MECHATRONIC SYSTEM FOR CONTROLLING THE SEED DISPENSER AND VACUUM PRESSURE OF A PLANTER-FERTILIZER

Abstract

Seed dispensers of the seeders are components that largely determine the quality of planting; in general, these are driven by a mechanical transmission-drive wheel system, which has the drawback of being affected in its operation by soil conditions, vegetation cover and planting speed, which influence the sliding of the drive wheel or cause vibrations and blockages of the transmission system causing poor planting quality. The most advanced seeders use mechatronic systems that eliminate these problems. In the present work a mechatronic system was developed to control the rotation frequency of the seed disc and vacuum pressure of the seed dispenser, which was adapted and tested in a pneumatic seeder-fertilizer. The system is based on microcontrollers to manage planting density by changing the rotation frequency of the seed disk driven by a geared motor, using the Pulse-Width Modulator (PWM) technique and the Proportional-Integral-Derivative (PID) control. A similar method controls the vacuum pressure by means of a servo motor that adjusts the opening of a gate in the turbine suction line. With the developed system it was possible to reach the desired planting dose in approximately 1.5 s with a control error in steady state of ± 5 % at rotation frequencies of the seed disc of 21, 53 and 70 r/min and vacuum pressures of 1.5 to 4 kPa. At vacuum pressures of 5 kPa or seed disc rotation frequency of 37 r/min the error increases to ± 10 %, and for 5 r/min to ± 20 %. The vacuum pressure control error was ± 10 % for pressures from 1.5 to 5 kPa. An efficient mechatronic system was developed to control the pneumatic seed dosing system.