Micromanipulation-force feedback pushing

In micromanipulation applications, it is often desirable to position and orient polygonal micro-objects lying on a planar surface. Pushing micro-objects using point contact provides more flexibility and less complexity compared to pick and place operation. Due to the fact that in micro-world surface forces are much more dominant than inertial forces and these forces are distributed unevenly, pushing through the center of mass of the micro-object will not yield a pure translational motion. In order to translate a micro-object, the line of pushing should pass through the center of friction. Moreover, due to unexpected nature of the frictional forces between the micro-object and substrate, the maximum force applied to the micro-object needs to be limited to prevent any damage either to the probe or micro-object. In this dissertation, a semi-autonomous manipulation scheme is proposed to push microobjects with human assistance using a custom built tele-micromanipulation setup to achieve pure translational motion. The pushing operation can be divided into two concurrent processes: In one process human operator who acts as an impedance controller to switch between force-position controllers and alters the velocity of the pusher while in contact with the micro-object through scaled bilateral teleoperation with force feedback. In the other process, the desired line of pushing for the micro-object is determined continuously so that it always passes through the varying center of friction. Visual feedback procedures are adopted to align the resultant velocity vector at the contact point to pass through the center of friction in order to achieve pure translational motion of the micro-object. Experimental results are demonstrated to prove the effectiveness of the proposed controller along with nanometer scale position control, nano-Newton range force sensing, scaled bilateral teleoperation with force feedback

Control Architectures for Robotic Assistance in Beating Heart Surgery

Tese de doutoramento em Engenharia Electrotécnica e de Computadores, no ramo de especialização em Automação e Robótica, apresentada ao Departamento de Engenharia Electrotécnica e de Computadores da Faculdade de Ciências e Tecnologia da Universidade de CoimbraDoenças cardiovasculares são a primeira causa de morte no mundo. Todos os anos mais de 17 milhões de pessoas morrem, representando 29% do número total de mortes. As doenças coronárias são as mais críticas, atingindo mais de 7.2 milhões de mortes. Para reduzir o risco de morte, o "bypass" coronário é a intervenção cirúrgica mais comum. Atualmente este procedimento envolve uma esternotomia mediana e um "bypass" cardiopulmonar, permitindo que uma máquina externa implemente as funções de oxigenação e bombeamento de sangue. Contudo, esta máquina externa é fonte de muitas complicações pós-operatórias, incluindo a morte de pacientes. Estes problemas motivam o estudo e desenvolvimento de técnicas cirúrgicas sem parar o funcionamento do coração. Nestes casos, os batimentos cardíacos e a respiração representam as principais fontes de perturbação. Foram desenvolvidos estabilizadores mecânicos para diminuir localmente o movimento cardíaco. Colocado numa região de específica (por exemplo, na artéria coronária), estes estabilizadores limitam o movimento por pressão e sucção. Apesar dos melhoramentos feitos ao longo dos anos, ainda existe um movimento residual considerável, e o cirurgião tem que os compensar manualmente. Torna-se então natural incluir dispositivos robóticos para ajudar na prática médica, melhorando a precisão, segurançae conforto de tarefas cirúrgicas. O sistema cirúrgico da Vinci é atualmente o sistema robótico mais avançado para a prática médica, com elevado desempenho em tarefas de destreza, precisão e segurança, apesar de não fornecer soluções de realimentação táctil, nem de compensação automática de movimentos fisiológicos. O trabalho desta tese é na área da robótica para cirurgias cardíacas com o coração a bater. Baseada na realimentação da força, esta tese explora novas arquiteturas de controlo com compensação automática dos movimentos cardíacos. São feitos testes experimentais em cenários muito realistas, sem utilizar seres vivos. Um robô denominado "Heartbox" equipado com um coração real reproduz movimentos cardíacos, enquanto que outro robô manipulador aplica forças cirúrgicas nesse coração com batimento artificial. As forças de interação fornecem realimentação de contacto ao cirurgião. O principal desafio científico deste trabalho é a ligação de técnicas de compensação autónoma de movimentos fisiológicos com controlo de força e realimentação haptica.Cardiovascular diseases are the first cause of mortality in the world. More than 17 million people die every year, representing 29% of all global deaths. Among these, coronary heart diseases are the most critical ones, reaching up to 7.2 million deaths. To reduce the risk of death the coronary artery bypass grafting (CABG) is the most common surgical intervention. Currently, the procedure involves a median sternotomy, an incision in the thorax allowing a direct access to the heart, and a cardiopulmonary bypass (CPB), where heart and lung functionalities are performed by an extracorporal machine. Unfortunately the heart-lung machine is the greatest source of complications and post-operatory mortality for patients. Problems involved have motivated beating heart surgery that circumvent CPB procedure. Heartbeats and respiration represent the two main sources of disturbances during off-pump surgery. Mechanical stabilizers have been conceived for locally decreasing heart motion. Placed around a region of interest (e.g., coronary artery), these stabilizers constraint the motion by suction or pressure. Despite many improvements done over the years, considerable residual motion still remains and the surgeon have to manually compensate them. Robotic assistance has the potential to offer significant improvements to the medical practice in terms of precision, safety and comfort. Theda Vinci surgical system is the most popular and sophisticated. Although it has considerably improved dexterity, precision and safety, no solution for restoring tactile feedback to the surgeon exists and physiological motion compensation still needs to be manually canceled by the surgeon. The work presented in this thesis focus on robotic assistance for beating heart surgery. Based on force feedback, we designed new control architectures providing autonomous physiological motion compensation. Experimental assessments have been performed through a realistic scenario. A Heartbox robot equipped with an \textit{ex vivo} heart reproduces heart motion and a robot arm generates desired surgical forces on the moving heart. Interaction forces provide the haptic feedback for the surgeon. Merging autonomous motion compensation techniques with force control and haptic feedback is a major scientific challenge that we tackle in this work.FCT - SFRH/BD/74278/201

Multisensory self-motion processing in humans

Humans obtain and process sensory information from various modalities to ensure successful navigation through the environment. While visual, vestibular, and auditory self-motion perception have been extensively investigated, studies on tac-tile self-motion perception are comparably rare. In my thesis, I have investigated tactile self-motion perception and its interaction with the visual modality. In one of two behavioral studies, I analyzed the influence of a tactile heading stimulus intro-duced as a distractor on visual heading perception. In the second behavioral study, I analyzed visuo-tactile perception of self-motion direction (heading). In both studies, visual self-motion was simulated as forward motion over a 2D ground plane. Tactile self-motion was simulated by airflow towards the subjects’ forehead, mimicking the experience of travel wind, e.g., during a bike ride. In the analysis of the subjects’ perceptual reports, I focused on possible visuo-tactile interactions and applied dif-ferent models to describe the integration of visuo-tactile heading stimuli. Lastly, in a functional magnetic resonance imaging study (fMRI), I investigated neural correlates of visual and tactile perception of traveled distance (path integration) and its modu-lation by prediction and cognitive task demands. In my first behavioral study, subjects indicated perceived heading from uni-modal visual (optic flow), unimodal tactile (tactile flow) or from a combination of stimuli from both modalities, simulating either congruent or incongruent heading (bimodal condition). In the bimodal condition, the subjects’ task was to indicate visually perceived heading. Hence, here tactile stimuli were behaviorally irrelevant. In bimodal trials, I found a significant interaction of stimuli from both modalities. Visually perceived heading was biased towards tactile heading direction for an offset of up to 10° between both heading directions. The relative weighting of stimuli from both modalities in the visuo-tactile in-teraction were examined in my second behavioral study. Subjects indicated per-ceived heading from unimodal visual, unimodal tactile and bimodal trials. Here, in bimodal trials, stimuli form both modalities were presented as behaviorally rele-vant. By varying eye- relative to head position during stimulus presentation, possi-ble influences of different reference frames of the visual and tactile modality were investigated. In different sensory modalities, incoming information is encoded rela-tive to the reference system of the receiving sensory organ (e.g., relative to the reti-na in vision or relative to the skin in somatosensation). In unimodal tactile trials, heading perception was shifted towards eye-position. In bimodal trials, varying head- and eye-position had no significant effect on perceived heading: subjects indicated perceived heading based on both, the vis-ual and tactile stimulus, independently of the behavioral relevance of the tactile stimulus. In sum, results of both studies suggest that the tactile modality plays a greater role in self-motion perception than previously thought. Besides the perception of travel direction (heading), information about trav-eled speed and duration are integrated to achieve a measure of the distance trav-eled (path integration). One previous behavioral study has shown that tactile flow can be used for the reproduction of travel distance (Churan et al., 2017). However, studies on neural correlates of tactile distance encoding in humans are lacking en-tirely. In my third study, subjects solved two path integration tasks from unimodal visual and unimodal tactile self-motion stimuli. Brain activity was measured by means of functional magnetic resonance imaging (fMRI). Both tasks varied in the engagement of cognitive task demands. In the first task, subjects replicated (Active trial) a previously observed traveled distance (Passive trial) (= Reproduction task). In the second task, subjects traveled a self-chosen distance (Active trial) which was then recorded and played back to them (Passive trial) (= Self task). The predictive coding theory postulates an internal model which creates predictions about sensory outcomes-based mismatches between predictions and sensory input which enables the system to sharpen future predictions (Teufel et al., 2018). Recent studies sug-gested a synergistical interaction between prediction and cognitive demands, there-by reversing the attenuating effect of prediction. In my study, this hypothesis was tested by manipulating cognitive demands between both tasks. For both tasks, Ac-tive trials compared to Passive trials showed BOLD enhancement of early sensory cortices and suppression of higher order areas (e.g., the intraparietal lobule (IPL)). For both modalities, enhancement of early sensory areas might facilitate task solv-ing processes at hand, thereby reversing the hypothesized attenuating effect of pre-diction. Suppression of the IPL indicates this area as an amodal comparator of pre-dictions and incoming self-motion signals. In conclusion, I was able to show that tactile self-motion information, i.e., tactile flow, provides significant information for the processing of two key features of self-motion perception: Heading and path integration. Neural correlates of tactile path-integration were investigated by means of fMRI, showing similarities between visual and tactile path integration on early processing stages as well as shared neu-ral substrates in higher order areas located in the IPL. Future studies should further investigate the perception of different self-motion parameters in the tactile modali-ty to extend the understanding of this less researched – but important – modality

Bilateral Control - Operational enhancements

A succinct definition of the word bilateral is having two sides [1]. In robotics the term bilateral control is used to define the specific interaction of two systems by means of position and/or force. Bilateral systems are composed of two sides named master and slave side. The aim of such an arrangement is such that position command dictated by master side is followed by a slave side, and at the same time the force sensation of the remote environment experienced by slave is transferred to the mater - human operator. This way bilateral system may be perceived as an “impendanceless” extension of the human operator providing the touch information of the remote (or inaccessible) environment. In a sense bilateral systems are a mechatronics extension of the teleoperated systems. There are many applications of this structure which requires critical manipulations like nuclear material handling, robotic surgery, and micro material handling and assembly. In all these applications a human operator is required to have as close to real as possible contact with object that should be manipulated or in other word the telepresence of the operator is required. In this thesis work various important aspects of bilateral control systems are discussed. These aspects include problems of (i) acquisition of information on master and slave side, (ii) analysis and selection of the proper structure of the control systems to ensure fidelity of the system behavior. The work has been done to enhance the performance of the bilateral control system by: (i) Enhancing position and velocity measurements obtained from incremental encoder having limited number of pulses per revolution. A few algorithms are investigated and their improvements are proposed; (ii) Increasing system robustness by using acceleration controller based on disturbance observer. The robust system design based on disturbance observer is known but its application requires very fast sampling and high bandwidth of the observer. In this work the discrete time realization of the observer is presented in details and selection of the necessary filters and the sampling so to achieve a good trade-off for observer realization is discussed and experimentally confirmed; (iii) Increasing the bandwidth of force sensation by using reaction force observer. For transparent operation of a bilateral system the bandwidth of force sensation is of the major interest. All force sensors do have relatively slow dynamics and observer based structures seems providing better behavior of the overall system. In this work the observer of the interaction force is examined and design procedure is established. In order to verify all of the proposed ideas a versatile bilateral system is designed and built and experimental verification is carried out on this system

Haptics in Robot-Assisted Surgery: Challenges and Benefits

Robotic surgery is transforming the current surgical practice, not only by improving the conventional surgical methods but also by introducing innovative robot-enhanced approaches that broaden the capabilities of clinicians. Being mainly of man-machine collaborative type, surgical robots are seen as media that transfer pre- and intra-operative information to the operator and reproduce his/her motion, with appropriate filtering, scaling, or limitation, to physically interact with the patient. The field, however, is far from maturity and, more critically, is still a subject of controversy in medical communities. Limited or absent haptic feedback is reputed to be among reasons that impede further spread of surgical robots. In this paper objectives and challenges of deploying haptic technologies in surgical robotics is discussed and a systematic review is performed on works that have studied the effects of providing haptic information to the users in major branches of robotic surgery. It has been tried to encompass both classical works and the state of the art approaches, aiming at delivering a comprehensive and balanced survey both for researchers starting their work in this field and for the experts

Contributions to shared control and coordination of single and multiple robots

L’ensemble des travaux présentés dans cette habilitation traite de l'interface entre un d'un opérateur humain avec un ou plusieurs robots semi-autonomes aussi connu comme le problème du « contrôle partagé ».Le premier chapitre traite de la possibilité de fournir des repères visuels / vestibulaires à un opérateur humain pour la commande à distance de robots mobiles.Le second chapitre aborde le problème, plus classique, de la mise à disposition à l’opérateur d’indices visuels ou de retour haptique pour la commande d’un ou plusieurs robots mobiles (en particulier pour les drones quadri-rotors).Le troisième chapitre se concentre sur certains des défis algorithmiques rencontrés lors de l'élaboration de techniques de coordination multi-robots.Le quatrième chapitre introduit une nouvelle conception mécanique pour un drone quadrirotor sur-actionné avec pour objectif de pouvoir, à terme, avoir 6 degrés de liberté sur une plateforme quadrirotor classique (mais sous-actionné).Enfin, le cinquième chapitre présente une cadre général pour la vision active permettant, en optimisant les mouvements de la caméra, l’optimisation en ligne des performances (en terme de vitesse de convergence et de précision finale) de processus d’estimation « basés vision »

Expert-in-the-Loop Multilateral Telerobotics for Haptics-Enabled Motor Function and Skills Development

Among medical robotics applications are Robotics-Assisted Mirror Rehabilitation Therapy (RAMRT) and Minimally-Invasive Surgical Training (RAMIST) that extensively rely on motor function development. Haptics-enabled expert-in-the-loop motor function development for such applications is made possible through multilateral telerobotic frameworks. While several studies have validated the benefits of haptic interaction with an expert in motor learning, contradictory results have also been reported. This emphasizes the need for further in-depth studies on the nature of human motor learning through haptic guidance and interaction. The objective of this study was to design and evaluate expert-in-the-loop multilateral telerobotic frameworks with stable and human-safe control loops that enable adaptive “hand-over-hand” haptic guidance for RAMRT and RAMIST. The first prerequisite for such frameworks is active involvement of the patient or trainee, which requires the closed-loop system to remain stable in the presence of an adaptable time-varying dominance factor. To this end, a wave-variable controller is proposed in this study for conventional trilateral teleoperation systems such that system stability is guaranteed in the presence of a time-varying dominance factor and communication delay. Similar to other wave-variable approaches, the controller is initially developed for the Velocity-force Domain (VD) based on the well-known passivity assumption on the human arm in VD. The controller can be applied straightforwardly to the Position-force Domain (PD), eliminating position-error accumulation and position drift, provided that passivity of the human arm in PD is addressed. However, the latter has been ignored in the literature. Therefore, in this study, passivity of the human arm in PD is investigated using mathematical analysis, experimentation as well as user studies involving 12 participants and 48 trials. The results, in conjunction with the proposed wave-variables, can be used to guarantee closed-loop PD stability of the supervised trilateral teleoperation system in its classical format. The classic dual-user teleoperation architecture does not, however, fully satisfy the requirements for properly imparting motor function (skills) in RAMRT (RAMIST). Consequently, the next part of this study focuses on designing novel supervised trilateral frameworks for providing motor learning in RAMRT and RAMIST, each customized according to the requirements of the application. The framework proposed for RAMRT includes the following features: a) therapist-in-the-loop mirror therapy; b) haptic feedback to the therapist from the patient side; c) assist-as-needed therapy realized through an adaptive Guidance Virtual Fixture (GVF); and d) real-time task-independent and patient-specific motor-function assessment. Closed-loop stability of the proposed framework is investigated using a combination of the Circle Criterion and the Small-Gain Theorem. The stability analysis addresses the instabilities caused by: a) communication delays between the therapist and the patient, facilitating haptics-enabled tele- or in-home rehabilitation; and b) the integration of the time-varying nonlinear GVF element into the delayed system. The platform is experimentally evaluated on a trilateral rehabilitation setup consisting of two Quanser rehabilitation robots and one Quanser HD2 robot. The framework proposed for RAMIST includes the following features: a) haptics-enabled expert-in-the-loop surgical training; b) adaptive expertise-oriented training, realized through a Fuzzy Interface System, which actively engages the trainees while providing them with appropriate skills-oriented levels of training; and c) task-independent skills assessment. Closed-loop stability of the architecture is analyzed using the Circle Criterion in the presence and absence of haptic feedback of tool-tissue interactions. In addition to the time-varying elements of the system, the stability analysis approach also addresses communication delays, facilitating tele-surgical training. The platform is implemented on a dual-console surgical setup consisting of the classic da Vinci surgical system (Intuitive Surgical, Inc., Sunnyvale, CA), integrated with the da Vinci Research Kit (dVRK) motor controllers, and the dV-Trainer master console (Mimic Technology Inc., Seattle, WA). In order to save on the expert\u27s (therapist\u27s) time, dual-console architectures can also be expanded to accommodate simultaneous training (rehabilitation) for multiple trainees (patients). As the first step in doing this, the last part of this thesis focuses on the development of a multi-master/single-slave telerobotic framework, along with controller design and closed-loop stability analysis in the presence of communication delays. Various parts of this study are supported with a number of experimental implementations and evaluations. The outcomes of this research include multilateral telerobotic testbeds for further studies on the nature of human motor learning and retention through haptic guidance and interaction. They also enable investigation of the impact of communication time delays on supervised haptics-enabled motor function improvement through tele-rehabilitation and mentoring

Neural models of inter-cortical networks in the primate visual system for navigation, attention, path perception, and static and kinetic figure-ground perception

Vision provides the primary means by which many animals distinguish foreground objects from their background and coordinate locomotion through complex environments. The present thesis focuses on mechanisms within the visual system that afford figure-ground segregation and self-motion perception. These processes are modeled as emergent outcomes of dynamical interactions among neural populations in several brain areas. This dissertation specifies and simulates how border-ownership signals emerge in cortex, and how the medial superior temporal area (MSTd) represents path of travel and heading, in the presence of independently moving objects (IMOs). Neurons in visual cortex that signal border-ownership, the perception that a border belongs to a figure and not its background, have been identified but the underlying mechanisms have been unclear. A model is presented that demonstrates that inter-areal interactions across model visual areas V1-V2-V4 afford border-ownership signals similar to those reported in electrophysiology for visual displays containing figures defined by luminance contrast. Competition between model neurons with different receptive field sizes is crucial for reconciling the occlusion of one object by another. The model is extended to determine border-ownership when object borders are kinetically-defined, and to detect the location and size of shapes, despite the curvature of their boundary contours. Navigation in the real world requires humans to travel along curved paths. Many perceptual models have been proposed that focus on heading, which specifies the direction of travel along straight paths, but not on path curvature. In primates, MSTd has been implicated in heading perception. A model of V1, medial temporal area (MT), and MSTd is developed herein that demonstrates how MSTd neurons can simultaneously encode path curvature and heading. Human judgments of heading are accurate in rigid environments, but are biased in the presence of IMOs. The model presented here explains the bias through recurrent connectivity in MSTd and avoids the use of differential motion detectors which, although used in existing models to discount the motion of an IMO relative to its background, is not biologically plausible. Reported modulation of the MSTd population due to attention is explained through competitive dynamics between subpopulations responding to bottom-up and top- down signals