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Topic: Sensing Ground speed in Inches per minute (20ipm to 40ipm) (Read 400 times) previous topic - next topic

Railroader

@Robin2 and @GoForSmoke

You've got a point. But… somehow the NEO-6M manages to show speeds as low as a few km/h, walking speed. I don't even need to walk 10 meters to get readings.
What the accurazy might be has not been checked.
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

wildbill

@Robin2 and @GoForSmoke

You've got a point. But… somehow the NEO-6M manages to show speeds as low as a few km/h, walking speed. I don't even need to walk 10 meters to get readings.
What the accurazy might be has not been checked.

In the OP, the mid range need is for 30"/minute measured over a minute, adjust and let it go. So, less than a meter: GPS just won't cut it. 

Railroader

What will this machine be doing that needs that high resolution? Drill through rock?
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

Robin2

Two or three hours spent thinking and reading documentation solves most programming problems.

Paul_KD7HB

MY wild guess is the machine is digging a ditch and laying plastic irrigation pipe in the ditch. Probably in the Sacramento valley of California.

Paul

DaveEvans

Check out this interesting optical flow device (similar to optical computer mice, it estimates velocity via image processing): https://docs.px4.io/v1.9.0/en/sensor/px4flow.html



Quote
The ortho photo below shows that a flight on the park roads is accurately measured. This was done with a PX4FMU on a 7" quad flying at about 1.6 m altitude in manual flight. No GPS, only integration of PX4FLOW (velocity)



This paper has an explanation of the above test and additional tests...an interesting read:  https://github.com/PX4/px4_user_guide/raw/master/assets/hardware/sensors/px4flow/px4flow_paper.pdf


It may satisfy the OP's requirements.

There is an Arduino library with I2C interface.




Railroader

@DaveEvans
What does that piece of hightech device cost? How much coding to get inches per minute?

More guesses. Could it be a gold digging machine?
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

DaveEvans

Cost: 150 USD at one vendor, but out of stock.
Code effort: I don't know, but a quick glance at the Arduino library makes it seem like it should be "not too hard."  From the basic example:

Code: [Select]
void loop()
{
  sensor.update();
 
  Serial.print("#");
  Serial.print(sensor.flow_comp_m_x());Serial.print(","); 'velocity*1000  (meters/time step)
  Serial.print(sensor.flow_comp_m_y());Serial.print(",");
  Serial.println(sensor.ground_distance());

  delay(100);
}



Railroader

Oops, 150 USD.... All kind of vision technology cost a lot. I heard high tech engineers suggesting that 30 years ago. The mechanics skilled engineer solved the matter using a cheap light array....

It sounds like a heavy overkill to me but let OP do the economical calcs. Maybe he is digging gold… Gold Rush...
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

DaveEvans

My guess is that if it works, is reliable and doesn't need much maintenance, then $150 (plus other costs to implement it) will be "in the noise."


However, keeping the lens clean enough in an "agricultural field" may be a deal killer (dust, mud splatters...) 

Also, although I think the device could work great in a bare field of plowed dirt, if it traverses a windy field of grain, corn, or other leafy greens, the movement of the plants may confound the image processor (unless mounted relatively close to the ground so the field of vision is on, say, the tire or track print, and not on things waving in the breeze).

KEwert

Thanks for the suggestions everyone! As for the purpose of the machine, unfortunately its not mining gold. Instead it is a water irrigator for crops, exciting huh. And before anyone says it, yes I know what im looking for already exists, but I'm cheap and I like the challenge of doing it myself. Also the last part I had to replace on the machine the manufacture wanted $450 for a replacement. It was a custom circuit board and 128ppr optical encoder they made to shut down the drive system if the irrigator became stuck. I replaced their board with a $20 arduino, reused the encoder and added a $30 24VAC to 12VDC power supply for the arduino, and its been running perfect ever since.

And Yes, ive already tried using the encoder for the speed pickup, but its at the center point of the pivot so in order for the encoder to see a single pulse the end has to move 66.26ft. Which moving at a rate of 30ipm, will take 26.5 minutes (which is way to long to wait to get a speed reading).

DaveEvans, that sensor looks promising, Ill for sure be reading up on it. Like you said $150 would be worth it, if its not too sensitive to dust on the lens.







GoForSmoke

@Robin2 and @GoForSmoke

You've got a point. But… somehow the NEO-6M manages to show speeds as low as a few km/h, walking speed. I don't even need to walk 10 meters to get readings.
What the accurazy might be has not been checked.

Does it have an accelerometer?
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

GoForSmoke

Thanks for the suggestions everyone! As for the purpose of the machine, unfortunately its not mining gold. Instead it is a water irrigator for crops, exciting huh.
Does it carry the water? Is there a water pipe that a roller could be rolling against?

Where does the hydraulic power come from?
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

Slumpert

Shame it's not a simple center pivot irrigation..  encoder on the pivot and force gauges on each link make controlling those pretty straightforward.

Probably the most precise method I can think of would be to have a suitable sized spool of cord and anchor one end behind the machine.

Now you can simple use a encoder on the spool to give very accurate speed measurement.

Your machine is traveling less than 200feet a hour, so it's feasible.  Few minutes to rewind a spool vs babysitting machine nonstop.

Robin2

Shame it's not a simple center pivot irrigation..
I suspect it is.

And Yes, ive already tried using the encoder for the speed pickup, but its at the center point of the pivot
...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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