Rudder Control Research Articles

Neural network controller for a multivariable model of submarine dynamics

Recently, there have been many attempts to use neural networks as a feedback controller. However, most of the reported cases seek to control Single-Input Single-Output (SISO) systems using some sort of adaptive strategy. In this paper, we demonstrate that neural networks can be used for the control of complex multivariable, rather than simply SISO, systems. A modified direct control scheme using a neural network architecture is used with backpropagation as the adaptive algorithm. The proposed algorithm is designed for Multi-Input Multi-Output (MIMO) systems, and is similar to that proposed by Saerens and Soquet [1] and Goldenthal and Farrell [2] for (SISO) systems, and differs only in the form of the gradient approximation. As an example of the application of this approach, we investigate the control of the dynamics of a submarine vehicle with four inputs and four outputs, in which the differential stern, bow and rudder control surfaces are dynamically coordinated to cause the submarine to follow commanded changes in roll, yaw rate, depth rate and pitch attitude. Results obtained using this scheme are compared with those obtained using optimal linear quadratic control.

Robust control methodology applied to the design of a combined steering/stabiliser system for warships

The consequences of roll motions in ship operations can seriously degrade the performance of mechanical and personnel effectiveness. To alleviate roll motions many ships are equipped with fin stabilisers. Rudders can also generate roll motions which can be harnessed to function in congress with the fins to accrue enhanced levels of stabilisation. An integrated rudder and fin stabilisation control strategy is proposed. Rudder roll controllers and autopilots are developed using the H∞ optimisation technique and their performance compared with the classical counterparts. Simulation studies are described that quantify the performance of the various controllers. The level of interaction present between the yaw and roll control loops is also examined. The study concludes that the overall performance of the H∞ RRS controller and autopilot is superior to that of the classical type. The level of interaction between the two loops can be suitably modified by varying the performance weighting functions. The study has concentrated on designing the controllers for frigates of the Royal Navy, however, the approach is suitable to present and future warship design.

Adaptive control of feedback linearizable nonlinear systems with application to flight control

The question of output trajectory control of a class of input-output feedback linearizable nonlinear dynamical systems using state variable feedback in the presence of parameter uncertainty is considered. For the derivation of a control law, a hypersurface is chosen which is a linear function of the tracking error, its derivatives, and the integral of the tracking error. An adaptive control law is derived such that in the closed-loop system, the trajectory asymptotically converges to this hypersurface. For any trajectory evolving on this surface, the tracking error tends to zero. Based on these results, a new approach to the design of an adaptive flight control system is presented. In the closed-loop system, trajectory control of the sets of output variables roll angle, angle of attack, and sideslip angle ( ,#,/?) using aileron, rudder, and elevator control is presented. Simulation results are obtained to show that precise simultaneous longitudinal and lateral maneuvers can be performed in spite of large uncertainty in the aerodynamic parameters.

F-15 forebody vortex flow control using jet nozzle blowing

A low-speed wind-tunnel test was conducted to determine the lateral-directional control effectiveness of a forebody jet nozzle blowing on a 10% scale F-15E model. This investigation of pneumatic forebody vortex flow control was the first of its kind performed on an F-15 configuration. The test acquired sixcomponent force balance data in the NASA Langley 30- by 60-Foot Tunnel at a freestream dynamic pressure of 8 psf at an equivalent Reynolds number per foot of approximately 5.08 X 10 5. Asymmetric forebody jet blowing was effective in generating yawing moments through an angle of attack (AOA) range that extends beyond the limit of rudder control power. The optimum nozzle configurations were pointed outward, and yawing moments generated within the maneuver range of AOA (a < 40 deg) increased with increases in both blowing rate and AOA. Above 10-deg AOA, blowing rates of C M = 0.010 and greater resulted in yawing moments that approached or exceeded that developed by full rudder deflection.

Nonlinear predictive control of feedback linearizable systems and flight control system design

The question of output trajectory control of input-output feedback linearizable nonlinear dynamic systems using state variable feedback is considered. For the derivation of the predictive control law, a vector function s is chosen as a linear combination of the tracking error, its higher order derivatives, and the integral of the tracking error. The control law is obtained by the minimization of a quadratic function of the predicted value of s and the control input. It is shown that in the closed-loop system the trajectories are uniformly ultimately bounded in the presence of uncertainty in the system parameters. Based on these results, a flight control system for the trajectory control of the output variables pitch, sideslip, and roll angles (0, /3, ) using aileron, rudder, and elevator control is presented. Simulation results are obtained to show that precise simultaneous longitudinal and lateral maneuvers can be performed in spite of the uncertainty in the aerodynamic parameters.

Evolving A Rule-Based Fuzzy Controller

In this article we demonstrate the application of genetic algorithms (GAs) to the automatic generation of fuzzy process controllers. Since each controller is represented as an unordered list of an arbitrary number of rules, the algorithm evolves both the composition and size of the rule base from initial randomness. Evolving controllers in the form of a rule base offers unique flexibility exceeding that of prior genetic efforts. The key to this methodology is the observation that the genetic algorithm does not merely evolve bit strings, but operates over a higher-level space of control rules. Both aspects are factors in the learning algorithm. To preserve rule integrity in a reproducing pair of strings, the combined loci must match semantically. This was the obstacle that hindered prior rule-based genetic fuzzy approaches. We demonstrate our algorithm by its application to the boat rudder control problem. We believe that this methodology has great potential for scalability since string size varies with the number of rules and not the number of variables or partitions. Finally, the method's generality permits its further application to the evolution of any system that can be specified as a set of rules.

A Multi Objective H∞ Solution to the Rudder Roll Damping Problem

Roll damping and simultaneous course steering by rudder control is a challenging problem where a key factor is roll damping performance in waves. Roll is a decisive factor for the operation of ships, both due to comfort of crew and passengers and due to requirements from cargo or on-board equipment. In the paper, roll damping and steering performance requirements are described and the controller design problem is formulated in an H∞ framework. It is shown how this design problem can be handled by using a multi objective H∞ approach. The design results are compared with an existing LQ design.

Cross Track Error and Proportional Turning Rate Guidance of Marine Vehicles

The problem of turning rate guidance and control of marine vehicles is considered. Feedback with feed forward rudder control is used to deliver a specified turning rate for the vehicle, while a guidance law is employed to create the necessary sequence of turning rate commands which would allow convergence to a desired geographical path. Two different guidance schemes are presented and analyzed, namely, cross track error and proportional turning rate guidance. Stability conditions are computed explicitly, while nonlinear analysis techniques illustrate the significance of design parameters on the final system response that cannot be inferred from linearized stability results.

Roll Reduction by Rudder Control for Two Ships During Underway Replenishment

A theoretical method for analyzing roll reduction by rudder control for ships during underway replenishment is developed. The basic idea is that, when the rudder is operating, yaw and roll moments will be generated that affect the rolling motion. This idea has been proven to be valid for a single ship running in waves and, therefore, is also applied in the present paper. Using the well-developed strip theory for two ships advancing in waves, a better set of gain coefficients for roll reduction by rudder control can be predicted a priori. From the present results, it is found that suitable rudder control indeed can reduce rolling motion especially at the resonance frequency. The results obtained by the present method can offer some valuable information for a roll-reducing autopilot. Rudder control therefore can be considered as another tool for reducing rolling motion while two ships are executing underway replenishment at sea.

Dynamic performance of towed vessels employing nonlinear rudder control under adverse weather conditions

A dynamic nonlinear model of a ship towed by a nonlinear elastic rope in the presence of sea current, wind and waves is formulated. Then, a nonlinear rudder controller is proposed for the towed vessel in order to limit its lateral motion in a narrow

不均一潮流中での船舶操縦運動の計算法と鳴門海峡における適用例

For the numerical calculation of ship maneuvering motion including the effect of non-uniformity of the current, it is necessary to obtain the distribution of hydrodynamic lateral forces along the ship's length. A new method proposed in this paper to determine this distribution along the ship's length is based on (1) the application of a wing theory for the linear force and (2) the use of the so-called cross-flow model for the non-linear force. Through the computations of ship turning motion in a shear flow and the comparison of the results with corresponding existing methods, it is found that the new method gives a reasonable yaw rate of a ship at the moment she enters or leaves the shear-flow region. By using this new method with a simple mathematical model for the rudder control by the helmsman, the safety maneuvering in Naruto Kaikyou is studied. An emphasis is mainly placed on the effects of non-uniform tidal current on the course-keeping ability of a ship. The effect of wind force is also investigated on the assumption that the wind is steady and uniform.

A stochastic rudder control law for ship path-following autopilots

A heuristic stochastic rudder control law for ship automatic path-following in restricted waters is presented. The objective is to make feasible an automatic pilot with an adaptive capacity of operating in situations where there is a great lack of knowledge of ship dynamics. State estimation and feedback control determination are separately treated. The extended Kalman filter is combined with a dynamical model compensation technique and a state noise adjustment procedure, in a situation where the observations have a high local level of information. An adaptive scheme results where unmodeled effects are estimated together with the system state. A feedback control law that uses state estimation information and steering conditions is proposed. In each discretization interval it takes a stepwise approximation for the control, as the solution of a parameter estimation problem. The performance of the resulting state estimator and controller is illustrated by results obtained through digital simulation. The test case selected is that of ship automatically steering in a channel under severe geometric and environmental conditions.

Aircraft parameter identification by the Gauss-Newton method in the frequency domain

Abstract A frequency-domain output-error method based on the Gauss-Newton minimization technique has been developed for the estimation of aircraft parameters from flight data. The method has been validated on simulated flight data. The effect of the intensity of measurement noise present in the flight data is studied and the method is shown to work satisfactorily even in the presence of high noise levels. Six different types of rudder and aileron control inputs have been used to generate the flight data; the analysis of such data is carried out to identify the suitable control input forms for the parameter estimation. Results are presented to show the effect of using the ‘packing theorem’ to increase the sparsely sampled frequency data; assigning a priori values to some of the weak parameters; and starting the iteration process with different initial values. Finally, a comparison of the method in the time domain and the frequency domain is presented to point out the relative merits of the latter approach.

Reduced noise monolithic wing-stabilizer aircraft

A sound reducing combined low mid-wing and horizontal stabilizer airplane with near longitudinal center line thrust twin engines having intensified aileron, elevator and rudder control. Small jet engines rigidly attached to the ailerons intensify attitude control for low speed manuevers.

Manoeuvrability of Ships in Narrow Waterway

In restricted waters such as harbour, bay or cannal, it is necessary to know the precise manoeuvring characteristics of ship including the effects of water depth, channel bank or the another ships from viewpoint of safety of navigation. In narrow waterways, specially, the effects of channel bank and hydrodynamic interactions between ships are fairly significant.This paper examines hydrodynamic behavior of ships during meeting and passing in narrow water channel, by using slender body theory. Furthermore, ship motions with rudder control during passing in channel by using these hydrodynamic forces are discussed. This paper concludes as follows.(1) During passing, the interaction forces, such as lateral force and yaw moment, between two ships are affected by the differences of ship speed and ship length, and by lateral distance between ships.(2) Lateral force and yaw moment acting on the ship are significant when the another larger ship passes nearby this ship.(3) By simulation study of ship motions, some problems on two way traffic in channel are noted.

Simulation Analysis of Steering Control During Underway Replenishment

Underway replenishment (UNREP) operations have always been a difficult maneuver, and are accomplished by manual control of U.S. Navy ships, using the most experienced personnel. The probability of collision during UNREP increases with decreasing distance between the ships. The David W. Taylor Naval Ship Research and Development Center has recently completed an exploratory development program to define and analyze the control parameters affecting the dynamic interactions between ships during UNREP, resulting in definition of some of the requirements for a prototype ship separation and sensing and control system. The UNREP control problem was simulated on a hybrid computer using analytical models of two identical Mariner-class ships, including consideration of nonlinear maneuvering equations, ship interaction forces and moments, regular waves, severe first-and second-order irregular waves, oblique seaway, time-sampled separation measurements, and low-pass filters. Assumed sensor inputs to the controller were longitudinal and lateral separation, lateral separation rate, relative yaw, relative yaw rate, and rudder angle. Results of the simulation indicate that first-order irregular-wave excitations dominate the UNREP rudder control problem in severe sea states. Use of either automatic or quickened (display-aided) manual control was found to be feasible, but additional work is needed to define the capabilities and limitations of quickening in this application, and to redesign the controller, using modern control theory techniques.

Adaptive Autopilot with Wave Filter

This paper is concerned with analysis and design of an adaptive autopilot for ships. The design is based on a low and high frequency model of the vessel motion adequate to ship steering. The low frequency model describes the vessel response to rudder control and slowly varying environmental forces. The high frequency model represents the wave induced oscillatory part of the yaw motion. The models are used in a Kalmanfilter and the rudder control is computed from linear quadratic theory based on the low frequency part of the state vector. This yields a very effective filtering of the wave component of the yaw motion. Proper operation of this filter/controller structure requires knowledge of the vessel model parameters and the dominating wave frequency. The vessel parameters are estimated on line by a recursive prediction error method. In order to reduce the computing requirements, the state estimator is operated using scheduled gains. This results in an easy and robust design. The Convergence properties are investigated by using the method of Ljung. The performance is exemplified by simulation experiments.

Improving the MLS Through Enhanced Cockpit Displays

The microwave landing system represents a major advancement in accurate, highly flexible positioning systems permitting the precise definition of curved approach paths. However, the exploitation of these capabilities also requires a comparable advancement in the presentation of information to the pilot. This paper presents a simulator investigation of various prediction and quickening algorithms in computer generated forward-looking displays to improve manual aircraft control on curved MLS approaches. Results indicate that second- and third-order predictor displays provide the best lateral performance. Intermediate levels of prediction and quickening provide best vertical control. Prediction/quickening algorithms of increasing computational order significantly reduce aileron, rudder, and elevator control responses, reflecting successive reductions in cockpit workload. Whereas conventional crosspointer displays are not adequate for manual control during curved landing approaches, perspective displays with predictors and some quickening in the vertical dimension only are highly effective. Additional research is needed to optimize the display for vertical control.

Prediction and Quickening In Perspective Flight Displays for Curved Landing Approaches

In an empirical test of various prediction and quickening display algorithms, 18 professional pilot-subjects made four curved-path landing approaches in a GAT-2 simulator using each of 18 dynamically different display configurations in a within-subject design. Results Indicate that second-and third-order predictor displays provide the best lateral performance. Intermediate levels of prediction and quickening provide best vertical control. Prediction quickening algorithms of increasing computational order significantly reduce aileron, rudder, and elevator control responses, reflecting successive reductions in cockpit work load. Whereas conventional crosspointer displays are not adequate for curved landing approaches, perspective displays with predictors and some vertical dimension quickening are highly effective.

Output feedback non-linear decoupled control synthesis and observer design for manoeuvring aircraft

A study of the applicability of nonlinear decoupling theory to the design of control systems using output feedback for maneuvering aircraft is presented. The response variables chosen for decoupled control were angular velocity components along roll, pitch, and yaw axes, angle of attack (p), and angle of sideslip, using aileron, rudder, and elevator controls. An observer design for a class of nonlinear systems was presented and this method was used to estimate angle of attack and sideslip; an approximate observer was obtained by neglecting derivatives of p and aileron deflection angles and it was used in a simulation study. A simulation study showed that precise rapid combined lateral and longitudinal maneuvers can be performed; it was also demonstrated that a bank-angle-command outer loop could be designed for precise bank angles changes and simultaneous large lift maneuvers.