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Linear analysis and corresponding vehicle tests have been used since the late 1950's to help understand the directional response of automobiles and commercial vehicles. This work is now well accepted, and linear terms such as understeer gradient and response time are descriptors routinely used to characterize vehicle performance in the linear range. This paper assesses the use of various levels of complexity in linear models. It verifies that, for steady state measures such as understeer gradient, all important effects can be handled quasistatically and a two degree of freedom model is adequate. The paper then illustrates situations in which the roll degree of freedom can be important for transient calculations, and assesses the changes in calculated transient results deriving from the addition to the model of time lags in lateral tire force buildup.

An analysis has been conducted on the hydrostatic drive system for driving a soil bin. A comparison of the bin velocity was made between the pure inertia load and inertia plus disturbance. Also, the pressure fluctuations that are predicted are quite sensitive to the leakage values chosen. A low leakage value predicts an oscillatory pressure response. Although no feedback was employed for the velocity output, the load disturbance changed the output velocity very little.

This paper examines the validation process for computer simulations of ground vehicle dynamics. Validation in this context may be defined as the process of gaining confidence that the calculations yield useful insights into the behavior of the simulated vehicle. It is our view that this process requires three separate questions to be addressed: Is the model appropriate for the vehicle and maneuver of interest? Is the simulation based on equations that faithfully replicate the model? Are the input parameters reasonable? This paper addresses each of these questions, mainly from an analytical point of view. The paper then addresses strengths and weaknesses of vehicle testing as part of the validation process.

European and American suspension systems are described for improving the operator ride comfort on off-road vehicles. Analytical methods are then described to predict the dynamic behavior of a vehicle and human ride response criteria. The approach includes the selection of a terrain input to excite the vehicle model formulated by the generalized mechanical system simulation programs. An example involving an agricultural tractor-plow system is presented to illustrate the techniques.

Pressure waves in hydraulic systems can cause control valves to become un-stable during operation and also contribute to vibration and noise. These undesirable pulses must be filter-filtered out or at least reduced in magnitude, in order to optimize the performance of fluid power systems and their controls. Reduction in pressure wave amplitude also reduces wear and damage to system parts [13].* The fluid pump is usually the primary source of pressure pulsations. These waves travel throughout the fluid system. Therefore, it becomes advantageous to reduce the amplitude of the pressure waves as close to the source as possible [16]. A method of reducing the pressure waves by use of a carefully selected volume in the flow line is described. A successful mathematical means of sizing the desired attenuator volume is outlined. The mathematical model can be used with any computer simulation program. Some of these are mentioned by Bowns and others [1,2,3,4,5,6,7,18,19].

Both tilt table testing and the calculation of so-called Critical Sliding Velocity (CSV) have the goal of determining conditions wherein a vehicle can be tripped by sideways impact with an obstacle and roll exactly one-quarter turn. This paper first reviews the mechanics associated with each of these metrics, verifying that (i) the tangent of the measured tilt table angle can be expected to yield a metric less than but closely related to T/2h, and (ii) CSV calculations are by and large dependent only on the vehicle's calculated cg height h and the ratio T/2h. The paper then addresses what we view to be an important related issue: How well do the mechanics of these measures and/or calculations carry over to calculations related to incidents which include more than one-quarter turn? We approach this question by extending the derivation of the CSV calculation to compute initial sideways velocities V2 needed to initiate a tripped roll of more than one-quarter turn.