Patent Description:
Most marine hybrid systems use a control strategy based on power demand, which demand is controlled by an operator. For marine vessels comprising multiple drivelines the power demand is distributed equally between all drivelines and the internal combustion engines and electric motors in each driveline are operated individually or together, depending on factors such as the magnitude of the power demand and/or the charge level, or state of charge (SOC), of the electrical storage units.

Marine hybrid systems having a control strategy based on power demand and automatic hybrid functionality may attempt to control the internal combustion engines to operate at or near optimum efficiency. However, the power demand, and thus the rotational speed of the propulsion units, is controlled by the operator. Consequently, optimum efficiency operation of the internal combustion engines is often not possible and may be achieved at the expense of inefficient operation of the electrical motors.

The invention provides an improved method for controlling marine hybrid systems and aims to solve the above-mentioned problems. Prior art methods for controlling marine hybrid systems are disclosed in <CIT>, <CIT> and <CIT>.

An object of the invention is to provide a method for controlling marine hybrid systems and a marine hybrid system, which solves the above-mentioned problems.

The object is achieved by a method according to claim <NUM>.

In the subsequent text, the term "driveline" is used to describe an installation comprising a combination of propulsion units. Such a driveline is preferably a parallel hybrid driveline. Examples of propulsion units are internal combustion engines (ICE) and electric motors (EM). Each driveline is arranged to drive a propeller shaft provided with one or more propellers. The electric motors can be powered by a common electrical storage unit or by individual electrical storage units for each electric motor. The electrical storage units can also be referred to as batteries. The internal combustion engines are operated at a requested or determined engine speed. In the subsequent text, the term engine speed can also be referred to as the rotational speed of the first propulsion unit. A suitable reduction gearing, or another suitable transmission is provided to reduce the engine speed to a lower rotational output to a propeller shaft. The location of the reduction gearing can be dependent on the type of electric motor used. The reduction gearing can for instance be arranged adjacent the output shaft of the electric motor, if the propulsion units are operated at the same rotational speed. Alternatively, the reduction gearing can be arranged adjacent the output shaft of the internal combustion engine, wherein the electric motor is rotated at the rotational output speed of a propeller shaft. These terms will be adhered to in the subsequent text.

According to one aspect of the invention, the object is achieved by means of a method to control at least a first and a second parallel hybrid driveline arranged to drive a marine vessel. Each driveline comprises a first propulsion unit in the form of an internal combustion engine operatively connected with a second propulsion unit in the form of an electric motor to drive a propeller shaft and produce a thrust force for propelling the vessel. An alternative arrangement can be to use a driveline comprising two first propulsion units and two second propulsion units operatively connected to a single propeller shaft. In the subsequent text, the term "first propulsion unit" is used to indicate an internal combustion engine (ICE) and the term "second propulsion unit" is used to indicate an electric motor (EM). The internal combustion engine is operatively connected to the electric motor via a driveshaft, which driveshaft can comprise an optional controllable clutch. At least one control unit is arranged for individual control of each first and second propulsion unit in all the parallel hybrid drivelines. All parallel hybrid drivelines can be controlled by a central driveline control unit controlling each internal combustion engine and electric motor in the respective drivelines. Alternatively, individual control units can be provided for each internal combustion engine and each electric motor in the respective parallel hybrid driveline. According to a further alternative, a central driveline control unit can be used in combination with individual control units for each propulsion unit. Transmission and exchange of data between control units can be made using a Controller Area Network (CAN bus), Local Area Network (LAN) or a similar wired connection, or by using a suitable Wireless Local Area Network (WLAN) or other wireless technology such as WiFi or Bluetooth.

The method involves performing the steps of:.

wherein the individual drivelines are controlled by exchanging data required for controlling the propulsion units between a central control unit and the drivelines or between individual control units for each driveline so that the combined rotational speed from all first propulsion units is sufficient for maintaining the requested vessel speed, and adjusting the rotational speed of at least one first propulsion unit and allowing it to be operated at a different rotational speed than at least one other first propulsion unit.

A request indicative of a vessel speed can be received from a controller operated by a user, which controller can be a joystick or multiple levers. In operation, the operator requests a vessel speed by actuating the controller to a lever setting between zero and full throttle. The displacement of the lever between these end points will not correspond to a linear increase in actual vessel speed. However, the engine speed will be a linear function the lever displacement, so the displacement of a lever to a particular setting is actually a request for an engine speed corresponding to this setting. Consequently, the user makes a request indicative of a vessel speed and the control unit receives a request for an engine speed.

A controller can be a single joystick controlling all drivelines. The controller can also comprise one or multiple levers for controlling one or more drivelines. For instance, installations comprising two drivelines can have two levers, which can be displaced individually or together. A triple installation can have three levers, wherein a center lever can output a signal representing an average value for an engine speed request. A quad installation can instead use two levers controlling two drivelines each. When requesting a vessel speed, the levers are usually displaced together. An exception to this is of course low speed maneuvering, e.g. a docking maneuver, where individual displacement can be required to achieve a vessel displacement is a desired direction. Allowing each lever to control more than one driveline is preferable for installations having more than four drivelines.

As indicated above, the rotational speed for each first propulsion unit is controlled for achieving the requested vessel speed, based on the received request from the operator. However, if the requested vessel speed is below a predetermined limit for the current rotational speed, then the desired speed can instead be achieved by clutch control. For instance, relatively low maneuvering speeds for docking can be achieved by allowing the clutch to slip while the first propulsion unit is operated at or just above its idling speed. Internal combustion engines and electric motors both have optimum efficiency points in respect to the conversion of energy to mechanical movement. The object of the invention is to balance the combined efficiency mapping between the drivelines to achieve the best possible combined efficiency for all drivelines. The efficiency points for each ICE and EM is determined from efficiency maps stored in the central control unit or in each individual control unit. Examples of efficiency maps will be described in further detail below.

When using a central control unit or multiple control units, data required for controlling the propulsion units is exchanged between a central control unit and the drivelines or between individual control units for each driveline, so that all propulsion units can be operated together. Coordinated control of the propulsion units is primarily performed for maintaining the requested speed. The requirement of maintaining the requested speed necessitates an exchange of data between control units when the rotational speed of the first propulsion unit in each driveline is individually adjusted. According to the invention, the individual drivelines are controlled so that the combined, or average rotational output speed of the propeller shafts for all drivelines is sufficient for maintaining the requested vessel speed. As each of the internal combustion engines are controlled towards a suitable efficiency point, the load from the corresponding electric motor in each driveline is simultaneously adjusted towards a suitable efficiency point. By adjusting the internal combustion engine and the electric motor in each driveline to improve the efficiency of each driveline, the efficiency of the complete driveline installation is improved.

In operation, the rotational speed of the first propulsion unit in a particular driveline is adjusted towards an efficiency point determined from a map for that first propulsion unit. Simultaneously, the second propulsion unit in this driveline is adjusted by reducing or increasing the load from the second propulsion unit onto the first propulsion unit in response to the adjustment of the rotational speed of the first propulsion unit towards the efficiency point. This means that the torque supplied to the driveline from the second propulsion unit can be positive or negative. Hence, if the adjustment of first propulsion unit towards a desired efficiency point requires a reduction of the load then the second propulsion unit can be operated to reduce the load from the second propulsion unit onto the first propulsion unit by providing an assisting, positive driving torque. Similarly, if the adjustment of first propulsion unit towards a desired efficiency point requires an increase of the load then the second propulsion unit can be operated to increase the load from the second propulsion unit onto the first propulsion unit by providing a braking, negative driving torque. Such an adjustment of the load from the second propulsion unit can be achieved by controlling it to charge an electrical storage unit, such as a battery or a supercapacitor.

When operating the second propulsion unit to reduce or increase the load from the second propulsion unit onto the first propulsion unit, the magnitude of the reduction or increase can be selected with respect to a desired efficiency point for the second propulsion unit. The decision to reduce or increase the load can primarily be made dependent on the determined efficiency point for the first propulsion unit and subsequently dependent on the determined efficiency point for the second propulsion unit. Hence, the adjustment of the load from the corresponding second propulsion unit can be weighted to give precedence to the efficiency of the first propulsion unit. However, the adjustment of the load from the corresponding second propulsion unit onto the first propulsion unit can be stopped before the first propulsion unit reaches a desired efficiency point, if the combined efficiency of the driveline reaches a maximum value. Consequently, neither the first nor the second propulsion unit would be operated at their respective desired efficiency points, but the combined efficiency of the driveline is improved. This control of the first and second propulsion units can be performed on at least one driveline in the marine hybrid system.

When adjusting the rotational speed of at least one first propulsion unit, this propulsion unit is allowed to be operated at a different rotational speed than at least one other first propulsion unit in an installation comprising multiple drivelines. Consequently, at least one driveline can be controlled to be operated at a different rotational output speed than one or more additional drivelines. Alternatively, all drivelines can be operated at different rotational output speeds. A prerequisite is that the individual drivelines are controlled so that the combined, or average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed.

As indicted above, it is possible to control the drivelines so that they are operated at different rotational output speeds after having adjusted the rotational speed of each first propulsion unit towards a desired efficiency point. The thrust force of each individual driveline can then produce a combined thrust force directed at an angle to the central longitudinal axis of the vessel when travelling straight ahead. Alternatively, the direction of the combined thrust force can deviate from the desired steering direction requested by the operator. When this condition occurs, a correction of the steering angle of one or more drivelines or steerable propellers is required. For instance, if the vessel comprises two or more parallel hybrid drivelines, then the direction of the combined thrust force can be adjusted by a steering control unit controlling at least one of the drivelines in order to maintain the total thrust force in a desired direction.

Alternatively, it is possible to operate the drivelines to produce a combined thrust force that coincides with the currently requested steered direction. Dependent on the determined efficiency points for each individual driveline, it can be possible to achieve a combined thrust force having a neutral direction by selective adjustment of the drivelines making up the installation. In installations comprising three or more drivelines, it can be possible to operate drivelines in pairs, preferably drivelines located at equal distances from the central longitudinal axis of the vessel. According to a first example, the vessel comprises three parallel hybrid drivelines, wherein the drivelines located on either side of a central driveline are operated at a different rotational output speed than the central driveline. According to a second example, the vessel comprises four parallel hybrid drivelines, wherein the drivelines located on either side of a pair of central drivelines are operated at a different rotational output speed than the central drivelines. This principle of selecting pairs of symmetrically located drivelines operated at the same rotational output speed will balance the combined thrust force can be applied to installations comprising three or more drivelines.

According to a further example, if the vessel comprises two or more parallel hybrid drivelines, at least one driveline can be stopped if the rotational output speed of the remaining driveline or drivelines is sufficient for maintaining the requested vessel speed.

According to a second aspect of the invention, the object is achieved by a control unit according to claim <NUM>.

According to a third aspect of the invention, the object is achieved by a marine vessel according to claim <NUM>.

According to a further aspect of the invention, the object is achieved by a computer program according to claim <NUM>.

According to a further aspect of the invention, the object is achieved by a computer program product according to claim <NUM>.

The invention involves adjusting the internal combustion engine and the electric motor in each driveline to improve the efficiency of each driveline. An effect of this is that the efficiency of the complete driveline installation is improved. By using the fact that the installation has more than one driveline with separate battery banks the load can be balanced between the drivelines to achieve the best possible efficiency. Instead of only considering the efficiency map of each ICE, the efficiency maps of each ICE and the corresponding EM is considered when using the electric motor to place the load at the best place along the load axis of the ICE efficiency map. This is achieved by both balancing the load on the respective ICE using the electric motors and balancing the rotational speeds of the ICE:s between the drivelines. Balancing the rotational speed can involve increasing the rotational speed on one or more drivelines and decreasing the rotational speed on one or more other drivelines. In this way, the vessel speed requested by the operator can be maintained, while the freedom to run the engines and motors at a better speed/load combination.

<FIG> shows a schematically illustrated vessel <NUM> comprising a marine hybrid installation according to the invention. The hybrid installation in this figure comprises a first and a second parallel hybrid driveline <NUM>, <NUM> arranged to drive the vessel <NUM> via a first and second drives <NUM>, <NUM> mounted on the vessel transom <NUM>. Each driveline <NUM>, <NUM> comprises a first propulsion unit <NUM>, <NUM> in the form of an internal combustion engine (ICE) operatively connected with a second propulsion unit <NUM>, <NUM> in the form of an electric motor (EM) to drive a propeller shaft <NUM>, <NUM> and produce a thrust force for propelling the vessel. Each second propulsion unit <NUM>, <NUM> is connected to an individual source of electric power (not shown), such as an electric storage unit or battery.

A request indicative of a vessel speed can be received from an operating station <NUM> by means of a controller <NUM> operated by a user. In this example, multiple levers are used for controlling the driveline speeds. The controller can also be a joystick. The operating station <NUM> also comprises a steering wheel <NUM> for controlling the steered direction, a joystick <NUM> for operating the vessel during docking, and a display <NUM>. The display <NUM> can be used for providing the operator with vessel and driveline related operating parameters, and/or for showing navigational information. The display can be a graphical user interface (GUI) and can be touch-sensitive. Control signals relating to propulsion and steering are transmitted from the operating station <NUM> to a corresponding propulsion control unit (see <FIG>) and a steering control unit (not shown) via a CAN bus <NUM>. As indicated in <FIG>, more than one operating station can be provided.

<FIG> show schematically illustrated vessels with alternative driveline installations. <FIG> shows a vessel comprising two stern drives driven by parallel hybrid drivelines. However, the invention is applicable to other drives as indicated in <FIG>, showing multiple azimuthing drives.

<FIG> shows a vessel comprising two parallel hybrid drivelines <NUM>, <NUM>, wherein each driveline <NUM>, <NUM> is provided with a first propulsion unit <NUM>, <NUM> in the form of an internal combustion engine (ICE) operatively connected with a second propulsion unit <NUM>, <NUM> in the form of an electric motor (EM).

<FIG> shows a vessel comprising three parallel hybrid drivelines <NUM>, <NUM>, <NUM>, wherein each driveline <NUM>, <NUM>, <NUM> is provided with a first propulsion unit <NUM>, <NUM>, <NUM> in the form of an internal combustion engine (ICE) operatively connected with a second propulsion unit <NUM>, <NUM>, <NUM> in the form of an electric motor (EM).

<FIG> shows a vessel comprising four parallel hybrid drivelines <NUM>, <NUM>, <NUM>, <NUM>, wherein each driveline <NUM>, <NUM>, <NUM>, <NUM> is provided with a first propulsion unit <NUM>, <NUM>, <NUM>, <NUM> in the form of an internal combustion engine (ICE) operatively connected with a second propulsion unit <NUM>, <NUM>, <NUM>, <NUM> in the form of an electric motor (EM).

The invention is not limited to the examples shown in <FIG>, but is applicable to any suitable driveline installation comprising multiple hybrid drivelines. The number of drivelines used is commonly decided by the size and speed requirements for each vessel. Consequently, relatively small vessels can use two hybrid drivelines as shown in <FIG>, while relatively large vessels can use up to seven or eight drivelines.

<FIG> shows a schematic illustration of a parallel hybrid driveline installation comprising three drivelines. The installation comprises a first, a second and a third parallel hybrid driveline <NUM>, <NUM>, <NUM> arranged to drive a marine vessel. Each driveline comprises a first propulsion unit <NUM>, <NUM>, <NUM> in the form of an internal combustion engine (ICE) operatively connected with a second propulsion unit <NUM>, <NUM>, <NUM> in the form of an electric motor (EM) to drive a propeller shaft <NUM>, <NUM>, <NUM> and produce a thrust force for propelling the vessel. Each first propulsion unit <NUM>, <NUM>, <NUM> is operatively connected to a respective second propulsion unit <NUM>, <NUM>, <NUM> via a driveshaft <NUM>, <NUM>, <NUM>, which driveshaft can comprise an optional controllable clutch <NUM>, <NUM>, <NUM>. A suitable reduction gearing or transmission (not shown) is provided adjacent the output shaft of each second propulsion unit. The reduction gearing is arranged to reduce the rotational speed of the propulsion units to a lower rotational output speed for the propeller shaft. Each second propulsion unit <NUM>, <NUM>, <NUM> is connected to an individual source of electric power (not shown), such as an electric storage unit or battery. Control units <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM> is arranged for individual control of each first and second propulsion unit <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, respectively, in all the parallel hybrid drivelines. All parallel hybrid drivelines <NUM>, <NUM>, <NUM> are controlled by a central driveline control unit <NUM> communicating with and controlling each first and second propulsion unit in the respective drivelines. Each driveline <NUM>, <NUM>, <NUM> further comprises a controllable clutch <NUM>, <NUM>, <NUM> on their respective propeller shaft <NUM>, <NUM>, <NUM>, allowing the central driveline control unit <NUM> to control the thrust force from each driveline <NUM>, <NUM>, <NUM>.

An operating station <NUM> comprises a driveline speed controller <NUM> operated by a user. In this example, multiple levers are used for controlling the driveline speeds. The operating station <NUM> also comprises a steering wheel <NUM> for controlling the steered direction, a joystick <NUM> for operating the vessel during docking, and a display <NUM>. The display <NUM> can be used for providing the operator with vessel and driveline related operating parameters, and/or for showing navigational information. The display can be a graphical user interface (GUI) <NUM> and can be touch-sensitive. Signals from the speed controller <NUM>, the steering wheel <NUM>, joystick <NUM> and the graphical user interface <NUM> are processed by a helm control unit <NUM>, which in turn generates control signals to a steering controller (not shown) and the central driveline control unit <NUM>. Control signals are transmitted from the operating station <NUM> to the central driveline control unit <NUM> and the steering control unit (not shown) via a CAN bus <NUM>. The CAN bus <NUM> also connects the central driveline control unit <NUM> and the individual control units <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM> for the first and second propulsion units. Alternatively, transmission and exchange of data between the control units can be made using a Local Area Network (LAN) or a similar wired connection, or by using a suitable Wireless Local Area Network (WLAN) or other wireless technology such as WiFi or Bluetooth.

<FIG> shows an example of an efficiency map for an internal combustion engine. The efficiency map is a diagram indicating engine torque (Nm) plotted on the y-axis over engine speed (rpm) plotted on the x-axis. The contour lines show the specific fuel consumption (g/kWh), indicating the areas of the speed/load regime where the engine is more or less efficient. In the diagram, it is desirable to operate an engine within contour lines having lower values for specific fuel consumption. An upper line delimiting the plotted contour lines indicates the maximum engine torque that the engine can achieve for different engine speeds.

<FIG> shows an example of an efficiency map for an electric motor. The efficiency map is a diagram indicating motor torque (Nm) plotted on the y-axis over motor speed (rpm) plotted on the x-axis. The contour lines show the motor efficiency (dimensionless), indicating the areas of the speed/load regime where the motor is more or less efficient in converting electrical power to mechanical power. In the diagram, it is desirable to operate an electric motor within a contour line having higher values for efficiency.

The following example is described with reference to a marine vessel with an installation comprising a first and a second hybrid driveline. Each hybrid driveline comprises a first propulsion unit in the form of an internal combustion engine, and a second propulsion unit in the form of an electric motor. Efficiency maps for the engine and the motor are stored in a central control unit or in individual control unit for the respective propulsion unit.

In operation, the internal combustion engines in both drivelines are initially operated at a requested engine speed n<NUM>, indicated at the point P<NUM> in <FIG>. In order to improve the efficiency of the installation, the rotational speed of the first propulsion unit in the first hybrid driveline is adjusted towards a first efficiency point P<NUM>, which point is determined from a stored engine efficiency map for the first propulsion unit. The direction of the adjustment is indicated by an arrow A<NUM>. This adjustment involves a reduction of the engine speed of the first propulsion unit from the requested engine speed n<NUM> to a lower, first engine speed n<NUM>. To achieve this, the second propulsion unit in the first hybrid driveline is adjusted by increasing the load from the second propulsion unit onto the first propulsion unit in response to the required lowering of the rotational speed of the first propulsion unit.

This is shown in <FIG>, where the second propulsion unit is adjusted from an initial motor speed n<NUM> at an initial operating point E<NUM>, where no torque is generated, to a first motor speed n<NUM> at a first operating point E<NUM>, where a negative, braking torque is generated. The initial motor speed n<NUM> is equal to the initial engine speed n<NUM> of the first propulsion unit. The direction of the adjustment is indicated by an arrow B<NUM>. This negative torque increases the load from the second propulsion unit onto the first propulsion unit, which second propulsion unit is now being operated at a motor speed n<NUM> equal to the rotational speed of the first propulsion unit.

Simultaneously, the rotational speed of the first propulsion unit in the second hybrid driveline is adjusted towards a second efficiency point P<NUM>, which point is determined from a stored efficiency map for this first propulsion unit. The direction of the adjustment is indicated by an arrow A<NUM>. The adjustment involves an increase of the engine speed of the first propulsion unit from the requested engine speed n<NUM> to a higher, second engine speed n<NUM>. At the same time, the second propulsion unit in the second hybrid driveline is adjusted by increasing the load from the second propulsion unit onto the first propulsion unit in response to the required increase of the rotational speed of the first propulsion unit. This is shown in <FIG>, where the second propulsion unit is adjusted from an initial motor speed n<NUM> at the initial operating point E<NUM>, where no torque is generated, to a second motor speed n<NUM> at a second operating point E<NUM>, where a negative, braking torque is generated. The direction of the adjustment is indicated by an arrow B<NUM>. This negative torque increases the load from the second propulsion unit on the first propulsion unit which is now being operated at a motor speed n<NUM> corresponding to the rotational speed of the first propulsion unit. The operation of the second propulsion units to provide a braking, negative driving torque can be achieved by controlling the second propulsion units to charge their respective electrical storage units, such as a battery or a supercapacitor.

When adjusting the rotational speed of the first propulsion units of the respective drivelines, the propulsion units are allowed to be operated at a different rotational speeds n<NUM>, n<NUM>. The rotational speed n<NUM>, n<NUM> of the respective first propulsion unit is controlled so that the combined, or average rotational speed from all first propulsion unit corresponds to the initially requested rotational speed n<NUM> for all first propulsion units. This will provide a combined rotational output speed from all drivelines required for maintaining the requested vessel speed.

<FIG> show examples of thrust force distribution for a number of alternative driveline installations. According to the invention, it is possible to control the drivelines so that they are operated at different rotational output speeds after adjustment of the rotational speed of each first propulsion unit towards a desired efficiency point.

<FIG> shows an example of thrust force distribution for installations comprising two drivelines. <FIG> shows a vessel <NUM> comprising two parallel hybrid drivelines <NUM>, <NUM>. According to this example, a first propulsion unit in a first driveline <NUM> has been adjusted towards a desired efficiency point, which adjustment has required a reduction of the rotational speed for the first propulsion unit and an increase of the load from the second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the first driveline <NUM>. The speed reduction has resulted in a reduced first thrust force F<NUM>, indicated by an arrow in <FIG>. Simultaneously, a first propulsion unit in a second driveline <NUM> has also been adjusted towards the desired efficiency point, which adjustment has required an increase of the rotational speed for the first propulsion unit and an increase of the load from the second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the second driveline <NUM>. The speed increase has resulted in an increased second thrust force F<NUM>, indicated by an arrow in <FIG>. From <FIG> it can be seen that the magnitude of the thrust force F<NUM> from the second driveline <NUM> is greater than that of the thrust force F<NUM> from the first driveline <NUM>. This will cause a turning moment about the center of gravity CG of the vessel <NUM>, which must be compensated for in order to prevent a deviation from the steered direction requested by the operator. The turning moment can be eliminated by a correction of the steering angle α<NUM> and/or α<NUM> of the first driveline <NUM> and the second driveline <NUM>, respectively. Such a correction can be performed by a steering control unit (not shown) in the same way as such a unit performs a correction for sideways drift caused by wind or currents. Steering control units of this type will not be described in further detail here. In this way the direction of the combined thrust force comprising the first thrust force F<NUM> and the second thrust force can be adjusted by the steering control unit in order to maintain a total thrust force F<NUM> in a desired direction. In addition, as the thrust forces are proportional to the rotational output speed of the respective first and second driveline, the individual drivelines are controlled so that the average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed. If the steering angle of one or more drivelines is corrected as indicated above, then an increase of rotational output speed can be required for one or both drivelines for maintaining the requested vessel speed. Alternatively, if the vessel is provided with a steerable rudder and fixed drive units, then the rudder can be used to compensate for the deviation from the steered direction.

<FIG> shows an example of thrust force distribution for installations comprising three drivelines. <FIG> shows a vessel <NUM> comprising three parallel hybrid drivelines <NUM>, <NUM>, <NUM>. According to this example, a first propulsion unit in a first driveline <NUM> and a third driveline <NUM> have been adjusted towards a desired efficiency point, which adjustment has required an increase of the rotational speed for the first propulsion unit and an increase of the load from the second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the first driveline <NUM> and the third driveline <NUM>. The speed increase has resulted in increased first and third thrust forces F<NUM>, F<NUM>, indicated by arrows in <FIG>, which forces are equal in magnitude.

Simultaneously, a first propulsion unit in a second driveline <NUM> has also been adjusted towards the desired efficiency point, which adjustment has required a reduction of the rotational speed for the first propulsion unit and an increase of the load from the second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the second driveline <NUM>. The speed reduction has resulted in a reduced second thrust force F<NUM>, indicated by an arrow in <FIG>. The rotational output speeds of the individual drivelines <NUM>, <NUM>, <NUM> are controlled so that the average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed.

From <FIG> it can be seen that the magnitude of the thrust forces F<NUM>, F<NUM> from the first and third drivelines <NUM>, <NUM> are greater than that of the thrust force F<NUM> from the second driveline <NUM>. As the installation in <FIG> comprises three drivelines, it is possible to operate the first and third drivelines as a pair. According to this example, the first and third drivelines <NUM>, <NUM> are located with equal spacing from the centerline CL of the vessel on either side of the second driveline <NUM> located on the centerline CL. The first and third drivelines <NUM>, <NUM> are operated at the same rotational output speed, which is higher than the rotational output speed of the central second driveline <NUM>. In this way it is possible to operate the drivelines to produce a combined thrust force F<NUM> that is equal to the sum of the individual thrust forces F<NUM>, F<NUM>, F<NUM>, and which coincides with the currently requested steered direction. Dependent on the determined efficiency points for each individual driveline, it is possible to achieve a combined thrust force having a neutral direction by selective adjustment of the drivelines making up the installation.

<FIG> shows an example of thrust force distribution for installations comprising four drivelines. <FIG> shows a vessel <NUM> comprising four parallel hybrid drivelines <NUM>, <NUM>, <NUM>, <NUM>. According to this example, a first propulsion unit in a first driveline <NUM> and a fourth driveline <NUM> have been adjusted towards a desired efficiency point, which adjustment has required an increase of the rotational speed for the first propulsion unit and an increase of the load from the respective second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the first driveline <NUM> and the fourth driveline <NUM>. The speed increase has resulted in increased first and fourth thrust forces F<NUM>, F<NUM>, indicated by arrows in <FIG>, which forces are equal in magnitude.

Simultaneously, a first propulsion unit in a second driveline <NUM> and a third driveline <NUM> have also been adjusted towards the desired efficiency point, which adjustment has required a reduction of the rotational speed for the first propulsion unit and an increase of the load from the respective second propulsion unit (see <FIG>, ref. This increase of the load from the second propulsion unit provides a braking, negative driving torque applied to the first propulsion unit of the second driveline <NUM>. The speed reduction has resulted in reduced second and third thrust forces F<NUM>, F<NUM>, indicated by arrows in <FIG>. The rotational output speeds of the individual drivelines <NUM>, <NUM>, <NUM>, <NUM> are controlled so that the average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed.

From <FIG> it can be seen that the magnitude of the outermost thrust forces F<NUM>, F<NUM> from the first and fourth drivelines <NUM>, <NUM> are greater than that of the innermost thrust forces F<NUM>, F<NUM> from the second and third drivelines <NUM>, <NUM>. As the installation in <FIG> comprises four drivelines, it is possible to operate the outermost first and fourth drivelines, as well as the innermost second and third drivelines <NUM>, <NUM> as pairs. According to this example, the first and fourth drivelines <NUM>, <NUM> are located with equal spacing from the centerline CL of the vessel on either side of the second and third driveline <NUM>, <NUM>, which in turn are located with equal spacing from the centerline CL inside the first and fourth drivelines <NUM>, <NUM>. The first and fourth drivelines <NUM>, <NUM> are operated at the same rotational output speed, which is higher than the rotational output speed of the innermost second drivelines <NUM>, <NUM>. In this way it is possible to operate the drivelines to produce a combined thrust force F<NUM> that is equal to the sum of the individual thrust forces F<NUM>, F<NUM>, F<NUM>, F<NUM>, and which coincides with the currently requested steered direction. Dependent on the determined efficiency points for each individual driveline, it is possible to achieve a combined thrust force having a neutral direction by selective adjustment of the drivelines making up the installation.

According to the invention, a vessel can comprise three or more parallel hybrid drivelines, wherein the drivelines located equidistantly on either side of the centerline of the vessel can be operated in pairs. This principle of selecting pairs of symmetrically located drivelines operated at the same rotational output speed will balance the combined thrust force can be applied to installations comprising any number of drivelines. However, the invention is not limited to this principle. Within the scope of the invention it is also possible to operate all drivelines in the installation at different rotational output speeds, as long as the average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed.

<FIG> shows a schematic diagram illustrating the operation of a driveline. In operation, the method is triggered in an initial step <NUM> when the vessel is being operated. In a first step <NUM> a control unit receives a request indicative of a vessel speed. In a second step <NUM>, the control unit determines a rotational speed for each first propulsion unit for achieving the requested vessel speed, based on the received request. In a third step <NUM>, efficiency points are determined for each of the first propulsion units and the second propulsion units from stored efficiency maps for each propulsion unit, based on the determined rotational speeds for the first propulsion unit in the respective drivelines. In a fourth step <NUM>, the rotational speed of the first propulsion unit in each powertrain is individually adjusted to improve the efficiency of this first propulsion unit while maintaining the requested vessel speed. Simultaneously, a fifth step <NUM> involves adjusting the load on the corresponding second propulsion unit in each powertrain to improve the efficiency of each powertrain and the complete powertrain installation. In a sixth step <NUM>, the individual powertrains are controlled so that the combined, average rotational output speed from all drivelines is sufficient for maintaining the requested vessel speed. In a final step <NUM>, the process returns to the first step if a request for a new rotational speed for the first propulsion units is received. The method is ended if an engine off signal is received.

The present disclosure also relates to a computer program, computer program product and a storage medium for a computer all to be used with a computer for executing said method. <FIG> shows an apparatus <NUM> according to one embodiment of the invention, comprising a nonvolatile memory <NUM>, a processor <NUM> and a read and write memory <NUM>. The memory <NUM> has a first memory part <NUM>, in which a computer program for controlling the apparatus <NUM> is stored. The computer program in the memory part <NUM> for controlling the apparatus <NUM> can be an operating system. The apparatus <NUM> can be enclosed in, for example, a control unit, such as the control unit <NUM> shown in <FIG>. The data-processing unit <NUM> can comprise, for example, a microcomputer.

The memory <NUM> also has a second memory part <NUM>, in which a program for controlling the target gear selection function according to the invention is stored. In an alternative embodiment, the program for controlling the transmission is stored in a separate nonvolatile storage medium <NUM> for data, such as, for example, a CD or an exchangeable semiconductor memory. The program can be stored in an executable form or in a compressed state. When it is stated below that the data-processing unit <NUM> runs a specific function, it should be clear that the data-processing unit <NUM> is running a specific part of the program stored in the memory <NUM> or a specific part of the program stored in the non-volatile storage medium <NUM>.

The data-processing unit <NUM> is tailored for communication with the storage memory <NUM> through a data bus <NUM>. The data-processing unit <NUM> is also tailored for communication with the memory <NUM> through a data bus <NUM>. In addition, the data-processing unit <NUM> is tailored for communication with the memory <NUM> through a data bus <NUM>. The data-processing unit <NUM> is also tailored for communication with a data port <NUM> by the use of a data bus <NUM>. The method according to the present invention can be executed by the data-processing unit <NUM>, by the data-processing unit <NUM> running the program stored in the memory <NUM> or the program stored in the nonvolatile storage medium <NUM>.

Claim 1:
Method to control at least a first and a second parallel hybrid driveline (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) arranged to drive a marine vessel (<NUM>), where each driveline comprises a first propulsion unit (<NUM>, <NUM>; <NUM> , <NUM> , <NUM> ) in the form of an internal combustion engine operatively connected with a second propulsion unit (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) in the form of an electric motor to drive a propeller shaft (<NUM>, <NUM>; <NUM>,<NUM>, <NUM>) and produce a thrust force, and where at least one control unit (<NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>; <NUM>) is arranged to control each first and second propulsion unit in all the parallel hybrid drivelines; performing the steps of:
- receiving a request indicative of a vessel speed;
- determining a rotational speed for each first propulsion unit (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) for achieving the requested vessel speed, based on the received request; characterized by:
- determining efficiency points (P<NUM>, P<NUM>; E<NUM>, E<NUM>) for each of the first and the second propulsion units from efficiency maps for each propulsion unit, based on the determined rotational speeds;
- individually adjusting the rotational speed (n<NUM>, n<NUM>) of the first propulsion unit (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) in each driveline towards the determined efficiency point to improve the efficiency of this first propulsion unit while maintaining the requested vessel speed, and
- simultaneously adjusting the load from the corresponding second propulsion unit (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) in each driveline by reducing or increasing the load from the second propulsion unit in response to the adjustment of the rotational speed of the corresponding first propulsion unit to improve the efficiency of each driveline and the complete driveline installation;
wherein the individual drivelines are controlled by exchanging data required for controlling the propulsion units between a central control unit and the drivelines or between individual control units for each driveline so that the combined rotational speed from all first propulsion units is sufficient for maintaining the requested vessel speed, wherein the method further comprises adjusting the rotational speed of at least one first propulsion unit (<NUM>, <NUM>; <NUM>, <NUM>, <NUM>) and allowing it to be operated at a different rotational speed than at least one other first propulsion unit.