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The paper addresses methods of thrust distribution in a propulsion system for an unmanned underwater vehicle. It concen-trates on finding an optimal thrust allocation for desired values of forces and moments acting on the vehicle. Special attention is paid to the unconstrained thrust allocation. The proposed methods are developed using a configurat...
Citations
... This configuration maximizes the thruster-feasible wrench in all the directions. It is directly inspired from the configuration commonly used to control the motion of unmanned underwater vehicles in the horizontal plane [46]. ...
In this article, thrusters embedded on a cable-driven parallel robot (CDPR) platform are proposed to improve the CDPR dynamics and trajectory tracking performance. On-board thrusters with their short response time can compensate for the reduced bandwidth of the winch actuation due to winding speed limit and low cable stiffness. To compute and allocate control signals to winches and thrusters, a nonlinear model predictive controller (NMPC) is designed. A model of a CDPR with its hybrid actuation dynamics and saturation is introduced, including an alternative model of the thrust actuation that removes the need of thrust sensors and reduces the size of the NMPC optimization problem. To achieve a zero steady-state error with the NMPC, which becomes offset-free, an augmented model including additional disturbance states is proposed. The theoretical conditions to achieve offset-free control are checked. The proposed NMPC scheme is validated experimentally on a planar CDPR with three cables and four propeller-based thrusters. Results show that onboard thrusters contribute to a tracking error reduction along complex trajectories and an efficient damping of the platform vibration.
... For instance, as it is impossible to generate negative thrust for a monodirectional thruster, the controller should always generate positive control input (along with the nozzle exit direction) by automatically adjusting the mapping matrix. This aspect pertains to the thruster allocation problem (or control distribution problem), which has been extensively investigated (Garus 2004;Servidia and Peña 2005). Specifically, Cho et al. formulated a constrained optimization problem by using linear programming to determine a solution for the Spacecraft Simulator for the Autonomous Rendezvous and Docking facility (Cho et al. 2009). ...
... -Naval : [Sørdalen , 1997 ;Garus , 2004 ;Fossen et Johansen , 2006 ;Christiaan , 2009 ;Poppe et al., 2010 ;Johansen et Fossen , 2013]. ...
... La disposition des actionneurs embarqués a été inspirée par [Garus , 2004] qui traite du positionnement dynamique d'un sous-marin doté de quatre propulseurs. Chaque générateur de force est fixé sur la plateforme et fournit une force unilatérale. ...
Les robots parallèles à câbles présentent plusieurs avantages par rapport aux robots parallèles classiques. En raison de la faible masse des câbles, qui remplacent les corps rigides, la masse à déplacer par le robot est plus faible. Par conséquent, ces robots manipulateurs permettent d’atteindre des vitesses et accélérations élevées et de couvrir un espace de travail plus important. Les robots parallèles à câbles sont également plus facilement reconfigurables et moins coûteux.En contrepartie, la flexibilité des câbles dégrade les performances en termes de précision et de temps d’établissement. Il est donc nécessaire d’atténuer les vibrations induites par la faible rigidité de l’effecteur actionné par câbles.L’élasticité des câbles réduit également la bande passante des efforts qu’ils peuvent transmettre. En effet, plus les câbles sont longs ou composés d’un matériau élastique, plus la longueur de câble à enrouler pour générer une force donnée est grande. Cette bande passante réduite des enrouleurs des câbles limite les performances des robots parallèles à câbles. Elle ne permet pas de rejeter efficacement les vibrations et de suivre des trajectoires dynamiques et rapides par l’action seule des enrouleurs des câbles.Dans cette thèse, on propose d’embarquer sur la plateforme différents types d’actionneurs additionnels pour améliorer la dynamique du robot. Ces actionneurs sont dotés d’une bande passante plus élevée que celle des enrouleurs des câbles. Une commande prédictive optimale est proposée pour distribuer à la fois les efforts des câbles et des actionneurs embarqués contribuant au mouvement du robot.Des expérimentations, menées sur deux prototypes de robots parallèles à câbles, valident l’approche et évaluent les performances de l’amortissement actif des vibrations et du suivi de trajectoire.
... In foreign reference [27][28][29], an unconstrained quadratic thrust allocation method is proposed. Although the thrust allocation problem is transformed into an unconstrained quadratic optimization problem, the methods in reference [27][28][29] all consider the treatment of singularity, which shows that the method can avoid the singular structure of thrust allocation. ...
... In foreign reference [27][28][29], an unconstrained quadratic thrust allocation method is proposed. Although the thrust allocation problem is transformed into an unconstrained quadratic optimization problem, the methods in reference [27][28][29] all consider the treatment of singularity, which shows that the method can avoid the singular structure of thrust allocation. Reference [27] solved the problem of positive and negative thrust generated by rotary thrusters. ...
... In reference [28], the thrust direction is calculated by the expected generalized force of a low-pass filter, and the singularity is solved by using the damped least square method when the thrust is calculated. In reference [29], a variety of unconstrained secondary thrust allocation methods for fixed multi thrusters are proposed, and the thrust allocation under failure of one of the thrusters is also considered. ...
Dynamic positioning means that the ship can resist the influence of wind, wave, current and other environmental interference through its own propeller without anchoring, so as to realize the maintenance of its fixed position or expected track on the sea surface, with the advantages of not limited by water depth, rapid input or evacuation, good mobility and accurate positioning. This paper briefly introduces the components, working principle and mathematical model of the ship dynamic positioning system; On this basis, this paper summarizes the research status of the control strategy, filtering and data fusion, thrust distribution method and other related technologies of the ship dynamic positioning system at home and abroad; Finally, the development trend of the above-mentioned related technologies is discussed, so as to provide reference for the research in this field.
... Robust dynamic control allocation methods, in which the allocation also depends on the distribution in the previous sampling instant have been developed using quadratic programming [15]. However, these methods for thruster allocation are deemed relatively computationally expensive for on-board implementation [16]. ...
... In [16] the authors propose thruster allocation approaches based on Singular value decomposition (SVD) to reduce the computational expense of a minimum norm optimization. The neural-predictive control of this paper yields an optimal controller that avoids this three phase procedure and minimizes a cost-function of state-error and propellant use. ...
... The simple logic control (13) leads to N pulses = 634 thrust pulses with a settling time of 316s, and the projection control (16), after selecting the best coefficient k 1 = 4, leads to N pulses = 652 thrust pulses with a settling time of 323s. The number of thrust pulses and settling time of the NPC control are shown in Tab. 1, for various values of the tunable weights parameters of Eq. 29, using the normalization of R of Eq. 32 with constantR. ...
This paper tackles the problem of optimal attitude control using a minimal number of attitude thrusters. Three possible control solutions to this problem are presented: 1) a logic-based controller that is simple to implement, 2) a projective control that aims to optimally replicate an ideal continuous control as closely as possible, and 3) an optimal neural predictive control (NPC) that minimizes the total impulse during a maneuver. The NPC is based on a recurrent neural network using a nonlinear autoregressive exogenous configuration for state propagation in a finite-time horizon optimization. Typically, for continuous systems, a back-propagation algorithm for the receding horizon optimization is used, but this is not applicable to systems with discrete inputs. In this paper the NPC is adapted to boolean input systems by employing a robust genetic algorithm to undertake the receding horizon optimization. An automatic selection of the parameters of the cost function is proposed, which improves the performance of the NPC and reduces the tuning to only one parameter. In addition, a multilayer perceptron (MLP) is trained offline with the optimal control data obtained, thus replacing the CPU-intensive cost function with a significantly less computationally expensive metamodel. The NPC performance is compared with the proposed logic-based and projective control algorithms in simulation of a 12U CubeSat and is shown to be the most efficient in terms of total impulse requirement at equal settling time and the least sensitive to the choice of parameters. The MLP control drastically reduces the online computational cost with performance approaching those of the NPC.
... The optimization was non-convex due to existence of local minima. Garus presented the thrust allocation problem as an unconstrained optimization for an AUV [8]. The main achievement of the work was the less complexity in computations and more flexibility in structure of a propulsion system. ...
... In the planar case, a common and pretty intuitive configuration of 4 thrusters is given in [18] for underwater vehicles or in [19] for spacecrafts and is represented in Fig. 1. The thruster positioning is symmetrical with respect to the endeffector vertical and horizontal axes of symmetry. ...
... Both literature studies [1,2,3] and own experiments [6] show that in practice the problem of thrust allocation in the propulsion system of an underwater robot vehicle is most often formulated as a square programming task in the following form: The main reason for considering this issue as a square programming task is the square representation of the power/thrust relationship. Under certain assumptions, this relationship can also be approximated by the linear function, which allows one to consider this optimisation problem as a linear programming task, whose computational complexity is significantly lower. ...
... (6) where c is a vector of non-negative components.Since the cost function (5) contains absolute values, in order to apply the Simplex algorithm to solve the above optimisation problem it is necessary to transform the dependencies (5-6) to the following form: In the matrix denotation, the above linear programming task can be formulated as follows:with the limitations: Simulation studies were conducted in the MATLAB environment, using linprog functions for the linear programming task and quadprog functions for the square programming task [7]. Fig. 6 ...
This article addresses the practical aspects of the synthesis of an automatic control system for the thrust allocation strategy in the propulsion system of an unmanned underwater vehicle. The vehicle under consideration is a robot submarine equipped with a multi-propulsion system providing four degrees of freedom of movement. The power distribution algorithms are based on limited optimisation methods that allow the determination, on the basis of generalised torques and forces, of how much thrust is required to be produced by individual propulsors. Considering the issue of power distribution as a task of square and linear programming, two algorithms of thrust allocation were proposed and compared. The conducted model tests made it possible to evaluate their quality and efficiency in relation to speed and computational complexity.
... Generally speaking, if the underwater vehicle holds more actuators than the 6 Degrees Of Freedom (DOF), the system is considered as over-actuated. Nevertheless, from the geometrical configuration of the thrusters depends the manageability of this redundancy (Fossen, 1994;Garus, 2004). Omerdic and Roberts (2004) addresses the structural redundancy to afford the system with fault tolerance in order to cope with the loss of a thruster. ...
... The structural redundancy of the system provides the ability to control several tasks, as the task function approach (Mansard, 2006) proposes. For example in Garus (2004), the authors use a configuration matrix of the actuation, allowing for actuators selection according to a secondary function related to dependability ability. ...
This paper addresses the question of redundancy management of a vectorial actuation system of an underwater robot. The approach focuses on the compensation of the actuators structural imperfections: dead-zone and motor's response disparity. The solution is based on the identification of a correction matrix which highly improves the open-loop response of the actuation system. The effect is formally shown in the linear case approximation. Experimental validation shows the performance of the solution.
... 과구동기 시스템의 제어력을 할당하기 위한 추력배분은 항공 (Oppenheimer and Doman, 2007) 및 우주 (Henrik, 2005) 그리고 선박 (Berge and Fossen, 1997;Fossen and Johansen, 2006;Ji and Kim, 2012) 및 수중로봇 (Garus, 2004;Whitcomb and Yoerger, 1999) 분야뿐만 아니라, 자동차, 보행로봇, 멀티로봇 (Pedrami et al., 2009) (Craven et al., 1998). ...
... (5) ROV의 형상은 좌우 대칭이다. Garus, 2004). Fig. 8 과 같이 표현된다. ...
This study deals with the heading angle and depth keeping control technique for an ROV with multiple horizontal and vertical thrusters by thrust allocation. The light work class ROV URI-L, which is under development at KRISO, is a redundant actuating system with multiple thrusters that are larger than the ROV's degree of freedom. In the redundant actuating system, there are several solutions for a specific ROV motion to be performed. Therefore, a thrust allocation algorithm that considers the entire propulsion system should be regarded as important. First, this paper describes the propulsion system of the ROV and introduces the thrust allocation method of each motion controller. In addition, the performance of the controller is examined using a heading angle and depth keeping control test in a stationary state.
