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praelian
08-12-2009, 03:11 PM
For those that participated in the mech-warfare arena, what wireless control device did you use--RC [2.4 ghz] TX/RX, zigbee (xbee), blue tooth, wifi? Any issues/lessons learned from using the particular device?

If this has been answered before, a link would greatly be appreciated!

Thanks in advance!

lnxfergy
08-12-2009, 03:43 PM
I used an XBEE pair. Regardless of what physical protocol and device you use, designing a reliable protocol on top of that will make the most difference. Sending poses directly to an SSC-32 over an xbee is probably a bad idea even though the XBEEs have a built-in resend.

Key points with any protocol:
1. Keep the byte count down. Issy ran at 38k4 baud, but only transmitted about ~10 bytes 30 times a second. Not eating up the entire channel's time means that the resend on the XBEEs actually has time to deal with lost packets. Most importantly here, have the poses local, just send directions on what poses to use (in other words, don't send individual servo positions over wireless, send higher level commands like walk forward, turn, speeds, etc).
2. Make it robust. Issy sends out a frame of "forward speed, turn speed, gun on/off, gun tilt servo, gun pan servo", and a checksum, all at 30hz. The checksum makes sure that a garbled packet doesn't send issy into a crazy pattern. The 30hz means that even if a few packets/frames get lost, we still have fairly decent data throughput.

-Fergs

praelian
08-12-2009, 03:51 PM
So you used an Xbee solution to send control commands but a wifi solution for the camera? I was looking at doing the same, but was fearful of any RF issues that may come up with the Xbee. Good to hear that it worked!

darkback2
08-12-2009, 08:30 PM
I had the good fortune? or was cursed, to have a PC mounted on my mech. So I was able to send both video and control data over wifi. Its a relatively reliable connection, but the computer a bit of a hassle...Mostly because i was doing more than just mech warfare, and had to split my time between mech warfare and artbots. Also I had an issue with people's computers jumping onto my network and taking my IP addresses. I think in the future we are looking to have a fix for that.

I may also replace the PC with a xbee to save weight, and switch out for an IP camera...

DB

Spartan001
08-13-2009, 08:12 AM
What are some ways that you can control a mech? Remote pc, xbee, wifi? and if so how would you impliment these control methods?:D:D:D:D:D:D:D:D:D:D:D:D:D

lnxfergy
08-13-2009, 09:58 AM
There is already a nearly-identical thread going: http://forums.trossenrobotics.com/showthread.php?t=3486

My thoughts, are posted there.

-Fergs

[Mod Note: I merged the threads together - thanks, Fergs! -A]