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Legality of Jaguar closed-loop control modes
In an official Q&A answer just posted today, it appears that the Jaguar closed-loop control modes are now not considered competition-legal (see the specific question and answer from the GDC here.)
We're interpreting this to mean that ONLY voltage mode is competition-legal - which is surprising, as we'd previously understood that the essential safety feature of the FMS being able to disable Jaguar-controlled motors was achieved via the special heartbeat sent from FRC_NetworkCommunication, and thus completely protected from any team-written software going awry. Hence the reason for the FRC-specific firmware on the Jags - if the Jag doesn't see the FRC-specific heartbeat, it cuts off the motor output regardless of whether a closed-loop control in the Jag is trying to drive it or not. Due to the implications of this, we'd like to see if others in the community read this Q&A the same way we have, before we ask GDC for explicit confirmation. Please post your thoughts. - Ron Team #2607 controls mentor |
Re: Legality of Jaguar closed-loop control modes
I would post to Q&A before Tuesday so you can get an answer and continue working on your design. It is good to get advice from other folks, but the Q&A ruling is final.
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Re: Legality of Jaguar closed-loop control modes
I thought that was an ambiguous way to answer the question. Is the closed loop control command that does originate from the cRIO the command, or is the calculated voltage output the command? I find it hard to believe that they would make it illegal without outright stating it, so clarification is in order.
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Re: Legality of Jaguar closed-loop control modes
My interpretation is that you can send the closed loop commands from the cRio.
A Jag may not send closed loop commands to another jag. |
Re: Legality of Jaguar closed-loop control modes
We've posted a Q&A requesting explicit statement of which control modes are competition-legal.
- Ron Team #2607 controls mentor |
Re: Legality of Jaguar closed-loop control modes
The way I see it, the intent of these rules is to keep robots safe. Based on the technology, the cRIO needs to control the Jags so that the Field Management System can stop the robots. That is the point of the FIRST specific Jaguar firmware. All modes are safe and controlled by the FMS.
I expect the GDC will state that all modes are legal. -Joe |
Re: Legality of Jaguar closed-loop control modes
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Re: Legality of Jaguar closed-loop control modes
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The key word is command, not data. |
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Re: Legality of Jaguar closed-loop control modes
Ron,
I was under the impression that the heartbeat is to insure that something has not interrupted the CAN connection and therefore allow the Jaguar to continue to execute the last command received. This is something different than a disable command generated by the Crio either through internal firmware for a fault or as received from the FMS. Is this correct? |
Re: Legality of Jaguar closed-loop control modes
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A "bad" student could reprogram the Jaguars with entirely new firmware, but this would break several other rules. There would be no doubt that they were doing something illegal though, so I don't know why they bothered to mention it here. |
Re: Legality of Jaguar closed-loop control modes
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Since this "trusted heartbeat" is completely protected from interference - intentional or unintentional - from team software, it's this handshake between the protected FRC software on the cRIO and the FRC-specific firmware on the Jags that provides the required safety, allowing the driver station (or FMS when connected) to disable the Jag motor output, effectively negating any motor output "commands" that come from the team software on the cRIO or the internal control loops on the Jag. That's why the Jags require the special firmware when using CAN in order to be competition-legal. Quote:
To quote, adding my own emphasis: "There is no rule that prohibits the Jaguars from reading the values from the encoders, however note that Rule R49 requires that the ROBOT must be controlled by the cRIO." Here's a very plausible paraphrase (which is hopefully NOT what the GDC intends): "There is no rule that prohibits the Jaguars from reading the values from the encoders, however the Jaguars are only permitted to provide the values to the cRIO and all control calculations must be performed on the cRIO." Seems like we all agree it'd be non-sensical for the GDC to intend this - but it's unclear enough that we had visions of robots being wrongly declared illegal based on different inspectors' opinions. :eek: |
Re: Legality of Jaguar closed-loop control modes
ok so if we interpret this the strictest way possible ( where the jag cant independently make a decision about its output ) wouldn't the current/voltage protection( a jag will shut itself off if it over amps or the voltage gets under 6v) built in to the Jags break this rule?
I dont think that this interpretation is correct ( or will remain correct ). |
Re: Legality of Jaguar closed-loop control modes
The GDC has spoken, no closed loop control from the jaguar.
http://forums.usfirst.org/showthread.php?t=16326 Quote:
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Re: Legality of Jaguar closed-loop control modes
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Can someone ask on the First forum (it won't let me post) if this means that speed, current and position modes of the Jaguar are prohibited? If so, then there's no reason to use CAN bus. We might as well stay with PWM and the Victors. Heavy sigh... |
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