How do you detect ground?

[AceOfHearts]

Hi there,

Is there a way to detect the ground beneath a robot reliably?

Not Ultrasonic, I was thinking something like LED light with phototransistor to detected reflected IR but not sure how feasable this would be.

This is to stop the robot from falling over the edge.

Any ideas appreciated.

 

[dknguyen]

TO detect ground...where? In front of the robot? Under the robot? What's wrong with ultrasonic? It might interefere with another sonar you have already? Anyways, sonar seems to be a fairly reliable way to detect ground. Another way is with those Sharp IR sensors like the GP2D120 (10-80cm) or GP2D12 (4-30cm) depending on how far ahead you want to look. Or instead of using the ranging versions of these Sharp IR sensors, you could use the proximity detector versions that are able to see GP2D15 that don't have a minimum distance, but only report the presence of an object rather tha a distance.

https://www.acroname.com/robotics/info/articles/sharp/sharp.html#e15

But to be honest...for something as important as ground, I'd probably use the same ranging sensors to look ahead and periodicially look at the ground, and then have a tactile sensor that always checks the ground...like an wheel at the end of an antenna or something. Ground is just too important and potentially unpredicable! Touch is the most reliable and important sense...even if it's not very fancy or elegant.

I'm talking more about real outdoors ground here. If it's more like kitchen floors or tabletops where it's flat, an LED and phototransistor would also work...unless the ground was too dark to start with. If the ground is too soft, sonar won't work well either. That's why touch is so great. THe ground just has to be there. It can also tell the difference between water and ground.

 

[Krumlink]

A microswitch with a rounded lever would work perfect. Just position it so that when it lays on the ground it depresses the switch. Simple! You dont need any Subatomic clock with a bistable quad-latteral support system. Just a switch!

 

[AceOfHearts]

thanks

Thanks very much for the responses. Yes, I am already using an Ultasonic sensor for forward obstacle detection.

The micrososwitch sounds like the perfect solution, and I found a microswitch just for this purpose at Maplin electronics website. It has a roller wheel so contact is made when there is pressure on it, perfect! Thanks for the idea.

IR method will deffinately be less reliable compared to a microswitch, as pointed out, due to different coloured grounds absorbing different amounts of IR without reflecting it.

This is my first robot, and it makes me fill with wonder at the human body we are marvell of robotics! Two eyes which are infinately superior than any U.S. or IR sensors with autofocus and full colour 3D vision guiding our way, Legs and arms with muscles allowing us to move and accomplish complex tasks (like the DC/stepper motors but supremely superior), and our extremely complex brain controlling thousands of processes in the body (can be compared to the microcontroller of the robot). Other transducers in the body, touch, taste, smell, sound sensors are all flawlessly designed and connected to the brain (microcontroller).

Deffinately, we are not a product of mere chance, but DESIGNED by a powerful and intelligent Creator. Athiests and evolutionists have got it completely wrong. That's for sure.

Anyway, thanks for the tips, I will be going out to maplins to fetch the micorswitches and some other components.