Autonomous Tractor Suitability
Craig Rupp, CEO of Sabanto and a pioneer in autonomous farming, shares his perspective on the practical realities of autonomy in agriculture. As one of the first to operate a fleet of autonomous tractors, Rupp offers unique insights into why a standard autonomous tractor may often be more effective than a dedicated field robot. In this series of bi-weekly opinion pieces, he explores the reality of autonomous farming and what it could mean for farmers today.
We’ve retrofitted over 20 tractor models from 6 OEMs, ranging from sub-60 HP to 400+ HP. It takes between 1 to 3 months for us to add another make and model. Along the way, we’ve learned what works for autonomy – and what doesn’t.
Some tractors make retrofitting seamless, while others fight you at every step. It often comes down to transmission, brakes, and steering. And despite what OEMs might say, new isn’t always better. Many used tractors are ideal platforms for autonomy. So, what should farmers look for? Let’s break it down.
The Right Tractor
Sadly, not every tractor can be easily retrofitted for autonomy. For the most part, we look at three things when evaluating candidates: the transmission, brakes, and steering.
Transmission
If you’re tractor has a manual transmission (synchromesh or unsynchronized), we always pass on it. It would require a feat of engineering to control the clutch and gearshift. A shuttle transmission is the minimum we’ll even consider. An electronic shuttle is even better. The infinitely variable transmission (IVT) is king because life gets a lot easier not having to worry about the gear selection to keep the RPM in a certain range for the PTO.
Brakes
Retrofitting autonomy means you need a safe, reliable braking system. We’ve encountered two types of braking solutions on the tractors we have automated: actuators and air valves.
If your tractor has conventional hydraulic brakes, our game plan is always resorting to using an electromechanical actuator to press the braking system and engage the hydraulic system. It is more invasive, requiring precise mounting and calibration.
We’ve found Fendt tractors have the ideal brake system for autonomy – air brakes. We control the existing air brake system by regulating air pressure with an electrically controlled air valve. This solution is simple by tapping into the air brake system with minimal modification and then smoothly modulating the braking.
Steering
Steering is the last critical piece of the autonomy puzzle. It always comes down to whether a tractor is auto-steer enabled. If it’s not, we resort to either an off-the-shelf hydraulic valve or steering wheel motor.
Our hydraulic system consists of a proportional valve, working with both closed and open-hydraulic systems. This solution directly controls the hydraulic pressure to the steering cylinders. We simply use pulse width modulation to adjust the proportional valve giving smoother adjustments, lower latency, and better response. The drawbacks are the installation and higher cost. Installation can be a nightmare. For example, try mounting a hydraulic valve on a Kubota with loader brackets.
The steering wheel motor is designed to mount directly onto the existing steering wheel of the tractor. Unlike the older on/off motors, newer generation solutions now allow variable steering adjustments, improving accuracy and reducing overcorrection. Those newer generation ones are typically CAN controlled. The drawbacks are the longevity as compared to the hydraulic system.
New vs. Used
When it comes to autonomy, the decision between new and used tractors isn’t just about cost, it’s about practicality, compatibility, and long-term value.
New Tractors
OEMs would surely love for you to buy a new tractor that was “autonomous ready”. But let’s be honest, most farmers aren’t rushing to drop hundreds of thousands of dollars on a new machine just to gain autonomy in this market. This “buy new” mindset is planned obsolescence, the practice of designing products with a limited lifespan so they become outdated or non-functional after a certain period, pushing farmers to replace them. I talked with a farmer last week that swore newer tractors are incapable of getting the same hours as those bought 20 years ago.
Used Tractors
For practically all the farmers we call customers, autonomy isn’t about starting fresh, it’s always about getting more out of what they already own – their used tractor. Although older tractors may be cheaper, their engine, hydraulics, and transmission could have reduced lifespans. Nonetheless, their justification always follows the same line of thinking:
- Implement Matched – My tractor is matched to my implements, field conditions, and workflow. Swapping it out for something new often means adjusting everything else, which adds cost and hassle.
- Proven tractor – I already know my tractor inside and out. Why not use something that has ran in my fields, with my implements, under my conditions?
- Leverage existing capital – My tractor is already paid for. Why not make it autonomous instead of buying a new one?
Still, some of our customers resorted to buying used tractors to lessen their capital outlay given the crowd of low-hour candidates in the market – tractors being the most widespread, underutilized capital there ever was. I usually try to convince them to forgo the 25% upcharge for a cab for one particular reason – the heat. Given no operator, no open windows, and no AC, an operating tractor’s cab gets exceedingly hot in Texas.
The Bottom Line
Most modern tractors, large or compact, can be retrofitted for autonomy. The key isn’t just buying new but choosing the right platform for a seamless retrofit. Farmers who upgrade their existing tractors get more value, avoid unnecessary costs, and keep using equipment they already trust.
Autonomy isn’t about replacing tractors – it’s about making them smarter.
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