4 ms·

I find that this is interesting to compare with Pulse-Width Modulation[0], in which a system must alternate between OFF and ON at some proportion to "simulate"

I find that this is interesting to compare with Pulse-Width Modulation[0], in which a system must alternate between OFF and ON at some proportion to "simulate" a non-binary signal (i.e. 60% of the time if the signal is on ON and 40% it's on OFF, then it looks like, on average, 0.6 rather than the discrete 1.0 and 0.0). [0] https://en.wikipedia.org/wiki/Pulse-width_modulation https://en.wikipedia.org/wiki/Pulse-width_modulation

deleted 11y ago
[deleted]
fernly 11y ago
Re PWM, I coincidentally recently was reading "Magic Sine Waves"[0] by the irrepressible Don Lancaster. He's done a lot of development since that article[1] [0] http://www.tinaja.com/glib/sinquest.pdf http://www.tinaja.com/glib/sinquest.pdf [1] http://www.tinaja.com/magsn01.shtml http://www.tinaja.com/magsn01.shtml
ArkyBeagle 11y ago
With PWM, you lowpass filter the thing to ... something akin to DC then feed it to an A/D. It's all about approximating the area under a curve. They're everywhere - A/D are PWM, class D amps are PWM, power supplies...
snowwindwaves 11y ago
Two examples where I use bang-bang control for inflate/deflate valves on inflatable weirs[0] and open/close solenoids on hydraulic pressure units controlling hydraulic rams attached to pelton turbine deflectors[1]. But I calculate a pulse width - how long the valve should be opened for in order to correct the error. For a turbine deflector loop it might execute every 1s with a minimum pulse time of 50ms and a maximum pulse time of 1s. For the weir control it might execute every 60s with a minimum pulse time of 300ms and a maximum pulse time of 20s, because the weir continues to move after the output is de-energized and the response of the water level over the weir depends on the area of the body of water behind the weir. I set a gain that determines how long the output is energized (the pulse width) for a given magnitude error. In my case the actuators are still discrete so the signal stays as a pulse train, it is not filtered up to be a continuous time signal. [0]: https://www.google.ca/#tbm=isch&q=obermeyer+weir https://www.google.ca/#tbm=isch&q=obermeyer+weir [1]: https://www.google.ca/#q=pelton+turbine+deflector&tbm=isch https://www.google.ca/#q=pelton+turbine+deflector&tbm=isch

deleted 11y ago

[deleted]

fernly 11y ago

Re PWM, I coincidentally recently was reading "Magic Sine Waves"[0] by the irrepressible Don Lancaster. He's done a lot of development since that article[1] [0] http://www.tinaja.com/glib/sinquest.pdf http://www.tinaja.com/glib/sinquest.pdf [1] http://www.tinaja.com/magsn01.shtml http://www.tinaja.com/magsn01.shtml

ArkyBeagle 11y ago

With PWM, you lowpass filter the thing to ... something akin to DC then feed it to an A/D. It's all about approximating the area under a curve. They're everywhere - A/D are PWM, class D amps are PWM, power supplies...

snowwindwaves 11y ago

Two examples where I use bang-bang control for inflate/deflate valves on inflatable weirs[0] and open/close solenoids on hydraulic pressure units controlling hydraulic rams attached to pelton turbine deflectors[1]. But I calculate a pulse width - how long the valve should be opened for in order to correct the error. For a turbine deflector loop it might execute every 1s with a minimum pulse time of 50ms and a maximum pulse time of 1s. For the weir control it might execute every 60s with a minimum pulse time of 300ms and a maximum pulse time of 20s, because the weir continues to move after the output is de-energized and the response of the water level over the weir depends on the area of the body of water behind the weir. I set a gain that determines how long the output is energized (the pulse width) for a given magnitude error. In my case the actuators are still discrete so the signal stays as a pulse train, it is not filtered up to be a continuous time signal. [0]: https://www.google.ca/#tbm=isch&q=obermeyer+weir https://www.google.ca/#tbm=isch&q=obermeyer+weir [1]: https://www.google.ca/#q=pelton+turbine+deflector&tbm=isch https://www.google.ca/#q=pelton+turbine+deflector&tbm=isch