update docs

ArmNavigation/two_joint_arm_to_point_control/Planar_Two_Link_IK.ipynb

@@ -4,7 +4,22 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Inverse Kinematics for a Planar Two-Link Robotic Arm\n",
+    "## Two joint arm to point control\n",
+    "\n",
+    "![TwoJointArmToPointControl](https://github.com/AtsushiSakai/PythonRobotics/raw/master/ArmNavigation/two_joint_arm_to_point_control/animation.gif)\n",
+    "\n",
+    "\n",
+    "\n",
+    "\n",
+    "This is two joint arm to a point control simulation.\n",
+    "\n",
+    "This is a interactive simulation.\n",
+    "\n",
+    "You can set the goal position of the end effector with left-click on the ploting area.\n",
+    "\n",
+    "\n",
+    "\n",
+    "### Inverse Kinematics for a Planar Two-Link Robotic Arm\n",
     "\n",
     "A classic problem with robotic arms is getting the end-effector, the mechanism at the end of the arm responsible for manipulating the environment, to where you need it to be. Maybe the end-effector is a gripper and maybe you want to pick up an object and maybe you know where that object is relative to the robot - but you cannot tell the end-effector where to go directly. Instead, you have to determine the joint angles that get the end-effector to where you want it to be. This problem is known as inverse kinematics.\n",
     "\n",
@@ -403,7 +418,7 @@
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    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.5.2"
+   "version": "3.6.6"
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