Professor Holger Hermanns and the wireless brake system (via Saarland University)
What is 99.999999999997 safe and has a 250 milli-second delay? It is the wireless bicycle brake from Saarland University. Professor Holger Hermanns, lead designer on the project, had this to say about the reliability, "... out of a trillion braking attempts, we have three failures. That is not perfect, but acceptable."
With pressure sensors in the bicycle's grips, the rider has to just squeeze. The system interprets how hard the person in squeezing, and adjusts the brake's clamping power proportionately. The transmitter, blue box on the handle bars, relays the signal to the breaking apparatus. The system uses a TDMA-based communication link (2.4GHz ISM band, MyriaNed wireless node). Each node is run with an Atmel atxmega128A1 and a Nordic Semiconductor NRF24L01GNRF24L01G+ transceiver. According to the design team, adding additional signal repeaters does not increase the reliability.
The clamping force is applied with what looks to be a stepper motor or large solenoid. The power demands of a stepper motor would be less strenuous, so I am leaning in that direction. Either way, the team stated that making a anti-lock brake system is entirely possible. Right now the team is more focused on defeating the 250milli-second delay. As they stated, "Its current configuration enables the cruiser bike to brake within 250 milliseconds. This means that at a speed of 30 kilometers per hour, the cyclist has to react two meters before reaching the dangerous situation."
Looking for a job in Germany? Professor Hermanns is looking for engineers who understand his concept of wireless braking to help with his efforts. The project is funded by the German Research Foundation under the "Automatic Verification and Analysis of Complex Systems (AVACS)" label. Read more about the fundamentals and technology behind the wireless brake in Professor Hermanns's paper, "A Verified Wireless Safety Critical Hard Real-Time Design." Note the file name, "wowmom.pdf."
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