diff --git a/docs/modules/arm_navigation.rst b/docs/modules/arm_navigation.rst
index a13604f1..8d641431 100644
--- a/docs/modules/arm_navigation.rst
+++ b/docs/modules/arm_navigation.rst
@@ -15,7 +15,7 @@ ploting area.
 
 Check this doc for machematical background: `Jupyter notebook documentation <https://github.com/AtsushiSakai/PythonRobotics/blob/master/ArmNavigation/two_joint_arm_to_point_control/Planar_Two_Link_IK.ipynb>`_
 
-|3|
+|arm_to_point|
 
 N joint arm to point control
 ----------------------------
@@ -27,9 +27,17 @@ This is a interactive simulation.
 You can set the goal position of the end effector with left-click on the
 ploting area.
 
-|4|
+|n_joints_arm|
 
 In this simulation N = 10, however, you can change it.
 
-.. |3| image:: https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/two_joint_arm_to_point_control/animation.gif
-.. |4| image:: https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/n_joint_arm_to_point_control/animation.gif
+Arm navigation with obstacle avoidance
+--------------------------------------
+
+Arm navigation with obstacle avoidance simulation.
+
+|obstacle|
+
+.. |arm_to_point| image:: https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/two_joint_arm_to_point_control/animation.gif
+.. |n_joints_arm| image:: https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/n_joint_arm_to_point_control/animation.gif
+.. |obstacle| image:: https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/arm_obstacle_navigation/animation.gif