Development and Utilization of a Planter Automatic Downforce Evaluation Test Stand to quantify System Response and Accuracy

摘要

In recent years, newer precision planters have seen integration of automatically controlled row unit downforce systems to reduce soil compaction, maintain proper seeding depth and control row unit ride quality. By keeping planter row unit downforce properly applied, a more uniform emergence and increased yield potential can be obtained. However, little knowledge exists to understand downforce system response and accuracy during scenarios typically occuring during field operation. Therefore, the study was conducted with two key objectives to study were to 1) develop a lab-based test stand to evaluate downforce system response time, accuracy, and downforce load distribution between the gage wheels, opening discs, and closing wheels; and 2) evaluate an automatic downforce system using test stand under simulated real-field scenarios. A downforce system test stand was designed with the capabilities of changing row unit vertical travel as well as load distributions between the planter row unit's gage wheels, opening discs, and closing wheels. The test stand was developed after assessing field operation of a planter with automatic downforce system operated on multiple fields. Simulation scenario were developed to 1) operate planter at varying speeds with uniform soil type and moisture; and 2) operate on soil with varying resistance due to texture and/or moisture changes. Real-time field data was used to develop simulation test files with target disc loading conditions. A custom LabVIEW program was developed to operate the downforce test stand's pneumatic valves and record data from the test stand and row unit sensors using a National Instruments (NI) CRio Chassis. The LabVIEW program could also read control commands from *.txt file, henceforth referred to as a simulation file, to actuate desired disc loads through the disc loading mechanism and platform height through the platform height control mechanism. The program would read the simulation file containing target values of disc load and platform height, parse the data fields and send it corresponding control loops. The control loops would used the simulation file data as a target load or distance height setting while reading pressure transducer and ultrasonic sensor data for current load of the disc cylinder and current height of the test stand, respectively. A National Instruments cRIO Chassis and C series modules were used to control the test stand and record data from the test stand at 10 Hz. Results from different scenarios exhibited that the test planter's automatic downforce control system maintained the target gauge wheel load setting of 38 kgf ±- 22.7 kgf for more than 94% of the time. The downforce control system was able to manage gauge wheel load with disc load variations up to 68 kgf within 1.3 sec and load variation upto 22 kgf within 0.5 sec. Overall, the planter downforce control system ability to maintain target gauge wheel loads at varying speeds and soil texture variation within 0.5 to 1.3 s suggested appropriate control for precision planter.