Emmanuel Vander Poorten | KU Leuven (original) (raw)

Papers by Emmanuel Vander Poorten

Apparatus (10) for generating motion around a remote center of motion (RCM), comprising a distal ... more Apparatus (10) for generating motion around a remote center of motion (RCM), comprising a distal link (L12, LR) arranged to revolve about the remote center of motion and to translate through the remote center of motion, a proximal link (L10, LI)
arranged to revolve about a proximal center of motion (LCM), coupled to a base link, through a rotational joint (150) and a sliding joint (181), a first mechanism comprising a first link (L9, BE) pivotally coupled to the proximal link (L10) and to the distal link (L12) and operable to transfer motion of the proximal link relative to the proximal center of motion to a motion of the distal link relative to the remote center of motion by maintaining a parallelogram (PARl), and a second mechanism operable to move the first link with two degrees of freedom in a plane parallel to the plane of motion of the proximal link, characterised in that the second mechanism comprises one link or a serial connection of links (L4, L8, L3, L7, L2, L6) connecting the base link to the first link, configured to have an orientation of instant motion which is different from an orientation of instant motion of the proximal link (LlO), relative to the base link.

Journal of the Robotics …, 2009

Book of Abstracts-28th Benelux Meeting on …, 2009

Controller synthesis for teleoperation boils down to making an adequate trade-off between perform... more Controller synthesis for teleoperation boils down to making an adequate trade-off between performance and stability. By incorporating more knowledge of the system or its interacting elements, performance can be gained without compromising stability. Compared to 2-and 3-channel schemes, 4-channel controllers, using force and displacement signals measured at both master and slave, are inherently more powerful. However, the substantial amount of parameters involved in these systems, complicates their understanding, restraining their practical use. This document advocates the use of H ∞ theory to take care of parameter tuning and introduces methods to incorporate stability requirements and environmental knowledge into the H ∞ framework.

SCATh Joint …, 2011

Retinal Vein Occlusion (RVO) is a common retinal vascular disorder which may cause severe loss of... more Retinal Vein Occlusion (RVO) is a common retinal vascular disorder which may cause severe loss of vision. To assist the surgeon in treating this condition, we developed a robotic system for retinal surgery. The system enhances the surgeons precision by using comanipulation control schemes. We developed a new testing device to simulate the conditions encountered during retinal procedures. Initial tests conducted with this device proof the enhanced precision when using the robotic system.

This paper analyses and compares two passivity-based approaches that allow to include a-priori kn... more This paper analyses and compares two passivity-based approaches that allow to include a-priori knowledge on the dynamic range of the human operator and/or the environment. This can lead to less conservative teleoperation systems compared to systems designed to be purely passive or absolutely stable. The first approach under investigation is a method where the absolute stability is analysed of a teleoperation system augmented with shunt impedances in series and/or parallel with the teleoperation system. It is shown that the traditional interpretation of the use of shunt impedances is not valid and a more accurate description of how to use this method is presented. The second approach under investigation is the bounded environment (operator) method. It is shown that the original idea to restrict the analysis to the so-called worst-case scenarios of a pure mass and a pure stiffness as environment can be too simplistic. Illustrative examples with mass-spring-damper systems fixed to the ground and floating objects as environments are made to demonstrate this in detail. In conclusion, this paper shows that embedding environment knowledge into the controller analysis/design is not straightforward and further research should be dedicated to determine which bounds should be used to obtain practically stable systems for different applications.

… and Automation, 2007 …, 2007

Abstract This paper describes the design of a new telepresence vision system developed to realize... more Abstract 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 ...

This article introduces a set of novel haptic guidance algorithms intended to provide intuitive a... more This article introduces a set of novel haptic guidance algorithms intended to provide intuitive and reliable assistance for electric wheelchair navigation through narrow or crowded spaces. The proposed schemes take hereto the non-holonomic nature and a detailed geometry of the wheelchair into consideration. The methods encode the environment as a set of collision-free circular paths and, making use of a model-free impedance controller, `haptically' guide the user along collision-free paths or away from obstructed paths or paths that simply do not coincide with the motion intended by the user. The haptic feedback plays a central role as it establishes a fast bilateral communication channel between user and wheelchair controller and allows a direct negotiation about wheelchair motion. If found unsatisfactory, suggested trajectories can always be overruled by the user. Relying on inputs from user modeling and intention recognition schemes, the system can reduce forces needed to move along intended directions, thereby avoiding unnecessary fatigue of the user. A commercial powered wheelchair was upgraded and feasability tests were conducted to validate the proposed methods. The potential of the proposed approaches was hereby demonstrated.

Advanced Robotics, 2007

In this paper the first haptic display capable of applying a true impulse to the operator is pres... more In this paper the first haptic display capable of applying a true impulse to the operator is presented. The applied impulse results in an immediate change of the user's momentum. Such a change is considered to be invaluable in making interactions with rigid virtual objects feel realistic. Conventional methods can only approximate impulses by outputting a constant force over a certain number of sample periods. The quality of these impulses is therefore limited by the maximum torque of the motor. At high interaction velocities these methods lose realism. The usage of large motors not only brings along safety issues, it also compromises the feeling of free motion. The new haptic display can generate an arbitrarily large impulse by continuously adapting the amount of momentum of a momentum wheel. At the predicted instant of contact with the virtual object, an electromagnetic tooth-clutch is engaged. The momentum wheel is mechanically connected to the handle of the haptic display and a real, but controlled, collision between the operator and momentum wheel is realized. The impulse generation part of the device is in fact the first 'generalized encountered haptic display'. Like typical encountered haptic displays its influence is not felt in free motion, but in contrast to them it is not limited to only static encounters, but effectively applicable to make encounters over a full velocity spectrum.

… in Computer-Human …, 2010

In this paper, the Bounded Environment Passivity method [1] is applied to a 3-channel controller.... more In this paper, the Bounded Environment Passivity method [1] is applied to a 3-channel controller. This method enables the design of teleoperation controllers that show passive behaviour for interactions with a bounded range of environments. The resulting tuning guidelines, derived analytically, provide interesting tuning flexibility, which allows to focus on different aspects of transparency. As telesurgery is the motivation behind this work, the focus lies on correctly reflecting the stiffness properties of the environment. A comparison between the transparency and stability properties of this 3channel controller and the same properties of the Position-Force controller demonstrates the interesting properties of the 3-channel controller. The theoretical results are verified experimentally on a 1 d.o.f. master-slave setup.

EuroHaptics Conference, 2007 and …, 2007

ABSTRACT In a previous paper, the authors presented the first haptic display capable of applying ... more ABSTRACT In a previous paper, the authors presented the first haptic display capable of applying directly an impulse to its operator. The resulting immediate change in momentum is considered invaluable to make interactions with rigid virtual objects feel realistic. The size of the impulse is controlled by adapting the amount of momentum of a momentum wheel. At the predicted instant of contact with the virtual object, an electromagnetic tooth clutch is engaged. The axes of momentum wheel and haptic handle are connected and a real but controllable collision between the operator and the momentum wheel is realized. This paper presents some tools to improve the accuracy of the impulses realized by the device. First, a detailed investigation of the dynamic properties of the tooth clutch is included. Based on this analysis, conclusions with respect to the range of display able impulses are made. The first order adaptive windowing method (FOAW) of Janabi-Sharifi is extended to a second order form (SOAW) and used to make accurate predictions of the instant and velocity of impact. Finally, the impulse generation capability of the device is utilized in a new method to estimate the inertia of the device's interacting components. All these tools are combined and a rigid virtual wall was implemented. Experimental results confirm the quality improvement with respect to traditional virtual walls

This paper presents a mechatronic analysis of a teleoperation system that provides haptic feedbac... more This paper presents a mechatronic analysis of a teleoperation system that provides haptic feedback. The analysis, based on the Bounded Environment Passivity method, describes the combined effect of the teleoperation controller and the master and slave hardware, including the effect of structural flexibilities, which have often been neglected in the domain of teleoperation. This results in rules of thumb for the design of the hardware and the tuning of the controller. As two of these rules of thumb pose a trade-off in hardware design, an unprecedented conceptual design optimization is described in a second part of this paper. The objective is to demonstrate the need for a mechatronic approach to the design of teleoperation systems in order to obtain maximal system performance.

… Perception, Devices and …, 2008

At present, surgical master-slave systems lack any kind of force feedback. Typically, controllers... more At present, surgical master-slave systems lack any kind of force feedback. Typically, controllers giving good stiffness transparency for soft environments cannot guarantee stability during hard contact. This paper presents a pragmatic method to avoid instability of a masterslave system during hard contacts, which does not affect the stiffness reflection for soft environments. The time derivative of the interaction force with the environment is used to detect a hard contact. Upon detection of a hard contact the force feedback is switched off and a virtual wall is activated at the master side in order to guarantee the perception of hard contact by the operator. The experiments demonstrate good stiffness transparency for soft environments, while the system remains stable for both soft and hard environments.

status: published, 2011

KULeuven. ...

Proceedings of the 5th …, 2004

… Sensing and Sensor …, 2009

Nowadays, master-slave systems are frequently used for minimally invasive surgery (MIS). Unfortun... more Nowadays, master-slave systems are frequently used for minimally invasive surgery (MIS). Unfortunately, these systems lack any kind of force feedback. Indeed, measuring forces in a surgical scene is not a trivial problem. This abstract describes the development of a force measurement system based on the overcoat principle [1] with additional passive positioning device for a slave robot arm with a passive wrist (ZEUS). Through this upgrade, a surgical teleoperator with 3D force feedback is realized. Preliminary experiments confirm the quality of the proposed approach.

Proceedings of the …, 2001

… :" New vistas and …, 2008

At present, surgical master-slave systems lack any kind of force feedback. In many cases especial... more At present, surgical master-slave systems lack any kind of force feedback. In many cases especially perception of the stiffness of tissue plays an essential role for diagnosis or intervention. This paper investigates methods to realize a reliable stiffness perception through a master-slave system. Two controllers, the classical Direct Force Feedback controller (DFF) and the Stiffness Reflecting Controller (SRC) are compared and experiments with linear springs and biological soft tissue are presented. Both controllers are non-passive, thus the stability of interactions with arbitrary passive environments cannot be guaranteed. Therefore, a pragmatic method is presented to avoid instability of the master-slave system during hard contacts, without compromising the quality of stiffness reflection for interactions with soft environments. The method consists of an observer which detects interactions with hard objects. Upon detection of a hard contact the force feedback is switched off and a rigid virtual wall is activated at the master site. This method guarantees the perception of the hard contact by the operator. The experiments demonstrate that the system remains stable for both soft and hard environments.

International Journal of Robotic Research, 2011

Bounded Environment Passivity, presented in this paper, allows one to design teleoperation system... more Bounded Environment Passivity, presented in this paper, allows one to design teleoperation systems that behave passive provided that the environment with which interaction takes place, belongs to an a-priori defined range of environments. The use of such a-priori knowledge on the environment reduces conservativeness with respect to classical design approaches. An additional advantage lies in its capability to get a clearer insight on which type of environments are problematic for the specific controller under investigation. On the basis of a case study, i.e. the well-known Position-Force controller, this paper describes and compares different passivity-based methods. First, the traditional methods of two-port passivity and absolute stability are applied. The restrictions of these methods to come up with useful design rules are explicitly demonstrated. Then, the Bounded Environment Passivity conditions of the Position-Force controller are derived. These conditions describe the relation between the specific controller implementation, the teleoperator dynamics and the environment characteristics. Additionally, the effects of structural resonance frequencies and low-pass filters, often present in realistic teleoperator setups, are described. This analysis reveals fundamental mechatronic rules of thumb for the design of a teleoperator system with a Position-Force control architecture. The theoretical results are verified experimentally on a 1-d.o.f.-teleoperation system.

Intelligent Robots and …, 2006

This paper deals with the haptic rendering of collisions between a human operator and rigid objec... more 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 operator's hand is being estimated online. A momentum wheel, under velocitycontrol, 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.