DE102013209337A1 - Optimization of a drive system with a variable pitch propeller in a watercraft during a stop maneuver - Google Patents

Abstract

The invention relates to a method for operating a propulsion system of a watercraft during a stop maneuver, the propulsion system having at least one rotatable controllable pitch propeller (1) which each has propeller blades with an adjustable blade angle (12) and which is driven by means of a motor (3), the Motor (3) can exert a motor torque (15) on the controllable pitch propeller (1), a speed (13) of the watercraft and a propeller speed (11) of the at least one controllable pitch propeller (1) being determined. The invention also relates to a controller, a watercraft, a computer program and a computer program product for performing the method. In order to allow the watercraft to be braked quickly in a simple manner, it is proposed that a characteristic curve for the watercraft be determined in advance, which shows different initial speeds (17) of the watercraft at the start of the stopping maneuver with at least one time course of the blade angle (12) and linked to a temporal course of the propeller speed (11) in such a way that the drive system operated according to the characteristic curve during the stop maneuver results in the shortest possible stopping distance of the watercraft and the propeller speed (11) does not exceed a predeterminable, critical speed value, the drive system during the stop maneuver is operated according to the previously determined characteristic.

Description

The invention relates to a method for operating a propulsion system of a watercraft during a stop maneuver, wherein the propulsion system comprises at least one variable pitch propeller, each having propeller blades with adjustable blade angle and which is driven by a motor, wherein the engine can exert a motor torque on the variable pitch propeller, wherein a speed of the watercraft and a propeller speed of the at least one variable pitch propeller are determined. Furthermore, the invention relates to a controller, a watercraft, a computer program and a computer program product for carrying out the method.

Such a method and such a drive system are used, for example, in watercraft in which good maneuverability or widely varying steady-state speeds are required, e.g. Ferries, passenger ships, feeder.

In contrast to the conventional fixed-pitch propeller, the propeller blades are rotatably mounted on the hub of the "controllable pitch propeller" or variable pitch propeller. Thus, the pitch can be infinitely adjusted from zero thrust to maximum thrust in the direction forward or backward, wherein the pitch angle or the pitch ratio can also be referred to as blade angle.

To accelerate the vessel from standstill, the machine is started at zero thrust and ramped up, for example, to cruise speed. It is not loaded by drive torque when starting. Consequently, the vehicle does not immediately travel when the engine is started. Turbulence of the propeller shaft and associated engine (e.g., from passing ships in the harbor) is prevented by the zero-thrust propeller.

Watercraft with variable pitch propellers usually do not have a reverse gear, at most a reducer in fast-rotating engines. This eliminates a significant weakness in the drive system compared to conventional drive systems. The efficiency is cheaper at different speeds than in the case of a fixed propeller.

The drive can be reversed with the engine running from "ahead" to "back", which is associated with considerable time savings because the machine no longer has to be stopped or not shut down to minimum speed. This significantly improves maneuverability.

Especially in diesel-electric ship propulsion systems with pitch propellers, however, a backflow of power from the propeller via the electric motor occurs during emergency stop, since the propeller acts as a turbine and the electric motor works as a generator. This effect, in which unlike the normal drive operation, a negative torque acts on the propeller, is also known as "windmilling". The power with which the propeller is driven must either be fed back into the on-board power supply with appropriate power converters or burned out via so-called braking resistors. In order to ensure the stability of the electrical system and not drive the diesel generators in the reverse power range, therefore, a large structural and logistical effort is operated. In addition, the regenerative converters are much more expensive than the purely motor-operated design.

The invention has for its object to provide a method of the type mentioned above, which allows a quick deceleration of the vessel in a simple manner.

This object is achieved in a method of the type mentioned in the following process steps in that a characteristic curve for the vessel is determined in advance, which different initial velocities of the vessel at the beginning of the stop maneuver with at least a temporal course of the blade angle and a time course the propeller speed linked such that the operated during the stop maneuver according to the characteristic drive system results in the shortest possible Aufstoppweg the vessel and the propeller speed does not exceed a predetermined, critical speed value, the drive system is operated during the stop maneuver according to the previously determined characteristic.

This object is further achieved by a controller which has means for carrying out the method according to the invention, wherein the means comprise at least one computer unit and a memory unit on which the characteristic curve determined beforehand for the vessel is stored. Furthermore, this object is achieved by a watercraft with at least one drive system and the aforementioned control, wherein the drive system comprises at least one rotatable variable pitch propeller, which each has propeller blades with adjustable blade angle and which is drivable by means of a motor, wherein by means of the motor, a motor torque on the Variable pitch propeller ( 1 ) is exercisable, wherein by means of a respective sensor, at least one speed of the watercraft and a propeller speed of the at least one variable pitch propeller can be determined. After all the object is also achieved by a computer program according to claim 5 and a computer program product according to claim 6.

According to the invention, the speed of the ship is determined, wherein the flow velocity of the water with respect to the ship or the propeller can be taken into account. For example, sensors can be used for this purpose. The propeller speed is also determined, for example by means of further sensors, in particular in the form of a transmitter. In a converter-fed drive system with an electric drive motor, the propeller speed can be determined, for example, via electrical currents with which the motor is acted upon by the converter.

In addition, the propeller torque of the at least one variable pitch propeller can be determined. For this purpose, it can be used that the time change of the propeller speed is proportional to the difference between the engine torque and the propeller torque, wherein in a converter-fed drive system, the engine torque can be determined based on the engine-supplied torque-generating current.

The inventive method is used in watercraft with pitch-adjustable propeller blades and a pitch adjuster for adjusting the pitch of the propeller blades used. Furthermore, a controller may be provided which can process the data from sensors and can pass commands to the pitch adjuster, the engine, the inverter and possibly other ship components and parts of the ship propulsion system.

The characteristic according to which the drive system is operated during a stop maneuver can be determined, for example, by means of a calculation or a simulation, which is carried out for a specific vessel or for a particular type of vessel. To determine the characteristic, it is possible to use forces acting on the vessel during a stop maneuver, such as the resistance of the hull of the vessel due to the forward drive, the resistance of the rudder and the thrust of the propeller. In this case, the resistance of the vessel and the resistance of the rotor can be described for example by model experiments or semiempirische functions. For a meaningful equation of motion as the basis of the calculation or the simulation, the mass inertia of the vessel can be taken into account, which can be assumed to be known.

When determining the characteristic curve, two situations can be distinguished, in particular in the case of diesel-electric drives: If a positive torque acts on the variable-pitch propeller, the propeller speed can be freely set within the scope of the available engine power. On the other hand, if a negative torque acts on the propeller, the "windmilling" effect occurs and the propeller is driven by the water, which increases the propeller speed.

During normal operation of the ship, the ship's propulsion system generates propulsion and the at least one variable pitch propeller has a positive blade angle so that a positive torque is applied to the pitch propeller. Because positive blade angle are understood as those blade angle, which cause a feed of the ship at a given direction of rotation of the variable pitch propeller. Negative blade angles are thus understood as those blade angles which cause a repulsion of the ship in the same given direction of rotation of the variable pitch propeller.

Depending on the previously determined characteristic curve, it may be provided, for example, that during a stop maneuver the blade angle is changed by a positive blade angle until the blade angle is reached at which the variable pitch propeller no longer generates any feed. Subsequently, the blade angle can be further changed until finally a negative blade angle is reached and a recoil arises. In particular, due to the friction of the water flowing past the hull of the ship, a delay of the ship can be effected overall during this process. At the same time, the speed of the variable pitch propeller can be changed. This can be achieved by specifying a setpoint speed to the motor or, for example, also in that the drive motor is disconnected from its power supply. According to the invention, the stopping maneuver results in the shortest possible stopping distance of the watercraft, with the propeller speed not exceeding the specifiable, critical speed value. The critical speed value can in particular be selected such that serious damage to the ship propulsion system can be avoided.

Depending on the characteristics of the watercraft and the initial speed of the vessel at the beginning of the stop maneuver, it is also conceivable that the characteristic curve initially provides for maintaining the blade angle, in particular in order to prevent "windmilling". For a shortest, as far as possible during the stop maneuver Aufstoppweg can be advantageous especially at lower initial speeds of the watercraft characteristic Provide to increase the propeller speed initially, but maximum up to the critical speed value.

In an advantageous embodiment of the invention, a distance of the vessel is determined to a collision obstacle, wherein the drive system additionally performs an evasive maneuver, if the distance traveled during the stop maneuver of the vessel Aufstoppweg is greater than the distance of the vessel to the collision obstacle.

The collision obstacle may be stationary obstacles such as reefs, docks and the like, or even mobile obstacles such as other watercraft. The determination of the distance of the watercraft to the collision obstacle can be made in particular optically or by means of radar measurements. Likewise, position data of the obstacle can be supplied to the drive system to determine the distance.

In particular, when the collision obstacle is mobile and in motion, an obstruction path traveled by the collision obstruction during the stop maneuver may be taken into account in determining the distance. Thus, the obstacle path may increase or decrease an allowable stopping distance of the vessel, depending on which direction the collision obstacle is moving.

The avoidance maneuver can be optimized, for example, that the drive system current position data of the vessel are accessible. By means of stored navigation data or maps comprising the water depth, for example, possible avoidance maneuvers can be checked for feasibility, and finally an evasive maneuver can be selected which is feasible and at the same time ensures a safe distance from the possible collision obstacle.

The invention will be described and explained in more detail below with reference to the embodiments illustrated in the figures. Show it:

1 a schematic representation of an embodiment of a drive system according to the invention,

2 time courses of a blade angle according to an exemplary characteristic,

3 time profiles of a propeller speed according to another exemplary characteristic,

4 a first example of a time profile of a propeller speed according to the characteristic curve and a speed of a watercraft,

5 a second example,

6 a third example, and

7 a fourth example.

1 shows a schematic representation of an embodiment of a drive system according to the invention. A variable pitch propeller 1 is via a reducer 4 from a motor 3 driven. The variable pitch propeller 1 has propeller blades, which each have an adjustable blade angle 12 have, by an adjustment 5 can be changed. The motor 3 is from a converter 2 energized, the inverter 2 Setpoints related to the engine speed 10 from a controller 6 receives. The controller 6 becomes the actual, from a giver 7 determined propeller speed 11 fed and the controller 6 continue to give target values with regard to the blade angle 12 to the adjustment unit 5 ,

2 shows temporal courses of a blade angle 12 according to an exemplary characteristic. As in the following figures, the characteristic was determined in advance and ensures that a drive system of an associated vessel operated during a stop maneuver according to the characteristic curve results in the shortest possible stop-up distance and the propeller speed 11 does not exceed a predefinable, critical speed value. For the calculation or simulation for determining the characteristic, forces acting on the vessel, such as the resistance of the hull of the vessel due to the forward drive, the resistance of the rudder and the thrust of the propeller can be taken into account. Furthermore, the inertia of the watercraft can be used to determine the characteristic curve.

Shown are different temporal courses of the blade angle 12 , where on the x-axis the time, on the y-axis of the blade angle 12 and on the z-axis the initial velocity 17 each applied in arbitrary units. In the illustration it is assumed that before the start of the stop maneuver always a certain positive blade angle 12 is applied, for example, those blade angle 12 which provides maximum feed. At time t _S is for different initial speeds 17 the stop maneuver started. As you can see, time is a complete reversal of the blade angle 12 from the initial speed 17 from: At low initial speeds 17 can the blade angle 12 very quickly reversed at higher initial speeds 17 sees this exemplary characteristic more time for the reversal of the blade angle 12 in front.

The determined characteristic can furthermore take into account that during operation of the vessel before the stop maneuver different blade angles 12 issue. For the sake of simplicity, a corresponding graphical representation is dispensed with.

3 shows time courses of a propeller speed 11 according to another exemplary characteristic. Shown are different time profiles of the propeller speed 11 , where on the x-axis, the time on the y-axis, the propeller speed 11 and on the z-axis the initial velocity 17 each applied in arbitrary units. Again, at time t _{S will be} for different initial speeds 17 the stopping maneuver started, wherein before the start of the stop maneuver different propeller speeds 11 available. At low initial speeds 17 and as in this example, even at low propeller speeds 11 At the beginning of the stop maneuver, the propeller speed becomes 11 increased rapidly and considerably. At a comparatively high initial speed 17 becomes the propeller speed 11 maintained according to the present characteristic. At even higher initial speeds 17 becomes the propeller speed during the stop maneuver 11 decreased.

4 shows a first example of a time course of a propeller speed 11 according to the characteristic and a speed 13 a watercraft. Furthermore, exemplary temporal courses of a blade angle 12 and a moment coefficient 14 represented, on the ordinate axis of the respective absolute value of said measured variable and on the abscissa the time, each in arbitrary units are plotted. A positive moment coefficient 14 means that on the variable pitch propeller 1 Overall, a positive torque acts. This can, as in the following figures, the curves shown in particular of the in the 2 and 3 Distinguish exemplary curves illustrated.

At the beginning are the determined speed 13 and the propeller speed 11 of the vessel constant and comparatively high. There is a positive blade angle for this 12 which is in a positive moment coefficient 14 results.

At time t _S , a stop maneuver is initiated and the blade angle 12 decreased and eventually changed to negative angles. At the same time the propeller speed becomes 11 increased by the engine speed 10 is increased until a maximum speed is reached. The maximum speed can be selected, for example, so that the propeller speed 11 does not exceed a predefinable, critical speed value. These measures have the consequence that the moment coefficient 14 abruptly sinks, but still remains positive. A negative moment coefficient 14 would indicate that a negative torque on the variable pitch propeller 1 acts and thus "windmilling" occurs. Meanwhile, the determined speed decreases 13 of the vessel comparatively fast and the moment coefficient 14 after a certain period of time assumes greater values than at the beginning of the stop maneuver, in which the direction of rotation of the propeller is always maintained. At increased propeller speed 11 and adjacent negative blade angle 12 becomes the determined speed 13 until it finally assumes the value zero and the vessel is stationary. For not shown and listed here reference numerals see the other figures.

5 shows a second example of a time course of a propeller speed 11 according to the characteristic and a speed 13 a watercraft. In comparison to 4 are the determined speed 13 and the propeller speed 11 lower before the start of the stop maneuver. During the stop maneuver, the propeller speed becomes 11 massively increased, with the blade angle 12 only gradually is reversed. This results in an ascertained speed increased at the beginning of the stop maneuver 13 , which is then reduced to zero. During the entire stop maneuver the moment coefficient remains 14 always positive, so that no "windmilling" occurs.

6 shows a third example of a time course of a propeller speed 11 according to the characteristic and a speed 13 a watercraft. During the stop maneuver, the propeller speed remains 11 unchanged and the blade angle 12 is gradually reversed. The moment coefficient 14 remains positive during the entire stop maneuver and the determined speed 13 is continuously lowered until the vessel is at a standstill.

7 shows a fourth example of a time course of a propeller speed 11 according to the characteristic and a speed 13 a watercraft. The determined speed 13 and the propeller speed 11 are comparatively large before the start of the stop maneuver. At the beginning of the stop maneuver, the blade angle 12 relatively quickly reversed, with the engine 3 from the inverter 2 is disconnected, so that the propeller speed 11 initially drops rapidly. Since at the beginning of the stop maneuver the torque coefficient 14 is negative for a certain period of time, occurs the "windmilling" effect, so that the propeller speed 11 rises again. After the time period during which "windmilling" occurs has elapsed, the torque coefficient decreases 14 positive values again. During the entire stop maneuver the determined speed becomes 13 continuously reduced, and also the propeller speed 11 remains below the predefinable, critical speed during the entire stop maneuver.

In summary, the invention relates to a method for operating a propulsion system of a watercraft during a stop maneuver, wherein the drive system comprises at least one variable pitch propeller, each having propeller blades with adjustable blade angle and which is driven by a motor, wherein the motor can exert a motor torque on the variable pitch propeller wherein a speed of the watercraft and a propeller speed of the at least one variable pitch propeller are determined. Furthermore, the invention relates to a controller, a watercraft, a computer program and a computer program product for carrying out the method. In order to allow a quick deceleration of the vessel in a simple manner, it is proposed that a characteristic curve for the vessel be determined in advance, which different initial velocities of the vessel at the beginning of the stop maneuver with at least a time course of the blade angle and a time course of the propeller speed linked so that the operated during the stop maneuver according to the characteristic drive system results in the shortest possible Aufstoppweg the vessel and the propeller speed does not exceed a predetermined, critical speed value, the drive system is operated during the stop maneuver according to the previously determined characteristic.

Claims (6)

Method for operating a propulsion system of a watercraft during a stop maneuver, wherein the propulsion system comprises at least one rotatable variable pitch propeller ( 1 ), which in each case propeller blades with adjustable blade angle ( 12 ) and which by means of a motor ( 3 ) is driven, the engine ( 3 ) a motor torque ( 15 ) on the variable pitch propeller ( 1 ), whereby one speed ( 13 ) of the watercraft and a propeller speed ( 11 ) of the at least one variable pitch propeller ( 1 ), characterized in that a characteristic for the vessel is determined beforehand, which has different initial speeds ( 17 ) of the watercraft at the beginning of the stop maneuver with at least a respective time course of the blade angle ( 12 ) and a time profile of the propeller speed ( 11 ) such that the drive system operated according to the characteristic during the stopping maneuver results in the shortest possible stopping distance of the watercraft and the propeller speed ( 11 ) does not exceed a predefinable, critical speed value, wherein the drive system is operated during the stop maneuver according to the previously determined characteristic curve. Method according to claim 1, wherein a distance of the vessel is determined to a collision obstacle, and wherein the propulsion system additionally performs an evasive maneuver if the stoppage distance traveled by the vessel during the stopping maneuver is greater than the distance of the vessel from the collision obstacle. Control ( 6 ) for a watercraft having at least one propulsion system, the controller ( 6 ) Means for performing a method according to claim 1 or 2, wherein the means comprise at least one computer unit and a memory unit on which the previously determined for the vessel characteristic is stored. Watercraft with - at least one propulsion system and - a control system ( 6 ), which is designed according to claim 3, wherein the drive system comprises at least one rotatable variable pitch propeller ( 1 ), which in each case propeller blades with adjustable blade angle ( 12 ) and which by means of a motor ( 3 ) is drivable, wherein by means of the engine ( 3 ) a motor torque ( 15 ) on the variable pitch propeller ( 1 ) is exercisable, wherein by means of a respective sensor at least one speed ( 13 ) of the watercraft and a propeller speed ( 11 ) of the at least one variable pitch propeller ( 1 ) can be determined. Computer program for carrying out a method according to one of Claims 1-2 when running in a controller ( 6 ) according to claim 3. Computer program product on which a computer program according to claim 5 is stored.

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