Getting distance traveled from PID controller?

RoboticsConnection.com HomePage

RoboticsConnection User Forum

Home

Members

Calendar

Who's On

Welcome Guest ( Login | Register )

Getting distance traveled from PID...

Rate Topic

Display Mode

Topic Options

Author

Message

pirobot

Posted Saturday, May 31, 2008 11:08 AM

Forum Member

Group: Forum Members
Last Login: Wednesday, September 24, 2008 4:05 PM
Posts: 35, Visits: 142

Hi Jason,

I've checked the .Net documentation on the PID controller interface and it's not clear to me if I can get the distance traveled between any two points in time. In other words, suppose I command my robot to move 48 inches but part way through it has to stop because of an obstacle. I'd like to be able to read off how far it traveled before stopping. If I were doing it at the firmware level I could clear the encoder counters then read off their values when the robot stopped.

Thanks!
patrick

Post #525

Arnaud

Posted Monday, June 02, 2008 12:09 AM

Forum Member

Group: Forum Members
Last Login: Thursday, June 26, 2008 11:27 PM
Posts: 30, Visits: 306

I did a lot of tests with PID.I think if you stop PID with cmd stop or other, you can querry the counter value and convert ticks to inch(the counter is reset only if you send a new pid cmd "i think").

Regards

Arnaud

Post #527

jsummerour

Posted Monday, June 02, 2008 6:50 AM

Supreme Being

Group: Administrators
Last Login: Today @ 6:22 AM
Posts: 277, Visits: 407

Patrick,

As soon as you issue a PID command, the encoder values are reset. So, you can simply create two WheelEncoder objects, set their Resolution and WheelDiameter properties, and query their value as soon as you stop the robot to obtain distance.

Best Regards,

Jason Summerour
President,
Summerour Robotics Corporation
Microsoft MVP
www.roboticsconnection.com

Post #530

pirobot

Posted Monday, June 02, 2008 7:49 AM

Forum Member

Group: Forum Members
Last Login: Wednesday, September 24, 2008 4:05 PM
Posts: 35, Visits: 142

Thanks Arnaud and Jason! I don't know how I missed the WheelEncoder object--didn't think to look in the Sensors section of the docs instead of the PID section, though it makes sense that's where they should be. Now I am all set.

--patrick

Post #535

pirobot

Posted Sunday, June 08, 2008 6:35 PM

Forum Member

Group: Forum Members
Last Login: Wednesday, September 24, 2008 4:05 PM
Posts: 35, Visits: 142

Hi Jason,

I may have found a glitch in the WheelEncoder object. The Resolution property is typed as a byte which is too small to hold the resolution of the encoders I am using (US Digital encoders that mount to a Lynxmotion gearhead motor). The resolution for these encoders is something like 6250 ticks per revolution which won't fit into a byte. Even the 624-pulse resolution of the Traxster motors won't fit into the byte value. By contrast, the PIDMotorController Resolution property is typed as an int and so I don't have the same problem there.

Thanks!
patrick

Post #550

Arnaud

Posted Monday, June 09, 2008 12:24 AM

Forum Member

Group: Forum Members
Last Login: Thursday, June 26, 2008 11:27 PM
Posts: 30, Visits: 306

Hi,

I have same problem with WheelEncoder. I'm interested by this resolution and it is true when we use PID we don't have problem with encoder resolution!!!

Regards

Arnaud

Post #552