Explaining the xacro model of seven DOF arm

We will define 10 links and 9 joints on this robot and 2 links and 2 joints in the robot gripper.

Let's start by discussing the xacro definition:

<?xml version="1.0"?>
<robot name="seven_dof_arm" xmlns:xacro="http://www.ros.org/wiki/xacro">

Because we are writing a xacro file, we should mention the xacro namespace to parse the file.

Using constants

We use constants inside this xacro to make robot descriptions shorter and readable. Here, we define the degree to the radian conversion factor, PI value, length, height, and width of each of the links:

 <property name="deg_to_rad" value="0.01745329251994329577"/> <property name="M_PI" value="3.14159"/> <property name="elbow_pitch_len" value="0.22" /> <property ...

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