The communication between the coaches and the athletes is extremely important. During the race the athletes receive lide feedback and instruction, for example if they have to maintain a certain power level or have to increase their capacity. The coaches receive live data from the support car about the performances of the athletes and the VeloX, which allows them to change the strategy during a run or give instruction to Rosa and Jennifer.
The VeloX 9 contains four types of sensors: the SRM-sensor, the sensehat, the ‘speed sensor’ and the sensors from Compass. The SRM-sensor measures the power from the athlete (wattage) and the pedal frequency (rpm), the most important data regarding the athlete. The sensehat is placed inside the electrobox and measures the environment within the VeloX 9 (temperature, air pressure, air humidity). The speed sensor is placed on the rear wheel and measures the rotation of the rear wheel. This is used to calculate the speed and travelled distance. Finally, the front fork and the seat contain strain gauges which work on glass-fiber based technology, which measure the deformations and can thus be used to calculate the internal forces.
The sensor data is collected by the raspberry-pi in the electrobox. This is where the data is processed and transferred to a receiver in the support car. We’ve investigated together with City Wireless which type of data transport would be the most suitable and we also looked into the type of receiver and transmitter.
We use a WiFi-protocol on the 2.4gHz waveband, the most used type by consumers. However, the type of equipment that we use is different from standard routers. The data is transferred from a nanostation via a directional antenna from the VeloX 9 to the support car. A normal router is omnidirectional, meaning that it’s signal is sent into all directions. With a directional antenna it is possible to efficiently send a powerful signal in a specific direction, allowing the data to be transferred for over 500 meters while still maintaining a strong and stable connection. Hereafter, the data is transferred via a router to the laptop of the coach and displayed real time thanks to our own software.
The communication between the support car and the athlete is established radiographically using portophones. Each year it is a challenge to ensure stable and powerful communication, because of among other things the extreme conditions in the desert and the materials used in the VeloX (carbon fiber). This year Jacobs Breda Electronics (JBE) looked together with us into possible causes for these problems and helped us by sponsoring the perfect portophones and helping us programming these. Besides us, they are also supporting the Sunweb cycling team with optimizing their communication, and supplying the communication of national cycling races in collaboration with the KNWU (Royal Dutch Cycling Union).
The sponsored Hytera portophones are very light and send on the UHF-band (ultra high frequency). Using UHF it is possible for the portophones to have a smaller antenna, resulting in little used space in the VeloX, and the waves are better able to pass through small openings, which allows them to better pass through the shell of the VeloX. Furthermore, the athletes encounter a high level of ambient noises due to heavy vibrations occurring when going faster than 100 km/h, the sound of the drivetrain (chains, gears and bearings), sound from the contact between tire and road, and the amplification of sound due to the closed shell of the VeloX. Together with JBE we manufactured custom-fit earpieces with a build in speaker and a filter to cancel ambient noise, allowing the coaches to be understandable for Rosa and Jennifer, even at a low volume.