DE102016225093A1 - Method and device for wave compensation - Google Patents

Abstract

Disclosed are a method and apparatus for active wave compensation with a prediction or with a predictor for estimating the future relative movement between a load and a target position and an adaptive control. The prediction is performed using a recursive least-squares algorithm.

Description

The invention relates to a system for active wave compensation. Strictly speaking, such systems do not compensate for the swell but for the wave-induced movement of a floating device (e.g., ship or platform) due to the swell.

One of the main features and significant disturbing factor in marine and offshore operations is the wave induced movement of the floating equipment. For operations such as In the event of landing a load on the seabed / ship or laying underwater pipelines, it is necessary to wait for a so-called weather window in which a calm swell is suspected, resulting in high costs of the operation. In this regard, systems are used for wave compensation in marine and offshore technology to compensate for this movement and, where appropriate, to expand the weather window or the operating time window.

The goal of such wave compensation systems is to control a position and / or velocity of a load (e.g., pipeline or gangway). The current state of the art essentially allows the division into passive and active systems.

Passive systems use a compliant element (e.g., a passive energy store or hydropneumatic spring) which reduces load induced by the waves to a lifting unit of the floating device. This has the advantage of a simple and inexpensive construction but with limited compensation quality.

The active systems provide an additional actuator or at least a complementary active engagement in the lifting device, whereby they achieve a significantly improved compensation quality by means of suitable control strategies. The actuation may be based on hydraulic cylinders, winches with primary and secondary controlled hydraulic motors or electric motors.

In the publication EP 1 070 828 A2 an active system for wave compensation is shown. For this purpose, a measuring device (Motion Reference Unit, MRU) is provided, which detects the movement of the floating device, which is then impressed in the control loop in the form of a precontrol. Based on the control loop, an active manipulation of the actuators takes place.

A disadvantage of such active regulations is the time delay, which is largely determined by the delay of the closed loop, which by the controller, the characteristics of each installed mechanical components, the dynamics of the entire system and the signal delays due to the measurement system (bus delays, Update times, etc.) is affected.

The active system for wave compensation according to the document EP 2 123 588 A1 Therefore, in addition to the measuring device, it has a prediction device which determines a prediction (prediction) of the movement of the floating device for the near future, which is also impressed into the regulation of the lifting device. An algorithm for prediction is used.

The object of the invention is to provide a method and a device for improving the performance with a predictive control strategy. The method and the device should be able to be integrated with little effort into existing control systems. In particular, the method and the device, in contrast to publications of the prior art without change in existing control system to be used (add-on solution).

This object is achieved by a method for active wave compensation with the features of patent claim 1 and by an apparatus for active wave compensation with the features of claim 13.

Further advantageous embodiments of the invention are described in the dependent claims.

• - Messen der aktuellen Relativbewegung und
• - Vorausberechnen der zukünftigen Relativbewegung.

With the claimed method, an active wave compensation is performed in which a relative movement between a target position (eg, the seabed or a deck of a floating device) and a load (eg, a pipeline or a gangway) is at least partially compensated. The method has the following repeated steps:

• - Measuring the current relative movement and
• - Predict the future relative movement.

According to the invention, the prediction is based on a recursive least-squares algorithm.

In order to achieve the same compensation quality, more cost-effective components can be used in methods with advance calculation in comparison with the prior art. Furthermore, the method allows very low integration costs. Finally, the method enables an add-on solution for existing systems.

According to a first embodiment, the inventive method for controlling at least one actuator of a fixed - be arranged in particular on the shore - lifting device, the movement of the load to be adapted to the movement of a floating device.

In a second preferred embodiment, the floating device may comprise the lifting device so that the load is to be held stationary - e.g. over the seabed. The second embodiment of the method may e.g. be used on an offshore crane, a crane ship, an offshore gangway, a drilling platform or a drill ship.

According to a third embodiment, the floating device also has the lifting device, wherein (different from the second embodiment) the load is to be adapted to the movement of another floating device. In this case, preferably an optical measuring technique can be used to detect the relative movement of the two floating devices to each other. The third embodiment may therefore be a ship-to-ship application of the method according to the invention.

The inventive method can be developed not only to compensate for a vertical (immersion) movement (Heave) but also for the other five degrees of freedom of movement of the floating device. Thus, for linear movements along the longitudinal axis and / or linear movements along the transverse axis and / or rotational yawing movements about the vertical axis and / or rolling movements about the longitudinal axis and / or pitching movements about the transverse axis of the floating device.

Preferably, the method comprises the following supplementary step: determination of a dominant frequency of the movement, e.g. the typical Jonswap spectrum for the North Sea.

According to a first embodiment, the method is performed with a closed loop.

Preferably, the method has the following additional step: performing an offline transfer function of the control loop.

Preferably, the method has the following additional step: determination of a phase shift of the control loop.

Preferably, the method has the following additional step: determination of a prediction time as a function of the update rate based on the determined phase shift.

According to a second embodiment, the method is adaptive and has the following supplementary step: carrying out a feed-forward inversion of the closed-loop control. Thus, the performance of the method according to the invention can be further improved.

Preferably, the method has the following additional step: modification of properties of an adaptive controller as a function of the process dynamics.

Preferably, the method has the following additional step: performing an online parameter estimation of the closed-loop control in real time.

The execution of the closed loop closed loop parameter estimation is preferably based on an algorithm that performs a stable inversion of an estimated model.

The claimed device is used for active wave compensation, wherein a relative movement between a target position (eg the seabed or a deck of a floating device) and a load (eg a pipeline or a gangway) is at least partially compensated. For this purpose, the device has a measuring device for detecting the current relative movement and a predictor used as a predictor for predicting the future relative movement. According to the invention, the predictor is based on a recursive least-squares algorithm.

In order to achieve the same degree of compensation, components with predictors over the prior art can use less expensive components. Furthermore, the device allows very low integration costs. Finally, the device enables an add-on solution for existing devices.

The aforementioned developments of the method may also be preferred developments of the device.

In a preferred embodiment, the device according to the invention has a summation element via which an output signal of the predictor and an output signal of a control element can be added.

Several embodiments of the method and the device according to the invention for active wave compensation are shown in the drawings. With reference to the figures of these drawings, the invention will now be explained in more detail.

• 1 in einer schematischen Darstellung ein Schiff mit einer am Boden abzusetzenden Last mit der erfindungsgemäßen Vorrichtung zur Wellengangskompensation,
• 2 eine Schaltbild eines ersten Ausführungsbeispiels des erfindungsgemäßen Verfahrens,
• 3 ein Diagramm mit der Darstellung der Bewegung der Last ohne und mit erfindungsgemäßem Verfahren bzw. ohne und mit erfindungsgemäße Vorrichtung; und
• 4 eine Schaltbild eines zweiten Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Show it

• 1 in a schematic representation of a ship with a load to be placed on the ground with the device according to the invention for swell compensation,
• 2 a circuit diagram of a first embodiment of the method according to the invention,
• 3 a diagram showing the movement of the load without and with inventive method or without and with inventive device; and
• 4 a circuit diagram of a second embodiment of the method according to the invention.

1 shows in a simplified representation of a wave 1 a sea surface on which a ship 3 swims. Because of the wave 1 leads the ship 3 a movement (heave) h _t from which of the shaft 1 may differ, and those in 1 symbolized by a double arrow.

On the ship 3 is a crane 4 mounted over its winds 6 a burden m to the seabed 8th should be lowered. The winch has a turning speed ω , It has the load m a position z and will be at a speed v lowered.

Generally speaking, the movement is h _t of the ship 3 a relative movement h _t between a floating device 3 and a target position 8th ,

According to 2 becomes the movement h _t of the vessel at time t by a measuring device (MRU) 10 measured and as an input to estimate the future value h _{t + 1} used. The estimate is based on a recursive least squares (RLS) algorithm.

verwendet, wobei der Messdaten-Vektor $\overrightarrow{h_t^T}$

aus N Messungen bis zum Zeitpunkt t besteht, und wobei $\overrightarrow{\theta }$

die Koeffizienten sind.The estimation becomes a linear model Θ $$H_{t+1}=\overrightarrow{H_t^T}\cdot {\overrightarrow{\theta }}_t$$

used, with the measured data vector $\overrightarrow{H_t^T}$

consists of N measurements up to the time t, and where $\overrightarrow{\theta }$

the coefficients are.

berechnet, wobei λ (0≤λ≤1) der sogenannte Forgetting Factor und P_i die inverse Korrelationsmatrix der Messdaten sind.First, the so-called Kalman gain vector $${\overrightarrow{K}}_t=\frac{P_{t-1}\cdot \overrightarrow{H_{t-1}}}{\lambda +\overrightarrow{H_{t-1}^T}{P}_{t-1}\overrightarrow{H_{t-1}}}$$

where λ (0≤λ≤1) is the so-called forgetting factor and P _{i is} the inverse correlation matrix of the measured data.

bestimmt.The apriori error ε between the current measured value h _t and the estimated value h _{t + 1} is then called $${\epsilon }_t=H_t-\overrightarrow{H_{t-1}^T}\overrightarrow{{\theta }_{t-1}}$$

certainly.

und die inverse Korrelationsmatrix P_t anhand $$P_t=\frac{P_{t-1}-{\overrightarrow{K}}_t\overrightarrow{h_{t-1}^T}{P}_{t-1}}{\lambda }$$

aktualisiert.The coefficients θ _t are calculated using the equation $${\overrightarrow{\theta }}_t={\overrightarrow{\theta }}_{t-1}+{\overrightarrow{K}}_t{\epsilon }_t$$

and the inverse correlation matrix P _t based $$P_t=\frac{P_{t-1}-{\overrightarrow{K}}_t\overrightarrow{H_{t-1}^T}{P}_{t-1}}{\lambda }$$

updated.

multipliziert $$h_{t+n}=\left(h_{t-N+n-1},h_{t-N+n},H_{t+n-1}\right)\cdot {\overrightarrow{\theta }}_t$$

Subsequently, an estimate of the movement or the measured values is calculated at a time t + n. For this purpose, a new measurement data vector of corresponding length is generated iteratively and with the coefficient vector ${\overrightarrow{\theta }}_t$

multiplied $$H_{t+n}=\left(H_{t-N+n-1}.H_{t-N+n}.H_{t+n-1}\right)\cdot {\overrightarrow{\theta }}_t$$

The invention is directed to an extension of an existing AHC system for swell compensation. That means an existing controller 16 , which is formed in the illustrated embodiments as a PID controller, by incorporating future information about movement allows improved performance. Accordingly, the extended structure is divided into a "prediction of movement" and an "active precontrol".

The performance of the system for active wave compensation is determined by the delay of the closed loop 14 determined by the controller 16, the characteristics of each installed mechanical components and the signal delays due to the measuring device 10 (Bus delays, update times, etc.) is affected.

By using a predictor 12 in the feedforward control can compensate for these delays of the closed loop by a suitable prediction horizon 14 be made.

The property of the predictor 12 requires a periodic course of the input variable h _t to be as accurate as possible h _{t + 1} to meet. This is due to the characteristics of the waves 1 and accordingly the slower movement h _t of the ship 3 given.

To determine the optimal prediction time becomes an offline transfer function of the closed loop 14 carried out. Furthermore, at the known dominant frequency of wave motion h _t ( z .B. in jonswap spectrum) the phase shift of the closed loop 14 certainly. Based on the determined phase shift, the prediction time is determined as a function of the update rate.

The over a summation member 23 formed sum of the predicted future movement h _{t + 1} and a user command of a control 24 represents the input of the prior art active wave compensation system. The internal structure of the prior art system need not be changed.

A simulation of both embodiments of the method according to the invention and the device according to the invention for active wave compensation combined with the predictor 12 is in 3 shown. These are the results for the sample ship 3 with representative movement data h _t shown. There are four different speeds v the load m applied over time. The dashed curve shows the movement speed h _t of the ship and thus the speed v the load m without compensation. Further shows the curve 19 the speed v the load m with active wave compensation according to the prior art. Curve 20 shows the speed v the load m with inventive active swell compensation according to the first embodiment with phase shift. Curve 21 shows the speed v the load m with inventive active swell compensation according to the second embodiment with the adaptive method.

In the simulation based on the sample ship 3 with representative movement data h _{t was} able to improve the performance of the compensation of ship movement h _t be achieved.

In addition to the procedure described above, the performance can be further improved by means of a feed-forward inversion of the controlled system.

A disadvantage of the method described above is the need for an offline phase delay analysis, which is achieved by an extension according to 4 is solved.

An adaptive controller 22 modifies its properties depending on the process dynamics and the characteristics of the movement h _t of the ship 3 , The adaptation process requires an additional online parameter estimation by means of a parameter estimator 26 of the closed loop 14 Real time. The parameter estimator 26 is based on an algorithm that performs a stable inversion of the estimated model. The predicted motion information is included in the calculation of the manipulated variable of the adaptive controller.

Disclosed are a method and apparatus for active wave compensation with a prediction or with a predictor for estimating the future relative movement between a load and a target position and an adaptive control. The prediction is performed using a recursive least-squares algorithm.

LIST OF REFERENCE NUMBERS

1

wave

3

floating facility / ship

4

Lifting device / crane

6

winch

8th

Target position / seabed

10

measuring device

12

predictor

14

closed loop

16

regulator

18

Curve h _t

19

Curve control according to the prior art

20

Curve control with phase shift

21

Curve adaptive method

22

adaptive controller

23

Summation member

24

operating element

26

Parameter Estimates

h _t

current relative speed / movement

h _{t + 1}

future relative speed / movement

m

load

z

Position of the load

v

Speed of the load

ω

Turning speed of the winch

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1070828 A2
• EP 2123588 A1 [0008]

Claims (15)

Method for active wave compensation, with which a relative movement (h _t ) between a target position (8) and a load (m) is at least partially compensated, comprising the steps of: - measuring the current relative movement (h _t ) and - predicting the future relative movement ( h _{t + 1} ), characterized in that the prediction is based on a recursive least squares algorithm. Method according to Claim 1 , wherein the target position (8) rests or is arranged on a floating device, and wherein the load (m) is coupled to a lifting device (4) of a floating device (3). Method according to Claim 2 wherein the measuring and the prediction are done for one of the six degrees of freedom of the at least one floating device (3) or for any combination of the degrees of freedom. Method according to one of the preceding claims with the step: - Determining a dominant frequency of the relative movement (h _t ). Method according to one of the preceding claims, which is carried out with a closed loop (14). Method according to Claim 5 with the step: - performing an offline calculation of the transfer function of the control loop (14). Method according to Claim 5 or 6 , with the step: - Determining the phase shift of the control loop (14). Method according to Claim 7 comprising the step of: - determining the prediction time as a function of the update rate based on the phase shift. Method according to Claim 5 with the step: - Carrying out a feed-forward inversion of the closed-loop control. Method according to Claim 9 , comprising the step: - modifying properties of an adaptive controller (22) as a function of the relative movement (h _t ) and the process dynamics. A method according to claims 9 or 10, comprising the step: - Performing an online parameter estimation of the closed loop (14) in real time. Method according to Claim 11 wherein the step of: - performing the online parameter estimation is based on an algorithm that performs a stable inversion of the estimated model. Device for active wave compensation, with which a relative movement (h _t ) between a target position (8) and a load (m) is at least partially compensated, wherein the device comprises a measuring device (10) for detecting the current relative movement (h _t ) and a predictor (12) for predicting the future relative movement (h _{t + 1} ), characterized in that the predictor (12) is based on a recursive least squares algorithm. Device after Claim 13 to carry out the method according to one of Claims 2 to 12 is designed. Device after Claim 13 or 14 with a summation element (23), via which an output signal of the predictor (12) and an output signal of a control element (24) can be added.

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