Velocity Calculation rework #453
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src/common/base_classes/Sensor.cpp
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| const float delta_angle = current_angle - prev_angle; | ||
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| // floating point equality checks are bad, so instead we check that the angle change is very small | ||
| if (fabsf(delta_angle) < 1e-8f) { |
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Don't we want to check for angles larger than this, rather than smaller?
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Good catch, whoops! Should be fixed now.
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Hey, thanks a lot for contributing this. I think it is a good idea, as you have mentioned the unstable velocity signal is a real pain for many people. This seems like a very reasonable approach, but I'd like to merge it to the dev branch and try it a bit before releasing. So if its ok with you I would merge it immediately after doing the next release? |
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Merging after this release is totally fine by me! |
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Seeing the relatively frequent questions and problems associated with noisy velocity measurements on the discord server, what do you think about a change like this to the velocity calculation?
The idea being that currently when we make a call to
getVelocity(), if the angle change is zero then we get a zero velocity, if we have a non-zero angle change it appears as a very high velocity because all of that change is accounted for in one cycle. Because our loop can often run many cycles between angle changes. This shows up (unfiltered) as a series of zero velocity measurements with large single sample spikes, this is obviously nonphysical. The current fix to this is to heavily filter the velocity signal, which introduces a large phase loss in the control system.This change only updates the velocity if an angle change is observed and otherwise reports the previous velocity. This results in a closer approximation to a continuous signal.
One degenerate case that is not handled is if the motor comes to a complete and total stop, the velocity will not be reported as zero. Practically, this doesn't seem like a problem because the reported velocity will be very small, very few motors will come to an absolute stop for any long period of time, and a floating point zero value (vs very small non-zero) isn't actually very useful.
This change is currently untested on hardware.