Update README.md

README.md

@@ -10,9 +10,9 @@
 
 # COMPONENTS
 * On docking station
- * One IR emitter 
+ * Three IR emitters 
 * On ANDBOT
- * Two IR receivers 
+ * Four IR receivers 
  * microSW
 
 # BASIC OPERATIONS
@@ -22,10 +22,13 @@
 ## State diagram
 ![](https://docs.google.com/drawings/d/1y88r8ekS2AH1VXI44CYqL3lbkHgwUZl5kNnLzkqsd8c/pub?w=960&h=720)
 
-* We will use ROS navigation to command the ANDBOT to move to the landing point, which should be in 0.7 meter in front of the docking station. The ANDBOT's back will be facing to the docking station.
+* We will use ROS navigation to command the ANDBOT to move to the landing point, which should be in 0.7 meter in front of the docking station. The ANDBOT's back is supposed to be faced to the docking station.
  * ROS navigation can cause around 0.2m position errors and 0.3rad orientation errors. 
-* Then, ANDBOT should rotate in-place until the IR receiver got signals which is greater than the pre-defined threshold.
-* Then, ANDBOT will start to do orientation PID control to move toward the docking station and keep the two IR receiver readings balanced.
+* Then, ANDBOT should rotate in-place until any of following conditions:
+ * The R0 or R1 got signals which is greater than the pre-defined threshold. It means the robot is in the zone Z1.
+ * The R2 got signals from E2, then the ANDBOT should move ahead until it lost the E2 signal
+ * The R3 got signals from E3, then the ANDBOT should move ahead until it lost the E3 signal 
+* Then, ANDBOT will start to do orientation PID control to move toward the docking station and keep the R0 & R1 readings balanced.
 * Until the microSW on.