Robust and Safe Autonomous Navigation for Systems with Learned SE(3) Hamiltonian Dynamics

Stability and safety are critical properties for successful deployment of automatic control systems. As a motivating example, consider autonomous mobile robot navigation in a complex environment. A control design that generalizes to different operational conditions requires a model of the system dynamics, robustness to modeling errors, and satisfaction of safety \NEWZL{constraints}, such as collision avoidance. This paper develops a neural ordinary differential equation network to learn the dynamics of a Hamiltonian system from trajectory data. The learned Hamiltonian model is used to synthesize an energy-shaping passivity-based controller and analyze its \emph{robustness} to uncertainty in the learned model and its \emph{safety} with respect to constraints imposed by the environment. Given a desired reference path for the system, we extend our design using a virtual reference governor to achieve tracking control. The governor state serves as a regulation point that moves along the reference path adaptively, balancing the system energy level, model uncertainty bounds, and distance to safety violation to guarantee robustness and safety. Our Hamiltonian dynamics learning and tracking control techniques are demonstrated on \Revised{simulated hexarotor and quadrotor robots} navigating in cluttered 3D environments

Aerial Manipulation: A Literature Review

Aerial manipulation aims at combining the versatil- ity and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well

Wall-contact sliding control strategy for a 2D caged quadrotor

This paper addresses the trajectory tracking problem of a 2D caged flying robot in contact with a wall. To simplify the contact problem, the models are constructed on a vertical two-dimensional plane, and our objective is to let the quadrotor hover or move along the wall with arbitrary velocity and attitude. The control law is derived using the Lyapunov stability theory, applying backstepping techniques to achieve exponential stability under mild assumptions. To overcome the unknown friction force between robot and wall, we design estimators for the friction coefficient, which include a projection operator that provides an upper bound for the obtained estimates. Realistic simulation results are provided to validate the proposed methodology

Model-Based Control of Flying Robots for Robust Interaction under Wind Influence

Model-Based Control of Flying Robots for Robust Interaction under Wind Influence The main goal of this thesis is to bridge the gap between trajectory tracking and interaction control for flying robots in order to allow physical interaction under wind influence by making aerial robots aware of the disturbance, interaction, and faults acting on them. This is accomplished by reasoning about the external wrench (force and torque) acting on the robot, and discriminating (distinguishing) between wind, interactions, and collisions. This poses the following research questions. First, is discrimination between the external wrench components even possible in a continuous real-time fashion for control purposes? Second, given the individual wrench components, what are effective control schemes for interaction and trajectory tracking control under wind influence? Third, how can unexpected faults, such as collisions with the environment, be detected and handled efficiently and effectively? In the interest of the first question, a fourth can be posed: is it possible to obtain a measurement of the wind speed that is independent of the external wrench? In this thesis, model-based methods are applied in the pursuit of answers to these questions. This requires a good dynamics model of the robot, as well as accurately identified parameters. Therefore, a systematic parameter identification procedure for aerial robots is developed and applied. Furthermore, external wrench estimation techniques from the field of robot manipulators are extended to be suitable for aerial robots without the need of velocity measurements, which are difficult to obtain in this context. Based on the external wrench estimate, interaction control techniques (impedance and admittance control) are extended and applied to flying robots, and a thorough stability proof is provided. Similarly, the wrench estimate is applied in a geometric trajectory tracking controller to compensate external disturbances, to provide zero steady-state error under wind influence without the need of integral control action. The controllers are finally combined into a novel compensated impedance controller, to facilitate the main goal of the thesis. Collision detection is applied to flying robots, providing a low level reflex reaction that increases safety of these autonomous robots. In order to identify aerodynamic models for wind speed estimation, flight experiments in a three-dimensional wind tunnel were performed using a custom-built hexacopter. This data is used to investigate wind speed estimation using different data-driven aerodynamic models. It is shown that good performance can be obtained using relatively simple linear regression models. In this context, the propeller aerodynamic power model is used to obtain information about wind speed from available motor power measurements. Leveraging the wind tunnel data, it is shown that power can be used to obtain the wind speed. Furthermore, a novel optimization-based method that leverages the propeller aerodynamics model is developed to estimate the wind speed. Essentially, these two methods use the propellers as wind speed sensors, thereby providing an additional measurement independent of the external force. Finally, the novel topic of simultaneously discriminating between aerodynamic, interaction, and fault wrenches is opened up. This enables the implementation of novel types of controllers that are e.g. compliant to physical interaction, while compensating wind disturbances at the same time. The previously unexplored force discrimination topic has the potential to even open a new research avenue for flying robots

Towards Human-UAV Physical Interaction and Fully Actuated Aerial Vehicles

Unmanned Aerial Vehicles (UAVs) ability to reach places not accessible to humans or other robots and execute tasks makes them unique and is gaining a lot of research interest recently. Initially UAVs were used as surveying and data collection systems, but lately UAVs are also efficiently employed in aerial manipulation and interaction tasks. In recent times, UAV interaction with the environment has become a common scenario, where manipulators are mounted on top of such systems. Current applications has driven towards the direction of UAVs and humans coexisting and sharing the same workspace, leading to the emerging futuristic domain of Human-UAV physical interaction. In this dissertation, initially we addressed the delicate problem of external wrench estimation (force/torque) in aerial vehicles through a generalized-momenta based residual approach. To our advantage, this approach is executable during flight without any additional sensors. Thereafter, we proposed a novel architecture allowing humans to physically interact with a UAV through the employment of sensor-ring structure and the developed external wrench estimator. The methodologies and algorithms to distinguish forces and torques derived by physical interaction with a human from the disturbance wrenches (due to e.g., wind) are defined through an optimization problem. Furthermore, an admittance-impedance control strategy is employed to act on them differently. This new hardware/software architecture allows for the safe human-UAV physical interaction through exchange of forces. But at the same time, other limitations such as the inability to exchange torques due to the underactuation of quadrotors and the need for a robust controller become evident. In order to improve the robust performance of the UAV, we implemented an adaptive super twisting sliding mode controller that works efficiently against parameter uncertainties, unknown dynamics and external perturbations. Furthermore, we proposed and designed a novel fully actuated tilted propeller hexarotor UAV. We designed the exact feedback linearization controller and also optimized the tilt angles in order to minimize power consumption, thereby improving the flight time. This fully actuated hexarotor could reorient while hovering and perform 6DoF (Degrees of Freedom) trajectory tracking. Finally we put together the external wrench observer, interaction techniques, hardware design, software framework, the robust controller and the different methodologies into the novel development of Human-UAV physical interaction with fully actuated UAV. As this framework allows humans and UAVs to exchange forces as well as torques, we believe it will become the next generation platform for the aerial manipulation and human physical interaction with UAVs

A Control Architecture for Unmanned Aerial Vehicles Operating in Human-Robot Team for Service Robotic Tasks

In this thesis a Control architecture for an Unmanned Aerial Vehicle (UAV) is presented. The aim of the thesis is to address the problem of control a flying robot operating in human robot team at different level of abstraction. For this purpose, three different layers in the design of the architecture were considered, namely, the high level, the middle level and the low level layers. The special case of an UAV operating in service robotics tasks and in particular in Search&Rescue mission in alpine scenario is considered. Different methodologies for each layer are presented with simulated or real-world experimental validation

IDA-PBC Control of an Underactuated Underwater Vehicle

[ES] En este trabajo se presenta el diseño de un IDA-PBC (Interconnection and Damping Assignment-Passivity Based Control) para la regulación de un vehículo submarino subactuado. Se consideran seis grados de libertad y cuatro propulsores como actuadores, lo cual es un desafío para su control de movimiento. Específicamente, el IDA-PBC diseñado permite llevar el vehículo a una profundidad y orientación deseadas y constantes. Resultados de simulación sobre el modelo del vehículo submarino utilizado validan el desempeño del sistema de control propuesto.[EN] This paper presents an IDA-PBC (Interconnection and Damping Assignment-Passivity Based Control) for underactuated undewater vehicle control, which it has more degree of freedom than actuators. In this proposal, six degree of freedom and only four propels as actuators are considered, which it oers a main control challenge. Specifically, the IDA-PBC proposed drives the vehicle towards a desired deep and orientation. Simulation results on a vehicle model validate the performance of the control scheme proposed.Este trabajo fue parcialmente apoyado por el Tecnologi- ´ co Nacional de Mexico (Contratos TecNM 5939.16-P.C-P y ´ 6104.17-P), y por el Consejo Nacional de Ciencia y Tecnolog´ıa (Contrato CONACyT 166636).García, D.; Sandoval, J.; Gutiérrez–jagüey, J.; Bugarin, E. (2017). Control IDA-PBC de un Vehículo Submarino Subactuado. Revista Iberoamericana de Automática e Informática industrial. 15(1):36-45. https://doi.org/10.4995/riai.2017.8829OJS3645151Acosta, V., Ríos-Bolívar, M., 2010. Aplicación del enfoque ida-pbc en la estabilización del sistema pendubot. Revista Ciencia e Ingeniería 31 (1), 3-12.Akcakaya, H., Sumer, L., 2013. Ida-pbc design for marine vehicle. 1st IFAC Workshop on Advances in Control and Automation Theory for Transportation Applications, Istanbul, Turkey, 150-155. https://doi.org/10.3182/20130916-2-TR-4042.00014Balebona, C., Jenry, J., 2009. 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Tesis Doctoral, Universidad de Sevilla.Gómez-Estern, F., Ortega, R., Rubio, F. R., Aracil, J., 2001. Stabilization of a class of underactuated mechanical systems via total energy shaping. Proceedings of the 40th IEEE Conference on Decision and Control 2, 1137-1143. https://doi.org/10.1109/CDC.2001.981038González, J., Gomáriz, S., Batlle, C., 2015. Control difuso para el seguimiento de gui-ada del auv cormorán. Revista Iberoamericana de Automática e Informática Industrial 12, 166-176. https://doi.org/10.1016/j.riai.2015.02.003Healey, A. J., Lienard, D., 1993. Multivariable sliding mode control for autonomous diving and steering of unmanned underwater vehicles. IEEE Journal of Oceanic Engineering. 18, 327-339. https://doi.org/10.1109/JOE.1993.236372Khalil, H., 2002. Nonlinear systems. Prentice Hall.Kotyczka, P., Lohmann, B., 2009. Parametrization of ida-pbc by assignment of local linear dynamics. 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Control by interconnection and standard passivity-based control of port-hamiltonian systems. IEEE Transactions on Automatic Control 53, 2527-2542. https://doi.org/10.1109/TAC.2008.2006930Pérez, T., Donaire, A., Renton, C., Valentinis, F., 2013. Energy-based motion control of marine vehicles using interconnection and damping assignment passivity-based control - a survey. 9th IFAC Conference on Control Applications in Marine Systems, Osaka, Japan, 316-327. https://doi.org/10.3182/20130918-4-JP-3022.00072Sandoval, J., Kelly, R., 2013. Dise-o de un nuevo ida-pbc para la estabilización del sistema carro-péndulo. Congreso Internacional de Robótica y Computación, Los Cabos, Baja California Sur, México.Sandoval, J., Kelly, R., Santibá-ez, V., 2011. Interconnection and damping assignment passivity-based control of a class of underactuated mechanical systems with dynamic friction. 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Reshaping the physical properties of a quadrotor through IDA-PBC and its application to aerial physical interaction

International audienceIn this paper we propose a controller, based on an extension of Interconnection and Damping Assignment-Passivity Based Control (IDA-PBC) framework, for shaping the whole physical characteristics of a quadrotor and for obtaining a desired interactive behavior between the robot and the environment. In the control design, we shape the total energy (kinetic and potential) of the undamped original system by first excluding external effects. In this way we can assign a new dynamics to the system. Then we apply damping injection to the new system for achieving a desired damped behavior. Then we show how to connect a high-level control input to such system by taking advantage of the new desired physics. We support the theory with extensive simulations by changing the overall behavior of the UAV for different desired dynamics, and show the advantage of this method for sliding on a surface tasks, such as ceiling painting, cleaning or surface inspection