Development of an Intermediate DOF Vehicle Dynamics Model for Optimal Design Studies

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Title: Development of an Intermediate DOF Vehicle Dynamics Model for Optimal Design Studies
Author: Lowndes, Erik M
Advisors: Joseph W David, Chair
C Tim Kelley, Committee Member, Member
Larry M Silverberg, Committee Member, Member
John S Strenkowski, Committee Member, Member
Abstract: The demands imposed by the optimal design process form a unique set of criteriafor the development of a computational model for vehicle simulation. Due to the largenumber of simulations that must be performed to obtain an optimized design the modelmust be computationally efficient. A competing criterion is that the computational modelmust realistically model the vehicle.Current trends in vehicle simulation codes have tackled the problem of realism byconstructing elaborate full vehicle models containing dozens if not hundreds of distinctbodies. Each body in a model of this type is associated with six degrees of freedom.Numerous constraint equations are applied to the bodies to represent the physicalconnections. While the formulation of the equations is not particularly difficult, and in facthas been automated in several software packages, the resulting model requires aconsiderable amount of computational time to run. This makes the model unsuitable forthe application of computational optimal design techniques.Past research in the field of vehicle dynamics has produced numerouscomputational models which are small enough and fast enough to satisfy the speeddemands of the optimal design process. These models typically use less than a dozendegrees of freedom to model the vehicle. They do a good job of predicting the generalmotion of the vehicle and they are useful as design tools but they lack the accuracyrequired for optimal design.A model that bridges the gap between these two existing classes of models and issuitable for performing optimal design was developed. The model possesses twenty-eightdegrees of freedom and consists of eight bodies which represent the sprung mass, the rearsuspension, the left front spindle, the right front spindle, and the four wheels. A drivercontrol algorithm was developed which is capable of driving the car near its handlinglimits. The NCSU Legends race car was modeled and an attempt was made to optimizethe vehicle setup for the Kenley, NC race track.
Date: 1998-10-26
Degree: PhD
Discipline: Mechanical Engineering

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