Dictino Chaos

Virtual and remote robotic laboratory using EJS, MATLAB and LabVIEW.

This paper describes the design and implementation of a virtual and remote laboratory based on Easy Java Simulations (EJS) and LabVIEW. The main application of this laboratory is to improve the study of sensors in Mobile Robotics, dealing with the problems that arise on the real world experiments. This laboratory allows the user to work from their homes, tele-operating a real robot that takes measurements from its sensors in order to obtain a map of its environment. In addition, the application allows interacting with a robot simulation (virtual laboratory) or with a real robot (remote laboratory), with the same simple and intuitive graphical user interface in EJS. Thus, students can develop signal processing and control algorithms for the robot in simulation and then deploy them on the real robot for testing purposes. Practical examples of application of the laboratory on the inter-University Master of Systems Engineering and Automatic Control are presented.

A Mobile Robots Experimental Environment with Event-Based Wireless Communication

An experimental platform to communicate between a set of mobile robots through a wireless network has been developed. The mobile robots get their position through a camera which performs as sensor. The video images are processed in a PC and a Waspmote card sends the corresponding position to each robot using the ZigBee standard. A distributed control algorithm based on event-triggered communications has been designed and implemented to bring the robots into the desired formation. Each robot communicates to its neighbors only at event times. Furthermore, a simulation tool has been developed to design and perform experiments with the system. An example of usage is presented.

Identification of a Surface Marine Vessel Using LS-SVM

The availability of adequate system models to reproduce, as faithfully as possible, the actual behaviour of the experimental systems is of key importance. In marine systems, the changing environmental conditions and the complexity of the infrastructure needed to carry out experimental tests call for mathematical models for accurate simulations. There exist a wide number of techniques to define mathematical models from experimental data. Support Vector Machines (SVMs) have shown a great performance in pattern recognition and classification research areas having an inherent potential ability for linear and nonlinear system identification. In this paper, this ability is demonstrated through the identification of the Nomoto second-order ship model with real experimental data obtained from a zig-zag manoeuvre made by a scale ship. The mathematical model of the ship is identified using Least Squares Support Vector Machines (LS-SVMs) for regression by analysing the rudder angle, surge and sway speed, and yaw rate. The coefficients of the Nomoto model are obtained with a linear kernel function. The model obtained is validated through experimental tests that illustrate the potential of SVM for system identification.

Nonlinear Control for Trajectory Tracking of a Nonholonomic RC-Hovercraft with Discrete Inputs

This work studies the problem of trajectory tracking for an underactuated RC-hovercraft, the control of which must be done by means of discrete inputs. Thus, the aim is to control a vehicle with very simple propellers that produce only a discrete set of control commands, and with minimal information about the dynamics of the actuators. The control problem is approached as a cascade control problem, where the outer loop stabilizes the position error, and the inner loop stabilizes the orientation of the vehicle. Stability of the controller is theoretically demonstrated and the robustness of the control law against disturbances and noise is established. Simulation examples and experiments on a real setup validate the control law showing the real system to be robust against disturbances, noise, and outdated dynamics.

Semiphysical Modelling of the Nonlinear Dynamics of a Surface Craft with LS-SVM

One of the most important problems in many research fields is the development of reliable mathematical models with good predictive ability to simulate experimental systems accurately. Moreover, in some of these fields, as marine systems, these models play a key role due to the changing environmental conditions and the complexity and high cost of the infrastructure needed to carry out experimental tests. In this paper, a semiphysical modelling technique based on least-squares support vector machines (LS-SVM) is proposed to determine a nonlinear mathematical model of a surface craft. The speed and steering equations of the nonlinear model of Blanke are determined analysing the rudder angle, surge and sway speeds, and yaw rate from real experimental data measured from a zig-zag manoeuvre made by a scale ship. The predictive ability of the model is tested with different manoeuvring experimental tests to show the good performance and prediction ability of the model computed.

BENCHMARK CONTROL PROBLEMS FOR A NON-LINEAR UNDERACTUATED HOVERCRAFT: A SIMULATION LABORATORY FOR CONTROL TESTING

Abstract Hovercrafts are a type of vehicles with a structure model similar to marine vehicles. These systems are strongly non-linear so their dynamics are complex. The problems of motion control can be classified in three groups: point stabilization, trajectory tracking and path following. From a pedagogical point of view it is difficult to study the behaviour of this type of vehicles using only static graphs. In order to understand the dynamics of these vehicles it is necessary to use interactive dynamic simulations. This paper shows a simulation environment used as a laboratory to design, analyze and test controllers for the three benchmark control problems for the model of a radio control hovercraft with the possibility of implementing the designs obtained in the real system.

Identification of longitudinal and transversal dynamics of a fast ferry

Abstract An analysis of the system identification methods have been carried out and a new alternative approach is proposed in order to estimate models for heave, pitch and roll dynamics of a high speed craft. As starting point, a first approach resolves the identification subject as an optimization problem to fit the best model, and uses genetic algorithms and nonlinear least squares with constraints methods applied in the frequency domain. The second and definitive one suggests a new parameterization which facilitates obtaining high quality starting values and avoids non-quadratic functions in the cost function. At last it is shown an example in which the two approximations are applied and compared.

Combining Virtual and Remote Interactive Labs and Visual/Textual Programming: The Furuta Pendulum Experience

This paper proposes a new way of experimenting with online (virtual or remote) interactive laboratories. Experimentation possibilities can be opened by allowing students to interact with the online laboratory using a visual and textual programming language that can communicate with the laboratory application and which includes tools to define and plot graphs. The combination of interactive laboratories with a visual and textual programming language, benefits both teachers and students: the former have a wider range of possibilities when considering the assignments that can be proposed and the latter acquire a greater knowledge of the plant under study by facing a more inquiry-based approach for online experimentation. To demonstrate the usefulness and possibilities of this environment, a Furuta pendulum system has been successfully used in both its remote and its virtual version.

Design of a stabilization control system for high-speed crafts based on robust techniques. Two different approaches

This work handles the design of a stabilization control for a high-speed craft in order to improve comfort and security in maritime transport. The goal is to damp the coupled dynamics of heave, pitch and roll by using active stabilization surfaces such as flaps, T-foil and fins. The methodology used is based on the Quantitative Feedback Theory (QFT) robust technique. Two approaches depending on the degree of coupling are presented. In the first approach, controllers for the longitudinal and transversal dynamics are designed separately and afterwards the actuator coupling is considered. The second approach provides a solution in cases where the effect of the actuator coupling is large. Hence, a combination of QFT and Eigenstructure Assignment (EA) methods is used. For both methods, time-domain simulations analyses for different conditions of sea state and angles of incidence provide satisfactory results and achieve damped responses. It is shown that robust techniques based on QFT methodology result feasible and very suitable since the problem can be applied to any angle of incidence and only one controller is required for any speed or sea state. Therefore they constitute attractive alternatives in the application of a stabilization control of an advanced marine system.

Quantized-State control of a hovercraft with discrete inputs

Abstract The In this work the quantized state control QSC methodology has been applied to the tracking control problem of a Hovercraft with discrete control inputs. Firstly a continuous control law for the hovercraft with continuous inputs is designed. Then this controller is adapted to the discontinuous inputs by using a PWM strategy. Finally the QSC methodology is introduced. This paper shows that the control effort and number of computations in the controller can be reduced by the QSC strategy without loss of performance.