To build a robot arm, we need the following:

• A good set of linkages that move independently with good physical strength
• A good set of actuators that could help us withstand enough payload
• Drive controls

In case you plan to build a real robot arm, you might need similar embedded architecture and electronic controls, real-time communication between the actuators, a power management system, and maybe a good end effector, based on your application requirements. As you know, there's more to consider and this is not in the scope of this book. However, the aim is to emulate a robot arm in ROS so that it works the same way in reality as well. Now, let's look at the robot arm specifications.