1996-02-01

Verification of Vehicle Parameters for Use in Computer Simulation 960176

Input parameter verification is the most challenging aspect of the validation process of a computer simulation for a particular vehicle. Unreasonable parameters can arise from three sources, erroneous measurements (or bad guesses), misinterpretation of the parameter to be measured, and mistakes in data entry. Typical safeguards against the entry of unreasonable input parameters include careful checking and perhaps preprocessing input data through a graphical interface
This paper proposes an additional check procedure, namely, running the simulation through a recipe of maneuvers to determine metrics routinely associated with vehicle performance We refer to this kind of checking as simulation preprocessing
The methodology is computer controlled given the input data, the simulation preprocessor runs the simulation through the prescribed maneuvers and computes the metrics of interest In particular, the preprocessing begins with the calculation of cg position and overall inertial parameters, plus road wheel steer angles as a function of steering wheel at the trim condition. These calculations are based on a straight-running maneuver on a very slippery surface. For directional response measures, the preprocessor computes understeer gradient using constant steering wheel angle at increasing speeds, and roll angle, yaw rate, and lateral acceleration gains along with the yaw rate response time. For braking response, the preprocessor computes brake torque at each wheel as a function of brake application, and maximum wheels-unlocked deceleration on a dry surface
The paper also presents examples which illustrate the power of the methodology

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