Self steering implements, considered an oddity 20 years ago, started attracting serious attention four years ago. Today, they are reality.
Although the big product announcements always come from major manufacturers, both types of self-steer technology now on the market were born in Saskatchewan.
Farmers may remember the self-steering John Deere 4020 that University of Regina engineer Ron Palmer demonstrated in 1985. It used a worm gear electric motor from an automotive power window mechanism.
Instead of making a window go up and down, it was mounted sideways so it pushed left and right against a lever attached to the tractor steering wheel.
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Directional input came from an on-board controller that received digital locating signals beaming in from towers around the field. The device was designed to show that electronic signals could safely control the path of a farm implement. The 1985 demo could even turn itself around at the end of each pass.
In the summer of 1999, Palmer refined his beacon guidance autosteer project and experimented with a Wilmar sprayer on the Pattison farm near Lemberg, Sask.
He had tapped into the light bar guidance unit and was getting what he calls strong gee and haw signals for steering. Although he considered plumbing the experimental control directly into the hydraulic steering, he was hesitant because of implement warranty implications for new machines.
“All the way back to the early 1990s, we had been agonizing over the question of a rubber puck turning the actual steering wheel versus cutting into the hydraulic steering for a true electric-over-hydraulic system,” Palmer said.
“I was leaning toward the simple method of using the rubber puck because it was adaptable to any vehicle that has a steering wheel.”
Larry Pattison remembers that day in 1999.
“Ron had a reversible electric screwdriver attached to a hockey puck turning the steering wheel. It kind of worked, but it was awkward. I told him I didn’t think farmers would want something like that attached to their steering wheels.
“I figured that if he’s already succeeded at sending quality steering messages to the screwdriver, why not instead send them to a solenoid and let the solenoid do the steering in the hydraulic system?
“Ron said that, yes, we could do that, so we scrounged up a valve. A half-day later we had automated steering using the Wilmar steering hydraulics.”
Palmer also remembers the day.
“I told Larry that it’s his sprayer, and maybe he doesn’t want to screw it up by splicing anything into the steering hydraulics. He went ahead anyway.
We chained one of the booms up and he took off the two-way valve and within a matter of hours, he had it plumbed into the steering system and we had the self-guided sprayer.
“The rubber puck had been working for me OK, but not really good. I’d get on a side hill and it would slip. It didn’t give me the nice firm control you need for steering. I wasn’t really satisfied with it.”
When they first installed the boom valve into the steering system, it allowed too much oil flow and the steering jerked badly when the controller sent signals.
“It was rated at 12 gallons per minute,” Pattison said.
“For straight line steering down the field, we only need about one gpm, so we metered it down with restrictors. The valve itself is nothing special, just a simple open-centre, two-way valve for a double-acting cylinder.
“We had a pressure end return to the tank and an AB port going to the rams. Ron’s controller sends the signal down to the 12 volt solenoid and that activates the valve one way or the other. The flow goes left or right. But for actual turning or to do contours, I think you’d need more flow.”
Sub-inch accuracy was a concern.
“I don’t know if a simple two-way valve can handle it,” Pattison said.
“You’d probably need a proportional valve for sub-inch accuracy or for actually turning at the end of a row. The tricky part is the electronic signal. You’re sending a signal down to the solenoid to activate the valve five times per second.”
Pattison said many people with self-guided steering systems blame their equipment when they can’t get desired accuracy.
It’s usually not the equipment, he added, but the guidance signal that determines the accuracy.
“If you go with a free GPS signal, then your accuracy is one foot,” Pattison said.
“If you pay to get a subscription, then you’re at four to six inches. If you want sub-inch, you need more expensive equipment.”
Palmer said safety is not an issue because with such a low flow rate, it only takes a hand on the steering wheel to take over manual control.
“It takes very little hand pressure to override the guidance system. You make your turn at the end of the field, pick a new row, let go of the wheel and the GPS just sucks you right back into the next line.”
Were Palmer and Pattison really the first to make autosteer work?
“Nobody knows for sure because there’s always so much development work going on around the world and you can’t keep track of it all,” Palmer said.
“But what we do know for sure is that we’ve never heard of anyone anywhere doing this before we did.”
