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Data envelopment analysis (DEA) is used to examine the efficiency of 74 front wheel assist agricultural tractors from three U.S. manufacturers. The outputs of drawbar horsepower and power takeoff horsepower are modeled in a constant returns-to-scale framework using three productive performance inputs (fuel consumption, slip, and center of gravity), and one price input, namely, retail tractor price. The results suggest that by and large, John Deere tractors are more DEA efficient than their competitor's tractors. However, competitor's tractors that are DEA efficient are most often the top benchmarks for DEA inefficient tractors. These results suggest that while John Deere appears to produce many quality tractors, competitor's like CNH and AGCO produce a few tractors that may be of even higher quality.

Applications of active suspension control for both on-highway and off-highway vehicles are reviewed. Suspension design is evaluated in terms of ride vibration exposure and road/terrain handling. Active, semi-active, and slow-active suspension types are described in terms of their performance capabilities. Finally, numerous design concepts and their application to a wide range of ground vehicle types (i.e, truck, automotive, agricultural, and construction) are described.

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.

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.

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.

The purpose of this paper is to describe and demonstrate a computer program to interactively design roller-chain and synchronous-belt drives. The program allows the user to optimize the power-transmission drive system and has graphics capability to assist in design visualization. The paper discusses the analysis procedure, design criteria, and the program data base. The analysis procedure and design criteria are based on accepted methodology by the roller-chain and synchronous-belt manufacturers. Governing equations and flow charts are included in the discussion, and three examples are presented to demonstrate the program capabilities and features.

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.