Ultrasonic Sensors

[Tom Line]

Please be aware there are some issues using the Analog output of the Maxbotix sensor.

#1 There is a "bump" if you have a large change in distance. The sensor will overshoot the actual distance and then ramp back down to the correct one. You can filter this using averaging, but it will slow the response.
#2 Don't expect to be able to use these to track or range other robots. They respond too slowly. Last year, at full speed using these sensors, we had to stop when the sensor hit 48 inches because of the response time. If we did so, it was actually hitting the brakes at about 18 inches, and stopping with 3 or 4 inches to spare.

What you CAN do with these is use them for collision detection. You can also aim them at a continuing obstruction. For instance - aim it a wall that you're traveling next to. You can keep track of how close you are to it.

I do not know if the other outputs of the Maxbotix will exhibit the same behavior. I'd suggest purchasing one and working with it before you decide it will solve your problems.

For static ranging, however, they are VERY accurate. Consistently within less that an inch.

[PWHSrobotics]

We got our sensors today, but have a question

- How are other teams hooking up the sensors to work with the built in Ultrasonic VI's given to us in labview?

[PWHSrobotics]

any help or a link to a topic that this was already answered in would be much appreciated

[nathanww]

I'm not a labview programmer, but as I understand the built-in ultrasonics routines are for digital ultrasonic sensors(the system sends out a ping and then waits to hear the returning ping). The maxbotics has a coprocessor that does this, so instead of using digital pulses, it just sends you back an analog value, which you can read the same way you'd read a potentiometer.

[Tom Line]

Originally Posted by nathanww

I'm not a labview programmer, but as I understand the built-in ultrasonics routines are for digital ultrasonic sensors(the system sends out a ping and then waits to hear the returning ping). The maxbotics has a coprocessor that does this, so instead of using digital pulses, it just sends you back an analog value, which you can read the same way you'd read a potentiometer.

The maxbotics will send PWM values or analog values. Take your pick.

If you use the analog values, you can simply read the analog channel and divide by a constant to get number of inches.

No idea about the ultrasonics sensor VI - it was easier for me to do it the way I stated since we used them last year.

[windell747]

I'm not sure how to get the sensors working with the labview tutorial, but if you have the ones that output an analog voltage I can imagine you can just read in the value as an analog input and scale that value by a constant by multiplying a constant to it.

[tennisbeast29]

I was thinking about using an ultrasonic range finder. It's very good at detecting walls and other solid objects.

But for robots, which have different sized parts hanging about and holes everywhere that could have echos, I thought it wouldn't really be accurate because they would all affect the distance. This is my first year so I'm not sure, did this system work for anyone?