Thread: Discussion ESC Response Testing
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Old Dec 01, 2010, 09:27 AM
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Quote:
Originally Posted by Arthur P. View Post
Would be interesting to see how the TWI/I2C modified ESCs and Holgers behave, whether they also show the same number of steps whether the difference between current and target throttle is large or small.
I agree also. This is an interesting test. It is worth to try it with my test machine , sending i2c controls instead of PWM. Now what controls should be applied, to best represent a Kopter behavior:

- 10%-100%
- 40%-60%
- 50%-70%
?

Quote:
If you know that the step proportion and thus the number of steps is fixed, then you can of course correct if you have a higher update frequency than the step rate. I.e. if you want to go from 50 to 60% throttle and you know the step size is 50%, sending a 70% throttle and then going back to 60% will get you to the 60% in a single step. What is interesting is that the motorsmoothing routine for the MK does do this for the downward steps, but works with fixed 50% steps upward.
Yes. And it makes sense to do it for downward first, as ESC response time is slow when going down. And I wonder if an ESC with Brake set, would behave correctly with that downward curve...

Quote:
My modified motor smoothing allows you to vary the motorsmoothing up and down by a different fixed percentage value for up or down. It might howevere be worth testing whether this shouldn't be changed to start off with e.g. a single current +/- 1.5 * (target - current) throttle input up and down, followed by the actual target input on the next iteration. That would pre-empt the slower ESC response for smaller throttle value changes, while for large changes max and min throttle would limit the initial step at some point.
I assume you are talking about FC + BL-CTRL with "current" feedbacked by the I2C. With PPM, there is no way to feedback current.

Quote:
Of course in real life the calculated target throttle may be incorrect due to vibration and other external disturbances, but if your update rate is much higher than needed, this will in a way be filtered out by the motor/ESC smoothing routines and the rapidity with which the next (maybe more correct) value gets calculated.
I see your points. But, in that case the refresh rate of the FC must be much higher than the refresh rate of the ESC itself. And also, motor rotation is not that quick, at full speed it takes 4msec for one full rotation.
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