Dynamics of Dynamic Positioning Systems
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Questions and Answers

What are the three horizontal degrees of freedom that a DP system typically controls?

  • Surge, sway, and yaw (correct)
  • Surge, heave, and yaw
  • Pitch, roll, and yaw
  • Roll, sway, and yaw

    • What is the primary function of the mathematical model in a DP system?

  • To directly control the movement of the vessel's thrusters
  • To predict the vessel's heading, position, and speed based on forces acting on it (correct)
  • To generate the exact thrust required for each thruster
  • To track the vessel's position and movement in real-time

    • What factors are used as input to the mathematical model?

  • Wind speed and direction, thruster/propeller pitch/rpm and direction
  • Vessel's heading, position, and speed
  • Sea current and wave forces
  • All of the above (correct)

    • What is the purpose of the Kalman filtering technique in a DP system?

    <p>To continuously correct and improve the accuracy of the mathematical model</p> Signup and view all the answers

    How are wind forces calculated in a DP system?

    <p>As a function of measured wind speed and direction</p> Signup and view all the answers

    How does a DP system determine the forces the thrusters should produce?

    <p>By calculating the forces needed to minimize the deviation between the vessel's actual position and its required position</p> Signup and view all the answers

    What is the primary limitation of the mathematical model in a DP system?

    <p>It is not able to account for all the forces acting on the vessel</p> Signup and view all the answers

    How does the DP system use the data from gyrocompasses and position-reference systems?

    <p>To update the mathematical model with real-time information about the vessel's position and heading</p> Signup and view all the answers

    What are the main components of the DP system?

    <p>Power supply system, Thruster system, Reference systems, Sensor, Control system, Steering console and System operator</p> Signup and view all the answers

    What are some of the key characteristics of the power supply system?

    <p>High flexibility, high reliability, continuity of work, high accuracy</p> Signup and view all the answers

    What type of propeller is most commonly used in DP systems?

    <p>Controllable Pitch Propeller</p> Signup and view all the answers

    What is a Becker rudder?

    <p>A type of steering gear used in DP systems</p> Signup and view all the answers

    What is the purpose of manoeuvring thrusters?

    <p>To provide propulsion in lateral directions</p> Signup and view all the answers

    What are Azipod thrusters?

    <p>A type of thruster used in DP systems</p> Signup and view all the answers

    What are the main characteristics of reference systems used in DP systems?

    <p>High accuracy, high reliability, continuity of work</p> Signup and view all the answers

    What is the minimum time that the control system, control console, displays and alarm systems, and reference systems of the DP system must be able to operate for in the event of a failure of the main power system?

    <p>30 minutes</p> Signup and view all the answers

    What significant development occurred in the United Kingdom in 1977 regarding drilling technology?

    <p>First semi-submersible drilling rig launched</p> Signup and view all the answers

    Which company was responsible for the first research on DP systems in Norway?

    <p>Kongsberg Vapenfabrikk</p> Signup and view all the answers

    What percentage of the world market for DP systems did Kongsberg capture by 2012?

    <p>75%</p> Signup and view all the answers

    Which of the following is NOT an application of DP systems?

    <p>Emergency Response Vessels</p> Signup and view all the answers

    What is a primary factor in determining the required equipment class for a DP system?

    <p>Risk analysis of position loss</p> Signup and view all the answers

    What does FPSO stand for in the context of DP applications?

    <p>Floating Production Storage and Offloading</p> Signup and view all the answers

    Which type of vessel is primarily associated with underwater cable laying and repair using DP technology?

    <p>Cable Lay/Repair Vessels</p> Signup and view all the answers

    What is the main purpose of developing redundancy in DP systems?

    <p>To ensure position keeping capability</p> Signup and view all the answers

    What occurs in equipment class 1 in the event of a single fault?

    <p>A loss of position and/or heading may occur.</p> Signup and view all the answers

    Which class does not allow a loss of position and/or heading in the event of a single fault?

    <p>Equipment class 3</p> Signup and view all the answers

    What type of components may be accepted in systems of equipment class 2?

    <p>Common static components without immediate positioning effects</p> Signup and view all the answers

    Which of the following describes 'rolling' movement of a ship?

    <p>Tilting side to side on the X-axis.</p> Signup and view all the answers

    What is measured by the position-reference systems on a seagoing vessel?

    <p>Changes in position, heading, and speed</p> Signup and view all the answers

    In the context of equipment classes, what is meant by 'single failure criteria'?

    <p>Any active or static component that may cause immediate impact on position keeping.</p> Signup and view all the answers

    Which of the following components would classify as normally static and potentially affect position keeping?

    <p>Cables and pipes</p> Signup and view all the answers

    What does the phrase 'six degrees of freedom' refer to in maritime movement?

    <p>The range of motion involving translations and rotations.</p> Signup and view all the answers

    What factors influence the choice of reference systems in a dynamic positioning system?

    <p>The level of risk associated with the operation</p> Signup and view all the answers

    Which of the following is NOT a commonly used reference system in dynamic positioning?

    <p>GPS</p> Signup and view all the answers

    What is the primary function of heading sensors in dynamic positioning systems?

    <p>To determine the ship's motion parameters and course</p> Signup and view all the answers

    Which type of sensor measures movements in the vertical plane for stabilization purposes?

    <p>Attitude sensor</p> Signup and view all the answers

    What is an advantage of pendulum devices when used in dynamic positioning systems?

    <p>Low cost</p> Signup and view all the answers

    Which disadvantage is associated with pendulum devices in dynamic positioning systems?

    <p>Poor performance under marine dynamics</p> Signup and view all the answers

    What improves the performance of pendulum devices in dynamic positioning systems?

    <p>Implementing them in a dampened environment</p> Signup and view all the answers

    Which of the following sensors can provide additional heading data in DP systems?

    <p>Satellite compasses</p> Signup and view all the answers

    What are the disadvantages of using a pick up coil in a VRU?

    <p>Size and handling restrictions, life cycle costs, installation difficulties, latency</p> Signup and view all the answers

    Which of these is NOT a disadvantage of using VRU with solid state inertial sensors?

    <p>Good accuracy for GPS and Acoustic Stabilization, range of performance / price sensors available, relatively low cost</p> Signup and view all the answers

    What is an advantage of using a VRU with GPS?

    <p>Heading and Position Information, Good Accuracy</p> Signup and view all the answers

    Which of these is a disadvantage of using a VRU with GPS?

    <p>Heading is GPS dependent, relatively high cost</p> Signup and view all the answers

    What are the two main types of anemometers mentioned?

    <p>Mechanical and ultrasonic</p> Signup and view all the answers

    What are the possible wind speeds and direction errors in an anemometer?

    <p>The anemometer could be affected by the wind direction and speed, as well as the location and the direction of the ship.</p> Signup and view all the answers

    Which of the following is NOT a factor that can potentially distort wind measurements from an anemometer?

    <p>The color of the anemometer</p> Signup and view all the answers

    What are the two main types of waves sensors mentioned?

    <p>Hydrometeorological buoys and logs</p> Signup and view all the answers

    What are the two types of current sensors mentioned?

    <p>Hydrometeorological buoys and logs</p> Signup and view all the answers

    Which of the following are not the main source used for ships’ speed, according to the text?

    <p>Depth sensors</p> Signup and view all the answers

    When were microprocessors first used in DP systems?

    <p>Since 1980</p> Signup and view all the answers

    What type of technology was used in the first DP systems?

    <p>Analogue techniques</p> Signup and view all the answers

    Which of these is NOT mentioned as a factor influencing the accuracy of wind measurements from an anemometer?

    <p>The color of the anemometer</p> Signup and view all the answers

    What is the primary benefit of using digital techniques over analogue techniques in DP systems?

    <p>Digital techniques are more reliable than analogue techniques</p> Signup and view all the answers

    Which of these is a possible benefit of using a VRU with solid state inertial sensors over a pick-up coil VRU (select all that apply)?

    <p>Lower cost</p> Signup and view all the answers

    Study Notes

    Dynamic Positioning (DP) Systems

    • DP is a vessel capability to maintain its position automatically using its propulsion system
    • A DP system is a hydrodynamic system that controls or maintains the vessel's position and heading
    • Dynamically positioned vessel (DP vessel) means a vessel that automatically maintains its position and/or heading (fixed location, relative location or predetermined track) using thruster force
    • DP systems are strongly linked to the development of the oil industry in sea areas

    History of DP Systems

    • 19th century: First oil well in the Caspian Sea, 30m from shore, using wooden pier
    • 1925 Caspian Sea: First self-elevating drilling and production platforms ("Jack-up" type), operating in waters up to 60m deep
    • Vessels stabilized position using anchor ropes, enabling drilling and exploitation of wells up to 600m deep
    • 1960 California: CUSS (Continental, Union, Shell & Superior oil consortium) attempted core drilling at 180m water depth and up to 3500m
    • Equipment included four azimuth thrusters, manual control, visual observations, and sonar tracking
    • 1961 USA: Launching of the first drilling vessel with fully functional automatic DP system (Eureka) for Shell, drilling at depths up to 1300 meters. Wave up to 6 meters, wind up to 21 m/s.
    • 1963 France: Launching of two DP ships (Salvor and Terebel) intended for laying pipelines on the seabed and securing underwater works
    • 1964 USA: Launching of DP vessel Caldrill (Caldrill Offshore Company), drilling up to 2000 meters
    • 1971 UK: British GEC Electrical Projects Ltd. constructed first DP systems
    • 1974 UK: Conversion of commercial ship Wimpey Sealab into a drilling vessel for hard coal deposits
    • 1977 UK: Launching of the first semi-submersible drilling rig (Uncle John)
    • 1975 Norway: First research on DP systems at the request of Stolt Nielsen by Kongsberg Vapenfabrikk (KV)
    • 1977 Norway: Launching of Seaway Eagle, the first vessel with the Norwegian DP system

    DP Vessel Applications

    • Diving Support Vessels
    • Pipelay Vessels
    • ROV Support Vessels
    • Crane Vessels
    • Float-over Vessels
    • Accommodation Vessels
    • Drilling Vessels
    • FPSO Vessels
    • Shuttle Tankers
    • Trenching Vessels
    • Cable Lay/Repair Vessels
    • Jack-up Vessels
    • Offshore Supply Vessels
    • Anchor Handling Vessels/Tug
    • Well Stimulation Vessels
    • Rock Placement Vessels
    • Dredging Vessels

    DP System Classes

    • DP equipment class 1: A single fault may lead to a loss of position and/or heading
    • DP equipment class 2: A single fault within any active component or system does not lead to a loss of position/heading. Common static components are accepted, as long as there's adequate protection for failure and is documented
    • DP equipment class 3: A single fault or failure does not lead to a loss of position/heading. This includes components listed in class 2 and components and systems in a single compartment or fire sub-division. All components/systems potentially affected by fire or flooding need to meet the requirements of class 2.

    Degrees of Freedom

    • A ship's motion at sea, described as six degrees of freedom:
      • Translations: Surge (forward/backward), Sway (left/right), Heave (up/down)
      • Rotations: Roll (side-to-side), Pitch (forward/backward), Yaw (left/right turn)

    Main Principles of Operation

    • Forces affecting seagoing vessels: wind, waves, currents, and propulsion
    • DP systems measure deviations between desired and actual positions
    • Forces are calculated to counteract deviations, to maintain stability
    • Mathematical models describe how vessels react to external forces (wind, waves, currents) such as mass and drag
    • Kalman filtering technique helps continuously correct models, improving accuracy
    • Input data compares predicted position/heading to actual values, adjusting the model.
    • DP system components: power supply, thrusters, reference systems, sensors, control systems, steering console, and operator

    DP Construction Components

    • Power supply system (high flexibility due to potential sudden changes in demand)
    • Thruster system:
      • Propellers (often Controllable Pitch Propellers - CPP)
      • Rudders (modified steering gear, e.g., Becker, Schilling rudders, Kort nozzles)
      • Manoeuvring thrusters (transverse propulsion units fitted to ship bow or stern)
      • Azimuth thrusters (propellers with rotatable units)
      • Azipod thrusters (thrusters with propeller housed in pod units)
      • Voith-Schneider thrusters (axial thrusters)
    • Reference systems (high accuracy, reliability, and continuity)
      • Mechanical systems
      • Taut wires
      • Microwave systems (e.g., Artemis, RADius, RadaScan, Miniranger, Trispondeur)
      • Laser systems (e.g., Fanbeam, CyScan)
      • Differential satellite
      • Hydroacoustic
    • Sensors: Measuring devices to determine ship motion, course and external factors:
      • Heading sensors (gyrocompasses, satellite compasses)
      • Attitude sensors (pendulum devices, fluid-stabilized devices, VRUs/GPS)
      • Anemometers (Mechanical, ultrasonic)
      • Wave sensors (hydrometeorological buoys)
      • Current sensors (logs)
      • Draft sensors (ships' speed, additional sensors)
    • Control system (analogue or digital techniques)
    • Steering console
    • Operator

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    Dynamic Positioning (DP) Systems PDF

    Description

    Explore the critical components and functionalities of Dynamic Positioning (DP) systems through this quiz. Test your knowledge on how these systems maintain position, utilize mathematical models, and employ various thrusters and filters. Ideal for engineering students and professionals in marine technology.

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