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CROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY 
     The present invention contains subject matter related to Korean Patent Application No. 10-2014-0027032, filed in the Korean Patent Office on Mar. 7, 2014, the entire contents of which are incorporated herein by reference. Applicants also claim priority from Korean Application No. 10-2014-0027032 filed Mar. 7, 2014. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to method of controlling a power trunk or tailgate, and more particularly, to a method of controlling a power trunk or tailgate with a synchronization procedure between left and right spindles. 
     Description of Related Art 
     In general, a trunk is used to store general luggage, an emergency tool kit, a spare tire, and the like. In some cases, a first-aid kit and the like are stored in the trunk for preparation against an accident. A lid that covers such a trunk room is called a trunk lid. 
     The trunk lid is locked/unlocked by a trunk locking device, which includes a hinge for allowing the trunk lid to be lifted by even a weak force as the locking device is released. 
     Recently, an automatic power trunk system capable of automatically opening or closing the trunk lid by making a simple switch operation on a driver seat has been developed. 
     In the related art, various techniques to control driving of the power trunk have been proposed. 
     By way of example of the related art, there is known a technique in which an angle of the trunk and a movement velocity is transmitted from a Hall sensor, the movement velocity of the trunk is classified into an accelerating cycle, a decelerating cycle, and a constant velocity cycle, and the velocity of the power trunk is controlled by increasing, decreasing, or maintaining a duty ratio at a constant rate for each cycle. In this technique, output power of a motor is controlled by increasing or decreasing the pulse width modulation (PWM) duty ratio at a constant rate so as to control the velocity of the trunk for each cycle. 
     When a vehicle having a power trunk or tailgate stops or is parked on a curved place or a sloping road, the center or gravity of the power trunk or tailgate is decentered, so that a difference is generated between loads applied to spindles of both sides of the power trunk or tailgate. 
     In this manner, when a difference is generated between the loads applied to the spindles of both sides, a difference is also generated between the speeds of both spindle motors. Therefore, a bending load is generated in the trunk or tailgate, and a deviation is disadvantageously generated in the trunk or tailgate. 
     CITATION LIST 
     Patent Literatures 
     [Patent Literature 1] Korean Patent Application Publication No. 10-2010-0059127 
     SUMMARY OF THE INVENTION 
     This invention has been made to address the aforementioned problems and provide a method of controlling a power trunk or tailgate with a synchronization procedure between left and right spindles in order to prevent a speed difference from being generated between spindle motors of both sides in a vehicle having the power trunk or tailgate. 
     The object of the present invention is not limited to those described above, and a person skilled in the art would apparently appreciate other objects by reading the following descriptions. 
     According to an aspect of the invention, there is provided a method of controlling a power trunk or a power tailgate in a power trunk or tailgate control system for controlling operations of the power trunk or the power tailgate in a vehicle having the power trunk or the power tailgate, the method comprising: checking whether the power trunk or the power tailgate has an open operation state or a close operation state; measuring a Hall effect count of a left spindle motor for driving a left spindle and a Hall effect count of a right spindle motor for driving a right spindle used to open or close the power trunk or the power trunk if the power trunk or the power tailgate has the open operation state or the close operation state; stopping operations of the left and right spindle motors and outputting an alarm if an error count is equal to or greater than a predetermined error limitation value as a result of the measurement of the Hall effect count of the left spindle motor and the Hall effect count of the right spindle motor; stopping operations of the left and right spindle motors and outputting an alarm if a difference of the Hall effect count obtained by comparing the Hall effect count of the left spindle motor and the Hall effect count of the right spindle motor is equal to or greater than a first predetermined limitation value; performing a synchronization procedure between the left and right spindles if the difference of the Hall effect count is smaller than the first limitation value and is equal to or greater than a second predetermined limitation value; and maintaining the current output ratio between the left and right spindle motors if the difference of the Hall effect count is smaller than the second limitation value. 
     The Hall effect count of the right spindle motor may be compared by referencing the Hall effect count of the left spindle motor. 
     In the aforementioned method, the performing the synchronization procedure may include increasing the output ratio of the right spindle motor if the power trunk or the power tailgate has the open operation state, and the Hall effect count of the right spindle motor is smaller than the Hall effect count of the left spindle motor, and decreasing the output ratio of the right spindle motor if the Hall effect count of the right spindle motor is greater than the Hall effect count of the left spindle motor. Furthermore, the performing the synchronization procedure may include decreasing the output ratio of the right spindle motor if the power trunk or the power tailgate has the close operation state, and the Hall effect count of the right spindle motor is smaller than the Hall effect count of the left spindle motor, and increasing the output ratio of the right spindle motor if the Hall effect count of the right spindle motor is greater than the Hall effect count of the left spindle motor. 
     In the increasing the output ratio of the right spindle motor, the output ratio of the right spindle motor may increase without exceeding the second limitation value. 
     In the decreasing the output ratio of the right spindle motor, the output ratio of the right spindle motor may decrease without exceeding the second limitation value. 
     The method may further comprise initializing a synchronization value when the close operation of the power trunk or the power tailgate is normally completed. 
     According to this invention, since the synchronization procedure is performed between the left and right spindles in a vehicle having a power trunk or a power tailgate, a speed difference is not generated between both the spindle motors. Therefore, it is possible to drive the power trunk or the power tailgate more stably. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein: 
         FIG. 1  is a block diagram illustrating a configuration of a power trunk or tailgate control system according to an embodiment of the invention; 
         FIGS. 2 and 3  are flow charts illustrating a method of controlling a power trunk or tailgate according to an embodiment of the invention; 
         FIG. 4  is a diagram for describing operations performed when the power tailgate is opened according to an embodiment of the invention; and 
         FIG. 5  is a diagram for describing operations performed when the power tailgate is closed according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Since the present invention may be modified or embodied in various forms, particular embodiments will be described in detail with reference to the accompanying drawings. However, it should be noted that they are not intended to limit the invention, but include all possible all possible modifications, equivalents, and substitutes within the scope and spirit of the present invention. 
     The terminology used herein is only for the purpose of describing particular embodiments and is not intended to limit the invention. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further to be noted that, as used herein, the terms “comprises”, “comprising”, “include”, and “including” indicate the presence of stated features, integers, steps, operations, units, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, units, and/or components, and/or combination thereof. 
     Unless specified otherwise, all terminologies used herein, including technical and scientific terminologies, have the same meaning as those understood generally by a person skilled in art. Terminologies defined in a general dictionary are to be construed as the same meanings as those understood in the context of the related art. Unless specified clearly herein, they are not construed as ideal or excessively formal meanings. 
     It is noted that like reference numerals denote like elements throughout overall drawings. In addition, descriptions of well-known apparatus and methods may be omitted so as to not obscure the description of the representative embodiments, and such methods and apparatus are clearly within the scope and spirit of the present disclosure. 
     The present invention provides a power trunk or tailgate control system for controlling driving operations of a power trunk or tailgate in a vehicle having the power trunk or tailgate. 
       FIG. 1  is a block diagram illustrating a configuration of the power trunk or tailgate control system according to an embodiment of the invention. 
     Referring to  FIG. 1 , the power trunk or tailgate control system according to the present invention comprises a controller  110 , a left spindle motor  120 , a left spindle  130 , a first Hall sensor  140 , a right spindle motor  150 , a right spindle  160 , and a second Hall sensor  170 . 
     The left and right spindles  130  and  160  are positioned in the left and right sides of the power trunk or tailgate to drive the power trunk or tailgate. 
     The left spindle motor  120  drives the left spindle  130  under control of the controller  110 . 
     The right spindle motor  150  drives the right spindle  160  under control of the controller  110 . 
     The first Hall sensor  140  detects a speed of the left spindle motor  120  to generate a Hall effect count. 
     The second Hall sensor  140  detects a speed of the right spindle motor  150  to generate a Hall effect count. 
     The controller  110  receives the Hall effect counts from the first and second Hall sensors  140  and  170  and controls an output ratio between the left and right spindle motors  120  and  150  based on the Hall effect counts. 
     Now, a description will be made in detail for a method of controlling the power trunk or tailgate by controlling the output ratio of the left or right spindle motor  120  or  150  using the controller  110 . 
       FIGS. 2 and 3  are flow charts illustrating a method of controlling the power trunk or tailgate according to an embodiment of the invention. 
     Specifically,  FIGS. 2 and 3  are flow charts illustrating a method of controlling a power trunk or tailgate in a power trunk or tailgate control system for controlling operations of the power trunk or tailgate in a vehicle having a power trunk or a power tailgate. 
     Referring to  FIG. 2 , the power trunk or tailgate control system checks whether the power trunk or tailgate has an open operation state or a close operation state in step S 201 . 
     If the power trunk or tailgate has the open operation state or the close operation state, the power trunk or tailgate control system measures a Hall effect count of the left spindle motor  120  for driving the left spindle  130  and the Hall effect count of the right spindle motor  150  for driving the right spindle  160  used to open or close the power trunk or tailgate in step S 207 . 
     If an error count is equal to or greater than a predetermined error limitation in step S 209  as a result of the measurement of the Hall effect counts of the left and right spindle motors  120  and  150 , the driving of the left and right spindle motors  120  and  150  stops, and an alarm is output in step S 217 . 
     The Hall effect count of the left spindle motor  120  and the Hall effect count of the right spindle motor  150  are compared. If a difference of the Hall effect count between the left and right spindle motors  120  and  150  is equal to or greater than a first predetermined limitation value in step S 211 , the driving of the left and right spindle motors  120  and  150  stops, and an alarm is output in step S 217 . 
     If the difference of the Hall effect count is smaller than the first limitation value and is equal to or greater than a second predetermined limitation value in steps S 211  and S 213 , a synchronization procedure is performed between the left and right spindles  130  and  160  in step S 215 . 
     If the difference of the Hall effect count is smaller than the second limitation value, the current output ratio between the left and right spindle motors  120  and  150  is maintained. 
     If the close operation of the power trunk or tailgate in step S 201  is normally completed in step S 203 , the synchronization value is initialized in step S 205 . 
     Now, a description will be made in detail for a synchronization procedure between the left and right spindles  130  and  160  according to the present invention. 
       FIG. 3  is a flow chart illustrating a synchronization procedure between the left and right spindles according to an embodiment of the invention. 
     In  FIG. 3 , it is assumed that the Hall effect count of the right spindle motor  150  is compared by referencing the Hall effect count of the left spindle motor  120 , and the controller  110  performs the synchronization procedure by increasing or decreasing the output ratio of the right spindle motor  150 . 
     Referring to  FIG. 3 , if the power trunk or tailgate has an open operation state in step S 301 , and the Hall effect count of the right spindle motor  150  is smaller than the Hall effect count of the left spindle motor  120  in step S 305 , the output ratio of the right spindle motor  150  increases in step S 307 . 
     If the Hall effect count of the right spindle motor  150  is greater than the Hall effect count of the left spindle motor  120  in step S 309 , the output ratio of the right spindle motor  150  decreases in step S 311 . 
     In comparison, if the power trunk or tailgate has a close operation state in step S 303 , and the Hall effect count of the right spindle motor  150  is smaller than the Hall effect count of the left spindle motor  120  in step S 313 , the output ratio of the right spindle motor  120  decreases in step S 315 . 
     If the Hall effect count of the right spindle motor  150  is greater than the Hall effect count of the left spindle motor  120  in step S 317 , the output ratio of the right spindle motor  150  increases in step S 319 . 
     In the course of increasing the output ratio of the right spindle motor  150  in steps S 307  and  319 , the output ratio of the right spindle motor  150  preferably increases without exceeding the second limitation value. 
     In the course of decreasing the output ratio of the right spindle motor  150  in steps S 311  and S 315 , the output ratio of the right spindle motor  150  preferably decreases without exceeding the second limitation value. 
       FIG. 4  is a diagram illustrating operations when the power tailgate is opened according to an embodiment of the invention. 
     Referring to  FIG. 4 , the output ratio of the right spindle motor  150  increases if the Hall effect count of the right spindle motor  150  is smaller than the Hall effect count of the left spindle motor  120  when the open operation of the power tailgate  10  is performed. 
       FIG. 5  is a diagram illustrating operations when the power tailgate is closed according to an embodiment of the invention. 
     Referring to  FIG. 5 , the output ratio of the right spindle motor  150  increases if the Hall effect count of the right spindle motor  150  is greater than the Hall effect count of the left spindle motor  120  when the close operation of the power tailgate  10  is performed. 
     Although exemplary embodiments of the present invention have been shown and described hereinbefore, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications and alterations should therefore be seen as within the scope of the present invention.

Summary:
Disclosed is a method of effectively controlling a vehicle power trunk/tailgate in a vehicle power trunk/tailgate control system by performing a synchronization procedure between the left and right spindles in a vehicle having a power trunk/tailgate. Since a speed difference is not generated between the left and right spindle motors, the power trunk/tailgate can be driven more stably.