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The demand for increased performance of heavy earthmoving equipment has spurred the development of computer control for machinery using fluid power systems. Application of standard automatic control components to these systems provides the opportunity to implement advanced control approaches that reduce the operator workload and improve performance. In this work, closed-loop control is applied to the joints of a typical three-link digging device. Because the changing configuration of the device greatly changes the dynamic characteristics, an adaptive control algorithm is introduced to modify the control parameters to maintain consistent performance of the implement.

The differences between courses offered agricultural and mechanical engineers are examined. The topics in the courses are reviewed in some detail. The students start with a review of basic fluid mechanics followed by an introduction to bulk modulus. Governing equations for pumps motors and valves are introduced next. Course emphasis then diverges. The agricultural engineers cover the basics of control theory to cover a deficiency in their undergraduate curriculum. The mechanical engineers embark on more rigorous examination of the simulation of fluid power components. Students in both departments may elect to take a 1 cr. laboratory course. The laboratory exercises are discussed.

The success of agricultural and construction machinery owes a great deal to the effective use of fluid power. Most fluid power systems are configured with a positive displacement fluid pump that is large enough to meet the flow requirements of many work circuits. Different work functions require a variety of fluid flow and pressure values to provide the desired operation. System branches, therefore, must include specialized flow and pressure regulating valves. The development of a mathematical model of a fluid flow control valve follows.

An exploratory concept for a chassis suspension system for improving the operator ride comfort of an agricultural tractor is presented in this paper. The first section of the paper describes the criteria and concepts that have been incorporated into the design of a hybrid leading and trailing arm chassis suspension system. The second section of the paper discusses the evaluation of this suspension system and its parameters by simulating nine (9) different tractor and nine (9) different tractor-plow models, derived from the various combination of suspension configurations and operator cab locations. A generalized mechanical system simulation program is utilized to predict the dynamic linear transfer function behavior of each vehicle model. With frequency domain analysis techniques and the Fast Fourier Transform (FFT) algorithm, the dynamic vehicle response to the ISO 5007 Smooth Track excitation is computed.

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.

The purpose of this paper is to demonstrate a computer program developed for interactive optimization of dynamic systems represented by ordinary differential equations. The program is capable of minimizing a cost function with respect to from one to five design variables. The program is command driven with on line help and has interactive graphics capability for displaying output. Three vehicle dynamics examples are used to demonstrate the capabilities of the program, and in doing so reveal some interesting vehicle handling results.

Engineers and technicians have used mathematical analysis, in the design of fluid power machinery, for as long as this art has been known. As the machinery became more complex, analysis methods have had difficulty in meeting design needs. Some equation sets appropriate for fluid power devices are very difficult to solve with general mathematical methods. Electronic computers now make it possible to solve complex mathematical models. As fluid power analysis has evolved, software has been produced that is appropriate for fluid power analysis. The question then arises, as to how reliable and accurate this software may be. Some previous studies indicate that different types of software produce results that are quite similar in quality, however, quantitative answers may vary slightly (1, 2)*. This study compares the design analysis results for a fluid power attenuator obtained with the HYSAN** software and a previous study reported in the SAE Transactions (3).