On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill <lcargill99@comcast.com> wrote:>John Larkin wrote: >> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: >> >>> >>> You leave out math but include C code, I think that's defeating the >>> purpose. If you can't explain it in non-technical words or a simple >>> picture... well, try harder :-) >>> >>> You spend only one page on tuning, and give no examples of "If you see >>> this, try this" which is much more useful to the practical user. >> >> >> Engineers tend to do >> >> Actuator = error * (Kp + Ki + Kd) >> > >Uhhhhh... no. > >Actuator = (error * Kp) > + ( filter1(sum(error)) * Ki ) > + ( filter2(delta(error,lastError)) * Kd) > >> whereas old-time analog controllers did >> >> Actuator = Kp * (1 + Ki + Kd) >> >> with the idea being that it's easier to tune on-site. >> >> > >Because trimpots are awesome.Oh, you know what I mean. Old-time analog PID controllers often used a different sigal flow path than sum-of-terms. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
PID Without a PhD, Finally
Started by ●April 14, 2016
Reply by ●April 27, 20162016-04-27
Reply by ●April 29, 20162016-04-29
John Larkin wrote:> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill > <lcargill99@comcast.com> wrote: > >> John Larkin wrote: >>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: >>> >>>> >>>> You leave out math but include C code, I think that's defeating the >>>> purpose. If you can't explain it in non-technical words or a simple >>>> picture... well, try harder :-) >>>> >>>> You spend only one page on tuning, and give no examples of "If you see >>>> this, try this" which is much more useful to the practical user. >>> >>> >>> Engineers tend to do >>> >>> Actuator = error * (Kp + Ki + Kd) >>> >> >> Uhhhhh... no. >> >> Actuator = (error * Kp) >> + ( filter1(sum(error)) * Ki ) >> + ( filter2(delta(error,lastError)) * Kd) >> >>> whereas old-time analog controllers did >>> >>> Actuator = Kp * (1 + Ki + Kd) >>> >>> with the idea being that it's easier to tune on-site. >>> >>> >> >> Because trimpots are awesome. > > Oh, you know what I mean. Old-time analog PID controllers often used a > different sigal flow path than sum-of-terms. > >Oh, I'm sure. I haven't done anything directly with analog PID other than read about them. -- Les Cargill
Reply by ●April 30, 20162016-04-30
In article <nfuiil$cc0$2@dont-email.me>, lcargill99@comcast.com says...> > John Larkin wrote: > > On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill > > <lcargill99@comcast.com> wrote: > > > >> John Larkin wrote: > >>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: > >>> > >>>> > >>>> You leave out math but include C code, I think that's defeating the > >>>> purpose. If you can't explain it in non-technical words or a simple > >>>> picture... well, try harder :-) > >>>> > >>>> You spend only one page on tuning, and give no examples of "If you see > >>>> this, try this" which is much more useful to the practical user. > >>> > >>> > >>> Engineers tend to do > >>> > >>> Actuator = error * (Kp + Ki + Kd) > >>> > >> > >> Uhhhhh... no. > >> > >> Actuator = (error * Kp) > >> + ( filter1(sum(error)) * Ki ) > >> + ( filter2(delta(error,lastError)) * Kd) > >> > >>> whereas old-time analog controllers did > >>> > >>> Actuator = Kp * (1 + Ki + Kd) > >>> > >>> with the idea being that it's easier to tune on-site. > >>> > >>> > >> > >> Because trimpots are awesome. > > > > Oh, you know what I mean. Old-time analog PID controllers often used a > > different sigal flow path than sum-of-terms. > > > > > > Oh, I'm sure. I haven't done anything directly with analog > PID other than read about them.http://www.contrexinc.com/PDF/Reflex/tm_12m03_104.pdf That is a perfect Analog PID circuit,.. Scroll down to see print. LAG = (I) With enhanced control. LEAD= (D) " " " Via the BREAK levels. GAIN= (P) Dancer POS is the Set Point (SP) While the input to the buffer is the Process Value (PV) Jamie
Reply by ●May 2, 20162016-05-02
On Thu, 28 Apr 2016 22:02:08 -0500, Les Cargill <lcargill99@comcast.com> wrote:>John Larkin wrote: >> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill >> <lcargill99@comcast.com> wrote: >> >>> John Larkin wrote: >>>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: >>>> >>>>> >>>>> You leave out math but include C code, I think that's defeating the >>>>> purpose. If you can't explain it in non-technical words or a simple >>>>> picture... well, try harder :-) >>>>> >>>>> You spend only one page on tuning, and give no examples of "If you see >>>>> this, try this" which is much more useful to the practical user. >>>> >>>> >>>> Engineers tend to do >>>> >>>> Actuator = error * (Kp + Ki + Kd) >>>> >>> >>> Uhhhhh... no. >>> >>> Actuator = (error * Kp) >>> + ( filter1(sum(error)) * Ki ) >>> + ( filter2(delta(error,lastError)) * Kd) >>> >>>> whereas old-time analog controllers did >>>> >>>> Actuator = Kp * (1 + Ki + Kd) >>>> >>>> with the idea being that it's easier to tune on-site. >>>> >>>> >>> >>> Because trimpots are awesome. >> >> Oh, you know what I mean. Old-time analog PID controllers often used a >> different sigal flow path than sum-of-terms. >> >> > >Oh, I'm sure. I haven't done anything directly with analog >PID other than read about them.We do it all the time on boards: voltage regulator loops, power amps, that sort of thing. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 2, 20162016-05-02
On Mon, 02 May 2016 10:50:32 -0700, John Larkin wrote:> On Thu, 28 Apr 2016 22:02:08 -0500, Les Cargill <lcargill99@comcast.com> > wrote: > >>John Larkin wrote: >>> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill >>> <lcargill99@comcast.com> wrote: >>> >>>> John Larkin wrote: >>>>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> >>>>> wrote: >>>>> >>>>> >>>>>> You leave out math but include C code, I think that's defeating the >>>>>> purpose. If you can't explain it in non-technical words or a >>>>>> simple picture... well, try harder :-) >>>>>> >>>>>> You spend only one page on tuning, and give no examples of "If you >>>>>> see this, try this" which is much more useful to the practical >>>>>> user. >>>>> >>>>> >>>>> Engineers tend to do >>>>> >>>>> Actuator = error * (Kp + Ki + Kd) >>>>> >>>>> >>>> Uhhhhh... no. >>>> >>>> Actuator = (error * Kp) >>>> + ( filter1(sum(error)) * Ki ) >>>> + ( filter2(delta(error,lastError)) * Kd) >>>> >>>>> whereas old-time analog controllers did >>>>> >>>>> Actuator = Kp * (1 + Ki + Kd) >>>>> >>>>> with the idea being that it's easier to tune on-site. >>>>> >>>>> >>>>> >>>> Because trimpots are awesome. >>> >>> Oh, you know what I mean. Old-time analog PID controllers often used a >>> different sigal flow path than sum-of-terms. >>> >>> >>> >>Oh, I'm sure. I haven't done anything directly with analog PID other >>than read about them. > > We do it all the time on boards: voltage regulator loops, power amps, > that sort of thing.I have to admit that I do more "seat of the pants" loop tuning in that sort of circumstance than I should. Sometimes more math and less knob-twiddling is a good thing (sometimes not). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●May 2, 20162016-05-02
John Larkin wrote:> On Thu, 28 Apr 2016 22:02:08 -0500, Les Cargill > <lcargill99@comcast.com> wrote: > >> John Larkin wrote: >>> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill >>> <lcargill99@comcast.com> wrote: >>> >>>> John Larkin wrote: >>>>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: >>>>> >>>>>> >>>>>> You leave out math but include C code, I think that's defeating the >>>>>> purpose. If you can't explain it in non-technical words or a simple >>>>>> picture... well, try harder :-) >>>>>> >>>>>> You spend only one page on tuning, and give no examples of "If you see >>>>>> this, try this" which is much more useful to the practical user. >>>>> >>>>> >>>>> Engineers tend to do >>>>> >>>>> Actuator = error * (Kp + Ki + Kd) >>>>> >>>> >>>> Uhhhhh... no. >>>> >>>> Actuator = (error * Kp) >>>> + ( filter1(sum(error)) * Ki ) >>>> + ( filter2(delta(error,lastError)) * Kd) >>>> >>>>> whereas old-time analog controllers did >>>>> >>>>> Actuator = Kp * (1 + Ki + Kd) >>>>> >>>>> with the idea being that it's easier to tune on-site. >>>>> >>>>> >>>> >>>> Because trimpots are awesome. >>> >>> Oh, you know what I mean. Old-time analog PID controllers often used a >>> different sigal flow path than sum-of-terms. >>> >>> >> >> Oh, I'm sure. I haven't done anything directly with analog >> PID other than read about them. > > We do it all the time on boards: voltage regulator loops, power amps, > that sort of thing. > >Unlike PIDs, most of those should have a pretty simple method for figuring out it's at balance. I dunno, I've made some things self-calibrating in software lately. I like that better. -- Les Cargill
Reply by ●May 2, 20162016-05-02
On Mon, 2 May 2016 19:07:06 -0500, Les Cargill <lcargill99@comcast.com> wrote:>John Larkin wrote: >> On Thu, 28 Apr 2016 22:02:08 -0500, Les Cargill >> <lcargill99@comcast.com> wrote: >> >>> John Larkin wrote: >>>> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill >>>> <lcargill99@comcast.com> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> wrote: >>>>>> >>>>>>> >>>>>>> You leave out math but include C code, I think that's defeating the >>>>>>> purpose. If you can't explain it in non-technical words or a simple >>>>>>> picture... well, try harder :-) >>>>>>> >>>>>>> You spend only one page on tuning, and give no examples of "If you see >>>>>>> this, try this" which is much more useful to the practical user. >>>>>> >>>>>> >>>>>> Engineers tend to do >>>>>> >>>>>> Actuator = error * (Kp + Ki + Kd) >>>>>> >>>>> >>>>> Uhhhhh... no. >>>>> >>>>> Actuator = (error * Kp) >>>>> + ( filter1(sum(error)) * Ki ) >>>>> + ( filter2(delta(error,lastError)) * Kd) >>>>> >>>>>> whereas old-time analog controllers did >>>>>> >>>>>> Actuator = Kp * (1 + Ki + Kd) >>>>>> >>>>>> with the idea being that it's easier to tune on-site. >>>>>> >>>>>> >>>>> >>>>> Because trimpots are awesome. >>>> >>>> Oh, you know what I mean. Old-time analog PID controllers often used a >>>> different sigal flow path than sum-of-terms. >>>> >>>> >>> >>> Oh, I'm sure. I haven't done anything directly with analog >>> PID other than read about them. >> >> We do it all the time on boards: voltage regulator loops, power amps, >> that sort of thing. >> >> > >Unlike PIDs, most of those should have a pretty simple method for >figuring out it's at balance.Things like output impedance, loop stability, line and load transient regulation sometimes matter.> >I dunno, I've made some things self-calibrating in software lately. >I like that better.Sure, but it's not generally practical to make a voltage regulator using an ADC and a DAC and a lot of code. Analog PID is still useful. We sometimes do temperature controllers as analog PID loops, too. For things like crystal ovens. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 2, 20162016-05-02
On Mon, 02 May 2016 13:14:43 -0500, Tim Wescott <seemywebsite@myfooter.really> wrote:>On Mon, 02 May 2016 10:50:32 -0700, John Larkin wrote: > >> On Thu, 28 Apr 2016 22:02:08 -0500, Les Cargill <lcargill99@comcast.com> >> wrote: >> >>>John Larkin wrote: >>>> On Tue, 26 Apr 2016 21:45:06 -0500, Les Cargill >>>> <lcargill99@comcast.com> wrote: >>>> >>>>> John Larkin wrote: >>>>>> On Thu, 14 Apr 2016 19:09:26 -0400, DJ Delorie <dj@delorie.com> >>>>>> wrote: >>>>>> >>>>>> >>>>>>> You leave out math but include C code, I think that's defeating the >>>>>>> purpose. If you can't explain it in non-technical words or a >>>>>>> simple picture... well, try harder :-) >>>>>>> >>>>>>> You spend only one page on tuning, and give no examples of "If you >>>>>>> see this, try this" which is much more useful to the practical >>>>>>> user. >>>>>> >>>>>> >>>>>> Engineers tend to do >>>>>> >>>>>> Actuator = error * (Kp + Ki + Kd) >>>>>> >>>>>> >>>>> Uhhhhh... no. >>>>> >>>>> Actuator = (error * Kp) >>>>> + ( filter1(sum(error)) * Ki ) >>>>> + ( filter2(delta(error,lastError)) * Kd) >>>>> >>>>>> whereas old-time analog controllers did >>>>>> >>>>>> Actuator = Kp * (1 + Ki + Kd) >>>>>> >>>>>> with the idea being that it's easier to tune on-site. >>>>>> >>>>>> >>>>>> >>>>> Because trimpots are awesome. >>>> >>>> Oh, you know what I mean. Old-time analog PID controllers often used a >>>> different sigal flow path than sum-of-terms. >>>> >>>> >>>> >>>Oh, I'm sure. I haven't done anything directly with analog PID other >>>than read about them. >> >> We do it all the time on boards: voltage regulator loops, power amps, >> that sort of thing. > >I have to admit that I do more "seat of the pants" loop tuning in that >sort of circumstance than I should.Nothing wrong with that. We're not at a blackboard trying to impress a classroom full of EE students, we're trying to design something that works.> >Sometimes more math and less knob-twiddling is a good thing (sometimes >not).Tuning by simulation is quick. Use a little theory to get the starting point. Any serious loop is nonlinear enough that it should be simulated anyhow. Sometimes the only practical way to design a temperature control loop is by breadboarding it; the thermal structure can be too fuzzy to even simulate. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 2, 20162016-05-02
John Larkin <jjlarkin@highlandtechnology.com> writes:> Sure, but it's not generally practical to make a voltage regulator > using an ADC and a DAC and a lot of code. Analog PID is still useful.Voltage regulators typically aren't really PID though, I thought. More like P without the I or D.> We sometimes do temperature controllers as analog PID loops, too. For > things like crystal ovens.That seems like a more interesting application.
Reply by ●May 2, 20162016-05-02
John Larkin <jjlarkin@highlandtechnology.com> writes:> Sometimes the only practical way to design a temperature control loop > is by breadboarding it; the thermal structure can be too fuzzy to even > simulate.I wonder how close you can come by sticking temperature sensors all over the place during development. Then apply heat in a single place and see how the temperature map evolves over time; then move the heat source to another place and repeat, etc. The idea is to get enough info to let you simulate the system accurately using basic thermo equations.
