Add README.md

README.md

+# Description
+
+This ROS package contains physical descriptions of a Dynamixel pan&tilt device.
+
+The following files are provided by this package:
+
+ * Xacro macro to be included in higher level urdf or xacro files.
+
+ * An example xacro file to be used as an example of use of the macro.
+
+# Dependencies
+
+This node has the following dependencies:
+
+  * [iri_dynamixel_pan_tilt_gazebo](https://gitlab.iri.upc.edu/labrobotica/ros/sensors/imu/iri_dynamixel_pan_tilt_gazebo) (for simulation only)
+
+# Installation
+
+- Move to workspace: `roscd && cd ../src`
+- Clone the repository: `git clone https://gitlab.iri.upc.edu/labrobotica/ros/devices/ptu_d46/iri_dynamixel_pan_tilt_description.git`
+- Compile:  `roscd && cd .. && catkin_make -DCMAKE_BUILD_TYPE=Release`
+
+# How to use it
+
+The [ax12_pan_tilt_example.xacro](https://gitlab.iri.upc.edu/labrobotica/ros/devices/dynamixel_pan_tilt/iri_dynamixel_pan_tilt_description/blob/master/urdf/ax12_pan_tilt_example.xacro) 
+file shows an example of how to include the xacro macro in another xacro file.
+
+The xacro macro has the following parameters:
+
+ * **prefix:** name of the device used to specify the frames and joints to allow multiples instances.
+
+ * **parent:** name of the parent frame of the IMU sensor. 
+
+ * **pan_joint_name:** name of the pan joint.
+ 
+ * **tilt_joint_name:** name of the tilt joint.
+ 
+ * **load_name:** name of the load frame.
+
+ * **origin:** pose of the device with respect of the parent frame.