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This thread is privately moderated by Jack Crossfire, who may elect to delete unwanted replies.
Dec 24, 2014, 11:27 PM
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Constant RPM drive




Whacked on the ages old 5V BEC to try to maximize the range, then tried constant RPM set to 500 or 9m18s/mile.




The result was higher speed going uphill than downhill, with the total speed in the 10minute/mile range. It must have been the lousy tracking of rpm.

Then of course, the range was reduced to 4.5 miles. The BEC was actually less efficient than straight PWM. As for measuring power independent of voltage, only the current feeding the BEC was measured, so the power would vary as the ESC efficiency changed at different voltages. The rough figures showed 15W on the downhill & 17W on the uphill.

Then, there were the usual software problems. Throttle always reset during fast turns & sometimes reset during slow turns. Acceleration was too slow. A faster tachometer is needed.

Ran all 9 miles looking at data on the phone. Probably need to capture the bluetooth data. During these long runs, a wish list topped by automatic path following always forms. Automatic path following can be reduced to a simple problem: determining what's 1 material & what's another material in an image. 1 material is usually asphalt. The other material is grass, gravel, or dirt.

The computer always knows asphalt is on the left & other stuff is on the right. It can get the color on the leftmost & rightmost parts of the image. Then it can work inwards until the colors change.
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Dec 25, 2014, 01:29 PM
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RickC_RCAV8R's Avatar
Jack :

Merry Christmas !

Forgive my ignorance for a moment about this constant RPM controller . I see what you are going after with the car . Is your drving circuit just a straight-up PWM modulator set for the proper pulse width ? A souped up 555 astable timer circuit or the like ?

I was thinking of trying something similar in a bicopter application with the V22 that I am currently finishing up . The idea is to use it for a better altitude hold . KK firmware is alright but the hold could be better . Also , IF one of thes guys were to be used for each motor , monkeying around with the SYNC between the modulators would allow for roll and yaw changes between the motors by timing . (Kinda long the lines of the optically timed units)
Any ideas here ?
Dec 25, 2014, 11:18 PM
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Copters have always used PWM modulators.
Dec 26, 2014, 12:16 PM
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RickC_RCAV8R's Avatar
Jack :

I am aware of the use of the PWM modulators . The SYNCing of them together is the question though . Apparently , if this is done , one can augment the roll and yaw by having the props slightly out of rotation with each other / angular acceleration (w) to induce this effect . Probably changing the angular Momentum of each prop . (Single fixed pitched props)

Thanx anyway .


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