add example for pidController

examples/simple_pid_controller/simple_pid_controller.ino

@@ -0,0 +1,34 @@
+#include <qlibs.h>
+
+continuousTF<1> processTransferFunction= {
+    { 0.0f, 1.5f, },
+    { 2.0f, 1.0f, },
+};
+
+constexpr real_t dt = 0.05f;    /*Time step*/
+real_t yt = 0.0f;               /*Process output*/
+real_t ut = 0.0f;               /*Controller output*/
+real_t wt = 0.0f;               /*Set-Point*/
+continuousSystem process( processTransferFunction, dt );
+pidController controller;
+int inputPin = A0;   // select the input pin for the potentiometer that will drive the setPoint
+
+void setup() {
+  Serial.begin(9600);
+  controller.setup( 5.0f, 10.0f ,0.01f ,dt );
+  controller.setSaturation( 0.0f, 100.0f );
+}
+
+void loop() {
+  /*Set-Point is driven from a potentiometer connected to analog input*/
+  wt = map( analogRead( inputPin ), 0, 1023, 0.0f, 100.0f );
+  ut = controller.control( wt, yt );
+  yt = process.excite( ut );
+
+  Serial.print( ut );
+  Serial.print( "," );
+  Serial.print( wt );
+  Serial.print( "," );
+  Serial.println( yt );
+  delay( dt*1000 );
+}