The Shape of Damping: Optimizing Damping Coefficients to Improve Transparency on Bilateral Telemanipulation

This thesis presents a novel optimization-based passivity control algorithm for hapticenabled bilateral teleoperation systems involving multiple degrees of freedom. In particular, in the context of energy-bounding control, the contribution focuses on the implementation of a passivity layer for an existing time-domain scheme, ensuring optimal transparency of the interaction along subsets of the environment space which are preponderant for the given task, while preserving the energy bounds required for passivity. The involved optimization problem is convex and amenable to real-time implementation. The effectiveness of the proposed design is validated via an experiment performed on a virtual teleoperated environment. The interplay between transparency and stability is a critical aspect in haptic-enabled bilateral teleoperation control. While it is important to present the user with the true impedance of the environment, destabilizing factors such as time delays, stiff environments, and a relaxed grasp on the master device may compromise the stability and safety of the system. Passivity has been exploited as one of the the main tools for providing sufficient conditions for stable teleoperation in several controller design approaches, such as the scattering algorithm, timedomain passivity control, energy bounding algorithm, and passive set position modulation. In this work it is presented an innovative energy-based approach, which builds upon existing time-domain passivity controllers, improving and extending their effectiveness and functionality. The set of damping coefficients are prioritized in each degree of freedom, the resulting transparency presents a realistic force feedback in comparison to the other directions. Thus, the prioritization takes effect using a quadratic programming algorithm to find the optimal values for the damping. Finally, the energy tanks approach on passivity control is a solution used to ensure stability in a system for robotics bilateral manipulation. The bilateral telemanipulation must maintain the principle of passivity in all moments to preserve the system\u2019s stability. This work presents a brief introduction to haptic devices as a master component on the telemanipulation chain; the end effector in the slave side is a representation of an interactive object within an environment having a force sensor as feedback signal. The whole interface is designed into a cross-platform framework named ROS, where the user interacts with the system. Experimental results are presented

Experimental Evaluation of the Projection-based Force Reflection Algorithms for Haptic Interaction with Virtual Environment

Haptic interaction with virtual environments is currently a major and growing area of research with a number of emerging applications, particularly in the field of robotics. Digital implementation of the virtual environments, however, introduces errors which may result in instability of the haptic displays. This thesis deals with experimental investigation of the Projection-Based Force Reflection Algorithms (PFRAs) for haptic interaction with virtual environments, focusing on their performance in terms of stability and transparency. Experiments were performed to compare the PFRA in terms of performance for both non-delayed and delayed haptic interactions with more conventional haptic rendering methods, such as the Virtual Coupling (VC) and Wave Variables (WV). The results demonstrated that the PFRA is more stable, guarantees higher levels of transparency, and is less sensitive to decrease in update rates

Adaptive assistance-based on decision-making models for telerobotics systems

Esta tesis propone una nueva estrategia de asistencia háptica en la interacción humano-robot. Dado que el humano es el elemento fundamental del sistema, es necesario proponer estrategias que se adapten a su comportamiento, además de garantizar un mejoramiento del desempeño en la tarea. El inconveniente surge cuando se requiere asistir al operador en mejorar el desempeño de la tarea y permitir al usuario total control de la tarea cuando sea necesario, desviándose del plan original con el objetivo de abordar situaciones imprevistas. Desde una perspectiva enfocada en el control, se debe resolver el compromiso existente entre proveer un alto nivel de asistencia para mejorar el desempeño de la tarea y un bajo nivel de asistencia para permitir al operador desviarse del plan pre-programado (original). Se propone entonces incorporar en la asistencia háptica un mecanismo de toma de decisiones usado por los humanos en tareas básicas de decisión entre dos alternativas. Este mecanismo de decisión se incorporar como el método de selección de parámetros en un controlador adaptativo de estructura fija (i.e. un controlador de impedencia/admitancia de parámetros variables). Los resultados experimentales demuestran que el modelo de toma de decisión, i.e. el modelo drift-diffusion modificado, permite asignar el nivel de autonomía de una forma que resulta intuitiva para el usuario y mejora el desempeño en la tarea. Además la estrategia de asistencia basada en modelos de toma de decisión proporciona un mecanismo de sintonizaci ón para resolver diferentes requerimientos de la tarea, lo cual es importante en entornos no estructurados. Dado el número de parámetros configurables presentes en la asistencia, la etapa experimental expone la función de cada uno de estos parámetros. Se realizó un experimento con usuarios en un entorno de teleoperación donde se evalúa estadísticamente el comportamiento de la asistencia en entornos parcialmente estructurados y se compara con la asistencia proporcionada por un experto humano, la cual puede ser considerada como la asistencia adaptativa nominal.Abstract. This thesis proposes a novel haptic assistance method for human-robot interaction. Since the human is the main element of the system, it is necessary to propose strategies that adapt the robot’s dynamics to the human behavior, while guaranteeing an improvement in task performance. The main issue arises when the assistance must chose between assisting the operator to improve task performance or allowing the user to have full authority over the task when necessary, allowing him/her to deviate from the original plan in order to handle unforeseen situations. From a control systems’ perspective, the assistance has to solve the trade-off between high assistance levels to improve task performance and low assistance level to allow the user to deviate from the preprogrammed (original) plan. The main results of this work incorporate into the haptic assistance a human-like decision-making mechanism used in two-alternative force choice tasks. Our experimental results show that the drift-diffusion, which is a decision-making model proposed in the cognitive area, allocates control authority in a way that is intuitive for the user. The the proposed assistance provides a tunable (decision-making) mechanism that is capable of fulfilling different task requirements, which is an important when dealing with unstructured environments. Given the number of configurable parameters in the assistance mechanism, the experimental procedure exposes the effects of changing them. A user study in a telerobotic scenario was performed to evaluate the behavior of the assistance in a partially structured environment; the proposed assistance is compared to the assistance provided by a human expert, which may be considered as the nominal adaptive assistance.Doctorad

Haptic data reduction through dynamic perceptual analysis and event-based communication

This research presents an adjustable and flexible framework for haptic data compression and communication that can be used in a robotic teleoperation session. The framework contains a customized event-driven transmission control protocol, several dynamically adaptive perceptual and prediction methods for haptic sample reduction, and last but not the least, an architecture for the data flow

Control of Cooperative Haptics-Enabled Teleoperation Systems with Application to Minimally Invasive Surgery

Robot-Assisted Minimally Invasive Surgical (RAMIS) systems frequently have a structure of cooperative teleoperator systems where multiple master-slave pairs are used to collaboratively execute a task. Although multiple studies indicate that haptic feedback improves the realism of tool-tissue interaction to the surgeon and leads to better performance for surgical procedures, current telesurgical systems typically do not provide force feedback, mainly because of the inherent stability issues. The research presented in this thesis is directed towards the development of control algorithms for force reflecting cooperative surgical teleoperator systems with improved stability and transparency characteristics. In the case of cooperative force reflecting teleoperation over networks, conventional passivity based approaches may have limited applicability due to potentially non-passive slave-slave interactions and irregular communication delays imposed by the network. In this thesis, an alternative small gain framework for the design of cooperative network-based force reflecting teleoperator systems is developed. Using the small gain framework, control algorithms for cooperative force-reflecting teleoperator systems are designed that guarantee stability in the presence of multiple network-induced communication constraints. Furthermore, the design conservatism typically associated with the small-gain approach is eliminated by using the Projection-Based Force Reflection (PBFR) algorithms. Stability results are established for networked cooperative teleoperator systems under different types of force reflection algorithms in the presence of irregular communication delays. The proposed control approach is consequently implemented on a dual-arm (two masters/two slaves) robotic MIS testbed. The testbed consists of two Haptic Wand devices as masters and two PA10-7C robots as the slave manipulators equipped with da Vinci laparoscopic surgical instruments. The performance of the proposed control approach is evaluated in three different cooperative surgical tasks, which are knot tightening, pegboard transfer, and object manipulation. The experimental results obtained indicate that the PBFR algorithms demonstrate statistically significant performance improvement in comparison with the conventional direct force reflection algorithms. One possible shortcoming of using PBFR algorithms is that implementation of these algorithms may lead to attenuation of the high-frequency component of the contact force which is important, in particular, for haptic perception of stiff surfaces. In this thesis, a solution to this problem is proposed which is based on the idea of separating the different frequency bands in the force reflection signal and consequently applying the projection-based principle to the low-frequency component, while reflecting the high-frequency component directly. The experimental results demonstrate that substantial improvement in transient fidelity of the force feedback is achieved using the proposed method without negative effects on the stability of the system