"Tim Wescott" <tim@seemywebsite.please> wrote in message news:FImdnYzhapPSMEvPnZ2dnUVZ_qGdnZ2d@giganews.com...> On Wed, 15 Jan 2014 05:23:09 -0800, hondgm wrote: > >> I know about the auto-tuning algorithm for PID: cycle the temperature up >> and down, measure the peaks and distance between the peaks, and >> calculate Kp, Ki, and Kd. >> >> But recently I've been experimenting with what Phelan called PDF, and am >> intrigued by it. There isn't a lot of information out there about it, >> but nearly everyone that's used it has good things to say. >> >> The problem is, how is it tuned? It only has a Ki and Kd, so that makes >> it slightly simpler. An auto-tune algo like the one I just mentioned >> would be great, or at the very least, some general guide for manual >> tuning. A method that doesn't mention poles, zeros, or transforms would >> be nice because even though I have an EE degree, my strong point isn't >> controls. >> >> Either I forgot everything in my controls class or never learned it, I >> don't know which. > > It's easy enough to add real derivative control to Phelan's method. I've > read some of his original articles (or the one?). On the one hand, the > hype to value ratio is a bit high for my taste. On the other hand, the > method itself is a useful one, it's just the text surrounding it that > gets tedious. > > Phelan's layout does make implementing integrator anti-windup convenient. > > Look around and see if you can find a Z-N method for just Ki and Kp. > Better yet, try Astrom-Hagglund. Ziegler-Nichols is basically a highly > refined seat of the pants method, and tends to cough up underdamped > systems. Astrom-Hagglund is basically Ziegler-Nichols but with different > constants that result in more conservatively tuned systems. > > Astrom and Hagglund wrote a book just on PID control -- I bet they have > every flavor of Ziegler-Nichols-like tuning method in there, including > ones that exclude a derivative in the controller. > > -- > Tim Wescott > Control system and signal processing consulting > www.wescottdesign.comYep, ZN will give you a nice quarter-critical damped response if your loop is totally linear and time-invariant, but using it where there are interacting loops or other Difficulties isn't recommended. I find that the Louisiana State University approach works well on industrial loops, where some degree of nonlinearity and interaction are almost always present to some degree. It's also just as simple to apply as ZN if you put the equations into a spreadsheet. Sorry, had a quick hunt for links but they're not immediately to hand. Sure to be there somewhere.
Tuning PDF loop (pseudo derivative feedback)
Started by ●January 15, 2014
Reply by ●January 18, 20142014-01-18
Reply by ●January 19, 20142014-01-19
On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote:> I know about the auto-tuning algorithm for PID: cycle the temperature up =and down, measure the peaks and distance between the peaks, and calculate K= p, Ki, and Kd. =20>=20 >=20 >=20 > But recently I've been experimenting with what Phelan called PDF, and am =intrigued by it. There isn't a lot of information out there about it, but = nearly everyone that's used it has good things to say. =20>=20 >=20 >=20 > The problem is, how is it tuned? It only has a Ki and Kd, so that makes =it slightly simpler. An auto-tune algo like the one I just mentioned would= be great, or at the very least, some general guide for manual tuning. A m= ethod that doesn't mention poles, zeros, or transforms would be nice becaus= e even though I have an EE degree, my strong point isn't controls. =20>=20 >=20 >=20 > Either I forgot everything in my controls class or never learned it, I do=n't know which. All this tuning stuff is nonsense. You draw a Bode plot of your system and = design properly the controller. Tuning is for amateurs.
Reply by ●January 19, 20142014-01-19
On Sunday, 19 January 2014 20:10:52 UTC+11, gyans...@gmail.com wrote:> On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote: >=20 > > I know about the auto-tuning algorithm for PID: cycle the temperature u=p and down, measure the peaks and distance between the peaks, and calculate= Kp, Ki, and Kd. =20> > =20 > > But recently I've been experimenting with what Phelan called PDF, and a=m intrigued by it. There isn't a lot of information out there about it, bu= t nearly everyone that's used it has good things to say. =20> > =20 > > The problem is, how is it tuned? It only has a Ki and Kd, so that make=s it slightly simpler. An auto-tune algo like the one I just mentioned wou= ld be great, or at the very least, some general guide for manual tuning. A= method that doesn't mention poles, zeros, or transforms would be nice beca= use even though I have an EE degree, my strong point isn't controls. =20> > =20 > > Either I forgot everything in my controls class or never learned it, I =don't know which.=20>=20 > All this tuning stuff is nonsense. You draw a Bode plot of your system an=d design properly the controller. Tuning is for amateurs. Sadly, there aren't a lot of professionals around with a really good grasp = of control theory - and those few that I have met included some that could = talk the talk rather better than they could walk the walk. For the rest of us, tuning is a quick and dirty - but effective - way of ex= tracting the information that you'd need design the controller properly in = the first place. -- Bill Sloman, Sydney
Reply by ●January 19, 20142014-01-19
On Sun, 19 Jan 2014 01:10:52 -0800 (PST), gyansorova@gmail.com wrote:>On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote: >> I know about the auto-tuning algorithm for PID: cycle the temperature up and down, measure the peaks and distance between the peaks, and calculate Kp, Ki, and Kd. >> >> >> >> But recently I've been experimenting with what Phelan called PDF, and am intrigued by it. There isn't a lot of information out there about it, but nearly everyone that's used it has good things to say. >> >> >> >> The problem is, how is it tuned? It only has a Ki and Kd, so that makes it slightly simpler. An auto-tune algo like the one I just mentioned would be great, or at the very least, some general guide for manual tuning. A method that doesn't mention poles, zeros, or transforms would be nice because even though I have an EE degree, my strong point isn't controls. >> >> >> >> Either I forgot everything in my controls class or never learned it, I don't know which. > >All this tuning stuff is nonsense. You draw a Bode plot of your system and design properly the controller. Tuning is for amateurs.And you sound like an academician who's never actually BUILT anything... just paper doodles. The real world is non-linear. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 19, 20142014-01-19
On 1/19/2014 10:41 AM, Jim Thompson wrote:> On Sun, 19 Jan 2014 01:10:52 -0800 (PST), gyansorova@gmail.com wrote: > >> On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote: >>> I know about the auto-tuning algorithm for PID: cycle the temperature up and down, measure the peaks and distance between the peaks, and calculate Kp, Ki, and Kd. >>> >>> >>> >>> But recently I've been experimenting with what Phelan called PDF, and am intrigued by it. There isn't a lot of information out there about it, but nearly everyone that's used it has good things to say. >>> >>> >>> >>> The problem is, how is it tuned? It only has a Ki and Kd, so that makes it slightly simpler. An auto-tune algo like the one I just mentioned would be great, or at the very least, some general guide for manual tuning. A method that doesn't mention poles, zeros, or transforms would be nice because even though I have an EE degree, my strong point isn't controls. >>> >>> >>> >>> Either I forgot everything in my controls class or never learned it, I don't know which. >> >> All this tuning stuff is nonsense. You draw a Bode plot of your system and design properly the controller. Tuning is for amateurs. > > And you sound like an academician who's never actually BUILT > anything... just paper doodles. > > The real world is non-linear. > > ...Jim Thompson >It also benefits from those local loops we've been talking about. For instance, if you have two loop components that both have 2:1 gain variations over their working range but are faster than the rest, a single large loop has to be slowed down ridiculously to maintain stability. OTOH, if you use local loops, you can make the outer loop something like four times faster, and get much improved transient response. There are lots of things that are hard to calculate from first principles, e.g. the transient response of a multi-stage TEC. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●January 19, 20142014-01-19
On Sun, 19 Jan 2014 13:15:26 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 1/19/2014 10:41 AM, Jim Thompson wrote: >> On Sun, 19 Jan 2014 01:10:52 -0800 (PST), gyansorova@gmail.com wrote: >> >>> On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote: >>>> I know about the auto-tuning algorithm for PID: cycle the temperature up and down, measure the peaks and distance between the peaks, and calculate Kp, Ki, and Kd. >>>> >>>> >>>> >>>> But recently I've been experimenting with what Phelan called PDF, and am intrigued by it. There isn't a lot of information out there about it, but nearly everyone that's used it has good things to say. >>>> >>>> >>>> >>>> The problem is, how is it tuned? It only has a Ki and Kd, so that makes it slightly simpler. An auto-tune algo like the one I just mentioned would be great, or at the very least, some general guide for manual tuning. A method that doesn't mention poles, zeros, or transforms would be nice because even though I have an EE degree, my strong point isn't controls. >>>> >>>> >>>> >>>> Either I forgot everything in my controls class or never learned it, I don't know which. >>> >>> All this tuning stuff is nonsense. You draw a Bode plot of your system and design properly the controller. Tuning is for amateurs. >> >> And you sound like an academician who's never actually BUILT >> anything... just paper doodles. >> >> The real world is non-linear. >> >> ...Jim Thompson >> > >It also benefits from those local loops we've been talking about. For >instance, if you have two loop components that both have 2:1 gain >variations over their working range but are faster than the rest, a >single large loop has to be slowed down ridiculously to maintain >stability. OTOH, if you use local loops, you can make the outer loop >something like four times faster, and get much improved transient response. > >There are lots of things that are hard to calculate from first >principles, e.g. the transient response of a multi-stage TEC. > >Cheers > >Phil HobbsYep. In my ASIC designs, transistors are dirt cheap, so I really go hog-wild with local loops so that my building blocks approach ideal performance. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●January 19, 20142014-01-19
On Monday, January 20, 2014 4:41:29 AM UTC+13, Jim Thompson wrote:> On Sun, 19 Jan 2014 01:10:52 -0800 (PST), gyansorova@gmail.com wrote: >=20 >=20 >=20 > >On Thursday, January 16, 2014 2:23:09 AM UTC+13, hon...@yahoo.com wrote: >=20 > >> I know about the auto-tuning algorithm for PID: cycle the temperature =up and down, measure the peaks and distance between the peaks, and calculat= e Kp, Ki, and Kd. =20>=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> But recently I've been experimenting with what Phelan called PDF, and =am intrigued by it. There isn't a lot of information out there about it, b= ut nearly everyone that's used it has good things to say. =20>=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> The problem is, how is it tuned? It only has a Ki and Kd, so that mak=es it slightly simpler. An auto-tune algo like the one I just mentioned wo= uld be great, or at the very least, some general guide for manual tuning. = A method that doesn't mention poles, zeros, or transforms would be nice bec= ause even though I have an EE degree, my strong point isn't controls. =20>=20 > >>=20 >=20 > >>=20 >=20 > >>=20 >=20 > >> Either I forgot everything in my controls class or never learned it, I=don't know which.>=20 > > >=20 > >All this tuning stuff is nonsense. You draw a Bode plot of your system a=nd design properly the controller. Tuning is for amateurs.>=20 >=20 >=20 > And you sound like an academician who's never actually BUILT >=20 > anything... just paper doodles. >=20 >=20Actually wrong, it's the academics that perpetuate the PID rubbish. There r= ae many problems with this approach. The main problem is for electro-mechan= ical systems is that you have no concept of bandwidth. You are measuring ve= ry little. Time-domain design is futile. I admit if you are designing say s= ome form of chemical plant then that makes sense, since you have little kno= wledge of the plant and it is very slow anyway. Look at how a hard disk dri= ve is designed and that is how its done. Watch out for the structural reson= ance, that is the key point.
Reply by ●January 19, 20142014-01-19
On Sun, 19 Jan 2014 11:14:23 -0800 (PST), the renowned gyansorova@gmail.com wrote:> >Actually wrong, it's the academics that perpetuate the PID rubbish.I have yet to see a real controls academic that considers PID remotely interesting. Maybe at trade schools, check your matchbook covers. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●January 19, 20142014-01-19
On Monday, January 20, 2014 9:16:56 AM UTC+13, Spehro Pefhany wrote:> On Sun, 19 Jan 2014 11:14:23 -0800 (PST), the renowned >=20 > gyansorova@gmail.com wrote: >=20 >=20 >=20 > > >=20 > >Actually wrong, it's the academics that perpetuate the PID rubbish. >=20 >=20 >=20 > I have yet to see a real controls academic that considers PID remotely >=20 > interesting. Maybe at trade schools, check your matchbook covers.=20 >=20 >=20 >=20 >=20Well you're talking about the fancy research stuff, but students still need= to know the basics too and I gather they do all learn about PID and a litt= le of the lag-lead stuff which is far more of use. Trades people aren't muc= h use because they don't know what's going on most of the time, though I am= sure they could tune a PID. Academics will draw you a root-locus some of t= he time of course which is totally useless! You don't need fancy control al= gorithms for most small problems but for some (eg control of the Euro-fight= er and missile guidance) the modern stuff does get used, so don't knock it.= Amateurs are even using Kalman filters in embedded systems nowadays (for i= nertial measurement). In the 1970s these were Ph.D topics.
Reply by ●January 19, 20142014-01-19
On Sun, 19 Jan 2014 14:37:21 -0800 (PST), gyansorova@gmail.com wrote:>On Monday, January 20, 2014 9:16:56 AM UTC+13, Spehro Pefhany wrote: >> On Sun, 19 Jan 2014 11:14:23 -0800 (PST), the renowned >> >> gyansorova@gmail.com wrote: >> >> >> >> > >> >> >Actually wrong, it's the academics that perpetuate the PID rubbish. >> >> >> >> I have yet to see a real controls academic that considers PID remotely >> >> interesting. Maybe at trade schools, check your matchbook covers. >> >> >> >> > >Well you're talking about the fancy research stuff, but students still need to know the basics too and I gather they do all learn about PID and a little of the lag-lead stuff which is far more of use. Trades people aren't much use because they don't know what's going on most of the time, though I am sure they could tune a PID. Academics will draw you a root-locus some of the time of course which is totally useless! You don't need fancy control algorithms for most small problems but for some (eg control of the Euro-fighter and missile guidance) the modern stuff does get used, so don't knock it. Amateurs are even using Kalman filters in embedded systems nowadays (for inertial measurement). In the 1970s these were Ph.D topics. >Real men use a Nichol's chart >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
