pdf wrote:I have several questions, if anyone is following this thread. It looks like the no-load current, motor resistance, and "K" value uniquely specify the different motors.
justin_le wrote:then the winding inductance has a very large effect. A model that is based only on motor resistance and 'K' will show much higher power and torque values at speed than you would measure in practice. This gets more and more pronounced the higher the RPM that you are simulating at.
justin_le wrote:justin_le wrote:then the winding inductance has a very large effect. A model that is based only on motor resistance and 'K' will show much higher power and torque values at speed than you would measure in practice. This gets more and more pronounced the higher the RPM that you are simulating at.
To illustrate this point, the graph below shows how you would predict the performance of an eZee motor at 48V/20A if using only the motor constant 'K', the winding resistance, and the no-load current as your motor model:
Meanwhile, the actual data matches much more closely with the graph below, which has exactly the same parameters for R and Kv but where the effect of motor inductance and commutation events are taken into consideration:
Compare the predicted power output at 40 kph, the winding inductance reduces the output watts by more than a factor of 2. But at really low speeds, where the commutation period is significantly longer than the L/R time constant for the motor windings, then the two graphs converge and ultimately show the same stall torque.
swbluto wrote:Thanks for the illustration. I was recently under the impression that the caveat you brought up affected performance in the region of 5-10%, but it certainly seems to be fairly important.
By the way... can you tell me how the "commutation" period is so long at low speeds?
It seems obvious that the phases are activated for longer periods of time at lower RPM, but it also seems that you're encountering PWM at the lower speeds due to current limiting. Is the "commutation period" of the PWM waveform not particularly important (Once current limited has deceased at higher speeds, the PWM disappears and the phase waveform becomes the only one existent), and it's mostly just the phase current's period?
swbluto wrote:it doesn't seem easy to port to an online format without heavy bandwidth costs.
swbluto wrote:Ok, I've gone through the steps for licensing and dedicating an SVN space to the open source movement. This software is now GPL licensed and ready for open sourcing to allow improvement or modification to the software by anyone who wishes to contribute. All improvements and derivatives must be open source under the same license as part of the terms for GPL licensing.
The SVN is http://svn2.assembla.com/svn/ebikecalculatoropen .
If you just want to browse or have a look around the space, the url is http://code.assembla.com/ebikecalculato ... sion/nodes .
swbluto wrote:Change the built in 2d array for the motors so that it can read that information from an external CSV spreadsheet or some other database. This way, the motors can be added in the future without requiring compiling the program and so anyone could add motors to the motor database.
damcard wrote:swbluto wrote:Change the built in 2d array for the motors so that it can read that information from an external CSV spreadsheet or some other database. This way, the motors can be added in the future without requiring compiling the program and so anyone could add motors to the motor database.
How were you going to do this exactly? Would you have a folder with the files it could load? That is, where would the csv files be held? A form could be used to load custom csv's I suppose. If it is a hosted app or if it connected to a service I could see how users could add motors.
I ported Motor.java to Flash(as3). I will finish up the others once I can get read access to the repository and check out the entire project. Thanks -David.
wookey wrote:Could I ask that if people are going to make this into a flash application that they _please_ test it with/write it for Gnash and swfdec - the free flash applications. Currently flash is a real problem on the net because it requires Adobe's proprietary technology for much of it to work - that is not the sort of web we all want to be using (imagine where we'd be if 10 years ago there was only one web-browser available to us all, from one supplier and no-one else could write web-browsers because how stuff worked was not documented). I'd much prefer for it to remain a java application, now that java has been made a free language. flash is not searchable, flash is not link-to-able.
I found a couple of minor corrections in the help. I just tried to check the code out and fix these but it seems the help docs are not actually checked in. Is this just an oversight? Shall I do that? I've joined the project and it's set me to 'member' does that give me svn checkin rights?
They haven't exactly been too forthcoming in releasing the inductance data and it's not readily extractable from the graphs since "numerical estimation" techniques are used (LOL- in other words, no formula), so I guess they have the monopoly of "true performance" simulation and unfortunately doesn't include all the detailed vehicle analysis that I've come to love about mine (Like heat generation, acceleration, predicted speed given a defined hill and motor temperature and the such).
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