Proceedings of the Twenty-ninth (2019) International Ocean and Polar Engineering Conference www.isope.

org
Honolulu, Hawaii, USA, June 16-21, 2019
Copyright © 2019 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1 880653 85-2; ISSN 1098-6189

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Virtual Reality Simulations for Dynamic Positioning Floatover Installation
Alan M. Wang(1), Rongqi Chen (1), Min He(1), Xiaohuan Zhu (1), Jingkuo Xu(1), Wim van 't Padje (2)
(1)
Offshore Oil Engineering Co., Ltd.
Tianjin, China
(2)
Research and Development Department, STC BV
Rotterdam, The Netherlands

reality environment of South China Sea. There are 23 full mission

ABSTRACT bridge simulations with 10 key personnel participants, performed at the
STC Simulation Facility in Rotterdam. These simulation tests are
This paper presents a comprehensive description of this innovative designed to verify the DP operation procedures and to define the
training program and its successful simulation application, including environmental criteria, as well as to train and familiarize the key
virtual reality (VR) simulations of offshore field, numerical and visual personnel involved, especially DP operators, with the floatover
modeling of met-ocean environment and DP2 floatover vessel, and operation procedures. The objective of this training program is to
performance of key personnel when executing floatover operations. provide an understanding and support in managing and organizing the
The VR simulations realistically and accurately replicate the floatover resources on the simulation bridge efficiently and effectively in order to
operations against set scenarios in a VR environment, thus identifying reduce accident probabilities and to reach the operational goals for the
any deficiencies in key installation personnel, communication skill, challenging floatover operation.
execution plan, operation procedures, and floatover hardware systems.
The VR simulations also serve to provide a team building exercise This innovative simulation program encompasses all the scenarios of
where everyone has a chance to meet and work together. The various floatover operations, including a series of positioning trials,
simulation scenarios are tested under normal/anticipated environmental moving to standoff position, approaching to pre-installed jacket,
conditions and extreme environmental conditions, as well as a number docking into jacket slot, undocking operation, etc. The simulation
of stressful conditions, such as thruster failure, adverse internal wave training excludes the mating operation mainly due to the highly
current, power blackout, etc. The simulation tests last five days and nonlinear effect of leg mating units (LMU) and deck support units
concluded with debriefing sessions, conclusions, recommendations, and (DSU) during load transfer, which requires an extremely high
lessons learned, as being an important basis for its success in the computing power to simulate the real-time responses of complicated
challenging DP floatover operation. contact mechanism. A high-precision millimeter-level local reference
system, including a microwave positioning system RadaScan and a
KEY WORDS: Virtual Reality; Virtual Simulation; Dynamic laser radar system CyScan, is emulated as being installed on the vessel
Positioning; Floatover Installation. stern deck to avoid any blockage of the topsides. The outcome of the
high-precision local reference system is used as input for the DP
NOMENCLATURE control system. A dynamic positioning system IMTECH DP 4500 is
integrated as a DP mockup model in its simulations. The mockup
BRM = Bridge Resource Management model of the DP control system has been tested and validated by DP
COOEC = Offshore Oil Engineering Co., Ltd. specialists against the hydrodynamic models developed in the full
DPO = Dynamic Positioning Officer mission bridge simulator Diomedea approved by DNV GL.
FMB = Full Mission Bridge
HYSY = Hai Yang Shi You This paper presents a comprehensive description of this innovative
HZ25-8 = Hui Zhou 25-8 training program and its successful simulation application, including
ECDIS = Electronic Chart Display and Information System VR simulations of offshore field, numerical and visual modeling of
VR = Virtual Reality met-ocean environment and DP2 floatover vessel, and performance of
key personnel when executing floatover operations. The VR
INTRODUCTION simulations realistically and accurately replicate the floatover
operations against setting scenarios in a VR environment, thus
A virtual reality (VR) simulation program has been developed to identifying any deficiencies in key installation personnel,
simulate a floatover installation of 13,000Te integrated topsides with a communication skill, execution plan, operation procedures, and
dynamic positioning (DP2) X-Class semisubmersible vessel in a virtual floatover hardware systems. The VR simulations also serve to provide a

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team building exercise where everyone has a chance to meet and work Simulation Procedure
together. The simulation scenarios are tested under normal/anticipated
environmental conditions and extreme environmental conditions, as The VR simulations utilized the following procedure in order to set up
well as a number of stressful conditions, such as thruster failure, realistic simulations that lead to the best results for the given objectives:
adverse internal wave current, power blackout, etc. The simulation tests  Collection of required data.
last five days and concluded with debriefing sessions, conclusions,  Creation of simulation databases and models.
recommendations, and lessons learned, as being an important basis for  Preparation of scenarios in consultation with Client.
its success in the challenging DP floatover operation. Fig. 1 shows that  Preparation of assessment checklist.
the DP2 X Class semisubmersible vessel HYSY278 was selected for  Preparation of the Evaluation Form (Questionnaire).
the challenging floatover installation of 13,000Te integrated topsides at  Internal and external validation of simulation database & models.

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a water depth of 100 meters for the Hui Zhou 25-8 Drilling and  Testing of proposed simulations involving new database, new
Production Platform in South China Sea. Jin et al. (2018) described models and existing models, simulator arrangement of FMB, new
details of the DP floatover technology and its successful application. software, etc.
 Full team assembled and kick-off meeting and system
familiarization.
 Daily simulation execution including briefing meeting, simulation
runs, questionnaire, debriefing meeting, lessons learned, planning
for next day, closing meeting at end of each simulation day.
 Real-time Training with special attention during debriefing for
BRM themes such as Shared Mental Model, Challenge and
Response, Situational Awareness, Communication, etc.
 Last day of simulations to reach preliminary conclusions &
recommendations, lessons learned, closing simulations.
 Final reporting

FMB Simulators & Training Setup

A Full Mission Bridge Simulation (FMB) is a ship simulator with a

ship’s bridge where a bridge management team can carry out all
possible missions that should be carried out on board of that ship under
Fig. 1: Successful DP Floatover Installation of 13,000Te HZ25-8 DPP all kinds of different conditions including emergencies. A single FMB
Topsides in Challenging Environment of South China Sea simulator consists of the followings:
 A navigation bridge equipped with control equipment for steering,
VR SIMULATION METHODOLOGY engine settings, bow/stern thruster settings, radars, ECDIS,
communication, binoculars, (engine) sound generators, etc.;
The VR simulations include preparation and execution phases which  One or more computers with simulation program software;
are listed in Tables 1a and 1b, respectively.  One or more computers for projection of visuals on the screen(s);
 A projection screen area upon which the outer world of the ship’s
Table 1a. VR Simulation Preparations bridge is projected.
Creation of new database & new models
Fig. 2 shows the Bridge Team in charge of DP operation, docking and
Internal validation of new database & new models undocking during simulations, IMTECH DP 4500 Panel with DPO
External validation done by Client (Dynamic Positioning Officer) and his assistant who station at the
bridge and communicate with DP observers at stern, simulation
Testing of proposed simulations involving operators, and exercise coordinator, etc. The bridge team virtually
 New database, new models and pre-existing models maneuvers the DP vessel in a virtual-reality environment including
 Simulator arrangement of FMB4, Classroom 4 water depth, wind, waves, current, tide, and so on. Advantage of real
 New software, e.g. models of fendering system, winches, etc. time simulations is that human factors in the simulations is not effected
Notice of Readiness upon testing of system by any difference in time scale, that is, in real time simulations,
everything happens in real time, therefore one second of simulation
Table 1b. VR Simulation Execution time is exactly equal to one second in real time. The simulation results
regarding human behavior are directly applicable to the same situation
Full team assembled, opening meeting and system familiarization in real life, e.g. situational awareness, distraction, concentration span,
Daily simulation execution confusion, breakdown in communication, improper conn/lookout,
 Briefing meeting departure from original project plan, violation of rules/regulations,
 Simulation Run operation procedures, reaction time, fatigue, etc.
 Questionnaire
 Debriefing meeting Depending on the demands placed on the underlying simulation
 At end of each simulation day: Lessons learned, Planning for program, a FMB simulator may require one or more computers to
next day, Closing meeting accommodate the necessary software. The projection screen area upon
which the outer world of the ship’s bridge is projected determines the
Last day of simulations
type of simulator. Pinkster (2012) describes the FMB simulators in
 Preliminary Conclusions & Recommendations details and examples of the use of the FMB simulators in offshore
 Closing simulations operations. Wang et al. (2010) presented a good example of the virtual

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simulation for a VLCC class FPSO hookup and their various Simulation Layout
applications for the mating operation between the FPSO and the SYMS
(Soft Yoke Mooring System) in extremely shallow water. An STC exercise coordinator with years of offshore operation
experience as DPO was assigned to oversee the simulations and played
an active role in the debriefing process. Generally speaking, the
exercise coordinator moved between FMB4, the stern observers’
position, IOS4 and classroom 4 whenever this was deemed to be
necessary.

The debriefing process considered two main areas:

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 Skill, knowledge, procedures, safety margins, etc.
 Human Resources observations as experienced by the participants.

The outmost care has been taken to provide only objective observations.
The simulation set up can be viewed below:
 Instructor Station Views: Main Screens in Classroom 4, Visual
Database, GPS Positioning Survey Screen, Tug View, Aft Deck
View (8 CCTV Screens), Helideck View plus four CCTV Screens
 DPOs’ Bridge Views: Imtech DP Console, GPS Positioning Survey
Screen, Helideck View plus four CCTV Screens
 Stern Observers’ View: Aft Deck View with 8 CCTV Screens
Fig. 2: Bridge Team, IMTECH DP 4500 Panel with DPO Operator &
Assistant, Communication with Observer & Simulation Operator

For the DP floatover simulations, the following STC facilities were

used:
 Full Mission Bridge Simulator (FMB4) with a 240-degree stern
view from the bridge.
 One Instructor Operator Stations (IOS) for HYSY278 and soft lines
winch operation.
 Classroom 4 for debriefings, day conclusion meetings, and next day
planning meetings.
 During simulations, participants present in the Classroom 4 were
able to closely follow the actual simulation progress step by step as
this was projected on a large screen especially for this purpose.
 Three VHF radios were made available so the DPO (Dynamic
Positioning Officer) of the HYSY278 could speak to the IOS
operator or officer positioned on the stern (spotter). Communication
could be made at any time to simulate crew replies to distance off
object, make soft lines ready, tug communication, etc.
Fig. 4: Instructor Station (IOS4) with Operator and Exercise
Fig. 3 shows that during simulations participants present in Classroom Coordinator
4 were able to closely follow the actual simulation progress step by step
as this was projected on a large screen especially for this purpose.

Fig. 5: DP Observer/Spotter Positioned at the Stern of HYSY278

Fig. 4 shows Instructor Station View (IOS4) with Operator and

Exercise Coordinator. IOS4’s functions include:
Fig. 3: Classroom 4 for Debriefings, Day Conclusion Meetings, and  Start/Stop each simulation
Next Day Planning Meetings, etc.  Establish met-ocean data: wind/current/wave for each run
 Interactive Tug operated by IOS

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 HYSY278 Vessel Model with/without DPP Topsides  The wind input for the exercise provides gusts and at a realistic
 Two softline winch operation height in relation to the topsides height. The DP system allows for
 VHF radio contact with FMB4 higher gusts than programmed due to the imagined height of wind
gauge.
Fig. 5 shows Stern DP Observers’ View at aft deck with 8 CCTV  The wave direction is always in the same direction as the wind.
Screens. DP Observer/Spotter is positioned at the stern of HYSY278 to  To allow time for the DP system to stabilize many of the
obtain all the information concerning positioning including distance to simulations have been started and running for 10 to 20 minutes
go to various points of reference and skewing. before the DPO will take over. For recording and playback
purposes a notation of elapsed time has been made at the start
BRM Techniques condition for each exercise when the assessment will begin.

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 Jacket approach and move within jacket:
The literal meaning of Bridge Resource Management (BRM) is: 1) Vessel speed shall be maintained within 0.1-0.2 m/sec before
managing or organizing the resources on the bridge. This BRM training entering inside jacket. Note: DPO will aim at 0.01 m/sec
has the general objective to provide an understanding and support in when entering inside the jacket.
managing the resources efficiently and effectively in order to reduce 2) Heading within +/- 2° before entering jacket
error/accident probabilities and to reach the operational goals. 3) 5° max heading deviation during docking and undocking
4) Allowed 1 meter off-line before jacket entry
Human error is the most prominent cause of errors and failures in
offshore operations, such as, docking and undocking during floatover Debriefing Sessions
operations. Most of the accidents occur in such intensive offshore
activities, where it is at these times and in these places that the bridge Prior to each simulation, all the participants were briefed regarding the
personnel have the greatest workload. They must effectively use all the coming simulation exercise and their role therein. Directly after each
equipment and resources available and function as a team to handle the simulation the participants were each requested to separately fill in a
work required to complete offshore operations as safely and efficiently questionnaire where they could state their experiences and objective
as possible. opinions on the simulated phase of the DP floatover operations.
Directly thereafter followed the debriefing. Debriefing sessions were
BRM focusses attention to such items as Communication, Shared attended by all involved participants and any other relevant
Mental Model, Short Term Strategy, Situational Awareness, etc. It representatives. The debriefing session consisted of two main
considers how these elements affect not only the individual but also the components: Human Resource and Skill/Knowledge/Procedures. After
team. The work of planning, executing, and reviewing simulated each simulation the DPOs completed a short questionnaire to be used as
operations is designed to heighten the awareness of the participants to a reference for the debrief session. The debriefing sessions used shared
the job of safe operation and to the hazards presented to the floatover mental model, situational awareness, challenge and response, proper
vessel and its operation crew during those times of increased workload. communication procedures, etc., described below.

BRM error chain clues such as ambiguity, distraction, confusion, break Situational Awareness (SA): How well did the participant understand
in communication, improper procedure, departure from plan, violation what was happening around him? Was he familiar with the operation,
of rule and complacency, etc., together which, can lead to an did he have a shared mental model, did he fully appreciate the
occurrence. Use of communication message markers such as importance of his role in the operation and was he able to anticipate
information, question, answer, request, intention, warning, advice and upon upcoming events?
instruction, etc., are just one of the tools used to promote clear and
concise communication. Communication (C): Does closed-loop Communication exist? Were
instructions and reports clear? Was Standard Marine Communication
The use of a Shared Mental Model, Situational Awareness, Challenge Protocol (SMCP) utilized?
& Response, proper Communication procedures, etc., are amongst the
key issues of the utmost importance for successful marine operations. Challenge and Response (C&R): Does the proper Challenge and
These elements have been chosen to be used for all simulations. By Response environment exist between the DPO and any other? Does
introducing these concepts we will reduce the potential for human error each feel free to challenge the other, if challenged is the response
and thus significantly decrease the risks involved and increase the appropriate. Participants will be exposed to the idea of a challenge as
safety of the operation at hand. A number of the above mentioned BRM one which challenges a “concept” rather than the “person”.
techniques have been constantly brought to the attention of the
participants during the DP floatover simulation training and highlighted Shared Mental Model: All participants have the same mental idea or
as being an important basis for the success in the floatover operation. concept of what is or will happen, also what will be expected of them.

DP Floatover Operation Criteria Operational Deficiencies (OD): As seen by STC Offshore Specialist
Expert opinion.
For all the simulation runs the following operation criteria have been
discussed and agreed. If any of the parameters below are exceeded, The skill/knowledge/procedures section of the debriefing confined
they shall be items for discussions during the debrief sessions. itself to factual data which was accurately recorded during the
 At 1000m distance from jacket the vessel speed shall be maintained simulation and can be reviewed on the debriefing simulator. Areas of
within 0.5m/sec in 100m steps. attention will include but not be limited to:
 At 500-100m distance from jacket the vessel speed shall be  Safe approach speed
maintained within 0.2m/sec in 50m steps.  Clearance distances, any other established safety margins
 At 100m distance from jacket the vessel speed shall be maintained  Ability to control HYSY278 under normal circumstances
within 0.1m/sec in 10m steps.  Ability to control HYSY278 under adverse circumstances

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 Log keeping ability report, Figs. 6a & 6b show two screenshots of the STC debriefing
 Overall performance simulator software interfaces which illustrates the fendering system and
 Conclusions the jacket row identification.
 Recommendations
 Lessons learned Attendees

The key issues within this program were the safety and efficiency of the
defined DP operation simulations and the training experience of the
individual participants. In order to accurately simulate the DP floatover
operation that is going to be completed offshore, the following key

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operation personnel were present:
 Dynamic Positioning Officers, AHT Tug Masters, Winch Operators,
Positioning Survey Engineers
 Installation Manager, Superintendents, and Field Engineers
 Client Reps, MWS surveyor

Tests and measurements were related to all the personnel participating,

indirectly and directly including all the operation procedures, execution
plans and systems such as emergency responses, change management
procedures, risk assessment and job safety analysis procedures.

STC personnel include project manager, mathematical model builders,

software engineers, exercise coordinator, DP specialists, IOS operators,
technical specialists, etc., who were present to direct, coordinate,
a) Surge Fenders and Jacket Entry Guides support the entire simulation program.

SIMULATOR MODELS

For the simulator training, new mathematical models and a visual

database were developed. This section describes the characteristics of
these new models and the existing models used in the VR simulations.
Both the methodology employed and the models used have undergone
through internal and external validations prior to commencement of the
simulations. The visual database and mathematical models shall be
validated by STC internally and Client externally.

Visual Database

The new visual data base consists of

 Filed area layout for instructor’s use
 Bathymetry
 Location and visualization of Jacket without DPP Topsides
 Visualization of the DPP Topsides and DSF
 Location and visualization of Jacket with DPP Topsides
b) Jacket Row Identification and Sway Fenders
Fig. 6: STC debriefing simulator software interface
HYSY278 Modeling with or without Topsides
In addition to the STC reports, any comments/recommendations by
Client and/or the DNV GL ND Marine Warranty Surveyor were taken Two mathematic models of the floatover vessel, DP2 X-Class
into consideration. All reports are of a confidential nature and will be semisubmersible vessel HYSY278, were developed for the DP
treated as such. The debriefings were facilitated by a member of the simulations:
STC and supported by the STC exercise coordinator. The debriefing  Vessel Model HYSY278 with DPP Topsides shown in Fig. 7a, used
took place in Classroom 4. All exercises were saved electronically and for docking operation.
provided to Client at the end of the program. At the end of each day a  Vessel Model HYSY278 without DPP Topsides shown in Fig. 7b,
session of lessons learned and program planning for the next day was used for undocking operation.
conducted. This provided a round-up of the conclusions and
recommendations and established a way forward for the next day of the Table 2 shows the principal parameters used to model the floatover
simulation program along with a shared mental model for all. vessel HYSY278 with DPP topsides and without DPP topsides,
respectively. The wind loads acting on both the vessel models with and
The capable exercise coordinator experienced in DP offshore without DPP Topsides, including forces and moments, are modeled as a
operations was assigned by STC to debrief the training program and function of wind direction and wind speed of 1.0m/sec. These wind
discuss the lessons learned during the exercises. This person should not forces were obtained from empirical approximations and included
be affiliated with Client and Contractor Representatives, or any of the within the simulations by means of deduced wind coefficients which
subcontractors. To better understanding the debriefing and assessment were acting on frontal and lateral wind areas, respectively. Ideally wind
tunnel tests should be conducted to estimate the wind coefficients for

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the vessel HYSY278 with and without DPP topsides, and thereby The coordinate system used for the DP simulations is illustrated in Fig.
producing more accurate wind force coefficients used for the DP 8. All the environmental components and their directions, that is, waves,
simulations. The wind is modeled by using a Davenport variation. current, wind, are defined in the vessel’s coordinate system as the angle
Some deviation in wind strength and wind direction is taken into from the positive x-axis to the direction in which it is travelling,
account in the simulation. measured in anti-clockwise. Therefore, wind and waves coming from
astern are defined as a direction of 0 degree; wind and waves from
starboard as a direction of 90 degrees; wind and waves from the bow as
a direction of 180 degrees. The current direction is defined as going
from the vessel, which is opposite heading of wind and waves’
direction. The parameters given in Table 2 are defined the coordinate

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system convention described in Fig. 8.

a) HYSY278 with DDP for Docking: Draft = 8.00m

Fig. 8: Coordinate System of DP Simulations

The current loads on the wet hull of vessel HYSY278 including forces
and moments are also modeled as a function of current direction and
b) HYSY278 without DPP for Undocking: Draft = 11.35m
current speed of 1.0m/sec. The current force coefficients were derived
Fig. 7: DP Vessel Models with and without DPP Topsides
from empirical formula and were included within the simulations by
means of deduced current coefficients which were acting on frontal and
Table 2. Principal Parameters of DP Floatover Vessel HYSY278
lateral wet hull areas, respectively. The resulting wind and current
forces acting on the vessel models with and without DPP Topsides
Particulars Unit w/DPP wo/DPP were developed during the simulations when the met-ocean data were
Length Overall [m] 221.60 221.60 determined for the simulation scenarios. It should be pointed out that
Breadth Moulded not all the current force coefficients as supplied could be included
[m] 42.0 42.0
exactly in the simulator model for every angle of attack. In reality when
Depth Moulded [m] 13.30 13.30 homogeneous current is from the beam, the yawing moment may be
Floatover Draft [m] 8.00 11.35 neglected. If this is implemented in the STC model, the vessel
HYSY278 will not start yawing when the current angle of attack is 45
Displacement [Te] 58,834 87,321 degrees. When the yawing moment is included in the model for an
Windage Area Frontal [m2] 5,513 652 angle of attack of 45 degrees, the yawing moment for angle of attack of
0-degrees will be overestimated in the model. A compromise had to be
Windage Area Lateral [m2] 4,903 822 made to handle this problem. Because wind forces are dominating, it is
Current Area Frontal [m2] 328 465 allowed to make this simplification. The current force coefficients of
Current Area Lateral [m2] 1,773 2,477 the vessel wet hull derived from empirical formula were implemented
in the simulator.
Radii of Gyration Rxx [m] 21.06 13.97
Radii of Gyration Ryy [m] 58.88 53.76 Mathematical Model
Radii of Gyration Rzz [m] 58.89 54.69 The Euler Equation for ship maneuvering in horizontal plane is derived
Center of Buoyancy XCOB [m] 104.82 102.49 from Newton’s Second Law, that is:
Center of Buoyancy YCOB [m] 0.00 0.00
X =
m(u − vr ) Y=
m(v + ur ) N=
I z r (1)
Center of Buoyancy ZCOB [m] -3.80 -5.35
Center of Gravity XCOG [m] 104.82 102.49 where X, Y, u and v are the force components and the velocity
Center of Gravity YCOG [m] 0.00 0.00 components in x and y direction and N is the moment component
around z axis, respectively; m and Iz are the total mass and the inertial
Center of Gravity ZCOG [m] 8.61 -3.20 moment of the vessel around z axis; r is the yaw acceleration and δ is

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the rudder angle. Refer to Fig. 9 for details of the coordinate system and moments as a function of current direction based a current speed of
convention. 1.0m/sec on the HYSY278 wet hull were provided by the Client. The
current forces were included within the VR simulations by means of
deduced current coefficients which were acting on frontal and lateral
wet areas. The current force coefficients were used in the simulations
for both HYSY 278 wet hull models during docking and undocking.

Data on the wind loads including forces and moments are a function of
wind direction based on a wind speed of 1.0m/sec on the HYSY278
hull and topsides models during docking and on HYSY278 hull and

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DSF models during undocking. The wind forces were included within
the VR simulations by means of deduced wind coefficients which were
acting on the frontal and lateral windage areas of HYSY278 hull,
topsides, and DSF.

There are first-order and second-order wave forces due to waves. The
second-order slow drift wave forces are of interest in DP static analysis.
These drift forces are calculated within the Diomedea program, which
are dependent on wave height and peak period and are of reasonably
Fig. 9: Coordinate Systems of Ship Maneuvering practical indicative order.

In general, the forces and moments are the function HYSTY278 Thruster Location & Capacities: The 7 thruster locations
f u , v, r , u , v, r, δ , δ）. The maneuvering simulations adopt a ship-bound
of （ and their nominal capacities of DP vessel HYSY278 are listed in Table
system O(x, y, z) which is a different approach to a seakeeping 3 and defined in Fig. 10. HYSY278 is equipped with three different
simulation whose motion equations are written in an earth-bound types of thrusters, i.e. three tunnel thrusters, two azimuth thrusters, two
system o(xo, yo, zo). When heel angle is less than 10° or Froude main propellers, and fitted out with two Becker rudders placed directly
numbers is less than 0.25, the heeling effect on these variables are astern of the main propellers. DP capability plot of HYSY278 follows
negligible. When ships have small deviations from a straight path, only the specifications of IMCA M140 (2000).
linear terms in the expressions of Taylor expansion for the force and
moment should be retained. In addition, all those terms due to
symmetric ships will vanish. Using the simplified derivative notation of
SNAME Nomenclature 1952, e.g. ∂Y / ∂v =Yv and non-dimensional
hydrodynamic coefficients by a primed symbol, the linear non-
dimensional equations of motion with moving axes in the horizontal
plane are given by Bertram (2000) as follows:

( X u' − m ' )u ' + X u' Du ' =0 (2)

  '
M 'u + D 'u = rδ

where ∆u ' = ( u − U ) / u

 −Yv' + m' −Yr' + m ' xOG'

  v 
'
M' =   u' =  '  (3)
 − N v + m xOG − N r + I z 
' ' ' ' '
r 
 −Yv' −Yr' + m '   Y 
'
D' = ' ' 
r '  δ' 
 − N v − N r + m xOG 
' '
 Nδ 

'  
M , D ,
'
r and u are the generalized mass matrix, damping matrix,
' '

rudder effectives vector, and motion vector. These generalized Fig. 10: Coordinate System and Location of HYSY278 Thrusters
hydrodynamic coefficients can be evaluated from the formulae based
on theoretical equations and model experiments. U is a reference speed, Table 3. Thruster Locations and Nominal Capacities
normally the initial speed of the vessel maneuver.
Thruster +ve Forward +ve Portside Power Capacity
Environmental Forces: The IMCA Specification (2000) gives Unit [m] [m] [kW] [kN]
Bow Tunnel Thruster T1 98.568 0.0 2,000 263.0
guidance on the creation of DP capability plots based on the mean loads
Bow Azimuth Thruster T3 92.484 0.0 2,000 315.0
duo to one-minute average wind speed, current speed and wave drift Bow Azimuth Thruster T4 85.284 0.0 2,000 315.0
loads, which can be obtained by either model tests or numerical Stern Tunnel Thruster T2 -91.836 0.0 2,000 263.0
analyses. Stern Tunnel Thruster T5 -95.832 0.0 2,000 263.0
Main Propellers T6 -100.332 8.748 5,500 867.0
Due to lack of the model test results, the current and wind force Main Propellers T7 -100.332 -8.748 5,500 867.0
coefficients are based on industrial recommendations by IMCA M140 Portside Rudder -105.444 8.748
(2000) and OCIMF (1994). Data on the current loads including forces Starboard Rudder -105.444 -8.748

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Note that the thruster capability of main propellers in the reverse RadaScan and a laser radar system CyScan, are emulated as being
direction is approximately 70% of the nominal thruster in the forward installed on the vessel stern deck to avoid any blockage of the topsides.
direction. Due to the block effect of the main propeller’s shafts, the The two stacks of six retro prism reflectors are installed on the jacket.
thruster capability of stern tunnel thrusters is approximately 60% of The mini RadaScan responders are amounted on the jacket, next to
their nominal thrusters. CyScan reflectors. These two local reference systems will be activated
and switched from DGPS system as the vessel approaches the jacket
AHT Positioning Tug is used as an emergency plan in case of DP and the CyScan/RadaScan comes into range, normally 350m to 500m
failure of HYSY278 and should be modeled per principal parameters of away from the jacket. Fig. 11 shows both the local reference
actual AHT tug selected. The visual model and virtual model of the positioning systems CyScan and RadaScan are installed at centerline
positioning tug such as Fairmount Sherpa is selected from the STC 50m away from stern and approximately 3m above deck, thus ensuring

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existing model database. During the VR simulations, the AHT tug can clear line of sight between master units and reflectors.
be operated by Tug Master or by IOS operators as a vector tug.
SIMULATION RUNS
Soft Lines: The soft line hawsers are used with two 75Te winches
positioned at stern of HYSY278 as an emergency plan in case of A proposal of simulation runs was submitted by Client upon which
docking failure of HYSY278. The soft lines function as cross lines there are two main objectives. One objective is to confirm whether the
during docking operation. These soft lines are modelled and practically DP floatover operation can be successfully and safety executed while
possible in order to produce the proper transient behavior of these lines the other objective is to act as a training and teambuilding exercise for
when paying in or out of the soft lines by IOS operators or winching the key participants, especially Dynamic Positioning Officers (DPOs).
operators during the VR simulations. Each simulation run consists of four distinct elements: Briefing prior to
Execution, Simulation Execution, Completion of the Training
Fender System: Any fender force modelled as contact elements in the Questionnaire and Debriefing. Each simulation run was recorded
Diomedea simulator is a direct result of contact between a part of the digitally with a specific STC file name and stored in the debriefing
vessel’s hull and the fender in question. This contact results in a system. The final simulation assessment report along with the electric
displacement of the fender. The fender force produced by this contact is files will be made available to Client at the end of the simulations. At
directly proportional to the deflection of the fender, i.e. function as a the end of each day, a round-up session discussing lessons learned was
spring term, and the rate of variation in time of the same displacement, executed.
i.e. function as a damping term which dissipates contact energy. The
fender force thus produced is perpendicular to the contact element. Due Each simulation run shall include the followings:
to the fender force, a friction force acting in a direction parallel to the  Exercise start condition and screen shot, objective and
contact element is generated in opposite direction to the relative motion environmental condition, names of all participants (IOS operator,
between the fender and the contact element. This friction force is Client participants, external expert(s), etc.)
maximized up to 14% percentage of the fender normal force, which is  Various screenshots at key moments
typical maximum friction coefficient between the Teflon pad and the  Observations: Human Resource & Knowledge/Skill
steel hull. Should this maximum friction force be exceeded, then the  Conclusions
vessel will as a result slide along the fender in the direction of relative  Recommendations
motion between contact element and fender.
The simulation runs encompass all the scenarios of various floatover
operations, including a series of positioning trials, moving to standoff
position, approaching to pre-installed jacket, docking into jacket slot,
undocking operation, etc. The simulation scenarios are tested under
normal environmental conditions and extreme environmental
conditions, as well as a number of stressful conditions, such as thruster
failure, adverse internal wave current, power blackout, etc. Some of
typical simulation runs are described hereafter.

Fig. 11: DP Local Reference Position Systems: CyScan & RadaScan

Local Reference Systems: RadaScan & CyScan: Several methods are

used to measure the vessel position and heading. The DP position
reference systems installed on the HYSY278 include two DGPS
Position Reference Systems, one laser radar system CyScan/Laserbeam
and one a microwave positioning system RadaScan, which were used in
the simulations. The DGPS systems are mainly used when the vessel is
more than 500m away from the jacket based on the as-built geo-
coordinates of the pre-installed jacket. The high-precision millimeter-
level local reference systems, that is, a microwave positioning system Fig. 12: Vessel Trajectory during Positioning Trial: Run D1R3

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Simulation Run D1R3 was maneuvered in a controlled fashion at all
times, albeit not via the auto DP system.
Run D1R1 was utilized only as an observational and familiarization  Familiarization for DPO No. 3 successful.
exercise for participants to view set-up of bridge, positioning master Recommendations  Future scenarios will be executed with less
position, instructor operating stations (IOS), etc. Run D1R3 was wind.
designed for DPO No. 3 during positioning trails. Table 4 summarizes  Familiarization completed, next exercises:
the Run D1R3 simulation activities and debriefing process. During the moving to stand-off position
debriefing session, the Human Resources include Situational
Awareness, Communication, Challenge and Response, Shared Mental Simulation Run D2R6
Model, as well as input from the individual questionnaire, and the

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Knowledge/Skill/Procedures include operation procedures, vessel speed Run D2R6 was designed for DPO No. 1 during docking operation.
and heading control, safety margins, etc. Fig. 12 shows the vessel Table 5 summarizes the Run D2R6 simulation activities and debriefing
trajectory during the positioning trials, as well as the vessel position at process. Fig. 13 shows some typical positions during the docking
the end of the simulation. operation.

Table 4. Simulation Run D1R3 & Debriefing: Positioning Trials

Item Description
SIMULATION RUN: D1R3
Start Condition DPO started elapsed time: 02:29
 Open water start heading 240°
 HYSY278 with topsides
Metocean Data
Wind Mean Speed = 18 knots at EL(+)10m
Heading = 308°
Waves Significant Wave Height = 1.5m
Heading = 308°
Current Surface Speed = 1.5 knots
Heading = 180°
Objectives  Maintain position in target zone within 50m
circle a) At Starting Position
 Move forward 100m
 Move backward 100m
 Move starboard 50m
 Move portside 50m
 Turn 10° and another 10°
 clockwise
 Turn 10° and another 10°
 anti-clockwise
 Move slowly forward 50m
DEBRIEFING
Human Resources  Alarms accepted (improved situational
awareness).
 Discussion on bridge regarding response of
model and familiarization of equipment. Early
stages of “Shared mental Model”.
 Challenge from new instrumentation and b) Approaching to Jacket
handling characteristics.
Knowledge/Skill/  Alarm indicates too much power on stern
Procedures thrusters. This is deemed not significant
because we are not in the vicinity of the Jacket
 00:26 vessel unable to stop with current wind
condition on DP, switched to joystick to slow
vessel then back to DP at 00:31 to check
response. DP system not holding position.
Deck load switched on and off as a test.
 00:41 attempting moving forward 100m.
 Adjusting various controls on the DP system as
part of the familiarization process. DP system
not holding. Simulation stopped.
 00:47 exercise ended.
Conclusions  DP switch on deck load must be on for all
exercises draft 8.0m
 With given environmental conditions the vessel c) Just Passing through Sway Fenders at Row B

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 Recommendations  A test will be made in open water changing
from DP to joystick to determine if a jump
occurs. This is related to the event at 00:32,
refer to Challenge and Response. Should this
not reveal any reaction we will try staying on
DP and entering jacket again to see if there is a
jump while in proximity to surge fender.
 The bridge team will develop another form of
reporting from aft to bridge to avoid confusion,
refer to Communication.

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 The bridge team will endeavor to reply to all
communications with aft spotter and to clarify
if necessary, refer to Situational Awareness.

Simulation Run D3R7

d) Arrival at Final Mating Position
Fig. 13: Typical Positions during Docking Simulation: Run D2R6 Run D3R7 was designed for DPO No. 2 during docking operation,
which is the case of unexpected failure of Thruster No. 5, when the
Table 5. Simulation Run D2R6 & Debriefing: Docking Operation vessel stern is half way between Rows A and B. Table 6 summarizes
Item Description the Run D2R6 simulation activities and debriefing process. Fig. 14
SIMULATION RUN: D2R6 shows some typical positions during the docking operation.
Start Condition DPO started elapsed time: 00:11
 Docking operation start 100m from Jacket Table 6. Simulation Run D3R7 & Debriefing: Failure of Thruster No. 5
Metocean Data Item Description
Wind Mean Speed = 12 knots at EL(+)10m SIMULATION RUN: D3R7
Heading = 135° Start Condition DPO started elapsed time: 00:20
Waves Significant Wave Height = 1.5m  Docking operation start 100m from Jacket
Heading = 135° Metocean Data
Current Surface Speed = 1.2 knots Wind Mean Speed = 12 knots at EL(+)10m
Heading = 315° Heading = 180°
Objectives  Approach to Jacket from 100m Waves Significant Wave Height = 1.5m
 Initial Entry into Jacket Heading = 180°
 Pass through Row B Current Surface Speed = 1.2 knots
 Arrival at the final mating position Heading = 0.0°
DEBRIEFING Objectives  Thruster No. 5 will fail unexpectedly when the
Human Resources  00:16 Bridge to Stern “Ok I’ve stopped”. Stern stern is half way between Rows A & B
to Bridge “Why did you stop?” No reply from  Determine if the bridge team can maintain
bridge team, break in communications. control
 Why does the man aft say to alter course, when  Move to final docking position
the answer might be a bodily shift? DEBRIEFING
 00:32 you will hit the corner….(what actions Human Resources  Proper Communication between stern and
were executed by bridge team), entering jacket bridge: Good Situation Awareness.
 Excessive speed in jacket indicates loss of  00:47 detected Thruster No. 5 failure within
situational awareness. seconds, call ER to shut down: Good
Knowledge/Skill/  00:27 35 meters approaching jacket, shown in Situational Awareness.
Procedures Fig. 13b. Knowledge/Skill/  00:40 switch to joy-stick control and contacted
 Approaching on auto DP, will switch to Procedures corner of Row A with stbd. quarter
joystick mode  00:44 Thruster No. 5 failure (full RPM’s)
 00:35 speed 0.3m/s, why? (Event 1)
 00:37 aft section passes Row B, shown in Fig.  00:45 call from bridge to ER shut down
13c. Thruster No. 5
 00:45 in position end of exercise, shown in Fig.  00:59 end of exercise but vessel heading 1° off,
13d. not on surge fenders evenly.
Conclusions  Beginning an exercise from 100m is sufficient Observation  The switch to joy-stick and deselecting sway or
to allow the bridge team to settle the vessel surge does not make any difference to
before exercise begins. dampening the effect of the swing of the stern
 Incorrect reference line was chosen for jacket to stbd for this DP simulator.
approach which indicates familiarization is Conclusions  The bridge team was able to successfully
ongoing with the DPOs. maneuver the vessel into the final docking
 When switching from DP mode to joystick position with a random failure of Thruster No.
mode, some slight sway can be experienced. 5 and with given environmental conditions.
 The bridge team was successful in Recommendations  After mating time should be allowed for some
maneuvering into the final mating position settling of the simulation before ending run.
with anticipated environmental conditions.

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 RECOMMENDATIONS & CONCLUSIONS

This simulation training program for DP flaotover operations deliver

the following recommendations and conclusions.

 Familiarization of simulation system and review of agreed

parameters in the beginning of project is vital to its success. Not all
simulations systems are identical in performance thus time and
exercise is required to “get the feel” of the model response such

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that it can be operated successfully.
 The layout of DP systems in general requires review. Alarm screens
for example should not be positioned behind panels required for
immediate operations.
 The starting position for such exercises should be in the vicinity of
a) At Starting Position 100m from the jacket to give the bridge team sufficient time to
orient the vessel.
 This project made use of 23 simulations. This number appeared to
strike the correct balance between effectiveness and pointless
repetition. Too few simulations run the risk of providing inadequate
opportunity to see the DPO’s in sufficient variety of simulations.
For example; after day one and well into day two only then were
gaps in BRM skills discovered. This is vital in the improvement of
performance bridge team as well as discovering inherent errors,
previously undiscovered.
 The two main issues which were of most concern were vessel speed
and heading. Speed within the jacket which exceeded agreed safety
parameters and deviations in headings which presented not only a
problem for the approach, but also problems when within the jacket.
Skewing within the jacket can lead to excessive force on the sway
b) Jacket Initial Entry fenders and jacket structure itself.
 A variety of contingency plans were exercised. When designing
simulations for such plans, due considerations must be given to the
models used. In this project it was clear that vector winches as per
the simulator model are not suitable for testing a contingency plan
which required winches of a different operating design.
 For emergency departure in the event of a black-out, the Master
Tug should have a position indicator of the vessel HYSY278 to
facilitate a safer departure.

ACKNOWLEDGEMENTS

Several people have contributed to this work in many vital ways. Very
special thanks to Mr. Jakob Pinkster, Mr. Jan S. Bakker, Capt. Pieter
Bas Schoe, and Capt. John E. Hutchins from STC B.V. for their
enthusiastic support, invaluable experiences and expertise.
c) Just Passing through Sway Fenders at Row B
REFERENCES

Bertram, V (2000). Practical Ship Hydrodynamics, Butterworth-

Heinemann, Linacre House, Jordan Hill, Oxford, 270pp.
IMCA (2000). Specifications for DP Capacity Plots, The International
Marine Contractors Association, IMCA M 140 Rev. 1, June 2000,
13pp.
Jin, XJ, Wang, AM, Li, HL, Yu, WT, He, M and Wang, A (2018). "
Floatover Installation Technology with a DP2 Class Dynamic-
Positioning Semisubmersible Vessel," Proc 20th Int Offshore and
Polar Eng Conf, Sapporo, Japan, ISOPE, Vol 1, pp 962-971.
OCIMF (1994). Prediction of Wind and Currenr Loads on VLCCs, Oil
Companies International Marine Forum, OCIMF 2nd Edition, 1994,
52pp.
d) Arrival at Final Mating Position Pinkster, J (2012). "Full Mission Bridge Simulations - a Must for
Fig. 14: Typical Positions during Docking Simulation: Run D3R7 (Complex) Offshore Projects," Proceedings of Society for Underwater
Technology Technical Conference, SUTTC-2012, Shenzhen, China,

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 6pp. Wang, AM, Pinkster, J, Jiang, XZ, Li, ZG, Yu, CS, and Zhu, SH (2010).
Wang, AM, Jiang, XZ, Yu, CS, Zhu, SH, Li, HL, and Wei, YG (2010). "Virtual Simulations of VLCC Class FPSO-SYMS Mating Operation,"
"Latest Progress in Floatover Technologies for Offshore Installations Proceedings of the 20th International Offshore and Polar Engineering
and Decommissioning," Keynote Paper, Proc 20th Int Offshore and Conference, Beijing, China, ISOPE, Vol 1, pp 9-20.
Polar Eng Conf, Beijing, ISOPE, Vol 1, pp 9-20.

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