Lesson-4.markdown

@@ -51,6 +51,22 @@ So in order for this application to work properly, the car had to start of the l
 ### Exercise 4, Line Follower that stops in a goal zone
 
 ### Exercise 5, PID Line Follower
+The program for this exercise implements a standard PID controller in the following way
+
+```java
+// Calculate parameters
+			error = calculateError();
+			integral = integral + error;
+			derivative = (error - lastError) / dt;
+			
+			// Apply the PID regulation
+			controlledValue = (kp * error) + (ki * integral) + (kd * derivative);
+			
+			controlSignal(controlledValue);
+			
+			lastError = error;	
+			
+            Delay.msDelay(dt);
 
 ### Exercise 6, Color Sensor