Testing a SRF02 Sonar - partial FAIL

Hello All,

After plenty of testing I have concluded that the SRF02 sonar is NOT A VIABLE REPLACEMENT for the Maxbotics MB1200 series of sonars for the downward looking (alt hold) sonar on Arducopters.

R287-SRF02.jpgIt may however be OK as candidate for any future obstacle avoidance developments

The SRF02 was attractive to me for three reasons:

1) it is an i2c device (ie it sends its range signal back to the arducopter as a digital signal) and,

2) you can command a reading from it (ie it is not ranging all the time)

3) it is relatively low cost (less than £10 or approx $20)

One of the likely sources of sonar noise that a lot of people see in their arducopters is the analog signal, many people have lessened their noise problems by shielding the signal cable and moving the sonar and cables away from their ESCs - hence the digital (i2c) sonar was worth a look.

In the future I'd like to test some obstacle avoidance - to do this you need approximately five sonars operating (front , back, left, right + down). The sonar modules we use will interfere with each other if two are ranging at roughly the same time. Having a sonar module you could command to range was therefore worth a look.

So why is not a viable replacement?

Well  - It does work OK its just that the Maxbotics modules are better in a few important ways.

1) range the SRF02 is quoted at 6 meters in reality it is only able to do that over a hard surface. Over grass it is less than half that range reliably

2) it seems to be more sensitive to noise (or less sensitive to signal - hard to know which)  than the MB1200 series of modules. See the attached graph - The red line is the SRF02 sonar data , green is barometer and blue the commanded altitude. With a bit more filtering the noise could be reduced but this is not seen in an unshielded Maxbotics sonar mounted in the same location. This test included flying the copter in Alt Hold mode up and down over a mound about 2 meters high - this is why the Barometer graph does not follow the sonar. It also means the ground below the sonar was angled at up to 20 degrees. My interpretation of this is that the sensor is just not picking up some of the ultrasonic returns and giving bad range data for this reason.

3690898448?profile=originalI have written a SRF02 Library reasonably compatible with the Arducopter code if anyone is interested. When I get the time I will investigate using the SRF02 sonars and this library for obstacle avoidance.

Here is the Library: SRF02.zip

 Back to my I2C version of the Maxbotics sonar for now for me

-Andrew

You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –

Replies

  • Admin

    agmatthews,

    Nice experiment and good analysis of the results. I have both of the sensors, but use them in a rover for obstacle avoidance.

    Regards,

    TCIII

This reply was deleted.

Activity

DIY Drones via Twitter
20 hours ago
DIY Robocars via Twitter
RT @Heavy02011: @diyrobocars : A Home-brew computer club* for Connected Autonomous Driving on Jan 23rd, 2021 https://www.meetup.com/Connected-Autonomous-Driving/events/275728684/ #Meetu…
20 hours ago
DIY Robocars via Twitter
20 hours ago
David Hori liked Isabella Domi's profile
Wednesday
DIY Robocars via Twitter
RT @Heavy02011: ⁦@diyrobocars⁩ Autonomous Driving Assembly at #rC3. join us at https://rc3.world/rc3/assembly/diyrobocars-f1tenth/ ⁦@f1tenth⁩ ⁦@DAVGtech⁩ ⁦@DWalmroth⁩…
Monday
DIY Robocars via Twitter
RT @chr1sa: New car designs coming for our next @DIYRobocars @donkey_car virtual race on the 23rd. Choose any one you want at race time Le…
Monday
DIY Robocars via Twitter
RT @RoboticMasters: Thanks to @EllerbachMaxime and the Sydney Uni Capstone Students the @donkey_car @diyrobocars simulator is getting a ma…
Monday
DIY Robocars via Twitter
Jan 6
DIY Robocars via Twitter
Dec 28, 2020
DIY Robocars via Twitter
An interesting line-following simulator to use with with your robocars: https://github.com/ron-grant/LFS
Dec 23, 2020
DIY Robocars via Twitter
Dec 23, 2020
DIY Robocars via Twitter
An improved version of the @IntelAIResearch OpenBot: https://diyrobocars.com/2020/12/14/an-improved-version-of-the-intel-openbot/
Dec 14, 2020
DIY Drones via Twitter
An improved version of the Intel OpenBot https://ift.tt/2KkHT8Q
Dec 14, 2020
DIY Robocars via Twitter
Dec 10, 2020
DIY Robocars via Twitter
RT @KN_Richardson: Delivery 📦😬 Early xmas present from @ccbdcdt ! Sims ready, will put h/w together over Christmas break. Didn’t need to mo…
Dec 7, 2020
DIY Robocars via Twitter
RT @RoboticMasters: Did we mention there's new car models in the #donkeycar simulator too? Here is an RB16 from team @redbull @donkey_ca…
Dec 7, 2020
More…