DP Description

1. Basic DP Principles
Forces & Motions
Measurements
DP Control

2. Dynamic Positioning simply explained
Sense
Assess
Respond
Dynamic
Positioning

3. Dynamic Positioning
• Keep the vessel within specified
position- and heading limits
• Minimize fuel-consumption
• Minimize wear and tear on thrusters and
propulsion equipment
• Fault tolerance
• reference systems and sensors
• thrusters
• computer system

4. Dynamic Positioning System
Components - Diesel Electric Propulsion
• Power plant
• power generation
• power distribution
• Propulsion / thruster system
• drives
• thrusters
• Control systems
• DP control system
• independent joystick system
• manual thruster control
system
• power management system

5. Basic Forces and Motion
• Three degrees of freedom
• Surge
• Sway
• Yaw
• Environmental Forces
• Wind
• Waves
• Current
• Thruster Forces
• Tunnel thrusters
• Azimuth Thrusters
• Propulsion/ Rudders

6. SURGE SWAY YAW
Measured by means of
Position Reference Systems
Measured by means
of Gyro compass
Measurements - Position and Heading

7. Measurements - Attitude
H L E
PITCH ROLL HEAVE
Measured by means of
Motion Reference Sensors

8. Input to the
Dynamic Positioning System
Reference Systems and Sensors
Position Reference Systems
Satellite Systems
Laser Systems
Radio Systems
Acoustic Systems
Taut Wire
Motion Reference Sensors
MRU
Heading Measurements
Gyro Compass

9. The Dynamic Positioning Control
1
2
3
1
2
3
Extended Kalman Filtering
Controller
Thruster Allocation

10. The Extended Kalman Filter
Calculate most accurate position, heading, speed of the vessel
Calculate unmeasured environmental forces acting on the vessel
1
• Position
• Heading
• Motion
• Environmental forces
Based on a mathematical
model of the vessel and
sensor and reference system
readings, the Kalman filter
estimates:
1
Input data to the Controller

11. The controller calculates force required from
thrusters/propellers to:
• Compensate environmental loads
• Restore position
• Stop motion
Calculate force demand
2
1
Input data to the
Thruster Allocation Function
Calculate most accurate position, heading, speed of the vessel
Calculate unmeasured environmental forces acting on the vessel
2
Rotational
Moment
Directional
Force
The Controller

12. Allocation
of demand
Distribute force demand to each thruster,
propeller and rudder (pitch, rpm, azimuth)
3
Calculate force demand
2
1 Calculate most accurate position, heading, speed of the vessel
Calculate unmeasured environmental forces acting on the vessel
• Handles any configuration of thrusters, rudders
and propellers
• Optimum thruster/ propeller use
• Redistributes signals if one thruster is down /
disabled
• If total force-demand exceeds available thrust;
heading is prioritized
• Error detection if failure in the thruster system
3
The Thruster Allocation