2006 Volume 68 Issue 1 Pages 51-60
Driving forces and side forces of off-highway block tires on a slippery gravel road were measured using a measurement system developed. This system uses a direct-coupled four-wheel-drive apparatus that is towed with constant speed from a towing point located away from its axis of symmetry. In order to promote the application of the tire characteristics measured, the coefficient of driving forces and the coefficient of side forces were approximated to be polynomials using the slippage and side-slip angle. Further, to investigate the basic principle of the measurement system, the equation of motion for the four-wheel-drive apparatus was linearized to a numeric model with one degree of freedom. Using the numeric model, the local stability of the four-wheel-drive apparatus around the position of equilibrium was confirmed analytically for the successful measurement experiments. In the experiments, where the towed point angle exceeded 90 degrees, the measurement system did not converge to equilibrium. This phenomenon also was confirmed with the holomorphic analysis using the numeric model with one degree of freedom.
