Abstract:
A snow groomer, equipped with a winch assembly to aid handling of the snow groomer on steep slopes, has a frame; a user interface; a control unit; and the winch assembly, which has a support structure fixed or connected to the frame, a drum that rotates with respect to the support structure about an axis, a cable fixed or connected at one end to the drum and wound about the drum, an actuator assembly for rotating the drum about the axis, and a sensor for determining the position of the drum about the axis; the control unit being configured to control the cable as a function of the position of the drum and the geometry of the drum.

Description:
PRIORITY CLAIM 
       [0001]    This application is a national stage application of PCT/EP2010/058140, filed on Jun. 10, 2010, which claims the benefit of and priority to Italian Patent Application No. M12009A 001028, filed on Jun. 10, 2009, the entire contents of each are incorporated by reference herein. 
       BACKGROUND 
       [0002]    Certain known wind power electricity generating systems comprise a hub; a number of blades fitted to the hub; and an electric machine comprising a stator and a rotor. 
         [0003]    In actual use, the wind blows on the blades of these known wind power electricity generating systems to rotate the hub about the axis, and to transfer the kinetic energy of the wind to the hub; and rotation of the hub is transferred to the electric machine, in particular to the rotor which is connected to and rotates with the hub about the axis. 
         [0004]    The hub, blades, and rotor define the rotary assembly. 
         [0005]    In these known wind power electricity generating systems, the angular speed of the rotary assembly must be detected to control the wind power system. More specifically, the angular speed of the rotor must be detected to control an inverter coupled to the electric machine, and/or to control the pitch of the blades with respect to the wind, and/or to calculate the power coefficient of the system, and/or to monitor system operation and efficiency, and/or to keep within a maximum angular speed. 
         [0006]    The angular speed detection device most commonly employed in known wind power systems is an encoder, of which there are various types. The most commonly used are incremental and absolute encoders, which comprise a photodetector or proximity sensor. 
         [0007]    Incremental and absolute encoders comprise a disk, the lateral face of which has at least one succession of holes arranged in at least one circle; and a device for detecting the holes. The disk is fixed to the rotary assembly, and the hole detecting device is fixed to the nacelle. 
         [0008]    An incremental encoder disk has at least one succession of equally spaced holes, and the hole detecting device comprises at least one proximity sensor alongside the disk, or at least one light source and at least one photodetector on either side of the disk. 
         [0009]    As the disk rotates, the hole detecting device detects the holes and generates a signal indicating the angular distance travelled and the angular speed of the disk, and therefore of the rotary assembly. 
         [0010]    Some incremental encoders have at least two proximity sensors or at least two photodetectors, and holes arranged in at least two circles, and detect the rotation direction of the disk. 
         [0011]    In known absolute encoders, on the other hand, the holes are arranged unevenly in a given configuration in at least two circles, and the hole detecting device comprises at least two photodetectors or at least two proximity sensors. Absolute encoders process the signals from the proximity sensors or photodetectors to determine angular position with respect to a fixed reference. 
         [0012]    One problem of using known encoders in direct-transmission wind power systems lies in the encoder requiring a large disk fixed to the rotary assembly. 
         [0013]    In some known direct-transmission wind power systems, the rotor and hub are hollow, are connected directly to each other, and have inside diameters allowing access by workers to the inside for maintenance or inspection. In such cases, using an encoder calls for a disk fixed to the rotary assembly and large enough to permit easy access, which poses two problems: the weight of the disk itself, and the precision with which the holes are formed, which affects the accuracy with which angular speed is determined. Moreover, encoders are sensitive to vibration caused by the blades; and the holes are subject to clogging by dirt, thus impairing reliability of the hole detecting device. 
         [0014]    In order to overcome this drawback, U.S. Published Patent Application No. 2009/047130 discloses an accelerometer combined with a gyroscope both mounted of the hub for retrieving the angular speed and the angular position, PCT Patent Application No. WO 2009/001310 discloses three accelerometer mounted of the hub for retrieving the angular position of the rotor assembly, and German Patent No. 10 2007 030268 discloses an accelerometer mounted on the blade for retrieving the dynamic parameters. However, the above disclosed techniques fail to be highly accurate. 
       SUMMARY 
       [0015]    The present disclosure relates to a wind power electricity generating system and relative control method. 
         [0016]    More specifically, one embodiment of the present disclosure relates to a wind power electricity generating system comprising a nacelle; a rotary assembly rotating about an axis with respect to the nacelle; and an angular speed detection device for detecting the angular speed of the rotary assembly. 
         [0017]    It is an advantage of the present disclosure to provide a wind power system equipped with an angular speed detection device configured to eliminate certain of the drawbacks of certain of the known art. 
         [0018]    According to one embodiment of the present disclosure, there is provided a wind power electricity generating system comprising a nacelle; a rotary assembly rotating about an axis with respect to the nacelle; 
         [0019]    an electric machine comprising a stator and a rotor and an angular speed detection device for detecting the angular speed of the rotary assembly; the angular speed detection device comprising at least one sensor rotating about the axis together with the rotary assembly, and supplies at least one signal related to angular speed; wherein the rotary assembly comprises a hub; at least one blade fitted to the hub; and the rotor of the electric machine, connected to the hub; and the wind power electricity generating system characterized in that the sensor is fixed to the rotor of the electric machine. 
         [0020]    In one embodiment, the rotary assembly comprises a hub; at least one blade fitted to the hub; and a rotor connected to the hub. 
         [0021]    In another embodiment, the sensor is fixed to the rotor. 
         [0022]    It is a further advantage of the present disclosure to provide a method of controlling a wind power system, configured to eliminate certain of the drawbacks of certain of the known art. 
         [0023]    According to one embodiment of the present disclosure, there is provided a method of controlling a wind power electricity generating system; the wind power system comprising a nacelle, a rotary assembly rotating about an axis with respect to the nacelle, an electric machine comprising a stator and a rotor; the method comprising the step of acquiring a signal, related to the angular speed of the rotary assembly; the method being characterized by acquiring the signal of at least one sensor fixed to the rotor of the electric machine rotating about the axis together with the rotary assembly. 
         [0024]    Additional features and advantages are described in, and will be apparent from, the following Detailed Description and the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    A non-limiting embodiment of the present disclosure will be described by way of example with reference to the accompanying drawings, in which: 
           [0026]      FIG. 1  shows a partly sectioned side view, with parts removed for clarity, of a wind power electricity generating system in accordance with one embodiment of the present disclosure; 
           [0027]      FIG. 2  shows a larger-scale, partly sectioned side view, with parts removed for clarity, of a detail of  FIG. 1 ; 
           [0028]      FIG. 3  shows a partly sectioned, schematic view in perspective, with parts removed for clarity, of a detail of  FIG. 1 ; and 
           [0029]      FIG. 4  shows a larger-scale, partly sectioned side view, with parts removed for clarity, of a further embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Referring now to the example embodiments of the present disclosure illustrated in  FIGS. 1 to 4 , number  1  in  FIG. 1  indicates a wind power electricity generating system. 
         [0031]    In the example shown, system  1  is a variable-angular-speed, direct-transmission wind power system. 
         [0032]    Wind power system  1  comprises a pylori  2 , a nacelle  3 , a hub  4 , three blades  5 , an electric machine  6 , an angular speed detection device  7  ( FIG. 2 ), and a control device  8  ( FIG. 2 ). 
         [0033]    The three blades  5  are fitted to hub  4 , which in turn is fitted to nacelle  3 , in turn fitted to pylori  2 . 
         [0034]    Nacelle  3  is mounted to rotate about an axis A 1  with respect to pylori  2  to position blades  5  facing the wind; hub  4  is mounted to rotate about an axis A 2  with respect to nacelle  3 ; and each blade  5  is mounted to rotate about a respective axis A 3  with respect to hub  4 . 
         [0035]    In the  FIG. 1  example, axis A 2  is tilted slightly with respect to the horizontal, and axis A 3  is substantially perpendicular to and radial with respect to axis A 2 . 
         [0036]    With reference to  FIG. 2 , hub  4  comprises a hollow shaft  9  and a body  10 , which are connected rigidly to each other and have inside diameters large enough to permit worker access to the inside for maintenance or inspection. 
         [0037]    Hollow shaft  9  is fitted, on bearings  11 , to nacelle  3  and connected directly to electric machine  6 . 
         [0038]    Electric machine  6  comprises a stator  12  and a rotor  13 . Stator  12  defines a portion of nacelle  3  and comprises stator windings  14 ; and rotor  13  is hollow, comprises permanent magnets  15 , and is fixed directly to hollow shaft  9 . 
         [0039]    In the example shown, electric machine  6  is synchronous. 
         [0040]    The wind rotates hub  4  about axis A 2 ; rotation of hub  4  is transferred to and rotates rotor  13  about axis A 2 ; and the relative movement of permanent magnets  15  with respect to stator windings  14 —in the form of rotation of rotor  13  at variable angular speed—induces voltage at the terminals of stator windings  14 . 
         [0041]    Hub  4 , blades  5 , and rotor  13  are integral with one another, and define a rotary assembly  16  rotating about axis A 2  with respect to nacelle  3 . 
         [0042]    With reference to  FIG. 1 , the pitch of each blade  5  with respect to the wind is controlled by rotating blade  5  about respective axis A 3  to adjust the surface of incidence with respect to the wind. Rotation of each blade  5  about respective axis A 3  is controlled on the basis of efficiency parameters of wind power system  1 , and so as to keep rotary assembly  16  within a maximum angular speed. 
         [0043]    Angular speed is detected by angular speed detection device  7  ( FIG. 2 ). 
         [0044]    With reference to  FIG. 3 , angular speed detection device  7  comprises two sensors  18 , each comprising a transmitter  19 ; two receivers  20 , each coupled to respective transmitter  19 ; and a processing unit  21  coupled to receivers  20 . 
         [0045]    More specifically, each sensor  18  is an accelerometer, and supplies a signal related to angular speed. 
         [0046]    Each sensor  18  determines the acceleration caused by gravitational force and/or centrifugal force along a respective detection axis A 4  integral with respective sensor  18 . 
         [0047]    Each sensor  18  is fixed to rotor  13  (as shown by the continuous lines in  FIGS. 2 and 3 ). In  FIG. 3 , sensors  18  are positioned that respective detection axes A 4  are perpendicular to each other and radial with respect to axis A 2 . Each detection axis A 4 , however, may be set to any position, except that in which it is parallel to axis A 2  or aligned with the other detection axis A 4 . 
         [0048]    In actual use, as rotor  13  rotates about axis A 2 , the force of gravity measured by each sensor  18  along respective detection axis A 4  varies due the change in direction of respective detection axis A 4  with respect to the ground, and each sensor  18  also detects along respective detection axis A 4  acceleration caused by the centrifugal force produced by rotation of rotor  13 . 
         [0049]    When rotor  13  rotates at angular speed, therefore, each sensor  18  emits a signal that, allowing for tolerances and variations in angular speed, is practically sinusoidal; and, given that respective detection axes A 4  of sensors  18  are perpendicular, the respective signals are phase shifted 90 degrees. 
         [0050]    With reference to  FIG. 2 , receivers  20  and processing unit  21  are housed inside nacelle  3 , close to sensors  18 , and integral with nacelle  3 . 
         [0051]    Each signal is received by respective receiver  20  which transmits it to processing unit  21 . 
         [0052]    Alternatively, instead of transmitters  19  and receivers  20 , angular speed detection device  7  comprises contact members  22  which provide sliding contacts; each sensor  18  is coupled by contact members  22  to processing unit  21 ; and the signal from each sensor  18  is supplied to processing unit  21  via contact members  22 . 
         [0053]    Processing unit  21  processes one or both of the signals from sensors  18  to determine the angular speed of rotary assembly  16 . 
         [0054]    Processing unit  21  also processes one or both of the signals from sensors  18  to determine the angular position of rotary assembly  16 . 
         [0055]    With reference to  FIG. 2 , angular speed detection device  7  is coupled to control device  8 . 
         [0056]    Control device  8  controls wind power system  1  on the basis of the angular speed and/or angular position of rotary assembly  16  supplied by angular speed detection device  7 . The control functions performed by control device  8  include: monitoring correct operation of wind power system  1 ; controlling the pitch of blades  5  with respect to the wind; controlling the power coefficient of wind power system  1 ; controlling the inverter coupled to electric machine  6 ; controlling the efficiency of wind power system  1 ; and keeping rotary assembly  16  within the maximum angular speed. 
         [0057]    Control device  8  also processes the angular speed and/or angular position of rotary assembly  16  by fast Fourier transform (FFT) to determine events. 
         [0058]    In one embodiment, additional communication means (not shown in the drawings) are associated with control device  8  of wind power system  1  to transmit the angular speed and/or angular position of rotary assembly  16  to a remote control centre (not shown in the drawings) coupled by cable or radio to wind power system  1 . 
         [0059]    In one variation of the present disclosure, as opposed to being fixed to rotor  13 , each sensor  18  is fixed to hub  4 , and more specifically to an inner wall of body  10  (as shown by the dash lines on the left of  FIG. 2 ). 
         [0060]    In another variation of the present disclosure (not shown in the drawings), as opposed to being fixed to rotor  13 , each sensor  18  is fixed to any one of the three blades  5 , and more specifically to an inner wall of blade  5 . 
         [0061]    In another variation of the present disclosure, each sensor  18  is an inclinometer that supplies a signal related to angular speed; and processing unit  21  calculates angular speed by processing the signal from each inclinometer. 
         [0062]    In another variation of the present disclosure, angular speed detection device  7  comprises only one sensor  18  fixed to rotor  13  or hub  4 ; sensor  18  supplies a signal related to angular speed; and processing unit  21  calculates angular speed on the basis of the signal from sensor  18 . 
         [0063]    In another variation of the present disclosure, angular speed detection device  7  comprises only one sensor  18  in the form of a two-axis accelerometer or a two-axis inclinometer. 
         [0064]    In a further embodiment of the present disclosure shown in  FIG. 4 , in which parts similar to those of the first embodiment are indicated using the same reference numbers as in  FIGS. 1 to 3 , angular speed detection device  7  is replaced with an angular speed detection device  23 . 
         [0065]    Angular speed detection device  23  comprises a sensor  24  defined by a gyroscope based on detection of Coriolis forces; and contact members  25 . 
         [0066]    Sensor  24  is fixed to rotary assembly  16 , and more specifically to rotor  13  (as shown by the continuous line in  FIG. 4 ); or is fixed to hub  4 , and more specifically to an inner wall of body  10  (as shown by the dash line on the left in  FIG. 4 ). 
         [0067]    Angular speed detection device  23  is coupled to control device  8  of wind power system  1  by contact members  25  to supply control device  8  with the angular speed of rotary assembly  16 . 
         [0068]    Sensor  24  is a gyroscope and supplies a signal related to angular speed. More specifically, the signal is a voltage proportional to the angular speed of rotary assembly  16 . 
         [0069]    Sensor  24  is coupled to control device  8  by contact members  25 , which provide sliding contacts by which the signal from sensor  24  is supplied to control device  8 . Alternatively, instead of contact members  25 , the sensor comprises a transmitter  26 ; angular speed detection device  23  comprises a receiver  27  coupled to control device  8  and for receiving signals from transmitter  26 ; and sensor  24  transmits signals to control device  8  by means of transmitter  26  and receiver  27 . 
         [0070]    In a variation of the present disclosure, sensor  24  is fixed to the inside of body  10  (as shown by the dash line in  FIG. 4 ). 
         [0071]    In another variation of the present disclosure (not shown in the drawings), sensor  24  is fixed to any one of the three blades  5 , and more specifically to an inner wall of blade  5 . 
         [0072]    Though specific reference is made herein to a synchronous electric machine, the electric machine may be of any other known type, e.g. asynchronous. 
         [0073]    Clearly, changes may be made to the system and method as described herein without, however, departing from the scope of the accompanying claims. That is, it should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.