DESIGN AND EVALUATION OF A CONTROLLER TO ACHIEVE OPTIMUM SEEDING RATE WITH SPECIFIC SPATIAL MANAGEMENT IN AGRICULTURAL MACHINERY
Achieving optimal seeding rates in different areas of the field is very important for maximizing crop yield. Nowadays, spatial management of croplands as a modern technology has been recommended in precision agriculture systems. Agricultural inputs such as seed, fertilizers, herbicides, etc., should be optimized with field conditions in different areas. For example, fertilizing and moisture should being compatible. Due to changes in these two factors, optimum seeding rates might being different in a field; areas with higher fertility or higher soil moisture have the higher seed rates. An applicable method to reach the ability of variable seeding rates in agricultural machines is to add controllers to the conventional fixed seeding rate seed drills. In the spatial management technology for seeding in a variable rate, first, the map of required seed for seeding practice is prepared for each particle of the field and then loaded in the machine at GIS format. The controller controls the seed rate continuously using the GIS map and the spatial position of the machine at field is provided by positioning systems. The aim of this study was to select the best closed-loop variable rate control system for Hassia seed drill shifting from a fixed rate to variable rate. To this end, Assessment of the performance of a control system that mounted on the seed dill and vary the rotational speed of the seed metering drive shaft performed. The control system was included a 250-watt DC engine, gearbox with constant gear ratio, two encoders (first for sensing the seed drill speed and second for sensing the rotational speed of the engine), position receiver and navigation, DC engine controller, and a portable computer for collecting data. The response time for transmitting seeding rate by the controller was determined from low to high 4/7 seconds and from high to low 2/5 seconds.