Diff: PID.cpp

Revision:

0:4a55d0a21ea9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PID.cpp	Tue Nov 24 19:57:06 2015 +0000
@@ -0,0 +1,103 @@
+#include <PID.h>
+#include <stdlib.h>
+#include <math.h>
+/*Constructor (...)*********************************************************
+ *    The parameters specified here are those for for which we can't set up 
+ *    reliable defaults, so we need to have the user set them.
+ ***************************************************************************/
+PID::PID(float* Input, float* Output, float* Setpoint,
+        float Kp, float Ki, float Kd)
+{
+    
+    myOutput = Output;
+    myInput = Input;
+    mySetpoint = Setpoint;
+
+    
+    PID::SetOutputLimits(-1000,1000);                //default output limit corresponds to 
+                                                //the arduino pwm limits
+    PID::SetTunings(Kp, Ki, Kd);
+    //PID::SetIntegratorLimits(399);
+       
+    
+
+}
+ 
+ 
+/* Compute() **********************************************************************
+ *     This, as they say, is where the magic happens.  this function should be called
+ *   every time "void loop()" executes.  the function will decide for itself whether a new
+ *   pid Output needs to be computed.  returns true when the output is computed,
+ *   false when nothing has been done.
+ **********************************************************************************/ 
+void PID::Compute()
+{
+
+    float input = *myInput;
+    float error =(*mySetpoint)-input; 
+    
+    ITerm+= (error+lasterror)/2;
+    /*
+     if(!ki==0){
+    
+     if(ITerm < (-abs(max/ki))){
+        ITerm= (-abs(max/ki));
+        }
+     else if(ITerm > abs(max/ki)){
+        ITerm= abs(max/ki);
+        }
+            }
+     */  
+     float dInput = (error - lasterror);
+ 
+
+           /*Compute PID Output*/
+     float output = (kp * error )+(ki * (ITerm))+(kd * (dInput));
+       if(output > outMax) output = outMax;
+      else if(output < outMin) output = outMin;
+      *myOutput =output;
+
+     /*Remember some variables for next time*/
+      lasterror=error;
+
+     
+}
+
+
+/* SetTunings(...)*************************************************************
+ * This function allows the controller's dynamic performance to be adjusted. 
+ * it's called automatically from the constructor, but tunings can also
+ * be adjusted on the fly during normal operation
+ ******************************************************************************/ 
+void PID::SetTunings(float Kp, float Ki, float Kd)
+{
+   kp = Kp;
+   ki = Ki; 
+   kd = Kd; 
+//lasterror=0;
+//ITerm=0; 
+  
+}
+  
+/* SetOutputLimits(...)****************************************************
+ *     This function will be used far more often than SetInputLimits.  while
+ *  the input to the controller will generally be in the 0-1023 range (which is
+ *  the default already,)  the output will be a little different.  maybe they'll
+ *  be doing a time window and will need 0-8000 or something.  or maybe they'll
+ *  want to clamp it from 0-125.  who knows.  at any rate, that can all be done
+ *  here.
+ **************************************************************************/
+void PID::SetOutputLimits(float Min, float Max)
+{
+    if(Min >= Max) return;
+        outMin = Min;
+        outMax = Max;
+ 
+ }
+/****************SetIntegratorLimits**********/
+void PID::SetIntegratorLimits(float Max)
+{
+max=Max;
+}
+
+