Models of DP systems in full mission ship simulator

Transcription

1 Scientific Journals Maritime University of Szczecin Zeszyty auowe Aademia Morsa w Szczecinie 2010, 20(92) pp , 20(92) s Models of DP systems in full mission ship simulator Modele systemów dynamicznego pozycjonowania w wielozadaniowym symulatorze statu Paweł Zalewsi Maritime University of Szczecin, Faculty of avigation, Institut of Marine Traffic ngineering Aademia Morsa w Szczecinie, Wydział awigacyjny, Centrum Inżynierii Ruchu Morsiego Szczecin, ul. Wały Chrobrego 1 2, [email protected] Key words: ship s simulator, DP systems, Kalman filtering, systems modelling Abstract The paper presents modelling principles of DP systems integrated into the modernized full mission ship simulator of Kongsberg Polaris type at Maritime University of Szczecin. Comparisons to real systems and research possibilities are given. Basing on the effects and conclusions obtained from scientific-research wors performed by marine traffic engineering staff until now, the advantages of modernization of full mission simulator have been shown. Słowa luczowe: symulator statu, systemy DP, filtracja Kalmana, modelowanie systemów Abstrat W artyule przedstawiono modele systemów dynamicznego pozycjonowania (DP) w wielozadaniowym symulatorze statu typu Kongsberg Polaris w Aademii Morsiej w Szczecinie. Zaprezentowano porównania z rzeczywistymi systemami i możliwości badawcze. a podstawie rezultatów dotychczasowych prac nauowo-badawczych realizowanych w Instytucie Inżynierii Ruchu Morsiego AM w Szczecinie przedstawiono zalety modernizacji wielozadaniowego symulatora manewrowo-nawigacyjnego statu. Introduction The Maritime University of Szczecin started the project of the avigational Technologies Centre (TC) comprising DP systems integration into Full Mission Ship Simulator and building of research laboratories with ship s integrated bridge systems and networ and mobile technologies of navigation data transfer. The TC project is co-financed from U funds in the Innovative conomy Operational Programme (IOP POIG). The realistic hardware and open software environment of the Full Mission Simulator give new possibilities of ship hydrodynamics and DP systems modelling and human factor analysis including: visual evaluation in manoeuvring and close approach, platform support, berthing and unberthing; realistic tandem loading and offshore operations; ship handling in narrow waters, i.e. cruise liners approach to passenger terminals and operation in small harbours and narrow channels; emergency manoeuvre to avoid collision etc.; manoeuvring safety analysis. DP systems at full mission ship simulator Hardware and software of a DP Class 2 System integrated into Full Mission Kongsberg Polaris Simulator for Maritime University of Szczecin were specified in compliance or exceeding the regulations set forward in: STCW 95, IMO Resolution MSC / Circ. 645, IMO Resolution MSC / Circ. 738 ref. IMCA M Scientific Journals 20(92)

2 Models of DP systems in full mission ship simulator Fig. 1. Full Mission Ship Simulator with DP systems Rys. 1. Wielozadaniowy symulator statu z systemami DP The open structure of modelled vessels allows for hydrodynamic tuning, thrusters and rudders allocation research essential in DP systems. Generally a seagoing vessel is subjected to forces from wind, waves and currents as well as from forces generated by the propulsion system. The vessel s response to these forces, i.e. its changes in position, heading and speed, is measured by the position-reference systems, the gyrocompass and the vertical reference sensors. Wind speed and direction are measured by the wind sensors. The DP system calculates the deviation between the measured (actual) position of the vessel and the required position, and then calculates the forces that the thrusters must produce in order to mae the deviation as small as possible. In addition, the system calculates the forces of wind, wave and water current which act upon the vessel and the thrust required to counteract them. The system controls the vessel s motion in three horizontal degrees of freedom surge, sway and yaw. The DP system is designed to eep the vessel within specified position and heading limits, and to minimise fuel consumption and wear and tear on the propulsion equipment. In addition, the DP system tolerates transient errors in the measurement systems and acts appropriately if an error occurs in the propulsion units. Figure 2 presents bloc diagram of DP system or DP simulator. The ernel of this system is the vessel model which hydrodynamics are actually supplemented by extended Kalman filter algorithm similar to the one presented in [1]. The algorithm calculates values of vessel s state vector (position, heading and motion) by measurements filtration and then it changes resulting force demand thrusters allocation to meet position, heading and motion settings. Kalman filtering A discrete random dynamic system is described by two equations in the Kalman filter: state equation (structural model of the process): x A x w 1 1 (1) measurement equation (measurement model): z H x v (2) where: x n th dimension state vector, w r th dimension state disturbance vector, z m th dimension measurement vector, v p th dimension state disturbance vector (measurement noise), A n n dimension transition matrix, H m n dimension measurement matrix, r n, p m. Zeszyty auowe 20(92) 147

3 Paweł Zalewsi Fig. 2. Bloc diagram of DP system / simulator based on [2] Rys. 2. Schemat bloowy systemu / symulatora DP na podstawie [2] Besides, it is assumed for disturbance vectors w and v that they are Gaussian noise of normal distribution, of zero mean vector and are mutually not correlated. The state equation describes the trend of the vector concerned, and the measurement model gives the functional dependence of the 148 Scientific Journals 20(92)

4 Models of DP systems in full mission ship simulator measurement on this vector. The solution to the equation system (1), (2), taing into consideration the limitations imposed on disturbance vectors, is in the Kalman filter. The estimation of the state vector in the filter can be presented by the equations below: state vector forecast: where: xˆ n x ˆ A x (3) ˆ1 forecast or a-priori estimated n value of the state vector at -moment, xˆ a-posteriori estimated value of the state vector, covariance value of the forecast of state vector: P A P A Q T 1 (4) where: Q is the matrix of the covariance of the state disturbance (of vector w), index T means matrix transposing, filter amplification matrix: T H P H R 1 T K P H (5) where R is the covariance matrix of measurement disturbance (of vector v), estimate of the state vector from filtration after maing measurement z : xˆ xˆ K z H xˆ (6) covariance matrix of the estimated state vector: P P I K H (7) where I is the identity matrix. In DP systems controlling vessel s position with fixed heading in two dimensions generally the following values are to be estimated: position coordinates (ϕ, λ), projections of the speed vector in relation to the bottom onto the meridian and the parallel (V, V ), acceleration vector projections onto the meridian and the parallel (a, a ) and the projections of acceleration vector derivatives in relation to the bottom onto the meridian and the parallel (a, a ). In this case the state vector will have the following elements: x T ',, V, V, a, a, a ', a (8) The measured values will be: position coordinates of the positioning system used (ϕ PS, λ PS ), speed components in relation to the meridian and the parallel from DR navigation performed by the positioning system used (position changes derivatives V, V ), acceleration components in relation to the meridian and the parallel from an inertial transformer (a, a ). So the measurement vector will have the following elements: PS PS T z,, V, V, a, a (9) The matrixes in equations (1) (7) containing the above mentioned elements are build similarly to ones presented in [1]. Some assumptions lie values of variance and covariance for particular measurements have to be done, for instance: DGPS system σ ϕ = 1.0 m; σ λ = 1.0 m; coordinates not correlated; speed components σ V = 0.1 m/s; acceleration components σ a = 0.01 m/s 2. Instructor role The instructor station can access all exercise and environmental conditions, introduce failures and situations where the operator must tae corrective actions [3]. The instructor can initiate loss of thrusters and generators and create noise in sensor readings and position reference systems. The instructor has the same range of information in feedbac from the DP operators. Faults and errors introduced, will force the trainee to e.g. find another thrusters allocation, start emergency generators and other systems, or selecting another sensor or position reference system. A full set of sensor systems, fully interfaced to the DP system, are available with instructor controlled faults, noise and interference. Fig. 3. Instructor station at Full Mission Ship Simulator with DP systems Rys. 3. Stanowiso instrutorsie w wielozadaniowym symulatorze statu z systemami DP Sensors The following sensors are simulated: gyrocompass, wind sensors, Vertical Reference Sensors, speed sensor (log). Zeszyty auowe 20(92) 149

5 Paweł Zalewsi The Gyro sheet at instructor station [3] allows for monitoring of the Gyro compasses and for controlling and monitoring the Gyro correction (due to latitude and speed) panel on the active Ownship bridge. The Air sheet at instructor station allows for monitoring of the wind parameters and for controlling of the wind sensors (wind direction and speed uniform with gusts or from chart database with shadows emulated). The wind sensor location can be changed inside ship model (see Fig. 4). WIDSSORLOCATIO sound velocity ray-trace calculation with displaying of deflection based on velocity profile input, SSBL positioning of transponders, telemetry communications with transponders, calibration of LBL arrays, examining the expected accuracy when positioning in different arrays, data output for testing telegram interfaces to external computers (standard HiPAP / HPR telegrams). Windsensors located WIDSSORSLOCATD in IPOSITIOS1AD2 positions 1 and 2 will WILGIVIPUT give input DISTORTDBY distorted TURBULC by FROM turbulence from STRUCTUR structure LOCATIOS3AD4 locations ARBTRBUTIPUT 3 and 4 are better MAYDTOBSCALD but DOWDUTOALTITUD input may need XAGRATIGTH to be scaled down WIDSTRGTH due to altitude exaggerating the wind strength Fig. 4. Advantages and disadvantages of wind sensor location Rys. 4. Zalety i wady rozmieszczenia czujniów przepływu powietrza (anemometrów) The Vertical Reference Sensors comprising VRS, VRU and MRU are used for measuring pitch, roll and heave of real vessel. In the ship simulator environment that ind of data can be obtained from ship hydrodynamical model with emulation of any warnings, alarms and messages as in real sensors. The Waves and Sea sheets at instructor station allow for generation and controlling of external water forces. The speed sensor can be either Doppler or electromagnetic type. Acoustic Position Reference The Acoustic Positioning Operator System (APOS) is operated as normal Kongsberg HiPAP / HPR system where a simulator replaces transceiver and the transponders [3]. A typical Long Base Line (LBL) and Super-Short Base Line (SSBL) operator presentation is shown in the figure 4. The vessel is positioned in the LBL array with the locations 1, 2, 3 and 4, and the SSBL transponder B27 is positioned relative to the vessel. The APOS has following features: defined with one HiPAP and one HPR 400 receiver, Fig. 5. LBL and SSBL operator presentation Rys. 5. Interfejs operatora systemu APOS w onfiguracji LBL i SSBL Artemis Position Reference orth FIX orth Azimuth Distance orth orth Fig. 6. Parameters measured and calculated by Artemis Rys. 6. Prametry mierzone i wyliczane przez system Artemis The Artemis panel allows for microwave positioning of the range bearing type. It outputs range and bearing from the fixed antenna to the ship s antenna. Lost of signal, DIP zones and surface reflections impact the simulated measurement error. MOB Azimuth Relative Mobile Antenna Relative Mobile Antenna Bearing Azimuth Heading Heading = Azimuth Relative Mobile Antenna Bearing Heading Heading = Azimuth Relative Mobile Antenna Bearing 150 Scientific Journals 20(92)

6 Models of DP systems in full mission ship simulator Satellite Position Reference The Satellite Positioning Systems are operated via typical receiver interfaces or DP consoles as other position reference systems. The GPS has simulated default accuracy of 15 m (95%), DGPS of 3.3 m (95%), D(GPS + GLOASS) of 0.7 m (95%) and GALILO of 4.0 m (95%). The accuracy of satellite position reference can be changed via instructor station. Radius Position Reference The Radius panel allows for similar radar positioning as Artemis. Because transponders have no moving parts their angle of operation is limited (max. 90) and depends on transponder location on the vessel (changeable in the ship model). Fanbeam Position Reference The Fanbeam panel allows for laser based positioning. The probability of the system locing on other reflecting objects and blocing of the signal is determined at the instructor station. The range depends on the simulated weather. It outputs ranges and bearings to the reflecting prisms (their positions defined inside models used in the scenario). Thrusters Thruster and propulsion systems are ship-model dependent and can be chosen among: main propellers and rudders: single or twin screw, with or without nozzle, variable pitch and fixed RPM, fixed pitch and variable RPM, variable pitch and RPM, single or twin rudder, rudder active or inactive; azimuth thrusters; tunnel thrusters; water jet; voith-schneider thruster. The Fail-safe mode for controllable pitch propellers in DP vessels is the zero pitch point, however several possible failure modes can cause pitch freeze (fail-as-set), full pitch, failure to zero pitch, failure to any pitch setting. DP integrated consoles Dual redundant DP Operator Consoles (K-Pos Class 2) that will be installed at Maritime University of Szczecin Full Mission Ship Simulator allow for manual joystic operation and automatic station-eeping including: position and heading change, Autopilot, Auto Trac. Various system faults can be simulated via instructor station. Figure 7 presents bloc diagram of DP system integration into ship simulator, Wind VRS Gyro xternal force Pos. ref. Power Other sensors Thursterfeedbac Thurstersetpoint Fig. 7. Bloc diagram of DP Class 2 System integrated into ship simulator system [2] Rys. 7. Schemat bloowy systemu DP lasy 2 zintegrowanego z symulatorem wielozadaniowym statu [2] Zeszyty auowe 20(92) 151

7 Paweł Zalewsi abbreviations stand for: OS operator station, DPC-2 dynamic positioning controller with dual controllers (class required redundancy). Conclusions DP models implemented into Kongsberg-Polaris Full Mission Simulator enable not only advanced training in all aspects of ship-handling and navigation but also allow for in-depth scientific studies because of their customizable open structure. By following conclusions the systems presented in chapter 2 for DP models utilization in research can be quite straightforward: 1. DP capability analysis for various vessels and external conditions (weather conditions) can be performed either in the on-line or off-line mode. Figure 8 shows, by means of a schematic radarplot outline, an example of capability plot presenting operational margins with respect to the environmental conditions (wind speed vector) and possible system failures. Symbols at the top mean from the left clocwise: waves direction, wind direction, sea-current direction, BL direction for detailed readout. 2. Studies in ship motion modelling, identification of ship motion and ship s steering conducted on very realistic hardware can lead to more accurate ship models, modification of their parameters and equations. 3. Data analysis leading to autonomous models of trac steering as presented in [4] can be developed further. 4. ew software interfaces based on human-factor analysis can be designed with methodology similar to PS [5]. 5. Human factor on contemporary ship bridge with navigation equipment customised to any ship and / or emergency scenario can be thoroughly analysed. 6. Finally the navigation safety analysis of offshore DP vessels can be performed including the complex ris criterion [5] (Fig. 9). Fig. 9. Manoeuvring area obtained during navigation safety analysis Rys. 9. Obszar manewrowy uzysany w wyniu analizy bezpieczeństwa nawigacji Fig. 8. xample of DP capability plot for various wind speeds and directions Rys. 8. Przyładowy wyres ograniczeń utrzymania statu na pozycji systemem DP dla różnych prędości wiatru References 1. BAACHOWICZ A.: Variants of Structural and Mesurement Models of Integrated avigational Systems. Secja awigacji Komitetu Geodezji PA, Polsie Forum awigacyjne, Gdynia 2001, Annual of avigation 2001, 3, Operator and Maintenance Manual Kongsberg K-Pos DP, Basic and Advanced Trainer Szczecin. Doc. no.: , Kongsberg Maritime AS, Horten Technical Manual Section 5a Instructor s Manual POLARIS Ship s Bridge Simulator. Doc. no.: SO-0612-O, Kongsberg Maritime AS, Horten ZALWSKI P.: Fuzzy Fast Time Simulation Model of Ship s Manoeuvring. In 8 th International Symposium on Marine avigation and Safety of Sea Transportation Transav 2009, Gdynia, A.A. Balema Publishers, Rotterdam, etherlands GUCMA S., GUCMA L., ZALWSKI P.: Symulacyjne metody badań w inżynierii ruchu morsiego. Wyd. auowe AM, Szczecin Scientific Journals 20(92)