In farming, speed, efficiency and consistency are key to growth and success. This is especially true during the planting process as it pertains to seed depth which, today, is largely handled by hydraulic, pneumatic and mechanical downforce systems.
Some initial testing, however, is proving that another technology might be superior in its ability to control seed depth consistently and economically – electric variable dampers. Not only do these dampers represent a simple and less expensive alternative, but they are also proving to provide an exceptionally consistent seed depth in conditions with consistent soil types and where high-speed planting is desired.
Alternative electric force control
Researchers recently equipped a planter row unit with a smart electric damper.
The damper was used in combination with a vehicle speed sensor and a force feedback sensor. Both sensors were used to evaluate different methods for maintaining consistent seed trench depth. Springs or possibly an air bag could be used to provide an external force to maintain ground contact.
There are likely many ways to control a damper based on the amount of information available on modern crop planters. Speed and force measurements seemed to be the best place to begin evaluating an intelligent damping strategy, since these inputs are used in existing downforce applications.
How the damper works
Smart electric dampers (otherwise known as MR dampers) rely on Magneto-Rheological (MR) Fluid which consists of magnetic particles suspended in carrier fluid.
When a magnetic field is applied to MR fluid, it proportionally will change from a fluid to a semi-solid state in milliseconds, assuming the viscosity of the fluid is proportional to the magnetic field applied. This process allows the dampers to adjust resistance to movement.
The fluid passes through an annular orifice in the piston of a damper cylinder. An electric coil inside the piston creates the magnetic field necessary to change the viscous properties of the MR fluid dynamically based on electrical commands from a control system.
Today these dampers are already being used in suspension systems across many applications. It is believed that ground forces resist upward movement to maintain consistent seed depth similar to that of the downforce systems currently available on the market.
Field test results
Testing revealed the row unit with damper maintained more consistent and smoother trench control when compared to springs. Control of the damper using force feedback showed more influence on row stability when adjusting damper stiffness by indexing to vehicle speed.
While the results clearly demonstrated the superior performance of the dampers, the testing was limited by dry field conditions which meant that only a linear sensor could be used on the test row to judge trench consistency.
The relative movement of the damped row versus the non-damped row was evaluated to determine effectiveness. The damped row showed less movement which created consistent seed depth.
Study conclusions
Fields with consistent [Editor’s emphasis] soil conditions located where operators desire high-speed planting are likely the best fit for this technology.
The fixed springs used to maintain ground contact can be set to the desired force and damping. The electric dampers can adjust stiffness to resist upward force to maximize ground contact.
Vehicle speed could also be a valuable input to allow for speed and stiffness to be indexed. It is possible that only force input or speed, or a combination of both, could provide an optimum consistent seed depth, but more testing is needed.
Final Takeaway: Given the initial study results, it is likely some form of an electric damper system will be commercially available in the not-too-distant future.
A primer on seed depth technology
Over the past decade, significant advancements in planter and seeding technologies have enabled greater control of seed depth consistency. Hydraulic and pneumatic downforce technologies have been leading the way in consistent seed depth control. These technologies have allowed for faster planting, leading to greater productivity. They have also contributed to increased yield by enabling a uniform crop stand at time of harvest. This means a greater percentage of the crop reaches its point of harvest at the same time for more efficient harvesting.
Both hydraulic and pneumatic technologies act to provide down pressure that allows the cutting disks in the ground to maintain a prescribed depth. They have been proven to be reliable technologies when compared to springs. Some planter manufacturers have even completely phased out mechanical springs as a method for maintaining ground contact and seed depth.
Pneumatic systems are often associated with section control where air pressure is applied to a cylinder or air bag. This technology most commonly controls groups of rows or an entire machine to a common pressure. A unique, easily adjustable air pressure could be set for each field or crop.
Hydraulic systems are often associated with individual row control. Each row’s down pressure can be regulated based on force feedback sensors. The superior accuracy, reaction time and magnitude of force contribute to the positive market acceptance of hydraulic downforce in the market. Until now, a hydraulic downforce system has often been the preferred technology for maintaining seed depth.
While both hydraulic and pneumatic systems have clear performance advantages, they come with some drawbacks. Installation costs can be high due to the labor-intensive process of routing electrical, air and hydraulic lines. Plus, the potential for leak points (especially at fold and latching points) can be problematic. One of the leading hydraulic downforce systems on the market requires three hydraulic hoses to be run to each row. That means the number of connections for a 36-row machine, for example, could have well over 100 connection points.
