Research and Development in Robotic Systems

Light-weight Manipulator for Flexible Applications

© Fraunhofer IFF

ALEXA: An Advanced Lightweight Robot Arm for Flexible and Mobile Applications

The main focus of the ALEXA experiment was the use of portable lightweight robot arms for flexible and mobile tasks. The ALEXA robot arm is extremely lightweight and mainly consists of components from the modular robot construction kit robolink by igus®.

The manipulator's low weight is achieved through the consistent use of robolink joints, completely made of sturdy and lightweight plastics. Furthermore, the rotation axes of the robolink joints are driven by antagonistic cable pairs, and the drives are located in a separate module. This design also serves to reduce the total weight of the robot arm.


The ALEXA robot arm consists of five joints whose driving cables are connected to the central control module by separable bowden cables. The driving cables' are actuated by highly integrated drive modules, which have a very low weight relative to their power. The special base design allows the ALEXA robot arm to be installed on conventional tables or workbenches with minimal effort. This makes it easy to setup and remove. Furthermore, the use of bowden cables offers the user a large degree of freedom with regards to the position of the driving unit relative to the robot arm.

The ALEXA robot arm with its robolink plastic joints can be used for a wide range of applications.


Through the use of a multi-camera system and visual servo control technology, the positioning accuracy of the ALEXA robot arm during gripping and placing of objects can be improved. In addition, the integrated object recognition allows for an intuitive and visual teach-in.

The portability and simple situational programming of the ALEXA robot arm were key elements of the project. The ALEXA robot arm is a safe kinematic which can be used for new applications with direct human-robot interaction.

Industrial Project Partner

  • igus GmbH, Cologne

European Commission, FP7-ECHORD Project, Project runtime: 01.02.2011 – 30.09.2012