A PWM controller is bang-bang. Just means that the active drive has two states. The (usually) linear response of the system is provided by some kind of low-pass filtering in the controlled device. PID is a type of protocol used in the feedback loop. The feedback has a Proportional, an Integral, and a Derivative feedback element.
A "linear" servo system has an output to the active element that is truly proportional to the error. It may or may not use a PID protocol in the loop. Example might be a current/voltage control for a dc motor. Filtered PWM is usually more efficient and less expensive as a controller than truly "linear"; the latter usually involves dumping energy somewhere. But, truly "linear" is capable of faster response times. You pays your money, etc. For example, as pointed out, the heating system in your house is run by a thermostat. This element. although linear, has trip points that simply turn the fan on and off. The air in the room(s) provides the low pass filter. So an on-off device drives the servo system that maintains the air temperature in the room at a constant value. In the Rb case, we seem to have (I have fired one up, but haven't been able to observe it much) a digital servo system to maintain the Rb physics package at a fixed frequency. The servo loop seems to have a least significant change value. The point here is that by applying PWM to the least significant bit, a smaller frequency change in the output can be implemented. One still has to develop an error signal that is sufficiently accurate to implement the PWM, and it's not known yet what the characteristics of the low-pass behavior of the unit is. Hope my simple exposition is clear and right; I did not mean to initiate an argument based on semantics rather than physics :-) Don Mike S > On 1/13/2012 5:37 PM, Chris Albertson wrote: >>> What's "bang-bang servo?" (other than a techno band - >>> http://www.myspace.com/bangbangservo ) >> >> A home thermostat is the best example. It is a servo with no >> proportional control, just on and off. > > So, is a common industrial PID controller, which only provides on/off > control, but does so proportionally, "bang-bang" or not? It's > significantly different than a thermostat, which just has hysteresis > around a setpoint. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- "Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind." R. Bacon "If you don't know what it is, don't poke it." Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
