Computer age makes the dandy horse even dandier

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Professor Holger Hermanns atop the dandy horse. In the background are Florian Schiessl, right, and  Belgian bicycle engineer Dries Callebaut. Photo: Oliver Dietze
Professor Holger Hermanns atop the dandy horse. In the background are Florian Schiessl, right, and  Belgian bicycle engineer Dries Callebaut. Photo: Oliver Dietze

The so-called dandy horse, enjoyed by generations of children for 200 years, has now come of age, with an electric motor, sensors and a mini computer.

The dandy horse, also known as the balance bike or draisine, was the creation of Karl von Drais, who first tested one on a longer route on June 12, 1817.

Now, 200 years later, computer scientists at Germany’s Saarland University are making the forerunner of the bicycle attractive for adults as well.

In honor of the inventor, their prototype is still made completely of wood, but also houses an electric motor, battery, and electronic technology to manage its operation.

As soon as the rider pushes off from the ground, the motor starts and provides additional power during the entire ride.

The computer scientists are still tweaking the supporting software to improve the safety of the electric bike.

Holger Hermanns is a professor of computer science at Saarland University and has also become well-known in the cycling scene.

He wants to help the fast-growing e-bike industry avoid programming errors that have already become the subject of headlines in 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.”

In 2011 he presented a wireless bicycle brake.

He proved the reliability of the radio-based brake through mathematics, which are also used in the control systems of aircraft or chemical plants. The wireless bicycle brake made headlines.

In 2016 the European Research Council awarded him a €2.4 million grant which he is using to advance e-bike software in the area of operational safety.

A few weeks later, Hermanns learned that June 12, 2017 would be the 200th anniversary of the first bicycle tour. He decided to replicate Drais’ dandy horse, this time equipped with an electric drive.

Together with Dries Callebaut, a Belgian bicycle engineer, he developed a prototype for the “Draisine 200.0” over several months. To honor 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-watt electric motor, driven by a 750-gram 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.

The researchers quickly realized that small errors could have potentially catastrophic results.

“Imagine that you jump over a curb, the sensors interpret this as pushing and the electric motor speeds up to its 25kmh top speed,” he explains.

The members of his group, in particular Gereon Fox and Florian Schiessl, are continuing to test the prototypes.

They have even mounted a camera on the frame, to provide video evidence for the correct interplay of human and electric power. To synchronize the video recordings with the measured sensor data, they developed a special LED clock that is read automatically.

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,” he says.

Now, however, the computer science professor wants to take a longer test drive on the current prototype. This is ultimately how it all began 200 years ago.

Sebastian Biewer, Felix Freiberger, and Gilles Nies also worked on the Draisine 200.0.

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