application experience of component modeling in transas

ISSN 0005-1179, Automation and Remote Control, 2016, Vol. 77, No. 6, pp. 1106–1114. c© Pleiades Publishing, Ltd., 2016.Original Russian Text c© S.V. Tarasov, 2013, published in Avtomatizatsiya v Promyshlennosti, 2013, No. 7, pp. 42–46.

AUTOMATION IN INDUSTRY

Application Experience of Component Modeling

in Transas Group’s Training System Development

for Cargo-Ballast and Technological Operations

S. V. Tarasov

TRANSAS Technologies (ZAO), St. Petersburg, Russiae-mail: [email protected]

Received April 11, 2013

Abstract—The paper examines the experience of mathematical model development for the Tech-Sim/LCHS 5000 Series training systems from Transas Group (Russia). It overviews the subjectarea and the problems solved during the training simulator development. The application-specific requirements to model fidelity and software implementation are analyzed. The object-oriented approach applied, its implementation using Rand Model Designer, and the features ofstandard component library are described. The actions required to enable the operation of themodels developed in real-time simulation are discussed.

DOI: 10.1134/S0005117916060151

1. LIQUID CARGO HANDLING OPERATIONS

Problems of protection of human life and safety of property at the sea, and also protection ofthe marine environment demand presence from crews of ship of sufficient experience, skills andqualification. Relevant requirements are fixed in the International Convention on Standards ofTraining, Certification and Watchkeeping for Seafarers (STCW 95). One of means of ensuringof these requirements is use of the modern simulators intended for training and an assessment ofcompetence of seamen. In particular, at training of specialists, responsible for technology of loadingon tankers, simulators of liquid cargo handling operations are used (LCHS—Liquid Cargo HandlingSimulators).

Simulators of this type serve for studying of the design of the tanker, structure of its technicalmeans and systems, and also provide training in control of systems and units, to the correctperformance of technological operations, skills of adoption of competent decisions in normal andemergency operational conditions.

For the solution of the specified tasks any liquid cargo simulator has to realistic reproduce alltechnological operations included into standard courses of International Maritime Organization(IMO) for the corresponding types of ship, such as oil tankers [1] and gas tankers [2].

For oil tankers and chemical tankers typical operations are drainage, an inertization, loading(or discharging) cargo tanks with simultaneous ballasting of the ship, cleaning, a wash of cargotanks, etc. The production cycle of gas tankers in addition includes such operations as gassing upand cooling down of cargo tanks and pipelines. Besides, it is necessary to consider a number oftypical emergencies, including various leakages, breakages of the equipment and the fires.

Thus, the simulator has to provide possibility of work with various ship systems involved inthe specified operations: ballast, cargo, cleaning of tanks, washes of tanks, heating of freight,inert gases, fire extinguishing, automatic measurement, oil discharge and monitoring equipment,detection of leak of gas, alarm system, etc. Thus the simulators intended for training of specialists

1106

APPLICATION EXPERIENCE OF COMPONENT MODELING 1107

Fig. 1. One of the screens of the LNG Membrane Tanker simulator reproducing a computer control andmonitoring system of the gas tanker.

for the certain the project or ships class, have to reproduce in details structure and a configurationof systems of the ship prototype.

Let us consider experience of development of mathematical models for family of simulators ofthe cargo ballast and technological operations TechSim/LCHS 5000 developed by Transas company(http://www.transas.com/products/LCHS5000).

The user interface of of this family of simulators imitates a multilevel control system of theequipment of the real ship by means of the following kinds of screens:

—the screens reproducing the control panels located in the cargo control room, and also on localposts;

—the screens reproducing the user interface of the computer control system and monitoringestablished on the ship prototype (Fig. 1);

—screens of schematic diagrams of ship systems with possibility of the animated display of thecurrent processes;

—three-dimensional visualization with possibility of control of the equipment on the deck of theship.

2. REQUIREMENTS TO MATHEMATICAL MODELS

The key role in creation of the simulator of cargo ballast operations is played by development ofthe mathematical model allowing to describe adequately behavior of all controlled parameters ofship systems in interrelation with each other at all stages of a full production cycle of functioningof the tanker.

AUTOMATION AND REMOTE CONTROL Vol. 77 No. 6 2016

1108 TARASOV

Depth of mathematical modeling of physical processes minimum necessary for the simulatoris defined proceeding from the analysis of technical and operational documentation of tankers,requirements of the standard courses of IMO [1, 2] and training programs of the oil and gascompanies.

The majority of the ship systems which are a part of the cargo ballast simulator representbranched pipelines. The processes happening in such systems under normal operational conditionsallow modeling in the form of a hydraulic network.

Thus currents in pipes are described by a one-dimensional quasi-stationary stream of viscous,incompressible, two-phase multicomponent fluid. Parameters of a stream change in time due tochanges in boundary elements of a hydraulic network (tanks and reservoirs), change of powerparameters of components of a network (pumps and compressors), and also the phenomena ofphase transition and heat exchange of the environment in pipes with walls.

For tanks and reservoirs it is necessary to model mass- and heat transfer, component structure,phase transition, and also vertical convection within liquid and gaseous environments.

Thus, dynamics of the modelled systems is described by systems of the nonlinear differential-algebraic equations of variable structure with a large number of the equations.

At the same time the scope of mathematical model in simulators causes the following numberof requirements to program realization of model:

—the mathematical model has to reproduce authentically the physical processes going on simul-taneously in various ship systems in interaction to environment. Thus interactive communicationof the user with all equipment which is a part of the modelled systems, that is hundreds of valvesand pipes and dozens more difficult specialized devices has to be provided;

—productivity of mathematical model has to be sufficient for work on the standard personalcomputer as in the mode of the real, and accelerated time. And duration of typical operations isthose, that the possibility of acceleration of time is necessary for maintenance of acceptable timelimits of training in 25 times;

—the architecture of mathematical model has to be easily scalable and allow modification ofstructure of systems and a configuration of each system at the minimum labor costs.

In view of the specified requirements, it is possible to draw a conclusion that forming and thenumerical solution of similar systems is rather complex problem and demands special approach.

3. TECHNOLOGY OF COMPONENT MODELING

Approach to creation of model is defined by way of its decomposition on components. For theconsidered systems the approaches based on decomposition on the modelled phenomena (horizontalfragmentation) and on the modelled devices (vertical fragmentation) are possible. Set of devicesand structure of a hydraulic network, as a rule, don’t coincide both for systems of different functionof one ship, and for systems of similar purpose of various ships. At the same time set of themodelled phenomena for each type of devices in various systems, as a rule, remains same. Thereforefor development of family of TechSim/LCHS 5000 simulators component approach with verticalfragmentation was chosen.

Component modeling assumes that the description of the modelled system reflecting its naturalstructure is formed from ready components, and the cumulative mathematical model is formed bythe executing system automatically. Modern component modeling is object-oriented [3].

Within this approach the object-oriented analysis of applied area is carried out. On the basis ofthis analysis standard classes and the relations of inheritance between them that allows to createlibrary of standard components are allocated.



Fig. 2. Block diagram of model of cargo system of the gas tanker.

Fig. 3. The block diagram of the CargoTank class which is a fragment of cargo system of the gas tanker.


1110 TARASOV

As a development tool the environment of modeling Rand Model Designer which supports thefollowing opportunities was chosen (http://www.rand-service.com/ru/):

—object-oriented modeling within an UML language subset;

—physical modeling within a Modelica language subset;

—the types of data determined by the user.

During development of simulators the Rand Model Designer environment is applied both tocreation of library of standard components, and to development of models of concrete systems ofthe simulator.

The model of each system is formed by the developer in the form of the block diagram consistingof the objects connected by links. The environment of modeling assumes use of the embedded blockdiagrams that allows to reduce labor costs by drawing up models.

As an example we will consider cargo system of the gas tanker from the LNG Membrane Tankersimulator. The concept scheme of this system includes five cargo tanks, each of which is equippedwith an identical set of cargo pumps and valves. The block diagram of the model of this system(Fig. 2) contains five copies of the Cargo Tank class representing the block diagram from the tank,its pumps and valves (Fig. 3).

The library of standard components [5] created in the course of development of family of Tech-Sim/LCHS 5000 simulators of Transas company contains some tens various classes of the devicesinvolved in ship systems including:

—vessels for liquid and gas (tanks, air reservoirs);

—elements of pipelines (pipes and fittings);

—pumps and compressors;

—heattechnical devices (heat exchangers, evaporators);

—actuation devices (regulators and logical schemes).

Let us consider architecture of library components on the example of the standard Valve classrepresenting valve model. Functionality of a class is described by means of the behavior chart [4]reflecting possible object states, and transitions between them.

So, the card of behavior of the Valve class (Fig. 4) has the states corresponding to open(state opened), and closed (state closed) valve. In turn the condition state opened has the em-bedded behavior chart (Fig. 5) which states correspond to various directions of a current of liquid,and switch depending on stream size via the valve. The behavior of the valve in each of these statesis described by the separate local continuous class containing the equations concerning stream pa-rameters on a valve input/outut:

—stream hydraulics equations;

—heattransfer taking into account heat exchange with walls;

—phase state of the environment;

—concentration of components of the medium.

The library has the hierarchical structure constructed on the basis of mechanisms of inheritanceand an inclusion that facilitates support and addition of new classes.

In particular, the standard Valve class, is the successor of the standard Pipe class representingpipe model. Thus functionality of the valve on-state is inherited from the Pipe class (the fragmentof the behavior chart of the Valve class inherited from the Pipe class is highlighted on Fig. 4), andfunctionality of the valve in the closed state is redefined in the Valve class.

The class of the remotely-controlled valve ValveRemote (Fig. 6) which consists of standard objectof Valve realizing functionality of the valve, and Controller object modeling the mechanical drivecan be an example of a compound standard class.



Fig. 4. The behavior chart of the Valve class from library of standard components.

Fig. 5. The imbedded behavior chart of a state of state opened of the standard class Valve.

Fig. 6. The block diagram of the ValveRemote class from library of standard components.


1112 TARASOV

4. WORK OF MATHEMATICAL MODELAS A COMPONENT OF OF THE SIMULATOR

The program code of model (“the executable model”), in the form of dynamic libraries, is gen-erated according to its description in modeling language by means of the Rand Model Designer [5]environment. The executable model includes all components of model (including implicit objects,such as relations), the executing system and library of numerical methods.

In simulator operating time the executing system traces switchings of conditions of all objectsaccording to their behavior chart, automatically forms of the equations of active conditions ofobjects and the equations of relations between objects cumulative system of the equations of modeland carries out its numerical solution. The automatic generation of a program code allowing toexclude programming errors at a stage at creation of models of systems at the same time causesincreased requirements to quality of standard library classes, and also to reliability and speed ofthe executing system.

As showed experiment, the requirement of work of automatically generated models in real timeappeared the most critical for simulator applications. In the cargo ballast simulator updating ofthe controlled variable of all modelled systems has to happen to a step about 0.5 s in real timeowing to what time of calculation of one step for each system shouldn’t exceed the tenth fractionsof a second.

For illustration in the table are given the measurements of parameters of model of cargo systemof the gas tanker from structure of the LNG Membrane Tanker simulator when performing standardoperations in the simulator.

Apparently from the table, the cumulative system of the equations of model before transfor-mations contains tens of thousands of expressions that excludes possibility of its direct numericalsolution in real time.

The executing system carries out sorting of the equations, allocating algebraic cycles and se-quences of formulas, and also revealing opportunities for automatic transformation of system, forexample:

—some kinds of the algebraic equations are resolved symbolically and will be transformed toformulas;

—the chains of the equations equating some variables to each other (so-called “equivalences”),are removed from system, thus instead of each group of equivalent variables the only variable issubstituted.

As a result of automatic transformations, the quantity of the equations demanding the numericalsolution several times decreases. It allows to reduce operating time of a numerical method up tothe acceptable sizes, however generates additional expenses of time for the automatic analysis andtransformation of system. For reduction of these expenses, the executing system can use additional

Parameters of actions of mathematical model of cargo system of the gas tanker

Modelled technological operation Cooling downof cargo tanks

Loadingof cargo tanks

Number of the valves opened when performing operation, units 34 43Total number of expressions in cumulative system of the equations, units 14 512 14 790Nonlinear algebraic equations, units 309 318Linear algebraic equations, units 981 1504Formulas, units 652 840“Equivalences,” units 12 570 12 968Time of calculation of one step of model time, s 0.125 0.144



information on the equations which has to be brought by the developer of model at a stage ofcreation of library components:

—the explicit indication of the algebraic equations which are obviously the linear;

—the explicit indication of division of system of the equations into the “blocks” solved consis-tently;

—the explicit indication of variables which can’t obviously be unknown.

The listed measures allowed to achieve the demanded speed that is confirmed by data of thetable.

5. PRACTICAL APPLICATION OF TECHNOLOGY

The considered technology of component modeling successfully is applied in the company Transaswhen developing mathematical models to family of simulators of the cargo ballast and technologicaloperations TechSim/LCHS 5000 (http://www.transas.com/products/LCHS5000).

By the present moment simulators for the following models of ships are released:

—Chemical Tanker—the chemical tanker of the first class;

—Product Tanker—product carrier ship;

—LNG Membrane Tanker—the gas tanker of membrane type for transportation of the liquefiednatural gas (Fig. 7);

—LNG Regasification Terminal—gas terminal.

In development there are new simulators of this family:

—LCC Tanker—oil tanker of the Aframax class;

—LPG Tanker—the gas tanker for transportation of the liquefied petroleum gas.

Fig. 7. The simulator of the gas tanker LNG Membrane Tanker of the family TechSim/LCHS 5000 at the stand.


1114 TARASOV

REFERENCES

1. IMO Model Course 2.06: Oil Tanker Cargo and Ballast Handling Simulator, Portsmouth: IMO, 2002.

2. IMO Model Course 1.36: Liquefied Natural Gas (LNG) Tanker Cargo and Ballast Handling Simulator,London: IMO, 2007.

3. Kolesov, Y.B. and Senichenkov, Y.B., Modelirovanie sistem. Ob”ektno-orientirovannyi podkhod (Model-ing of Systems. Object-oriented Approach), St. Petersburg: BHV, 2006.

4. Kolesov, Y.B. and Senichenkov, Y.B., Modelirovanie sistem. Dinamicheskie i gibridnye sistemy (Mod-eling of Systems. Dynamic and hybrid systems), St. Petersburg: BHV, 2006.

5. Tarasov, S.V., Kiptily, D.V., and Lebedev, D.V., An Object-Oriented Approach to the Developmentof Liquid Cargo Handling Simulators in TRANSAS, in Proc. 7th Vienna Int. Conf. on MathematicalModelling, IFAC-PapersOnLine, Mathematical Modeling, Vienna, 2012, vol. 7, part 1, pp. 369–373.


application experience of component modeling in transas

Documents