Patent Grant
10286980
The present invention relates to roll of marine vessels and specifically relates to controlling the roll angle of a body portion of a vessel.
Controlling the roll angle of an aircraft during a turn such that the resultant force (comprising a vertical gravitational force and a centrifugal force) remains perpendicular to the floor of the cabin is known as making a coordinated turn. This is particularly important for passenger comfort as the weight of a person remains acting downwards relative to the person and relative to their seat, and any drink on a table appears level. Although the weight of the person increases slightly, they do not feel a lateral force.
A coordinated turn strategy for roll control has been applied to mono-hull boats using interceptors as disclosed in International Publication Number WO2011/099931 to overcome roll or heeling issues with propulsion pod marine vessels. Similarly it has been proposed for stability reasons to apply a coordinated turn strategy for roll control of a hybrid craft comprising a mono-hull connected under a small aircraft as disclosed in International Publication Number WO91/12172.
In the applicant's International Publication Numbers WO2011/143692 and WO2011/143694 are disclosed multi-hull vessels comprising suspension. The hulls are moveable relative to the deck or body portion and active (powered) control of the roll attitude of the body relative to the hulls is discussed. U.S. Pat. No. 3,517,632 also discloses a multi-hulled vessel in which the left hull and the right hull are moveable vertically relative to the body in dependence on steering angle to provide a lateral shift in the centre of mass of the body inwards towards the centre of the turn and also to tilt the hulls into the turn to enhance the steering effect without requiring a rudder. However controlling roll angle in dependence on steering angle without including a speed parameter does not vary roll angle in dependence on lateral acceleration, so does not provide a coordinated turn control.
In a conventional multi-hulled vessel such as a catamaran for example where the hulls are fixed relative to the deck or body portion, executing a coordinated turn requires the hull towards the inside of the turn to be moved downwards relative the water surface and the hull towards the outside of the turn to be moved upwards relative to the water surface. These changes in the displacement of the inner and outer hulls during a turn can provide significant hydrodynamic losses in efficiency and the inability to move the hulls relative to the body make executing a coordinated turn at planing speed impossible. Also the wider the spacing between the hulls, the smaller the range of possible controlled roll angles, so the lower the maximum lateral acceleration that can be compensated for through adjusting the vessel roll angle. For these reasons multi-hulled vessels of conventional construction, where the hulls are fixed, are generally unable to execute coordinated turns at speed.
The present invention provides in one aspect a vessel having a body portion that is at least partially suspended above at least two hulls which are moveable with respect to the body portion, at least one sensor arranged to sense at least one operational parameter of the vessel, roll attitude of the body portion being adjustable and controlled during operation in response to said at least one operational parameter to ensure that the sum of the gravitational force and the centrifugal (substantially lateral with respect to ground) force acting on the vessel during a turn has a line of action that is perpendicular to a deck of the vessel. The at least two moveable hulls may include at least one left moveable hull and at least one right moveable hull.
The at least one operational parameter may include at least one lateral acceleration parameter. The at least one lateral acceleration parameter may include a predicted lateral acceleration, being a function of steering angle and speed, since lateral acceleration oriented relative to ground is substantially proportional to steering angle multiplied by the square of the vessel speed. When the steering angle is changed, the function of steering angle and speed can be used to predict the lateral acceleration that the vessel is about to experience before the loads build up, allowing the roll adjustment to be made before or while the roll moment builds up with increasing lateral acceleration. This is able to thereby reduce or minimise the power required to control the roll attitude of the body while maintaining the sum of the gravitational and centrifugal forces substantially perpendicular to a deck or floor portion of the body portion. The power required to provide active control of the roll angle can be minimised through the mechanism of the lateral shift of the centre of mass providing a roll moment compensating for the roll moment caused by the centrifugal force of a turn. Alternatively, for example when the steering angle is steady state, the at least one lateral acceleration parameter may include a calculated lateral acceleration, being a function of steering angle and speed. The function is essentially the same, but now the calculated lateral acceleration should be an actual lateral acceleration rather than a predicted soon to happen lateral acceleration. This calculated lateral acceleration is similarly oriented relative to ground. Alternatively or additionally, the at least one lateral acceleration parameter may include a calculated lateral acceleration, being a function of suspension support forces, since the roll moment due to cornering generates a difference in left versus right support forces in the suspension system (i.e. a couple) which can be used to calculate the lateral acceleration on the vessel body. Alternatively or additionally, the at least one lateral acceleration parameter may include a calculated lateral acceleration, being an average of two vertically spaced lateral accelerations oriented horizontally with respect to the body. As the vertically spaced lateral accelerometers are oriented horizontally with respect to the body, in this case the calculated lateral acceleration is likewise oriented horizontally with respect to the body, so minimising the calculated lateral acceleration oriented relative to the body ensures that the sum of the gravitational force and the centrifugal force acting on the vessel during a turn has a line of action that is substantially perpendicular to a deck of the vessel, i.e. achieve a coordinated turn. Similarly if a single body mounted lateral accelerometer is used to measure lateral acceleration on the body in an orientation horizontal with respect to the body, i.e. parallel to the deck so it rotates with rotation of the body, then the measured lateral acceleration can be minimised to ensure that the body roll attitude is substantially consistent with a coordinated turn. Therefore, the at least one lateral acceleration parameter may include a measured lateral acceleration, being measured in a lateral direction oriented horizontally with respect to the body portion. Conversely if the lateral acceleration is measured oriented relative to ground, using for example a motion compensated (tri-axial) accelerometer, then the roll angle to achieve a coordinated turn can be calculated from that lateral acceleration and the vessel roll angle adjusted to suit. Therefore, the at least one lateral acceleration parameter may include a measured lateral acceleration, being measured in a lateral direction relative to ground
In one or more forms of the present invention, the body portion may be entirely supported above said at least two moveable hulls. Alternatively, the body portion of vessel may include at least one further hull fixed to the body portion and providing partial support of the body portion relative to the water surface and/or the at least two moveable hulls may include at least one left hull and at least one right hull. The at least one left hull may be a single hull towards a left side of the vessel and the at least one right hull may be a single hull towards a right side of the vessel in which case the vessel can be a catamaran or trimaran. Alternatively, the at least one left hull may include a forward left hull and a rearward left hull and the at least one right hull may include a forward right hull and a rearward right hull, the forward and rearward left and right hulls can then be arranged in a rectangular configuration for example. Alternatively, the at least two hulls further include at least one forward hull and at least one rearward hull, the left, right, forward and rearward hulls being arranged in a diamond configuration for example.
In one or more forms of the present invention, the body portion may be entirely suspended above said at least two hulls which are individually moveable in a vertical direction relative to the body portion, but constrained from moving in a lateral direction relative to the body. In this case, such as when using trailing arms for example, the vertical (with respect to ground) component of the load on each hull may be maintained substantially constant during a steady state coordinated turn.
In one or more forms of the present invention, the body portion may be supported above the hulls by a suspension system including at least two fluid actuators that vary in length and fluid volume, at least one of said two fluid actuators may include a chamber being part of at least one left circuit having a left circuit fluid volume and at least one of said two fluid actuators may include a chamber being part of at least one right circuit having a right circuit fluid volume. The suspension system may further include a fluid control system including at least a pump to effectively or directly transfer fluid between the at least one left circuit and the at least one right circuit to thereby enable adjustment of the roll attitude of the vessel.
In one or more forms of the present invention, the control of the roll attitude of the body portion may include time or the at least one operational parameter may be time-averaged. For example, the rate of roll adjustment may be controlled, so that a step change in steering angle does not elicit an immediate step change in roll attitude, but instead the roll attitude is adjusted at a rate that the vessel could move at, or should move at as a maximum for comfort. Or the lateral acceleration from an accelerometer may be averaged over a period such as a tenth of a second, either in blocks of that period, or as a moving average.
The body portion may be supported above the hulls by a suspension system including multiple support devices. The control of the roll attitude of the body portion may use pressures within and/or loads upon at least one of said multiple support devices. This and/or any other function may be combined. The support devices may be the fluid actuators and/or mechanical springs for example. Additionally or alternatively, the roll attitude of the body portion may be controlled up to a roll attitude limit which is determined in dependence on at least one support device exceeding a predefined travel limit and/or pressure or load.
In one or more forms of the present invention, the roll attitude of the body portion may be controlled up to a roll attitude limit which is determined in dependence on hull displacement relative to the body portion (for example pitch and heave motions relative to the body portion) and/or a detected sea state.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least two hulls moveable relative to the body portion, the body being at least partially supported above said at least two hulls, the method including the steps of measuring a lateral acceleration of the body portion and adjusting the roll angle of the body to minimise the measured lateral acceleration of the body portion, said lateral acceleration of the body portion being parallel to a deck of the body portion (not absolute). The method may further include the step of measuring the lateral acceleration of the body portion using at least one lateral accelerometer mounted to the body portion.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least two hulls moveable relative to the body portion, the body being at least partially supported above said at least two hulls, the method including the steps of detecting at least one lateral acceleration parameter and adjusting the roll angle of the body using the at least one lateral acceleration parameter to maintain a roll angle that is substantially consistent with a coordinated turn.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least two hulls moveable relative to the body portion, the body being at least partially supported above said at least two hulls, the method including the steps of detecting at least one lateral acceleration parameter and adjusting the roll angle of the body using the at least one lateral acceleration parameter to ensure that the line of action of the sum of the gravitational force and the centrifugal force acting on the vessel during a turn is perpendicular to a deck of the vessel.
In either of the above two methods the step of detecting at least one lateral acceleration parameter may further include the steps of measuring vessel operating parameters and calculating or predicting the turning forces on the body portion. The operating parameters may include vessel speed & steering angle.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least one left hull and one right hull moveable relative to the body portion, the body portion being at least partially supported above said at least one left hull and one right hull, the method including the step of adjusting the roll angle of the body to ensure that at least a vertical component of the pressure loads on the at least one left hull is within 15% of the equivalent at least vertical component of the pressure loads on the at least one right hull. The lateral component of the pressure loads on each hull increases to react the centrifugal force during a turn, but if the vertical component of the pressure loads on each hull is maintained or the change in the time-averaged vertical component of the pressure loads on each hull due to the roll moment on the body portion is substantially compensated by a lateral load shift due to rolling of the body portion, then the speed of the vessel is typically much less reduced than if the load balance changes between the left and right hulls. So preferably the variation between the (preferably time averaged) vertical component of the pressure load on the at least one left hull is within 15%, but it may be less than 10% or less than 5% or less than 2% of the equivalent vertical component of the pressure loads on the at least one right hull. This approach can improve efficiency, but does not necessarily provide the occupants of the vessel body portion with the comfort of a perfectly coordinated turn.
The method may further include the step of estimating and/or measuring the lateral acceleration of the body portion using at least one lateral accelerometer mounted to the body portion. The step of estimating and/or measuring the lateral acceleration may include using at least one motion compensated lateral accelerometer mounted to the body portion. Alternatively or additionally, the step of estimating and/or measuring the lateral acceleration may include the steps of measuring speed and steering angle and the step of calculating lateral acceleration. This enables a balance to be chosen between efficiency and occupant comfort.
The method may further include the step of estimating and/or measuring at least one load on said at least one left hull and one right hull.
The vessel may further include a suspension system for supporting at least a portion of the body above or relative to the at least one left hull and one right hull, the method may further include the step of estimating or measuring at least one load on or at least one pressure in the suspension system. For example the load in a mount of a suspension device (such as a ram or a spring) can be measured, but if the suspension device is fluid filled such as an air spring or a hydraulic ram, the pressure of the fluid can be measured to calculate force on the suspension device.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least one left hull and one right hull moveable relative to the body portion, the body portion being at least partially supported above said at least one left hull and one right hull, the method including the steps of determining the leeway angle with which the vessel is proceeding and adjusting the roll angle of the body portion using leeway angle.
The step of adjusting the roll angle of the body portion using leeway angle may include adjusting the roll angle of the body portion of the vessel in dependence on an estimate or measurement of lateral acceleration or centrifugal force (rather than steering angle and speed alone for example) when the leeway angle exceeds a preset magnitude to prevent for example a steering angle due to leeway from driving an unnecessary roll of the body portion. Additionally or alternatively a global positioning signal may be used to determine that the angle of the steering is due to leeway rather than turning.
Additionally or alternatively, the step of adjusting the roll angle of the body portion using leeway angle may include adjusting the roll angle of the body portion of the vessel to ensure that at least a vertical component of a load on the at least one left hull is within 15% of the equivalent at least vertical component of a load on the at least one right hull when the leeway angle exceeds a preset magnitude. The load may be for example a pressure load on the hull from the water, or a load in a support device in a suspension system between the body portion on the left and right hulls.
Additionally or alternatively, the step of adjusting the roll angle of the body portion using leeway angle may further include the steps of: estimating or measuring lateral acceleration or centrifugal force; and estimating or measuring at least one load on at least one of the at least one left hull and one right hull or measuring a load on or pressure in a suspension component between the body portion and at least one of the at least one left hull and one right hull.
The step of adjusting the roll angle of the body using leeway angle may include calculating a roll angle offset to reduce or remove any difference between a roll angle set point for a perfectly coordinated turn and a roll angle set point calculated using inputs influenced by the leeway angle. The magnitude of the roll angle offset may be decayed as a function of time, the function optionally including any of lateral g, speed, steering angle and/or at least one load on at least one hull or at least one suspension member between the body portion and a hull.
According to another aspect of the present invention, there is provided a method of controlling the roll angle of a body portion of a vessel, the vessel further including at least one left hull and one right hull moveable relative to the body portion, the body portion being at least partially supported above said at least one left hull and one right hull, the method including the steps of determining a magnitude of payload offset and adjusting the roll angle of the body using the magnitude of payload offset.
The step of adjusting the roll angle of the body using magnitude of payload offset may include adjusting the roll angle of the body portion of the vessel in dependence on an estimate or measurement of lateral acceleration or centrifugal force (rather than or instead of using steering angle and speed alone for example) when the payload offset exceeds a preset magnitude.
Additionally or alternatively, the step of adjusting the roll angle of the body using the magnitude of payload offset may include adjusting the roll angle of the body portion of the vessel to ensure that at least a vertical component of a pressure load on the at least one left hull is within 15% of the equivalent at least vertical component of a pressure load on the at least one right hull when the payload offset is less than a preset magnitude.
Additionally or alternatively, the step of adjusting the roll angle of the body using the magnitude of payload offset may further include using: an estimate or measurement of lateral acceleration or centrifugal force; and an estimate or measurement of at least one load on at least one of the at least one left hull and one right hull or a measurement of a load on or pressure in a suspension component between the body portion and at least one of the at least one left hull and one right hull.
The step of adjusting the roll angle of the body using the magnitude of payload offset may include calculating a roll angle offset to reduce or remove any difference between a roll angle set point for a perfectly coordinated turn and a roll angle set point calculated using inputs influenced by the magnitude of payload offset. The magnitude of the roll angle offset may be decayed as a function of time (the function optionally including any of lateral g, speed, steering angle and/or at least one load on at least one hull or at least one suspension member).
It will be convenient to further describe the invention by reference to the accompanying drawings which illustrate preferred aspects of the invention. Other embodiments of the invention are possible and consequently particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.
In the drawings:
Referring initially to
When the vessel 1 is under-way and makes a turn to the right, centrifugal force FC additionally then acts leftwards on the centre of mass of the body portion 2 as shown in
An additional advantage to making a coordinated turn is that the centre of mass of the body portion shifts inwards towards the centre of the turn relative to the hulls. Assuming that the centre of mass of the body portion is on the centreline of the vessel, assuming that the left and right halves of the vessel are mirrored through the centreline when the vessel is static, and assuming that the suspension geometry between the body portion and the hulls is the leading arm and slider type shown in
If an alternative suspension geometry (locating the hulls relative to the body portion) is used, the width between the hulls can change, the roll angle of the hulls relative to the body portion can change, the spacing between the centres of buoyancy of the left and right hulls can change and the transfer of forces and moments between the hulls and the body portion can change. This can generate an imbalance in the change in vertical loads on the hulls between reacting the moment of the centrifugal force versus reacting the lateral weight shift for example and this can result in various effects including roll jacking. It also means that different control strategies will either need to take suspension geometry effects into account (or approximately compensate for them) or will only adjust the roll attitude of the body portion of the vessel to an approximation of a coordinated turn where the roll angle of the body portion φ is similar, but not exactly equal to the angle θ required for a coordinated turn as defined above. Such control strategies can optimse for efficiency (i.e. minimal change in the vertical load on each hull and hence minimised loss of speed during turning) or optimise for passenger comfort (i.e. a perfectly coordinated turn) or any desired compromise or balance between these strategies.
The roll control system of the interconnected hydraulic rams provides roll stiffness without a corresponding stiffness in the warp mode. The rod cross sectional area influences the heave stiffness, the ratio of bore (compression) and annular (rebound, i.e. bore minus rod) area to rod area influences the ratio of roll to heave stiffness. So the hydraulic rams are modal supports when interconnected. Conversely the independent springs are independent supports, providing stiffness in all modes, roll, pitch heave and warp.
The suspension arrangements of
The catamaran in
The mid arm 71 is hung from a drop link 72 connected at the top to a body mount point 73. A mid support 74 acts between the body and a point along the mid arm. The joints at the body mount point 73, knee joint 75 and mid hull mount point 76 can all have the same functionality as a ball joint, or one can be a pin type joint, but the mid arm is provided to give a lever ratio to the mid support 74 between the body and the hull without providing any suspension geometry type location of the hull relative the body. In this example all the of the rams are shown with a similar 3:1 lever ratio, although this can be adjusted to enable common bore sizes between all rams when sized for the same pressure range for example, to increase part commonality. Again, the line 9 indicates a typical waterline on the hull 4.
Conversely the mid supports 74 comprise double-acting rams and interconnections. The mid left support or ram 86 has its compression chamber connected to the rebound chamber of the mid right support or ram 87 by a cross-connecting conduit 88 forming a left roll compression volume which also includes left roll fluid pressure accumulator 27. Similarly the mid right support or ram 87 has its compression chamber connected to the rebound chamber of the mid left support or ram 86 by a cross-connecting conduit 89 forming a right roll compression volume which also includes right roll fluid pressure accumulator 28. In this case damper valves 90, 91 are shown between the fluid pressure accumulators and the remainder of each compression volume which can be beneficial as this location provides a higher roll damping force than heave damping force in the mid supports and also, when active roll control is provided, damping of the roll resilience improves system response and controllability.
To enable active control of the roll attitude, to achieve a coordinated turn for example, again a fluid control system 37 is used. In this example, the fluid control system 37 comprises a bi-directional pump 92 connected to the left and right compression volumes by conduits 42 and 43. A valve can be provided in-line with the pump 92 to ensure that fluid does not flow between the roll compression volumes when no roll adjustment is intended. This arrangement allows a straightforward transfer of fluid between the left and right roll compression volumes. Conversely the arrangement of fluid control system shown in
The back supports 70 are in this example the same as the front supports 6, i.e. the back supports comprise a back left support 95, a back right support 96 and interconnecting conduit 97 although only one fluid pressure accumulator 98 is present as it can be used by both the left and the right supports. Alternatively the back supports can be independent and/or incorporate additional roll rams cross-connected like the mid supports providing additional left and right roll compression volumes which can be connected to the left and right roll compression volumes of the mid supports.
If the mid support rams 86 and 87 (i.e. the roll rams) had rods that extended through the compression chamber as well as the rebound chamber (through rods) then the mid support rams would be able to provide roll forces without providing heave forces. Alternatively, to achieve that same zero heave stiffness functionality, the mid support arrangement of
All of the above examples have been described using variations on leading and trailing arm geometry which maintains a constant width between the hulls measured relative to the body, through heave and roll motions. However as discussed in relation to
An example of an alternative suspension geometry is substantially laterally oriented wishbones as shown in plan view on the vessel in
In this hydraulic actuator example, a front left ram 109 helps to provide support of the body portion 2 above the front left hull 101 via the front left wishbone 105. Similarly a front right ram 110 helps to provide support of the body portion 2 above the front right hull 102 via the front right wishbone 106, a back right ram 111 helps to provide support of the body portion 2 above the back right hull 103 via the back right wishbone 107, and a back left ram 112 helps to provide support of the body portion 2 above the back left hull 104 via the back left wishbone 108. Preferably an additional wishbone or other means of providing roll positioning is provided for each individual hull to control the rotation of the respective hull about its respective (longitudinal) roll axis relative to the body portion.
One possible arrangement of hydraulic interconnection between the rams is also shown in
Another possible arrangement of supports and hulls is shown in
Control of the roll attitude of the vessel can utilise a variety of inputs and produce differing results depending on the inputs chosen and the suspension geometry of the vessel. For example, if the lateral acceleration (in a direction parallel to the deck of the body portion) is measured during a perfectly coordinated turn it will be zero, so the control could use a body mounted lateral acceleration signal (which rotates with the body) and attempt to minimise that signal. However wave inputs accelerating the body could also generate a lateral acceleration signal from a single body-mounted lateral accelerometer. To overcome this, a pair of vertically spaced lateral accelerometers can be utilised, as shown schematically in
Alternatively or additionally the actual centrifugal force FC and the gravitational force FG can be measured (for example using gyro-stabilised accelerometers or a set of accelerometers which include compensation for rotation of the accelerometers relative to the ground or other reference frame), then the angle θ of the resultant force can be calculated and the angle Φ of the body portion adjusted to be equal (to θ) as shown in
Similarly the loads on the suspension supports, the pressures in any fluid actuators and/or the hull-to-body or actuator positions can be measured to prevent excessive adjustments being made, for example to ensure that all roll attitude adjustments are made within suspension travel limits and/or hydraulic system pressure limits. Similarly other limits can be incorporated into the control such as only providing a coordinated turn up to a preset lateral acceleration, beyond which the roll angle can either be maintained at the angle corresponding to that lateral acceleration, or rolled to an amount that is less than a perfectly coordinated turn, to give feedback to the pilot of the vessel that cornering acceleration is high.
In each of the preceding cases, measuring acceleration or suspension loads, the centrifugal force must already be acting for the acceleration or load changes to be detected, but for the centrifugal force or roll loads to be present, the roll attitude of the vessel will typically have already started to move, potentially in the opposite direction to the aim for roll angle of the body portion during a coordinated turn. To reduce or eliminate this phase lag, it is preferable to measure a steering angle (rudder and/or propulsion thrust direction) and vessel speed to calculate or predict the centrifugal force and enable the control of the roll attitude of the body portion to be commenced prior to significant lateral acceleration (due to centrifugal force) building. As the steering angle can be changed faster than the boat will respond in roll, a function of time can be incorporated to control and/or limit the rate of change of roll attitude of the body portion. This is not only beneficial to occupant comfort, but is useful to prevent overshoot of roll angle changes.
A further benefit of including steering and speed inputs into the control of the roll attitude for a coordinated turn is one of low control forces and energy input. If a fluid suspension arrangement is providing all of the roll stiffness of the suspension system between the body portion and the hulls, and assuming that the vessel is balanced left to right in an ideal case, then the pressure difference between the left and right roll volumes will be zero statically. Also if the roll attitude of the body portion is continually adjusted so that the change in vertical force on each hull due to the lateral shift of the body portion centre of mass is equal and opposite to the change in vertical force on each hull due to the couple reacting the roll moment generated by the centrifugal force, then the pressure difference between the left and right roll volumes will remain minimal. Therefore to adjust the roll attitude of the vessel, sufficient pressure is required to create the desired rate of change of roll attitude of the body, i.e. to overcome rotational inertia, but additional pressure is not then required to compensate for the roll moment generated by the centrifugal force (due to the roll moment generated by the lateral shift of the body portion centre of mass) since this is minimised.
A simplified control flow diagram is shown in
In this example, the calculated or predicted lateral acceleration is used to calculate the corresponding roll attitude for a perfectly coordinated turn. This assumes that the lateral acceleration is absolute, ie relative to ground, not relative to the body of the vessel. Alternatively, if the lateral acceleration is only taken from one or more lateral accelerometers that are mounted on the body, then the lateral acceleration is measured using a reference frame that is relative to the body. Therefore then minimising the lateral acceleration should keep the vessel roll attitude in a coordinated turn attitude where the sum of the gravitational force and the centrifugal force acting on the vessel during a turn is perpendicular to the deck of the vessel. In this case it is preferable to use two vertically spaced lateral accelerometers, then average the detected accelerations to separate the lateral acceleration on the body (oriented laterally with respect to the body) from any roll accelerations on the body.
Returning to
If the hull positions relative to the body are not input, then at 146 instead of calculating a roll angle or roll attitude change, a parameter relating to direction of roll angle adjustment and preferably also to magnitude of change required, can be determined and passed directly to 152 to generate control signals which adjust the roll attitude of the vessel body. The control signals can for example, in the case of the hydraulic control system 37 of
The calculated or predicted lateral acceleration 143, 144 and/or the adjusted (ie leeway compensated) steering angle 160 together with speed 54 can then be used in 164 to determine the roll angle for a coordinated turn following the possible path 165. Alternatively, if suspension support force signals 167 (or pressures or other signals indicative of support forces) are also input, then at 164 the alternative path in 166 can be followed and the roll attitude determined to optimise efficiency and/or maintain the load balance between the left and right hulls. Where load change on the hulls is primarily due to lateral acceleration and the payload does not move significantly, the suspension forces can be used to calculate lateral acceleration. In this case, the lateral acceleration and hull position signals are not essential, but can be used as a check to ensure that a load-based adjustment is not causing a significant roll angle difference to a coordinated turn (say less than three or four degrees for example). The control unit for the suspension system can use either of the coordinated turn or load optimised paths in calculating block 164 or even a combination of the two which could be selected by the pilot or determined automatically depending on operating conditions such as sea state and/or speed. For example if the vessel is not planing it can be preferable to optimise for a coordinated turn, but when at planing speeds, it can be preferable to optimise for load balance to ensure efficiency and that the vessel continues to plane while cornering.
After the calculating block 164 the roll attitude adjustment or aim 168 is set, either for a perfectly coordinated turn, or to maintain the load balance between or minimise a load difference between the left and right hulls, or a combination of the two so the roll attitude is between the angle for a coordinated turn and the angle for load balance. However, the suspension support force or equivalent signals 167 can at 169 also be used to determine if there is an uneven load between the left and right hulls due, for example, to an offset load or payload on the body. If not the roll attitude adjustment from 168 can be passed directly to the output signals of 171 to effect adjustment of the roll attitude of the body relative to the hulls. If however at 169 it is determined that there is an offset load on the body portion, then again the balance or compromise between coordinated turn and balanced hull loads can be determined at 170 before the control unit outputs roll attitude adjustment signals at 171, particularly if, in the initial roll attitude determination in 164, the coordinated turn path 165 was followed without taking suspension loads from 167 into account.
If there is a lateral shift of the load on the deck (i.e. if many passengers go to one side of the vessel to look at something or if a load is added, moved or removed), while using a body mounted lateral accelerometer will enable the deck to be controlled to maintain a level position, the load balance between the left and right hulls changes, which may affect efficiency. Conversely if the control of the attitude of the deck and body is primarily driven by the forces and/or pressures in the left and right support devices, the body will be rolled upwards on the side where the load is greater, but the balance between the hull loads will be maintained during the load shift. Therefore it can be beneficial to use both functions (including measured, calculated or predicted lateral acceleration or support device loads or pressures) to arrive at the desired balance between the occupants feeling no lateral acceleration and maintaining the force balance between the left and right hulls. So any control strategy can use any or all of: lateral acceleration; speed and steering angle; and support loads or pressures, or other parameters enabling the prediction of lateral acceleration.
An offset can be used as a variable that changes at a lower frequency than the sensor scanning rate and can be used to adapt the control of the roll attitude. One such example would be the leeway angle in 160, and as parameters such as the vessel heading or the wind direction change, the offset can be updated. Similarly an offset can be used to adapt the control of the roll attitude for load offsets as detected at 167 and updated as the load shifts. To prevent sudden or unnecessary changes in such an offset which could generate unwanted and potentially abrupt changes in roll attitude (angle of the body portion) the rate of change of the offset can be limited, such as a decay function based on time and potentially other inputs such as the initial magnitude of the offset, lateral acceleration, speed, steering angle and/or at least one load on at least one hull or at least one suspension member such as a ram.
Similarly the rate of change of roll attitude aim or roll attitude adjustment magnitude can be limited to effectively damp the control to provide a more comfortable ride on the vessel body and/or to increase efficiency by effectively smoothing the control output signals.
The invention can be applied to any multi-hulled vessel where at least two hulls move relative to each other. Although previous inventions have enabled mono-hull vessels to make coordinated turns for passenger comfort and stability reasons, they have had to use interceptors, ailerons or other flaps or wings to drive the change in roll angle. These all require continued loss of power through drag or equivalent resistances to provide the forces that are adjusting the roll angle of the vessel from its natural inclination. The advantages of the present invention are unique to multi-hulled vessels in which the attitude of the body portion can be rolled and primarily relate to reduced power consumption or increased efficiency. For example if the roll attitude adjustment system includes a hydraulic system, then once the roll attitude of the body portion has been adjusted to an angle corresponding to a coordinated turn (i.e. the resultant of the gravitational and centrifugal forces acts perpendicular to the deck), then typically no power is required to maintain it there.
There are many possible forms of adjustment means for taking fluid from one of conduits 42, 43 (connected to the respective roll volumes) and supplying it to the other of said conduits, as shown by the variety of fluid control systems 37 in the Figures.
The suspension system can be of any type that allows adjustment of the roll attitude, so need not be hydraulic system based with powered roll attitude adjustment and can alternatively include motor-generators, for example in the form of linear actuators as discussed in the Applicant's U.S. Pat. No. 7,314,014 and in relation to
The body portion of the vessel may engage the water surface, i.e. the body portion may include an additional hull. For example in the case where a single left hull and a single right hull is utilised, if the body is entirely suspended above the left and right hulls and not engaging with the water as shown in
Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014901832 | May 2014 | AU | national |
| 2014902211 | Jun 2014 | AU | national |
| 2015900786 | Mar 2015 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2015/000287 | 5/15/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/172188 | 11/19/2015 | WO | A |
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| Entry |
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| European Search Report for Application No. 15792828.4 dated Dec. 1, 2017 (8 pages). |
| International Search Report and Written Opinion for Application No. PCT/AU2015/000287 dated Jun. 15, 2015 (9 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20170088235 A1 | Mar 2017 | US |
