History of the DLR LWR

To turn the dream of a robot with a payload to mass ratio of 1:1 into reality, a novel approach was taken: Instead of ensuring the necessary positioning accuracy for assembly and service tasks by a very rigid and therefore voluminous and heavy structure, the light-weight robot can feel the correct positions at the workpiece like a human worker. In the case of a classical ‚peg in hole‘ problem for example, the assembly position is approximated on a millimetric scale until contact is reached. Afterwards the exact assembly position is identified by a search movement using the integrated sensors.
 
The necessary internal link side position and joint torque sensors offer several additional advantages:

• Vibrations of the robot arm can be directly measured and actively damped, which allows for high dynamic movements
• Collisions with the environment are detected immediately, which allows in connection with the low mass of the light-weight robot a safe human robot interaction.

The low mass due to the - compared to conventional industrial robots - lighter structure permits it to reach identical dynamic properties with smaller motors. This enhances the weight reduction even further and thereby simplifies the transport of the robot to varying sites of operation.

The first light-weight robot at the Institute of Robotics and Mechatronics was the DLR Light-Weight Robot (LWR) I, completed in 1995. Both the LWR I and its successor LWR II (presented in 2000) were mere research systems. The experiences from these two generations of light-weight robots were taken into account for the development of the LWR III (presented in 2003).

In 2004 the DLR LWR III was licensed to KUKA Roboter GmbH. KUKA refined the technology over the KUKA LBR 4 (2008) and the KUKA LBR 4+ (2010) to the KUKA LBR iiwa (2013).

The DLR LWR III as well as its successors, the KUKA LBR 4, the KUKA LBR 4+ and the KUKA LBR iiwa have demonstrated large potentials for both industry and research.

From March 2009 the KUKA LBR 4 has been used in the fully automated assembly of rear axle gearboxes at the Mercedes-Benz Untertürkheim plant. When in December 2012 Daimler-Benz and KUKA signed a strategic cooperation about investigating the cooperation of human workers and KUKA LBRs in assembly tasks, more than 500,000 rear axle gearboxes have been assembled by these lightweight robots.

The DLR used the KUKA LBR iiwa in the context of the SMErobotics project to investigate the easy automation of assembly tasks.

Due to its lightweight design and the torque sensors in each joint, the DLR LWR III allows a close interaction of human and robot. To develop solutions for safe, intuitive, and dynamic human-robot interaction, DLR conducts research in this fields.