The invention relates to a vessel with a motion compensation platform.
The invention also relates to a motion platform.
The invention further relates to a method for compensating motions of a vessel.
The invention also relates to the use of a Stewart platform.
A vessel with a Stewart platform for compensating motions of a ship is already known. The platform comprises a surface, borne on six hydraulic cylinders, and motion sensors. During use, with the aid of the sensors, the motions of the respective ship are measured. With the aid of these measurements, the orientation of the hydraulic cylinders is driven continuously so that the surface remains approximately stationary relative to the fixed world. In this manner, motions of the ship are compensated and for instance people or loads can be transferred from the ship onto a stationary offshore construction, or vice versa.
One of the objects of the invention is to improve a motion platform, in particular a vessel with motion platform.
Another object of the invention is to improve the safety of the use of a vessel and/or motion platform.
At least one of these and other objects are achieved with a vessel with a motion compensation platform, which platform is provided with at least one carrier for bearing, moving and/or transferring a load, actuators for moving the at least one carrier relative to the vessel, preferably in six degrees of freedom, a control system for driving the actuators, and motion sensors for measuring motions of the vessel relative to an element in the surrounding area, which measurements are used as input for the control system. Here, at least one at least partly passive pressure element is provided for furnishing, during use, a pressure on the carrier for at least partly bearing this.
The at least partly passive pressure element applies a counterpressure to the carrier, whereby the actuators can be at least partly relieved. As a result, the actuators can be driven with relatively lighter pressure differences, thereby achieving greater precision.
The at least one object mentioned and/or other objects are also achieved with a motion platform particularly suitable for a vessel as described in any one of claims 1-9, which platform is provided with at least one carrier for bearing, moving and/or transferring a load, actuators, for moving the carrier, preferably in six degrees of freedom, relative to at least one fixed point of the actuators, and a control system, the control system being designed for driving the actuators for said relative movement of the carrier, while at least one at least partly passive pressure element is provided for at least partly compensating the mass of the load.
In addition, the at least one object mentioned and/or other objects are achieved with a method for compensating motions of a vessel, wherein the motions of the vessel are measured, wherein a carrier with a load is driven so that the carrier is held substantially stationary relative to an element in the surrounding area, while the gravity of a load is at least partly compensated through the application of a substantially constant counterpressure to the carrier.
The at least one object mentioned and/or other objects are also achieved through the use of a Stewart platform, while the carrier is at least partly borne by at least one substantially passive pressure element, in particular pneumatic means.
It is noted that in U.S. Pat. No. 5,947,740, a motion platform for a simulator is described which, in addition to six actuators, comprises a continuously (i.e. actively) driven hydraulic cylinder for taking away the load of the weight from the other actuators. When moving the platform and setting it at different angles, the pressure on the hydraulic cylinder is measured continuously and adjusted actively to the pressure variations. Contrary to this known pressure element, the at least one pressure element according to the invention is at least partly passive. The at least one pressure element is also particularly suitable for a motion platform for compensating motions of the vessel that is, holding the platform, at least a carrier, approximately stationary relative to an element in the surroundings such as, for instance, the fixed world, such as, for instance, an offshore construction, a quay or the surrounding water, and/or a floating element such as another vessel, etc. In case of a defect in the active drive of the actuators, for instance, the at least one pressure element will remain functional, thereby increasing the safety of the vessel while it remains of relatively limited complexity.
In clarification of the invention, exemplary embodiments of a vessel, motion platform, method and use according to the invention will be further elucidated with reference to the drawing. In the drawing:
In this description, identical or corresponding parts have identical or corresponding reference numerals. In the drawing, embodiments are given only as examples. The parts used there are mentioned merely an as example and should not be construed to be limitative in any manner. Other parts too can be utilized within the framework of the present invention.
This transferring from or to the vessel 1 should of course not be limited to the transfer from and/or to windmills 2. In principle, transferring can be carried out between the vessel 1 and any other surrounding element 2. The vessel 1 is suited for transferring, for instance, people, animals and/or loads to, in principle, any offshore construction, such as platforms at sea 3 and/or other constructions in the water 3, etc. In certain embodiments, a vessel 1 according to the invention is designed for transferring to any part connected to the fixed world, such as a quay, a levee, cliffs, steep rocks, (sea) floor etc. In certain embodiments, a vessel 1 has been made suitable for transferring to other moving elements and/or floating elements, such as, for instance, other vessels. To that end, with the aid of, for instance, a camera, optical sensor or the like, the motions of such a moving element can be registered and be compensated by the active components in the motions of the carrier.
In the embodiment shown, the motion compensation platform 4 is provided with six hydraulic cylinders 5 and a carrier 6. Such a motion platform 4 is known as simulation platform, as “Stewart” platform. The carrier 6 of such a platform 4 is typically movable in six degrees of freedom. In operation, the carrier 6 will be held, within the invention, substantially stationary relative to the windmill 2 by the hydraulic cylinders 5, by means of active drive. To that end, in/on the motion platform 4, and/or in/on the vessel 1, sensors such as motion sensors 7 and a control system 8 are provided, which are shown in
In the embodiment shown in
As stated, the pneumatic means 9 relieve the hydraulic cylinders 5. In particular embodiments, this results in that less oil has to be circulated for holding the carrier 6 stable upon motions of the vessel 1. In one embodiment, the pneumatic means 9 may be set, with the aid of the compressor 12, for providing a compressive force that absorbs at least a large part of the weight of the carrier 6 and the load. Partly because of the mass inertia of the carrier 6 and the load, and the constant pressure provided by the cylinder 10 and the accumulator 11 on the carrier 6, in one embodiment, the carrier 6 will tend to remain approximately stationary relative to the fixed world. Consequently, the hydraulic cylinders 5 can compensate the motions of the vessel 1 with relatively small forces, i.e., hold the carrier 6 approximately stationary relative to an element in the surrounding area.
In one embodiment, the pneumatic means 9 are also designed for preventing the reinforcement of particular motions of the vessel 1, for instance through the forces exerted by the hydraulic cylinders 5 on the vessel 1. As indicated in an exaggerated, schematic manner in
In particular embodiments, the motion sensors 7 comprise known motion sensors 7 such as for measuring motions of the vessel 1, for instance accelerometers or dynamometers. With known accelerometers, the motion of the vessel 1 relative to the fixed world can be measured. Also, in particular embodiments, other types of sensors 7 can be utilized, such as for instance cameras, GPS (Global Positioning System), sensors utilizing electromagnetic waves, sonic waves, etc. The sensors 7 may measure the position of the vessel 1 relative to one or more elements in the surrounding area, such as for instance another vessel 1 and/or the fixed world. The information the control system 8 receives from the motions sensors 7 is processed via, for instance, preprogrammed algorithms so that the hydraulic cylinders 5 can be driven for holding the carrier 6 approximately stationary relative to the respective at least one element in the surrounding area.
In particular embodiments, the control system 8 comprises, in addition to algorithms for driving the hydraulic cylinders 5, a drive for anticipating specific motions of the vessel 1. Through recognition of, for instance, a specific order in the motions of the vessel 1, the control system 8 drives the cylinders 5 proactively. In this manner, the forces of the hydraulic cylinders 5 on the vessel 1 can remain as small as possible and motions of the vessel 1 can be prevented from being unfavourably influenced, at least being reinforced.
The operation of an embodiment of the motion platform 4 is approximately as follows. When the vessel 1 is close to the windmill 2, the platform 4 is activated. The pressure in the pneumatic means 9 is increased with the aid of the compressor 12 to approximately the weight of the carrier 6 and a load thereon, so that carrier 6 and load, or a part thereof, are borne by the pneumatic means 9. This may be carried out in cooperation with measurements from the hydraulic cylinders 5 and/or the motion sensors 7, with which the weight and or the motion of the vessel 1, respectively, can be measured relatively simply. Naturally, also, other weight meters and/or methods for measuring the weight and/or motions can be utilized for setting the desired pressure in the pneumatic means 9. In addition, the velocities and accelerations of the motions of the vessel 1 are measured with the motion sensors 7, which measurements are used as input for the control system 8. Through continuous adjustment of the six cylinders 5, the carrier 6 will be able to virtually stand still relative to the windmill 2. After that, a hatch or gangplank connected to the platform 4 and/or the windmill 2 can be lowered so that personnel and/or the load can be transferred safely.
In certain embodiments, the pneumatic means comprise several pneumatic cylinders 10. As shown in
As shown in the schematic embodiment of
Instead of hydraulic cylinders 5, naturally, also other amounts and types of actuators 6 can be utilized within the framework of the invention. Other embodiments may comprise active pneumatic cylinders, linear motors, electric driving elements etc.
These and may comparable variations, as well as combinations thereof, are understood to fall within the framework of the invention as outlined by the claims. Naturally, different aspects of the different embodiments and/or combinations thereof can be combined with each other and be exchanged within the framework of the invention. Therefore, the embodiments mentioned should not be understood to be limitative.
Number | Date | Country | Kind |
---|---|---|---|
1031263 | Mar 2006 | NL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/NL2007/050080 | 2/28/2007 | WO | 00 | 3/6/2009 |