Abstract: A converter control arrangement (18) for regulating the output current of a dc source power converter (16) comprises a current regulator (20) for regulating the output current based on a comparison of an output current value (Iout) of the dc source power converter (16) with a desired target current value (Itgt). When the output voltage value (Vout) of the dc source power converter (16) is within a normal operating voltage range between minimum and maximum voltage values (Vmin, Vmax) defined with respect to a voltage reference value (Vref) of the dc source power converter (16), the converter control arrangement (18) controls the target current value (Itgt) so that it is equal to a desired reference current value (Iref).

Abstract: A data fusion architecture with a plurality of sensors, optionally position measuring equipment (PMEs), is described. Each sensor supplies measurement data x1, x2 . . . xM and is associated with accuracy data H1, H2 . . . HM indicative of the accuracy of the supplied measurement data. Sub-processing units derives first estimates sf1, sf2 . . . sfM and second estimates Hn1, Hn2 . . . HnM of the variability of the measurement data supplied by the respective sensor. The first estimates are derived by processing the measurement data x1, x2 . . . xM and the second estimates are derived by processing the accuracy data H1, H2 . . . HM. The first and second estimates are combined in a multiplier to derive overall estimates ?1, ?2 . . . ?M of the variability of the measurement data supplied by the respective sensor. Data fusion means such as a Kalman filter combines the measurement data supplied by each sensor and the overall estimates ?1, ?2 . . . ?M for each sensor.

Abstract: A method of operating a dual fed system is described where power is supplied to a electrical load from first and second ac busbars at a ratio that achieves a desired level of exhaust emissions such as nitrogen oxides (NOx), carbon dioxide (CO2) and other pollutants produced by the prime movers associated with generators. Preferably, the method may be used to operate a dual fed marine propulsion system wherein the electrical load is a thruster. Operating a dual fed marine propulsion system using the method of the present invention makes it possible to optimize thrust allocation between thrusters in a way that is similar to that used in conventional dynamic positioning (DP) systems and then share or allocate the required power between generators to minimize exhaust emissions.

Abstract: A system for minimizing fuel consumption in a dynamic positioning (DP) vessel comprising a measurement system, an observer system, a control system and a thruster system. The heading of the vessel is adjusted to minimize the environmental forces felt on each side of the vessel. The method also allows for operator input to offset the vessel heading to improve comfort on board.

Abstract: Dynamic positioning systems and methods for controlling thrusters of a vessel. A dynamic positioning system includes a controller configured to predict position and heading of the vessel and efficiently control the the thrusters based on the predicted position and heading.

Abstract: The present invention provides an improved architecture for integrating an inertial navigation system (INS) into a dynamic positioning (DP) system for a vessel. The architecture includes an INS unit and a DP system having a Kalman filter or other algorithm for combining data supplied by a plurality of position measuring equipment (PME) and the INS unit to derive an estimate of the position or speed of the vessel. A switch array and a switch array controller are also provided. These may optionally form a part of the DP system. The switch array is operable under the control of the switch array controller to supply data supplied by one or more of the plurality of position measuring equipment to the INS unit for the purposes of correcting drift. The selection of which of the one or more PME is/are to be combined with the INS unit is made automatically, in real time, to dynamically optimise the DP system.

Abstract: Dynamic positioning systems and methods for controlling thrusters of a vessel. A dynamic positioning system includes a controller configured to predict position and heading of the vessel and efficiently control the the thrusters based on the predicted position and heading.

Abstract: A taut cable with a fiber optic cable with Bragg diffusion gratings allows a suitable driver circuit to determine the shape of the taut cable at a large number of points along its length. This enables the total 3-dimensional shape of the taut cable to be estimated and from which the position of the vessel relative to a seabed weight attached to the taut cable can be inferred.

Abstract: A method of estimating the environmental force acting on a supported jack-up vessel is described. The vessel is positioned in a force determination position and the strain on at least one support leg of the jack-up vessel is measured while a first thrust is applied to the vessel. A second thrust is applied to the vessel while the vessel is maintained in the force determination position. The variation in the strain in the at least one support leg is monitored as the second thrust is applied and the strain is used to calculate an estimate of the environmental force acting on the vessel. The method allows a dynamic positioning (DP) system of the jack-up vessel to determine a suitable thrust to apply to the vessel as the support legs of the vessel are raised. By applying this suitable thrust the position of the vessel can be maintained when the vessel transitions from being supported by the support legs to being supported by water.

Abstract: A method of operating a dual fed system is described where power is supplied to a electrical load from first and second ac busbars at a ratio that achieves a desired level of exhaust emissions such as nitrogen oxides (NOx), carbon dioxide (CO2) and other pollutants produced by the prime movers associated with generators. Preferably, the method may be used to operate a dual fed marine propulsion system wherein the electrical load is a thruster. Operating a dual fed marine propulsion system using the method of the present invention makes it possible to optimise thrust allocation between thrusters in a way that is similar to that used in conventional dynamic positioning (DP) systems and then share or allocate the required power between generators to minimise exhaust emissions.

Abstract: The present invention provides a method of controlling the position of a spread moored marine vessel (1). In particular, the method of the present invention substantially maintains the position of a spread moored vessel (1) in, or on the boundary of a target area (2) using thruster assistance. This is done by monitoring the position of the vessel and when the vessel (1) is positioned outside of the target area (2) applying a position correcting thrust (7) to the vessel (1) in the direction of an aim position located on the boundary of the target area (2) and when the vessel (1) is positioned within the target area (2) reducing the position correcting thrust (7) applied to the vessel (1) or maintaining the position correcting thrust (7) applied to the vessel (1) at zero. The present invention may also apply a damping thrust (7) to the vessel (1) in order to damp the positional variation of the vessel (1).

Abstract: A method of estimating the environmental force acting on a supported jack-up vessel is described. The vessel is positioned in a force determination position and the strain on at least one support leg of the jack-up vessel is measured while a first thrust is applied to the vessel. A second thrust is applied to the vessel whilst the vessel is maintained in the force determination position. The variation in the strain in the at least one support leg is monitored as the second thrust is applied and the strain is used to calculate an estimate of the environmental force acting on the vessel. The method allows a dynamic positioning (DP) system of the jack-up vessel to determine a suitable thrust to apply to the vessel as the support legs of the vessel are raised. By applying this suitable thrust the position of the vessel can be maintained when the vessel transitions from being supported by the support legs to being supported by water.

Abstract: A data fusion architecture with a plurality of sensors, optionally position measuring equipment (PMEs), is described. Each sensor supplies measurement data x1, x2 . . . xM and is associated with accuracy data H1, H2 . . . HM indicative of the accuracy of the supplied measurement data. Sub-processing units derives first estimates sf1, sf2 . . . sfM and second estimates Hn1, Hn2 . . . HnM of the variability of the measurement data supplied by the respective sensor. The first estimates are derived by processing the measurement data x1, x2 . . . xM and the second estimates are derived by processing the accuracy data H1, H2 . . . HM. The first and second estimates are combined in a multiplier to derive overall estimates ?1, ?2 . . . ?M of the variability of the measurement data supplied by the respective sensor. Data fusion means such as a Kalman filter combines the measurement data supplied by each sensor and the overall estimates ?1, ?2 . . . ?M for each sensor.

Abstract: A converter control arrangement (18) for regulating the output current of a dc source power converter (16) comprises a current regulator (20) for regulating the output current based on a comparison of an output current value (Iout) of the dc source power converter (16) with a desired target current value (Itgt). When the output voltage value (Vout) of the dc source power converter (16) is within a normal operating voltage range between minimum and maximum voltage values (Vmin, Vmax) defined with respect to a voltage reference value (Vref) of the dc source power converter (16), the converter control arrangement (18) controls the target current value (Itgt) so that it is equal to a desired reference current value (Iref).

Abstract: A fault detection method uses inertial measurements provided by an inertial measurement unit (IMU) (2) to detect faults in position measurement equipment (PME) (4). The method uses at least one inertial measurement (a(t?N) . . . a(t)) to derive at least one unaided marine vessel state estimate (x(t?N) . . . x(t)) in an unaided solution function block (12). This is then compared with at least one position measurement (p(t?N) . . . p(t)) provided by the PME (4) in a fault detection function block (14) to determine if there is a fault in the PME. An earlier inertial measurement (a(t?N+1)) and an earlier position measurement (p(t?N+1)) are used to derive an aided marine vessel state estimate (x?(t?N+1)) in an aided solution function block (10). The aided marine vessel state estimate (x?(t?N+1)) is used as a start condition to the step of deriving the at least one unaided marine vessel state estimate (x(t?N) . . . x(t)). The aided and unaided solution function blocks (10, 12) can be implemented as a Kalman filter.

Abstract: The present invention provides a method of controlling the position of a spread moored marine vessel (1). In particular, the method of the present invention substantially maintains the position of a spread moored vessel (1) in, or on the boundary of a target area (2) using thruster assistance. This is done by monitoring the position of the vessel and when the vessel (1) is positioned outside of the target area (2) applying a position correcting thrust (7) to the vessel (1) in the direction of an aim position located on the boundary of the target area (2) and when the vessel (1) is positioned within the target area (2) reducing the position correcting thrust (7) applied to the vessel (1) or maintaining the position correcting thrust (7) applied to the vessel (1) at zero. The present invention may also apply a damping thrust (7) to the vessel (1) in order to damp the positional variation of the vessel (1).

Abstract: The present invention provides an improved architecture for integrating an inertial navigation system (INS) into a dynamic positioning (DP) system for a vessel. The architecture includes an INS unit and a DP system having a Kalman filter or other algorithm for combining data supplied by a plurality of position measuring equipment (PME) and the INS unit to derive an estimate of the position or speed of the vessel. A switch array and a switch array controller are also provided. These may optionally form a part of the DP system. The switch array is operable under the control of the switch array controller to supply data supplied by one or more of the plurality of position measuring equipment to the INS unit for the purposes of correcting drift. The selection of which of the one or more PME is/are to be combined with the INS unit is made automatically, in real time, to dynamically optimise the DP system.

Abstract: Dynamic positioning of a vessel 10 connected to the seafloor 14 by a riser 12 utilizes a measurement of riser 12 bottom angle combined with a measurement of vessel 10 velocity, optionally obtained from a Doppler log 16. These two signals are combined to produce a single position estimate using an algorithm such as a Kalman filter. Using riser bottom angle only would result in an unstable control system, since the bottom angle lags the vessel motion by a considerable amount and the relationship is non-linear. Using the velocity measurement alone would result in a slow drift of position. The combination of the two eliminates the disadvantages of the individual measurements.

Abstract: Dynamic positioning of a vessel 10 connected to the seafloor 14 by a riser 12 utilises a measurement of riser 12 bottom angle combined with a measurement of vessel 10 velocity, optionally obtained from a Doppler log 16. These two signals are combined to produce a single position estimate using an algorithm such as a Kalman filter. Using riser bottom angle only would result in an unstable control system, since the bottom angle lags the vessel motion by a considerable amount and the relationship is non-linear. Using the velocity measurement alone would result in a slow drift of position. The combination of the two eliminates the disadvantages of the individual measurements.