Feature request: log PID values and option to manually restore/set accumulated Kp value


#1

Seeing some really exciting progress on cbox and brewblox! Just wanted to throw in a feature request that I think would remove a frequent pain point of mine.

Current status quo (two pain points, one inefficient positive feature):

Scenario: Wifi resets during active fermentation
   Given: controlled beer is actively fermenting
     And: temperature is stabilized by accumulated integral
     And: spark loses connectivity to pi (thus stopping logging)
    When: user resets power to spark to resume logging
    Then: logging resumes
     And: accumulated integral is reset to zero
     And: controller loses control of fermentation until integral re-accumulates 

Scenario: brief (perhaps intentional) power loss during active fermentation
   Given: controlled beer is actively fermenting
     And: temperature is stabilized by accumulated integral
    When: power to spark is (perhaps intentionally) cycled
    Then: accumulated integral is reset to zero
     And: controller loses control of fermentation until integral re-accumulates

Scenario: too much integral
   Given: controlled beer reaching end on active fermentation
     And: accumulated integral from more active fermentation persists and fridge set point lower than neccesary
    When: power to spark is intentionally cycled
    Then: accumulated integral is reset to zero
     And: controller re-accumulates more more appropriate component integral

My suggestion is to

  1. log PID values to the pi’s datastore (this will also make PID tuning easier)
  2. give an options:
    a) after a power cycle, restore accumulated integral to the last logged value (or have integral persist on controller through a power cycle) and/or
    b) at any time, user can manually change the integral to an arbitrary value.

With suggested feature:

Scenario: Wifi resets during active fermentation
   Given: controlled beer is actively fermenting
     And: temperature is stabilized by accumulated integral
     And: spark loses connectivity to pi (thus stopping logging)
    When: user resets power to spark to resume logging
    Then: logging resumes
     And: accumulated integral is reset to previously logged value
     And: controller remains in control of fermentation 

Scenario: brief (perhaps intentional) power loss active fermentation
   Given: controlled beer is actively fermenting
     And: temperature is stabilized by accumulated integral
    When: power to spark is (perhaps intentionally) cycled
    Then: accumulated integral is reset to previously logged value
     And: controller remains in control of fermentation

Scenario: too much integral
   Given: controlled beer reaching end on active fermentation
     And: accumulated integral from more active fermentation persists and fridge set point lower than neccesary
    When: user wants to manually reset accumultor
    Then: they have option to do so manually via the UI
     And: controller set to more appropriate integral component 
     And: fridge set point is more appropriate for level of yeast activity

Scenario: PID tuning
   Given: User needs to tune the PID for their equipment
     And: User lacks intuition to decompose factors affecting setpoint curve into P I and D components
    When: User is trying to diagnose problems
    Then: they can look directly at logged PID values
     And: explicitly see factors driving unwanted behavior
     And: adjust accordingly

#2

I would love this feature. I hate not having the ability to reset the integrator. I would even like to take it a step further. On CraftBeerPi (never used it…but I think this is true), the user gets to implement their own control algorithms without having to recompile anything or get deep into the source. I would love to implement my own type of feed-forward control in conjunction with the PID. For example, use Newton’s Law of Cooling to automatically adjust the fridge temperature on ramps instead of waiting for the integrator to wind up appropriately.