Rafael E. Vásquez

Mechanical/Naval Design of an Underwater Remotely Operated Vehicle (ROV) for Surveillance and Inspection of Port Facilities

This paper presents the mechanical/naval design process of an underwater remotely operated vehicle (ROV), required to obtain reliable visual information, used for surveillance and maintenance of ship shells and underwater structures of Colombian port facilities. The design was divided into four main subsystems: mechanical/naval, hardware, software and guidance, navigation and control. The most relevant design constraints were evaluated considering environmental conditions, dimensional restrictions, hydrostatics, hydrodynamics, degrees of freedom and the availability of instrumentation and control hardware. The mechanical/naval design was performed through an iterative process by using computational tools, including Computer Aided Design CAD, Computer Aided Engineering CAE, Computational Fluid Dynamics CFD and a high level programming environment. The obtained design ensures that the reliable operation of the robot will be achieved by using a consistent construction process. The new ROV constitutes an innovative product in Colombia, and it will be used for surveillance and oceanographic research tasks.© 2007 ASME

Development of an Underwater Remotely Operated Vehicle (ROV) for Surveillance and Inspection of Port Facilities

This work addresses the development of an underwater remotely operated vehicle (ROV), required to obtain reliable visual information, used for surveillance and maintenance of ship shells and underwater structures of Colombian port facilities and oceanographic research. The most relevant design constraints were evaluated considering environmental conditions, dimensional restrictions, hydrostatics, hydrodynamics, degrees of freedom and the availability of instrumentation and control hardware. The mechanical/naval design was performed through an iterative process by using computational tools CAD/CAE/CFD. The hardware architecture was divided in three layers: instrumentation, communications and control. The software was developed using ANSI C with Embedded Linux operating system. The guidance and navigation system used the Kalman filter to estimate the state of the vehicle. The vehicle can operate in manual and semi-automatic modes. In the semi-automatic, the position of a joystick is converted into the velocity set-points that are integrated to get the yaw and depth commands for the PID controllers. The rigorous design and a consistent construction processes allowed the development of a robust and reliable robotic system that constitutes an innovative product in Colombia.Copyright

Analysis of a Planar Tensegrity Mechanism for Ocean Wave Energy Harvesting

Tensegrity systems have been used in several disciplines such as architecture, biology, aerospace, mechanics, and robotics during the last 50 years. However, just a few references in literature have stated the possibility of using such systems in ocean or energy-related applications. This work addresses the kinematic and dynamic analyses of a planar tensegrity mechanism for ocean wave energy harvesting. Ocean wave mechanics and the most important concepts related to fluid–structure interaction are presented. Then, a planar 3 degrees of freedom (3-dof) tensegrity mechanism, based on a morphology defined by Kenneth Snelson in 1960 which is known as “X-frame,” is proposed as connecting linkage to transmit wave-generated forces. A geometric approach is used to solve the forward and reverse displacement problems. The theory of screws is used to perform the forward and reverse velocity analyses of the device. The Lagrangian approach is used to deduce the equations of motion considering the interaction between the mechanism and ocean waves. The tensegrity-based mechanism is analyzed using a linear model of ocean waves and its energy harvesting capabilities are compared to a purely heaving device. Results show that the proposed tensegrity configuration allows to harvest 10% more energy than the traditional heaving mechanism used in several wave energy harvesting applications. Therefore, tensegrity systems could play an important role in the expansion of clean energy technologies that help the worlds sustainable development.

Development of a Low-Level Control System for the ROV Visor3

This paper addresses the development of the simulation of the low-level control system for the underwater remotely operated vehicle Visor3. The 6-DOF mathematical model of Visor3 is presented using two coordinated systems: Earth-fixed and body-fixed frames. The navigation, guidance, and control (NGC) structure is divided into three layers: the high level or the mission planner; the mid-level or the path planner; and the low level formed by the navigation and control systems. The nonlinear model-based observer is developed using the extended Kalman filter (EKF) which uses the linearization of the model to estimate the current state. The behavior of the observer is verified through simulations using Simulink®. An experiment was conducted with a trajectory that describes changes in the and and yaw components. To accomplish this task, two algorithms are compared: a multiloop PID and PID with gravity compensation. These controllers and the nonlinear observer are tested using the 6-DOF mathematical model of Visor3. The control and navigation systems are a fundamental part of the low-level control system that will allow Visor3’s operators to take advantage of more advanced vehicle’s capabilities during inspection tasks of port facilities, hydroelectric dams, and oceanographic research.

Development of a Laboratory Equipment for Dynamic Systems and Process Control Education

This paper addresses the development of an equipment to teach control engineering fundamentals. The design requirements were determined by users that perform academic, research and industrial training tasks in the area of dynamic systems and process control. Such requirements include: industrial instrumentation; measurement of controlled and manipulated variables, and disturbances; process reconfigurability; different control technologies; several control strategies; appropriate materials for visualization; and compact shape to optimize lab space. The selected process is a tank system that allows one to choose among several dynamic behaviors: first, second, and third order, linear and nonlinear behavior, and dead time; the mathematical model that represents the dynamics of the system is presented. A traditional 3-stage design methodology that includes conceptual, basic and detailed design was followed. The developed equipment allows the user to select from three different technological alternatives to control the system: a PLC, an industrial controller, and a computer. With such flexibility, several control strategies can be implemented: feedback, feedforward, PID, LQG, nonlinear control (gain scheduling, sliding mode, etc.), fuzzy logic, neural networks, dynamic matrix control, etc. The developed system is being used to teach undergrad courses, grad courses, and industrial training. Additionally, the equipment is useful in research projects where grad students and researches can implement and test several advanced control techniques.Copyright

Kinematic Analysis of a Planar Tensegrity Mechanism for Wave Energy Harvesting

Tensegrity systems have been used in several disciplines such as architecture, biology, aerospace, mechanics and robotics during the last fifty years. However, just a few references in literature have stated the possibility of using them in ocean or energy-related applications. This work addresses the kinematic analysis of a planar 3–dof tensegrity mechanism for ocean wave energy harvesting. A planar tensegrity mechanism is proposed based on the “X-frame” morphology developed by Kenneth Snelson in 1960s. A geometric approach is used to solve the forward and reverse displacement problems. The theory of screws is used to perform the forward and reverse velocity analyses of the device. The result of shows that tensegrity systems could play an important roll in the expansion of clean energy technologies that help the world’s sustainable development.

Estrategias para Compensar no Linealidades Generadas por Válvulas en Lazos de Control de Flujo

In this work, different strategies to compensate nonlinearities generated by valves in flow control loops were compared. The identification for an incompressible flow process was made through a plant test and a computer control system was developed. In this system a PI linear controller and four different compen-sation strategies were implemented using LabVIEW™. The comparison was made using the integral of the absolute value of the error, settling time and overshoot as performance indexes. The compared strategies allowed improving the performance of the linear controller in the actuator saturation zone. In conclusion, using these algorithms can be considered to replace elements as self-tuning controllers or nonlinear positioners that raise the inversion and maintenance costs of the plant.

On the use of time-domain simulation in the design of Remotely Operated Submergible Vehicles

Designing a Remotely Operated Vehicle (ROV) is a complicated task in which the design team deals with a considerable amount of uncertainty before the device is able to be tested at full scale. A way to cope with such uncertainty is to use simulation software to evaluate design concepts along the different levels of abstraction of the process. In this work, the use of aNySIM, the Maritime Research Institute Netherlands (MARIN) multibody time-domain simulation tool, as a part of the design process of an ROV is addressed. The simulation software is able to solve the equations of motion of the vehicle based on rigid body dynamics, including features such as hydrodynamics, hydrostatics, thrusters, thrust allocation, and PID control. Different simulation scenarios are proposed to evaluate different concept solutions to the design, including thruster parameters and distribution. The results are further used to select the concept solutions to be implemented in the final design.

A Methodology for DP Capability Studies on Remotely Operated Vehicles

Dynamic Positioning (DP) capability studies are used to assess if a vessel has sufficient thrust capacity to withstand environmental loads while keeping its position and orientation at a specified set-point or path. These studies are usually performed on ships and other DP-controlled surface vessels; consequently, standards and procedures for these are widely known. In this work, a methodology for conducting a DP capability study for Remotely Operated Vehicles (ROV) is presented. Due to the nature of ROV operations, a DP capability study should include different features that are not common to surface vessels. In this case, an ROV connected to a surface vessel through a tether is considered. During operation, the tether is subject to varying current loads that are accumulated along the water column and transferred to the vehicle. Therefore, the ROVs thrusters must be able to withstand, in addition to its own drag, three-dimensional loads due to three-dimensional currents and umbilical-related loads. To illustrate the methodology, two case studies are considered: the DP capability of an ROV that has to operate in the Colombian Caribbean and an existing ROV operating in the North Sea.Copyright

Development and implementation of a low-level control system for the underwater remotely operated vehicle Visor3

This paper addresses the development and implementation of a low level control system for the underwater vehicle Visor3, developed by the Universidad Pontificia Bolivariana, located at Medellín, Colombia. Visor3 is an observation class ROV that was developed for surveillance and inspection of port facilities and underwater structures and has been used as a test platform for the development of robotic technology for underwater exploration of Colombian seas. Both, the control and navigation algorithms were implemented in the on-board processor (BeagleBone embedded computer). This processor is running an Ångström operating system which is a Linux distribution used in embedded devices with built-in components. The control and navigation algorithms were tested in a hardware in the loop (HIL) environment using a 6-DOF mathematical model of Visor3 before the real test. Results from the HIL simulation and experimental test are compared. Results show that the HIL is powerful tool for the NGC development of the ROV.