Jaguar Meltdown

[Peter H]

Our team (1606) had an interesting night tuesday when one of our jaguars released a plume of smoke while driving, all wiring was correct and the replacement jaguar is doing fine so we hope its just one that was faulty. upon further inspection after taking it apart it appears one of the power transistors had completly melted and began melting a second one and there were burn marks in the casing. has anyone else had this problem? pictures to follow...

[Urban Hawk]

here is a site for you to look at:http://tom-tech.com/first/wiki/images/a/af/JaguarGettingStarted.pdf
there is a possibility the airway was blocked causing it to overheat.
also make sure you cap the PWM value using the calibration procedure listed in the document so it isn't at full.

[Peter H]

airway was completly clear and our team leader says the pwm wasnt a problem. heres what it looked like...

http://i149.photobucket.com/albums/s42/Cadet44/Robotics/Picture001.jpg

http://i149.photobucket.com/albums/s42/Cadet44/Robotics/Picture002.jpg

after this the fan was checked and was still working fine

[JBotAlan]

Just pointing out the obvious--traditionally, Victors have failed because teams have gotten metal shavings inside them; the team I was on as a student included. Are you absolutely mega-sure that this didn't happen? It is very easy to do, especially if the person with the drill doesn't fully realize the potential for disaster...

As for the team I'm with now, we haven't had the robot moving much at all, so we haven't put our Jags through their paces. If one of them self-destructs, I will definitely post back here.

You may wish to contact FIRST if you believe this failed under normal circumstances.

Jacob

[Urban Hawk]

the picture that you had on there is a victor.... not a jaguar. here is a document i found online that may help you:
http://www.robotmarketplace.com/V883UsersManual.pdf

p.s. that is a bad picture of it

[JBotAlan]

the picture that you had on there is a victor.... not a jaguar. Im going off to find another document to help you... hold on

This (http://www.chiefdelphi.com/media/photos/24374) is a Victor. What was posted definitely is not.

[Peter H]

Just pointing out the obvious--traditionally, Victors have failed because teams have gotten metal shavings inside them; the team I was on as a student included. Are you absolutely mega-sure that this didn't happen? It is very easy to do, especially if the person with the drill doesn't fully realize the potential for disaster...

As for the team I'm with now, we haven't had the robot moving much at all, so we haven't put our Jags through their paces. If one of them self-destructs, I will definitely post back here.

You may wish to contact FIRST if you believe this failed under normal circumstances.

Jacob

absolutley we always cover all electronics when we do anythiong and we didnt find any foreign material in it when we opened it

[kc2pix]

Same thing happened to us!
(sorry the picture is bad. the burnt one is on the left)

7352

[JBotAlan]

There's now 3 separate incidents that I see where a Jag has blown; two on this thread and one here (http://www.chiefdelphi.com/forums/showthread.php?threadid=73830). I hope that this is the end of it, not the beginning.

Better contact FIRST. You could ask on the Q&A, or e-mail them (unless someone else has a better suggestion).

Meanwhile, it's probably best to go back to basics if you can--use Victor 884s. They've been proven. Too bad there's not more of them in the kit this year.

Jacob

[Urban Hawk]

i have the manuals for the speed controllers so here they are:

for jaguar:http://tom-tech.com/first/wiki/images/a/af/JaguarGettingStarted.pdf
for victor 884:http://www.ifirobotics.com/docs/ifi-v884-users-manual-dec04.pdf

looking at them the most likely problem may have been wiring since that seems to be one of the best ways when it comes to wrecking a victor so id suggest looking at the wiring guidelines section for the victors since it does list at the end several things you shouldn't do. For jaguar there isn't much on the manual about faults however on the first page there are 3 warnings of things you shouldn't do.

[dbeck103]

Being one of the beta teams we had one do exactly what you had happen - it smoked the transistor - Since then we have had two other failures. Luminary Micro has been great about replacing them and trying to determine why they are failing. Ours both failed in drive mode. Please contact Luminary Micro for help if you have failures.

[Al Skierkiewicz]

This is the destruct problem with conductive debris. Remember that the full power supply is available on the FETs when the power is turned on. If a chip should contact the Source and Drain pins on one FET 12 volts will cause full current to flow limited only by the action of the breaker feeding the controlller.

[Racer26]

I am currently holding in my hands a Jaguar that smoked about 90 minutes ago, and looks inside very similar to the above pictures. Upon disassembly, no obvious metal debris is present. Email already sent to LM for RMA.

EDIT: upon closer inspection of the above pictures, this one also appears to have smoked the chip on the lower right edge of the ring of FETs.

[Dad1279]

This is the destruct problem with conductive debris. Remember that the full power supply is available on the FETs when the power is turned on. If a chip should contact the Source and Drain pins on one FET 12 volts will cause full current to flow limited only by the action of the breaker feeding the controlller.

I think there is more going on here. We have not smoked a victor in 6 years, always very careful. Today we mounted a Jaguar, never drilled near it, and it smoked after less than 5 minutes of operation. No way there was debris in it, unless it was left over from manufacturing.

I will contact Luminary Monday, and send it in.

[Al Skierkiewicz]

Dad,
It is common for debris to vaporize in this kind of failure. So it is next to impossible to determine whether there was something or not that a foreign body was the cause. Make sure to contact luminary and return it. They are doing forensics to determine failures at this point.

[MrForbes]

Al--With the plastic piece surrounding the pins of each transistor, it looks pretty unlikely that a shaving could short the pins. It might be able to short the mounting tab of one transistor to another, or to some other part of the circuit.

[Al Skierkiewicz]

Jim,
It would look that way but on closer examination you will see that the plastic has sufficient clearance between the FETs and the plastic to allow chips to fall into that area. Also the shroud is tapered on the bottom side so most of the pin area is exposed. The shroud only touches the board at the outer edges.

[MrForbes]

It's possible, but it still looks unlikely. The openings in the top of the case are very small, the gap between the transistor and the plastic part is very small, so it seems that for a shaving to get in there, it would have to be so small that it would not be large enough to short the pins together. There are other ways for electronic components to fail, than to be shorted by foreign matter, aren't there?

That said, we haven't had any problems, we've been using 4 Jaguars since the end of December. We also haven't been doing any drilling of metal above them, since they're located in a wooden enclosure that is mounted vertically and has it's opening facing away from the rest of the robot.

[Al Skierkiewicz]

With the shape of the shroud, there are large open spaces between transistors and lots of turbulent air under the fan to push chunks around and into the FETs along with vibration running hard wheels on hard floors. When in place the underside center of the shroud is almost 1/4" above the board.

[Gdeaver]

This may not be debris. This year with the slippery wheels, a jag can go from full forward to full reverse in a very short period of time both electrically and mechanically. This could be a problem with them dealing with back EMF. Does any body know what FET they are using? While modern FETs are tough, the intrinsic diode can be the weak point and when the diode blows FETs look allot like the picture. Didn't the victors have a separate diode to deal with back EMF? Does the Jag? I've noticed that some high power drives that can handle these surges use a special type of MOV to soak up and dissipate the energy from a rapid reversal. Other speed controllers that are used for battle bots warn to allow a time period before applying a reversal. Also, the jags thermal sensing is not part of the FETs and can not react real fast. There are drives that are based on intelligent high side switches that have current and thermal protection built in to the package. It's a more difficult design when using multiple FETS per leg of the H bridge, however they are much tougher. Our team is using a joystick rate of change filter that gives a pronounce decay and ramping up when the driver changes direction rapidly. If jags have the back EMF problem, our filter should help allot.

[Alex Golec]

In keeping up with current events, we had the same problem today.

We caught the problem early on, but the Jaguar had already failed at that point. We could smell "warm plastic," and when we disassembled the Jaguar in question, the smell was confirmed: the plastic around one of the FETs had begun to melt.

There were no metal chips to be found, and I have no reason to believe any would have ended up in there. In our testbed, this Jaguar was mounted sideways on a panel above all driven components, and had been opened up fresh out of the box the night before. This was in regular use (http://www.youtube.com/watch?v=FkuxZKA6Cl0).

Hopefully we'll be able to find the source of the problem since this Jaguar is nowhere close to incinerated. I'll be in discussion with Luminary.

[AV_guy007]

the picture that you had on there is a victor.... not a jaguar. here is a document i found online that may help you:
http://www.robotmarketplace.com/V883UsersManual.pdf

p.s. that is a bad picture of it

That is actually the inside of a jag as stated by others, but more importantly you linked to the Victor 883 manual. While they are similar to the 884 they have differences and are not legal this year. I just wanted to point that out so no one sees that and uses 883's on their robot.

[Al Skierkiewicz]

Gary,
The FET used in the Jaguar is a Fairchild FDP8874. Thanks to Scott and the Luminary folks for being so open and providing schematics and descriptions. HEX Power FETs all have a diode that is a fall out of the manufacturing process as I understand. The Fairchild device has a few better specs than the IFI devices in that the On resistance is a little lower, the current rating is a little higher and the gate switching time is a little faster. The diode is speced for a voltage drop at 40 amps so I would guess the diode can handle more than that. With three in parallel, they should handle any current the motor could back feed into them during a motor reversal.
In the one post above about a single FET melting the plastic, I would suspect that the one device had just reached the temperature of the plastic melting point while the others were not far behind. This could easily be a difference in cooling fan flow or contact with the transistor tab. Remember that the IFI Victor did not contain plastic near the transistors so users would have nothing to indicate that the devices were at elevated temperatures without touching them. Luminary is trying to research all the data from the field so it is important to report as much data as you can about the device and it's use at the time of failure. This is a daunting task to sift through what might be actual failure from what might be abuse. Remember that we have had abusive failures every year we have used IFI components. Try as they might, manufacturers can only try to design to minimize abusive failures. There is significant diminishing returns to this equation though. "Make it foolproof and only a fool will use it", as the old saying goes.

[Team2191]

Where should we send broken Jaguars?

[the man]

Dont take the conecter screws all the way out they can get metal shavings in there wich is most likly what happened. It happened to us twice last year and other teams with six of them had no problems, we were taking the screws all the way out and it would scrape some of it off leaving metal shavings in the jags...Not fun stuff. :ahh:

[zahara3]

can some one tell me if we are still allowed to use victors or not? thank you

[seannoseworthy]

Where should we send broken Jaguars?

You can find instructions here (http://forums.usfirst.org/showthread.php?p=37077#post37077) on how to RMA a jaguar.

We had this exact same problem last year. In the report Luminary Micro released. They say the problem is Excessive heat in MDL‐BDC MOSFET(s) with the symptoms of Excessive current draw by MDL‐BDC with the visuals of Single low‐side MOSFET melt‐down with damage to plastic ring Possible blown or fractured PCB traces. To prevent this Luminary Micro reccomends Mitigate risk for swarf (for example, avoid using ring terminals; take extreme precaution when creating metal debris), avoid positioning module for direct impact vulnerability during competition.

Two days ago we had another Jaguar fail the status led flashed red and BDC-COMM reported a VOLTAGE BUS error. Which is most likely "Voltage regulator Failure (REG): Failures of the 3.3 V or 5.0 V linear regulator could be due to one of two conditions. The most likely root cause is excessive current draw from the power rail at the interface connector. The regulator is specified to shut down internally under these conditions; however, our testing has shown that this regulator feature does not work correctly. The second possible root cause is input over-voltage. The regulators have a maximum input voltage of 15 V, which is reflected in the absolute maximum rating of the Jaguar module. Bench tests have shown that the regulators function beyond 15 V with no degradation or failures at less than 17 V. Although there is no measured data showing DC supply voltages greater than 15 V, there is speculation that the supply could exceed this under certain regenerative conditions. Efforts to replicate this failure on the bench using a motor in full-regeneration were unsuccessful. Despite lack of correlation with bench testing, this is the only reasonable explanation for certain regulator failures, and because of the range of installations, not every condition can be reasonably replicated. Luminary Micro will use a regulator with an increased voltage range and functional over-current protection in future revisions of this design."

-Sean

[Dad1279]

We bricked one tonight just updating the firmware.

We really wanted to take advantage of the features this year but the reliability is frustratingly unacceptable.

Ready to throw on the towel and dust of the reliable 5 year old vics....

[Al Skierkiewicz]

can some one tell me if we are still allowed to use victors or not? thank you

Yes, you may use Victors. From Sec 8, Rev E

<R42> Items specifically PROHIBITED from use on the ROBOT include:

D. Motor speed controllers other than Innovation First, Inc. “Victor 884” speed controllers or Luminary Micro/Texas Instruments “Jaguar” (MDL-BDC or MDL-BDC24) speed controllers,

[seannoseworthy]

We bricked one tonight just updating the firmware.

We really wanted to take advantage of the features this year but the reliability is frustratingly unacceptable.

Ready to throw on the towel and dust of the reliable 5 year old vics....

If the firmware is corrupt, you may be able (http://www.luminarymicro.com/component/option,com_joomlaboard/Itemid,92/func,view/id,7307/catid,5/) to fix it with the JTAG port on the bottom of the device it will be coverd by the sticker. Flash it with the newest firmware found here (http://www.luminarymicro.com/index.php?option=com_remository&func=download&id=1359&chk=29b2134cf76a5b860e5b27f5b5af429f&Itemid=591). You would want to use this (http://ca.mouser.com/ProductDetail/Texas-Instruments/MDL-ADA2/?qs=vnwGVgFuQiYlhwR1LjkswQ%3d%3d) cable or a similar cable to flash the firmware.

PM me if you want to sell me your jaguar with corrupt firmware

-Sean

[dyanoshak]

We bricked one tonight just updating the firmware.


Check this thread out: http://www.chiefdelphi.com/forums/showthread.php?p=906884#post906884

If you accidentally load the Gray Jaguar firmware on a Black Jaguar, or vice-versa, they will not operate. The post I linked to describes how to fix the problem.

It is a good idea to download the latest firmware from www.luminarymicro.com/jaguar (http://www.luminarymicro.com/jaguar) to make sure you have the right ones.

-David

[Phoenix.14]

We experienced this with two of our jaguars in close succession; one of them burned and produced smoke, and had a similar melted plastic piece when we opened it up. The other stopped working just after and produced similar behavior to that of the burned one (running at full speed nonstop, even when the PWM wasn't plugged in), but we haven't opened that one up yet.

Fortunately we still have four working jaguars, so barring another failure we'll be fine.


There is a possibility that there could be metal shavings in the jaguar as we drilled holes in the metal board they were mounted to that day, but they were mounted upside down on the bottom of the board, so I find it doubtful that they would have gone into the fan opening.

[Dad1279]

Thank you David.

Phoenix - Shavings are the death of speed controllers. They are the last thing mounted on our robot.

[DonRotolo]

There is a possibility that there could be metal shavings in the jaguar as we drilled holes in the metal board they were mounted to that day, but they were mounted upside down on the bottom of the board, so I find it doubtful that they would have gone into the fan opening.
I have proof that metal shavings can defy gravity.

Make sure the gorillas in Mechanical understand the impact to the electronics of their work with their stone knives, axes and drill bits. ::ouch::

[3286]

While we are a rookie team and we make it a point to search posts and threads for information, we have noticed a kind of disconnect in some of the documents and references regarding the entire build process, especially in some of the seemingly more important DO's and DONTS! The mechanical and electrical side of building are of course easier for many, since they are not as abstract as programming and electronics for a lot of people, but this is the second time I have seen reference to calibrating Jaguars. Yet I did not notice this in any of the quick build or First provided reference.

We aren't complaining or throwing stones here even though it may seem as such, just stating an observation that may be taken for granted by more experienced teams since they have already been thru the steeper parts of the learning curve.

Probably everyone is getting a bit tense and anxious with only about 3 weeks left in the build season!

Good luck everyone, hang in there

Mike

[Al Skierkiewicz]

Mike,
Calibration of both Jaguars and Victors is a step that many teams do not take. The assumption is that the controllers are shipped pre-calibrated from the factory. In reality the calibration procedure matches your joystick travel to the maximum output of the controller. This step can be accomplished in software or a simple procedure in the controller. Without this step, your robot may not meet full throttle at each extreme of the joystick (or whatever you use to drive) or more importantly, it may not be matched for both forward and backward motion. In extreme cases the motors may not be at zero throttle when the joystick is at rest.

[Dad1279]

Check this thread out: http://www.chiefdelphi.com/forums/showthread.php?p=906884#post906884

If you accidentally load the Gray Jaguar firmware on a Black Jaguar, or vice-versa, they will not operate. The post I linked to describes how to fix the problem.

It is a good idea to download the latest firmware from www.luminarymicro.com/jaguar (http://www.luminarymicro.com/jaguar) to make sure you have the right ones.

-David

Worked. :)

[Joe Ross]

Mike,
Calibration of both Jaguars and Victors is a step that many teams do not take. The assumption is that the controllers are shipped pre-calibrated from the factory. In reality the calibration procedure matches your joystick travel to the maximum output of the controller. This step can be accomplished in software or a simple procedure in the controller. Without this step, your robot may not meet full throttle at each extreme of the joystick (or whatever you use to drive) or more importantly, it may not be matched for both forward and backward motion. In extreme cases the motors may not be at zero throttle when the joystick is at rest.

This is probably straying off-topic for this thread, but I don't think calibrating the speed controllers is wise in most situations.

Ever since autonomous started, joysticks haven't been the only thing controlling the robot. If you calibrate the speed controller to match a bad joystick, you will adversely affect the performance in autonomous mode.

Furthermore, the centering of the joysticks should not be an issue with the NI control system. Modern joysticks automatically calibrate the center position. Thus, you should not plug the joystick or enable the robot with joysticks off center. Any students should be familiar with this, as video game systems have had the same limitation since the N64.

If you really do want to use a particularly bad joystick, I think you're far better off compensating in software only during teleop.

If you have a speed controller with calibration that doesn't seem right, you should calibrate it with an autonomous routine that outputs -1, 0, and 1. Additionally, WPILib (in all languages) has it's own calibration values for min, max, center, and deadband, so you can adjust those for a particular speed controller. In java, it's the setBounds function.

[Darkknight512]

Just had a jag blow today, looks like the same problem from the picture. We are a rookie team, a little behind havent cut a single peice of metal except the original frame but when that happend the electronics board was not even assembled yet.

[Mike Copioli]

Just had a jag blow today, looks like the same problem from the picture. We are a rookie team, a little behind havent cut a single peice of metal except the original frame but when that happend the electronics board was not even assembled yet.

There are several possible causes for the failures occurring with the Gray Jags. The obvious afore mentioned causes are a result of conductive particulate (metal shavings) entering the housing and shorting across one or more legs of the H-bridge. This is an issue with both the Jags and the Victors. The Victors however have additional protection from this debris in the form of conformal coating. While this conformal coating protects the device at the surface component level it provides little or no protection to the FETs that make up the H-Bridge. This is unavoidable in both brands of speed controller and the major contributer to failures. These failures can be prevented by adopting practices and mounting techniques that reduce the risk of foreign body intrusion.

Other failures that I have observed can be attributed to ESD. There are a couple key elements to switching the H-bridge circuitry safely. The switch must occur in a way that prevents the high side of the bridge from saturating (switching on) while the low side of the bridge is saturated. This would cause what is called shoot-through and is basically a direct short between battery positive and battery negative through two legs of the bridge. This switch timing is controlled by a microprocessor inside the device. While the timing of the switch is most likely not the cause of the shoot-through, the driver circuitry that allows the NFETs to switch the positive side of the bridge failing is. This device is called a charge pump and what it does is very simple. A charge pump takes an input voltage and steps it up to a higher voltage. This higher voltage is what drives the gates of the High side NFETs. Why am I explaining all of this? very simple. One should understand how the device works in order to understand how it fails. After examining several Jags that have failed I have made a few discoveries, first and foremost the charge pump chip that is used in the gray Jags appears to be sensitive to ESD. In a one instance the chip had a hole blown through it. This happened shortly after a lightning bolt jumped from the bot to a desk. A charge pump chip that fails to do its job and or latches up can and does cause shoot-through. A second discovery revealed that the fans used in the gray Jags do not tolerate shock and vibration very well. Two of our failures are attributed to the struts breaking off of the fans after traveling over the bumps a couple of times. A loud rattling sound soon followed. In all cases the devices were free from debris and foreign body invasion. Many of these issues claim to be resolved in the Black Jaguar. Some of the changes that I have noted between the black Jaguar and the Gray are increased input voltage range, more ESD protection, and 4 less FETs (one per leg). The FETS used in the black Jags also have a higher continuous Drain current rating. This year our team is using Black Jags primarily due to these hardware changes. We have used the Victors in years past but made the switch to the Jags because of the legality of CAN in this years competition. Most of the failures can be repaired if you know what you are doing and have the ability to solder and remove surface mount and through hole components. I am not sure how legal this is but we are only using the gray Jags for the practice bot so it is irrelevant to us.

[T3H_K3YM45T3R]

My team has had 3... 4 jags fail now, and we're going back to victors. I don't think we will be using jags again. We fried 1 last year and this year we fried 3, they replaced the one we fried last year at the Greater Kansas City regional last year... we didn't burn it up at the competition, but had it with us for no reason.

the first one that fried this year "Popped" when it went out, I think the capacitor (big blue thing in the middle, for those that don't know) might have blown. It sounded like a capacitor shorting or "firing"

... I don't know if that helps or anything

[Liu_yiang]

Ours had the same problem. This seems to be a continuing problem with Jaguars. One can only go in reverse, one can't go at all. Last year, we had all four of them go out at once. We love our victors...

[boomergeek]

Team 241 had 3 Jaguars short out this year:
All resulted in the circuit breaker on the associated Jaguar breaker trip continuously that made the rest of the robot uncontrollable- (caused variable lag time of one to three seconds on all other functions on the robot).
We guessed that the failure mode was caused by voltage spikes caused by attempts at wide voltage swings too quickly.

One failure occurred at BAE unveiling event ; (less than 5 minutes total use prior to failure)
One at the Granite State Regional ; (less than 10 total minutes use)
One at the Connecticut Regional ; (less than 40 minutes total use)

The first two were on our drivetrain (CIMs).

The last on was on our ball magnet roller (Fisher-Price).

At Manchester, we added a software control to limit the rate of voltage change so that the Jaguar would not be swung from +12V to -12V too quickly (and vice versa).
Since we make that change, no more the Jaguars blew on the drive train- Because we had 2 blow out of 40 minutes total use (10 minutes times 4 CIMs) and we have not had any more blow after 240 minutes total use- we think the workaround helped.

But due to an oversight, our software workaround to baby the Jaguars did not get put on the Jaguar driving the fisher-price until after we blew another Jaguar.
After we put the software workaround on the roller, we have not had another Jaguar blow. (16 minutes use without a failure).

[eugenebrooks]

That your mitigating measure resolved your problem is consistent with the Jaguars being sensitive to the high currents produced when the motor is turning in the opposite direction than the polarity of the voltage drive. When this happens, the motor is effectively a generator aiding the battery to drive the current, instead of opposing it as is normal, producing a current surge while the condition persists. Victors are subjected to the same current assault upon sudden reversal of the drive, but are perhaps more hardy.

As opposed to limiting the "rate" of the "voltage change," it might be useful to account for the fact that the control of the victor is pulsed, on or off with a direction, and that there is a braking option selected via jumper when it is off. What you want to do is put in a short delay on "reversal" of the control signal, holding it at zero during this time, so that the braking will slow the motor down a bit before the drive reverses. This measure would help protect victors as well. Your slowing down of the rate of the change in the drive is having a similar effect, but the currents during the "on time" of the jaguar while the motor is reversed are still excessive.

Eugene



Team 241 had 3 Jaguars short out this year:
All resulted in the circuit breaker on the associated Jaguar breaker trip continuously that made the rest of the robot uncontrollable- (caused variable lag time of one to three seconds on all other functions on the robot).
We guessed that the failure mode was caused by voltage spikes caused by attempts at wide voltage swings too quickly.

One failure occurred at BAE unveiling event ; (less than 5 minutes total use prior to failure)
One at the Granite State Regional ; (less than 10 total minutes use)
One at the Connecticut Regional ; (less than 40 minutes total use)

The first two were on our drivetrain (CIMs).

The last on was on our ball magnet roller (Fisher-Price).

At Manchester, we added a software control to limit the rate of voltage change so that the Jaguar would not be swung from +12V to -12V too quickly (and vice versa).
Since we make that change, no more the Jaguars blew on the drive train- Because we had 2 blow out of 40 minutes total use (10 minutes times 4 CIMs) and we have not had any more blow after 240 minutes total use- we think the workaround helped.

But due to an oversight, our software workaround to baby the Jaguars did not get put on the Jaguar driving the fisher-price until after we blew another Jaguar.
After we put the software workaround on the roller, we have not had another Jaguar blow. (16 minutes use without a failure).

[boomergeek]

Eugene,

Thanks for giving a more accurate description of the surge from the reversal of directions being better described as a current surge rather than a voltage spike. I believe our Jaguars had been set up for "brake" instead of coast option from the beginning of the season. (Before the two failures).
We have been using CAN control signaling.

I'm relatively new to FIRST (my second year). And I was kind of surprised that neither the speed controllers themselves nor the standard software for driving the speed controllers had sufficient defensive measures for preventing a full speed motors in one direction (with the momentum of a robot traveling 10 fps) being instantaneously subjected to full voltage in the reverse direction.

Overly sensitive joysticks can excite this problem ... as well as novice drivers that have no concept of electrical and mechanical stresses that occur when they forget the concept of the momentum for a 135 lb robot and instead try to reposition a robot as quickly they would an avatar on a video game. ;)

[Joe Ross]

I'm relatively new to FIRST (my second year). And I was kind of surprised that neither the speed controllers themselves nor the standard software for driving the speed controllers had sufficient defensive measures for preventing a full speed motors in one direction (with the momentum of a robot traveling 10 fps) being instantaneously subjected to full voltage in the reverse direction.

While not enabled by default, when using CAN you can set a voltage ramp rate.

[Al Skierkiewicz]

Dick,
We rarely will suggest "brake" mode be used on drive motors. In low center of gravity robots it is not as dramatic as in high center of gravity robots like last year. Brake mode will usually tip a robot over.

[boomergeek]

Dick,
We rarely will suggest "brake" mode be used on drive motors. In low center of gravity robots it is not as dramatic as in high center of gravity robots like last year. Brake mode will usually tip a robot over.

Tipping can even be an issue this year.
Our tall stylish robot helped get us an imagery award in Connecticut this weekend and had the crowd on the edge of their seats when it does a 2-5 foot reverse front wheelie coming over the bump. (But not a single rollover thanks to our driver). "FLOOR IT coming down the hill until all four wheels are back on the carpet!"

We used the voltage rate change of the CAN control.
The use of brake mode was an experiment by our programmers that made it in early in the season and never really got a good A vs B comparison.