Το αντικείμενο της παρούσας διπλωματικής είναι η μοντελοποίηση, ο έλεγχος και η κατασκευή ενός επίπεδου ρομποτικού φιδιού βασισμένο σε υπολογιστικώς ανεξάρτητα μέρη τα οποία επικοινωνούν μέσω ασύρματου δικτύου \eng{Wifi} μεταξύ τους, καθώς και με εξωτερικές συσκευές για σκοπούς τηλεχειρισμού. Η κατασκευή βασίζεται στα ενσωματωμένα υπολογιστικά συστήματα \eng{Overo} της εταιρίας \eng{Gumstix}. Στόχος της διπλωματικής είναι η υλοποίηση της κίνησης του πλευρικού κυματισμού του φιδιού στο επίπεδο και η μελέτη της αποδοτικότητας του καθώς και η αντιμετώπιση του προβλήματος ελέγχου του. Στο πρώτο κεφάλαιο γίνεται μια αναφορά στην ανάγκη της ανάπτυξης ρομπότ εμπνευσμένα απο βιολογικούς οργανισμούς, συγκεκριμένα φιδιών, τις εφαρμογές τους στον πραγματικό κόσμο, την σχετική δουλειά καθώς και την συνεισφορά της παρούσας εργασίας. Στο δεύτερο κεφάλαιο παρουσιάζεται η ανάλυση της δυναμικής του επίπεδου φιδιού και επεξηγείται η σημαντική εξάρτηση από τα διάφορα μοντέλα τριβής για την κίνηση του ρομπότ στο επίπεδο. Στο τρίτο κεφάλαιο αναλύεται το πρόβλημα ελέγχου και παρουσιάζονται προτεινόμενοι ελεγκτές για την κίνηση της πλευρικής κυμάτωσης, επεκταμένοι για σύγκλισης τροχίας καθώς και τα αποτελέσματα της προσωμείωσης με βάση τους συγκεκριμένους νόμους ελέγχου. Στη συνέχεια στο τέταρτο κεφάλαιο παρουσιάζονται τα διάφορα στάδια κατασκευής του ρομπότ από τον σχεδιασμό του σκελετού, στη λογική των ανεξάρτητων μελών,τα κατασκευαστικά μέρη κάθε μέλους, μέχρι την αρχιτεκτονική του προγραμματισμού του και του χειρισμού του. Τέλος,στο πέμπτο κεφάλαιο παρατίθονται τα πειραματικά αποτελέσματα και σχολιάζεται η απόδοση της κατασκευής. / The subject of this thesis is the modelling, control and development of a planar snake-like robot based on modular links that communicate to each other via a Wifi network, as well as to other devices in order to remote control it. The links are based on the embedded computer-on-module Overo from the company Gumstix. The aim of this thesis is the implementation of the lateral undulation locomotion of snakes on a planar surface and the study of its efficiency as well as to present a control method for it. The first chapter points out the need of developing robots based on various existing biological organisms, specifically snakes ,their applications to real-world problems, the related work and the contribution of the current thesis. The second chapter contains the dynamic analysis of planar snake robots and explains the strong dependence on friction models for the movement of snakes on planar surfaces. In the third chapter, a control law is proposed to achieve lateral undulation as well as an extension of it to achieve trajectory tracking and the simulation results based on these control laws are presented. The fourth chapter contains the various stages of the development of the snake robot, from the design of its body, to the concept of modular links, to the programming architecture of them and their remote control. Finally, the fifth chapter presents the experimental results and comments on the efficiency of the developed robot.

This thesis outlines the evolution of computer hardware and software architectures which are suitable for the programming and control of modular robots and distributed manipulators. Fundamental aspects of automating manufacturing functions are considered and the use of flexible machines, constructed from components of a family of mechanical modules and associated control system elements, are proposed. Many of the features of these flexible machines can be identified with those of conventional industrial robots. However a broader class of manufacturing machine is represented in as much as the industrial user defines the kinematics and dynamics of the manipulator. Such flexible machines can be referred to as "modular robots" or, where the mechanical modules are arranged in concurrently operating but mechanically decoupled groups, as "distributed manipulators". The main body of the work reported centred on the design of a family of computer control system elements which can serve a range of distributed manipulator and modular robot forms. These control system elements, whose cost is commensurate with the size and complexity of the manipulator's mechanical configuration, necessarily have many of the features found in robot controllers but also require properties of reconfigurability, programmability, and control system performance for the considerable array of manipulator configurations which can be constructed.

The ultimate goal in robotic systems is to develop machines that learn for themselves based on experience. In order to achieve on-line learning some software tools are needed to allow the robots to continually adapt their behaviour in order to constantly optimise their performance. This thesis presents research work focused on path planning for mobile robots with the objective of generating optimal paths for any type of mobile robot in an environment containing any number of static obstacles of any shape. The research specifically recognises that an optimal path can be defined according to several criteria including distance, time, energy consumption and risk. The easiest and most commonly used measure is to minimise distance, but this does not by itself optimise task performance, and the other criteria are generally far more important. Distance is used mainly because there is no direct method to optimise time, energy and risk as they depend on the characteristics of the robot and the environment. This is solved in this research by using a set of Artificial Intelligence tools working together to perform an optimisation process strictly on the criteria selected. The path planning system developed consists of an original and novel two-stage 4 process comprising generation followed by optimisation. Path generation is achieved using cellular automata whose behaviour has been determined by a genetic algorithm. A program called Rutar has been written in which the best behaviour found by the genetic algorithm is encoded, and it has been tested and shown to infallibly generate all the non-redundant paths between any two points around any obstacles. An interesting and valuable feature of Rutar is that the time taken to generate paths depends only on the amount of free space available in which the robot can move and therefore the more obstacles there are present, and hence the more complex the layout, the faster the execution time. The paths generated are sub-optimal solutions, which are then optimised according to the user's selection of a combination of Time, Energy, Distance and Risk criteria. The optimisation process is performed by another genetic algorithm. The original scheme used in this work allows any combination of all the desired criteria in a single optimisation process, allowing it to handle very complex non-linear problems. All of the optimisation criteria can be used in situations where the environment and the robot are considered to be unchanged during the interval in which the robot moves. This optimisation can be performed either off-line or on-line. However, the ability of the developed system to generate and optimise the paths very fast provide an opportunity for dynamic path optimisatiorý which ultimately can lead to on-line learning. This potential of the tools developed for the path planning system is explored and recommendations for further exploitation are made.

No description available.

Nuclear decommissioning involves the use of remotely deployed mobile vehicles and manipulators controlled via teleoperation systems. Manipulators are used for tooling and sorting tasks, and mobile vehicles are used to locate a manipulator near to the area that it is to be operated upon and also to carry a camera into a remote area for monitoring and assessment purposes. Teleoperations in hazardous environments are often hampered by a lack of visual information. Direct line of sight is often only available through small, thick windows, which often become discoloured and less transparent over time. Ideal camera locations are generally not possible, which can lead to areas of the cell not being visible, or at least difficult to see. Damage to the mobile, manipulator, tool or environment can be very expensive and dangerous. Despite the advances in the recent years of autonomous systems, the nuclear industry prefers generally to ensure that there is a human in the loop. This is due to the safety critical nature of the industry. Haptic interfaces provide a means of allowing an operator to control aspects of a task that would be difficult or impossible to control with impoverished visual feedback alone. Manipulator endeffector force control and mobile vehicle collision avoidance are examples of such tasks. Haptic communication has been integrated with both a Schilling Titan II manipulator teleoperation system and Cybermotion K2A mobile vehicle teleoperation system. The manipulator research was carried out using a real manipulator whereas the mobile research was carried out in simulation. Novel haptic communication generation algorithms have been developed. Experiments have been conducted using both the mobile and the manipulator to assess the performance gains offered by haptic communication. The results of the mobile vehicle experiments show that haptic feedback offered performance improvements in systems where the operator is solely responsible for control of the vehicle. However in systems where the operator is assisted by semi autonomous behaviour that can perform obstacle avoidance, the advantages of haptic feedback were more subtle. The results from the manipulator experiments served to support the results from the mobile vehicle experiments since they also show that haptic feedback does not always improve operator performance. Instead, performance gains rely heavily on the nature of the task, other system feedback channels and operator assistance features. The tasks performed with the manipulator were peg insertion, grinding and drilling.

Η παρούσα διπλωματική εργασία μελετά το θέμα της πλοήγησης ενός ρομποτικού οχήματος με στόχο την εξερεύνηση μιας περιοχής η οποία είτε είναι ελεύθερη είτε περιέχει εμπόδια σε γνωστές θέσεις. Για αυτό το πρόβλημα εξερεύνησης, υπάρχει επίσης ένας περιορισμός που αφορά το όχημα: θα πρέπει αυτό κατά τη διάρκεια της εξερεύνησης να διατηρεί την επικοινωνία του με ένα σταθερό σταθμό βάσης. Για να αντιμετωπιστεί το σύνθετο αυτό θέμα και για να αναπτυχθεί ένας αλγόριθμος για την πειραματική διαδικασία, αρχικά θεωρήθηκε ένα μοντέλο κινοδυναμικών εξισώσεων για το ρομποτικό όχημα. Στη συνέχεια, για το μοντέλο αυτό παρουσιάστηκε ένας μη-γραμμικός ελεγκτής που σχεδιάστηκε για παρακολούθηση επιθυμητών τροχιών. Για να υλοποιηθεί ο εν λόγω ελεγκτής, ήταν απαραίτητος ο εντοπισμός της θέσης του ρομποτικού οχήματος και αυτό επετεύχθη πειραματικά μέσω επεξεργασίας εικόνας. Το ρομπότ αναγνωριζόταν στις εικόνες που λαμβάνονταν από μια κάμερα παρακολούθησης, και με κατάλληλη γεωμετρική ανάλυση ήταν εφικτή η εκτίμηση της θέσης και του προσανατολισμού του ρομπότ. Για την επικοινωνία του ρομπότ με το σταθμό βάσης αναπτύχθηκε ασύρματο δίκτυο ΙΕΕΕ 802.15.4 και για την αξιολόγηση της ποιότητας της επικοινωνίας αυτής χρησιμοποιήθηκε το Received Signal Strength Indicator (RSSI). Ο αλγόριθμος σχεδιασμού διαδρομής, ο οποίος καθοδηγεί το ρομπότ στο περιβάλλον με στόχο την εξερεύνηση όλων των ελεύθερων σημείων, αξιοποίησε την εκ των προτέρων γνώση για τα εμπόδια, καθώς και τις μετρήσεις του RSSI κατά τη διάρκεια του πειράματος, ώστε να πετύχει το στόχο του. Πιο συγκεκριμένα, χρησιμοποιήθηκε μια on-line μέθοδος που πετυχαίνει όσο το δυνατόν μεγαλύτερη κάλυψη του περιβάλλοντος υπό τον περιορισμό της επικοινωνίας, έχοντας σαν οδηγό μια προσχεδιασμένη διαδρομή εξερεύνησης. Στο τέλος της εργασίας παρουσιάζονται πειραματικά αποτελέσματα και συμπεράσματα για τα διάφορα αντικείμενα της μελέτης. / The present diploma thesis studies the subject of the navigation of a robotic vehicle for the exploration of an environment which is either free or contains obstacles in known locations. For this area coverage problem, there is an additional constraint: during the exploration the robot must maintain its communication with a stationary base station. In order to address this complex subject and to develop an algorithm for the experimental procedure, a kinodynamic model is initially assumed for the robotic vehicle. Then, a non-linear controller is designed for this model to achieve tracking of reference trajectories. For the implementation of this controller, the localization of the robotic vehicle was necessary and it was achieved via image processing during the experiments. The robot was recognized in images taken by a surveillance camera, and after appropriate geometric analysis, it was possible to estimate the position and the orientation of the robot. For the robot-base communication, an IEEE 802.15.4 wireless network was developed and in order to evaluate the quality of this communication, the Received Signal Strength Indicator (RSSI) was utilised. The path planning algorithm, which navigates the robot inside the environment to explore all the available locations, achieved its goal by combining the prior knowledge about the obstacles and the RSSI measurements during the experiments. Specifically, an on-line method that achieves maximum possible coverage of the environment under the communication constraint was employed, using a pre-designed exploring path as a guide. At the end of this thesis, some experimental results and conclusions are presented concerning the versatile subjects of this study.

Le développement de comportements utiles pour les robots complexes, tel que des humanoïdes, s'avère difficile. La commande corps-complet à base de modèle allège en partie ces difficultés, en permettant la composition des comportements corps-complets complexes à partir de plusieurs tâches atomiques effectuées simultanément sur le robot. Cependant, des hypothèses et erreurs de modélisation, faites pendant la planification des tâches, peuvent produire des combinaisons infaisables/incompatibles quand exécutées sur le robot, créant des mouvements corps-complet imprévisibles, et probablement dangereux. L'objectif de ce travail est de mieux comprendre ce qui rend les tâches infaisables ou incompatibles et de développer des méthodes automatiques pour améliorer ces problèmes pour que les mouvements corps-complets puissent être accomplis comme prévu. Nous commençons par construire un formalisme permettant d'analyser quand les tâches sont faisables et compatibles étant données les contraintes de commande. En utilisant les métriques de faisabilité et compatibilité à base de modèle, nous démontrons comment optimiser les tâches avec des outils de commande prédictive non-linéaire ainsi que les inconvénients de cette approche. Afin de surmonter ces faiblesses, une boucle d'optimisation est formulée, qui améliore automatiquement la faisabilité et compatibilité des tâches via la recherche de politique sans modèle en conjonction avec la commande corps-complets à base de modèle. À travers une série d'expériences simulées et réelles, nous montrons que la simple optimisation de faisabilité et compatibilité des tâches nous permet de réaliser des mouvements corps-complets utiles. / Producing useful behaviors on complex robots, such as humanoids, is a challenging undertaking. Model-based whole-body control alleviates some of this difficulty by allowing complex whole-body motions to be broken up into multiple atomic tasks, which are performed simultaneously on the robot. However, modeling errors and assumptions, made during task planning, often result in infeasible and/or incompatible task combinations when executed on the robot. Consequently, there is no guarantee that the prescribed tasks will be accomplished, resulting in unpredictable, and most likely, unsafe whole-body motions. The objective of this work is to better understand what makes tasks infeasible or incompatible, and develop automatic methods of improving on these two issues so that the overall whole-body motions may be accomplished as planned. We start by building a concrete analytical formalism of what it means for tasks to be feasible with the control constraints and compatible with one another. Using the model-based feasibility and compatibility metrics, we demonstrate how the tasks can be optimized using non-linear model predictive control, while also detailing the shortcomings of this model-based approach. In order to overcome these weaknesses, an optimization loop is designed, which automatically improves task feasibility and compatibility using model-free policy search in conjunction with model-based whole-body control. Through a series of simulated and real-world experiments, we demonstrate that by simply optimizing the tasks to improve both feasibility and compatibility, complex and useful whole-body motions can be realized.

L'exploration d'un environnement inconnu par un robot mobile est un vaste domaine de recherche visant à comprendre et implémenter des modèles d'exploration efficaces, rapides et pertinents. Cependant, depuis les années 80, l'exploration ne s'est plus contentée de la seule détermination de la topographie d'un espace : à la composante spatiale a été couplée une composante sémantique du monde exploré. En effet, en addition aux caractéristiques physiques de l'environnement — murs, obstacles, chemins empruntables ou non, entrées et sorties — permettant au robot de se créer une représentation interne du monde grâce à laquelle il peut s'y déplacer, existent des caractéristiques dynamiques telles que l'apparition d'événements audiovisuels. Ces événements sont d'une grande importance en cela qu'ils peuvent moduler le comportement du robot en fonction de leur localisation dans l'espace — aspect topographique — et de l'information qu'ils portent — aspect sémantique. Bien qu'imprédictibles par nature (puisque l'environnement est inconnu) tous ces événements ne sont pas d'égale importance : certains peuvent porter une information utile au robot et à sa tâche d'exploration, d'autres non. Suivant les travaux sur les motivations intrinsèques à explorer un environnement inconnu et puisant son inspiration de phénomènes neurologiques, ce travail de thèse a consisté en l'élaboration du modèle Head Turning Modulation (HTM) visant à donner à un robot doté de mouvements de tête la capacité de déterminer l'importance relative de l'apparition d'un événement audiovisuel dans un environnement inconnu en cours d'exploration. Cette importance a été formalisée sous la forme de la notion de Congruence s'inspirant principalement (i) de l'entropie de Shannon, (ii) du phénomène de Mismatch Negativity et (iii) de la Reverse Hierarchy Theory. Le modèle HTM, créé dans le cadre du projet européen Two!Ears, est un paradigme d'apprentissage basé sur (i) une auto-supervision (le robot décide lorsqu'il est nécessaire d'apprendre ou non), (ii) une contrainte de temps réel (le robot apprend et réagit aussitôt que des données sont perçues), et (iii) une absence de données a priori sur l'environnement (il n'existe pas de vérité à apprendre, seulement la réalité perçue de l'environnement à explorer). Ce modèle, intégré à l’ensemble du framework Two!Ears, a été entièrement porté sur un robot mobile pourvu d'une vision binoculaire et d'une audition binaurale. Le modèle HTM couple ainsi une approche montante traditionnelle d’analyse des signaux perceptifs (extractions de caractéristiques, reconnaissance visuelle ou auditive, etc.) à une approche descendante permettant, via la génération d’une action motrice, de comprendre et interpréter l’environnement audiovisuel du robot. Cette approche bottom-up/top-down active est ainsi exploitée pour moduler les mouvements de tête d’un robot humanoïde et étudier l'impact de la Congruence sur ces mouvements. Le système a été évalué via des simulations réalistes, ainsi que dans des conditions réelles, sur les deux plateformes robotiques du projet Two!Ears. / The exploration of an unknown environement by a mobile robot is a vast research domain aiming at understanding and implementing efficient, fast and relevant exploration models. However, since the 80s, exploration is no longer restricted to the sole determination of topography a space: to the spatial component has been coupled a semantic one of the explored world. Indeed, in addition to the physical characteristics of the environment — walls, obstacles, usable paths or not, entrances and exits — allowing the robot to create its own internal representation of the world through which it can move in it, exist dynamic components such as the apparition of audiovisual events. These events are of high importance for they can modulate the robot's behavior through their location in space — topographic aspect — and the information they carry — semantic aspect. Although impredictible by nature (since the environment is unknown) all these events are not of equal importance: some carry valuable information for the robot's exploration task, some don't. Following the work on intrinsic motivations to explore an unknown environment, and being rooted in neurological phenomenons, this thesis work consisted in the elaboration of the Head Turning Modulation (HTM) model aiming at giving to a robot capable of head movements, the ability to determine the relative importance of the apparition of an audioivsual event. This "importance" has been formalized through the notion of Congruence which is mainly inspired from (i) Shannon's entropy, (ii) the Mismatch Negativity phenomenon, and (iii) the Reverse Hierarchy Theory. The HTM model, created within the Two!Ears european project, is a learning paradigm based on (i) an auto-supervision (the robot decides when it is necessary or not to learn), (ii) a real-time constraint (the robot learns and reacts as soon as data is perceived), and (iii) an absence of prior knowledge about the environment (there is no "truth" to learn, only the reality of the environment to explore). This model, integrated in the overal Two!Ears framework, has been entirely implemented in a mobile robot with binocular vision and binaural audition. The HTM model thus gather the traditional approach of ascending analysis of perceived signals (extraction of caracteristics, visual or audio recognition etc.) to a descending approach that enables, via motor actions generation in order to deal with perception deficiency (such as visual occlusion), to understand and interprete the audiovisual environment of the robot. This bottom-up/top-down active approach is then exploited to modulate the head movements of a humanoid robot and to study the impact of the Congruence on these movements. The system has been evaluated via realistic simulations, and in real conditions, on the two robotic platforms of the Two!Ears project.

Le travail présenté s'intéresse à la problématique générale de la mise en oeuvre de mains robotiques à haut niveau de dextérité. Dans ce contexte, nous nous intéressons à la synthèse de prise d'objets en prenant en compte les contraintes propres à la tâche de manipulation visée. La manière dont l'objet est saisi a une importance capitale sur le bon déroulement d'une tâche.Le développement d'algorithmes capables de générer automatiquement des prises optimales implique avant tout la nécessité de définir la notion de prise optimale au regard de la tâche cible. Pour répondre à ce problème, la communauté scientifique propose dans la littérature de nombreux critères de qualité et continue à en développer de nouveaux. Dans cette thèse, nous présentons une extension des travaux proposés avec une étude approfondie de ces critères dans le cadre de la manipulation dextre. Ces critères sont évalués avec une main robotique entièrement actionnée à quatre doigts et seize articulations.Nous quantifions l'efficacité de ces critères dans le cadre de la réalisation de tâches de manipulation fine avec trois types d'objets spécifiques. Deux groupes de critères sont étudiés : d'une part des critères s'appuyant uniquement sur la position des points de contact, et, d'autre part, des critères prenant en compte la cinématique du préhenseur. Cette étude nous a permis de sélectionner un ensemble de critères pertinents pour résoudre le problème de synthèse de prise que nous avons mis en oeuvre dans un processus basé sur une approche évolutionnaire. Cette approche a été validée dans l'environnement de simulation OpenRAVE, puis expérimentalement avec la nouvelle main RoBioSS. / The work presented in this thesis concerns object grasping with dexterous robotic hands. In this work, we are going to focus on the grasp synthesis problem by taking into account the in-hand manipulation task. The initial grasp has a capital role for the successful completion of a given task.In order to develop algorithms which are able to generate automatically correct grasps for a manipulation task, we need to define suitable grasp quality metrics to assess the validity of a grasp. Throughout the years, a large variety of quality measures have been proposed in the literature and researchers keep on developing new ones. However those quality measures are generally developed for simple grippers and for grasping tasks. In this thesis, we will extend the study of selected interesting grasp quality measures for in-hand manipulation tasks. These quality measures will be evaluated on a four finger robotic hand with sixteen fully actuated degrees of freedom.We will assess the chosen quality measures for in-hand manipulation tasks with three different carefully selected type of objects. The quality metrics are classified in two groups, first one focuses exclusively on the location of contact points and the second one considers the kinematics of the robotic hand. The review of these quality measures led us to select the ones meaningful for solving the grasp synthesis problem for in-hand manipulation. The grasping pipeline implemented to generate the correct grasps is based on an evolutionary approach using a mix of the selected quality measures. The proposed approach was tested in the OpenRAVE robotic simulator and also validated experimentally with the new RoBioSS hand.

La présente thèse traite de l'utilisation de retours haptiques pour fournir des informations aux chirurgiens durant des opérations de chirurgie minimalement invasive dans le but de les aider à améliorer leurs gestes.De meilleurs résultats pour les patients on amené la chirurgie minimalement invasive à devenir le standard pour bon nombre d'interventions. Cependant, la perte de perception de profondeur, la coordination main-oeil compliquée ainsi que les distorsions de sensations haptiques compliquent largement la tâche pour le chirurgien. Nous explorons le potentiel de retours haptiques pour intuitivement assister les chirurgiens durant des gestes de chirurgie minimalement invasive. Les formes de retour évaluées sont principalement haptiques (tactiles et kinesthésiques), avec des comparaisons à des retours visuels et multi-modaux (combinaisons de retours visuels et haptiques).Nos expériences dans le domaine de la navigation d'outils de chirurgie montrent des résultats encourageants quand aux bénéfices obtenus par des retours haptiques en termes d'amélioration de la qualité du geste chirurgical. Les guides par "virtual fixtures" montrent une nette supériorité par rapport aux autres formes de retour étudiées, cependant les retours vibrotactiles permettent aussi des améliorations notables. Des travaux parallèles sur le retour d'informations au sujet des efforts d'intéraction en bout d'outils a mis en évidence des différences importantes en termes des exigences de conception pour le retour tactile. Ceci nous a permis d'effectuer une conception et validation préliminaire de retours tactiles spécifiques à des applications de maitrise d'efforts, en utilisant l'exemple de la suture. / The present thesis focuses on the use of haptic feedback technologies to provide information to surgeons during laparoscopic or minimal access surgery (MAS) with the aim of assisting them in improving their gestures.Better overall outcomes for patients have led MAS to become standard for many surgical interventions. However, loss of visual depth perception, difficult hand-eye coordination and distorted haptic sensation seriously complicate this task for the surgeon. We explore the potential of haptic cues for intuitively assisting surgeons during MAS gestures. Evaluated forms of feedback mainly focus on haptic (tactile and kinaesthetic) cues, but include comparisons to visual and multi-modal combined haptic and visual cues.Experiments on surgical tool navigation show encouraging results for the benefit of haptic cues in improving surgical gestures, with clear superiority of soft guidance virtual fixtures over other forms of feedback. However, promising results for the use of vibrotactile feedback are also obtained. These results are confirmed in preliminary experiments on tool navigation in preliminary experiments on tool navigation during a laparoscopic cutting training task.Parallel work on feeding back interaction forces highlighted significant differences in the usability and design requirements for tactile cues when compared to instrument navigation applications. This led us to design and perform preliminary testing on tactile cues appropriate force information in the case of intra-corporeal suture knot tying.