Ambrosovskaya_Navis_v004

1. Dynamic positioning for fully-actuated autonomous vessels: key specifics

Elena Ambrosovskaya, Ph.D
Senior Researcher, Navis JSC (R&D Department), St. Petersburg, Russia
Ass.Prof. St. Petersburg Electrotechnical University ``LETI'', Russia
(Ship control system department)
Dmitry Romaev
Senior Researcher Navis JSC (R&D Department), St. Petersburg, Russia
International Intelligent Ship and Autonomous Navigation Technology Forum
Wuhan 2026
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2. Plan

• Dynamic positioning – principles, functions, hardware, quality (sea
trials data, Navis DP5000)
• Fully actuated/underactuated property
• Dynamic positioning for autonomous fully-actuated vessels
• Special problem: towing with autonomous tugs as DP problem
(simulation)
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3. Dynamic positioning (conventional)

DP System is a computer-controlled
system to automatically maintain a
vessel's position and heading by
using its own propellers and
thrusters.
Basic Modes:
• Auto Position
• Auto Heading
• Manual Position(Joystick)
• Manual Heading (Knob)
• Speed Vector
• Target following
• Low Speed Track
• High speed modes (autopilot,
high speed track)
Applications:
• Platforms
• Platform Supply vessels
• Offshore Supply vessels
• Research vessels
• Crewboats
• Crane vessels
• Stone Dumpers
• Shuttle tankers
• Drillships
• Diving Support
• Cable/Pipe Laying
• Dredging vessels
DP classes:
• Joystick systems
• DP0
• DP1
• DP2 - Redundant
• DP3 - Redundant
DP consists of:
• Control Computers
• Operator stations, control
panels
• I/O units (PLC based)
• Interfaces with digital data
(sensors, power station)
Algorithms:
• Sensors/Ref systems filtering / sensors
fusion
• Controller
• Thrust allocation with Power monitoring
• Fault detection, alarms
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4. DP Principles (Convential)

Controller: make Fx, Fy, Mz (desired values):
Fx, Fy to keep position or create speed vector
Mz to keep heading or create set ROT
TAL: make ui (thruster controls) to minimize
allocation error:
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5. DP Quality: Box maneuver (20m)

• 2026 DP2 Sea Trials
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6. DP Quality: Heading control, Auto Position

• Remote COR
point + change
heading
39m OSRV vessel
2025 DP0 (Sea
Trials)
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7. DP Quality: Track Control

Low speed track (high quality
slow motion) 2026 Sea Trials
OSV vessel
OSV vessel goes on track with speed about 1 knt: ~0.3 m XTE quality:
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8. Fully-actuated in horizontal plane

• Ship motion: 6 DOF
• Horizontal motion: 3 DOF
Fully actuated: independent control of all
DOF
In horizontal plane: independent surge,
sway, yaw
LS track, Hold pos + any heading, speed
vector + any drift, any heading
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9. Fully actuated: how to check? Thrust ability diagram

What force we create when fix
z-moment value? Combination
of force diagrams of actuators.
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10. Fully-actuated/Underactuated. Propulsion

• Underactuated: no possibility create
side force without depending
moment
• Fully-actuated
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11. DP Thrust Ability is not equal to DP Capability

DP Capability is wind (environment) we can compensate
when staying.
No any side wind capability (90 deg) is no side force create
possibility
Know max control forces for actuator, solve TAL problem and
found max wind + wave force -> recalculate to wind speed
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12. Fully-actuated/Underactuated. Low and high speed

Example: cable layer goes on low speed
track (1-2 knots) with 90 deg drift
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13. DP2 Hardware

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14. DP0 Hardware

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15. USV / MASS. Classification

Terms
• Unmanned Surface Vehicles (USVs) - autonomous or remotely
operated vessels
• Maritime Autonomous Surface Ships (MASS)
Classification by size / class, mission / application, and level of
autonomy / control, hull type
Small / micro USVs: ≤ 5 m
Medium USVs: 5–10 m
Large USVs: around 10–20 m
Fleet class> 20–24 m
Monohull
Catamaran
Trimaran
Hydrographic / oceanographic survey
Environmental & meteorological
monitoring
Defense / naval
Port / security and inspection
Firefighting
Tugs
Educational/research
Remotely operated (joystic etc)
Partially autonomous (WP
navigation)
Highly / fully autonomous (Long
distance, collision avoidance etc)
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16. DP Principles

For MASS:
+ Communication
+ Path planning
+ Remote operations
- Control panels onboard
- Operator activity onboard
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17. DP System applications to MASS

DP as “magic-box” (DP Controller
or Small DP system) to create
force, speed, maintain position
and track, autopilot functions
API to remote control station
Support digital interfaces to
thrusters
Requirements:
Fully-actuated
Sensors
Ref-systems
Actuators 100%duty-cycle
DP Capability analysis
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18. Classic DP Approach example: small autonomous tug, DP0, remote and automatic control

• Automatic small tug, fully-actuated.
Propulsion examples: 2 Azimuth Thrs
(Bow + Stern) or 2 Azimuths in stern +
Tunnel
• Electric Propulsion
• Capability
• Functions: approach, following,
towing
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19. Simulation results

Navis DP5000 for
autonomous tug,
SimTech remote control
station
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20. DP Approach to towing with autonomous tugs

• Big Vessel: one from library
• Path Planning
• Tugs as thrusters, “slot” for tug
• Control
• Allocation
• Sensors fusion
DP System
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21. Tug as azimuth thruster

• If fully-actuated: any Fx,
Fy with Moment = 0
• Input action (API): desired
force (like joystick force)
• Limitation of F pulling
(depending on fix type)
• Sector limitation
• “Slot” for tug
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22. Towing Capability

• DP Capability, Tugs = Thrusters,
included limitations
• + Hydrodynamic force (nonzero
speed of towing): Fh includes
current + ship hydro
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23. Simulation results: Towing

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24. Simulation Results:

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25. Conclusion

• Autonomous DP = DP + communications + path planning + remote
operations / API = DP
• High quality control performance on low speed is possible if
autonomous vessel is fully-actuated
• DP (DP controller, small DP0/DP2 (non-redundant/redundant system))
can be a “magic box” realizing sensors fusion, control laws, thrust
allocation
• DP can be used for special autonomous applications: for example
automatic towing
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26.

My researchgate
Elena Ambrosovskaya
– Ph.D., senior
researcher in Navis
JSC, S-Petersburg,
Russia; ass.professor in
Electrical Engineering
University (Ship
Control Department)
Research interests:
ship motion
simulation, data
processing, sensors
fusion, ship motion
control, dynamic
positioning,
identification etc
My department in University
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27.

Our Partner in China: DYPOS
Marine
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28.

Thank you for attention
谢谢
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