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Mechanical & Automation Engineering / Re: Paint Bubbles On Snowblower
« Last post by BrokenYugo on Today at 01:26:07 pm »I'd guess bad prep, rust under the paint type issues.
Couple of critical questions:
1) is the "perfect" situation that both motors equally share the load at all times and respond identically?
2) How Dynamic is the system. Ie if you applied full torque or full load, what is the maximum rate of change of rotational speed
The answers will dominate what the best control architecture is!
If we assume the answer to 1) is YES (50:50 share is ideal) and the answer to 2) is say 1 second to reach max speed from zero speed
then it's clearly going to be best and easiest to do external speed control, ie to calculate a total torque value, then just split this 50:50 and send out that half torque command to each motor, and you'll need to be able to do this at between 10 and 20 times a second in order to maintain sufficient control bandwidth
There are other options which could be possible but which very much depend on the system dynamics, for example putting both in local speed control mode, but calibrating the PIDs differently to avoid detructive interference (you can have one motor doing all the P and one doing all the I for example)
The other question is what is fundamental oscialtion frequency of the system, ie you say the drives are "elastic", what is the natural frequency of this and will you control system operate above or below it (it really can't operate IN this zone!) Now if the load is varriable, then that no-go control bandwidth zone can be quite wide, so care will be required. For most mechanical systems, it's generally preffered to be above the natural frequency as normally things get "less stiff with time / condition / load" etc
The final question is
"How critical is the speed control accuracy and convergence" Ie, At what point does it actually matter that the speed is "wrong"? If you're making a machine to stir custard, then clearly, you've probably got a lot of tollerance to varriable speed, but a system to drive an elevator full of people, less tollerance. As you know the application, you can make some qualified estimation of the errorband/deadband that your system can tollerate, and this will drive the mechanical and software/controls architecture as appropriate...
It's one of the most useless tools I have. It sucks at everything besides that it actually holds the board. The only way it's useable is if you insert TH components and bend the leads so they don't fall out before putting it in holder. Inserting while in holder is a no-go. Not to say soldering under angle means that solder tends to flow downwards, especially on large solder joints. Frankly board just laying on the desk works better.