Autonomous with Ultrasonic sensor doesnt work!!

[Chris Hibner]

Originally Posted by cilginbilgin

We put all of our autonomous code inside the while loop however the robot still doesnt do what we want. We would be really happy if you could help us.

Thanks in advance.

Please post a picture of your new code.

Please see the post from MotorHead above. You autonomous code should look similar to his when your finished.

[cilginbilgin]

Originally Posted by Chris Hibner

Please post a picture of your new code.

Please see the post from MotorHead above. You autonomous code should look similar to his when your finished.

here are the pictures:
http://www.mypicx.com/02012012/Autonomous/

and I think my autonomous code is pretty same with MotorHead's.

[Chris Hibner]

Your logic seems correct. However, you may not be getting anything from the ultrasonic sensor. See the attached image of the ultrasound example (the example can be found in (LabviewInstallFolder)/examples\FRC\Analog\EZ1 MB1010 Sonar Analog).

The example sets the averaging, sets sample rate, and then gets the voltage within the while loop. We tried moving the "set averaging" and "set sample rate" to Begin.vi, but the "analog get voltage" stopped working when we did that. Perhaps you need to add the "set averaging" and "set sample rate" into your while loop.


Can you describe the following:

1) How exactly is your robot behaving when you run autonomous?

2) When you run autonomous, what are you seeing from your "Distance" indicator?

[MotorHead]

I haven't used the Ultrasonic yet, so I can't comment on its setup. I do have a problem with your logic. The way you currently are configured is: If distance >= to 40 then back up with y =-.4, If distance < 40, stop and activate solenoid.

The problem with this is you do not have a deadzone in which to stop. Your arrangement can cause the robot to excessively hunt about the setpoint of 40. Look again at the vi I posted. There is a nested case structure to test if you are above or below the setpoint or if you are within the acceptable deadzone, in which case, do nothing.

[cilginbilgin]

Originally Posted by Chris Hibner

Your logic seems correct. However, you may not be getting anything from the ultrasonic sensor. See the attached image of the ultrasound example (the example can be found in (LabviewInstallFolder)/examples\FRC\Analog\EZ1 MB1010 Sonar Analog).

The example sets the averaging, sets sample rate, and then gets the voltage within the while loop. We tried moving the "set averaging" and "set sample rate" to Begin.vi, but the "analog get voltage" stopped working when we did that. Perhaps you need to add the "set averaging" and "set sample rate" into your while loop.


Can you describe the following:

1) How exactly is your robot behaving when you run autonomous?

2) When you run autonomous, what are you seeing from your "Distance" indicator?

After we put set averagıng and set sample inside the while loop the code seems to be working however there is a small problem. Let x inches be the distance I want the robot to stop and to extend the piston. When I set robots position to some distance which is greater than x inches and run the code the robot stops and extends the piston at x-y inches. If I set robots position to x inches from the wall and run the code the robot doesnt move and extends the piston as I want. Is there anything I can do to avoid this problem or should I just tell the robot to stop at x+y inches to make it stop at x inches?

Originally Posted by MotorHead

I haven't used the Ultrasonic yet, so I can't comment on its setup. I do have a problem with your logic. The way you currently are configured is: If distance >= to 40 then back up with y =-.4, If distance < 40, stop and activate solenoid.

The problem with this is you do not have a deadzone in which to stop. Your arrangement can cause the robot to excessively hunt about the setpoint of 40. Look again at the vi I posted. There is a nested case structure to test if you are above or below the setpoint or if you are within the acceptable deadzone, in which case, do nothing.

It doesnt back up it goes forward with negative integers.


Thank you guys for your helps!!!!!

[Alan Anderson]

Originally Posted by cilginbilgin

After we put set averagıng and set sample inside the while loop the code seems to be working however there is a small problem. Let x inches be the distance I want the robot to stop and to extend the piston. When I set robots position to some distance which is greater than x inches and run the code the robot stops and extends the piston at x-y inches. If I set robots position to x inches from the wall and run the code the robot doesnt move and extends the piston as I want. Is there anything I can do to avoid this problem or should I just tell the robot to stop at x+y inches to make it stop at x inches?

The robot is moving. Once you detect that you are at x and tell the drive motors to stop, the robot coasts to a halt y inches further on. You could set the motor speed controllers to "brake" mode so the robot stops immediately, though that can make driving it a little less easy.

Or you could control the motor speed based on how far away you are, slowing down as you approach the target distance so you don't overshoot. For example, set the motor output to a value proportional to the error between the desired location and the measured location. If your proportionality constant is too high, you will overshoot (and then perhaps back up to the target, depending on the details of the code). If the constant is too low, you will stop too soon, so you can use another term that increases motor speed based on how long the position error is present. You can also reduce power if you're approaching the target too quickly. Put it all together and you have PID control -- search the forums for more discussion and explanation.