Abstract: Modular robotic arms include modular sections with a joint and arm segment. In some examples, the modular sections may connect to each other using common tooling flanges, such as a standard robotic interface for an end effector. In the same or different examples, a robotic arm controller is located in a base or other section for the robotic arm. In the same or different examples, a robotic arm joint includes a differential gear with two motors. Coordinated control of the two differential joint motors facilitates both hinge and rotary motion for the joint.