Data gathering is carried out by special measurement instrumentation which is unique worldwide. Measurements take place under real world conditions, directly on the test bikes while they are being ridden.
The special measurement instrumentation was first employed in 2009 and has been continuously updated ever since. This technology, valued at over € 200,000, was developed in collaboration with companies OTEC from Bensheim and Calantec from Berlin.
Measurement under real world conditions
Measurements take place under real world conditions, directly on the test bikes while they are being ridden. This allows ride performance to be recorded undistorted. The heart of the measurement equipment, the Databox, is carried in a handlebar bag, and into it flows all of the data provided by sensors distributed around the bike. Energy use from the battery, speed, pedalling cadence and pedalling effort are measured, as well as tracking the ride via GPS.
A sensor is fitted inside the original battery for each test bike, so that energy use (current times voltage) can be measured. This sensor is located either within the battery housing, or outside it via a plug connection. Current and voltage signals are transmitted to the Databox via an analogue signal.
Pedal cadence and speed
Cadence and speed are measured by magnetic sensors attached respectively to the bottom bracket and to a front fork blade, and connected to the Databox by cables.
Pedalling effort is measured using special instrumented pedals. These measure the force applied to the pedals via the resulting deformation of the pedal body. The magnitude of this deformation is measured via integrated magnets and a Hall sensor. The raw data are processed in a slim housing installed parallel to the cranks, and then transmitted wirelessly to the Databox. Using this data the power applied by the rider can be determined, and this can in turn be used to calculate the power assist level from the motor. One advantage of using this power measurement system is the ease of fitting and removing the power measurement pedals, an essential factor for the smooth running of the test.
A GPS receiver is connected to the Databox to record precise route data, and this documents the entire ride for later analysis. This ensures that the data can at a later stage be filtered metre by metre, i.e. for the different test circuit sections.
The Databox, fitted into the handlebar bag, records all of the data, amounting to about 12 MB per test ride, both on its internal memory and onto a USB stick. After the test ride the USB stick is removed and the data saved on a PC. Analysis is conducted using Matlab software.
Read further background information in the ExtraEnergy Magazine:
Copy: ExtraEnergy e.V., Frieder Herb, Angela Budde
Translation: Peter Eland
Online publication: Angela Budde
8 October 2016