Markus Grebenstein

DLR-Hand II: next generation of a dextrous robot hand

This paper outlines the 2nd generation of multisensory hand design at DLR, based on the results of the DLR Hand I we analysed. An open skeleton structure for better maintenance with semi-shell housing and the new automatically reconfigurable palm have been equipped with more powerful actuators to reach 30 N on the fingertip. The newly designed sensors as the 6-DOF fingertip force torque sensor, the integrated electronics and the new communication architecture with a reduction of cabling to the hand to only 12 lines, are outlined. The Cartesian impedance control of all the fingers completes the new 13-DOF hand.

Variable impedance actuators: A review

Variable Impedance Actuators (VIA) have received increasing attention in recent years as many novel applications involving interactions with an unknown and dynamic environment including humans require actuators with dynamics that are not well-achieved by classical stiff actuators. This paper presents an overview of the different VIAs developed and proposes a classification based on the principles through which the variable stiffness and damping are achieved. The main classes are active impedance by control, inherent compliance and damping actuators, inertial actuators, and combinations of them, which are then further divided into subclasses. This classification allows for designers of new devices to orientate and take inspiration and users of VIAs to be guided in the design and implementation process for their targeted application.

The DLR hand arm system

An anthropomorphic hand arm system using variable stiffness actuation has been developed at DLR. It is aimed to reach its human archetype regarding size, weight and performance. The main focus of our development is put on robustness, dynamic performance and dexterity. Therefore, a paradigm change from impedance controlled, but mechanically stiff joints to robots using intrinsic variable compliance joints is carried out.

DLR MiroSurge: a versatile system for research in endoscopic telesurgery.

PurposeResearch on surgical robotics demands systems for evaluating scientific approaches. Such systems can be divided into dedicated and versatile systems. Dedicated systems are designed for a single surgical task or technique, whereas versatile systems are designed to be expandable and useful in multiple surgical applications. Versatile systems are often based on industrial robots, though, and because of this, are hardly suitable for close contact with humans.MethodTo achieve a high degree of versatility the Miro robotic surgery platform (MRSP) consists of versatile components, dedicated front–ends towards surgery and configurable interfaces for the surgeon.ResultsThis paper presents MiroSurge, a configuration of the MRSP that allows for bimanual endoscopic telesurgery with force feedback.ConclusionsWhile the components of the MiroSurge system are shown to fulfil the rigid design requirements for robotic telesurgery with force feedback, the system remains versatile, which is supposed to be a key issue for the further development and optimisation.

The DLR MIRO: a versatile lightweight robot for surgical applications

Purpose – Surgical robotics can be divided into two groups: specialized and versatile systems. Versatile systems can be used in different surgical applications, control architectures and operating room set‐ups, but often still based on the adaptation of industrial robots. Space consumption, safety and adequacy of industrial robots in the unstructured and crowded environment of an operating room and in close human robot interaction are at least questionable. The purpose of this paper is to describe the DLR MIRO, a new versatile lightweight robot for surgical applications.Design/methodology/approach – The design approach of the DLR MIRO robot focuses on compact, slim and lightweight design to assist the surgeon directly at the operating table without interference. Significantly reduced accelerated masses (total weight 10 kg) enhance the safety of the system during close interaction with patient and user. Additionally, MIRO integrates torque‐sensing capabilities to enable close interaction with human beings ...

The hand of the DLR Hand Arm System: Designed for interaction

Physical human–robot interaction implies the intersection of human and robot workspaces and intrinsically favors collision. The robustness of the most exposed parts, such as the hands, is crucial for effective and complete task execution of a robot. Considering the scales, we think that the robustness can only be achieved by the use of energy storage mechanisms, e.g. in elastic elements. The use of variable stiffness drives provides a low-pass filtering of impacts and allows stiffness adjustments depending on the task. However, using these drive principles does not guarantee the safety of the human due to the dramatically increased dynamics of such system. The design methodology of an antagonistically tendon-driven hand is explained. The resulting hand, very close to its human archetype in terms of size, weight, and, in particular, grasping performance, robustness, and dynamics, is presented. The hyper-actuated hand is a research platform that will also be used to investigate the importance of mechanical couplings and, in future projects, be the basis of a simplified hand that would still perform daily manipulation tasks.

Antagonistically driven finger design for the anthropomorphic DLR Hand Arm System

The DLR Hand Arm System is a highly dynamic and fully integrated mechatronic system which uses an anthropomorphic design. It exhibits impressive robustness by using a complete variable stiffness actuation paradigm. It aims at reaching the human archetype in most of its performances and its design. The methodology consists in understanding the human archetype on a functional basis rather than to copy it. However, the design is driven by two antipodal concepts: On one hand, the design has to be simple, robust, and easy to maintain. On the other hand it must be anthropomorphic in shape and size but also, more importantly, in functionality. The paper presents a finger design that combines a reduced diversity of parts with the need to build five kinematically different fingers. The fingers are protected against overload by allowing subluxation of the joints. The tendon routing allows for an antagonistic actuation and is optimized to minimize friction and wear. The resulting combination of the link design and the antagonistic actuation is shown to be robust against impacts as well as highly dynamic. They achieve the targeted maximum fingertip force of 30 N in stretched out configuration. The use of antagonistic drives enables to tackle problems of tendon over-stretching and slackening that commonly encounter in tendon driven mechanisms. Due to the enhanced capabilities and, in especial, its robustness, the application developers can focus on the use of innovative grasping and manipulation strategies instead of worrying about the integrity of a costly robotic systems. The possibility of storing energy in the elastic elements of the drive opens new opportunities to perform dynamics based actions (e.g. snapping fingers).

A mechatronics approach to the design of light-weight arms and multifingered hands

Describes design and development efforts in DLRs robotics lab towards a new generation of ultra-light weight robots with articulated hands. The design of fully sensorized joints with complete state feedback and the underlying mechanisms are outlined. The second light-weight arm generation is available now, as well as the second generation of a worldwide most highly integrated 4 finger-hand is available now. Thus we hope that important steps towards a new generation of service and personal robots have been achieved.

A hands-on-robot for accurate placement of pedicle screws

This paper presents a novel system for accurate placement of pedicle screws. The system consists of a new light-weight (<10 kg), kinematically redundant, and fully torque controlled robot. Additionally, the pose of the robot tool-center point is tracked by an optical navigation system, serving as an external reference source. Therefore, it is possible to measure and to compensate deviations between the intraoperative and the preoperatively planned pose. The robotic arm itself is impedance controlled. This allows for a new intuitive man-machine-interface as the joint units are equipped with torque sensors: the robot can be moved just by pulling/pushing its structure. The surgeon has full control of the robot at every step of the intervention. The hand-eye-coordination problems known from manual pedicle screw placement can be omitted

Antagonism for a Highly Anthropomorphic Hand–Arm System

A novel approach to antagonism in robotic systems is introduced and investigated as the basis for an unequalled, highly anthropomorphic hand–arm system currently being developed. This hand–arm system, consisting of a 19-d.o.f. hand and a 7-d.o.f. flexible arm, will be based on antagonistic principles in order to study and mimic the human musculoskeletal system, as well as to advance safety in robotics.