4 ms·

A robotic analogue is tuning PID loops. There exists loads of literature on the subject, but it turns out that it's quite hard, despite the relatively simplicit

A robotic analogue is tuning PID loops. There exists loads of literature on the subject, but it turns out that it's quite hard, despite the relatively simplicity of the control law [1]. It's the underlying dynamics that results in no golden rule of PID tuning if you start the system from a random state. The whole computer stack is similarly complex, but higher dimension and it's not clear what metric you would tune against (it would be application specific). Not that I think it's impossible, lots of regions of computer science are self-adaptive (TCP, splay tree). Its just the ensemble is a mega chaotic space. Maybe someone will hook up a DBN and skynet it soon. [1] http://en.wikipedia.org/wiki/PID_controller#Loop_tuning http://en.wikipedia.org/wiki/PID_controller#Loop_tuning

ArkyBeagle 11y ago
This is a bit of a slog to read, but it's not bad: http://www.amazon.com/Adaptive-Control-Edition-Johan-Astrom/dp/0201558661 http://www.amazon.com/Adaptive-Control-Edition-Johan-Astrom/...
analog31 11y ago
While tuning PID loops in general is a hard problem, auto-tuning PID temperature controllers have been around for a long time. For instance: https://www.ia.omron.com/products/family/165/specification.html https://www.ia.omron.com/products/family/165/specification.h... I've used similar controllers (a bewildering variety of models for different kinds of sensors and electrical loads), and they are uncanny.
- snowwindwaves 11y ago
  what systems other than temperature control have you used an auto-tune with? I attempted to use a PID auto-tune on a hydro electric turbine once and watched (with horror) as it stroked the wicket gates open and closed with 10s period for about 30s before the wicket gate linkage actually broke. The linkage breaking was due to improperly set 0-point but it became clear that auto-tune isn't appropriate for all systems, and holy hell I'd be damn sure I knew what an auto-tune was going to do before I unleashed it on actual equipment again. Probably I would want to specify the min and max for the CV ... more knobs that need to be set. In my avergage hydro-electric plant there are 320 constants or "knobs" for the system plus 170 for each unit, so 1000 parameters that need to be determined during programming or commissioning for a 4-unit plant.
  - analog31 11y ago
    Very good point. Outside of temperature control, I have not seen these used. At my workplace, we have a motor and controller that are presently unusable because the supplier can't come up with workable PID settings. Fortunately it's a demo unit for a prototype, so nobody's out any money.
dharma1 11y ago
Ardupilot has had autotune for PID's for a while - and it works really well! http://copter.ardupilot.com/wiki/autotune/ http://copter.ardupilot.com/wiki/autotune/

ArkyBeagle 11y ago

This is a bit of a slog to read, but it's not bad: http://www.amazon.com/Adaptive-Control-Edition-Johan-Astrom/dp/0201558661 http://www.amazon.com/Adaptive-Control-Edition-Johan-Astrom/...

analog31 11y ago

While tuning PID loops in general is a hard problem, auto-tuning PID temperature controllers have been around for a long time. For instance: https://www.ia.omron.com/products/family/165/specification.html https://www.ia.omron.com/products/family/165/specification.h... I've used similar controllers (a bewildering variety of models for different kinds of sensors and electrical loads), and they are uncanny.

snowwindwaves 11y ago
what systems other than temperature control have you used an auto-tune with? I attempted to use a PID auto-tune on a hydro electric turbine once and watched (with horror) as it stroked the wicket gates open and closed with 10s period for about 30s before the wicket gate linkage actually broke. The linkage breaking was due to improperly set 0-point but it became clear that auto-tune isn't appropriate for all systems, and holy hell I'd be damn sure I knew what an auto-tune was going to do before I unleashed it on actual equipment again. Probably I would want to specify the min and max for the CV ... more knobs that need to be set. In my avergage hydro-electric plant there are 320 constants or "knobs" for the system plus 170 for each unit, so 1000 parameters that need to be determined during programming or commissioning for a 4-unit plant.
- analog31 11y ago
  Very good point. Outside of temperature control, I have not seen these used. At my workplace, we have a motor and controller that are presently unusable because the supplier can't come up with workable PID settings. Fortunately it's a demo unit for a prototype, so nobody's out any money.

dharma1 11y ago

Ardupilot has had autotune for PID's for a while - and it works really well! http://copter.ardupilot.com/wiki/autotune/ http://copter.ardupilot.com/wiki/autotune/