WATERCRAFT SPEED SENSOR

Abstract

A sensor for measuring movement of an object relative to a fluid has a housing fixed to a surface of the object and a spring on the housing formed by a plurality of blades each having an outer end fixed to the housing and an inner end connecting to a hub, with the plurality of blades defining a plane. Respective strain gauges are carried on the blades. A rigid pin is mounted on the hub of the spring, extends in a direction generally perpendicular to the plane, and projects from the surface of the object and into the fluid.

Claims

1. A sensor for measuring movement of an object relative to a fluid, the sensor comprising: a housing fixed to a surface of the object; a spring on the housing formed by a plurality of blades each having an outer end fixed to the housing and an inner end connecting to a hub, the plurality of blades defining a plane; respective strain gauges on the blades; and a rigid pin mounted on the hub of the spring and extending in a direction generally perpendicular to the plane and projecting from the surface of the object and into the fluid.

2. The sensor according to claim 1, wherein the plurality of blades comprises at least three blades.

3. The sensor according to claim 1, wherein the blades are arranged angularly equidistant from each other relative to an axis of the hub.

4. The sensor according to claim 1, wherein the plurality of strain gauges comprises at least three strain gauges positioned on three different blades.

5. The sensor according to claim 1, wherein the pin carries a float.

6. The sensor according to claim 1, wherein the housing comprises a cover flush to the surface of the object.

7. The sensor according to claim 6, wherein the cover has a bore through which the pin extends and having an inner diameter larger than an outer diameter of the pin.

8. The sensor according to claim 1, wherein the spring assumes a rest position for the pin when no forces act upon the pin.

9. A sensor for measuring movement of an object relative to a fluid, the sensor comprising: a housing fixed to a surface of the object; a base fixed to the housing and defining a plane; am elastically deformable pin mounted of the base, extending generally perpendicular to the plane, and projecting from the surface of the object into the fluid; and a plurality of strain gauges on the pin.

10. A system for determining information about a movement of an object relative to a fluid, the system comprising: a sensor as defined in claim 1, a first communication unit on the object and connected to the sensor, and a second communication unit receiving information from the first communication unit.

11. The system according to claim 10, further comprising: a calculating unit configured to calculate from information received from the strain gauges of the sensor a velocity of the object and a direction of movement of the object relative to the fluid.

12. The system according to claim 11, wherein the calculating unit uses GPS-information about the object for calculating a velocity of the object and a direction of movement of the object relative to the fluid.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0055] The above and other objects, features, and advantages will become more readily apparent from the following description, it being understood that any feature described with reference to one embodiment of the invention can be used where possible with any other embodiment and that reference numerals or letters not specifically mentioned with reference to one figure but identical to those of another refer to structure that is functionally if not structurally identical. In the accompanying drawing:

[0056] FIG. 1 is a side view of a first embodiment of the sensor of the invention incorporated in a surfboard;

[0057] FIG. 2 is a bottom view taken in the direction of arrow II of FIG. 1 of the surfboard of FIG. 1;

[0058] FIG. 3 is a large-scale section taken along line of FIG. 2;

[0059] FIG. 4 is a front perspective view of a first embodiment of a 4-blade sensor according to the invention in a perspective schematic view;

[0060] FIG. 5 is a partly exploded back perspective view of the sensor of FIG. 4 in a perspective back view according to arrow V of FIG. 4 with four strain gauges;

[0061] FIG. 6 is a large-scale view of a second embodiment of a 4-blade sensor similar to that of FIG. 4 in a different perspective and showing differently formed blades;

[0062] FIG. 7 a schematic exploded view of a third embodiment of the sensor of the invention;

[0063] FIGS. 8 and 9 show the embodiment of FIG. 7 when partly and fully assembled;

[0064] FIG. 10a is a schematic cross section through the sensor of FIG. 4 without float in a position where no forces act upon the pin so it is in its rest position;

[0065] FIG. 10b shows the sensor of FIG. 10a when a first force F is exerted upon the pin;

[0066] FIG. 10c, 10e show the sensor of FIG. 10a in further positions of the pin and the blades under action of different forces F acting in different directions onto the pin;

[0067] FIG. 11 is a schematic of an electric Wheatstone bridge circuit with embedded strain gauges;

[0068] FIG. 12 shows a fourth embodiment of the sensor according to the invention in a view like FIG. 6 with a 3-blade sensor having three unillustrated strain gauges;

[0069] FIG. 13 shows a fifth embodiment of the sensor of the invention in schematic illustration similar to FIG. 3 showing a flexible pin carrying strain gauges;

[0070] FIG. 14 is a schematic diagram illustrating an embodiment of a system according to the invention comprising an object configured as a watercraft in water and having a first communication unit, a second communication unit mounted on the shore, and a satellite;

[0071] FIG. 15 is a sixth embodiment of the sensor according to the invention in an illustration similar to FIG. 3 showing a membrane for detecting z-directional forces acting on the pin; and

[0072] FIG. 16 shows a seventh embodiment of the sensor of the invention in an illustration similar to FIG. 3 showing a membrane in the housing, near or at the blades.

SPECIFIC DESCRIPTION OF THE INVENTION

[0073] Numerous embodiments of the invention are shown in the drawings described in the following description of the figures and under reference to the drawings only in an exemplary way. For the sake of clarity identical parts or parts having identical functions have been designated with the same reference numerals, in part by adding small alphabetic characters, even for different embodiments. Features that have been disclosed only in reference to one single embodiment can, within the frame of the invention, also be provided in any other embodiment of the invention. Such embodiments are also comprised of the invention, even if such embodiments are not disclosed in the drawings.

[0074] All features disclosed in the following description are relevant to the invention. In the disclosure of this patent application there is also included the disclosure of any cited prior art documents and prior art sensor, including for the purpose to take up one or several features of those prior sensors into one or more claims of the present patent application.

[0075] An embodiment of a sensor according to the invention is designated in its entirety in the drawing with reference numeral 63. It will be referenced to in view of the object 10. The object 10 is schematically shown in the drawings as a surfboard 11. This surfboard 11 is used in a fluid 12 that in the present case is water.

[0076] According to FIGS. 1 and 2 the surfboard 11 might have a plurality of skegs 14a, 14b, 14c. A middle axis of the surfboard 11 is designated with the reference numeral 15 and the direction of travel 16 of the surfboard 11 will mostly be parallel to the middle axis 15.

[0077] The sensor 63 is on the underside 64 of the surfboard 11 and is, as can be seen from FIG. 2, positioned advantageously on or near to the middle axis 15 of the surfboard 11.

[0078] FIG. 3 shows an enlarged schematic cross section view of FIG. 1 according to circle III.

[0079] The sensor 63 will be now described in detail in view of FIG. 3:

[0080] The cross section of FIG. 3 shows the inner structure of the surfboard 11 including an internal foam 19 that might be a light weight foam, for example made of polyurethane, and hard skin surfaces 20a, 20b that may consist of resin and glass fibers. The sensor 63 comprises a housing 21 inset into the surfboard 11 and thus fixed thereto. The housing 21 receives a ring 22 fixed to the housing 21.

[0081] Four angularly equispaced blades 25a, 25b, 25c, 25d extend radially inward from an inner face of the ring 22. The outer end 27 of each blade 25a, 25b, 25c, 25d is fixed to the ring 22. The inner ends 28 meet in a hub 65. The plurality of blades 25a, 25b, 25c, 25d form a spring 62 and lie in a common plane 73.

[0082] A pin 17 is fixed to the hub 65 of the spring 62 and is cylindrical and has a circular cross section. The pin 17 extends in a direction 74 perpendicular to the blade plane 73. The pin 17 is made of a stiff, rigid material such as metal or hard plastic and does not bend when radial forces are exerted on the pin.

[0083] FIG. 10a shows a rest position of the pin 17. The spring 62 urges the pin 17 into this rest position.

[0084] If a radial force is applied to a free end 66 of the pin 17 (see FIG. 10b), the pin 17 will pivot from the position according to FIG. 10a into the position according to FIG. 10b.

[0085] Since the pin 17 is rigid and stiff and will not bend, the spring blades 25a, 25c will bend as can be seen in comparison of FIGS. 10a and 10b.

[0086] According to FIG. 3 the housing 21 of the sensor advantageously is closed by a cover 23. The cover 23 has a bore 24 through which a pin 17 extends.

[0087] As can be seen in FIG. 3, there is an annular space 67 between the bore 24 and the pin 17 to allow movement of the pin 17 as shown in FIGS. 10a to 10c. The bore 24 thus has an inner diameter 75 larger than the outer diameter 76 of the pin 17.

[0088] Movements shown in FIGS. 10b and 10c are for purpose of illustration only and that in real applications only very small angles, for example of much less than 1, will be reached.

[0089] According to FIG. 5, which is an exploded view, there are four strain gauges 26a, 26b, 26c, 26d provided on the back faces 30 of the blades 25a, 25b, 25c, 25d. Other embodiments of the invention that are not shown in the drawings provide strain gauges on the front faces 29 of the blades 25a, 25b, 25c, 25d. All embodiments shown in the drawings only show strain gauges 26a, 26b, 26c on the back side 30 of the blades 25a, 25b, 25c, 25d.

[0090] Strain gauges that can be employed in the embodiments of the invention are standard known electronic elements. Strain gauges appropriate for use with the invention are commercially available for example at Hottinger Baldwin Messtechnik GmbH in 64293 Darmstadt, Germany.

[0091] According to the invention strain gauges 26a, 26b, 26c and 26d are glued to the back faces 30 of the blades 25a, 25b, 25c, and 25d and then covered with an insulating material like silicone or resin. The strain gauges 26a, 26b, 26c connected are via cables 34a, 34b (see FIG. 3) connected to other electronic elements and/or are part of an electric circuit 44 that will be explained later under reference to FIG. 11.

[0092] Strain gauges 26a, 26b, 26c, and 26d employed according to the embodiment of the invention are preferably linear strain gauges. The strain gauges that can be used within the invention change their electrical resistance if the blades 25a, 25b, 25c, 25d, on which the strain gauges 26a, 26b, 26c, 26d are glued undergo a change in length.

[0093] As can be seen in comparison of FIGS. 10a and 10b the portion of the back side 30 of blade 25a will be elongated when the pin 17 is pivoted from the position of FIG. 10a in the position of FIG. 10b, while the length of portion of the back side 30 of the blade 25c will shortened at the same time. This length discrepancy will lead to discrepancy in the resistance of the strain gauges 26a, 26c.

[0094] According to the embodiments of FIG. 3 to FIG. 10e the two strain gauges 26a and 26c are positioned on two blades 25a, 25c that are arranged exactly opposite to each other. Any change in resistance of strain gauge 26a therefore will be the same at the opposing strain gauge 26c, however with a negative effect.

[0095] Using an appropriate electrical circuit, these changes in resistance of the strain gauges 26a, 26b, 26c, 26d can be measured and can be used to obtain information about forces F exerted on the pin 17.

[0096] If for example according to FIG. 10b a force F is exerted on the pin 17, this will lead to a certain movement of the pin 17 that will result in a certain change in the electric resistances of the two strain gauges 26a, 26c.

[0097] If however a contrary force F according to FIG. 10c is exerted onto the pin 17 as shown in FIG. 10c, in the opposite direction compared to FIG. 10b, then different behavior of the deviation of the resistances of the strain gauges 26a, 26c will be detected.

[0098] The detection of the changes in resistance of the strain gauges 26a, 26b, 26c, 26d can be employed to derive information about the force F exerted onto the pin 17. From the information about the strength of the force F and from the direction of the force F information about the current direction D of the object 10 relative to the fluid 12 and of the velocity of the object 10 relative to the fluid 12 can also be calculated.

[0099] According to the FIGS. 10a to 10c it has been shown that detection of the change of resistance of the strain gauges 26a and 26c yields information about the force F acting in x-direction, or information about the part of the force F acting in x-direction can be employed. It is also possible by using the strain gauges 26b and 26d to obtain information about the strength of the forces F acting in y-direction. Thus, detection of the differences in the resistance of the strain gauges 26b, 26d can be used to derive information about the direction and the force F that have been exerted onto the pin 17 in y-direction.

[0100] According to FIGS. 1 and 2 the direction of travel 16 of the surfboard 11 is designated with an X, the direction transverse thereto is designated Y and the vertical direction is designated Z.

[0101] It shall be assumed that the strain gauges 26a, 26c of the sensor 63 shown in FIG. 10a are positioned in such a way at the surfboard 11 that they are lie on a line that is parallel to the direction X. If the surfboard 11 moves exactly in the direction of travel 16 through the water 13, then the force F according to FIG. 10b would be exerted onto the pin 17.

[0102] If however the surfboard 11, for whatever reason, made a reverse movement in direction X, the force F as shown in FIG. 10c would be exerted onto the pin 17 and a reverse change of resistance of the strain gauges 26a, 26c would be sensed.

[0103] The same applies for strain gauges 26b and 26d that under the previous assumption, would be oriented in this embodiment in the direction Y transverse to the direction X.

[0104] Also the changes of resistance of the strain gauges 26b, 26d are detected through the electric circuit 44.

[0105] From the measurements one can not only derive information about the relative speed of the object 10 relative to the fluid 12, but also information about the direction of the speed, thus indicating the direction of relative movement of the object and the fluid.

[0106] Regarding FIGS. 10d and 10e:

[0107] Some embodiments of the sensor 63 of the invention might include a float 43 schematically shown in the embodiments of FIGS. 5, 10b to 10e.

[0108] This float 43 can for example be a disk and can be used to measure the buoyancy of the object 10 relative to the fluid 12 The disk float 43 can for example be on the lower free end 66 of the pin 17.

[0109] If a force is exerted on the float 43 in the direction z or in direction z as shown in FIG. 10d, then starting from the state of the sensor 63 as shown in FIG. 10a the pin 17 is drawn downward, which will lead to a change in resistance of both of the strain gauges 26a, 26c.

[0110] The same applies analogously if an upward (Z-direction) force F is exerted against the float 43 according to FIG. 10e that will lead to stretching of the portion of the back face 30 of the blades 25a, 25c again resulting in a change in resistance of the strain gauges 26a, 26c commonly.

[0111] While it is clear that the change in resistance of strain gauge 26a and strain gauge 26c according to FIG. 10d will be same or will approximately be the same, it is also clear, that the same effect will take place in a position as shown in FIG. 10e, however with a negative i.e. inverse way.

[0112] Therefore, a measurement of the change of resistance of the strain gauges 26, 26c can also give information about whether or not a force F is exerting onto the pin 17 in z-direction or in z-direction and also information about the amount of the force F in z-direction.

[0113] Therefore, an appropriate electronic circuit 44 as shown in FIG. 11 can differ between movements of the pin 17 relative to the spring 62 in all three different directions x, y and z. This will permit receiving vector information about the direction and the length of the force vector of the force F applied to the pin 17.

[0114] For clarification it is pointed out to the fact that all embodiments shown may include a float 43 or may not include such float 43.

[0115] All embodiments of the invention as shown in the drawings can also operate without a float 43 and still permit to the user to obtain information about the forces F in x- and y-direction.

[0116] In many applications there will be no need for obtaining information about z-directional forces F. So such a float 43 can be omitted for such applications.

[0117] For further explication it is noted that the length L1 of the pin 17 and the length L2 of the pin 17 projecting from the surface 20 of the object may differ in dependency of the different conditions.

[0118] It is important for the invention that the free end 66 of the pin 17 reach a zone in the fluid 12 called the free layer zone.

[0119] Between the free layer zone and the surface 20 there might be a turbulent laminar zone of fluid 12 that might lead to incorrect measuring and values and results.

[0120] A turbulent zone of fluid 12 might be part of the fluid in movement due to the movement of the object and measurements within this turbulent zone of fluid might not be representative and might result in incorrect measurement values.

[0121] All strain gauges 26a, 26b, 26c, 26e are connected via cables 34a, 34b to further electronic components of an electronic circuit.

[0122] The circuit 44 is shown in detail only in FIG. 11. The electronic circuit may include one or more electronic elements 33a, 33b and/or one or more microprocessor (not shown).

[0123] According to FIG. 11 there is a power supply/voltage source 51 provided and connected to all strain gauges 26a, 26b, 26c, 26d that are in the circuit diagram symbolized by resistances.

[0124] The strain gauges 26a and 26b are parallel and the strain gauges 26b and 26d are parallel.

[0125] Further resistances R1, R2, R3 and R4 are provided.

[0126] The output voltage at the strain gauges 26a, 26c, that is an indication for the resistance of the strain gauges or for the change of resistance of the strain gauges, is connected to the input side of a first differential amplifier 46a. The output of this first differential amplifier 46a provides the first output signal 48 that gives an x-direction signal.

[0127] The strain gauges 26b and 26c are connected to the input of a second differential amplifier 46b whose output corresponds to the output 49 (signal output) that is for the y-direction signal.

[0128] The output of the first differential amplifier 46a and the output of the second differential amplifier 46b are connected to the input of a summing amplifier 47, whose output is the output signal 50 corresponding to the signal in z-direction.

[0129] The circuit 44 as shown in FIG. 11 in total is a Wheatstone bridge. This circuit provides a very advantageous way to measure changes in resistances in the strain gauges 26a, 26b, 26c, 26d to obtain information about the strength of the force F exerted onto the pin 17 and information about the direction of the force F exerted onto the pin 17.

[0130] The measurement values obtained at the signal output 48, 49 and 50 of the three direction x, y and z can be processed using appropriate formulas and can be calculated into force information and directional information. From this information about the speed and the direction of speed of the object relative to the fluid can be calculated.

[0131] Appropriate algorithms and formulas can be employed for performing this calculation and for employing the desired information.

[0132] According to FIGS. 6, 9 a further embodiment of the sensor 63 is shown having blades 25a, 25b, 25c, 25d that are of different shape:

[0133] FIG. 6 shows blades 25a, 25b, 25c, 25d that have at their inner ends 28 a width W1 smaller than the width W2 of the blade 25 at its outer end 28.

[0134] According to FIGS. 7, 9 the sensor 63 can comprise an installation housing 35 that permits pre-installation into the object 10, for example into the surfboard 11. The installation housing 35 can comprise a compartment for receiving a sensor housing 69. The sensor housing 69 can also have a compartment 70 for receiving the ring 22 including the spring 62.

[0135] A plate 38b can close the sensor housing 39 and can constitute the cover 23 or can be covered by a further cover not shown in the drawings.

[0136] There is a further plate 38a shown for easy installation as well as fixing members 37a, 37b that facilitate mounting of the sensor.

[0137] Screw receptacles 39a, 39b, 39c, 39d serve for receiving screws (not shown) for mounting the sensor.

[0138] According to the embodiment of FIG. 12 there is 3-blade sensor 54 shown. This sensor consists of three blades 25a, 25b, 25c that are arranged under an angular distance =120.

[0139] On the back side of the blades 25a, 25b, 25c (not shown in FIG. 12) there are in total three strain gauges.

[0140] FIG. 13 discloses another embodiment showing a sensor 63 having a pin 78 that elastic or bendable. The rest position of the pin 78 is shown in solid lines and the bend position of the pin 78 is shown that is reached if a force F is exerted onto the free end 66 of the pin 78 is shown in broken lines.

[0141] Strain gauges 26e, 26f are indicated in FIG. 13 and provided on the outer sides 71 of the pin 78 that are capable of detecting a length change of the pin 78 due to a bending of the pin 78.

[0142] As there are several strain gauges 26e, 26f on the outer side 71 of the pin 78 the sensor 63 of FIG. 13 can also not only measure the velocity but also the direction of travel.

[0143] According to FIG. 1 and FIG. 14 there is also a system 72 provided that comprises not only of the sensor 63 but also a first communication unit 56. The first communication unit 56 can be an integral part of the sensor 63 or can be a separate part on the object 10 and being connected to the sensor 63 either by cable or via wireless connection.

[0144] The first communication unit 56 can interact via a signal path 59a in a wireless manner with a second communication unit 57 on a distant place. The second communication unit 57 can be arranged on land or alternatively on a platform on the sea or on another moving object.

[0145] All measurement information obtained from the electronic circuit 44 can be transmitted via the first communication 56 to the second communication unit 57.

[0146] According to a further embodiment of the invention it is also possible to include GPS data.

[0147] FIG. 14 discloses a system 72 that may also comprise a satellite 58 that is via a signal path 59b, which can be unidirectional, capable of transmitting GPS data to the first communication unit 56. This GPS data can be used or employed or transmitted by the first communication unit 56 to the second communication unit 57.

[0148] The second communication unit 57 can be connected to a calculating unit 60 that can calculate all received data. From the data received by the calculating unit 60 information about the relative movement of the object 10 relative to the fluid 12 in x-, y- and/or z-direction can be obtained.

[0149] For purpose of clarification it shall be noted that the calculator 60 can also be installed at the object 10, and can also be integral part of the sensor 63 or a separate part of the sensor 63.

[0150] While the previous embodiments employin parta float 43, instead of such a float a membrane 61 can be used.

[0151] The membrane 61 can be for example positioned at the free end 66 of the pin 17 (see FIG. 15) or can be positioned within the housing 69.

[0152] The membrane 61 can be used to obtain buoyant information by sensing pressure or by sensing changes in pressure.

[0153] Instead of a membrane 61 any other pressure sensitive sensor or detector can be employed that might generate for the system 72 information about a relative direction of the object 10 relative to the fluid 12 in z-direction.