The SOFIE project aims to improve the understanding of bicycle and rider stability in order to increase the safety of elderly cyclists. In the framework of this project, an advanced multi-body model of bicycle and rider dynamics, including the influences of the environment, is developed. The purpose of this model is to test, in the design phase, different concepts of so-called Intelligent Assist Devices (IADs) to enhance cycling safety. The model is validated in a novel experimental setup where under controlled and safe conditions the rider and bicycle can be perturbed to identify the properties of the control mechanisms.
In the setup the rear wheel of the instrumented bicycle rotates freely on a roller bench. The front wheel rotates on a treadmill to preserve the tire-road contact; steering can still be used to maintain balance. The roller bench is situated on a 6 degrees of freedom Stewart platform. The movement of the platform can be controlled in each direction. Therefore, it is possible to apply disturbances to the roll, pitch and yaw and to apply lateral, posterior and superior disturbances to the bicycle with a predetermined multisine disturbance signal.
The bicycle is equipped with sufficient inertial sensors to accurately estimate the current orientations. Furthermore, the laboratory setup allows utilizing a marker-based video system to measure subject and bicycle movements in a global frame. The subject is secured in a safety harness. By analysing experiments in this setup in the mathematical model, the experiments may serve as validation data.
Preliminary results showed that it is well possible to perform perturbation experiments; the actual modelling of the tyre-floor contact proves important in determining the response. Further experiments will be done to estimate the properties of the control system in different categories of riders using system identification, allowing differences between young and elderly subjects to be studied. Subsequently, with the novel experimental setup it is possible to evaluate IADs.