Maxbotic I2C Sonar interference

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AJ152 August 11, 2016 at 5:55pm

Thanks Gary

Gary McCray said:

Hi AJ152,

This wiki page covers the variety of sensors currently interfaced to the Pixhawk and ArduRover code.

http://ardupilot.org/rover/docs/common-rangefinder-landingpage.html

Hope this helps,

Gary
Gary McCray August 8, 2016 at 12:22pm

Hi AJ152,

This wiki page covers the variety of sensors currently interfaced to the Pixhawk and ArduRover code.

http://ardupilot.org/rover/docs/common-rangefinder-landingpage.html

Hope this helps,

Gary

Rangefinders (landing page) — Rover documentation
Gary McCray August 8, 2016 at 11:28am

Hi AJ152,

Lidar can also be used on Rovers and is generally much more reliable than Sonar.

The Ideal is a scanning LIDAR such as SICK, Hokuyo or Lightware, but to use one of those with ArduRover on a Pixhawk, you really, at this time, need to interface through a companion computer using ROS and it is really still much more of a developer level project.

The easiest way right now for rovers is to substitute two inexpensive Pulsed Light Lidar-Lite or Lightware Lidars for the 2 sonars used for Rover object detection and course correction in the ArduRover setup.

Eventually, scanning Lidar will be the main solution for this, but it is really still in it's infancy for our Rovers.

The inexpensive IR angle distance sensors do not work at all well for this.

Tom Coyle (Main Rover guy) actually has gotten the 2 Sonar object detection - course correction system to sort of work, but for a whole lot of reasons (mostly bad returns from assorted conditions), I believe he has found it considerably less than satisfactory.

Sonar really doesn't work very well in air, much better in water.

I am slowly working on a scanned Lidar solution myself, but I have several other projects that are interfering right now.

Best Regards,

Gary
AJ152 August 8, 2016 at 10:43am

This is great info, thank you Gary. Do you suggest other types of Sensors for a Rover?

Gary McCray said:

Short answer is a qualified yes.

All SONAR transducers are basically high frequency speakers - in this case transceivers operating as both speaker and microphone.

The work by oscillating an electromagnet to transmit and detecting the return as vibrations in the same electromagnet.

Clearly they can produce EMF and the Maxbotic ones are generally not very well shielded, however, the frequency is generally low enough that it does not interfere (much) in the high frequency domains of the devices you are referencing.

I have heard of at least a few instances where interference was suspected for both RX and for GPS, but if there is reasonable physical separation that really shouldn't be a problem.

In fact, a much greater problem is the Sonars own sensitivity to outside interference.

These things are notorious for getting their signals wiped out from external RF, EMF, vibration and external sound sources. (I speak from personal experience).

They need to be acoustically shielded with a cone and the transducer end needs to be isolated from high frequency vibration and preferably have a EMF and RF proof box around them as well as using shielded signal wires.

Basically in multicopter use we have not gotten generally worthwhile results from them.

They can be made to work, but it is a major pain to do so and even the cheap LIDAR systems work much better.
Gary McCray August 7, 2016 at 4:42pm

Short answer is a qualified yes.

All SONAR transducers are basically high frequency speakers - in this case transceivers operating as both speaker and microphone.

The work by oscillating an electromagnet to transmit and detecting the return as vibrations in the same electromagnet.

Clearly they can produce EMF and the Maxbotic ones are generally not very well shielded, however, the frequency is generally low enough that it does not interfere (much) in the high frequency domains of the devices you are referencing.

I have heard of at least a few instances where interference was suspected for both RX and for GPS, but if there is reasonable physical separation that really shouldn't be a problem.

In fact, a much greater problem is the Sonars own sensitivity to outside interference.

These things are notorious for getting their signals wiped out from external RF, EMF, vibration and external sound sources. (I speak from personal experience).

They need to be acoustically shielded with a cone and the transducer end needs to be isolated from high frequency vibration and preferably have a EMF and RF proof box around them as well as using shielded signal wires.

Basically in multicopter use we have not gotten generally worthwhile results from them.

They can be made to work, but it is a major pain to do so and even the cheap LIDAR systems work much better.

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Maxbotic I2C Sonar interference

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