Abstract:
A method for controlling movement of a window glass ( 12 ) in a vehicle using an electric motor ( 26 ) associated with a drive mechanism ( 1,2,3,4 ) through a cable ( 50 ), said method comprising the steps: determining an actual position (X 2 ) of the window glass ( 12 ) based on the movement of the motor ( 26 ), determining a cable stiffness (S 2 ), determining a position lag ( 400 ) of the window glass ( 12 ) based on the determined actual position (X 2 ) of the window glass ( 12 ), a predetermined position (Z 2 ) of the window glass ( 12 ) and the cable stiffness (S 2 ); and continuously correcting the position of the window glass ( 12 ) based on the determined position lag ( 400 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a method for estimating and adjusting the short drop distance of a vehicle window glass in a frameless glass window system. 
         [0002]    Frameless windows are common in convertible cars. Convertible cars have a canopy which can be moved from an extended position to a retracted position. In the retracted position of the canopy there is no part of the canopy which engages with the top edge of the window. However, in the extended position of the canopy the top edge of the window engages with at least a part of the canopy. In the extended position of the canopy, when the door is opened, the window glass has to be lowered to a position which is slightly below the fully closed position. When the door is shut, the window glass is raised to a fully closed position in which it seals into a seal extending along the canopy of the vehicle above the window. When a door handle is operated to open the door, the window glass is lowered out of the seal in the canopy to enable the door to be opened without interference between the seal and window glass during this process. This lowering of the window while opening the door is commonly referred to as “Short-Drop”. However, the distance for which the glass lowering is required to be such that the “daylight” maximum opening shall not exceed a predetermined limit. For example 4 mm according to US regulation FMVSS118 or maximum opening shall not exceed 12 mm according to Directive 2000/4/EC of the European Parliament. This is required because safety regulations require that if the glass is open for more than the predetermined limit, then during a window close operation, obstacle detection and reversal (commonly called as Anti-Pinch) should be active. However, the Anti Pinch detection cannot be activated unless the motor has attained a certain stable speed. Hence if the glass is lowered just slightly more than the predetermined limit, the chances are that safety regulations would not be met. On the other hand, if the glass is not sufficiently lowered, the seal will get damaged when the door is opened and closed or there will be damage to the glass itself 
         [0003]    Also, these specifications have to be met over the temperature range of −40 to +80 degrees centigrade. Lowering the window by big distances would be an irritant to the user and hence is not a good option. 
         [0004]    The windows are usually operated through an electric motor which is associated with a mechanism for controlling the movement of the window glass. The electric motor is controlled by an Electronic Control Unit (ECU). The ECU usually has a hall sensor to determine the number of rotations of the motor which in turn represents the distance moved by the window glass. The motor is coupled to the glass through mechanical linkages including a cable. The position estimation in power windows is based on the motor rotations measured by the hall sensor. However, it does not accurately represent the glass position because the window glass does not start moving as soon as the motor moves because of the slack in the cable and the other mechanical linkages. When the window glass is lowered or raised for a small distance, the window glass does not move to an exact position due to the cable slack and other mechanical linkages. Hence there will be a position lag of the window glass and there is a need to calculate accurate position of the window glass and correct this position lag. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is advantageous in that it detects a position lag of a window glass and adds this correction to the short drop distance. The invention according to the first embodiment, determines an actual movement of the window glass respective to a movement of the motor and it estimates a position lag of the window glass based on the actual movement of the window, movement of the motor and an ambient temperature; and adds correction to short drop distance based on the position lag of the window. 
         [0006]    According to one of the embodiment the method estimates cable stiffness based on the ambient temperature. As the cable stiffness varies with temperature and lifetime, the position lag of the window glass is estimated accurately. Thus the present invention is advantageous in that it eliminates inaccuracies in the system. 
     
    
     
       BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
         [0007]    Different embodiments of the invention are disclosed in detail in the description and illustrated in the accompanying drawing: 
           [0008]      FIG. 1  illustrates a schematic diagram of a vehicle door system. 
           [0009]      FIG. 2  illustrates the position of the window glass. 
           [0010]      FIG. 3  illustrates a block diagram of the present invention to correct the position lag  400  of the window glass  12  movement. 
           [0011]      FIG. 4  illustrates a method for determining and correcting a position lag of the window glass. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A vehicle door system  100  shown in  FIG. 1  comprises a window glass  12  which can be lowered into a well  14  of a panel member  16  forming the door  100 . For raising and lowering of the window glass  12  there is provided within the panel member  16  a mechanism  1 , 2 , 3 , 4  having a cable  50  fitted onto this mechanism which grips guide rails (not shown) on which the window glass  12  is mounted This mechanism is driven via the cable  50  from an electric motor  26  which is controlled by an electronic control unit (ECU)  60  via signal line  64 . The window glass  12  is held at its front and rear edges  30 ,  32  within the panel member  16  by guide rails (not shown) which are movable with the movement of the motor associated with the cable  50 . The electronic control unit (ECU)  60  has a temperature sensor  70  which provides the value of ambient temperature. The door panel has a door handle  66  which is connected to the electronic control unit  60  via a signal path  62 . 
         [0013]    A canopy  10  shown in  FIG. 1  is electronically controlled and opening and closing operation is controlled by a separate electronic control unit. The canopy  10  has a sealing  20  extending along the length of the canopy of the vehicle in which the window glass  12  can be raised into its closed position when the door is shut. 
         [0014]      FIG. 2  shows the position of the window glass  12 . The window glass  12  can be raised from an upper edge  34  of the panel  16  to a fully closed position X 1  of the sealing  20 . The distance X, Y and Z correspond to the window glass travel from the upper edge  34  of the panel  16  into the sealing  20 . The window glass  12  can be raised into a fully closing position X 1  or a minimum closing position X 2  into the sealing  20  when the door is shut. The window can also be lowered from the sealing  20  below the minimum closing position X 2  when the door is opened. The window is lowered out of the seal  20  to enable the door to be opened without interference between the seal  20  and the window glass  12 . This is commonly referred as “Short-Drop” (SD). If the window glass  12  is not sufficiently lowered, the seal  20  will get damaged when the door is opened or there will be damage to the glass itself. When the door is open, it is expected that the window glass  12  is lowered to a position which is slightly below the minimum closing position X 2 . When the door is shut, it is expected that the window glass  12  is raised to a fully closed position X 1  in which it seals into the sealing  20  to an air tight position or any where between the position X 1  and the position X 2 , for example in the illustration the position Y 1 . When the door is shut or open, the movement of the window glass  12  corresponding to movement of the motor  26  is not exactly same due to some parameters. The parameters are a cable temperature, cable stiffness, a motor speed and a motor voltage or a motor current that is applied to the motor. Due to the aging and also due to the temperature variance, the cable  50  loosens its stiffness and cable tension needs to be adjusted regularly. Hence when the door is shut the window glass  12  would move to a position Z 2  which is still below the minimum closing position X 2  or when the door is opened, the window glass  12  is lowered to a position X 2  instead of position Z 2 . The distance between the position X 2  and the position Z 2  is a position lag  400  which needs to be corrected. The position lag  400  can be of several motor rotations and when translated into glass movement it would correspond to a distance measured in millimeters (mm) of window glass  12  travel. For example if 1 motor rotation corresponds to 1.6 mm of window glass  12  travel, then 7.5 motor rotations would correspond to 12 mm of window glass  12  movement. If this position lag  400  is not estimated and corrected, the window glass  12  would stop movement much earlier. However, the position lag  400  cannot be set at a fixed value and a fixed correction factor cannot be applied due to cable stiffness which varies with temperature. A procedure for correcting this position lag  400  is described in  FIGS. 3 and 4 . 
         [0015]      FIG. 3  illustrates a block diagram  500  of the present invention to correct the position lag  400  of the window glass  12  movement. As shown in the  FIG. 3 , a door operating means B 1 , a motor movement determining means B 2 , a window glass movement determining means B 3 , a cable stiffness determining means B 4 , a position lag estimating means B 5 , window seal position detection means B 6  and a correcting means B 7  are part of a method executed by the ECU  60 . The ECU  60  determines the closing or opening operation of the door  100 . The opening or closing of the door  100  is determined by a door operating means B 1  when the door handle  66  has been operated. When a door operating signal S 4  via the signal path  62  becomes active, the ECU  60  provides a control signal to start the motor  26  to lower or raise the window glass  12  via the signal line  64 . The motor  26  movement determining means B 2  determines the motor speed S 1  based on the voltage S 3  that is applied to the motor  26 . The window glass movement determining means B 3  determines the actual window position in relation to the movement of the motor  26 . The position lag estimating means B 5  uses the door operating signal S 4  to start the window position lag estimation based on a motor speed S 1 , a cable stiffness S 2 , a motor voltage S 3 , actual position of the window glass X 2 , a motor position and a predetermined position of the window glass Z 2 . The cable stiffness S 2  is determined by determining an ambient temperature and the slack due to mechanical linkages from the drive mechanism  1 ,  2 ,  3 ,  4 . The motor position depends on the number of rotations of the motor  26  and is determined from a hall sensor (not shown). The window seal position detection means B 6  is fed with the signals motor speed S 1  and voltage S 3 , which determines the window seal position based on the force that is applied to the window glass  12  and the system damping when the glass enters the seal. The objective of the detection is to determine when the glass is very close to the position where it stops moving. The motor movement beyond this point is only due to the slack in the cable and other non linearities due to mechanical components which vary with temperature and ageing. Based on the motor speed S 1 , cable stiffness S 2  and motor voltage S 3  the position lag estimating means B 5  determines the number of rotations of the motor  26  after which the window glass  12  starts moving after the motor  26  has been activated. It provides the window glass position lag  400  to the correcting means B 7  which uses it for correcting the position lag  400  for which the motor  26  needs to be ON. The position lag  400  relative to the window seal position X 2  is provided by the window seal position detection means B 6 . The correcting means B 7  continuously calculates the remaining position to reach the predetermined position Z 2  at which the motor  26  has to be switched OFF. The motor position has been adjusted based on position of the window glass  12 , the required short drop distance SD, the position lag  400 , the window seal position X 1  and the motor speed dependant on motor voltage S 3 . The correcting means B 7  continuously checks for the position lag  400  that have been corrected to reach the predetermined position Z 2 . If not, the motor  26  movement is adjusted until it reaches the predetermined position Z 2 . Once the predetermined position has been reached, the motor  26  movement is stopped. 
         [0016]      FIG. 4  illustrates a method of the present invention to correct the position lag  400  of the window glass  12  movement. The method is executed in the ECU  60 . In this particular description the position lag correction is described for the door opening operation, but the description also holds good for the door closing operation. In Step S 01 , the ECU  60  determines the closing or opening operation of the door  100 . The opening or closing of the door is determined by the door operating means B 1  when the door handle  66  has been operated. In the next step S 02 , a window seal position is determined. When the door is opened, the window glass  12  is lowered to a position say X 2  due to the parameters cable stiffness S 2 , motor speed  51  and motor voltage S 3  that is applied to the motor  26 . It is expected that the window glass  12  has to be lowered to the position Z 2  in order to avoid other safety features to be activated. In the step S 02 , the ECU determines an actual position X 2  of the window glass  12  with respect to the movement of the motor  26 . The ECU  60  determines movement of the window glass  12  by the window glass movement determining means B 3 . The ECU  66  determines the movement of the motor  26  by the motor movement determining means B 2 . In the step S 03 , the ECU  60  measures an ambient temperature from the temperature sensor  70  and calculates the cable stiffness S 2  by the cable stiffness determining means B 4 . The cable stiffness S 2  is depends on the ambient temperature and is determined from the measured ambient temperature. In the step S 04 , a position lag estimating means b 5  estimates the position lag  400  of the window glass based on the actual position X 2  of the window glass  12  in relation to the movement of the motor  26 , the cable stiffness S 2  and the predetermined position Z 2  of the window glass  12 . In the step S 05 , Based on the ambient temperature and the position lag  400 , the motor movement is initiated to correct the position lag  400  by a correcting means B 7 . In the step S 06 , the correcting means B 7  continuously checks for the predetermined position Z 2  that have been reached. If not, motor movement is adjusted until it reaches the predetermined position Z 2 . Once the predetermined position Z 2  has been reached, at step SO 7  motor movement is stopped. 
         [0017]    Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.