Commit 00479e99 authored by David Preiss's avatar David Preiss
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## Week 3
[Here's video of the dyno running as of last night.]( I thought I remembered it being possibleto embed youtube/vimeo links directly into gitlab markdown, but it doesn't seem to be working atm.
This week all of the remaining subsystems came together (except for a thermocouple which I would like to add for some future sweeps) and I was able to generate some interesting data as shown in the plots below. Back in week 2 I sketched out an illustration of the sweep I was planning to make: Commutate at some constant RPM and then incrementally increasing opposing torque via the absorber. At each increment, measure torque via the load cell, RPM via the encoder, stepper voltage and current consumption via the INA260. For an open loop stepper, stepper voltage and current comsumption will remain relatively constant across the entire sweep, increasing slightly with increasing RPM. The product of these two will give us electrical power consumption. As torque increases, we eventually stall or backdrive the motor as shown in the video below. At this point we have acheived the peak torque output of the motor at that RPM. The plot (and V = L*di/dt) suggest that for a motor that is not acheiving steady state current consumption for an inductor, as RPM increases, max torque decreases, because we are not giving enough time for current to fully develop in the inductor before commutation occurs and we attempt to reverse polarity and therefore current direction.
We can also calculate mechanical power output at each increment by taking the product of torque and RPM. By dividing mechanical power output by electrical power input, we can determine motor efficiency across the entire torque speed curve. So our final plot shows us not only the standard torque speed curve (the interpolation of points spanning peak torque at each RPM), but also motor efficiency there as well.
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