diff --git a/README.md b/README.md
index 42af8d9..880aa1b 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # myCobotROS
 
 <!-- This is the mycobot ROS package designed by Zhang Lijun([lijun.zhang@elephantrobotics.com]()) -->
-> Make sure that `Atom2.lalpha` is flashed into the top Atom and `Transponder` is flashed into the base Basic .<br>
+> Make sure that `Atom2.1alpha` is flashed into the top Atom and `Transponder` is flashed into the base Basic .<br>
 > ubuntu: 16.04LTS<br>
 > ros version: 1.12.17
 
@@ -60,7 +60,7 @@ rocore #open another tab
 a) For display or marker control, in second terminal, run:
 
 ```bash
-roslaunch myCobotROS display.launch
+roslaunch myCobotROS mycobot.launch
 ```
 
 b) For slider bar control, in second terminal, run:
diff --git a/scripts/display.py b/scripts/display.py
index 0d35239..32ce33a 100755
--- a/scripts/display.py
+++ b/scripts/display.py
@@ -61,6 +61,11 @@ def talker():
         marker_.scale.z = 0.04
 
         #marker position initial 
+        # print(coords)
+        if not coords:
+            coords = [0,0,0,0,0,0]
+            rospy.loginfo('error [101]: can not get coord values')
+	
         marker_.pose.position.x =  coords[1] / 1000 * -1
         marker_.pose.position.y =  coords[0] / 1000 
         marker_.pose.position.z =  coords[2] / 1000