A real-time hardware-in-the-loop vehicle simulator

Off-Road Environment Simulator (ORES) is a realtime Hardware-in-the-Loop (HIL) platform to simulate the dynamic characteristics of off-road vehicles. This paper focuses on the model development and validation of an All-Wheel-Drive (AWD) vehicle on the ORES test rig. Off-road vehicles primarily operate on bumpy terrains and are subjected to different ground excitations. This results in non-unique resistive wheel torques because of differences in ground friction conditions and wheel loads. If engine torque is not distributed in accordance with resistive wheel torques, it may lead to transmission windup resulting in failure of various driveline components. The purpose of this platform is to reduce transmission development time by replacing field trials with lab testing. The vehicle is driven over a rectangular bump in rig simulation. For these discontinuous short-wavelength ground excitations, terrain enveloping plays a significant role in determining effective ground excitation. An effective terrain profile is obtained using a two-point follower technique. These ground excitations are given as inputs to a detailed seven degree of freedom vehicle ride model which calculates the wheel loads. The ride model is then integrated with longitudinal dynamics, tire, driveline and test-rig models. Vehicle axle acceleration, wheel speed and drive torque responses are measured for validating the simulation results against rig trials. The match is fairly well which validates the suitability of the proposed modeling approach.