The driver concept for the DLR Lightweight Robot III

In this paper we present the synchronization and driver architecture of the DLR LWR-III, which supplies an easy to use interface for applications. For our purpose we abstracted the robot hardware entirely from the control algorithms using the common device driver concept of modern operating systems. The software architecture is split into two modular parts. On the one side, there are device drivers that communicate with the hardware components. On the other side, there are realtime ap- plications realized as Simulink Models, which provide advanced control algorithms. This ensures a clean separation between the two modules and provides a communication over a common and approved interface. Furthermore we investigated how we can ensure synchronization to the hardware over the device driver interfaces and how we can ensure that it meets hard realtime requirements. The main result of this paper is to realize a synchronization between LWR-III hardware and Simulink control applications while targeting small latencies with respect to hard realtime requirements. The design is implemented and verified on WindRiverTM VxWorksTM

An Introduction to Robotically Assisted Surgical Systems: Current Developments and Focus Areas of Research

Robotic assistance systems for diagnosis and therapy have become technically mature and widely available. Thus, they play an increasingly important role in patient care. This paper provides an overview of the general concepts of robotically assisted surgical systems, briefly revisiting historical and current developments in the surgical robotics market and discussing current focus areas of research. Comprehensiveness cannot be achieved in this format, but besides the general overview, references to further readings and more comprehensive reviews with regard to particular aspects are given. Therefore, the work at hand is considered as an introductory paper into the topic and especially addresses investigators, researchers, medical device manufacturers, and clinicians, who are new to this field

Passivity-based Object-Level Impedance Control for a Multfingered Hand.

Holding an object and manipulating it in 6D is a key application for multifingered robot hands. In the past many algorithms were proposed based on a weighted pseudoinverse of the grasp map combined with an internal force control. The majority of these algorithms require robust contact detection/tracking and switching controllers. Employing the virtual object introduced by Stramigioli we present an object-level control law. We define a novel virtual object frame based on the robot hand configuration. Our control law takes a desired object frame and desired grasping forces as input, it is passive, has an intuitive physical meaning, and stability is even given in case a finger looses contact with the object. A damping design as a function of the desired object stiffness and the combined hand-object inertia is presented. The performance of the controller is proven in two experiments implemented on the DLR Hand II

Stability Boundary for Haptic Rendering: Influence of Physical Damping.

Physical damping is increasing the z-width of haptic simulations. This paper derives the normalized stability boundaries for physically damped one degree of freedom haptic devices colliding with a virtual wall represented as spring-damper system. These boundaries are independent of the haptic device’s mass and the sampling time. Furthermore, the dependency of the maximum stable virtual stiffness is discussed. Moreover, this paper illustrates that the passive region which is defined by Colgate’s passivity condition is a subset inside the stable region for undelayed systems, but not for delayed systems

Reactionless Control for Two Manipulators Mounted on a Cable-Suspended Platform

The dynamics and control of a cable-suspended, two-arm robotic system are developed for an entertainment application. One manipulator arm is controlled to fulfil a user defined task. The second arm is then controlled to compensate for the disturbances on the cable-suspended platform arising from the motion of the first. Model-based feed forward control, stemming from the momentum conservation equations of a free-floating robot, is developed for the motion compensation problem. Furthermore, due to model uncertainty, sensor-based feedback control is introduced, to account for undesired oscillatory motions of the system. The latter control problem reduces to the dissipation of the oscillatory energy of the system, by means of adequate robot control. Both control methods are implemented and tested on an experimental set-up

Agile Robot Development (aRD): A Pragmatic Approach to Robotic Software

Mechatronic systems are reaching a new level of complexity, both for the single component and for overall systems making necessary a new software concept for the development and usage of such systems. Here we introduce the agile Robot Development (aRD) concept, which is a flexible, pragmatic and distributed software design to support and simplify the development of complex mechatronic and robotic systems. It gives easy access to scalable computing performance (even in hard real-time) and is motivated by the abstract view on a robotic system as being a decentral net of calculation blocks and communication links. We discuss design considerations and an implementation of this concept and demonstrate its performance with first applications

Robotics Component Verification on ISS ROKVISS - Preliminary Results for Telepresence.

ROKVISS, Germany’s newest space robotics technology experiment, was successfully installed outside at the Russian Service Module of the International Space Station (ISS) during an extravehicular space walk at the end of January 2005. Since February 2005 a two joint manipulator is operated from ground via a direct radio link. The aim of ROKVISS is the in flight verification of highly integrated modular robotic joints as well as the demonstration of different control modes, reaching from high system autonomy to force feedback teleoperation (telepresence mode). The experiment will be operated for at least one year in free space to evaluate and qualify intelligent light weight robotics components under realistic circumstances for maintenance and repair tasks as foreseen in upcoming manned and unmanned space applications in near future. This paper focuses in the telepresence control mode, its technology and first results from the space experiment ROKVISS

Time Domain Passivity Control Based Telepresence with Time Delay.

This paper analyses the Time Domain Passivity Control approach in the time-delayed telepresence context, and proposes a method which provides stable operation. The passivity controller for the two-port network which is created by the bilateral control and communication elements in [1] is shown to be not valid if a time delay is introduced in the communication channel. Classical stability analysis for the delayed system is presented and used as argument and benchmark for the proposed solution. Simulations and experimental results are discussed and compared with classical stability analysis

A workspace analysis method to support intraoperative trocar placement in minimally invasive robotic surgery (MIRS)

This paper presents a new method to calculate and display an approximated workspace of a surgical robot in nearly realtime. Displaying this information on a screen in the operation room could support the surgeon during intraoperative trocar placement for teleoperated minimally invasive robotic surgery (MIRS). We give a short overview on existing trocar placement procedures in teleoperated MIRS and describe the possibilities and limitations of workspace analysis methods to support the surgeon during trocar placement. Our new method uses MIRS-specific simplifications to reduce the search space and enable the creation of a reduced workspace map. It was implemented for the DLR MiroSurge system. The implementation can create a reduced workspace map and display a mesh representation of the map in less than 2 seconds. We give a short outlook on how this method could be embedded in trocar placement procedures in the operation theater and what our future plans are with this method