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The application of computer-aided engineering techniques to the design of off-road equipment reduces the development time and improves the performance and reliability. This paper discusses the applications of wireframe and solid geometric graphics techniques for the design engineering process (synthesis and analysis) of agricultureal equipment. From the illustrative examples, wireframe modeling best characterizes the design function of the mechanism or vehicle, while solid geometric modeling describes the best visualization of the machine and its component systems.

A modal analysis methodology is presented for multi-degree-of-freedom articulated machinery and vehicles. The analytical technique formulates the eigenvalue problem for linearized, constrained dynamical systems during steady-state motion or at a static equilibrium position. The technique is implemented into a computer simulation program to compute the system modal properties. The system eigenvalues and eigenvectors are combined with the system geometrical transformation data to yield the system transfer function ratios for the generalized coordinates and points of interest, as well as the mode shapes. In turn, the frequency response magnitudes and phase angle shifts for a specified frequency range are computed from the system transfer functions.

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.

A rigid/flexible multi-link mechanism simulation methodology is discussed for off-highway machinery applications. This formulation combines nonlinear large displacement dynamics with elastic structural dynamics effects. The first part of the paper briefly discusses the mathematical formulation (i.e., the 4 x 4 transformation methodology) while the second part discusses the application of the methodology. The rigid/flexible multi-link simulation methodology is used to model the dynamic response of a stiffness-sensitive loader linkage. The simulation results for the loader model are compared with the results of finite element analysis (i.e., normal mode, harmonic force and linear transient analyses).

Computer simulation modelling techniques are basic engineering tools to investigate and predict the performance and mobility of agricultural tractors. Analytical methodologies developed by researchers to simulate and evaluate the terrain-operator-agricultural vehicle system and its subsystems are described. The techniques are classified as models and methods describing the subsystem interactions and relationships and the overall tractor-soil-implement system. The subsystem models and methods include: soil mechanics) the soil-wheel interactions, the soil-track interactions, the vehicle mechanics relationships, the soil-implement interactions, and the power train and hitching relationships. These models and methods were developed by various researchers as a means to optimize the tractive performance of the tractor by parameter sensitivity analyses.

An analytical study of the dynamic behavior of agricultural tractor-trailer combinations is conducted to investigate the stability and handling characteristics. Equations of motion reflecting the characteristics and parameters of the combination in terms of stability and handling are developed. The influence of changing the combination operating and design parameters on the lateral stability of the system is investigated with an eigenvalue analysis technique and a time-domain integration technique. The simulation results showed that forward speed of the combination and the properties of the trailer substantially affect the lateral stability of the tractor-trailer combination.

A kinematic model for studying the maneuverability of an off-road tractor/double-axle trailer combination has been formulated. The influence of steering inputs from the tractor and the trailer front axles on the system's maneuverability in terms of lateral displacement and rotational motion during the turning process is studied by conducting computer simulations using the LOTUS spreadsheet program. A lane-change problem is presented to demonstrate the computational procedure and to illustrate the application of the kinematic model.