Abstract:
A method for controlling car separation in a multi-car elevator system, the method including: initiating, by a controller, a change in a profile of a target elevator car; determining that N elevators cars are affected by the change in the profile of the target elevator car, wherein elevator car N is an elevator car farthest from the target elevator car; calculating for each of the N elevator cars an updated profile; for each of the N elevator cars, beginning with the Nth elevator car and ending with the target elevator car, performing: determining if the updated profile for the elevator car will provide separation between the elevator car and a neighboring elevator car; and when the updated profile for the elevator car will provide separation between the elevator car and the neighboring elevator car, executing an elevator car profile update process for the elevator car.

Description:
TECHNICAL FIELD 
       [0001]    The subject matter disclosed herein relates generally to the field of elevators, and more particularly, to controlling elevator car separation in a multi-car elevator system. 
       BACKGROUND 
       [0002]    Existing elevator systems may employ multiple cars traveling in the same hoistway or lane. Operating multiple cars in a hoistway with sufficient separation between them is a challenge with any multi-car system. Previous strategies have been developed for maintaining separation between two cars in a hoistway under the assumption that the parameters of the motion (velocity, acceleration, jerk) are constant and will not change. 
       BRIEF DESCRIPTION 
       [0003]    According to one embodiment, a method for controlling car separation in a multi-car elevator system comprises initiating, by a controller, a change in a profile of a target elevator car; determining that N elevators cars are affected by the change in the profile of the target elevator car, wherein elevator car N is an elevator car farthest from the target elevator car; calculating for each of the N elevator cars an updated profile; for each of the N elevator cars, beginning with the Nth elevator car and ending with the target elevator car, performing: determining if the updated profile for the elevator car will provide separation between the elevator car and a neighboring elevator car; and when the updated profile for the elevator car will provide separation between the elevator car and the neighboring elevator car, executing an elevator car profile update process for the elevator car. 
         [0004]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the elevator car profile update process comprises: sending, from the controller to a motion controller, a target and a commanded profile for an elevator car; receiving, at the motion controller, the target and the commanded profile, the motion controller determining an initial condition of the elevator car corresponding to a current condition of the elevator car; generating, by the motion controller, a new profile for the elevator car in response to the target, the commanded profile and the initial condition of the elevator car; and sending from the motion controller to the controller an acceptance message indicating acceptance by the motion controller of the target and the commanded profile. 
         [0005]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the elevator car profile update process further comprises: sending, by the motion controller to the controller, the initial condition of the elevator car. 
         [0006]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the elevator car profile update process further comprises: determining, by the controller, an updated profile for the elevator car in response to the initial condition of the elevator car and the commanded profile. 
         [0007]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the commanded profile includes a velocity limit, acceleration limit and jerk limit. 
         [0008]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the initial condition of the elevator car includes position, velocity and acceleration. 
         [0009]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the sending from the controller to the motion controller the target and the commanded profile for the elevator car includes sending a unique command identifier. 
         [0010]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the sending from the motion controller to the controller the acceptance message includes sending the unique command identifier. 
         [0011]    According to another embodiment, an elevator system comprises: an elevator car; a system to impart force to the elevator car in a hoistway; a motion controller operable to command the system to impart force to the elevator car; and a controller in communication with the motion controller, the controller configured to execute operations comprising: initiating a change in a profile of a target elevator car; determining that N elevators cars are affected by the change in the profile of the target elevator car, wherein elevator car N is an elevator car farthest from the target elevator car; calculating for each of the N elevator cars an updated profile; for each of the N elevator cars, beginning with the Nth elevator car and ending with the target elevator car, performing: determining if the updated profile for the elevator car will provide separation between the elevator car and a neighboring elevator car; and when the updated profile for the elevator car will provide separation between the elevator car and the neighboring elevator car, executing an elevator car profile update process for the elevator car. 
         [0012]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the operations further comprise: sending, from the controller to the motion controller, a target and a commanded profile for an elevator car; receiving, at the motion controller, the target and the commanded profile, the motion controller determining an initial condition of the elevator car corresponding to a current condition of the elevator car; generating, by the motion controller, a new profile for the elevator car in response to the target, the commanded profile and the initial condition of the elevator car; and sending from the motion controller to the controller an acceptance message indicating acceptance by the motion controller of the target and the commanded profile. 
         [0013]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein the operations further comprise: sending, by the motion controller to the controller, the initial condition of the elevator car. 
         [0014]    In addition to one or more of the features described above, or as an alternative, further embodiments may wherein the operations further comprise: determining, by the controller, an updated profile for the elevator car in response to the initial condition of the elevator car and the commanded profile. 
         [0015]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the commanded profile includes a velocity limit, acceleration limit and jerk limit. 
         [0016]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the initial condition of the elevator car includes position, velocity and acceleration. 
         [0017]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the sending, from the controller to the motion controller, the target and the commanded profile for the elevator car includes sending a unique command identifier. 
         [0018]    In addition to one or more of the features described above, or as an alternative, further embodiments may include, wherein: the sending from the motion controller to the controller the acceptance message includes sending the unique command identifier. 
         [0019]    In addition to one or more of the features described above, or as an alternative, further embodiments may include, wherein: the system to impart force to the elevator car is a ropeless system. 
         [0020]    In addition to one or more of the features described above, or as an alternative, further embodiments may include wherein: the system to impart force to the elevator car is a roped system. 
         [0021]    Technical effects of embodiments of the disclosure include the ability to dynamically control elevator car separation in a multi-car elevator system. 
         [0022]    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 
         [0023]    The foregoing and other features, and advantages are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0024]      FIG. 1  depicts a multi-car, self-propelled elevator system in an embodiment; 
           [0025]      FIG. 2  depicts a multi-car, roped elevator system in an embodiment; 
           [0026]      FIG. 3  depicts a control system of the elevator system in an embodiment; 
           [0027]      FIG. 4  depicts a process for dynamically controlling a profile of an elevator car in an embodiment; and 
           [0028]      FIG. 5  depicts a process for dynamically controlling elevator car separation in an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Embodiments relate to controlling elevator car separation in a multi-car elevator system. The multi-car elevator system may be ropeless, roped, or other configuration.  FIG. 1  depicts a multi-car, self-propelled (e.g., ropeless) elevator system  10  in an exemplary embodiment. Elevator system  10  includes a hoistway  11  having a plurality of lanes  13 ,  15  and  17 . While three lanes are shown in  FIG. 1 , it is understood that embodiments may be used with multi-car, self-propelled elevator systems have any number of lanes. In each lane  13 ,  15 ,  17 , elevator cars  14  travel in one direction, i.e., up or down. For example, in  FIG. 1  elevator cars  14  in lanes  13  and  15  travel up and elevator cars  14  in lane  17  travel down. In other embodiments, the elevator cars  14  may travel both up and down in each lane  13 ,  15  and  17 . One or more elevator cars  14  may travel in a single lane  13 ,  15 , and  17 . 
         [0030]    Above the top floor is an upper transfer station  30  to impart horizontal motion to the elevator cars  14  to move the elevator cars  14  between lanes  13 ,  15  and  17 . It is understood that the upper transfer station  30  may be located at the top floor, rather than above the top floor. Below the first floor is a lower transfer station  32  to impart horizontal motion to the elevator cars  14  to move the elevator cars  14  between lanes  13 ,  15  and  17 . It is understood that lower transfer station  32  may be located at the first floor, rather than below the first floor. Although not shown in  FIG. 1 , one or more intermediate transfer stations may be used between the first floor and the top floor. Intermediate transfer stations are similar to the upper transfer station  30  and the lower transfer station  32 . 
         [0031]    Elevator cars  14  are propelled using a linear propulsion system having a primary, fixed portion  16  and a secondary, moving portion  18 . The primary portion  16  includes windings or coils mounted at one or both sides of the lanes  13 ,  15  and  17 . The secondary portion  18  includes permanent magnets mounted to one or both sides of the elevator cars  14 . The primary portion  16  is supplied with drive signals to control movement of the elevator cars  14  in their respective lanes. 
         [0032]      FIG. 2  depicts a multi-car, roped elevator system  40  in an exemplary embodiment. Elevator system  40  includes a hoistway  41  having a single lane. Elevator system  40  includes a first elevator car (an upper elevator car)  42 , a first counterweight  43  that corresponds to the first elevator car  42 , a second elevator car (a lower elevator car)  44 , and a second counterweight  45  that corresponds to the second elevator car  44 . The first elevator car  42  is disposed above the second elevator car  44 . 
         [0033]    A first machine  46  that raises and lowers the first elevator car  42  and the first counterweight  43  and a second machine  48  that raises and lowers the second elevator car  44  and the second counterweight  45  are installed in an upper portion of the hoistway  41 . The first and second elevator cars  42  and  44  are raised and lowered inside the hoistway  41  independently from each other by the machines  46  and  48 . A first suspending member  50  is wound around a driving sheave of the first machine  46 . The first elevator car  42  and the first counterweight  43  are suspended inside the hoistway  41  by the first suspending member  50 . A second suspending member  52  is wound around the driving sheave of the second machine  48 . The second elevator car  44  and the second counterweight  45  are suspended inside the hoistway  41  by the second suspending member  52 . 
         [0034]    In operation, elevator cars are controlled so as to dynamically adjust motion profiles of the cars so as to maintain suitable separation between elevator cars.  FIG. 3  depicts a control system  100  of an elevator system in an embodiment. The control system  100  may be used with the ropeless elevator system  10  of  FIG. 1  or the roped elevator system  40  of  FIG. 2 . A controller  58  may serve as a lane supervisor or hoistway supervisor, responsible for controlling the elevator cars traveling in a common path. The controller  58  communicates with motion controllers  60 , which in turn control elevator cars  62 . In the embodiment of  FIG. 1 , a motion controller  60  may control an elevator car  14  or a section of the linear propulsion system. In the embodiment of  FIG. 2 , a motion controller  60  may control machine  46  or  48 . 
         [0035]    The controller  58  can command movement of the elevator car(s)  62  upward or downward in the hoistway, e.g., to a different floor of a building, and the motion controllers  60  implement lower-level (i.e., machine level) control to realize the commanded movement. The one or more motion controllers  60  convert commands from the controller  58  into commands to drive the primary portion  16  in  FIG. 1  or the machines  46 / 48  of  FIG. 2 . 
         [0036]    Each motion controller  60  may be implemented using a microprocessor executing a computer program stored on a storage medium to perform the operations described herein. Alternatively, one or more of the motion controllers  60  may be implemented in hardware (e.g., ASIC, FPGA) or in a combination of hardware/software. Similarly, the controller  58  may be implemented using a microprocessor executing a computer program stored on a storage medium to perform the operations described herein. Alternatively, the controller  58  may be implemented in hardware (e.g., ASIC, FPGA) or in a combination of hardware/software. 
         [0037]    In operation, the controller  58  communicates with one or more motion controllers  60  to control the elevator cars  62 . The control of the motion profile of the elevator cars may be performed dynamically (e.g., in the middle of elevator car runs). Dynamically controlling elevator car profiles may be used to maintain car separation, but also improve user perceived ride conditions such as wait times, travel times, etc. 
         [0038]      FIG. 4  is flowchart of a process for dynamically controlling an elevator car profile in an embodiment. The process may occur at any time controller  58  needs to adjust a profile of one or more elevator cars  62 , and need not be limited to the beginning or end of a run of the elevator car  62 . The profile, or motion profile, identifies operating conditions, such as a velocity/velocity limit, acceleration/acceleration limit and/or jerk limit of an elevator car  62 . An updated profile for the elevator car  62  may be sent by the controller  58  for various control processes, such as next committable floor, separation assurance between elevator cars  62  for normal stopping modes and urgent stopping modes, etc. 
         [0039]    The process begins at  300 , where the controller  58  sends a target and a commanded profile for an elevator car  62  to a motion controller  60 . The target may be a floor (e.g., floor  12 ) or position (e.g., 47.2 meters) for the elevator car  62 . The commanded profile may include profile settings such as a velocity limit, an acceleration limit and a jerk limit. The target and commanded profile may also be accompanied by a unique command identifier. The unique command identifier has a one-to-one correspondence with the target and the commanded profile and is used to identify the target and commanded profile by both the controller  58  and the motion controller  60 . 
         [0040]    At  301 , a determination is made if the motion controller  60  received the message (e.g., target and commanded profile) from the controller  58 . This may occur by the motion controller  60  sending an acknowledgement message to controller  58  along with the unique command identifier. If the motion controller  60  does not receive the message, flow proceeds to  330  where a failure message is generated. 
         [0041]    If at  301  the message from the controller  58  is received at the motion controller  60 , flow proceeds to  302  where, upon receiving the commanded profile, the motion controller  60  determines an initial condition of the elevator car  62  corresponding to a current condition of the elevator car  62 . The initial condition may include current position, velocity and acceleration of the elevator car  62 . The initial condition may be determined based on an existing profile for the elevator car  62 , or measured using sensors. At  304 , the motion controller  60  determines a new profile for the elevator car  62  in response to the target, the commanded profile and the initial condition of the elevator car  62 . The new profile includes the target along with values for velocity, acceleration and jerk. In computing the new profile, the motion controller  60  may factor in changes in the initial condition due to processing delays. For example, the position, velocity and acceleration of the elevator car  62  may change in the time period from first determining the initial condition to computing the new profile 
         [0042]    At  306 , the motion controller  60  determines if the commanded profile can be accepted. There may be situations where the motion controller  60  determines that due to some circumstances (e.g., undue delay at a stop, oversized load on elevator car, etc.) that the commanded profile cannot be achieved. If so, flow proceeds to  308  where the motion controller  60  sends an unacceptance message to the controller  58 , along with the unique command identifier. The process terminates at  332  with a failure. 
         [0043]    If at  306 , the motion controller  60  can accept the commanded profile and target, flow proceeds to  310  where the motion controller  60  sends an acceptance message to the controller  58  along with the unique command identifier. This indicates to the controller  58  that the target and the commanded profile have been accepted by the motion controller  60 . The motion control  60  begins executing the commanded profile. At  312 , the controller  58  determines if the acceptance message has been received from the motion controller  60 . If not, the process ends at  330 . If so, flow proceeds to  314  where the controller  58  determines an expected profile on the elevator car  62  and the process ends at  334  as a successful update of the profile of the elevator car  62 . 
         [0044]      FIG. 5  depicts a process for dynamically controlling elevator car separation in an embodiment. The process may occur at any time controller  58  needs to adjust a profile of one or more elevator cars  62 . The controller  58  begins the process at  410  when it is desirable to modify a profile of a target elevator car  62 . At  412 , the controller  58  determines the number of elevator cars, N (including the target elevator car), that will be affected by the change in profile to the target elevator car. For example, if three elevator cars are traveling upwards in a hoistway and the controller  58  needs to slow the uppermost car, then all 3 elevator cars may be affected by this profile change. At  412 , the controller  58  may assign the elevator cars car identifiers 1 through N, where 1 represents the target elevator car and 2 through N represent one or more other elevator car(s), N being the elevator car farthest from the target car. 
         [0045]    At  414 , the controller  58  calculates the desired profile needed for all N elevator cars in order to affect the change of profile for the target elevator car. The controller  58  then examines each elevator car, one by one, starting with the elevator car, N, farthest from the target elevator car. This is shown at  416 , where a car identifier is set to N. Flow proceeds to  418  where the controller  58  determines, based on the profile for car N, whether there will be sufficient separation between the elevator cars (i.e., car N and its neighboring elevator car(s)). If sufficient separation cannot be assured, flow proceeds to  420  where the process to adjust the profile of the target elevator car is stopped. If at  418 , the controller  58  determines there will be sufficient separation between car N and its neighboring elevator car(s), flow proceeds to  422  where the process of  FIG. 4  is executed. If the motion controller  60  for elevator car N cannot accept the profile ( FIG. 4 , blocks  306  and  308 ), flow proceeds to  424  where the controller  58  makes a record of the failed verification and for future profile changes, the controller  58  assume worst case scenario. If any of the cars fail to completely confirm that the new profile has been accepted, the remaining sequence of profile modifications cannot be continued. This process keeps the elevator cars  62  operating with sufficient separation, but the attempt to modify the profiles of multiple elevator cars  62  must be re-evaluated or re-started (e.g., return to  410 ). 
         [0046]    If the profile of car N is successfully updated at  422 , flow proceeds to  426  where the controller determines if the car identifier is equal to 1 (i.e., the target elevator car has had its profile modified). If not, flow proceeds to  428  where the car identifier is reduced by one and flow proceeds to  418 . If all the elevator cars have had updated profiles at  426 , flow proceeds to  430  where the process is completed. 
         [0047]    Embodiments provide for dynamically adjusting elevator car profiles in a multi-car elevator system. The use of dynamic motion profiles helps prevent situations in which passengers may be stopped in a car for no apparent reason due to obstructions from other elevator cars. An example of this may be to command a trailing elevator car to move at a low speed initially because of an obstruction by a leading elevator car, and increase the speed once the leading elevator car has cleared the following elevator cars intended destination. 
         [0048]    While the disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure 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 disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that aspects of the disclosure may include only some of the described embodiments. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.