How Can We Improve Odometer Accuracy for Precision Testing in Civil Engineering?

  • Thread starter Thread starter AshNZ
  • Start date Start date
  • Tags Tags
    Measuring
Click For Summary

Discussion Overview

The discussion revolves around improving the accuracy of odometers for precision testing in civil engineering, specifically for measuring short distances (2-3 meters) with a required accuracy of ±0.1 meters. Participants explore various devices and methods suitable for use in a medium-sized truck during slow movement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants express concerns about the feasibility of achieving high accuracy with a rubber wheel on a real road due to potential slipping or deformation.
  • Others suggest that making turns could complicate the accuracy of distance measurement, as wheels may travel different distances.
  • One participant proposes reconsidering the need for such precision over short distances, suggesting simpler alternatives like a rule laid on the ground with a pointer attached to the truck.
  • Several participants recommend using RTK GPS, total station theodolites, or laser distance meters as potential solutions.
  • Ultrasonic distance meters and stereo laser devices are mentioned as possibly effective tools for the task.
  • One idea involves attaching a distance wheel to the truck and connecting it to a display for the driver, possibly using a camera for readability.
  • A suggestion is made to tape a laser pointer to the truck's wheel and align it with printed scale markings on the ground for calibration.
  • Another participant discusses the possibility of using a tacho solution with an angle encoder on the rear axles, noting potential accuracy issues due to load and surface conditions.
  • There are mentions of using a trailing wheel with a fraction of a revolution counter as a DIY solution.
  • Clarification is provided that the project has a practical application related to pavement testing, similar to the Benkelman Beam test.

Areas of Agreement / Disagreement

Participants express a variety of viewpoints regarding the best approach to achieve the desired odometer accuracy. No consensus is reached, and multiple competing ideas and methods are presented throughout the discussion.

Contextual Notes

Some limitations include the dependence on road conditions, the potential for tire compression affecting measurements, and the challenges posed by turning the truck. The discussion also highlights the need for further clarification on the specific requirements and constraints of the project.

AshNZ
Messages
9
Reaction score
0
Hi,

I'm a civil engineering student in a summer internship at the moment but I've come across a mechanical issue. We want to buy or build a very accurate (+- 100mm) odometer for a large truck. We have a Survmaster precision odometer in there but it's only accurate to +- 1.0m which isn't good enough.

Do you have any ideas about any devices that we could build? It should be readable from the truck cab and driver should not have to come out to adjust too many things (in other words it should not be time consuming)

edit: Sorry should have mentioned it before, we're looking at that accuracy over very small distances (2-3m) and at a very slow speed. We need to be able to measure 2.7m +- .1 m.

Any ideas??

Thanks
 
Last edited:
Engineering news on Phys.org
Over what sort of distance?
You are going to have a real problem with a rubber wheel on a real road not slipping or deforming with that sort of accuracy over any resonable distance
 
Heck, just making a turn will cause the distance traveled by the wheels to be different from each other!
 
Sorry should have mentioned it before, we're looking at that accuracy over very small distances (2-3m) and at a very slow speed. We need to be able to measure 2.7m +- .1 m.
 
I can't think of a process that would require moving a large truck with such accuracy over such a short distance, perhaps you need to rethink the whole process and remove that requirement. If that is not possible something as simple as a rule laid on the ground with a pointer attached to the truck would be cheap and simple.
 
Last edited:
Can you rent an RTK gps or total station theodolite ?
Or just a laser distance meter?
 
A good ultrasonic distance meter should be able to handle this no problem. One of those stereo laser distance thinga-majigers would probably work well too.
 
You might want to find a super flat stretch of 30 meters (length of truck + 5 meters approx) and use the above mentioned laser/ultrasonic distance meter. Rinse and repeat
 
Thanks for your replies. Seems like I wasn't 100% clear. What we basically want the truck driver to do is sit in a parked truck, roll the truck forward slowly and stop when he's driven 2.7m. This probably rules the laser distance meters out. The truck isn't an 18 wheeler. It's just medium sized truck with no trailer.

We were looking at having http://www.bing.com/images/search?q=distance+wheel&FORM=BIFD#" and attach it to the truck and then somehow connect it so the driver can read it from the truck cab (maybe with a camera?)

It's not a one off thing that we're doing.. it's part of R&D that my company is undertaking.
 
Last edited by a moderator:
  • #10
Tape a novelty laser pointer facing down to the freehub of one of the front wheels. Print scale markings for about 5 meters using a drafter (at 1:1 ratio of course). Lay it down on a flat stretch. Align laser pointer to the printed scale. You should be able to calibrate it within 5 trials.
 
  • #11
A tacho solution would be fairly easy to implement - on a truck the rear axles are usually accesible, it would be easy to mount an angle encoder on them and either measure the wheel cirumference or just drive and calibrate it.
But you will have accuracy issues with load and surface (the tire will compress changing the circumfernce) or if the truck is turning.

An absolute system with some distance measuring machine and an external target is easiest, assuming you are always moving over the same course.
If not then the easiest solution (assuming you are on a road) would be a trailing wheel - like a survey wheel - but with a fraction of a revolution counter. Just a slotted disc a photodiode and a micro-controller if you want to do it yourself.
 
  • #12
Mugambo said:
Tape a novelty laser pointer facing down to the freehub of one of the front wheels. Print scale markings for about 5 meters using a drafter (at 1:1 ratio of course). Lay it down on a flat stretch. Align laser pointer to the printed scale. You should be able to calibrate it within 5 trials.
...and install a webcam slaved to the laser pointer and outputting to a laptop in the cab.
 
  • #13
Is this just an exercise or is there a practical application?
 
  • #14
Thanks for the suggestions. We close for Christmas today so will come back to this in the new year.

Jobrag, this has a practical application while testing pavements. We have a proprietary test similar to Benkelman Beam test and we're just working on it.
 

Similar threads

"Sane" error margins for emotor torque measurement
  • · Replies 2 ·
Replies
2
Views
2K
As much steam as possible from engine exhaust gas + warm water?
  • · Replies 25 ·
Replies
25
Views
5K
High School Measurements - How can it be that precise?
  • · Replies 42 ·
2
Replies
42
Views
4K
Engineering Pursuing Research in Engineering Versus Hobby Projects
  • · Replies 3 ·
Replies
3
Views
3K
How Can We Improve Precision in Volumetric Dispensing Systems for Small Volumes?
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad How Can We Measure Properties of Distant Planets and Stars?
  • · Replies 12 ·
Replies
12
Views
3K
How would you improve this anti-efficient gas system?
  • · Replies 14 ·
Replies
14
Views
2K
Admissions How Can I Improve My Chances of Getting into a PhD Program in Engineering?
  • · Replies 6 ·
Replies
6
Views
3K
Admissions How to prove Physics competency to grad school admission committees?
  • · Replies 24 ·
Replies
24
Views
4K
How can we accurately measure the natural frequencies of our fixture?
  • · Replies 8 ·
Replies
8
Views
4K