Development of a Hybrid Simulator for Underwater Vehicles with Manipulators

This article describes a hybrid simulation approach meant to facilitate the realization of a simulator for underwater vehicles with one or more manipulators capable of simulating the interaction of the vehicle with objects and structures of the environment. The hybrid simulation approach is first described and motivated analytically, then an analysis of simulation accuracy is proposed, where, in particular, the implications of added mass simulation are discussed. Then, a possible implementation of the proposed architecture is shown, where a robotic simulator of articulated bodies, capable of stable and accurate simulation of contact forces, although unfit to simulate any serious hydrodynamic model, is tightly interfaced with a general purpose dynamic systems simulator that is used to simulate the hydrodynamic forces, the vehicle guidance, navigation, and control system, and also a man-machine interface. Software details and the technicalities needed to interface the two simulators are also briefly presented. Finally, the results of the simulation of three operational scenarios are proposed as qualitative assessment of the simulator capabilities

DYNAMIC MODE DECOMPOSITION APPROACH FOR ESTIMATING THE SHAPE OF A CABLE

This study investigates the dynamic behavior of a flexible cable with heterogeneous stiffness using a data-driven approach. The study aims to develop accurate models describing intricate structures with rigid or flexible components. To achieve this, reflective markers were attached to the cable at equal spacing, and the motion was manually excited and captured using an 8-camera setup and OptiTrack\u27s Motive software. The cable displacement data at the marker locations were used as initial conditions for various Dynamic Mode Decomposition (DMD) models. The performance of the data- driven cable model is compared against the performance of the DMD modeling approach, fitting the dynamics of single- and multi-degree of freedom systems with added white noise. In this work, authors have considered using time delays and Wavelets-based DMD. The study found that the Wavelet-based DMD (WDMD) model was the most accurate method for reconstructing the response of the cable in the test cases. The researchers suggest that this data-driven approach can be applied to predict the dynamic behavior of non-linear systems, with potential applications in civil engineering, aerospace, and robotics. Overall, this study presents a promising approach to developing accurate models of complex structures with rigid or flexible components. The findings of this study can be valuable for designing structures that can withstand dynamic loads and vibrations

Ambiente virtual para el diseño de controladores de seguimiento de trayectorias de posición de vehículo operado remotamente

This article presents a virtual environment based on co-simulation between MatLab and MSC Adams, allowing simulation, analysis, development and validation of control strategies for tracking of position trajectories of a Remotely Operated Vehicle (ROV). The simulation results in the horizontal plane show that it is possible, in an uncomplicated way, to construct a virtual environment, which allows observing realistic movements when the forces exerted on an ROV are provided. Taking advantage of the properties of co-simulation, the experiences in this work show that this simulation strategy is very suitable for analysis purposes and control design, allowing researchers and professionals the wide use of control tools available in MATLAB for this end. In this work, a robust linear quadratic regulator (LQR) with integral action has been used to evaluate the performance of the proposed virtual environment for tracking of position trajectories. To validation purposes, widely used trajectories in naval study designs were employed such as the Zig -Zag shaped and the Circular shaped trajectories. Simulation results show that the integration of both, MatLab and MSC Adams, effectively addressees the problem of evaluation of performance of control strategies in the virtual environment. The presented approach allows gaining experience about the challenges of this kind of control problems, before dealing with the complex aspects of tuning in real experimental environments, avoiding losses and cost overruns for underwater robotics projects.Este artículo presenta un ambiente virtual basado en co-simulación entre MatLab y MSC Adams, permitiendo simulación, análisis, desarrollo y validación de estrategias de control para el seguimiento de trayectorias de posición de un vehículo operado remotamente (ROV). Los resultados de simulación en el plano horizontal muestran que es posible, de forma simple, construir un ambiente virtual que permite observar movimientos realistas al ingresar las fuerzas ejercidas sobre un ROV. Sacando ventaja de las propiedades de co-simulación, las experiencias en este trabajo muestran que esta estrategia de simulación es muy adecuada para propósitos de análisis y diseño de control, permitiendo a los investigadores y profesionales el uso amplio de herramientas de control disponible en MATLAB para este fin. En este trabajo se utiliza un regulador lineal cuadrático (LQR) robusto con acción integral para evaluar el desempeño del entorno virtual propuesto en el seguimiento de una trayectoria de posición. Para la validación se utilizaron trayectorias ampliamente empleadas en diseños de estudios navales como son la de forma de Zig-Zag y la de forma Circular. Los resultados de simulación muestran que la integración de MatLab y MSC Adams permite evaluar de forma efectiva el desempeño de estrategias de control en este entorno virtual. El enfoque presentado permite ganar experiencia acerca de los desafíos de este tipo de problemas de control, antes de tratar con los aspectos complejos de sintonización en ambientes experimentales reales, evitando pérdidas y sobrecostos en los proyectos robótica submarina

Design and Modeling of a New Biomimetic Soft Robotic Jellyfish Using IPMC-Based Electroactive Polymers

Smart materials and soft robotics have been seen to be particularly well-suited for developing biomimetic devices and are active fields of research. In this study, the design and modeling of a new biomimetic soft robot is described. Initial work was made in the modeling of a biomimetic robot based on the locomotion and kinematics of jellyfish. Modifications were made to the governing equations for jellyfish locomotion that accounted for geometric differences between biology and the robotic design. In particular, the capability of the model to account for the mass and geometry of the robot design has been added for better flexibility in the model setup. A simple geometrically defined model is developed and used to show the feasibility of a proposed biomimetic robot under a prescribed geometric deformation to the robot structure. A more robust mechanics model is then developed which uses linear beam theory is coupled to an equivalent circuit model to simulate actuation of the robot with ionic polymer-metal composite (IPMC) actuators. The mechanics model of the soft robot is compared to that of the geometric model as well as biological jellyfish swimming to highlight its improved efficiency. The design models are characterized against a biological jellyfish model in terms of propulsive efficiency. Using the mechanics model, the locomotive energetics as modeled in literature on biological jellyfish are explored. Locomotive efficiency and cost as a function of swimming cycles are examined for various swimming modes developed, followed by an analysis of the initial transient and steady-state swimming velocities. Applications for fluid pumping or thrust vectoring utilizing the same basic robot design are also proposed. The new design shows a clear advantage over its purely biological counterpart for a soft-robot, with the newly proposed biomimetic swimming mode offering enhanced swimming efficiency and steady-state velocities for a given size and volume exchange

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

Ambiente de simulação para o sistema de exploração robótica subaquática UNEXMIN

Underwater mines exploration is a valued, complex, expensive and time-consuming task. The unstable nature of the underwater environment with lack of visibility and the existence of obstructions create the need for complex navigation software which requires numerous missions and hardware/software validations. When testing and verifying control algorithms for such an operation, a simulation environment can be a very helpful tool. This also includes tools for the development of unmanned vehicle software, algorithm benchmarking and system preliminary validation. The objective in this thesis was to start the development of a simulation platform that can be used when developing and testing control systems for AUV operations. The simulator will include a dynamic model of an AUV in addition to complex world and sensor models such as DVL, IMU, Multibeam, Mechanical Scanning Imaging Sonar (MSIS), cameras, SLS and others. The simulated world includes water graphics, mine meshes, underwater visibility, currents, and hydrodynamics. Control of the robot in simulation is performed by keyboard or joystick over thrusters. The platform must be universal, such that users can implement their own algorithms easily and get immediate simulation results without needing to implement a complete control system. There should also be an easy transition between testing the control system on the simulated AUV and applying it to the real AUV. Robot Operating System (ROS) and Gazebo were used in the development of the platform. The platform with sensors and navigation was validated with real-world tests comparison.A exploração de minas subaquáticas ´e uma tarefa valiosa, complexa, dispendiosa e demorada. A natureza instável do ambiente subaquático, com falta de visibilidade e a existência de obstruções, cria a necessidade de software de navegação complexo, qual requer inúmeras missões e validações de hardware/software. Ao testar e verificar os algoritmos de controle para tal operação, um ambiente de simulação pode ser uma ferramenta muito útil. Isto também inclui ferramentas para o desenvolvimento de software de veículos não tripulados, benchmarking de algoritmos e validação preliminar do sistema. O objetivo desta tese foi iniciar o desenvolvimento de uma plataforma de simulação que possa ser usada no desenvolvimento e teste de sistemas de controle para operações de AUV. O simulador incluirá um modelo dinâmico de um AUV, além de modelos complexos do mundo e sensores, como DVL, IMU, Multibeam, MSIS, câmaras, SLS e outros. O mundo simulado inclui gráficos de ´agua, malhas de minas, visibilidade subaquática, correntes e hidrodinâmica. O controle do robô ´e realizado por teclado ou joystick sob as dinâmicas de propulsão. O simulador deve ser universal, de modo que os usuários possam implementar seus próprios algoritmos facilmente e obter resultados imediatos de simulação sem a necessidade de implementar um sistema de controle completo. Também deve haver uma transição fácil entre testar o sistema de controle no AUV simulado e aplicá-lo ao AUV real. ROS e Gazebo foram usados no desenvolvimento da plataforma. A plataforma com sensores e navegação foi validada com comparação de testes reais