Abstract:
An anemometer assembly for sensing and transmitting wind speed and wind direction data. The wind sensor measures relative wind direction and wind speed without the use of moving parts and consumes very little power making it suitable for unattended operation. The main wind sensing member is an elongated vertical member that can be used as radio antenna. The data can be transmitted from a remote location and thus relay data to a central collection repository or network location.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Anemometers are primarily used to measure air flow and commonly comprise a rotating element whose angular speed of rotation is correlated with the linear velocity of the air flow. Cup and vane anemometers are by far the most prevalent. The cups typically spread over 120 degree angles, attached at a central hub. The center of the hub translates rotational movement along a vertical axis when the cups respond to air movement in the horizontal plane. The rotational movement relates to the speed of the impinging air currents and thus to wind speed. One of the drawbacks of this type of anemometer is that the inertia of the mechanical mechanism must be overcome. The weather vane device requires a very free gimbal so as to allow the device to point accurately into the wind at very low wind speeds. As a result of its reliance on this mechanical element, the anemometer is not conducive to measuring gusts, and is subject to errors in measurement due to overshoot, oscillations that occur due to change in wind direction, and wind measurement even when the wind is not blowing. 
         [0002]    Still another type, a sonic anemometer uses sound waves to measure wind direction and speed. These are a class of instruments that are typically used by research and other scientific organizations. These systems use the changes in the speed of sound as measure over a finite path. Whilst these instruments overcome the failings of the more prevalent cup and vane they cost considerably more to purchase and maintain. Also, the sonic devices tend to be very power hungry, so although suitable for unattended operation, considerable cost and compensatory mechanisms must be built into the device for continuous remote operation. 
         [0003]    Other force sensing vertical rod type anemometers are known. In one example Shoemaker (U.S. Pat. No. 7,117,735) uses a simple, single pickup wind drag force measurement system. Therefore, although addressing the cost threshold, the accuracy of measurement is modest. Moreover, the device is sensitive to inclinations of the base, and has no built in device as a compensatory mechanism for correcting the inaccuracies that would result. 
         [0004]    Another vertical shaft sensor design, Gerardi (U.S. Pat. No. 5,117,687) uses a sphere attached to a shaft. When the wind force moves the shaft, electromagnetic or optical sensors detect the deflection from the neutral position. The air data sensor uses a relative difference method to measure deflection using four orthogonally placed sensors in addition to two more sensors for complete 3-axis velocity measurements. One drawback to this design is the excessive use of strain gauges contributing to the overall complexity of the design. Moreover, this invention requires a counterweight to function in an inclination independent manner. 
         [0005]    Portable wind sensors typically involve a weather vane structure that points a fan-based anemometer in the direction of the wind to measure wind speed. Other types require the operator to point a fan-based anemometer into the wind. These are generally unsuitable for unattended operation, suffering from inaccuracies in measurement and are generally less sensitive than more expensive designs. 
       SUMMARY OF THE INVENTION 
       [0006]    One embodiment of the present invention is directed to an anemometer assembly that is a combined wind speed and wind direction sensor and radio antenna. A wind sensor measures relative wind speed and wind direction without the use of moving parts and consumes very little power making it suitable for unattended operation. The main wind sensor is an elongated vertical member that can be used as radio antenna datalink. Data generated from the wind sensor can be transmitted from a remote location and relayed to a central collection point or network location. 
         [0007]    The anemometer assembly measures the velocity and direction of wind flowing over a surface of interest and includes a sensor plate, an elongated vertical member, and a plurality of load sensors. The sensor plate is supported by the load sensors placed, in one configuration, at 90 degrees to each other. The elongated vertical member extends perpendicularly from the sensor plate, and has a means of connecting to a surface, preferably from the center of the sensor plate. The sensor plate is preferably made from a variety of rigid but lightweight materials, such, but not limited to, aluminum or composite carbon fiber. 
         [0008]    Opposing load sensors form two legs of a Wheatstone bridge circuit. The load sensors are configured so that wind speed and wind direction is determined by the amount of load difference between opposing load sensors when the elongated vertical member is deflected due to wind loading. The load sensors can be any number of compression sensor gauges as known in the art. 
         [0009]    In accordance with other aspects of the invention, the elongated vertical member is insulated from the base by a bushing to allow the elongated vertical member to be used as a vertical antenna for a transmitter or transceiver for a datalink radio. The elongated vertical member can be made from a variety of materials, for example, but not limited to stainless steel or copper. The elongated vertical member can be telescopic, fixed and detachable, and/or segmented so as to ease transport and portability. 
         [0010]    In accordance with still other aspects of the invention, a tilt sensor is positioned on the sensor plate to measure deviation of the elongated vertical member from true vertical for the installation and compensation of the load sensor measurements. Measurements from the tilt sensor can be used to mathematically compensate and correct for deviations of the anemometer assembly, and by extension the elongated vertical member housed therein, from a true vertical position. As a result, counterpoising mechanisms are not necessary, and the sensor plate does not have to be perfectly level when in operation. 
         [0011]    In accordance with still other aspects of the invention, an antenna lead connects the elongated vertical member to a datalink radio that can link to a remote computer system. The data can be transmitted to a remote location where it can reduce the raw data from the load sensors to calculate wind velocity and wind direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Preferred and alternative examples of the present invention are described in detail below with reference to the following drawings: 
           [0013]      FIG. 1-1  is a schematic top view illustrating the orientation of the sensors of the anemometer assembly of one embodiment of the present invention; 
           [0014]      FIG. 1-2  is a schematic top view of a tilt sensor; 
           [0015]      FIGS. 1-3  and  1 - 4  are schematic drawings of two sets of exemplary strain gauges for X and Y axes configured in Wheatstone bridges; 
           [0016]      FIG. 2  is a cross-sectional and front view of an exemplary embodiment of the present invention; and 
           [0017]      FIG. 3  is a flow diagram of an exemplary embodiment of a wind movement measuring and data transmitting method performed by the system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]      FIG. 1-1  and  FIG. 1-2  shows a schematic top view of an exemplary embodiment of a an anemometer assembly  10  of the present invention, that includes a plurality of opposing load sensors  18  and  19  located on an X-axis  30 , and load sensors  20  and  21  located on an Y-axis  30 , a sensor plate  12 ; a main wind sensor that is an elongated vertical member/antenna  16 ; an insulating bushing  15 , an antenna lead  13 , a tilt sensor  25  ( FIG. 1-2 ), and a datalink radio  17  having a microprocessor  24 . The tilt sensor  25  ( FIG. 1-2 ) is positioned on the sensor plate  12  to detect the angle of inclination of the device and generate correction data. The load sensors  18 - 21  are connect at corners of the sensor plate  20  and a base structure ( FIG. 2 ). The load sensors  18 - 21  are in signal communication with the datalink radio  17 . 
         [0019]    The sensor plate  12  is mounted on top of the plurality of load sensors  18 ,  19 ,  20 ,  21  preferably at 90 degree angles to each other, each load sensor  18 ,  19 ,  20 ,  21  positioned at a corner of the sensor plate  12 , each load sensor  18 ,  19 ,  20 ,  21  is positioned to sense a load in a direction unique from that of the other. Opposing load sensors  18  and  19 , in this example, are along the X axis  30  in relationship to the sensor plate  12 ; and opposing load sensors  20  and  21  are located along a Y axis  35 . Each load sensor  18 ,  19 ,  20 ,  21  makes indirect contact with the elongated vertical member  16  through the sensor plate  12 . Each load sensor  18 ,  19 ,  20 ,  21  detects and measures a load force associated with deflections of the elongated vertical member  16  due to wind impinging on it and transmits any such measured deflection data to the datalink radio  17  where it is processed in microprocessor  24  to determine relative wind direction and wind speed. 
         [0020]    The elongated vertical member  16  is also a radio antenna for transmitting wind data to a data collection point  26 . The wind data calculated by microprocessor  24  is transmitted to the data collection point  26  by antenna  16  using datalink radio  17 . The datalink radio can be any type of radio that is capable of transmitting data, such as a WiMax radio. The elongated vertical member  16  is substantially freestanding and designed to be physically deflected in the direction of any wind flow when placed in such a wind flow stream. The amount of deflection is proportional and directional to the velocity and direction of any such wind flow. The insulating bushing  15 , positioned at an opening in the sensor plate  12 , insulates the elongated vertical member  16  from the sensor plate  12  allowing the elongated vertical member  16  to transmit radio signals without interference. The elongated vertical member  16  is secured to the insulating bushing  15  and the insulated bushing  15  is secured to the sensor plate  12 . The antenna lead  13  connects the elongated vertical member/antenna  16  to the datalink radio  17 . 
         [0021]    The microprocessor  24  converts load sensor  18 - 21  voltage to wind speed in each axis. The wind speed in each axis is corrected for forces due to tilt of the sensor plate  12  by using the tilt signals received from tilt sensor  25 . The corrected wind speed in each axis is then converted to resultant relative wind speed and wind direction by addition of the two wind vectors. The microprocessor  24  then formats the calculated wind speed and wind direction data and sends it to a datalink radio  17  where it is transmitted to a data collection point  26  using antenna  16  ( FIG. 2 ). 
         [0022]    The data collection point  26  ( FIG. 2 ) includes a means to store wind data for later analysis. This could by any common type of computer attached to a suitable datalink receiver. 
         [0023]    The tilt sensor  25  ( FIGS. 1-2 ,  2 ) produces tilt data that is used to correct for variations in inclination of the anemometer assembly  10 , and accurately calibrate the force on the elongated vertical member  16 . For example, a semi-conductor MEMS (micro electronic machined semiconductor) device or electrolytic tilt sensor (e.g. TrueTilt products from the Fredericks Company) can be used to provide for the correction details. The force due to inclination of elongated vertical member  16  from true vertical acts as if the mass of elongated vertical member  16  is located at the midpoint of the element. The force on the sensor plate  12  due to inclination from vertical is equal to the Sine of the angle of inclination from vertical multiplied by the length of elongated vertical member  16  divided by the distance between opposing load cells. To correct for inclination errors, this force is subtracted from the measured force due to wind to determine the true wind induced force on elongated vertical member  16 . 
         [0024]    Turning to back to  FIG. 1-1  and referring to  FIGS. 1-3  and  1 - 4 , opposing load sensors  18  and  19 ,  20  and  21  form two legs of a Wheatstone bridge circuit. In one preferred orientation of the load sensors  18 ,  19 ,  20 ,  21  is at 90 degree angles apart from each other to provide orthogonal force measurements that can be used with vector analysis to determine wind direction. The total force applied to the elongated vertical member  16  can be resolved by vector addition of the individual component forces. 
         [0025]    In  FIG. 1-3 , a first Wheatstone bridge circuit  18 - 19  includes a high side of an input voltage V IN  is connected to a first side of the first load cell  18   −L  and resistor R AX . The low side V IN  is connected to a first side of a second load cell  19   −L  and resistor R BX . A voltage out V OUT  is sampled across a node of the second sides of R AX  and R BX  and a node of the second sides of the load cells  18   −L ,  19   −L . A change in the resistance value of the load cells  18   −L ,  19   −L  correlates to an applied strain. Because the orthogonal wind axis, i.e. axis along which the wind is blowing, can act as a pivot point, the particular load cells used for this application preferably respond to both tensile and compressive forces. 
         [0026]    For example, the standard arrangements as shown in the schematic diagrams  FIGS. 1-3  and  1 - 4 , can have two resistive strain gauges and two fixed or unstrained resistors to measure aerodynamic forces in each in each of the two orthogonal directions εTx is the total strain in along the X axis  30 , and εTy is the total strain along the Y axis  35 . Total strain for each of the two orthogonal directions can be given by the equations: 
         [0000]        εTx=εRAx−εrBx+εR 18 −εR 19   (1) 
         [0000]        εTy=εRAy−εrBy+εR 20 −εR 21   (2) 
         [0027]    Where εTx=total strain in the x direction; 
         [0028]    εTy=total strain in the y direction 
         [0029]    εRAx=total strain on resistor Ax in the x direction 
         [0030]    εRAy=total strain on resistor Ay in the y direction 
         [0031]    εRBx=total strain on resistor Bx in the x direction 
         [0032]    εRBy=total strain on resistor By in the y direction 
         [0033]    εR18=strain on element  18  in the x direction 
         [0034]    εR19=strain on element  19  in the x direction 
         [0035]    εR20=strain on element  20  in the y direction 
         [0036]    εR21=strain on element  21  in the y direction 
         [0037]    Ax, Ay, Bx and By are fixed resistors or unstrained resistance strain gauges. 
         [0038]    Signals generated by the load sensors  18 ,  19 ,  20 ,  21  include, for example, static strain due to the drag of the elongated vertical member  16  and are proportional to the square of the wind velocity. The generated signals from the load sensors  18 ,  19 ,  20 ,  21  are sent to the microprocessor  24 . The microprocessor  24  simultaneously receives the generated signals from at least two load sensors  18 ,  19 ,  20 ,  21 . Inclination of sensor plate  12  from perfectly flat introduces load signal in load sensors  18 ,  19 ,  20 , and  21  that would appear as wind if not corrected for. Inclination of sensor plate  12  is measured by tilt sensor  25 . The tilt data generated by tilt sensor  25  is used by microprocessor  24  to correct the force measurements from load sensors  18 ,  19 ,  20 , and  21  for errors due to inclination of the base plate. The tilt sensor can be calibrated prior to operation if it is not self calibrating. A correction coefficient relating tilt angle to force on the load sensors ( 18 ,  19 ,  20 ,  21 ) is dependent on the height and weight of vertical member  16 . 
         [0039]    In a preferred embodiment rigid material is used for the elongated vertical member  16  providing for simple moment arm calculations (i.e. moment calculated by force multiplied by the lever arm length) to establish the correction factor for tilt. If, for example, the elongated vertical member  16  can bend substantially in the wind because of inherent flexibility, calculation of wind velocity becomes significantly more complex, as the moment arm of the sensor element is no longer a second-order function of wind velocity at high wind speeds. A vector wind speed algorithm, for example as discussed above (See Equations 1 and 2), is carried out by a microprocessor  24  ( FIG. 2 ) to solve the load force equation for velocity in each axis  30 ,  35 , applying the proper calibration coefficients to the drag for (as described in Equation 3) and tilt sensor  25  ( FIGS. 1-2 ,  2 ) data. The microprocessor  24  corrects the load sensor voltage data for tilt and converts the corrected load sensor voltage data to wind speed along each axis. Wind speed in each axis is then converted to resultant wind speed and relative wind direction. The wind direction and wind speed is then formatted by microprocessor  24  and sent to datalink radio  17  for transmission. 
         [0040]      FIG. 2  is a cross-sectional view of an anemometer assembly  10  along an X-axis  30 , showing two opposing load sensors  18 ,  19 , a rigid mounting platform  11 , the sensor plate  12 , and further incorporating some of the features of the present invention. 
         [0041]    The anemometer assembly  10  as described above, measures the wind speed or velocity and wind direction of wind flowing over a surface and includes the sensor plate  12  having a means, such as an opening, for being connected to the elongated vertical member  16 . The sensor plate opening in conjunction with the insulating bushing  15  is a means of securing the elongated vertical member substantially perpendicularly within any such wind flow. The elongated vertical member  16  is connected to and extends perpendicularly through the sensor plate  12 , through the insulating bushing  15 , connecting with the antenna lead  13  and the datalink radio  17 . 
         [0042]    The four load sensors  18 - 21  are mounted on a rigid platform  11 . The rigid platform  11  and the sensor plate  12  are separated by a gap, such that the rigid platform is parallel to and underneath to the sensor plate  12 . The elongated vertical member  16  is secured to the rigid platform and extends substantially perpendicularly from the rigid platform with the elongated vertical member being substantially freestanding and designed to be physically deflected when placed in a wind flow. The antenna lead is substantially protected from wind disturbance by its position within the space between the sensor plate  12  and the rigid platform  11 . 
         [0043]    The elongated vertical member  16  is preferably made of stainless steel or some other suitably rigid, conductive material with a height between approximately 14 inches to 36 inches and a ratio of height to diameter of approximately 30:1 for sensing wind speeds from approximately 10-120 mph. The dimensions of the elongated vertical member  16  are chosen to optimize the range of wind speeds detectable. For example if the elongated vertical member  16  is too long and/or too thin it will not withstand strong winds. On the other hand if the elongated vertical member  16  is too thin and/or too short it will not be responsive to low wind velocities. With these considerations in mind, the elongated vertical member  16  is selected to provide a desirable range of strain values. Preferably an elongated vertical member  16  will be in the range of 0.35-0.75 inches in diameter. 
         [0044]    The force (F) acting on the elongated vertical member  16  is proportional to the square of the wind speed (V); signal generated from the load sensors increases with increased wind velocity. By measuring force (F) while knowing the other parameters (including the dimensions of the elongated vertical member  16 , the velocity is derived by the equation: 
         [0000]        V=[ 2 F/C   d    ρ l d]   1/2    (3) 
         [0045]    where C d  is the drag coefficient of the elongated vertical member; ρ is the density of the fluid (air), l and d are the length and diameter of the elongated vertical member, and V is the free stream velocity of the wind. Because the force due to the wind on the mounted elongated vertical member  16  is measured in two axes (X  30  and Y  35 ), the anemometer assembly  10  measures the vector components of the local wind. Therefore using a rectangular to polar coordinate system conversion, both wind speed and wind direction can be inferred. 
         [0046]    Turning to  FIG. 3  a flow chart illustrates a wind movement measuring and data transmitting method  50  as practiced according to one embodiment of the invention. In operation at a Block  55  a flow of air creates force against the elongated vertical member  16  causing deflection of the elongated vertical member  16 . Next at a Block  60 , opposing load sensors  18 ,  19 ,  20 ,  21  ( FIG. 1-1 ) detect the physical deflection of an elongated vertical member  16  in the direction of any wind flow and generate a signal in response to the deflection. The amount of deflection is proportional and directional to the velocity and direction of any such wind flow. Next at a Block  65 , a signal proportional to the amount of deflection induced strain it generated by the load sensor and is transmitted to and received by a microprocessor  24 : the microprocessor  24  is capable of simultaneously receiving and integrating information input from all load sensors  18 ,  19 ,  20 ,  21  ( FIG. 1-1 ), in addition to signals generated from the tilt sensor  25  at a Block  70 . At a Block  75 , the microprocessor  24  corrects the load sensor data for tilt and calculates the wind speed and relative wind direction. At Block  80 , the wind speed and direction data is formatted and sent to the datalink radio. 
         [0047]    At a Block  85 , the formatted wind speed and wind direction data is transmitted to data collection point  26  which includes a means to store the wind data. The weather sensor data from the elongated vertical member  16  and tilt sensor  25  can then be presented to the end user at the data collection point  26 , which can be, for example, a handheld WiMax® enabled device, which can present the weather data on a display. 
         [0048]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example simple software modifications enable this, allowing for updates to keep this invention useful for the foreseeable future; and a wide variety of materials can be used for the component parts and a variety of load cells and tilt sensors can be used without departing from the spirit of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.