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As more and more functions of agricultural tractors are automated to make farming operations faster and easier, designing efficient driver controls becomes more and more crucial. The French Institute of Agricultural and Environmental Engineering Research (CEMAGREF) and The Ecole Nationale Supérieure d'Arts et Métiers (ENSAM) developed a method to assess drivers' reaction to a new driver controls system including both a psychological and quantitative approach. A physiological approach was also considered, but could not be instrumented in the tractor-cab's environment. A group of eight farmers were used to test the method by evaluating a new automated control system on a tractor. This experiment pointed out that a good indicator of the driver's trust and understanding of the control system was given by the ability to imagine new ways or new conditions in which it could be used.

A vibrating digger blade with one input to move the blade horizontally and one input to move the rear of the blade vertically was tested to determine a mode of vibration that would produce the most effect on the soil at acceptable torque and power inputs. A kinematic and dynamic simulation program which accounted for the frictional and inertial effects of the moving parts of the machine and a block of soil on the blade was written and used to help decide which independent parameters and their levels to use in a field test program. The optimum combination of elements yielded by the study for use in a commercial digger design was an eccentricity of 9.52 mm for horizontal movement, an eccentricity of 12.7 mm for vertical movement, and an operating velocity ratio of 1.0.1

The evolution of an experimental prototype vibrating digger blade for harvesting root crops is described. The prototype had two independent oscillatory inputs, one to vibrate the whole blade horizontally and another to vibrate the rear edge vertically. It was to be used in later field experiments to determine the effect of changing directions of vibration on the dependent variables of draft, torque, and soil break-up. Torque measurements were made in the laboratory for eccentricities of 0.0, 9.53, and 12.70 mm and frequencies of 6.96, 9.28, 10.44, 13.92, 15.66, and 20.89 Hz, the range of these variables which would subsequently be used in field tests. The outputs of two computer simulation programs, one written by Rodriguez and a commercial software mechanisms analysis program, compared favorably with the measured laboratory results. 1

Vertical stiffness and damping coefficient values were measured, in non-rolling conditions, on eleven agricultural drive tires, with sizes ranging from 14.9-30 to 18.4-38, and both types of carcass construction, bias and radial, were tested. Tire stiffness was measured both in static and dynamic conditions. The mechanical model representing the tires was made of a parallel spring-and-damper system, simplified to a single spring in static conditions. Tire stiffness was linearly related to inflation pressure in all cases, but dynamic stiffness was higher than static stiffness. The use of different tire models for static and dynamic conditions is recommended during simulation and tire behavior prediction.

The purpose of this study was to analyse the dynamic behavior of a tractor driveline with respect to torsional vibrations in order to improve design procedures for transmission quality. A model of the transmission line was developed by CEMAGREF and ENSAM for the RENAULT 145-14 TX tractor. The model was tested by comparing the global torsional stiffness of the model to experimental measurements of the actual stiffness for different gears. Then, the natural frequencies of vibration of the model were determined and checked against the frequency of the vibrations generated by the engine to detect any detrimental coupling. The results of this investigation are presented in this paper.