds,” Hoffet said. FINE Mobile therefore asked Hoffet to develop a lightweight, silent pedalling system that would give riders more leeway in the effort they expend. In response, Hoffet added a motor and an electronic feature run by the vehicle’s Raspberry Pi computer. The added electronics measure battery performance and pedalling speed. By monitoring this data, the computer can reduce pedal resistance. Some final adjustments still need to be made to the system before its completely finalised.

Twiking from Germany to Switzerland

The eco-friendly Twike was invented in Switzerland in the 1990s but is now manufactured by FINE Mobile in Rosenthal, in the heart of Germany. That’s where Hoffet spent six months working on his project. “I first realised how handy Twikes can be when I was at EPFL and saw a researcher come to campus in one,” Hoffet said. And when his internship at another company fell through, he applied to work at FINE Mobile. The timing turned out to be perfect, since the company was in the middle of developing a new model. In his spare time, Hoffet renovated a Twike at the company’s site and used it to return to Switzerland – at a top speed of 85km/h.

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