Simulation and parameter sensitivity studies of skid-steering and Ackerman steering on an eight-wheeled vehicle

A three degree of freedom vehicle dynamics model that includes longitudinal and lateral tire force models is described, including its implementation into the Matlab/Simulink simulation environment. The tire force models account for the effect of longitudinal slip as well as lateral slip angles, and the force characteristics are assumed to take the form commonly found for hard surface (non-deformable terrain) applications. The baseline model was developed for an eight-wheeled platform, and the model allows for simulation of either Ackerman or skid-steered configurations. A simple driver model is integrated with the vehicle model and allows control of the velocity and heading of the vehicle. Several common vehicle maneuvers including straight-line motion, constant radius turn, oval racetrack, and lane change are used to verify the model capability. The model was used to compare energy consumption of an Ackerman-steered vehicle and a skid-steered vehicle for the maneuvers described above. It was verified that skid steering consumed more energy than Ackerman steering for all maneuvers except for the straight-line maneuver. In addition, the model was used to examine the effects of varying several vehicle design parameters on energy consumption. The specific parameters analyzed include vehicle mass, aspect ratio, number of wheels, longitudinal weight distribution, and roll weight distribution. Results from this parameter sensitivity study can be used to make important design decisions early in the design cycle for eight-wheeled vehicles and other similar applications.