Balance and control of a rear-wheel steered speed-record recumbent bicycle

The goal of the Human Power Team from the TU Delft and the Free University of Amsterdam is to break the world speed record in unpaced cycling (Sam Whittingham, 133.28 km/h). The design of such a faired recumbent bicycle is a challenge. The Delft design, called VeloX (Human Power Team (2013)), is a fully-faired monocoque front-driven recumbent bicycle, with minimized air drag and maximized space for a big and strong athlete. However, front driven bicycles have the disadvantage that the front driving induces unwanted steering and that the frontal area of the bicycle cannot be reduced any further. A solution would be rear-wheel steering. A common thought is that a rear-wheel steered bicycle cannot be laterally self-stable, and therefore hard to control. However, recent research (Knoll et al. (2012)) has shown that one can design a rear-wheel steered bicycle which shows a stable forward speed range. Based on these results a rear-wheel steered recumbent bicycle has been designed, within the existing design constraints. Although not self-stable, this design shows a mildly lateral unstable behavior in the desired forward speed range of 0 to 40 m/s (0 to 144 km/h). Computer simulations demonstrate that the bicycle can be stabilized by adding a human controller model (Schwab et al. (2013)) to the bicycle model. For a set of expected lateral perturbations (side wind perturbations) it is shown that rider steer torque stays within human bounds, both in magnitude and in frequency. Future work is dedicated to building and testing a prototype of the design.