Experimental Research on Stability of an Off-Road Vehicle on Deformable Surfaces

The paper describes a field experiment on the lateral dynamics of a light sport utility vehicle (SUV), driven over two different deformable surfaces (sand and loess). The vehicle was equipped with a steering robot, four wheel dynamometers, and a differential global positioning system (DGPS). The main purpose of this study was to determine (1) tire lateral forces on steered wheels of the vehicle and (2) vehicle response to two different methods for the steering angle excitation: a sine wave and a ramp change. The steering robot installed in the vehicle allowed us to perform tests with various parameters (sine wave at 0.5, 1.0 and 2.5 Hz, ramp change at 100, 500 and 1500 deg/s) and to repeat the tests as needed for further analysis of the data (the so called “open loop”). During the tests, wheel forces were measured by two wheel dynamometers installed on the front (steered) wheels, and vehicle dynamic response was sensed by the DGPS, working at 0.01 s acquisition time that achieved a resolution of vehicle horizontal position of 20 mm. The vehicle was (1) pulled by a heavier tractor-vehicle to ensure a straight linear course, (2) freely driven, with the vehicle responding to steering inputs. Presented results include side force at various excitation parameters for both pulled and freely driven tests and data from the DGPS: lateral acceleration, yaw rate and side slip angle of the vehicle.