Abstract:
A system and method for determining functionality and accuracy of a sensor such that monitoring of a sensor is possible without the provision of redundant sensors. Briefly described, one embodiment is an anemometer operable to detect wind speed adjacent to the wind power installation, a calculating unit operable to calculate a calculated wind speed using data from an operating parameter of the wind power installation, and a comparison device operable to compare the detected wind speed with the calculated wind speed to determine the functionality of the anemometer.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to copending nonprovisional utility application entitled, “METHOD FOR MONITORING A SENSOR,” having Ser. No. 10/496,335, filed Nov. 1, 2004, which is the U.S. National Phase of PCT/EP02/12721 filed Nov. 14, 2002, which claims priority to German Application No. DE 101 57 759.1 filed Nov. 27, 2001. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention concerns a method of monitoring a sensor for sensing the flow speed of a medium. The invention further concerns an apparatus for carrying out that method.  
         [0004]     2. Description of the Related Art  
         [0005]     It is already known from JP 11072502 to test the anemometer which is operating defectively in a process or to establish defective operation thereof. In that situation, the signal of the anemometer is evaluated by means of a computer and, with varying wind conditions, the evaluated data are compared and an error signal can be deduced therefrom.  
         [0006]     JP 57-198870 discloses a test device for anemometers, in which anemometers are tested under working conditions. U.S. Pat. No. 4,331,881 discloses how an anemometer can be used in a wind power installation, the signal from the anemometer being used to control the wind power installation.  
         [0007]     Sensors for monitoring flow speeds of media which are capable of flow have long been known. Quantitative flow speed meters are used in many variations, in dealing with liquids. Anemometers for example are used in the most widely varying structural configurations in relation to gaseous media which also include air.  
         [0008]     Those sensors are frequently exposed in situ to environmental conditions which can adversely effect reliable operability thereof. For example, anemometers arranged on wind power installations, depending on the weather, can certainly be subjected to icing. It will be easily appreciated that such an iced-up anemometer can scarcely still ascertain and deliver a correct value for the flow speed of the air. Redundancy does not afford a satisfactory solution here, as the redundantly provided anemometer is naturally also subjected to the icing effect.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     Therefore the object of the present invention is to monitor a sensor such that monitoring of a sensor is possible without the provision of redundant sensors.  
         [0010]     An exemplary embodiment is method by correlating or comparing of the flow speed of the medium, which is given by the sensor, with at least one operating parameter of an installation operated with the medium. In that respect the invention is based on the realization that such an installation is operated not only on the basis of the data from that one sensor, but frequently operation is dependent on a plurality of parameters. In that manner, a given operating state occurs, independently of the sensor to be monitored but in dependence on the respective flow conditions. If now a characteristic operating parameter is correlated or compared with the flow speed specified by the sensor, it is possible to deduce from that correlation an indication as to whether those values are in a plausible relationship with each other, that is to say whether the sensor is operating faultlessly.  
         [0011]     Another exemplary embodiment is further attained by an apparatus having a sensor for detecting the flow speed of a medium, an installation operated with the medium and a correlation device for correlating the flow speed of the medium, which is specified by the sensor, with at least one operating parameter of the installation.  
         [0012]     In a preferred development of the method the data from the sensor are correlated or compared with a plurality of operating parameters in parallel or successive relationship. Parallel correlation of the data increases the reliability of the information provided about the sensor function. On the other hand however, depending on the operating state of the installation, it may be appropriate, according to the respective operating conditions involved, firstly to use a first operating parameter for the correlation procedure, but, with changing operating conditions, to make use of a second or further operating parameters for the correlation procedure in order to arrive at an assessment which is as reliable as possible.  
         [0013]     In a particularly preferred embodiment of the invention the correlation or comparison device is already integrated into the installation and thus can easily detect the operating parameters required for the correlation or comparison procedure and implement a suitable comparison. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0014]     An embodiment of the invention is described in greater detail hereinafter with reference to the drawings in which:  
         [0015]      FIG. 1  shows a wind power installation; and  
         [0016]      FIG. 2  shows characteristic curves of operating parameters of the wind power installation.  
         [0017]      FIG. 3  is a simplified schematic of a hydroelectric plant making use of the invention.  
         [0018]      FIG. 4  is a simplified schematic of an internal combustion engine making use of the invention  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  shows a wind power installation comprising a pylon  10 , a pod  12  arranged on the pylon  10 , with a rotor having rotor blades  14  for driving a generator arranged in the pod, the generator producing electrical power in dependence on the wind speed. Also provided on the pod  12  is an anemometer  16  for detecting the wind speed.  
         [0020]     As, in particular in winter, in cold weather conditions, the anemometer  16  can certainly suffer from icing and thus the wind speed can be incorrectly indicated, the anemometer  16  is monitored by the power produced by the wind power installation, which is dependent on the wind speed, being correlated with the reading from the anemometer  16 . If the generated power of the wind power installation is higher than would be expected according to the wind speed ascertained by the anemometer  16 , it is possible to deduce therefrom that the anemometer is not functioning faultlessly as the generated power could finally not be produced if the wind speed were not sufficient for that to happen.  
         [0021]     That relationship is shown once again in  FIG. 2  by means of characteristic curves. The characteristic curve  20  represents the variation in the power produced by the wind power installation in dependence on the wind speed. The abscissa is therefore identified by ‘V’ for the wind speed and the ordinate by ‘P’ for power. As can be seen from the characteristic curve, the power rises with increasing wind speed until the nominal wind speed is reached at a point marked by  24  on the abscissa. From here on the wind power installation produces the nominal power. Thus, at least for the range from the origin of the curve to that switch-over point  24 , the wind speed can be correlated with the power produced, in order to deduce from that correlation whether the anemometer  16  is functioning properly.  
         [0022]     After the nominal wind speed is reached however the curve  20  no longer provides any usable indication in regard to the correlation with the wind speed specified by the anemometer. Instead of the power characteristic curve however it is now possible to use the blade angle characteristic curve  22 . From the moment of reaching the nominal wind speed and with a wind speed which further increases, more specifically the pitch angle of the rotor blades is altered. That is illustrated in the lower characteristic curve: here the abscissa is once again marked by ‘V’ for the wind speed and the ordinate by ‘a’ for the pitch angle of the rotor blades. It can be seen from the curve that the pitch angle decreases with increasing wind speed. Thus, after the curve goes beyond the switch-over point  24 , it is possible, on the basis of the pitch angle ‘a’ of the rotor blades, to determine whether the anemometer  16  is still specifying the correct wind speed.  
         [0023]     It will be appreciated that, instead of that successive use of a plurality of operating parameters, such use being dependent on the range of operation of the wind power installation, it is also possible for those parameters to be taken into consideration simultaneously. Therefore, as long as the wind speed is below the nominal wind speed, the electric power generated by the installation is used as the operating parameter and at the same time the pitch angle of the rotor blades  14  is investigated. After the curve has gone beyond the switch-over point  24  and thus the nominal wind speed has been exceeded, the pitch angle of the rotor blades  14  is now used and at the same time the power generated by the installation is taken into consideration.  
         [0024]     As shown in  FIG. 3 , it will be appreciated that this method according to the invention and the apparatus can be applied not only in relation to wind power installations. In hydroelectric power stations  30 , the amount of water  32  flowing therethrough can be measured by sensor  34  and correlated with the electrical power generated.  
         [0025]     As shown in  FIG. 4 , these methods and this apparatus can also be used even in internal combustion engines  40 , in order for example to monitor the feed of fuel  42  by senor  44 . Here the quantitative through-flow rate of the fuel  42  can be correlated with the mechanical power produced.  
         [0026]     The power output of the wind power installation and the pitch angle are combined and used to obtain an estimated wind speed. This estimate is thus obtained from the operating parameter of the wind power installation. These are then correlated or compared to the data collected by the sensor, in one example a wind speed as sensed by the anemometer. The accuracy of the data output by the sensor can therefore be checked. This may permit recalibration of the sensor, fixing the sensor, or in some cases, substituting the data from the wind installation as the valid data in place of the data collected by the sensor.  
         [0027]     All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to copending nonprovisional utility application entitled, “METHOD FOR MONITORING A SENSOR,” having Ser. No. 10/496,335, filed Nov. 1, 2004, which is the U.S. National Phase of PCT/EP02/12721 filed Nov. 14, 2002; and German Application No. DE 101 57 759.1 filed Nov. 27, 2001, are incorporated herein by reference, in their entirety.  
         [0028]     From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the embodiments are not limited except as by the appended claims.