Modern agricultural tractors contain so much cutting-edge technology, they rival even the latest spacecraft. But the back end is still old-school, relying largely on fossil fuels. So, any optimization in tractor efficiency is a huge win for the environment.
With this in mind, Purdue University researchers have undertaken a Department of Energy project to optimize the hydraulic systems that connect tractors and implements. Tractors use fluid power to actuate everything from the steering and propulsion; to powering the implements it pulls behind them.
Powering the implements has proven to be a problem, however. The hydraulic control system of the tractor has shown only 20 percent efficiency when connected to the hydraulic systems of certain implements like planters, seeders, and bailers. “There’s a conflict in the controls, where the two systems are almost fighting each other,” said Patrick Stump, a Ph.D. student in mechanical engineering. “As a result, when it’s connected to a planter, the tractor always has to run at extremely high power, which wastes fuel and increases emissions.”
The researchers focused on a particular tractor-planter combo. The planter is 40 feet wide, with 16 planting rows. Each row has multiple machines working together to plant the seed. There’s a cleaning wheel in front to remove existing vegetation; a cutting disc cuts a tiny ditch in the ground; a motor drives the seeds into the ground; a sprayer feeds water and fertilizer into the hole; then a final disc covers the hole. There are 16 of these planting rows, which need specific amounts of pressure to successfully plant the seeds. And all of them are powered by a single hydraulic system.
To tackle the problem of optimizing this tractor-planter combo, the team chose a three-phase approach. First, they needed to characterize the hydraulic system and build a computer simulation model. They started by modeling individual components and testing them in a stationary condition in the lab. They then combined the component models into a system and tested the system to verify that the entire model is valid. Once they had validated their model, the researchers moved to phase two: developing solutions they could test.
“Different planting conditions require different amounts of pressure and flow rate. If the model shows promising improvements in power and efficiency, then we can begin to implement these changes under real-world conditions,” said Ph.D. student Xin Tian.
For the third phase — real-world tests — the team outfitted the tractor-planter combo with a myriad of sensors in order to measure how much power the tractor is consuming, what the hydraulic pumps are doing, and what the pressure and flow rates are throughout the planter. The sensors were wired into a data acquisition box installed in the cab in order to provide a full picture of what happens during a planting cycle.
The team conducted several runs in the spring of 2021, where they planted corn seeds at different pre-determined engine speeds and planting rates. Combing through the data, they found that their new hydraulic control systems translated into an overall 25% efficiency increase. “Given the amount of fuel that a typical tractor consumes, that’s a massive improvement,” said Professor Andrea Vacca. “And this is only the beginning. Our project goal is to double the efficiency of the overall hydraulic control system. In the future, we plan on instituting a pressure control approach for the control logic, which has never been attempted in agricultural vehicles.”