In this paper we present a solution to the problem of estimating the position and orientation of a moving underwater object using acoustic range measurements relative to moving surface objects that have access to a gl...
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In this paper we present a solution to the problem of estimating the position and orientation of a moving underwater object using acoustic range measurements relative to moving surface objects that have access to a global navigation system. We start with the description of a standard GPS Intelligent Buoy system (GIB) that employs an Extended Kalman Filter (EKF); then we adapt this principle for the concrete task of tracking a human diver utilizing moving autonomous surface crafts. To this effect, we will introduce an advanced measurement system that improves significantly the estimation quality especially in the described scenario. The paper concludes with a short description of the first sea trials of the new developed system.
This paper addresses the problem of steering a quadrotor vehicle along a prescribed trajectory. The problem is formulated so as to enforce bounds on the thrust actuation and present robustness against possible disturb...
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ISBN:
(数字)9781457710964
ISBN:
(纸本)9781457710957
This paper addresses the problem of steering a quadrotor vehicle along a prescribed trajectory. The problem is formulated so as to enforce bounds on the thrust actuation and present robustness against possible disturbances resulting from errors in the estimation of the aircraft state. The proposed solution consists of a nonlinear state feedback controller for thrust and torque actuation that i) guarantees asymptotic stability of the closed-loop system in the presence of exponentially decaying observer errors, ii) ensures global regulation of the trajectory tracking errors, and iii) defines the thrust actuation as a saturated function of the position and linear velocity errors. Simulation results are presented to assess the performance and robustness of the proposed controller.
This paper proposes a controller which stabilizes a fixed-wing Unmanned Air Vehicle (UAV) in hovered flight. A six degree-of-freedom dynamic model is developed for an underactuated model-scale aircraft and a simpler t...
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ISBN:
(纸本)9781457710957
This paper proposes a controller which stabilizes a fixed-wing Unmanned Air Vehicle (UAV) in hovered flight. A six degree-of-freedom dynamic model is developed for an underactuated model-scale aircraft and a simpler three degree-of-freedom model is derived for controller design purposes. A novel nonlinear controller which renders the hovering position of the simplified system dynamics almost globally exponentially stable is proposed. Lateral stabilization is achieved by means of classic linear optimal control techniques. The nonlinear controller is designed so as to provide unidirectional thrust. Moreover, the closed-loop system is Input-to-State Stable (ISS) in the presence of unknown disturbances. Realistic simulation results demonstrate the controller's effectiveness and robustness when dealing with the problem at hand.
Using Monte-Carlo simulations and experimental model tests, the performance of three controllers designed for dynamic positioning (DP) of marine vessels and offshore rigs subjected to the influence of sea waves, curre...
Using Monte-Carlo simulations and experimental model tests, the performance of three controllers designed for dynamic positioning (DP) of marine vessels and offshore rigs subjected to the influence of sea waves, currents, and wind loads is compared for different sea conditions: calm, moderate, high, and extreme seas. The first controller is a nonlinear multivariable PID with a passive observer. The second controller is of the Linear Quadratic Gaussian (LQG) type and the third controller builds on ℋ ∞ control techniques using the mixed-μ synthesis methodology. We further examine the performance of wave filtering of the controllers operating in different sea conditions. The Monte-Carlo simulations highlight the strength of each method as well as its shortcomings and drawbacks.
Research on wind turbine Operations & Maintenance (O&M) procedures is critical to the expansion of Wind Energy Conversion systems (WEC). In order to reduce O&M costs and increase the lifespan of the turbin...
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ISBN:
(纸本)9781457710957
Research on wind turbine Operations & Maintenance (O&M) procedures is critical to the expansion of Wind Energy Conversion systems (WEC). In order to reduce O&M costs and increase the lifespan of the turbine, we study the application of Set-Valued Observers (SVO) to the problem of Fault Detection and Isolation (FDI) of wind turbines, by taking advantage of the recent advances in SVO theory for model invalidation. A simple wind turbine model is presented along with possible faulty scenarios. The SVO algorithm is built upon these dynamics, taking into account process disturbances, model uncertainty, and measurement noise. The FDI algorithm is assessed within a publicly available benchmark model, using Monte-Carlo simulation runs.
This paper describes a procedure to design robust controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads using ℋ ∞ and mixed-μ technique...
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This paper describes a procedure to design robust controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads using ℋ ∞ and mixed-μ techniques. To this effect, practical assumptions are exploited in order to obtain a linear design model with parametric uncertainties describing the dynamics of the vessel. Appropriate frequency weighting functions are selected to capture the required performance specifications at the controller design phase. The proposed model and weighting functions are then used to design robust controllers. The problem of wave filtering is also addressed during the process of modeling and controller design. The key contribution of the paper is twofold: i) it affords system designers a new method to efficiently obtain linearized design models that fit naturally in the framework of ℋ ∞ control theory, and ii) it describes, in a systematic manner, the different steps involved in the controller design process. Part II in a companion paper contains the details of simulations and results of experimental model tests in a towing tank equipped with a hydraulic wave maker.
This paper addresses the problem of Fault Detection and Isolation (FDI) for navigation systems equipped with sensors providing inertial measurements and vector observations. Two strategies are proposed. The first one ...
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This paper addresses the problem of Fault Detection and Isolation (FDI) for navigation systems equipped with sensors providing inertial measurements and vector observations. Two strategies are proposed. The first one takes advantage of existing hardware redundancy, providing sufficient conditions for the isolation of faults. The second approach exploits the analytical redundancy between the angular velocity measurements and the vector observations, by resorting to Set-Valued Observers (SVOs). The behavior of both strategies are illustrated in simulation.
This paper describes a procedure to design multiple model adaptive controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads. To this effect,...
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This paper describes a procedure to design multiple model adaptive controllers for Dynamic Positioning (DP) of ships and offshore rigs subjected to the influence of sea waves, currents, and wind loads. To this effect, a linear design model is obtained, based on practical assumptions, describing the dynamics of the vessel. Four Linear Quadratic Gaussian (LQG) DP controllers (with the same structure) are designed, covering the different sea conditions from calm to extreme seas. Tools from multiple model adaptive control (MMAC) theory are used to exploit the information provided by the different observers (models) in order to select the appropriate controller. Numerical simulations carried out using a high fidelity nonlinear DP simulator illustrate the efficiency of the MMAC techniques proposed. To bridge the gap between theory and practice, the results of the simulations were experimentally verified by model testing with a DP operated ship, the Cybership III, under different simulated sea conditions in a towing tank equipped with a hydraulic wave maker.
This paper addresses the control of linear time-invariant plants in the presence of unknown disturbances when the plant's output is only measured at sampling instants determined by a self-triggering strategy. In a...
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ISBN:
(纸本)9781457710957
This paper addresses the control of linear time-invariant plants in the presence of unknown disturbances when the plant's output is only measured at sampling instants determined by a self-triggering strategy. In a self-triggered scenario, the controller is allowed to choose when the next sampling time should occur and does so based on available measurements and on a priori knowledge about the plant. The proposed solution is a cascade interconnection of a discrete time observer and a self-triggered controller designed for state feedback. We focus our attention on discrete-time observers that are input-to-state stable (ISS) with respect to disturbances for all possible sequences of sampling times. Self-triggered control strategies presented in the literature are known to be ISS with respect to observation errors and exogenous disturbances. Due to the cascade structure of the closed-loop system, we conclude that the closed-loop is rendered ISS with respect to all bounded exogenous disturbances.
This paper addresses the problem of maintaining an autonomous robotic vehicle in a moving triangular formation by regulating its position with respect to two leader vehicles. The robotic vehicle has no a priori knowle...
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ISBN:
(纸本)9783902823199
This paper addresses the problem of maintaining an autonomous robotic vehicle in a moving triangular formation by regulating its position with respect to two leader vehicles. The robotic vehicle has no a priori knowledge of the path described by the leaders and its goal is to follow them by constantly regulating the inter-vehicle distances to a desired fixed value, using range-only measurements. To solve this station keeping problem, we propose a control strategy that estimates the formation speed and heading from the ranges obtained to the two leading vehicles, and uses simple feedback laws for speed and heading commands to drive suitably defined common and differential errors to zero. For straight-line motion, we provide guaranteed conditions under which the proposed control strategy achieves local convergence of the distance errors to zero. We also indicate how our design procedure can be extended to full dynamic models of marine robotic vehicles equipped with inner loops for yaw and speed control. Simulation results using realistic models are described and discussed.
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