Communication Protocols for Application in Agricultural Vehicles

The use of electronic and computer systems for monitoring and control of agricultural machines, equipment, facilities and processes, and for the management of farms and agricultural companies has played a key role for the achievement of new and better standards in world agriculture. Besides increasing productivity, other objectives are decreasing the losses, rationally using the inputs, and protecting the environment. The advances in electronics have contributed to the great reduction in cost and price of equipment, at the same time that they have increased performance and reliability. The agricultural machines industry has been incorporating electronics to their products with the aim of providing more information to the operator about machine performance; registering that information for future analysis; automatically controlling the machines, freeing operator attention to other tasks, optimizing the use of the machine and avoiding unnecessary wear; and optimizing the use of inputs. Classical examples of those systems are on-board computers for tractors, which monitor variables of the engine, transmission and slip, in order to inform the operator or to control them automatically. Nowadays many machines and implements, such as combines (harvesters), planters and sprayers have monitoring and/or control systems which compensate the influence of the variation of true ground speed on the actual application rate of inputs (such as fertilizers or herbicides) or on the rate of harvesting. In order to do that, those machines need many different sensors and actuators, and a great amount of data must be processed and stored. Recently, with the new paradigm of precision agriculture, the use of embedded electronic systems in agricultural machines has significantly increased. Precision agriculture is a new management approach based on the fact that within the usual field management unit there can be a lot of variability in soil parameters, in the crop stand and in other agents such as pests and diseases, which can help explain (and eventually help compensate or correct) the yield variability within that field. The goals of this new paradigm are: to apply the inputs at variable rate within the field, each point receiving only what is effectively necessary (as opposed to a homogeneous application); to optimize the use of inputs, improving the cost/benefit ratio; to decrease the excess of inputs and the environmental impact of agriculture (Saraiva; Cugnasca, 1998). Precision agriculture is strongly based on automation, as it depends heavily on electronic data acquisition systems, on accurate positioning systems in the field (such as the Global Positioning System — GPS), and on variable rate application controllers. A great number of such systems and devices have been proposed for different field operations and parameters.