README.md: Add references. Add GetTi(), GetTd()

Author: David Forrest

PID_v1_bc.cpp

@@ -225,7 +225,9 @@ void PID::SetControllerDirection(int Direction)
  ******************************************************************************/
 double PID::GetKp(){ return  dispKp; }
 double PID::GetKi(){ return  dispKi;}
+double PID::GetTi(){ return  dispKp/dispKi;}
 double PID::GetKd(){ return  dispKd;}
+double PID::GetTd(){ return  dispKd/dispKp;}
 int PID::GetMode(){ return  inAuto ? AUTOMATIC : MANUAL;}
 int PID::GetDirection(){ return controllerDirection;}
 

PID_v1_bc.h

@@ -52,13 +52,14 @@ class PID
                                           //   the PID calculation is performed.  default is 100
 
 
-										  
   //Display functions ****************************************************************
 	double GetKp();						  // These functions query the pid for interal values.
 	double GetKi();						  //  they were created mainly for the pid front-end,
 	double GetKd();						  // where it's important to know what is actually 
 	int GetMode();						  //  inside the PID.
 	int GetDirection();					  //
+        double GetTi();
+        double GetTd();
 
   private:
 	void Initialize();
@@ -70,7 +71,6 @@ class PID
 	double kp;                  // * (P)roportional Tuning Parameter
     double ki;                  // * (I)ntegral Tuning Parameter
     double kd;                  // * (D)erivative Tuning Parameter
-
 	int controllerDirection;
 	int pOn;
 

README.md

@@ -18,8 +18,19 @@ The back calculation should prevent integral windup be dynamically limiting the
 from exceeding the limits.  Large errors far outside of the proportional range (error > MaxOutput/kP) will produce MaxOutput and 
 inhibit integral growth.
 
-See   
+Alternative libraries:
 
+* PID -- Brett Beauregard's well documented original uses static limits on integral windup or PonM scheme
+* QuickPID -- has several anti-windup forms
+* PID_RT -- Has anti-windup but Proportional-on-measurement
+
+
+See:
+*  https://en.wikipedia.org/wiki/PID_controller#Integral_windup -- overview of Integral Windup & common solutions
+*  https://en.wikipedia.org/wiki/Integral_windup -- overview of Integral Windup & common solutions
+* https://www.cds.caltech.edu/~murray/courses/cds101/fa02/caltech/astrom-ch6.pdf -- Textbook chaper with windup and backcalculation
+* https://controlguru.com/integral-reset-windup-jacketing-logic-and-the-velocity-pi-form/ -- good pics
+*  https://homepages.laas.fr/lzaccari/preprints/ZackEJC09.pdf -- A comprehensive paper on more complicated anti-windup schemes than backcalculation
 *  https://github.com/br3ttb/Arduino-PID-Library/pull/116 -- Pull request to the PID_v1 library
-*  https://github.com/br3ttb/Arduino-PID-Library/issues/76#issuecomment-1445273655
+*  https://github.com/br3ttb/Arduino-PID-Library/issues/76