Method of simulating the performance of a vehicle on a road surface

A method of simulating the performance of a vehicle on a road surface on a power train test bed by means of torque-controlled electric load machines mounted on shafts of a power train of the vehicle and by means of a computer forming a feedback control system with a torque-controlled electric load machine mounted on at least one of said shafts for providing a setpoint torque value for said at least one torque-controlled electric load machine,

• the method comprising the following steps:
• a) storing within said computer
• a tire model providing values of a coefficient of friction as a function of slip of a tire for determining a slip-dependent friction of the tire on the road surface, and
• a vehicle model for calculating a velocity of said vehicle and a normal force at the tire,
• b) measuring an angular wheel speed on said at least one shaft,
• c) determining a force transferred from the tire to the road surface at the measured angular wheel speed using the tire normal force provided by the vehicle model and a slip-dependent friction of the tire provided by the tire model using a value of the coefficient of friction for a slip of the tire occurring between the measured angular wheel speed and a nominal angular wheel speed which corresponds to the calculated vehicle velocity provided by the vehicle model,
• d) determining a setpoint torque value for the torque-controlled load machine mounted on the at least one shaft at said measured angular wheel speed value using the vehicle velocity provided by the vehicle model and the tire normal force and the slip-dependent friction of the tire determined in step c),
• e) feeding back the force transferred from the tire to the road as determined in step c) from the tire model into the vehicle model to be used in the vehicle model for recalculating the vehicle velocity,
• f) reentering the value of the vehicle velocity recalculated in step e) into the tire model, and
• g) repeating steps b) to d) to recalculate the setpoint torque value for the torque-controlled load machine mounted on the at least one shaft.