stevendhansen

6 ms·

1.
by stevendhansen 9y ago
Yes, induction machines do draw power in order to establish a magnetic field where as PM machines get it for "free" by virtue of the magnets. Also the torque production at zero speed is almost identical in induction machines vs. P
2.
by stevendhansen 9y ago
You are incorrect. Induction machines are often used as generators. My employer uses them almost exclusively in the generator configuration. The Lorentz force is symmetric; in the generator mode of operation the magnetizing flux vector lead
3.
by stevendhansen 9y ago
Fair point about the quality of the current measurement. I probably take that for granted because I usually don't have to hit low cost targets! But that being said, a flux observer is inherently doing some kind of integration which ten
4.
by stevendhansen 9y ago
The high freq signal has to be lower than the switching frequency - otherwise you end up with harmonic interference from the PWM like you mentioned. For high performance servo control in the 5-200kW range with switching frequencies up to 20
5.
by stevendhansen 9y ago
It is not easy per-se, and yes it is used in many dissertations, but most of the limitations up to now have been more related to the performance required to implement a demodulator that runs at high enough frequencies in a low cost microcon
6.
by stevendhansen 9y ago
The power electronics are built using MOSFET half-bridges, which naturally support the ability to flow current in either direction. This allows current to flow from battery to motor or from motor to battery (regeneration). In regeneration t
7.
by stevendhansen 9y ago
Very impressive! I love to see this kind of thing on HN. I scanned through your code a bit on mobile, and here are a few quick suggestions: 1) It looks like you are using field oriented control. This is used 99% of the time in industry, but
8.
by stevendhansen 9y ago
[spoilers] The first time I read Permutation City I really enjoyed the reveal that Paul was originally a simulation (many times over) that only existed in the "real" world because the entire universe spontaneously came into being
9.
by stevendhansen 9y ago
Seconded, Blindsight is one the best SF books I've ever read. "Imagine you are Siri Keeton..." Can't wait for the 3rd book (Omniscience I think?) to come out.
10.
by stevendhansen 9y ago
Expansiveness in that Three Body Triology takes place over a large period of time (billions of years), and the fact that it takes place over such a large space (Earth, Trisolaris, outer planets, etc). The ideas were similarly expansive, esp
11.
by stevendhansen 9y ago
Robert Zubrin has discussed the "moon first" strategy, and has made the interesting observation that many of the pro arguments come from entrenched space industries looking to make a buck on existing hardware. The argument being &
12.
by stevendhansen 9y ago
Different strokes I guess. I really enjoyed the Three Body Problem trilogy due its expansiveness both in time and in space, and its focus on ideas rather than (solely on) characters. Then again one of my favorites hard SF authors is Greg Eg
13.
by stevendhansen 9y ago
There has been some good discussion on Reddit about how the thrust results shown in the paper are still most likely measurement errors due to thermal effects. It is a shame that they haven't released their actual data for independent a
14.
by stevendhansen 10y ago
Well said.
15.
by stevendhansen 10y ago
With respect, the idea that most parents could fix the system if they just tried is incredibly naive. I think most parents do the best that they can. If they feel that homeschooling is better for their children then they absolutely should p
16.
by stevendhansen 10y ago
The big problem in my mind is that Python is the wrong tool for the job. It is 2016, there are more hard-RTOS prototyping platforms than ever before. My favorite is National Instrument's RIO platform, which lets you use C or LabVIEW (i
17.
by stevendhansen 10y ago
I have a guess: the limit in these designs isn't typically the motor, but instead the power semiconductors in the inverter (the motor has a much longer thermal time constant than the power devices). Therefore the limit is the junction
18.
by stevendhansen 10y ago
As pointed out in other comments Tesla actually uses AC induction machines (asynchronous AC) instead of brushless machines (synchronous AC). To a first approximation an AC induction machine can produce constant torque up to a fixed speed. A
19.
by stevendhansen 10y ago
Except it isn't just the spread of misinformation. Even more important (IMHO) is the insulating effect of showing people only like-minded opinions, effectively trapping everyone in a bubble. I can't think of any way Facebook can s
20.
by stevendhansen 10y ago
"...until you can come to a consensus that's acceptable to everyone." In my (admittedly anecdotal) experience, democracy rarely seeems to come to any consensus that is acceptable to everyone, but rather serves as little more
21.
by stevendhansen 10y ago
Reminds me of a book I recently finished (Death's End by Cixin Liu). A major plot element is sending a human brain to intercept an alien civilization that is en-route to Earth with the hope that the aliens will resurrect the person and
22.
by stevendhansen 10y ago
"our radically capitalist regime" Citation required. I'd venture the US is more accurately described as a hybrid socialist / mercantilist regime than a capitalist regime.
23.
by stevendhansen 10y ago
It can be both.
24.
by stevendhansen 10y ago
The only alternatives to privatization I can see are: 1) force the population to collectively pay for these services or 2) force specific individuals to provide these services for free Option 1 is morally questionable and option 2 is a type
25.
by stevendhansen 10y ago
One of my favorite books as well. Every time I've gotten to the ending (especially the part where they discover the massive sculpture through trillions of universes) my mind is blown and I end up sitting and thinking about it for hour
26.
by stevendhansen 10y ago
Just because controllers have proportional and integral terms does not mean they are PID controllers! I'm not just being pedantic here, there is a world of difference between a modern servo controller and a simple (or advanced) PID con
27.
by stevendhansen 10y ago
PID control is rarely used for professional servo applications, with the exception being amateur and lower performance systems (radio controlled, etc). This is especially true with PM servo motors because these machines are inherently nonli
28.
by stevendhansen 10y ago
PID is a generalized control algorithm that performs poorly unless your system is entirely linear. It is overwhelmingly used in industry, however, because it is simple, and anyone can drop in a PID block and adjust three constants to get se
29.
by stevendhansen 11y ago
The events of the last century have all but proven, in my mind, that the political process can do very little to change the political process.
30.
by stevendhansen 11y ago
Nope, by a stroke of luck Bitcoin uses secp256k1 instead, which is not included in Suite B.

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