Electronic – How to measure distance travelled in cm without gps

distance

I was asked to build a circuit that will measure the distance travelled of a small vehicle, like a lawn mower.

There's a requirement that it would measure distance travelled in cm/sec. GPS is too inaccurate, and the starting point is unknown. I'm unable to put anything in the ground.

Any ideas? I can use whatever IC I want. I thought of using a camera pointing down, like a mouse, but it seems too complicated to process outside of home.

Best Answer

Since the small vehicle is like a lawn mower I am assuming the small vehicle has wheels. You have many options to choose from based on your requirements.

  • As PeterJ suggested you can use a quadrature encoder.
  • Another option is use and Hall effect sensor. This type of application is used frequently in automotive applications.
  • The use of an accelerometer will enable speed measurements. Consider a three axis accelerometer, thus this will infomation as as to if the vehicle going up an incline or down an incline. I create a simple accelerometer demo using Beaglebone black, Embedded QT and ADXL345 which can be found here. The source is available to public on github. I also did similar demo using TIVA ARM Cortex M4 + ADXL345. I can make the source code pubic if interested.
  • The use of a magnetometers will help determine direction in XY direction

Also take a look at the Dead reckoning concept. Dead reckoning doesn't use GPS, and is widely used in automotive navigation applications when GPS is not present, such as driving through a tunnel.

Another interesting application is irobot create. As I understand the both hardware and software is open sourced. This will give some good ideas for your project. Below is picture of guts of iRobot command module.

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Another option would to use myRio from NI. Although the hardware is not open source myRio allows you the connect to LabView to help develop algorithms.

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