21 April 2018 
22 August 2017

Scientists electrify historic dandy horse

Small children still use a form of the so-called dandy horse, balance bike or draisine, which the inventor Karl von Drais first tested on a longer route on 12 June 1817. Now, 200 years later, computer scientists at Saarland University are making the forerunner of the bicycle attractive for adults. Their prototype, still made of wood, contains an e-motor, battery, sensors and mini-computer.

Photo: Oliver DietzePhoto: Oliver Dietze
Professor Holger Hermanns riding the Dandy Horse, in the background research team member Florian Schiessl, on the right the Belgian bicycle engineer Dries Callebaut
With their “Draisine 200.0” the computer scientists are testing the validity of mathematical proofs, among other things to improve the safety of e-bike software. Holger Hermanns is a professor of computer science at Saarland University. With his basic research, he wants to help the fast-growing e-bike industry avoid programming errors that have already affected other industries. “If we succeed in making automatic software verification an industry standard, we will no longer have to go through things like the diesel scandal,” says Hermanns.

In 2011 he presented a wireless bicycle brake. He proved the reliability of the radio-based brake through mathematical methods, which are also used in the control systems of aircraft or chemical plants. In 2016 he was awarded by the European Research Council with a 2.4 million euro Advanced Grant. With this grant, Holger Hermanns seeks to advance e-bike software in the area of operational safety. Then Hermanns learned that 12 June 2017 would be the 200th anniversary of the first bicycle tour. He decided to replicate Drais’ dandy horse – equipped with an electric drive.

Draisine 200.0

Together with Dries Callebaut, a Belgian bicycle engineer, in a few months he developed a prototype for the “Draisine 200.0”. To honour Karl von Drais, the follow-on model is built completely of wood and is braked using a sort of foot pedal on the wooden front wheel. In the center of the wooden back wheel is a 200 W electric motor, driven by a 750?g battery. Through a cable, the electric motor is connected to a mini-computer, which sits on the frame and controls the motor with the help of a speed sensor. However, this in particular has proven to be difficult.

“With conventional electric bikes, the motor turns on when the pedals move, but the dandy horse does not have these,” explains Hermanns. Therefore, working out exactly when the rider is pushing the dandy horse is a challenge, making the fine-tuning of the developed control software nerve-racking. Anyhow, their efforts have paid off: the third prototype – with mini-computer, battery and speed sensor now hidden completely inside the wood frame – is no longer affected by strong vibrations. For Professor Hermanns’ research group, this is, however, only the beginning: “We will now verify the correctness of the software, i.?e., mathematically prove that the motor will not run faster than the allowed top speed and the battery will not be overloaded,” explains Hermanns.


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