Diff: PI_Cntrl.cpp

Revision:

6:8ed679044a72

Parent:

2:769ce5f06d3e

Child:

11:67af6d24c588

--- a/PI_Cntrl.cpp	Tue Apr 17 09:06:47 2018 +0000
+++ b/PI_Cntrl.cpp	Tue Apr 17 11:47:35 2018 +0000
@@ -1,31 +1,61 @@
-/*#include "PI_Cntrl.h"
+/*  
+    PI Controller class with anti windup reset in biquad transposed direct form 2
+    see e.g.: https://www.dsprelated.com/freebooks/filters/Four_Direct_Forms.html
+    everything is calculated in double
+    
+                  Tn*s + 1                      
+      G(s) = Kp -------------  with s ~ (1 - z^-1)/Ts
+                    Ts*s                     
+*/
+
+#include "PI_Cntrl.h"
 
 using namespace std;
 
-PI_Cntrl::PI_Cntrl(float Kp, float Tn){
-    this->Kp = Kp;
-    this->Tn = Tn_;
-    
-    //...
-    
-    
-    }
+PI_Cntrl::PI_Cntrl(float Kp, float Tn, float Ts)
+{
+    setCoefficients(Kp, Tn, Ts);
+    uMax = 10000000000.0;
+    uMin = -uMax;
+    reset(0.0f);
+}
 
+PI_Cntrl::PI_Cntrl(float Kp, float Tn, float Ts, float uMax)
+{
+    setCoefficients(Kp, Tn, Ts);
+    this->uMax = (double)uMax;
+    uMin = -(double)uMax;
+    reset(0.0f);
+}
 
-PI_Cntrl::~PI_Cntrl() {} 
-    
-void PI_Cntrl::reset(float initValue) {
-//...
-
+PI_Cntrl::PI_Cntrl(float Kp, float Tn, float Ts, float uMax, float uMin)
+{
+    setCoefficients(Kp, Tn, Ts);
+    this->uMax = (double)uMax;
+    this->uMin = (double)uMin;
+    reset(0.0f);
 }
 
-float PI_Cntrl::doStep(float error){
-    
-    // ...
-    
-    // -------- Anti-Windup -------- 
-    // ...
-    // -------- Timeshift --------
-    
-    
-    }*/
\ No newline at end of file
+PI_Cntrl::~PI_Cntrl() {}
+
+void PI_Cntrl::reset(float initValue)
+{
+    s = (double)initValue;
+}
+
+void PI_Cntrl::setCoefficients(float Kp, float Tn, float Ts)
+{
+    b0 = (double)Kp*(1.0 + (double)Ts/(double)Tn);
+    b1 = -(double)Kp;
+    b2 = (double)Ts/(double)Tn;    
+}
+
+float PI_Cntrl::doStep(double e)
+{
+    double u = b0*e + s;          // unconstrained output
+    double uc = u;                // constrained output
+    if(u > uMax) uc = uMax;
+    else if(u < uMin) uc = uMin;
+    s = b1*e + u - b2*(u - uc);
+    return (float)uc;
+}
\ No newline at end of file