ITRM20100221A1 - STEERING SYSTEM FOR VESSELS - Google Patents

Description

STEERING SYSTEM FOR BOATS

Description

The present invention relates to a steering system for boats which comprises at least two directional surfaces or rudders.

By directional surface we mean, in the following, any mobile hydrodynamic control surface, therefore a rudder blade, a flap, any hull appendage or the like.

Steering systems as specified above are known.

US Patent No. 4,388,889 describes a steering system with hydraulic control of the rudder blades, in which the inclination and rotation speed of the blades are limited, in relation to the forward speed of the vessel, to limit the roll, in particular to facilitate the landing of aircraft on the upper deck.

US Patent No. 5,488,919 describes a dual rudder steering system, in which the two blades are tilted and rotated asynchronously to improve the roll and pitch control of the boat.

However, the systems known in the art do not allow precise control of roll and pitch during the whole range of maneuvers that are foreseen for a vessel, thus reducing the comfort on board the vessel itself.

The aim of the invention is to impart, by means of an optimal control of the movement of the rudders, a system of forces to the vessel such as to improve the running characteristics, in particular the speed of approach and / or decrease in resistance to motion in the approach phase itself, at the same time controlling roll and pitch, thus optimizing turns and also generating a hydrodynamic brake as the vessel moves forward.

The technical problem underlying the present invention is to provide a steering system which allows to overcome the drawback mentioned with reference to the known art.

This problem is solved by a system as specified above which is characterized by the fact that it includes:

â € ¢ two or more directional surfaces controlled by respective independent electric motors on corresponding rotation axes;

â € ¢ means for identifying, for each directional surface, the position of least torque in correspondence with each axis of rotation; And

means for controlling the rotation of said directional surfaces by a predetermined angle with respect to said position of least torque.

The main advantage of the steering system according to the present invention resides in allowing a continuous dynamic control of the position of each rudder, adjusting it in an optimal way.

The present invention will be described below according to an example of its preferred embodiment, provided by way of non-limiting example with reference to the attached drawings in which:

â € ¢ Figure 1 shows a perspective and schematic view of the stern of a boat with a steering system according to the present invention;

â € ¢ Figure 2 shows a block diagram which visually illustrates the various components of the steering system of Figure 1;

â € ¢ figure 3 shows a block diagram illustrating the operating logic of the steering system in figure 1.

The present invention consists in synthesis in an electromechanical and electronic directional system for naval means, controlled by a software procedure suitable to move a series of rudders or, in general, any type of directional surface.

The fundamental principle of the innovation is to manage the independent movement of at least two rudders for marine vehicles with speed, precision and repeatability.

With reference to the figures, a boat is indicated by 1 and, in correspondence with its stern wall, a steering system is described which includes, in the present example, two rudder blades 2 whose respective axis is connected directly to an electric motor 3 coupled to a gearmotor 4 characterized by a large reduction ratio, in order to have a high degree of control of the movements of the blades.

Each electric motor 3 has a special PLC which is able to continuously record the position of the respective rudder blade allowing, by means of an algorithm, to orient the rudders themselves in an optimal position to perform a desired maneuver as will be evident in the following.

The steering system also includes an interface for operating the rudders and instructions to the rudders, which can be mechanical and / or electronic to manage simple movement and advanced rudder functions.

In detail, the steering system of this example comprises a control unit (controller) to which means are connected for the detection of sensitive data useful for the maneuvering of the directional surfaces.

In particular, the controller (figure 2) is connected to an inertial platform conveniently made up of sensors to determine the angle of inclination of the vessel in a transverse (roll) and longitudinal (pitch) direction. In sensors they can be of the resistive type.

Optionally, said platform can also include a set of accelerometers for determining the various accelerations on two or three axes.

In addition, the controller is connected to an electronic compass and a global positioning system (GPS).

The controller is therefore connected to said electromechanical / electronic interface, in particular of the â € œsteer by wireâ € type, in which the traditional tie rods are replaced by a wire system of electric controls, connected to the actuators of the directional surfaces through the controller.

Controls can be given via a steering wheel, joystick, joystick and the like.

Finally, there is a control interface, for example for setting up the steering system.

Through the controller, it is possible to use preset laws to the motion of the rudders, through a special software and with an algorithm designed to process the load information of the individual rudders and process the consequent actions.

The structure of the algorithm can be summarized as follows.

Straight course:

The rudders during a straight-line navigation are moved around the position initially identified by the operator, until the system identifies the condition of lower torque on the axes of both rudders.

Turn:

The pilot operates the steering wheel to set the turn; the sensor transmits the angle of tack to the controller which calculates the derivative with respect to the time of the angle. With this data, the controller decides whether to operate the quick turn or efficient turn mode. Then, it sends to the rudders the angle of rotation they will have to reach. The system will perform a minimum torque control on the rudder outside the turn, in order to place the rudder itself at a predetermined angle with respect to that of the minimum torque.

Braking:

a proportional control operated manually by the pilot activates the function that allows the rudders to be steered in order to intercept the flow coming from the propellers in order to divert it and generate the brake action. It is implied that course control relaxes the constraint on braking intensity.

Reverse gear:

a manual command will allow the controller to activate the reverse function. The rudders will rotate 180 ° and the steering wheel will control the rudders with the same laws of forward gear but starting from this new â € œzeroâ €.

Figure 3 shows a diagram of the structure of the algorithm implemented with the stability control. The diagram illustrates, for the sake of brevity, the main variables, the others have the same logic scheme and can only be considered as a repetition of n functions. The algorithm will consider the sum of the effects and a series of coefficients â € œkâ €, calculated experimentally, will correct the phenomena that cannot be modeled with the simple superposition of the effects.

Below is the legend of the input-output signals

INPUT:

Unit

Name Type of Description

measure

Unit

Name Type of Measure description

Course reference (determined by the steering wheel sensor or by phi_d float degrees preset algorithm and controlled through the human / machine interface system) Measured yaw angle (from the compass phi_m float degrees

or from the inertial platform) Yaw angle derivative (derived d / dt (phi) float degrees / s from the measurements from the electronic compass or platform) Roll and / or pitch angle measured psi_m float degrees (from the inertial platform or from the angle sensors)

Unit

Name Type of Measure description

Derivative of the angle of the motions (from the platform d / dt (psi) float degrees / s

inertial or angle sensors) OUTPUT:

Unit

Name Type of Range Description of measure

-

alpha float degrees Rudder angle

90 °, 90 °

The control algorithm must be performed with TS sampling period. In consideration of the expected dynamics, TS â ‰ ˆ 0.1s is expected.

At each sampling instant Ts, the control algorithm determines the new value of the desired rudder angle (alpha), on the basis of the angles measured and the control strategy implemented:

alpha (k + 1) = f (psi_d (k) - phi_m (k), psi_m (k), d / dt [psi (k)], d / dt [psi (k)]) The alpha angle will be calculated, in principle, as the sum of two contributions:

1. Contribution deriving from the Steering controller (to execute the desired route, or to make the turns);

2. Contribution from the Stabilizer Controller (for damping the oscillations). It is implied that the need to dampen the motions relaxes the constraint on the accuracy of the tracking of the route.

It should be noted that the sensor system designed to detect the movements of the ship and transfer the information to the electronic system is not essential for the present invention, but is necessary for additional implementations.

The electromechanical rudder movement system associated with an electronic control allows the rudder movements to be controlled with extreme precision, speed and repeatability. Thanks to this feature it is possible to give a series of motion laws to the rudders that allow to:

â € ¢ Position the rudders at the optimal angle, therefore of minimum resistance, for all conditions of motion;

â € ¢ to perform turns with a particularly small turning radius (the internal rudder reaches much greater angles than the external one in order to generate a high resistance and consequently a high yaw torque)

â € ¢ perform wide radius turns but offering reduced resistance to the boatâ € ™ s motion (the rudders orient themselves with respect to the flow, each reaching an optimal angle of attack; in fact this angle is also a function of the position of the rudders with respect to the center of the turn .

Thanks to the possibility of dynamically adjusting the optimal angle of attack of the rudders, the rudder blades are installed on an axis inclined with respect to the traditional vertical axis (figure 1). This particular installation is not commonly used because the rudders, arranged in this way, form an angle with respect to the fluid which is variable with the attitude of the boat, and therefore impossible to cancel in a static way. The advantage of positioning the rudders inclined with respect to the vertical axis is to facilitate the control of the rolling and pitching motions as well as the attitude.

In the present example, the inclined assembly is obtained by using suitable mounting brackets 5 fixed to the stern wall, which also support the respective electric motor and the gearmotor. The axis of the bracket 5 determines the inclination of the blade.

However, it is understood that the axes of the directional surfaces can be mounted directly on the transom or under the hull depending on the specifics of the application.

Further advantages related to the invention are those of carrying out the dynamic control of the attitude and of the rolling and pitching motions of the boat. With the aid of an appropriate network of sensors, which can record the motions of the boat, it is possible to give the rudders a law such that they induce a system of forces to the marine vehicle capable of opposing the motions of the boat itself.

The rudder blades are, unlike normal applications, independently controlled from each other. This feature makes it possible to use these appendices for the realization of multiple functions.

Contrary to what happens in normal applications, the rudders are controlled by an electric motor and gearmotor unit capable of carrying out the movements required by the algorithm, with precision, speed and repeatability that cannot be reached by traditional systems which usually include hydraulic actuators.

This innovation opens up the possibility of using the rudders in such a way as to significantly expand their functions, which is not possible with classic actuation systems.

The directional hydrodynamic control surfaces considered are simple rudder blades, but a similar effect can be achieved, using the same logic system with the use of other hull appendages (flaps, hydrodynamic control surfaces arranged along the hull etc. .).

Furthermore, it can be envisaged to amplify the effects of the described invention, applying the same principle to further fluid dynamic control surfaces.

It is possible to foresee a development of the rudder blades by dividing their surface, in order to allow a relative rotation of the two parts (rudder and flap) with respect to the absolute one relative to the naval vehicle. The splitting of the rudder blades, if controlled by the electric / electronic system, can increase the new functions of the rudders themselves.

It is also possible to foresee the use of rudders and / or other types of hydrodynamic control surfaces (for example flaps) which, activated by the suitably programmed electric / electronic system, can act as a propulsion system for the marine vehicle by exploiting the effect of the so-called kicking. This function, only possible in the presence of an electronically controlled electric movement system, also allows the marine vehicle to be stabilized even at mooring.

The salient part of the invention is the possibility of acting on hydrodynamic control surfaces, giving them an appropriate law of motion capable of imparting to the boat a system of forces such as to modify its equilibrium (motions around the axes of roll, attitude and yaw). It is important to point out that all the positive effects deriving from the invention are generated by the simple separate movement of the rudders and / or generic fluid dynamic control surfaces, but it is not possible to achieve these advantages if there is no electronic system to supervise the system. electrical / mechanical to implement the movements themselves.

In order to satisfy further and contingent needs, a person skilled in the art may make numerous further modifications and variations to the above-described steering system, all of which however fall within the scope of protection of the present invention, as defined by the attached claims.

Claims (9)

CLAIMS 1. Steering system for boats that includes at least two directional surfaces, characterized by the fact of including: â € ¢ two or more directional surfaces controlled by respective independent electric motors on corresponding rotation axes; â € ¢ means for identifying, for each directional surface, the position of least torque in correspondence with each axis of rotation; And means for controlling the rotation of said directional surfaces by a predetermined angle with respect to said position of least torque. 2. System according to claim 1, wherein the axis of said directional surfaces is directly connected to a respective electric motor (3) coupled to a gearmotor (4) with a high reduction ratio, each electric motor (3) presenting a special PLC capable of continuously recording the position of the respective directional surface. 3. System according to claim 1 or 2, which comprises a control unit (controller) to which said means are connected for identifying, for each directional surface, the position of least torque in correspondence with each axis of rotation and said means to control the rotation of said directional surfaces by a predetermined angle with respect to said position of least torque. System according to claim 3, wherein the controller is connected to an inertial platform. 5. System according to claim 3 or 4, wherein the controller is connected to sensors to determine the angle of inclination of the vessel in the transverse (roll) and longitudinal (pitch) direction. 6. System according to claim 3, wherein the controller is connected to an electromechanical / electronic interface of the â € œsteer by wireâ € type. 7. System according to claim 4 or 5, in which the controller operates according to a software with which, at each sampling instant Ts, a control algorithm determines a new value of the desired rudder angle (alpha), on the basis of the angles measured: alpha (k + 1) = f (psi_d (k) - phi_m (k), psi_m (k), d / dt [psi (k)], d / dt [psi (k)]) where: phi_d is the route reference determined through an interface; phi_m is the yaw angle; psi_m is the roll and / or pitch angle measured. System according to claim 1, wherein the directional surfaces are installed on an inclined axis. 9. System according to claim 8, in which the inclined assembly of the directional surfaces is obtained by using special mounting brackets (5) fixed to the stern wall, in which the axis of the bracket (5) determines the inclination of the ™ axis of the directional surface. p.p. Flexitab S.r.l.