Platoons - Physical Simulation
To correctly simulate platoons travelling at typical road speeds, model vehicles are mounted on a long spine running through a slot in a suspended ground plane and propelled at 25 m/s (55.9 mph). The models are box type lorries and Windsor cars at scales of 1/20th and 1/10th respectively. A number of spacings, suitable for the application of autonomous road vehicles, between 0.5 and 1.5 vehicle lengths are examined.
Twelve multi-hole pressure probes, above and to the side of the vehicles, monitor the development of slipstream velocities and static pressure. This is important in understanding the influence the passing vehicles have on other road users (motorcyclists), roadside workers and pedestrians. A series of light gates on opposing sides of the track allow accurate calculation of the vehicle speed and assist in aligning data from each run with respect to a fixed position runs so ensemble averages can be calculated.
Novel on-board pressure monitoring systems are built into all vehicles to monitor the transient pressure distribution development on the vehicle surfaces. Transient and mean forces are calculated through integration of the pressure over a discretised geometry of the vehicle surface. These forces can be scaled up to estimate the forces on full-scale vehicles through aerodynamic load cofficients. This is important because transient loads on the vehicle sides may effect vehicle handling whilst the mean drag may effect fuel consumption and CO2 emissions.