32 research outputs found
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
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