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LWR III

The DLR Light Weight Robot III (LWR III) is a light-weight robot with seven degrees of freedom, which was in 2003 presented to the public for the first time.

 

 

Technical data

Size: Maximum reach 936 mm
Weight: 14 kg
Degrees of freedom: 7 (R - P - R - P - R - P - P)
Maximum Payload: 14 kg
Max. joint speed: 120°/s
Control modes: Position-, Torque-, Impedance Control
Specifics: • Completely torque controlled
• Control frequencies: Current 40 kHz; Joint 3 kHz; Cartesian 1 kHz
• Integrated electronics and internal cabling

System description

The DLR Light Weight Robot III (LWR III) represents the third generation of light-weight robots developed at the DLR Institute of Robotics and Mechatronics. Like its predecessors it has an outstanding load-to-weight ratio. The robot weighs just 14 kg and is able to handle loads up to 14 kg. Thereby it has turned the dream of a robot with a load to weight ratio of at least 1:1 into reality. The usage of Harmonic Drive gears, of Robodrive ILM motors with high power density and of light materials, as well as a consequent light-weight oriented mechanical design were key issues in reaching this goal.

Similar to the human arm, the robot has seven degrees of freedom which results in advanced flexibility in comparison to standard industrial robots. The individual joints are mechanically connected via carbon-fiber structures and communicate via a fiber optical SERCOS bus system. The innovative hand-axis design enables the configuration as pitch-pitch as well as pitch-roll unit. The electronics, including the power converters, the power cables and the communication bus system, is integrated into the robot arm. Neither a bulky external rack, known from standard systems, nor external cabling is needed.

History of the DLR LWR


Light-weight Robotics has been a central research topic at the DLR Institute of Robotics and Mechatronics for more than 20 years. To turn the dream of a robot with a payload to mass ratio of 1:1 into reality, a novel approach was taken.
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Mechatronic design of the LWR III


The mechatronic design of the LWR III forms the basis for its excellent payload-to-weight ratio and the variety of control capabilities offered by this robot arm.
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LBRControl_Joint_Control_scheme

Control of light-weight robots


Our light-weight robots are controlled by a cascaded structure of current, joint and Cartesian level controllers. The modular joints are equipped with both motor-side and link-side position sensors as well as link-side torque sensors. The collocated design of the joint with actuator and sensor in close proximity enables robust, passivity-based control approaches.
Full article

Design methods of the LWR III


The development of the LWR III required as well the close cooperation between mechanics, electronics and control design as the extensive use of Finite Elements Analysis.
Full article

LBR III – Bildergalerie

Joint of the LWR III

When the casings are removed, the compact construction of the joint modules becomes visible. 

Credit: DLR (CC BY-NC-ND 3.0).

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View of the LWR III joint

LWR III with DLR Hand II

Thanks to its tool interface, the LWR III can be equipped with various end effectors like for example the DLR Hand II. 

Credit: DLR (CC BY-NC-ND 3.0).

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LWR III with DLR Hand II

CAD Rendering of the LWR III

View of the LWR III from the right. 

Credit: DLR (CC BY-NC-ND 3.0).

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Rendering LWR III

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Publications

Robert Burger, Sami Haddadin, Georg Plank, Svel Parusel, and Gerhard Hirzinger, "The driver concept for the DLR Lightweight Robot III" in Proc. of the IEEE International Conference on Intelligent Robots and Systems (IROS), Taipeh, Taiwan, October 2010.

Gerhard Hirzinger and Alin Albu-Schäffer, "Light-Weight Robots", Scholarpedia, 3 (4), 2008, p. 3889.

Alin Albu-Schäffer, Christian Ott, U. Frese, and Gerhard Hirzinger, "Cartesian Impedance Control of Redundant Robots: Recent Results with the DLR-Light-Weight-Arms" in Proc. of the IEEE International Conference on Robotics and Automation (ICRA), Taipeh, Taiwan, September 2003.

Gerhard Hirzinger, Norbert Sporer, Alin Albu-Schäffer, M. Hähnle, R. Krenn, A. Pascucci, and M. Schedl, "DLR's torque-controlled light weight robot III - are we reaching the technological limits now?" in Proc. of the IEEE International Conference on Robotics and Automation (ICRA), Washington D.C., USA, May 2002.

LWR III
History of the DLR LWR
Mechatronic design of the LWR III
Control of light-weight robots
Design methods of the LWR III
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