Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

A CIM. It was moving too, not just stalled. We added a slow boost to make sure the flywheel was moving before allowing more power, so we were seeing Jag faults at half power around 800 rpm after awhile.
It had a really, really smooth maintain speed though...

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Mark,
800 RPM on the flywheel or the motor? My suspicion is the motor was heavily loaded and controller current on the Jag was approaching it's set point for current overload. Was this for the steering via moving flywheel of 2009? Of the designs I observed, some incredible forces were built up during steering moves.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

It's 800 rpm on the CIM.
This is a kinetic energy kicker from this year. It's geared to be capable of 5000 rpm, but we restrict it and normal operating speed is about 1600rpm from the far zone.
The magnetic fields collapse quickly when it kicks, but we didn't measure a dangerous pulse back into the Jag. Power to the CIM is stopped when it kicks.
The CIM didn't heat up more than slightly warm to the touch.
A combination of the back EMF and spinning up the flywheel is obviously stressful enough on the Jag to warm it up over time and put it close to the over-current. It didn't have any trouble maintaining speed, just on the ramp up.
I am surprised that over current was reached at half speed after a lot of stressful speed changes.
The fault point gradually dropped in testing as time and stress went on.

We had it playing golf at an SBPLI fundraising outing on Tuesday and it was operating from 300 rpm to 450 rpm without noticeable issues. It can repeatedly putt a golfball back into the box it came out of at 40 feet.


The 2009 flywheel for turning you're thinking of was one of our local teams (263 Sachem), and was powered by a victor that overheated and burst into flames before they redesigned the code to ramp up and not try to go full bore all the time. That flywheel was 22 lbs and they were spinning it a bit faster.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Unfortunately, I have never seen a spec on trip current on the Jaguar. My suspicion is somewhere around 60-80 amps sustained. I have no test data on this, just some observation. Of course, back EMF could be playing havoc with the low voltage sense.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

According to the documentation, the jaguar is designed for 40 amps continuous current. They can hold 60 amps for 2 seconds, and a 100 amp start current.
As found in the MDL-BDC24 Data sheet.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

FWIW, the CIM draws 68 amps at max power, according to its engineering drawing.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

If you are quoting this FAQ...
The Jaguar (MDL‐BDC) modules have a self protection feature that does not allow excessive current to be drawn. This feature protects both the motor and the motor controller from damage. The Jaguar (MDL‐BDC) module normally provides up to 40 A of continuous current to a heavily loaded motor. However, it is capable of providing much higher currents, but for shorter periods of time. Jaguar provides 60 A for up to two seconds and provides 100 A for approximately 0.2 s.

I read this as the current protect mode waits 2 sec at 60 amps and 0.2 sec at 100 amps. The stall current on a CIM is 129 amps. If this is an accurate statement, then Mark's experience could have been right around the 60 amp trip point. Remember that fault will prevent output for 3-4 seconds while flashing the fault LED.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Personally, I've experienced the jaguars holding the stall current of CIM's for a little under a second, easily about 100-110 amps (we were running 2 CIM's on 2 jags, so, bit of a voltage drop and thus lower curent). The .2 seconds wasn't even close to what I was seeing before the flashing red lights came on.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

We had a similar problem at Championships. We built a swerve drive using denso motors for steering and 2 cims per drive transmissions. Our students noted that we would lose partial power when reversing and it would continue until the stick was centered. We put our machine on blocks and noted the blinking Jaguars. We then replaced the Jaguars but to no avail. Finally we got a hold of the TI guy (sorry can't remember his name) and he basically told us that the Jags were faulting when we changed motor directions too quickly (This was happening even when the machine was on blocks). Said the cutoff was around 40 amps. No. our drivetrain does not have excessive friction in it everything is properly supported with ball bearing and properly tensioned and it was geared for intermediate speed. With that said our students swapped out the Jaguars at home to victors after verifying that our machine was still doing this and poof! Problem solved. It would seem that the Jaguars have some really neat features, but for some things, they are just too smart for their own good (or they are just too smart for us :) ). I think it would really help if they could raise that trip current for the fault protection. We didn't have any issues in 2009 with the Jaguar going into a fault condition, probably because of the Regolith playing surface.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

The internal breaker in the Jaguars is really annoying in my experience. It tends to trip faster than the PDB's breaker and stays locked off for 3 seconds continuously. A lot of teams rely on drawing more than 40 amps current for just a few seconds for various scenarios involving turning, pushing, etc. so running Victors in a drivetrain automatically gives you performance gains simply because you get more leeway with temporary high current scenarios.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Just to be clear, the Jaguar does not have an internal breaker. The internal micro is sensing the current and making decisions accordingly. The micro also decides to shut down output for the 3-4 seconds it is flashing the fault LED. This is likely to give the FETs a chance to shed some heat.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Are you saying you had 8 CIMs on your vehicle?

(2 CIMs/trans * 1 trans/wheel * 4 wheels/vehicle = 8 CIMs)

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

I believe 368 built a coaxial swerve drive with two transmissions for four wheels.

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Just as a suggestion, if you are using CAN (and thus Jaguars) then the fault timeout can be reduced to 0.5 seconds.

Obviously, if your mechanism is pulling so much current that this happens fairly often a redesign could be a good idea (as reducing the timeout leaves the jaguar with less time to cool its FETs).

Re: Denso Window Motors, Warning - Don't use with Jaguars !
 

Justin,
While this might be a good idea in some designs, I would not suggest it for FRC robots. If a fault is occurring, you may not know it without also programming to watch for fault status. Should someone be trying to diagnose a problem, they would not have the added status of the fault light and timeout to see where the problem is occurring.