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Unread 21-01-2011, 00:38
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Re: Legality of Jaguar closed-loop control modes

I see no justification for this ruling within rule <R62>.

Quote:
<R62> All outputs from sensors, custom circuits and additional electronics shall connect to only the following:
A. other custom circuits, or
B. additional COTS electronics, or
C. input ports on the Digital Sidecar, or
D. input ports on the Analog Breakout, or
E. the RS-232 DB-9 RS-232 port on the cRIO-FRC, or
F. the Ethernet network connected to either Port 1 or Port 2 of the cRIO-FRC, or
G. the CAN-bus if and only if all Jaguar speed controllers on the CAN-bus are wired in full compliance with Rule <R58> and Rule <R59>, or
H. the sensor inputs on the Jaguar speed controller.
If they intended to use <R62-G> to justify the ruling by way of <R58> they should have cited <R58> directly. If they are not using <R58> as the justification then I see no part of this rule prohibiting closed loop control on the Jaguars. The Jaguars themselves are not "sensors", "custom circuits" or "additional electronics" as their output is permitted to be attached to motors which are not listed in this rule.


<R58> may provide some justification for such a ruling
Quote:
<R58> Each Jaguar must be controlled with signal inputs sourced from the cRIO-FRC and passed via either a connected PWM cable or a CAN-bus connection.
I would argue however, that any of the closed loop control modes are controlled with inputs sourced from the cRIO-FRC. Control of the Jaguar is provided through a combination of configuration parameters, setpoints and the heartbeat provided by the cRIO.

I'd have to imagine that the people that put all the time and effort in to support the closed loop modes in the three different languages have to be a bit frustrated right now. I see the blue box under <R62> as a giant vote of "no confidence" in the Jaguar firmware. If the GDC believed that the Jaguar firmware would shut off the Jaguar outputs when the robot was disabled, what harm is there in allowing teams to use the closed loop modes with a "use at your own risk" disclaimer?

Teams that spent offseason time working with the CAN bus and closed loop modes are also likely to be a bit aggravated. This type of thing is exactly the kind of transparency that people are asking for from FIRST. I don't think you would have seen any uproar about this if FIRST had issued a technology roadmap detailing what they were planning on opening when at the time they changed control systems. Then teams could have allocated their offseason time in a more applicable manner, perhaps practicing custom dashboards knowing that a laptop with a larger screen could be used, or offboard camera processing, knowing that COTS computing devices were going to be legal.
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