In the future humanoid robots are envisioned in household applications as well as in space environments. The capability to carry out complex manipulation tasks is a key issue. For its achievement the development of robust control strategies and intelligent manipulation planners for dual handed manipulation is currently a matter of active research in the robotics community.

The mobile robotic system Justin with its compliant controlled light weight arms and its two four finger hands is an ideal experimental platform for these research issues. The newly developed mobile platform allows the long range autonomous operation of the system. The individually movable, spring born wheels match the special requirements of “Justin's” upper body during manipulation tasks. PMD sensors and cameras allow the 3D reconstruction of the robot's environment and therefore enable Justin to perform given tasks autonomously.

Hands need arms... and vice versa. We have long experience with the development of light-weight robot arms, which exhibit a 1:1 force:weight ratio, are accurate yet so fast you can catch balls with them.

Our experience in developing, building and using dextrous robot hands reaches back to 1993. Our workscope covers all areas from multisensory mechatronic hand design up to control of the hands including telemanipulation, autonomous grasping and manipulation. The experiences gained with the real system result in new requirements for the next generation design steps.
 

DLR Hand II
Following our mechatronic design approach the current generation of dextrous robot hands at our lab - DLR Hand II - is a reliable, flexible and powerful multisensory and fully integrated design with a hot pluggable tool retainer and is rated as one of the most advanced and complex artificial hands in the world.

DLR-HIT-Hand - Multisensory 4-Finger-Hand
In the category 07. Industry & Construction, the DLR-HIT-Hand wins the prestigious 2007 iF design award. Quoting the reviewers, "The design clearly cites the extensor ligaments on the back of the hand, shows a line of life in the palm, and nails are indicated in the distal phalanxes. The whole hand looks very human-like and natural. This results in a high acceptance in human applications." (PDF)

A commercially available 4-Finger Hand
Based on the DLR Hand II, HIT (Harbin Institute of Technology) and DLR (German Aerospace Center) have jointly developed a multisensory robot hand. This hand, sold by Schunk as "SAH", demonstrates that highly advanced mechatronics can be embedded in applications at the medium-cost range.

The hand consists of four identical fingers, one of which is equipped with an additional drive, that functions as an opposing “thumb”. In order to correspond to the human motor functions, each finger is made up of four joints. For the Where and How, sensors at the fingers provide the force and positioning data for each joint, among others. The perfect integration of all drives including electronics in fingers and palm enables the mounting to any robot arm.

In the last decades robotics and mechatronics have found their way into many medical applications. Especially surgery has shown large potential for the use of robotic systems. The goal in medical robotics is thereby not to replace the surgeon by a robot, but to provide the surgeon with new treatment options to the benefit of the patient. Although this technology is still in its early stages, it will significantly change future surgery. The Institute of Robotics and Mechatronics contributes to this process by several research activities which reach from the development of a universal surgical robot and sensorized surgical instruments over advanced telemanipulation concepts to intraoperative autonomous functions and preoperative planning and registration.

Efficiency and flexibility of biological systems is still unreached in current robotic systems. Biological evolution formed highly specialized systems, perfectly designed with respect to material, force-to-weight ratio and energy turnover. This can be seen in the human hand, the musculoskeletal construction of which has only recently been understood in all its detail.

Although technical hands, such as the highly integrated DLR Four-Finger Hand, can already be used in a large range of applications, such hands are far from offering an alternative to the human hand, because of size and flexibility. Furthermore, a sensor with properties close to those of the human skin is far from being available to robotic hands.

To reach the same dexterity as the human hand, our solution is to construct a precise kinematic model of the human hand using in vivo MRT (magnetic resonance tomography)-data and constructing a model and robotic hand-arm system from that. The resulting robot hand will be very human-like, and can therefore be optimally connected to and controlled by the human peripheral and central nervous systems.

To ensure an optimal connection between robot and human, we investigate various interfaces:
Non-invasive: We concentrate on electromyography (EMG), placing electrodes on the skin to measure muscular activity. This approach is ideally suited for, e.g., active hand prostheses;
Invasive: We investigate a connection to the human peripheral nervous system (PNS) by inserting electrodes into nerve fibres.

In order to deliver sensory data back to its operator we develop an artificial skin-like touch sensor, based on properties of the human sensitive skin.

Biological systems are brilliant regarding their computational efficiency, complexity and adaptability. Therefore, we complete the system by carefully investigating biologically inspired cerebellum-based control strategies.

In our telepresence and virtual reality setups, a human operator immerses him/herself into a remote or virtual environment and controls a tele-operated device on motion and force level. By means of a multimodal human machine interface (HMI) the human perceives and acts as in the real world. Telerobotic systems, in contrast to telepresence systems, are implemented if the delay is too large to include the human operator into the control loop, or if the task can be performed semi-autonomously, i.e. the teleoperator acts according to its pre- or tele-programmed behaviour and the operator supervises the task execution.

Our research group places special emphasis on the haptic feedback which is used for exploring virtual or remote environments more realisticly. Haptics (from Greek haptikos “able to touch or grasp”) is related to the perception and manipulation of objects using the senses of touch and proprioception. By means of haptic feedback it is intended to imitate the touch and kinesthetic sensations that a human would feel while manipulating objects with his/her hands in the real world. Providing the user with haptic feedback is essential even for simple human activities that involve handling objects.

Technologies in order to achieve these goals are developed at the Institute.

Today in robotics, computer vision in a broad sense can be regarded as the key technology for realizing systems with an enhanced level of autonomy. In this domain, we tackle problems from a wide methodological range, from image-based tracking to scene understanding and world modeling. With such a broad scope, we can address application demands as diverse as rapid visual servoing and flexible adaptive behavior for a robot system, or generation of photo-realistic representations in a virtual-reality context.

In DLR`s programmatic structure space robotics is a so-called core topic within the program theme “technology for space systems”. This core topic is basically subdivided into the following areas and “internal projects”:

Programmatic goal:

• Space robot (flight) missions and studies (supported by the national and European space agencies)
• Supporting technologies and methodologies:
• lightweight robots
• articulated hands
• mechatronic components
• space robot dynamics
• tele-robotics / tele-presence
• autonomy and skill transfer

Space robotics will become a key technology for the exploration of the outer space and the operation and maintenance of space stations, satellites and other platforms, saving costs and relieving man from dangerous tasks.

CSA Cooperation - Ground control and dynamics modelling of ISS-robots (MSS)
Canada's contribution to the International Space Station (ISS) is the Mobile Servicing System (MSS), which is composed of the Mobile Remote Servicer Base System (MBS), the Space Station Remote Manipulator System (SSRMS) and the Special Purpose Dexterous Manipula­tor (SPDM).

Until now the planned mode of operations for SSRMS and SPDM is teleoperation by an astronaut at the robotics workstation inside the ISS. But it is predicted that this way to operate the MSS will consume a lot of crew time because of the low velocities at which the SSRMS and SPDM will be operated and because of the poten­tially large displacements to be performed by these manipulators. As an alternative to reduce the load imposed on the astronauts part of the MSS, operations on the MSS could be conducted from a ground station. SSRMS and SPDM provide control modes that would be suitable for ground operations. However, ground control is hampered by communication link limitations such as time delays and reduced bandwidth and by the lack of good situational awareness of the operator. In this context, situational awareness refers to the operator's knowledge of the spatial relationships amongst the work site equipment, features and obstacles. Situational awareness is impeded in any remote operation where the operator is limited only to equipment-mounted camera views with which to perceive the work site. To overcome these limitations a virtual reality approach is mandatory, which gives the operator the realistic feeling having the robotic system always fully under control. This requires a predictive graphical simulation of the entire robotic system on the ground control system, to compensate the relatively high data round trip time (more than 5-6 sec) as well as to provide an easy-to-use user interface for programming, controlling, and supervising the remote robot system. To ensure that MSS operations could be safely carried-out from the ground, it is necessary to demonstrate the proposed ground control technologies within a realistic environment.

Ground-Control Test-Bed
To validate the ground control concept for MSS in a representative environment, a test-bed has been developed on which the MARCO system can be integrated and tested. The objective is to faithfully reproduce the interfaces and dynamics of MSS as well as the communication limitations. One of the main components of the test-bed is the MSS Operation and Training Simulator (MOTS): a real-time dynamics simulator currently used for MSS operator training and for operation planning. It provides a high fidelity simulation of MSS operations accurately emulating the rigid and flexible body dynamics of MSS, its control software including the relevant control modes and features as well as all relevant environmental effects. To simulate MSS ground control from MARCO, CSA has added an interface to MOTS that will allow it to receive commands and transmit telemetry in the same fashion as the MSS will, through the ISS command and telemetry servers.

MARCO
The Modular Architecture for Robot Control (MARCO) developed by DLR is a spin-off of the ROTEX flight experiment conducted by DLR in 1993. Subsequent to this experiment, the ground segment has been further developed to add more and more capabilities to the system. Over the last years, DLR has focused its work in space ro­botics on the design and implementation of a high-level task-directed robot programming and control system. The goal was to develop a unified concept for a flexible, highly interactive, on-line programmable teleoperation ground station as well as an off-line programming system, which includes all the sensor-based control features partly tested in the ROTEX sce­nario. But in addition to the former ROTEX ground station it should have the capability to program a robot system at an implicit, task-directed level, including a high degree of on-board autonomy.

ROKVISS - Robotics Component Verification on ISS
Germany’s recent space robot project ROKVISS was successfully launched on December 24th 2004 form Baikonur Cosmodrome. During a spacewalk on January 26th 2005, the ROKVISS experiment hardware was mounted to the outer wall of the Russian Svesda module.

ROKVISS aims at the qualification of the newest light weight robot joint technologies as developed in DLR’s lab. They are the basis for a new generation of ultra-light, impedance controllable and soft arms, which, combined with DLR’s newest articulated 4-fingered hands, are the essential components for future robonaut systems.

DLR’s focus on space robotics was driven by strong considerations, how to push robotic technologies for space applications. A new generation of light weight robots with an unbeatable weight to load ratio as well as impressive control features, which makes the system easy-to-use and safe for terrestrial servicing applications was developed. To test and verify all these new technologies in space, recently the ROKVISS (RObot Komponent Verification on ISS) Experiment was born. The main goals of the ROKVISS experiment are the demonstration and verification of light-weight robotics components, under realistic mission conditions in free space, as well as the verification of direct tele-manipulation to show the feasibility of applying tele-presence methods for further satellite servicing tasks.

One basic idea for the ROKVISS project was to get rid of bulky and expensive radhard components for a space born application in favor of highly integrated circuits used with terrestrial devices. To come to a first assessment of the applicability of the joint mechatronics for free space, we performed a radiation, an EMC and a thermal test with one of the existing joints. The results of all these tests were very convincingly, no problem in principle could be identified.
 

SLES - Spacecraft Life Extension System
It seems that with our capture tool and docking technology as developed for ESS, we might create the first business case in on-orbit-servicing. Telecommunication satellites typically cost at least $250 million and are designed for an average on-orbit life-time of 10-15 years. Once their on-board propellant load is depleted, the satellites are boosted into a disposal orbit and decommissioned, even though their revenue-generating communications relay payloads continue to function.
Our industrial partner Orbital Recovery Corp. has initiated a so-called Spacecraft Life Extension System (SLES TM) which should significantly prolong the operating lifetimes of these valuable telecommunication satellites.

SLES will operate as an orbital tugboat, supplying the propulsion, navigation and guidance to keep a telecommunications satellite in its proper orbital slot for many additional years. Another application of the SLES could be the rescue of a spacecraft that has been placed in a wrong orbit by its launch vehicle, or which has stranded in an incorrect orbital location during positioning manoeuvres. The system is designed to easily mate with all current and future telecommunications satellites. It will link up using our proprietary docking device (the modified ESS capture tool, see Fig. below) that connects to the telecommunication satellite's apogee kick motor, as we have proposed within the ESS technology study. Meanwhile we have made a lot of effort to redesign the capture tool towards increasing its fail-safe behaviour, e.g., by using additional redundant magnetic sensors.

The Institute of Robotics and Mechatronics of the DLR has a contracted cooperation with the robot manufacturer KUKA. The main issues are to improve the dynamic performance of industrial robots by optimizing feedforward and feedback control laws. Based on non-linear dynamic robot models, feedforward control is used to maximize robot speed of the reference trajectory, and feedback control is used to improve contour following by vibration attenuation.

During the last years, DLR successfully developed algorithms, optimization environments, and simulation tools which used to improve the robots performance. See the topics below for more information.