Abstract:
A method of operating an elevator system includes detecting a building sway which causes sway of elevator suspension or compensation members. An elevator control system is switched into a building sway mode, and operation of one or more elevator cars of the elevator system is changed via the building sway mode to mitigate vibratory effects of the building sway on the one or more elevator cars.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to elevator systems. More specifically, the subject matter disclosed herein relates to mitigation of sway of suspension and/or driving ropes for elevator systems. 
         [0002]    Elevator systems typically include one or more ropes or other suspension members from which an elevator car is suspended, and with which the elevator car is driven along a hoistway. Tall buildings in particular, which have elevator systems servicing them, have some sway associated with them. This sway, most often experienced during periods of high winds, can seriously impact elevator performance and, in some instances, damage elevator components. For example, building sway can result in rope sway that, especially when the rope length is shortened as the car runs into an upper or lower landing, has a significant lateral amplitude that causes excessive vertical vibration and noise at the elevator car. Further, rope sway effects experienced at the elevator car are increased at certain floors where the rope sway frequency is at or near the building sway vibratory frequency. 
         [0003]    The typical approach to rope sway mitigation involves deploying mechanical elements such as sway arms, snubbing devices, car followers, rope guides, isolators or the like. The mechanical elements such as the above increase system cost and many times lack the reliability necessary to prevent the effects of rope sway. Another solution includes adjusting a tie down sheave in the hoistway to minimize the effect of compensation rope sway during the high wind event. The building is then monitored for sway and wind modes are implemented limiting elevator performance, for example, stopping service to floors in a predetermined “critical zone”, at which the effects of the building sway on the elevator car are greatest. This approach, however, results in having many unserviceable floors of the building during building sway events, which is unacceptable to many elevator system users. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a method of operating an elevator system includes detecting a building sway which causes sway of elevator suspension or compensation members. An elevator control system is switched into a building sway mode, and operation of one or more elevator cars of the elevator system is changed via the building sway mode to mitigate vibratory effects of the building sway on one or more elevator cars. 
         [0005]    Alternatively in this or other aspects of the invention, changing operation of one or more elevator cars includes stopping an elevator car during travel to reduce a sway amplitude of suspension or compensation members operably connected to the elevator car via the stoppage. Movement of the elevator car is then restarted. 
         [0006]    Alternatively in this or other aspects of the invention, a false call is assigned to the elevator car to stop the elevator car. 
         [0007]    Alternatively in this or other aspects of the invention, the elevator car is given priority for a call at an intermediate floor to stop the elevator car. 
         [0008]    Alternatively in this or other aspects of the invention, changing operation of the one or more elevator cars includes limiting a continuous length of time an elevator car may spend at a floor or number of floors defined as a critical zone with regard to suspension or compensation member sway by configuring individual elevator cars of the elevator system with critical zones at different levels in the building. The controller is utilized to direct passengers to selected elevator cars such that a destination of each passenger is not within the critical zone for the elevator car to which they are assigned, thereby limiting continuous time of the elevator cars in their respective critical zones. 
         [0009]    Alternatively in this or other aspects of the invention, the critical zones are configured by installing different tie down sheaves at each elevator car. 
         [0010]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0012]      FIG. 1  is an illustration of an embodiment of an elevator system; 
           [0013]      FIG. 2  is an illustration of another embodiment of an elevator system having multiple hoistways; 
           [0014]      FIG. 3  is an illustration of yet another embodiment of an elevator system; 
           [0015]      FIG. 4  is an illustration of still another embodiment of an elevator system; and 
           [0016]      FIG. 5  is an illustration of another embodiment of an elevator system having multiple hoistways. 
           [0017]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Shown in  FIG. 1  is an embodiment of an elevator system  10 . Features of the elevator system  10  that are not required for an understanding of the present invention (such as the guide rails, safeties, etc.) are not discussed herein. The elevator system  10  includes an elevator car  12  operatively suspended or supported in a hoistway  14  with one or more suspension members, for example, suspension ropes  16 . The one or more suspension ropes  16  interact with one or more sheaves  18  to be routed around various components of the elevator system  10 . The one or more suspension ropes  16  are also connected to a counterweight  20 , which is used to help balance the elevator system  10  and reduce the difference in rope tension on both sides of the one or more sheaves  18  during operation. The sheaves  18  each have a diameter  22 , which may be the same or different than the diameters of the other sheaves  18  in the elevator system  10 . At least one of the sheaves  18  could be a drive sheave driven by a machine  24 . Movement of the drive sheave by the machine  24  drives, moves and/or propels (through traction) the one or more suspension ropes  16  that are routed around the drive sheave  18  thereby moving the elevator car  12  along the hoistway  14 . The elevator system  10  may further include one or more compensation ropes  26  extending from the elevator car  12  toward a hoistway pit  28  around a compensation sheave  27  and up to the counterweight  20 . A tie-down mass  60  may be disposed in the hoistway pit  28  and affixed to the compensation sheave  27 . The compensation ropes  26 , compensation sheave  27  and tie-down mass  60  stabilize motion of the elevator car  12  along the hoistway  14 . 
         [0019]    As shown in  FIG. 2 , some elevator systems  10  include multiple hoistways  14  and multiple elevator cars  12  controlled via a controller  30 , which may operate in either a destination dispatching mode or in a hall call dispatching mode. In hall call dispatching, the passenger initiates a call by pressing a hall call button  33  located in a hallway  34  outside the hoistway  14 . Typically, the button pressed will indicate a desired direction of travel (either up or down) of the passenger. Once inside the elevator car  12 , the passenger presses a button on a car panel  36  to indicate a destination floor. In destination dispatching, the passenger indicates the destination floor on a destination entry panel  32  in the hallway  34 . The controller  30  decides which elevator car  12  the passenger will travel on and directs the passenger to the correct elevator car  12  by, for example, a message on the destination entry panel  32  or an audible signal. 
         [0020]    Referring now to  FIG. 3 , as the elevator car  12  moves to provide service to various floors  38  of a building  39 , a suspension rope length  40  between the machine  24  and the elevator car  12  shortens as the elevator car  12  moves upwardly in the building  39 . Similarly, a compensation rope length  42  between the elevator car  12  and the hoistway pit  28  shortens as the elevator car  12  moves downwardly in the building  39 . During conditions of building sway, for example, high wind events, the suspension ropes  16  and the compensation ropes  26  will sway laterally at a frequency and amplitude. Quickly shortening suspension ropes  16  or compensation ropes  26  via elevator car  12  travel in the building  39  while the ropes  16  or  26  have significant lateral sway amplitude results in increased rope vibratory frequency that when coupled with vertical motion of the elevator car  12  results in undesirable vertical vibrations and noise in the elevator car  12 . Such conditions are most prevalent when the elevator car  12  is making a long, non-stop run in the building  39 , for example, when the elevator car  12  is conveying a passenger from a high floor  38  in the building  39  to a first floor  38  of the building  39 , with no other calls for the elevator car  12  being made. Conventionally, the elevator car  12  would travel along the hoistway  14  without interruption, resulting in high vibration of the elevator car  12  with the quick shortening of the compensation ropes  26  as the elevator car  12  nears a bottom of the hoistway  14 . It is to be appreciated that similar conditions would exist when the elevator car  12  makes a long uninterrupted run in the upward direction in the building  39  and the suspension ropes  16  are quickly shortened. 
         [0021]    To mitigate this issue, specific logic is utilized by the controller  30  during building sway condition as detected, for example, by a building sway detector  46 . The building sway detector  46  may be a pendulum switch, accelerometer, input from a building tuned mass damper, or a wind anemometer, or other such device. When a building sway is detected, and the elevator car  12  is on a long travel run such as described above, the controller  30  will assign a false call at a floor  38  prior to the elevator car&#39;s destination floor  38 . For example, during travel from a high floor  38  to the lobby floor  38 , the controller  30  may assign a false call to a fifth floor  38 , to briefly stop the elevator car  12 . If the elevator system includes multiple hoistways  14  and multiple elevator cars  12 , the elevator car  12  on the long travel run is assigned priority to accept a request from an intermediate floor  38  to briefly stop the elevator car  12 . 
         [0022]    The brief stop of the elevator car  12 , whether due to the actual intermediate call or the false call allows the rope sway amplitude, either of the suspension ropes  16  or compensation ropes  26 , to lessen before the elevator car  12  returns to motion, thus preventing the high amplitude that results in vibration at the elevator car  12  due to the high speed shortening of the ropes. This solution is beneficial as it is only apparent to a passenger as a false call when a low volume of passengers are utilizing the elevator system  10 . Further, the elevator cars  12  are not slowed for each trip during a building sway event as is the typical solution, so performance of the elevator system  10  is improved, especially during high volume usage of the elevator system  10 . 
         [0023]    In another embodiment, as illustrated in  FIG. 4 , during a building sway event, the building  39  has one or more critical zones  48 , equating to floors  38  or sets of floors  38 . Critical zone landings or floors  38  are vertical stopping locations in the building  39  that set the length of elevator compensation ropes  26  or suspension ropes  16  that result in their resultant natural sway period to be close in magnitude to the building sway periods. At these locations (critical zones) it is very easy to build up large rope sway amplitudes during building sway events. It is to be appreciated that while the description herein is of limiting sway of suspension ropes  16  and compensation ropes  26  at a car  12  side of the elevator  10 , the invention described herein may also be applied to limiting sway of suspension ropes  16  and/or compensation ropes  26  at a counterweight  20  side of the elevator  10 . In this case the concept of critical zones would be extended to include landings that put the counterweight side hoist ropes  16  or compensation ropes  26  at respective lengths  51  or  50  that result in those rope segments being tuned to be similar to the building sway input period. Time that elevator cars  12  spend in the critical zones  48  increases the likelihood of excessive suspension rope  16  or compensation rope  26  vibration during the building sway event. As such, as part of controller  30  operation during such a sway event, either in a destination dispatch or traditional hall call elevator system  10 , the building sway detector  46  triggers the controller  30  to initiate building sway mode. The controller  30  will then limit the number of calls that can be accepted by an individual elevator car  12  for landings in the critical zones  48 . Limiting the number of calls that can be accepted in the critical zones  48  limits the amount of time the particular elevator car  12  spends in the critical zone  48 , thereby limiting rope sway amplitudes. In addition to limiting the number of calls that can be accepted in a critical zone  48 , the controller  30  may choose to adjust the number of stops the elevator car  12  may make in the critical zone  48  depending on how many passengers will be boarding or deboarding the elevator car  12  at a particular floor  38 , because the number of passengers boarding or deboarding determines a necessary transfer time at the floor  38  and therefore affects the amount of time spent in the critical zone  48 . 
         [0024]    Further, the controller  30  may utilize static critical zone  48  determinations input into the controller  30 , or may make dynamic adjustment to the critical zone  48  based on information provided to the controller  30 . For example, weight of the elevator car  12  has an effect on the suspension ropes  16 , so the controller  30  may utilize a dynamic calculation of the critical zone  48  based on a number of passengers in the elevator car  12  and/or a load weight from a load weight cell. In some elevator systems  10 , a weight of an empty elevator car  12  may also be used as part of the calculation of the critical zone  48 . 
         [0025]    In a destination dispatch elevator system  10 , the controller  30  monitors the number of stops assigned to a particular elevator car  12  and then limits the number of stops to a number appropriate to an amount of time that can be spent in the critical zone  48 . For example, if the critical zone  48  of a particular building  39  is defined by floors  10  through  15  in a building  39  of fifteen floors, then the controller  30  can assign any number of passengers to stop at floors  2  through  9 , while only allowing one or two stops in the critical zone  48 , floors  10  through  15 , in any given run of the elevator car  12 . The controller may do this by, for example, allowing only passengers traveling to floor  12 , or one of the other floors in critical zone  48 , into a particular elevator car  12 , while not allowing passengers whose destination is any of the other floors in the critical zone  48  into the same elevator car  12 . Alternatively, the controller  30  may allow passengers bound for any of the floors in the critical zone  48  to enter the same elevator car  12 , but to direct the elevator car  12  to travel out of the critical zone  48  between stops in the critical zone  48  thereby limiting contiguous time spent in the critical zone  48 . 
         [0026]    In a traditional hall call elevator system  10 , the building sway mode may be implemented by limiting the number of elevator car  12  calls accepted by the car panel  36  in the critical zone  48 . For example, in the building  39  with the floor  10  through  15  critical zone  48  above, the controller can effectively lock out the critical zone floor call buttons of the car panel  36  after one or two calls to the critical zone  48  have been registered by the car panel  36 . Suppose a number of passengers enter an elevator car  12  at the first floor of building  39 , the elevator system  10  having building sway mode engaged so that only one stop is permitted in the critical zone  48 . A first passenger depresses the button for floor  12  on the car panel  36 . Any attempts to depress buttons for floors  10 - 11  or  13 - 15  by the other passengers will not be registered by the car panel  36 . The car panel  36  may display a message informing the passengers that it will be necessary to leave the elevator car  12  and board another elevator car  12  to travel to floors  10 - 11  or  13 - 15  due to conditions. The displayed message may be augmented by, or replaced by an audible message. Utilizing this building sway mode operation, the elevator system  10  will still be able to service all floors of the building  39 , while minimizing time elevator cars  12  spend in the critical zone  48  to reduce the effects of rope sway on elevator car  12  performance. 
         [0027]    Referring now to  FIG. 5 , in other embodiments, an amount of tie down mass  60  may be varied between hoistways  14  in elevator systems  10  with multiple hoistways  14 . The effect is that, for example, a critical zone  48   a  for a first hoistway  14   a  having a first tie down mass  60   a  is floors  30 - 40  of a fifty floor building  39 . In a second hoistway  14   b,  a different tie down mass  60   b  is installed, such that a critical zone  48   b  is between floors  40 - 50 . Utilizing a destination dispatch elevator system  10  including the different tie down mass  60   a  and  60   b,  passengers selecting travel to floors  40 - 50  are assigned to elevator car  12   a  in hoistway  14   a  by the controller  30 , while passengers selecting travel to floors  30 - 40  are assigned to elevator car  12   b  in hoistway  14   b.  In a traditional hall call elevator system  10 , the tie down mass variation may be implemented by locking out buttons for floors  30 - 40  on car panel  36   a  of elevator car  12   a,  and locking out buttons for floors  40 - 50  on car panel  36   b  of elevator car  12   b.  Passengers pressing the locked out buttons would be directed by a visual and/or audible message to a proper hoistway for their selected floor. Signage may also be installed above the elevator cars  12  to indicate floors  38  of service. 
         [0028]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.