Test 1
As I start my design of an SRS Robo-Magellan robot I have the strong desire to build off my successes and failures and of course; try something different.
On my list of “wants” is a sensor to measure distance to ground. Obviously this is normally fix unless you have suspension, and indeed I have suspension. I want to ensure my robot doesn’t bottom out while climbing hills, or if I’ve come upon a bit of a gap I don’t want my wheels to roll over.
My perception of the issue is .. grass.
Problem: I want a sensor that can give me AGL that see’s mostly into the grass. I would love if it if was non-contact but still has to be mostly water proof.
First up is one pile of junk, but good enough for the basics. An ultrasonic sensor the HC-SR04
Measured Frequency ~38KHZ
250mm accuracy <5mm
I presented sample container to sensor. The container was about 120mm wide with grass. I found surrounding area affected readings so I hacked together a cone for the sensor. The cone corrected the reading abnormalities.
Sample weed-like grass had a rough dirt floor at 70mm above base table. The sensor is 255 millimeters above the table base.
Measurement of 10 reading rolling average was 117-122mm from table base to measured height.
Unfortunately this doesn’t really get us as far into the grass as I’d like. Worst thought is that the tallest blades rose to within 5mm from cone visibility and started causing sensor reliability issues, giving me readings greater than the length through the base. This sensor, in my opinion, is unreliable for this application.
… parts ordered for future testing but suggestions welcomed.