Showing papers on "Rudder published in 2003"

Acceleration Feedback in Dynamic Positioning

Abstract: This dissertation contains new results on the design of dynamic positioning (DP) systems for marine surface vessels A positioned ship is continuously exposed to environmental disturbances, and the objective of the DP system is to maintain the desired position and heading by applying adequate propeller thrust The disturbances can be categorized into three classes First, there are stationary forces mainly due to wind, ocean currents, and static wave drift Secondly, there are slowly-varying forces mainly due to wave drift, a phenomenon experienced in irregular seas Finally there are rapid, zero mean linear wave loads causing oscillatory motion with the same frequency as the incoming wave train The main contribution of this dissertation is a method for better compensation of the second type of disturbances, slowly-varying forces, by introducing feedback from measured acceleration It is shown theoretically and through model experiments that positioning performance can be improved without compromising on thruster usage The specific contributions are: • Observer design: Two observers with wave filtering capabilities was developed, analyzed, and tested experimentally Both of them incorporate position and, if available, velocity and acceleration measurements Filtering out the rapid, zero mean motion induced by linear wave loads is particularly important whenever measured acceleration is to be used by the DP controller, because in an acceleration signal, the high frequency contributions from the linear wave loads dominate • Controller design: A low speed tracking controller has been developed The proposed control law can be regarded as an extension of any conventional PID-like design, and stability was guaranteed for bounded yaw rate A method for numerically calculating this upper bound was proposed, and for most ships the resulting bound will be higher than the physical limitation For completeness, the missing nonlinear term that, if included in the controller, would ensure global exponential stability was identified The second contribution of this dissertation is a new method for mapping controller action into thruster forces A low speed control allocation method for overactuated ships equipped with propellers and rudders was derived Active use of rudders, together with propeller action, is advantageous in a DP operation, because the overall fuel consumption can be reduced A new model ship, Cybership II, together with a low-cost position reference system was developed with the aim of testing the proposed concepts The acceleration experiments were carried out at the recently developed Marine Cybernetics Laboratory, while the control allocation experiment was carried out at the Guidance, Navigation and Control Laboratory The main results of this dissertation have been published or are still under review for publication in international journals and at international conferences

Enhanced flight control systems and methods for a jet powered tri-mode aircraft

Abstract: A method of stabilizing a jet-powered tri-mode aircraft as the aircraft travels in a helicopter mode, a compound mode, and a fixed-wing mode is disclosed. The method includes receiving a plurality of velocity vector component values and velocity vector commands derived from either (1) a number of pilot operated controllers or (2) a commanded array of waypoints, which are used for fully automated flights, and a rotor speed reference value, which is decreased with increasing forward speed to unload the rotor, thereby permitting conditions for stopping the rotor in flight. Stabilization of the commanded velocity vector is achieved in all modes of flight using blended combinations of rotor swashplate controls and aerodynamic controls such as elevons, canards, rudders, and a horizontal tail. Stabilization to the commanded velocity vector includes a plurality of control constraints applied to the pilot stick controllers that prevent penetration of envelope limits.

Fuel-efficient rudder and propeller control allocation for marine craft: experiments with a model ship

Abstract: We derived a control allocation algorithm for low-speed marine craft using propellers and rudders. Active use of rudders has advantages in a low-speed operation by decreasing the need for propeller power and fuel. However, at low speed, a rudder is effective only for positive thrust. This complicates the thrust allocation problem which can no longer be solved by convex quadratic programming. In fact, the existence of local minima introduces discontinuities in the commanded thruster signals even if the desired control force is continuous. Discontinuous signals cause excessive wear on the thruster system and must be avoided. This paper suggests an analytic, 2-norm optimal method that can ensure continuity of the solutions. Being analytic, however, its limitation is the capability of handling only configurations where one single thrust device is subject to sector constraints at a time. Experiments with a model ship illustrate the potential for fuel saving. For this particular vessel, the energy consumption was halved. An output feedback tracking control law with integral action was simultaneously derived and analyzed. Semiglobal ship controllers like this one rely on the yaw rate being bounded, and an admittedly conservative method for determining this upper bound was proposed.

Steering control system and method for watercraft

Abstract: A steering system for a watercraft provides a position command signal indicative of a position of a rudder. An azimuth or location sensor senses an azimuth or a location of the watercraft, respectively. A control data input device selectively provides a control device with a manual mode signal and an autopilot mode signal. The autopilot mode signal is accompanied by a target azimuth signal or a target location signal. The control device controls the position of the rudder unit based upon the position command signal in the manual mode. The control device controls the position of the rudder unit such that the actual azimuth coincides with the target azimuth. The control device places the watercraft in the manual mode in place of the autopilot mode without the manual mode signal if the position command signal changes while the control device controls the position of the rudder unit in the autopilot mode.

Aircraft control surface controller and associated method

Abstract: A control surface controller (200) and a method of controlling a control surface interface includes a control surface interface for controlling one or more of the aerodynamic control surfaces (204) on an aircraft, such as ailerons, spoilers, elevators, and a rudder. A control surface controller (200) and a method of controlling a control surface interface (204) also include a variable resistance damper (220) that provides physical resistance to the control surface interface in proportion to control surface interface input rate. Accordingly, the resistance provided to the control surface interface may be selected in order to prevent the cause of pilot-induced-oscillation or airplane-pilot coupling. The resistance provided to the control surface interface may also be selected in order to limit the servovalve rate which reduces peak transient hydraulic fluid pressure in the hydraulic system.

Steer by wire helm

Abstract: A helm apparatus for a marine craft or other vehicle having a steered member such as a rudder includes a mechanically rotatable steering device and a sensor which senses angular movement of the steering device when the craft is steered A communication link to the rudder enables the helm to monitor the rudder position A bi-directional stop mechanism is actuated when the helm determines that the rudder position is beyond starboard or port hard-over thresholds, indicating that the rudder has reached a limit of travel The helm can cause the stop mechanism to fully engage the steering device to stop further rotation of the steering device in a first rotational direction, corresponding to rotational movement towards said limit of travel Rotational play is provided between the sensor and the stop mechanism, whereby the steering device can be rotated a limited amount, relative to the sensor, when the stop mechanism is fully engaged The stop mechanism is released from engagement with the steering device when the sensor senses that the steering device is rotated, as permitted by said play, in a second rotational direction which is opposite the first rotational direction Additionally, the same stop mechanism, or an optional steering effort mechanism, can be used to provide a dynamic steering effort, whereby the torque required to rotate the steering shaft is varied based on system inputs and configurations The required torque is changed by fluctuations of the amount of friction between the steering effort mechanism and steering shaft, based on system inputs and configurations

Speed synchronously controlled electrohydraulic load simulator

Abstract: An electro-hydraulic load simulator with synchronous control of speed is an improvement on electro-hydraulic servo loading system for the rudder of fly vehicle, and is composed of a position servo system, a torque servo system and simulative momental between the first two. Its feature is that the output of rudder driver in position servo system is connected with the input of compensator in torqueservo system. Its advantages are high effect on eliminating excess force and high interference eliminating power up to 95%.

Method and device for allocating thrust

Abstract: Force balance and moment balance associated with thrust of air and water craft equipped with thrust generators are preset in view of non-linear characteristics and dynamic characteristics of thrust generators A performance index for minimizing thrusts generated by the thrust generators is defined Using the balance as restricting condition, propeller thrusts of the thrust generators and rudder angles and changing speeds of rudders that minimize the performance index are calculated

Assessment of a mathematical model for the manoeuvring motion of a twin-propeller twin-rudder ship

Abstract: The MMG mathematical model [1] is well known and widely used for describing the manoeuvring motion of a ship. The MMG model is a modular type mathematical model which has proven to be useful in predicting various aspects of manoeuvring motion. However, this model was originally developed for the single-propeller single-rudder ship. Nowadays there are many multi-propeller multi-rudder ships, but little is known about the manoeuvring characteristics of the multi-propeller multi-rudder ship. In this paper, the authors develop the mathematical model to predict the manoeuvring motion of a twin-propeller twin-rudder ship, which was selected as one of the most popular configurations of multi-propeller multi-rudder ships. Initially, the various parameters included in the mathematical model for manoeuvring motion are investigated experimentally for a twin-propeller twin-rudder ship. The authors subsequently modified the mathematical model of the single-propeller single-rudder ship, and proposed a new mathematical model for the twin-propeller twin-rudder ship [2]. Finally, the predicted manoeuvring motion of the twin-propeller twin-rudder ship was compared with the test results of a free-sailing model in order to examine the validity of the proposed mathematical model.

Numerical analysis of podded and steering systems using a velocity based source boundary element method with modified trailing edge

Abstract: This paper describes an improved velocity based source boundary element method (BEM) as applied to modeling of podded propellers and propeller/rudder systems. The distinctive feature of the present method consists in the direct satisfaction of the Kutta-Joukowski condition on the additional Kutta panel constructed behind the realistic blade trailing edge when defining the unknown doublet strength. This Modified Trailing Edge (MTE) is also used as a tool for the approximate accounting for viscous and related effects on circulation. The integrated propulsive/steering system is simulated within the potential frameworks using the velocity field iterations method and quasi-steady approach, which assumes the simulation of propeller in a spatially varying flow field while pod and strut(/rudder) are considered in a circumferentially averaged flow field. The developed method is applied for calculation of rudder behind the operating propeller and podded units of different arrangement tested at MARINTEK (Norwegian Marine Technology Research Institute). The results of the measurements and theory/experiment comparisons are discussed.

Numerical modeling of rudder sheet cavitation including propeller/rudder interaction and the effects of a tunnel

Abstract: This paper presents the coupling of a vortex lattice method (MPUF-3A), a finite volume method (GBFLOW3D), and a boundary element method (PROPCAV) to allow for the prediction of rudder sheet cavitation, including the effect of propeller, as well as the effects of tunnel walls. The unsteady cavity prediction on the propeller blades is performed using MPUF-3A to satisfy both a constant pressure condition on the cavity surface and the flow tangency condition on the cavity and blade surfaces. The effects of the tunnel and a vortical inflow are modeled via GBFLOW-3D by solving the 3-D Euler equations with slip boundary conditions on the walls and by representing the effect of the propeller blades via body forces. The cavity prediction on the rudder is accomplished via PROPCAV (which can handle back and face leading edge or mid-chord cavitation) in the presence of the 3-D flow field produced by the propeller. This flow-field is determined via GBFLOW-3D, in which the propeller is represented via a non-axisymmetric distribution of body forces. The effects of the tunnel walls are also considered in this case by applying a boundary element method on the walls, in the presence of the rudder. A multi-block Euler scheme is also developed in order to determine the effect of the rudder on the propeller

Watercraft steering assist system

Abstract: A steering assist system for a watercraft including a force detection assembly adapted to detect a force further applied to an operator steering control of the watercraft after the steering control is turned to a maximum turning position. The steering assist system also includes a controller configured to increase a steering force produced by the watercraft in response to an output of the force detection assembly. In one arrangement, the steering assist system increases an output of a propulsion system of the watercraft in proportion to an output of the force detection assembly. In another arrangement, the steering assist system moves a steering force producing member, such as a deflector or rudder, for example, in response to an output of the force detection assembly in addition to, or alternative to, increasing an output of the propulsion system.

Broaching prediction in the light of an enhanced mathematical model with higher order terms taken into account

Abstract: We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried out with these second-order terms of waves, and the results were compared with the results of free-running model experiments. An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves are not so crucial for predicting the capsizing boundaries themselves.

Numerical simulation for the rudder in order to control the cavitation phenomena

Abstract: In these ten years, the cavitation and erosion phenomena in the rudder have been increased for high-speed container ships. The cavitation in the rudder blades which is injurious to rudder efficiency is mainly caused by the main flow with a large angle of attack induced by propellers, and the erosion which occurs as a result of repeated blows by shock wave that cavitation collapse may produce was observed in the gap legion of the rudder. However, gap cavitation is not prone to occur in model experiments because of low Reynolds number. So, the viscous effect should be considered for solving the flow of the narrow gap. In order to predict the cavitation phenomena and to improve the performance of the rudder, the analysis of the viscous flow in the rudder gap is positively necessary. In this study, numerical calculation for the solution of the RANS equation is applied to the two-dimensional flow around the rudder gap including horn part and pintle part. The velocity and pressure field are numerically acquired according to Reynolds number and the case that the round bar is installed in the gap is analyzed. For reduced the acceleration that pressure drop can be highly restrained numerically and in model experiment, the cavitation bubbles can be reduced.

Real-time flight simulation monitor system

Abstract: A real-time simulation-monitor system for airplane is disclosed. The flight parameters of an airplane is transmitted via communication controller, data transmission radio station and antenna to a ground station directly or through a nevigation satellite. The preprocessor and main controller can transmit them to multiple terminals for simulatively displaying the flight state, and position of air plane on a digital map, and the states of flight path, rudder and landing chassis are received and displayed with real-time parameters. The signals and related parameters can also be transmitted back to airplane.

Investigations of a Control Surface Seal for Reentry Vehicles

Abstract: Reentry vehicles generally require control surfaces such as rudders and body flaps to steer them during flight. Control surface seals are installed along hinge lines and where control surface edges move close to the vehicle body. These seals must operate at high temperatures and limit heat transfer to underlying structures to prevent overheating and possible loss of vehicle structural integrity. Test results are presented for the baseline rudder/fin seal design for the X-38 reentry vehicle. Compressing seals at the predicted peak seal temperature of 1900°F resulted in loss of seal resiliency. The vertical Inconel rudder/fin rub surface was redesigned to account for this loss of resiliency. Room-temperature compression tests revealed that seal unit loads and contact pressures were below limits set to protect shuttle thermal tiles on the horizontal sealing surface. The seals survived an ambient-temperature 1000 cycle scrub test over sanded shuttle tiles and were able to disengage and reengage the tile edges during testing. Arcjet tests on a single seal caused a large temperature drop (ΔT = 1710°F) in the seal gap and confirmed the need for seals in the rudder/fin gap location. These test results verified that this seal is satisfactory for the X-38 application.

A novel method of ship manoeuvring model identification from sea trials

Abstract: The ship manoeuvring dynamics consists of surge, sway, and yaw differential equations (coupled mutually with each other). a basic principle of the proposed manoeuvring model identification algorithm is that both sway and yaw equations may directly assimilate, instead of the motions derived from other one or two equations, the corresponding sea trial data. Under such conditions, the evaluated hull and rudder sub-models are more adequate and less ambiguous. An approach has been made also to compose the hull hydrodynamics from turning tests, while z-tests refine the rudder related model parameters. The obtained final manoeuvring prediction is excellent.

Maneuvering of Surface Vessels Using a Fuzzy Logic Controller

Abstract: A fuzzy logic controller is developed for maneuvering control of surface vessels. The fuzzy controller uses a vessel's heading, yaw rate, distance from a reference point, and the velocity of the vessel relative to the reference point as inputs to generate the control outputs. The control outputs include rudder angle, increase in propeller thrust, and lateral bow thrust. The design of the fuzzy controller is simple and does not require a mathematical modeling of the complicated nonlinear system. The core of the fuzzy controller is a set of fuzzy associative memory (FAM) rules that correlate each group of fuzzy input sets to a fuzzy output set. A FAM rule is a logical if-then type statement based on one's sense of realism, experience, and expert knowledge. The effectiveness and robustness of the fuzzy controller are demonstrated through the numerical time-domain simulations of path tracking and dynamic positioning of a Mariner-class hull with use of nonlinear maneuvering equations of motions.

Ground-effect craft and method for the cruising flight thereof

Abstract: The invention relates to flying vehicles. A centre wing is provided with aerodynamic profiles on the longitudinal sections thereof. A cigar-shaped fuselage is arranged on the central wing. A crew cabin and a cargo-passenger cabin are arranged inside the fuselage. Hollow hermetical longitudinal beams are mounted on the periphery of the central wing on the sides thereof. Inflatable shock-absorbing balloons are arranged under said longitudinal beams. Two keels provided with rudders are mounted on the ends of the longitudinal beams. A horizontal tail is arranged on the keels and comprises a diving rudder which is disposed on a section between the keels and ailerons which are disposed on the sections of the longitudinal beams. The thrust propeller for horizontal thrust is accommodated inside an external annular cowl. The engine for the thrust propeller is arranged inside the tail cone of the fuselage. A set of tale-off and landing devices comprises a means for producing a static air cushion. The cruising flight of the inventive ground-effect craft is carried out by the propeller thrust and a lifting force produced by the interaction of the central wing and a ram air and by the ground-effect of a ground or water surface. The height over ground or water surface must be equal to 0.1-0.5 of the mean chord of the central wing or to 0.2-0.9 of the span thereof when the angle of attack of the central wing is equal to 5-6°, the horizontal propeller thrust ranges from 0.25 to 0.33 of the flying weight of the craft and the speed is equal to 200-280 km/h.

Method and device for allocating thrust to air or water craft

Abstract: Force balance and moment balance associated with thrust of air and water craft equipped with thrust generators are preset in view of non-linear characteristics and dynamic characteristics of thrust generators. A performance index for minimizing thrusts generated by the thrust generators is defined. Using the balance as restricting condition, propeller thrusts of the thrust generators and rudder angles and changing speeds of rudders that minimize the performance index are calculated.

Lifting body aircraft and reentry vehicle

Abstract: A lifting body aircraft suitable for atmospheric flight and/or as a reentry vehicle. The craft has a substantially flat upper surface, a lower surface with a doubly convex first section and a flat sloping second section. The doubly convex first section allows the craft to have its center of gravity forward of its longitudinal center line. The flat sloping second half of the lower surface and the substantially flat upper surface form the aft end of an airfoil. A pair of vertical stabilizers enhance stability and include rudders which, along with a pair of elevons, provide steerage. The craft may glide or it may have an engine or rockets for thrust. The result is an extremely stable lifting body design that is well suited for launch or conventional take off, insertion, orbital operations, reentry, atmospheric flight, and conventional landings.

Steering controlling device for vehicle

Abstract: PROBLEM TO BE SOLVED: To perform a road surface friction adaptive control by a simple constitution without newly providing a special sensor or the like to at least one of steering controls for the front wheels and the rear wheels of a vehicle SOLUTION: At a feed forward control section FF, a first target value is calculated in response to a norm yaw rate and a norm lateral acceleration based on a front wheel rudder angle (steering angle) At the same time, at a feed back control section FB, an (actual) yaw rate and an actual lateral acceleration are respectively compared with the norm yaw rate and the norm lateral acceleration, and a second target value is calculated based on a yaw rate deviation and a lateral acceleration deviation of the comparison result In addition, at a road surface friction estimating section ES, respective sections are adjusted in response to a set road surface friction corresponding gain, based on a correlation between yaw rate identified models of the front wheel and rear wheel rudder angles and the (actual) yaw rate, and the road surface friction adaptive control is performed Then, an actuator is controlled by a rear wheel rudder angle servo control section SC based on a target rear wheel rudder angle for which the second target value is added to the first target value COPYRIGHT: (C)2005,JPO&NCIPI

Comparison between Manoeuvring Trials and Simulations with Recursive Neural Networks

Abstract: This paper compares between the results obtained in manoeuvrability trials and simulated trajectories using Artificial Neural Networks. The tests considered in this paper were carried out with a fast patrol vessel. A Recursive Neural Network manoeuvring simulation model for surface ships has been developed. Input to the simulation are the orders of rudder angle, the ship’s speed and the recursive output velocities of sway and yaw. The comparison between tests and simulations show the good performance of the model.

Rudder angle detector

Abstract: PROBLEM TO BE SOLVED: To specify an absolute rudder angle of a steering shaft when an ignition switch is turned on. SOLUTION: A rudder sensor 5 detecting the rudder angle of the steering shaft 3 and tie-rod angle sensors 15-1 and 15-2 detecting the tie-rod angle against shaft direction of rack axes 9 of tie-rods 10-1 and 10-2 are connected to an electronic control unit 13. The electronic control unit 13 receives the input of tie-rod angle signal detected by the tie-rod angle sensors 15-1 and 15-2, and determines revolution direction and revolution number of the steering shaft 3. Based on the determined result and with the rudder angle signal from the rudder angle sensor 5, the control unit specifies the absolute rudder angle from a neutral position of the steering shaft 3. COPYRIGHT: (C)2004,JPO

Unsteady Hydrodynamic Behaviour of a Rudder Operating in the Propeller Slipstream

Abstract: In order to determine rudder dimensions, a reasonably accurate prediction of the hydrodynamic forces generated by the rudder configuration should be obtained. Several methods were developed to simulate this interaction by coupling potential code and RANSE code. The obtained results agree well with experimental results. The computational speed allows a parametric analysis of the interaction (rudder position, propeller load, etc.). Several configurations are simulated in both steady and unsteady state modes in order to estimate the influence of geometric parameters on the hydrodynamic coefficients of a rudder operating in the propeller slipstream.