Assistance with GPS Speed Solution

Maybe you need greater accuracy? level graders used lasers for reference. Perhaps a mixture of laser triangulation and GPS?

To be clear: the GPS speed sensor most certainly works, if I drive the tractor above about 0.7 mph. It's not an issue of the sensor not working -- it does.

I'm not familiar with laser triangulation. do you have a quick resource for me to spot?

Honestly, I don't care about it being GPS, per se. I only want to have a speed solution that works for my specific speed range.

I may have a solution already, if this cable we ordered that goes from the CANBUS on the A-post in the tractor to the 844E actually works. It will (should) pick up the speed signal from the tractor, and input it into the 844E.

According to TeeJet, the 844E doesn't care where the speed signal comes from, as long as it gets a speed signal.

I'm posting here in case my solution doesn't work.

https://en.wikipedia.org/wiki/Laser_surface_velocimeter

As stated above:

The tractor is pulling an implement version of an asphalt roto-mill. It grinds\mixes\processes soils (can it can rigged to do asphalt and concrete. This one, however, is not).

The depth of the grind swath is anywhere from 6" deep to 12" deep, with 6" being normal, and thus being able to go in the 0.3 mph - 0.5 mph.

This grinder is a beast, requiring 300 shaft horsepower to run. We're using a 2012 JD 8360R (360 hp) to pull it.

The GPS speed sensor control is simply labeled as a TeeJet GPS Speed Sensor. Honestly, I can't find the model on TeeJet's website. I can find the antenna it uses, but not the sensor itself.

The 844E can use radar, mechanical, or GPS (which is configured as radar, as per the owner's manual).

the 8360R uses an active radar system, and it most certainly reads to 0.1 mph.

Now, going only 0.1 mph is a relatively rare occurrence, it can and does happen. I would say, however, that the tractor operates nominally between .25 and .5 mph as a decent average.

Most GPS (and other) speed systems are designed around a >1 mph speed paradigm.

Currently, we go from the GPS antenna > SMA to the GPS Speed Sensor > connect via Deutsch connector to wiring that connects directly to the main wiring harness that goes into the main electrical and communications interface to the 844E.

Well it should say on the front of the gps unit one of these:

Matrix pro

Centerline 220

Boompilot

Matrix 430

...and the pdf on the unit should show how to hook into alternative speed source...

I dont know why this image is sideways, but here is the exact image of the GPS speed sensor and the 844E in question.
There is no secondary or tertiary marks for model number, etc.

Along with farming 600 acres of row crops, and working closely with my great friend and C J Miller, Sr, - the area's most innovative contractor, I have the suspicion that this is a case of plain old "the book doesn't work.

You said up front that the depth varied enormously; with that fact alone indicates to me the mass of product you seek to treat could also vary accordingly - so if your speed was 99% accurate, what do you know?

I'd suspect there is someplace on the machine between the point when the material comes together from the grind, until discharged, be it a section of conveyor, or the volume passing a point, down to what I'd like best, scales on the collection unit that's being filled, you could come up with something much closer to real #'s.

It sounds as though currently the speed times some "standard" mass per linear foot is being used in the equation, and it's silly. A good operator will out-guess that program, or I'll do without the dirt in my coffee.

I really don't understand what you're getting at, but I'll try to clarify what I can:

Along with farming 600 acres of row crops, and working closely with my great friend and C J Miller, Sr, - the area's most innovative contractor, I have the suspicion that this is a case of plain old "the book doesn't work.

I have no idea what this phrase even means.

You said up front that the depth varied enormously; with that fact alone indicates to me the mass of product you seek to treat could also vary accordingly - so if your speed was 99% accurate, what do you know?

The depth of a carve can vary enormously. However, the depth is set at 'x' at the start of a particular project, and remains until at least that portion is completed. I also have indicated that there is a nominal depth (6" for most jobs) that the machine is set to.

The speed being 99% accurate would enable me to ensure that any application errors happening from the controls side, would have to be between the bypass valve and the nozzles.

I believe I have a couple of issues, some minor in nature, but end up being multiplicative, due to the fact I do not have a reliable speed output.

I'd suspect there is someplace on the machine between the point when the material comes together from the grind, until discharged, be it a section of conveyor, or the volume passing a point, down to what I'd like best, scales on the collection unit that's being filled, you could come up with something much closer to real #'s.

My avatar is a picture of the grinder\mixer in question. the product is ground, mixed, then discharged out of the back of the machine. The output pattern can be partially dictated by manipulating the hood in the back. As the hood closes more, the soil particles\aggregate are inside the grinder\mixer body, yielding smaller particles, at the expense of speed.

It sounds as though currently the speed times some "standard" mass per linear foot is being used in the equation, and it's silly. A good operator will out-guess that program, or I'll do without the dirt in my coffee.

You are incorrect here, sir. The 844E controller is an agricultural rate controller and monitor. There are two ways to set it up: gallons per acre, or gallons/1000 ft². The 844E takes nozzle size, your GPA settings, and utilizes your forward speed for rate application. Just like it does in 100% of other, similar, agricultural settings. The difference here is our very low speed.

The GPA setting will not work for my application, because mathematically, I need 10,000 gallons per acre, and the controller only goes to 9999. Not really far off, until I go to 8" deep, where it becomes 14,000 gallons per acre. I'm now trying out turf mode, or gallons\1000 ft²

I will tell you, however, that we mathematically know exactly how much product needs injected, 100% of the time. This data set does NOT ever change.

Currently, due to having to run the controls manually, we ARE using a "mass" type equation, to calculate how far our water trucks full of product should go. We're currently fairly accurate in my calculations.

Automation would greatly assist in the precision of the application, which is why I'm still trying to automate.

Well using Portland cement mixed into the soil at the proper rate allows projects to move forward on schedule by absorbing enough water to pass compaction tests, yet still be dug and moved by hand tools. CJ initiated that practice in the Baltimore Washington area, and I documented it with a movie in order to get some parameters and acceptance from the government. I was trying to explain I wasn't a book type that couldn't fathom your problem, that's all.

If you'd (I was guilty of this with my very first post) have just said what you did from the start, I'd not have wasted everyone's time. By altering the moisture and whatever else and using it coming out the other end? Sounds like a horror story. I never dreamed of something this complex, from your opening question.

My best wishes, and all I can do is encourage you - the guys and girl(s) on this forum do their very best to help.

Please just try and "switch shoes" by giving them as much pertinent information and the history as you might require.

I'm actually working on getting some class-C flyash to be able to mix.

You're closer to what I'm doing, I think, than you realize.

Flyash contains high amounts of calcium (which is what I need), in addition to have a mass of <200# mesh particles to allow for my chemicals to bond. This product, when correctly applied, changes the clayey soil to a sedimentary-textured, stone like road surface, stablized, and ready for immediate use, or ready for chipseal, asphalt, or concrete work on top.

Lime can drastically increase the resilient modulus of soil stabilization, too. Which adds yet another layer of complexity into what I'm doing.

So, you now understand the difficulty of my project -- it's dirt simple in design, and in theory.

In real-world application? Notsomuch.

I apologize if I sounded off, too. I was only trying to input minimal pertinent information. Some people don't like to have an excess of information not related to the issue at hand.

Again, I apologize if I sounded "off". That was not my intention.

None necessary, and you are correct as far as the similarity goes. That movie I made in the early '90's for the Contractor's Association was work in progress on 3 acres in Columbia, MD. for a Target store. There are quite a few zip codes with mean family income over 200K/year within 20 miles of there. They were willing to spend an extra 3M to get that building up and complete by Thanksgiving. (In those days it is scribed in stone and painted on the walls and tenement halls with some respect for tradition)

We were excited about it. Now, I get excited if I can get out of bed in less than 5 minutes. Remember, sticks and stones will break my bones, but vehicles with drunken drivers only fracture them in over a thousand places! Hang in there.

Here is a brochure for GPS unit with a 20 Hz refresh rate.

Not sure if it is accurate down to .1 MPH but it might be worth a phone call.

I contacted Dickey-john.

They evidently don't manufacture those any more, and I have been redirected to Ag Express.

He DID, however, indicated to me that he was unsure if that particular GPS would read much below 5 mph.

So, off to research laser speed guidance, and more mechanical speed guidance.

I don't believe for a moment this is an issue of "I can't do this", it's simply an issue of "HOW can I do this?"

Thank you kindly for the information, looks like I need to keep digging.

Any other ideas would be appreciated on a level orders of magnitude larger than the heat output of the sun.

This looks promising....

https://scholar.google.com/scholar?safe=off&rlz=1C1PCTG_enUS441&es_sm=122&biw=1280&bih=635&bav=on.2,or.r_cp.&bvm=bv.103627116,d.dmo&um=1&ie=UTF-8&lr&q=related:GvnZ507ePGOwoM:scholar.google.com/

I guess you could just put a bicycle generator on so that you could engage it on the tire at low speeds and measure the output with a sensitive meter....

http://salestores.com/windngo7950b.html

Thanks Solar,

I have to dig my old fish finder out and see if I can soup it up.

http://www.sunrom.com/p/microwave-doppler-radar-sensor-for-motion-and-speed-sensing

Well said.

I'm thinking if OP's CANBUS reading works, that may be a good solution, as long as the machine is always used on a tractor with CANBUS. Another possibility, if the machine has wheel(s) is to use an encoder, similar to the ABS sensor on automobiles maybe, as others have said

I agree. The GPS is not well suited to sense .1 MPH from its 22K mile geosynchronous orbit.

The optical encoder on a drive wheel has promise as well as playing with the bypass valve sensitivity.

In another life, we used an optical encoder on the crankshaft to explore active cab noise cancellation in a John Deere tractor.

The problem with this is that the tires can slip in the dirt so that the turning of the tires does not equal the actual ground speed...

The only way I can see to solve the GPS issue is to contact the manufacturer/vendor and have them send you a firmware & software update that will move the "zero" down to .1MPH or provide you with a new unit that will do so.

You might be able to utilize an adapter/converter between the speed sensor to increase the ratio then label the display accordingly to reflect true tractor speed. (Fool the GPS) I would surmise that if you do this it will take some tuning of the machine and process to offset the effects developed by new dynamics.

The issue I've found involving my (admittedly limited) research into GPS is that >95% of GPS applications are concerned at the >5 mph paradigm.

Your idea, actually, has been brought up by myself, and one of the TeeJet personnel that I'm dealing with.

My idea is to flash the EEPROM with a faster response (say 5Hz to 10Hz) to see if that helps at all. Commercial aircraft have 20Hz signaling, but it comes at a premium price.

A separate wheel in contact with the ground,with built in speed sensor, could be used for true ground speed.

Before I elaborate, is this application a pavement grinder? One that flows the "grindings" into another unit or truck so they can be reprocessed making "hybrid-blacktop"?

The machine in question is an implement version of an asphalt roto-mill. This one is currently set up for soil stabilization, instead of asphalt and concrete work.

We do work on equipment pads, county roads, etc. The grinder chews up the soil, product and water get injected midstream, and ground\mixed soil product comes out the back end, ready for additional moisture to be lain to get the soil ready for compaction, so the product can activate and cure properly.

I have an update for you guys:
I received my cable from AgExpress, to go from the A-post of the tractor via CANBUS, to the 844E.

It appears that I'm receiving zero signal from the CANBUS. I've swapped the little input sensor from GPS to radar, and have calibrated the dual-beam radar, as per the owner's manual.

I can't figure out how to tell if the radar is even working, as the speed the tractor shows is pulled off the actual transmission speed sensor.

See, the GPS speed sensor was set at 1300 pulses. While I know this is way off for an actual signal from the dual-beam radar, I should at least be seeing *something* as far as speed input goes, even if it's ridiculously off.

I placed a call to AgExpress, and they basically told me to call John Deere, which I did first thing this morning (I haven't heard back yet). I'm trying to see what else in the "DUH" department I can check, before I go all crazy and ohm the cable out or something.

I have a friend who works in the coal mines here in Gillette, and he told me they ended up going directly off the transmission speed sensor for their speed input.

Should I even consider this dark path, or stick with the magnetic speed sensor? AgExpress makes a solution with 60 magnets, and they sell an extra 60 magnet set.

On a lighter note, I did another calibration of the other (new) GPS speed sensor antenna. I am now able to read at approx 0.5 mph, which is better than the previous 0.7 mph. Had I been able to drive in an actual straight line (stupid people using their stupid public road I was testing on), I might have done even a teeny bit better. At 0.5 mph, it reads decently, but it does bounce a bit. 0.6 mph is solid, though.

What do you guys think?

Keep up the good work.

I believe we have a solution to our issue, guys!

I'm going to get get an optical sensor (as was suggested here!), and make a pinwheel.

I'm in contact with the Danes at TeeJet to get the pulse information for the 844E. I need the amplitude of the pulse (envelope of the square wave), the wave insertion (is it positive or negative), and frequency range. The idea is to see if we can emulate a magnetic speed pulse, as a real magnetic speed sensor, the magnets would be so close together, we don't believe we'd get any pulse modulation.

I've been in contact with Monarch Instruments to see about what optical sensors they have available. Does anyone know of a decent outdoor rated sensor?

I want to thank every one of you for your feedback, and assistance. Between this forum, and a couple of resources I tapped, I've come up with a solution.

Thank you guys so very much.

kv,

A question for you, There is road construction going on near me, I noticed a layer of light tan colored material has been laid down as a base for the shoulder pavement (asphalt). Would you happen to know what this could be?

Good luck.

https://en.wikipedia.org/wiki/Caliche

Thanks Java,

"Caliche is widely used as a base material when it is locally available and cheap. However it does not hold up to moisture (rain), and is never used if a hard rock base material, such as limestone, is available."

It figures, that area floods, and the site is 5 miles from one of the largest limestone quarry's in the U.S.

I went over to the AgTalk forums, and a guy said that the A-post interface I'm trying to tie to for radar purposes also has a conductor for the transmission speed sensor.

Can anyone verify this, or perhaps guide me where to go to discover this myself?

If I can get the transmission speed signal, then winner\winner chicken dinner.

Well, maybe, but don't fire up the fryer yet. How are you going to get the data?
If I understand it right, A-post = CANbus = ISOBUS = ISO 11783
According to this, the CAN bus is a four-wire serial interface.
Googling around some, it seems that speed information (in mm/sec) may be available on the bus. But it seems you'll need some hardware and software interface to translate it from the bus to your device.
If you're feeling brave, this paper might help.

The cable from AgExpress works!

I would say it works with 90% accuracy, out of the box. I've not adjusted the calibration numbers on the TeeJet 844E yet, but it follows all the way down to 0.1 mph!

The cable in question is pinned from #2 on the CANbus of the tractor (#2 pin is the transmission speed sensor, #1 is GPS\radar), to the signal of the 844E. It's a $60USD cable from AgExpress.

I'm not sure if manipulating the calibration number in the TeeJet would be of any benefit, though. Any thoughts?

Thank you all again for your assistance! I'm glad I could come up with a solution.