Method and system for optimising operation of vessel
Disclosed are a method and a virtual sensor system for determining the speed through water of a marine vessel. The method includes obtaining propeller revolutions per minute and at least one of torque at propeller, propulsion power, thrust and engine fuel flow, obtaining speed over ground of the vessel and using the obtained data and hydrodynamic modelling to determine the speed through water of the vessel.
1. A method for determining speed through water of a vessel for optimisation of vessel operation, using a sensor system, the method comprising:
obtaining data regarding propeller revolutions per minute and at least one of torque at propeller, propulsion power, thrust or engine fuel consumption;
obtaining data regarding speed over ground of the vessel; and
using the obtained data and hydrodynamic modeling to determine speed through water of the vessel.
2. A method according to claim 1 , wherein at least one of the propeller revolutions per minute, torque at propeller, propulsion power, thrust or engine fuel consumption is a measurement value resulting from a corresponding indirect measurement based on vessel vibrations.
3. A method according to claim 2 , comprising:
obtaining logged data from one or more speed through water logs; and
using the obtained logged data in determining the speed through water of the vessel and for calibrating speed through water log data.
4. A method according to claim 3 , comprising:
obtaining oceanographic current data and using said data in determining the speed through water of the vessel.
5. A method according to claim 1 , comprising:
obtaining logged data from one or more speed through water logs; and
using the obtained logged data in determining the speed through water of the vessel and for calibrating speed through water log data.
6. A method according to claim 1 , further comprising:
obtaining oceanographic current data and using said data in determining the speed through water of the vessel.
7. A method according to claim 1 , comprising:
determining the speed through water using a statistical state-space model.
8. A method according to claim 1 , comprising:
determining the speed through water in real time.
9. A method according to claim 1 , comprising:
calculating the speed through water of the vessel using state space formulation:
Q t =ƒ( {circumflex over (v)} w,t Δ{circumflex over (R)} t ; α ′, β ′, γ )+ε 1,t
n t =g ( {circumflex over (v)} w,t ,Δ{circumflex over (R)} t ; α ′, β ′, γ )+ε 2,t
v g,t ={circumflex over (v)} w,t +ĉ t +ε 3,t
{circumflex over (v)} w,t ={circumflex over (v)} w,t-1 +η 1,t
ĉ t =ĉ t-1 +η 2,t
Δ {circumflex over (R)} t =Δ{circumflex over (R)} t-1 +η 3,t
wherein f and g are functions defined by relations:
K
Q
(
v
w
n
;
α
_
′
)
=
Q
n
2
K
T
(
v
w
n
;
β
_
′
)
=
R
cs
(
v
w
;
γ
_
)
+
Δ
R
n
2
and Q is torque of the propeller, v g is speed over ground, n is propeller revolution per minute, ε is a random variable describing measurement noise, and η is a random variable controlling evolution speed of the state, {circumflex over (v)} w is estimated speed through water, R cs (v w ; γ ) is calm sea resistance as a function of the speed through water, Δ{circumflex over (R)} is estimated extra resistance on top of calm sea resistance, ĉ is estimated oceanographic current, and parameters α, β and γ are state variables estimated based on data.
10. A method according to claim 9 , wherein the relations K Q and K T are linear or quadratic functions.
11. A method according to claim 9 , comprising:
augmenting the state space formulation is augmented with equations which take into account measured speed through water data and calibrate it as follows:
{circumflex over (v)} w,t =e −{circumflex over (x)} t {circumflex over (v)} w,t +ε 4,t
{circumflex over (x)} t ={circumflex over (x)} t-1 +η 4,t
wherein v w is the speed through water and {circumflex over (x)} is a state variable related to calibrating the speed through water log data, ε is a random variable describing measurement noise, and η is a random variable controlling the evolution speed of the state.
12. A method according to claim 9 , comprising:
augmenting the state space formulation with an equation which takes into account a forecasted current as follows:
c t =ĉ t +ε 5,t
wherein c is an oceanographic current forecast, ĉ an estimated oceanographic current, and ε is a random variable describing measurement noise.
13. A method according to claim 9 , comprising:
estimating unknown parameters of a hydrodynamic model are estimated using at least one dynamical state-space estimation technique.
14. A method according to claim 1 , comprising:
optimising with the determined speed through water, operation of the vessel, where the optimising is selected from a group comprising:
optimising time to clean a hull of the vessel;
optimisation of steering of the vessel;
optimising speed profile of a voyage; and
optimising voyage route.
15. A sensor system for determining speed through water of a vessel, the sensor system comprising:
a first receiver configured to receive propeller revolutions per minute and at least one of torque at propeller, propulsion power, thrust or engine fuel consumption;
a second receiver configured to receive speed over ground of a vessel; and
at least one processor configured to determine a speed through water of a vessel, based on received data and hydrodynamic modeling.
16. A sensor system according to claim 15 , wherein the first receiver is configured to receive at least one of the propeller revolutions per minute, torque at propeller, propulsion power, thrust or engine fuel consumption from a corresponding indirect measurement based on vessel vibrations.
17. A sensor system according to claim 15 , comprising:
a third receiver configured to receive oceanographic current data related to course of a marine vessel, wherein the processor is configured to use received data in a calculation of speed through water of the marine vessel.
18. A sensor system according to claim 15 , wherein the processor is configured to render speed through water.
19. A sensor system according to claim 15 , comprising:
a fourth receiver configured to receive data from a speed through water log, the processor being configured to use obtained data for determining a speed through water of a vessel and calibrating the speed through water log data.
20. The sensor system according 19 , in combination with a vessel whose speed is to be determined by the sensor system.