It is very easy on paper or CRT terminal. However, it is NOT so easy in
real life since one must ensure that virtually NO ultrasound reaches the
receiver directly from the transmitter and that the signal that the
receiver gets is JUST reflection. Remember, all of this is going on
under the skirt of the 'bot. Direct coupling from xmtr --> rcvr is
going to be very difficult--not impossible, I agree--but difficult.
I've worked quite a bit with these 40KHz transducers and they are very
sensitive when you don't want them to be and you can't get enough signal
out of them when you want it. The transmitter almost has to be mounted
behind the receiver and mechanically isolated from it. Ultrasound
travels very well thru solid object, e.g. the mowbot's frame. The
receiver would have to be sound insulated from the rear so that it would
only pick up the reflected signal.
It is a good idea, but I woudn't want the success of the project to
hinge on this point.
Tom