z-axis movement via ultrasonic sensor

Hello !

my question is ,
can we use ultra sonic sensor to the z axis to keep it above the ground , so whenever ground have uneven surface ultrasonic sensor detect that and moves the axis upwards and downwards.

long story shorts can we keep the ground clearance (between tool and workpes) constant ?

In my project precision it not a problem. .Can you please give me any hint so i can get more information about it..

Sorry for the late response sir, i am trying to make cake decorator so there may be ups and downs on cake surface
so that's why i want to put sensor on z axis so it can move tool up and down during execution.
here is a picture
where A should be read by sensor and moves the tools accordingly ..please help me out with this.

Thank You sir

?????

I dont think its easy for cake...youll take a lot time to adjust it, for metal people use one method called breakaway, when the nozzle colide with the work material the nozzle breakaway from the support, in your case maybe it drop up the cake...i saw here one guy use wire to avoid it to drop...whats 3? 3mm, 3cm or 3 inch? why you need one machine to do it? 3cm will be more easy to implement.
The sensor work. Actually the machine dont have idea what sensor you are using, just signal and if the signal was consistent or not.
You wanna real time height adjustment?
Do you have 3D printer?
If no check bed leveling in 3D printer, someone here started talk about 3D printer but i think stopped talking about it, search here in the forum.

Ultrasonic sensor have mm to meters circumference range. In industry now i saw a lot people using fiber now.

The material surface will be pretty trick i think using ultrasonic.