Heading Angles Research Articles

Trajectory tracking for autonomous surface ships using Gaussian process regression and model predictive control with BVS strategy

Autonomous navigation is critical to the development of next-generation shipping systems. The proposal of intelligent ships enables innovation in the shipping and shipbuilding industry and increases the safety and efficiency of ship operations. Autonomous control of surface ships to follow a prescribed trajectory is critical in a variety of maritime applications. This paper proposes a trajectory tracking control strategy for autonomous surface ships that combines nonparametric modelling using Gaussian Process Regression (GPR) with the Model Predictive Control (MPC) framework. A Bézier curve-based Virtual Ship(BVS) guidance strategy is proposed to convert dynamic trajectory points into reference heading angles and speeds, such that the trajectory tracking problem can be decomposed into heading control and speed control problems. Gaussian process regression is utilised to identify the correlation between propeller revolution speed and ship speed, as well as the correlation between rudder angle and heading angle based on experimental data. Two GPR models are therefore constructed as the prediction models for designing MPC controllers for heading control and speed control, respectively. Nonlinear optimisation algorithms are utilised to search for optimal control commands in each sampling interval to solve the optimisation problem in MPC with GPR models and input constraints. Simulations are carried out to evaluate the effectiveness of the proposed method.

Low-cost dual-antenna GNSS-based heading and pitch angles estimation considering baseline length constraint

This contribution presents a vehicular heading and pitch angles estimation method based on the dual-antenna GNSS scheme, the baseline length is investigated as a priori nonlinear constraint to improve the estimation accuracy. The coordinates of the formed moving baseline are estimated first, the baseline length is exploited to enhance the ambiguity resolution process, and then its corresponding attitude angles are determined. The capability and reliability of the proposed algorithm are assessed by a real car-borne experiment with off-the-shelf, low-cost GNSS receivers. The driving trajectory contains both stationary periods and dynamic situations under the open sky and dense community environments. The experimental results show that, compared to the classical method that does not consider the baseline length constraint, the accuracy improvements of the proposed method on attitude angles range from 16.7% to 84.0% in different observation conditions, and the attitude errors of ambiguity fixed solutions are dominantly less than 5°.

Rapid and Near-Analytical Planning Method for Entry Trajectory under Time and Full-State Constraints

A rapid trajectory-planning method based on an analytical predictor–corrector design of drag acceleration profile and a bank-reversal logic based on double-stage adaptive adjustment is proposed to solve the entry issue under time and full-state constraints. First, an analytical predictor–corrector algorithm is used to design the profile parameters to satisfy the terminal of altitude, velocity, range, time, and flight-path angle constraints. Subsequently, an adaptive lateral planning algorithm based on heading adjustment and maintenance is proposed to achieve the flight stage adaptive division and determination of the bank-reversal point, thereby satisfying the terminal position and heading angle constraints. Concurrently, a rapid quantification method is proposed for the adjustable capacity boundary of the terminal heading angle. On this basis, a range-and-time correction strategy is designed to achieve high precision and the rapid generation of a three-degree-of-freedom entry trajectory under large-scale lateral maneuvering. The simulation results demonstrated that compared with the existing methods, the proposed method can adaptively divide flight stages, ensuring better multitask applicability and higher computational efficiency.

Effects of adverse sea conditions on the dynamic performance of a cruise ship integrated power system

In adverse sea conditions, changes in the propeller emergence depth can cause propulsion load fluctuations, resulting in significant variations in ship-integrated power systems (IPS). These fluctuations can severely affect the power quality of ships and the operational efficiency of electrical devices. To develop appropriate mitigation measures against the impact of wind and waves on IPS, a comprehensive model that can simulate the response characteristics of the hull and IPS for different heading angles in different sea conditions is necessary. This paper presents an integrated multi-system dynamic model capable of simulating the response characteristics of a ship's hull and its IPS under the wind and waves interference. A novel method is proposed to estimate propeller thrust and torque loss directly from the ship's pitch and roll angles. Utilizing this dynamic model, the responses characteristics of the hull and IPS in varying sea conditions have been investigated. The findings demonstrate that the model accurately captures variations in ship motions, as well as IPS voltage and frequency, under wind and waves interference. Additionally, this study explores the application of a hybrid energy storage system (HESS) to enhance the IPS power quality in the context of Sea State (SS) 7. Results indicate that the HESS has good potential to compensate for propulsion load fluctuations, thereby mitigating the negative impacts on the ship's IPS.

Steadiness of technical variables as a determinant factor of performance in a virtual simulated regatta

ABSTRACT The aim of this investigation is to explore the relationship between Optimist sailing performance with boat steadiness as well as the steadiness of cyclic variables related to sailors’ technique, in the upwind leg of a regatta. Thirty-two sailors from the optimist class (16 bottom level and 16 top level) performed a regatta in a semi-immersive simulator which measures the instantaneous velocity, heading, boom, heel, and rudder angle and hiking effort. It was calculated the mean values as well as the short-term steadiness and long-term steadiness throughout the test. Top level and bottom level sailors were compared and the correlation between these variables and mean velocity were analysed. Significant differences were found between groups on mean values, STS values and LTS values as well as significant correlations ranging r values between 0.385 and 0.768. If the steadiness of sailing variables is considered, they appear as determinants of performance in Optimist class while this is not observed when analysing mean values.

A Model-Based Adaptive Control of Turning Maneuver for Catamaran Autonomous Surface Vessel

The effective computer control of airborne, waterborne, and ground autonomous vehicles has become one of the highest priorities in the area of cyber-physical systems, Industry 4.0 in particular, and the world economy in general. Despite extensive research on Unmanned Aerial Vehicles (UAVs), the study of Autonomous Surface Vessels (ASVs) has been more than ten times less intense. As an attempt to fill a gap in that field, this article discusses the control mathematics of a realistic ASV nonlinear model of a real autonomous electric catamaran “Nymo”, which was designed at Tallinn University of Technology (TalTech). More technically, the article offers a novel adaptive control system that is based on knowledge of the main parameters of ASV and is specially designed for a Simulink/MATLAB environment. The article also enables adjusting variables like transition time and heading angle overshoot value. The control of the desired tracking is represented in such a maneuver as turning the catamaran at different angles. The designed control system has shown good quality in terms of accuracy in tracking the desired heading angles.

Research on Structural Collapse of a Containership under Combined Bending–Torsion by Oblique Waves

Large waves cause a great number of collapsed-ship accidents, resulting in the loss of many lives and properties. It has been found that most of these collapses are caused by encountering oblique waves. As a result, the ship structure experiences a complex collapse under combined bending and torsion. This paper utilizes a numerical hydroelasto-plastic approach, coupling CFD (Computational Fluid Dynamics) with the nonlinear FEM (Finite-Element Method), to study the structural collapse of a containership in oblique waves. First, a 4600 TEU containership was selected to study its collapse mechanism under oblique waves. Second, a hydroelasto-plastic numerical coupling of CFD and nonlinear FEM is used to co-calculate the wave loads and structural collapse of containership. The hydrodynamic model is constructed and used to solve wave loads in the CFD solver, and a nonlinear FEM model of containership with finer meshes is also modeled to solve the structural collapses, including plasticity and buckling. Third, several oblique-wave cases involving heading angles of 120°, 135°, 150°, and 180° are determined and calculated. Typical cases are discussed for time-domain stress histories and collapsed courses. Finally, the influence of oblique-wave parameters on structural collapse is discussed, and the collapse mechanism of containerships under the action of oblique waves is obtained, which provides a new understanding of ship structure design.

Frequency-Domain 3D Computer Program for Predicting Motions and Loads on a Ship in Regular Waves

The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain, is described in this paper. The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function. The code is fully developed in C++ language with extensive use of the object-oriented paradigm. The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles. The hydrodynamic responses such as hydrodynamic coefficients, ship motions, the vertical shear force and the vertical bending moment are estimated. A benchmark container ship and an LNG carrier are selected for testing and validating the computer code. The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.

Converting an allocentric goal into an egocentric steering signal.

Neuronal signals that are relevant for spatial navigation have been described in many species1-10. However, a circuit-level understanding of how such signals interact to guide navigational behaviour is lacking. Here we characterize a neuronal circuit in the Drosophila central complex that compares internally generated estimates of the heading and goal angles of the fly-both of which are encoded in world-centred (allocentric) coordinates-to generate a body-centred (egocentric) steering signal. Past work has suggested that the activity of EPG neurons represents the fly's moment-to-moment angular orientation, orheading angle, during navigation2,11. An animal's moment-to-moment heading angle, however, is not always aligned with its goal angle-that is, the allocentric direction in which it wishes to progress forward. We describe FC2 cells12, a second set of neurons in the Drosophila brain with activity that correlates with the fly's goal angle. Focal optogenetic activation of FC2 neurons induces flies to orient along experimenter-defined directions as they walk forward. EPG and FC2 neurons connect monosynaptically to a third neuronal class, PFL3 cells12,13. We found that individual PFL3 cells show conjunctive, spike-rate tuning to both the heading angle and the goal angle during goal-directed navigation. Informed by the anatomy and physiology of these three cell classes, we develop a model that explains how this circuit compares allocentric heading and goal angles to build an egocentric steering signal in the PFL3 output terminals. Quantitative analyses and optogenetic manipulations of PFL3 activity support the model. Finally, using a new navigational memory task, we show that flies expressing disruptors of synaptic transmission in subsets of PFL3 cells have a reduced ability to orient along arbitrary goal directions, with an effect size in quantitative accordance with the prediction of our model. The biological circuit described here reveals how two population-level allocentric signals are compared in the brain to produce an egocentric output signal that is appropriate for motor control.

ON THE STRUCTURAL VALUATION IN OBLIQUE WAVES OF A LARGE LIQUEFIED NATURAL GAS CARRIER BY 3D-FEM MODEL APPROACH

This structural valuation in oblique equivalent waves has as a study case a large LNG liquefied natural gas carrier, with an overall length of 289.3 m, structural gas membrane tanks, and a double hull. From the operation load cases, for the numerical study, a selection of the main cases is made, full cargo and ballast. The selected oblique design wave conditions are specific to unrestricted navigation areas, sagging and hogging wave-free surface, with the heading angle covering the oblique relevant cases. The computation of the LNG carrier equilibrium in oblique design waves is done by a three-parameter nonlinear approach, with the own P_QSW software. The 3D-FEM large LNG carrier model is developed by Femap/NX Nastran software. The structural valuation in oblique design waves, by strength and freeboard criteria, of the large LNG carrier involves 3D and 1D models. For practical purposes, the strength valuation results are synthesized as polar diagrams, for the relevant heading angles of the oblique design waves, representing the wave height safety limits for preserving the large LNG carrier structural integrity.

Investigation of water resistance of semi-submersible floating cranes of various designs

The paper considers the effect on water resistance of the movement of a semi-submersible floating crane model on quiet deep water in working and transport positions and different heading angles. The research was conducted in the experimental pool of Sevastopol State University. The performed towing tests of the model made it possible to plot the dependence of the coefficient of impedance on the Froude number. Each of the presented graphs refers to a certain horizontal clearance and heading angle, as well as the number of intermediate stabilization columns. According to the obtained graphs, it is possible to estimate the power of the power plant, mainline and shunting engines of a semi-submersible floating crane of the selected design scheme at the initial stages of design. In the future, it is planned to carry out research to determine the coefficient of additional resistance from the excitement of the considered cases of the hull shape.

Research on the identification method of key parts of ship target based on contour matching

A template matching method based on the contour fitting heading angle is proposed for the problem of identifying key parts of maritime ships. First, unmanned boats are used as hypothetical enemy targets to extract outer contours, build a matching template library, and establish relevant kinematic models. Based on the requirements of timeliness and relativism, the judgment conditions for fitting angles and heading angles are given. A traversal fitting framework is established based on the structural similarity index algorithm, and the target matching template is matched based on precise matching results. A motion space that combines position correlation, electro-optical detection distance, and target pitch decoupling is designed to obtain real heading angles. Finally, based on the relative position information of the template’s key parts, the key parts of the target are matched, and the normalized output matching image is obtained. The experiment shows that this method can achieve recognition instructions in real seaways where key parts of the target cannot be extracted due to the large amount of water mist, and it has advantages in timeliness, accuracy, and applicability compared with other algorithms. This method has strong robustness and provides a reference for the identification of key parts of various types of ship targets.

Modeling and analysis of nonlinear backstepping controller for the crazyflie quadrotor trajectory tracking

This paper illustrates the Newton-Euler laws-based nonlinear dynamic model of a Crazyflie Quadrotor Unmanned Aerial Vehicle (CF-QUAV). It demonstrates the state-space-form equations that govern how the CF-QUAV moves around its frame (body). A Proposed nonlinear control strategy is used to regulate the height (z), position (x, y), attitude (roll and pitch), and heading (yaw) angles. This strategy is based on a Backstepping nonlinear controller defined by Lyapunov theory. The proposed controller can replace the Proportional-Integration-Derivative (PID) controller utilized in the CF-QUAV model to follow the desired trajectories gleaned from CF lab tests. In addition, the parameters of the proposed controller are tuned using the Genetic Algorithm (GA) in order to achieve the best performance and stability of the CF-QUAV model. Simulation-based experiments with statistical analysis are carried out to evaluate the performance of the proposed nonlinear controller and compare its performance and stability with the linear PID controller.

Modeling the influence of wind on ship circulation elements

When solving a number of practical problems of navigation and ship maneuvering, it is necessary to take into account the effect of wind on the parameters of the ship motion, including curvilinear motion, in particular, on circulation. There is very little information on this problem, especially in terms of quantitative estimates of the wind impact on circulation elements. Based on this, the purpose of this work is to study the effect of wind on the circulation elements based on mathematical modeling and to determine quantitative estimates of this effect when changing such factors as wind speed and heading angle, ship length and rudder angle. The simulation is carried out on a certified navigation simulator Transas NT Pro-5000. The mathematical model of vessel movement and wind effect used in this simulator is presented in the paper. A description of three simulated container ships with similar aerodynamic characteristics is given for the various heading angle and velocity of the wind before the start of the turn. In some experiments, the rudder angle is changed. The results of the simulation are presented in tabular and graphical forms. Quantitative estimates of the displacement of the turning points on the circulation by 90°, 180°, 270° and 360° at wind influence from the corresponding points of circulation in the absence of wind. The graphical dependences of these displacements on the heading angle of the wind and their analytical approximations are presented. The ranges of the wind heading angles at which the maximum effect of the wind on the circulation elements is observed are established. Quantitative estimates of the inversely proportional dependence of the circulation elements on the ship length are calculated. The hypotheses of the other authors about the direction of displacement of the circulation curve under wind action are tested. To verify the validity and reliability of the results obtained, it is necessary to perform similar studies using other mathematical models and natural experiments.

Research on Path Planning and Path Tracking Control of Autonomous Vehicles Based on Improved APF and SMC.

Path planning and tracking control is an essential part of autonomous vehicle research. In terms of path planning, the artificial potential field (APF) algorithm has attracted much attention due to its completeness. However, it has many limitations, such as local minima, unreachable targets, and inadequate safety. This study proposes an improved APF algorithm that addresses these issues. Firstly, a repulsion field action area is designed to consider the velocity of the nearest obstacle. Secondly, a road repulsion field is introduced to ensure the safety of the vehicle while driving. Thirdly, the distance factor between the target point and the virtual sub-target point is established to facilitate smooth driving and parking. Fourthly, a velocity repulsion field is created to avoid collisions. Finally, these repulsive fields are merged to derive a new formula, which facilitates the planning of a route that aligns with the structured road. After path planning, a cubic B-spline path optimization method is proposed to optimize the path obtained using the improved APF algorithm. In terms of path tracking, an improved sliding mode controller is designed. This controller integrates lateral and heading errors, improves the sliding mode function, and enhances the accuracy of path tracking. The MATLAB platform is used to verify the effectiveness of the improved APF algorithm. The results demonstrate that it effectively plans a path that considers car kinematics, resulting in smaller and more continuous heading angles and curvatures compared with general APF planning. In a tracking control experiment conducted on the Carsim-Simulink platform, the lateral error of the vehicle is controlled within 0.06 m at both high and low speeds, and the yaw angle error is controlled within 0.3 rad. These results validate the traceability of the improved APF method proposed in this study and the high tracking accuracy of the controller.

Ship collision avoidance control based on improved velocity obstacle method

The velocity obstacle method has extensive research in collision avoidance, which uses circles to represent robots or ships to find a collision-free velocity. To better describe the motion characteristics of ships, an improved velocity obstacle method based on elliptical ship domain is proposed in this paper. In the previous research on collision avoidance, the ship domains of the own ship and the target ship are seldom considered at the same time. This paper considers the ship domains of the own ship and the target ship at the same time and judges whether the ship domains of the two ships overlap based on the generalized characteristic polynomial. The heading angle is discretized to construct the velocity obstacle (VO) by calculating the collision velocity at different heading angles. Velocities on the boundaries of the velocity obstacle are used to find an optimal heading angle. The algorithm is tested in different encounter situations and successfully realizes collision avoidance.

ОБОСНОВАНИЕ ЭЛЕКТРОННОЙ КОМПОНЕНТНОЙ БАЗЫ ДЛЯ АВТОГЕНЕРАТОРОВ ПРИ НАВИГАЦИОННОМ ОБЕСПЕЧЕНИИ БЕСПИЛОТНЫХ ЛЕТАТЕЛЬНЫХ АППАРАТОВ

The study analyzes the tasks of air objects navigation support. The authors conducted a synthesis of a flight route of an unmanned aerial vehicle with the choice of heading angles of flight at turning points using the direction finding signals received from a stationary ground source. The root-mean-square errors are estimated based on the flying tests. These errors determine a location of emitters during multiple estimation of angular coordinates at points separated in space by direction-finding receivers placed on board of unmanned aerial vehicles “Orlan-10”, “Phoenix”, and “Grant-M”. Methods for correcting autonomous flight with increasing and decreasing accuracy in estimating signal arrival directions are studied, which make it possible to minimize positioning errors for a fixed observation time. The study proposes a scheme of a self-excited oscillator on a field-effect transistor for backup command control with automatic heading angle control. A rule is substantiated for constructing a model of a selfexcited oscillator that meets the requirements for a minimum standard deviation calculated using an electrical circuit and a given heading angle with a restriction on the physical feasibility of the layout parameters of a given structure. Recommendations for the implementation of the electronic circuit are formulated and the modes of self-excitation of the oscillator are determined.

Fast Trajectory Generation on a Path using Feedback Linearization*

This paper describes a method for quickly generating feasible trajectories for fully actuated autonomous surface vehicles. It is assumed that a path consisting of a list of positions with associated heading angles is given. The goal is to generate a feasible trajectory that follows a given path and takes into account the nonlinear dynamical model. The trajectory contains the state as well as force-level input variables and can be used as feed-forward control by a trajectory controller. The generation of the trajectory is based on a closed-loop simulation of the nonlinear model in combination with a nonlinear controller and guidance law. Feedback linearization is applied to linearize the motion model of the surface vehicle at the velocity level. A state feedback controller is used to control the pose along the path. The presented method allows for simple and fast trajectory generation and can therefore be applied in sampling-based motion planners where many trajectories have to be generated.

Deep Neural Network-Based Footprint Prediction and Attack Intention Inference of Hypersonic Glide Vehicles

In response to the increasing threat of hypersonic weapons, it is of great importance for the defensive side to achieve fast prediction of their feasible attack domain and online inference of their most probable targets. In this study, an online footprint prediction and attack intention inference algorithm for hypersonic glide vehicles (HGVs) is proposed by leveraging the utilization of deep neural networks (DNNs). Specifically, this study focuses on the following three contributions. First, a baseline multi-constrained entry guidance algorithm is developed based on a compound bank angle corridor, and then a dataset containing enough trajectories for the following DNN learning is generated offline by traversing different initial states and control commands. Second, DNNs are developed to learn the functional relationship between the flight state/command and the corresponding ranges; on this basis, an online footprint prediction algorithm is developed by traversing the maximum/minimum ranges and different heading angles. Due to the substitution of DNNs for multiple times of trajectory integration, the computational efficiency for footprint prediction is significantly improved to the millisecond level. Third, combined with the predicted footprint and the hidden information in historical flight data, the attack intention and most probable targets can be further inferred. Simulations are conducted through comparing with the state-of-the-art algorithms, and results demonstrate that the proposed algorithm can achieve accurate prediction for flight footprint and attack intention while possessing significant real-time advantage.

Algorithm of the autonomous initial alignment of sins with sequential filtering

An algorithm for an autonomous initial alignment of a strapdown inertial navigation system on a fixed or limitedly movable base is proposed and considered. It sequentially uses two Kalman averaging filters in. The first one determines one column of the directing cosines matrix (DCM) between the axes of the associated with the object and the geographical accompanying bases by the signals of the accelerometers. The second filter determines the second column of the matrix based on the gyroscope signals and the obtained estimates of the direction cosines. The third column is determined from known ratios. From the resulting DCM, the heading, pitch and roll angles are determined. Information signals for solving the problem are obtained by averaging a small interval (5 s) at the end of the Kalman filter transition process. This allows minimizing errors from changing the position of the object during the measurement time, which can reach tens of minutes. The advantage of the algorithm is the independence of errors from the object heading. It is shown that pre-smoothing of signals improves accuracy. The algorithm makes it possible to determine the orientation angles, and then the direction cosines at a measurement time insufficient to complete the transient evaluation process by the Kalman filter. The conducted field experiments confirm the good characteristics of the alignment on a fixed and vibrating base, achieved using the algorithm.