Emmanuel Vander Poorten

Stability analysis and robust control for fixed-scale teleoperation

In this article we present a new theorem that reduces the stability problem of teleoperators from a structured singular value problem to a maximum singular value problem. A control scheme realizing an ideal response for fixed-scale teleoperation is proposed and its stability is proven analytically. Next, the ideal control scheme is extended to control schemes with a higher stability robustness. Also, for these more complicated schemes, stability analyses are performed making use of the new theorem and stability conditions are derived. Experiments on a 1-d.o.f. setup are conducted to confirm the validity of the proposed control schemes.

Rendering a Rigid Virtual World through an Impulsive Haptic Interface

This paper deals with the haptic rendering of collisions between a human operator and rigid objects in a virtual environment. The focus being on high-velocity impacts on a rigid wall. After discussing the importance of velocity measurements in contrast to force measurements, a new haptic device is introduced. The new device is capable of applying directly an impulse to the operator, similar to collisions occurring in the real world. Based on a Poisson-model of the rigid virtual object, the necessary change of momentum of the operators hand is being estimated online. A momentum wheel, under velocity-control, is engaged through an electromagnetic toothed clutch, at the estimated instant of impact. The resulting immediate change in momentum is thought to be essential for giving interactions with rigid virtual objects a realistic feel. Rather than generating so-called impulsive forces with big motors, this approach relies only on small motors and is thus intrinsically safer. Experiments are performed on a one-degree of freedom setup. Conclusions are drawn and future directions of this research are sketched

Design and Evaluation of a Telepresence Vision System for Manipulation Tasks

This paper describes the design of a new telepresence vision system developed to realize a higher immersive feeling for telemanipulation tasks. A new measure of permissible visual errors was defined. Making use of this new measure, a minimal vision system is designed, containing only the strictly necessary DOFs (degrees of freedom) while keeping the vision errors below an experimentally obtained set of permissible errors. The result is a 4DOF camera system, containing two rotational joints (pan-tilt) and two prismatic joints (horizontal plane.) An evaluation of the system was done through a telemanipulation task using a unified hand/arm teleoperation testbed. It was found that during use of the vision system almost all visual errors remained within the permissible errors. The proposed vision system design framework suggests to break away from simply (and often blindly) mimicking human appearance. Although we only dealt with the vision system design, the same concept could be used when designing any other part of a robot.

Estimation of optimal pivot point for remote center of motion alignment in surgery

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Impulse-based Control of an Impulsive Haptic Interface

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Feeling a rigid virtual world through an impulsive haptic display

OPP) is important for instrument manipulation in minimally invasive surgery. Such knowledge is of particular importance for robotic-assisted surgery where robots need to rotate precisely around a specific point in space in order to minimize trauma to the body wall while maintaining position control. Remote center of motion (RCM) mechanisms are commonly used, where the RCM point is manually and visually aligned. If not positioned appropriately, this misalignment might lead to intolerably high forces on the body wall with increased risk of postoperative complications or instrument damage. An automated method to align the RCM with the

Robotic ADaptation to Humans Adapting to Robots: Overview of the FP7 project RADHAR

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