One man takes control of 16 driverless tractors

A tractor that looks nothing like a tractor and doesn’t need a driver? It’s got a touch of the April Fools about it, but the Spirit could be about to challenge the Germans in the tractor technology stakes.

It might look like the lovechild of a Land Rover Mk I and First World War tank, but 25 of them will be crawling out of the Fargo, North Dakota, factory for testing on US farms this year.

Who makes it?

Two brainy, American-based groups have teamed up to design the Spirit – the Autonomous Tractor Corporation and the Automation Research Group.

How does it look?

Who says a tractor needs to have big wheels at the back, little ones at the front and a cab somewhere in between?

“No one has re-thought the ag tractor from the bottom up in probably 80 years,” says Dr LeRoy Anderson, a software developer at ATC. “Currently available equipment has tried to meet the needs of farmers by incremental innovation over many decades. The result is giant machines that are prohibitively expensive, inefficient and difficult to transport.”

Spirit-Autonomous-Tractor-x4

The tractor either directs itself or is in follow-my-leader mode, so the cab is pretty much redundant. Instead, the motors, fuel and ballast tanks are perched on 25in rubber tracks with hydraulic tensioners.

Tracks are a must since the Spirit tips the scales at 13.6t fully ballasted (the ballast tank itself can be topped up with 2.3t of water).

How does it work?

Two four-pot, 5.2-litre Isuzu motors supply the muscle. Both 202hp engines power generators, which in turn provide power to four oil-cooled electric wheel motors.

Top speed of the crankshaft is 1,800rpm and a cavernous 2,360-litre fuel tank stores enough juice to keep the Spirit running for 36 hours solid.

Because it’s diesel-electric there’s no need for a transmission, differentials or axles. That saves a few pennies in the build budget and cuts the number of moving parts that need maintaining.

With routine servicing, ATC reckons the Spirit’s usual life is up to 25,000 hours and the 500-hour service interval is about equal with a standard tractor.

Who controls it?

Come harvest there’s no need to leave the work to some sleepy work experience kids. One person, either at a base station or with a portable controller, can take charge of up to 16 tractors spread across fields 25 miles away. It can also be set in semi-autonomous following mode where it trails a controller (who can be sat in a pickup, for instance).

How does it avoid obstacles?

Here’s the clever part. The Spirit uses a combination of computers, lasers and radio signals to keep it on the straight and narrow. GPS satellite-based navigation is a no-go because it has a tendancy to fade and lose signal.

Instead, two lasers ping signals to and from transponders dotted around the field. 150MHz radios are also used to overcome line-of-sight issues with the lasers.

What about implements?

You can have a standard three-point linkage on the back. Beefy 227 litres/min hydraulics are available and as many as 12 spools can be plumbed in.

What does it cost?

Suprisingly little. It’s about $500/hp (about £315/hp), which includes the laser radio set-up to stop the tractor straying from the fields. So for $100,000 (£63,000) you can potentially get yourself a 200hp tractor, 24-hour farming and a lot of free time.

Spec

  • Engine four-cyl, 5.2-litre Isuzu
  • Power 202hp
  • Top speed 18mph
  • Hydraulics 227-litres/min
  • Weight 13.6t
  • Service interval 500 hours
  • Distance you can control 25 miles
  • Number of tractors controllable 16 tractors
  • Cost $500/hp

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