Bilevel shared control for teleoperators

A shared system is disclosed for robot control including integration of the human and autonomous input modalities for an improved control. Autonomously planned motion trajectories are modified by a teleoperator to track unmodelled target motions, while nominal teleoperator motions are modified through compliance to accommodate geometric errors autonomously in the latter. A hierarchical shared system intelligently shares control over a remote robot between the autonomous and teleoperative portions of an overall control system. Architecture is hierarchical, and consists of two levels. The top level represents the task level, while the bottom, the execution level. In space applications, the performance of pure teleoperation systems depend significantly on the communication time delays between the local and the remote sites. Selection/mixing matrices are provided with entries which reflect how each input's signals modality is weighted. The shared control minimizes the detrimental effects caused by these time delays between earth and space

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

Disturbance observer based bilateral control systems

Bilateral teleoperation is becoming one of the far reaching application areas of robotics science. Enabling a human operator the ability to reach and manipulate a remote location will be possible with the various applications of bilateral control. In that sense, ideal bilateral control allows extension of a person's sensing to a remote environment by a master slave structure. So, the coupled goals of bilateral control is to enforce the slave system track the motion generated on the master system and to reflect the forces from the slave system. This thesis investigates the current state of the art in bilateral teleoperation. For that purpose, design and analysis of bilateral control is made based on the use of disturbance observers. First, a known control structure is investigated in the context of acceleration control. Following this, a case study is made to show a different application of bilateral control, namely grasping force control. Performance improvement in bilateral control is also studied and correspondingly, a novel functional observer is proposed for better estimation of velocity, acceleration and disturbance. In the second half of the thesis, bilateral control with time delay is realized. Design is made via separating the position and force into two different loops. For position control under time delay, a previously proposed control scheme is used in which use of communication disturbance observer with convergence terms was discussed. Observation made about the divergence from the master reference under contact motion is analyzed and a model following control structure is proposed to eliminate the remaining disturbance from the slave plant. For force control under time delay, first the response of a local controller is analyzed. In order to improve the system transparency, a new method is proposed in which environment stiffness was used for force control loop rather than the delayed slave force. In this structure, estimation of environment stiffness was made via an indirect adaptive control scheme. The analyzed structures were also tested experimentally under a master slave system consisting of 1 DOF linear motors. Experiments show the validity of the contributions made for bilateral control with and without time delay

Novel Haptic Cueing for UAV Tele-Operation.

The use of Unmanned Aerial Vehicles (UAVs) is continuously increasing both for military and civilian operations. The degree of automation inside an UAV has reached the capability of high levels of autonomy, increasing but human participation/action is still a requirement to ensure an ultimate level of safety for the mission. Direct remote piloting is often required for a board range of situations; this is true especially for larger UAVs, where a fault might be dangerous for the platform but even for the other entities of its environment (people, building etc.). Unfortunately the physical separation between pilot/operator and the UAV reduces greatly the situational awareness; this has a negative impact on system performance in the presence of remote and unforeseen environmental constraints and disturbances. This is why this thesis is dedicated to the study of means to increase the level of situational awareness of the UAV operator. The sense of telepresence is very important in teleoperation, and it appears reasonable, and it has already been shown in the literature, that extending the visual feedback with force feedback is able to complement the visual information (when missing or limited). An artificially recreated sense of touch (haptic) may allow the operator to better perceive information from the remote aircraft state, the environment and its constraints, hopefully preventing dangerous situations. This thesis introdues first a novel classification for haptic aid systems in two large classes: Direct Haptic Aid (DHA) and Indirect Haptic Aid (IHA), then, after showing that almost all existing aid concepts belong to the first class, focuses on IHA and tries to show that classical applications (that used a DHA approach) can be revised in a IHA fashion. The novel IHA systems produce different sensations, which in most cases may appear as exactly "opposite in sign" from the corresponding DHA; these sensations can provide valuable cues for the pilot, both in terms of improvement of performance and "level of appreciation". Furthermore, it will be shown that the novel cueing algorithms, which were designed just to appear "natural" to the operator, and not to directly help the pilot in his task (as in the DHA cases), can outperform the corresponding DHA systems. Three case studies were selected: obstacle avoidance, wind gust rejection, and a combination of the two. For all the cases, DHA and IHA systems were designed and compared against baseline performance with no haptic aid. Test results show that a net improvement in terms of performance is provided by employing the IHA cuse instead of both the DHA cues or the visual cues only. Both professional pilots and naïve subjects were used in some of the experiments. The perceived feelings transmitted by the haptic cues, strongly depend by the type of the experiment and the quality of the participants: the professional pilots, for instance, retained the DHA the most helpful force while they preferred IHA because they found it more natural and because they felt a better control authority on the aircraft; different results were obtained with naive participants. In the end, this thesis aim is to show that the IHA philosophy is a valid and promising alternative to the other commonly used, and published in the scientific literature, approaches which fall in the DHA category. Finally the haptic cueing for the obstacle avoidance task was tested in the presence of time delay in the communication link, as in a classical bilateral teleoperation scheme. The Master was provide with an admittance controller and an observer for force exerted by the human on the stick was developed. Experiments have shown that the proposed system is capable of standing substantial communication delays

Proceedings of the NASA Conference on Space Telerobotics, volume 4

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotic technology to the space systems planned for the 1990's and beyond. Volume 4 contains papers related to the following subject areas: manipulator control; telemanipulation; flight experiments (systems and simulators); sensor-based planning; robot kinematics, dynamics, and control; robot task planning and assembly; and research activities at the NASA Langley Research Center

Performance and stability of telemanipulators using bilateral impedance control

A new method of control for telemanipulators called bilateral impedance control is investigated. This new method differs from previous approaches in that interaction forces are used as the communication signals between the master and slave robots. The new control architecture has several advantages: (1) It allows the master robot and the slave robot to be stabilized independently without becoming involved in the overall system dynamics; (2) It permits the system designers to arbitrarily specify desired performance characteristics such as the force and position ratios between the master and slave; (3) The impedance at both ends of the telerobotic system can be modulated to suit the requirements of the task. The main goals of the research are to characterize the performance and stability of the new control architecture. The dynamics of the telerobotic system are described by a bond graph model that illustrates how energy is transformed, stored, and dissipated. Performance can be completely described by a set of three independent parameters. These parameters are fundamentally related to the structure of the H matrix that regulates the communication of force signals within the system. Stability is analyzed with two mathematical techniques: the Small Gain Theorem and the Multivariable Nyquist Criterion. The theoretical predictions for performance and stability are experimentally verified by implementing the new control architecture on a multidegree of freedom telemanipulator

Proceedings of the NASA Conference on Space Telerobotics, volume 5

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotics technology to the space systems planned for the 1990's and beyond. Volume 5 contains papers related to the following subject areas: robot arm modeling and control, special topics in telerobotics, telerobotic space operations, manipulator control, flight experiment concepts, manipulator coordination, issues in artificial intelligence systems, and research activities at the Johnson Space Center

Haptic teleoperation of the youbot with friction compensation for the base

Haptic devices are bringing new possibilities for teleoperation by increasing the level of awareness that the operator can have over the slave. In other words, they create a stronger link between them. Because it is not enough to have a view of the task at hand, it is better to feel what is really happening at the other side. The main goal of the project is to provide the KUKA youBot with an Omega 6 haptic interface. The operator can feel the movement limitations that the arm’s tooltip may be experiencing, resulting in a better driving practice. But with these new capabilities other concerns arise, like the choice of an appropriate control algorithm, the correct coupling of workspaces or the design of a suitable data handling scheme. However, the current setup has not yet been submitted to a proper system validation and so there is still much work to do in order to increase its overall performance. Since friction can have a major role in the control scheme of the system, the latter should be provided with friction compensation. To achieve this, a study of the youBot wheels motor block friction has been carried out. These results are then also incorporated in the robot simulation. Moreover, when identifying this kind of behaviours some important decisions have to be made in order to get the best results from the time invested. Among those are the selection of a friction model, the system identification experiments and the validation of results. In conclusion, it has been proven that the implementation of a haptic interface for the youBot is not only feasible but that it delivers a greater overall teleoperation experience. Also, although the results of this project are an initial version of the system, the friction compensation for the base motor blocks is already working with acceptable performance. ________________________________________________________________________________________________________________Los dispositivos hápticos están trayendo nuevas posibilidades a la teleoperación, aumentando el nivel de consciencia que el operador puede tener sobre la máquina que dirige. En otras palabras, crean un vínculo más fuerte entre ambos. Y es que a veces no es suficiente visualizar la tarea que se esta realizando, es mejor notar lo que realmente está pasando en el otro lado. El objetivo principal del proyecto es proporcionar al robot youBot de KUKA una interfaz con el dispositivo háptico Omega6. El operador puede notar las limitaciones en los movimientos que la herramienta del brazo robot pueda estar experimentando, resultando así en una mejor experiencia de conducción. Pero con estas nuevas capacidades aparecen otras preocupaciones, como elegir un algoritmo de control apropiado, la correcta unión de los espacios de trabajo o el diseño de un esquema de manejo de datos adecuado. Sin embargo, la instalación actual aún no ha sido sometida a una evaluación de sistema apropiada y por lo tanto todavía hay mucho trabajo por hacer para incrementar el rendimiento general. Ya que la fricción puede tener un rol importante en el esquema de control del sistema, este debería ser provisto con compensación de fricción. Para lograr esto se ha llevado a cabo un estudio de los bloques motor de las ruedas del youBot. Estos resultados se han incorporado también a la simulación del robot. Por otra parte, cuando se identifican esta clase de comportamientos se han de tomar decisiones importantes para obtener los mejores resultados del tiempo empleado. Entre estas están la selección de un modelo de fricción adecuado, los experimentos para identificar el sistema y la validación de los resultados. En conclusión, se ha probado que la implementación del youBot con una interfaz háptica no es solo posible sino que mejora la experiencia general de teleoperación. Además, aunque los resultados del proyecto son una versión inicial del sistema, la compensación de la fricción para los bloques motor de la base ya está funcionando con un rendimiento aceptable.Ingeniería Industria