8000 Changes to PID library to allow it to be configured to not be time ba… · mikebroome/Arduino-PID-Library@c4f3f31 · GitHub
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Mike Broome
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Changes to PID library to allow it to be configured to not be time based.
- Allow SampleTime to be set to 0 to force Compute() to run every time it's called. In this case, the PID algorithm is not time based, and the user should not call it every time through loop(), but rather only based on some event (e.g. timer, button press, external input). - Add GetITerm() and GetLastInput() functions to return the current ITerm and LastInput, respectively. Being able to get and store these values allows the user of the PID library to reinitialize the PID library and continue using the same PID curve and calculation across resets. (Pass the saved ITerm as output and lastInput as input to the PID constructor to reinitialize and pick up where you left off.)
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‎PID_v1/PID_v1.cpp

Lines changed: 22 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
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/**********************************************************************************************
2-
* Arduino PID Library - Version 1.0.1
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* Arduino PID Library - Version 1.0.2
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* by Brett Beauregard <br3ttb@gmail.com> brettbeauregard.com
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* modified by Mike Broome - http://github.com/mikebroome/
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*
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* This Library is licensed under a GPLv3 License
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**********************************************************************************************/
@@ -43,6 +44,11 @@ PID::PID(double* Input, double* Output, double* Setpoint,
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* every time "void loop()" executes. the function will decide for itself whether a new
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* pid Output needs to be computed. returns true when the output is computed,
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* false when nothing has been done.
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*
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* Alternatively, if SampleTime is set to 0, Compute() will run every time it is
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* called. In this case, it would not be time based, and the user should not call
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* it every time through loop(), but rather only based on some event (e.g. timer,
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* button press, external input).
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**********************************************************************************/
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bool PID::Compute()
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{
@@ -87,6 +93,10 @@ void PID::SetTunings(double Kp, double Ki, double Kd)
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dispKp = Kp; dispKi = Ki; dispKd = Kd;
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double SampleTimeInSec = ((double)SampleTime)/1000;
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if (SampleTime == 0) {
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SampleTimeInSec = 1;
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}
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90100
kp = Kp;
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ki = Ki * SampleTimeInSec;
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kd = Kd / SampleTimeInSec;
@@ -101,13 +111,19 @@ void PID::SetTunings(double Kp, double Ki, double Kd)
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/* SetSampleTime(...) *********************************************************
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* sets the period, in Milliseconds, at which the calculation is performed
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*
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* Allow SampleTime to be set to 0 to force Compute() to run every time it's
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* called.
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******************************************************************************/
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void PID::SetSampleTime(int NewSampleTime)
106119
{
107-
if (NewSampleTime > 0)
120+
if (NewSampleTime >= 0)
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{
109-
double ratio = (double)NewSampleTime
110-
/ (double)SampleTime;
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double ratio = 1;
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if ((SampleTime != 0) && (NewSampleTime != 0)) {
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ratio = (double)NewSampleTime
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/ (double)SampleTime;
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}
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ki *= ratio;
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kd /= ratio;
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SampleTime = (unsigned long)NewSampleTime;
@@ -192,4 +208,5 @@ double PID::GetKi(){ return dispKi;}
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double PID::GetKd(){ return dispKd;}
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int PID::GetMode(){ return inAuto ? AUTOMATIC : MANUAL;}
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int PID::GetDirection(){ return controllerDirection;}
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211+
double PID::GetITerm(){ return ITerm;}
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double PID::GetLastInput(){ return lastInput;}

‎PID_v1/PID_v1.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
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#ifndef PID_v1_h
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#define PID_v1_h
3-
#define LIBRARY_VERSION 1.0.0
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#define LIBRARY_VERSION 1.0.2
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class PID
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{
@@ -50,6 +50,8 @@ class PID
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double GetKd(); // where it's important to know what is actually
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int GetMode(); // inside the PID.
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int GetDirection(); //
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double GetITerm(); //
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double GetLastInput(); //
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private:
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void Initialize();

‎PID_v1/keywords.txt

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,8 @@ GetKi KEYWORD2
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GetKd KEYWORD2
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GetMode KEYWORD2
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GetDirection KEYWORD2
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GetITerm KEYWORD2
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GetLastInput KEYWORD2
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#######################################
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# Constants (LITERAL1)

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