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Re: CIM Motor Failure
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Second thing, what is CAN? I've heard of it, but i have no idea hwat difference it makes, and why teams would choose to use it. If you send me in the right direction to find out what it is, that would be good too :) |
Re: CIM Motor Failure
Brandon,
What you describe is usually caused by mis-calibration of the motor controllers such that one motor is doing all the work on that side. However. since you changed the motor and the problem corrected itself, the motor seems to be the obvious fault. There are certainly other issues that can arise in dual motor transmissions. Often these relate to mounting causing higher than normal frictions on one motor. Although the CIM motors are fairly well insulated (note the fiber insulation on the armature in the photos), it is possible to damage a winding in manufacture. All indications are that the cool motor was not performing the same amount of work as the warm motor. Since the CIMs are sealed there is virtually no effective way to cool them. The majority of heat is built up in the armature. the only path for this heat to escape to the outside of the motor is through the end shafts, bearings and then to the end plates. Some heat can be radiated from the armature through the air to the magnet structure and case but this will produce very little cooling. As Richard stated above, these motors are designed for intermittent duty. Practicing for five minutes with a long cool down period is best. We are in training at the moment and require longer periods to achieve that result. The motor failure was the result of our aggressive schedule. |
Re: CIM Motor Failure
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Did you measure the free current of the "bad" motor, after it was removed from the system? Often a bad motor will draw more current than normal when running free. If you don't have a convenient way to measure it, see me at IRI -- I have a test set you can use. As Al pointed out above, it is difficult to cool CIMs. They don't have a flow-through path for cooling air, so the heat developed in their rotor assemblies stays trapped inside. The rotor heats up much faster than the case, so a hot case indicates a VERY hot rotor. In more quantitative terms, Al's "too hot for the finger" test indicates case temperature above 60 Celsius, and the pictures he posted indicate rotor insulation temperatures above 180 Celsius. I've been a motor guy for a long time. CIM's are some of my favorite motors because they can really take the heat. But even a CIM can be overcooked. Thanks for the cautionary story, Al. :) |
Re: CIM Motor Failure
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Several really good programming and control specialists haunt CD, but a thread titled "motor failure" might not attract their notice soon. CAN is an acronym for "controller area network". In an FRC control system with Jaguars, it is a two-way communication channel that enables both commands to and feedback from the motor controllers. |
Re: CIM Motor Failure
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Re: CIM Motor Failure
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(Be sure to read the thread as well as the papers) |
Re: CIM Motor Failure
While it doesn't usually seem to be a problem during competition since motors have time to cool, one thing we might try is adding a display to the driver's station that shows the motor temperature. That would be handy for practice and demos. Has anyone done this and if so what sensor did you use?
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Re: CIM Motor Failure
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Dale, you would be surprised at how hot motors get at conpetitions. Mostly during elims but i know my team had that problem last year. I am almost positive at FiM champs 67 was cooling down there robot with fans. Kinda ironic if you ask me ;) |
Re: CIM Motor Failure
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Richard- Unfortunately, we didn't get to do any post-mortem on the motor because we swapped it at spare parts desk during one of our regionals for a fresh one. It would have been nice to know FOR SURE that the motor was the root cause, or to know what exactly with the motor was the root cause, however in the heat of competition, this was not a priority. -Brando |
Re: CIM Motor Failure
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Re: CIM Motor Failure
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http://www.analog.com/en/mems-sensor...s/product.html We wired it via a resistor to the Analog card on the CRIO. |
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