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REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present invention claims priority to United Kingdom (GB) patent application number 0207526.5, filed Apr. 2, 2002.  
         TECHNICAL FIELD  
         [0002]    The present invention relates to a control system for a vehicle door latch and more particularly, relates to a closed loop latch control system.  
         BACKGROUND OF THE INVENTION  
         [0003]    Currently known electronic control systems for vehicle door latches provide latch control, but are unable to provide diagnostic fault or malfunction detection. In the present application, the term “malfunction” refers to a specific fault or an anticipated fault with a latch component, such as a non-functioning motor or a seized lever, or a blockage of a latch component due to an incorrect position of another latch component (e.g. if a latch has been instructed to carry out an operation sequence too rapidly for a motor to complete one operation before starting another operation).  
           [0004]    In practical terms, currently known control systems include, for example, a controller that instructs a power actuator to change a particular state of a latch component. If the actuator is unable to change the latch component&#39;s state (e.g., if the actuator is obstructed or has failed) due to an event that is not rectifiable during normal use, the controller currently has no way of notifying the user that the latch component has failed to change state. Instead, the actuator can only repeatedly signal the latch component to carry out the state change even though the latch component is incapable of doing so.  
           [0005]    In other instances, the controller may assume that user intervention, rather than a latch malfunction, is the cause of latch operation failure. For example, a user may try to lock all latches in a vehicle via a power door lock, but one of the latches may fail to lock. The latch control system may then interpret this failure as a request by the user to unlock all of the latches, including the latches that were successfully locked. The vehicle user may be unaware of this fault, resulting in possible compromise of vehicle security or safety, and/or damage of the latch.  
           [0006]    Further, the controller may receive instructions that are outside the operating parameters or physical limitations of the latch component. When the latch component attempts to carry out the instructions from the controller, a malfunction may occur due to, for example, an incorrectly timed sequence of operations being performed within the latch.  
           [0007]    There is a need for a vehicle door latch system that can diagnose faults and detect malfunctions within the system.  
         SUMMARY OF THE INVENTION  
         [0008]    One embodiment of the present invention is directed to a closed loop vehicle door latch control system comprising a controller, a latch including at least one sensor and at least one power actuator. The closed loop structure of the system allows detection of a latch malfunction causing latch failure. Further, the closed loop system can also detect a latch malfunction that causes the latch to fail in carrying out an instruction from the controller. In either case, the system is configured to generate an error signal when the latch malfunction is detected.  
           [0009]    The invention is also directed to a method of controlling a closed loop control system having a controller and a vehicle door latch including at least one sensor and at least one power actuator. In one embodiment, the method includes the steps of: i) interpreting an input from a vehicle user and instructing the latch to perform a predetermined operation on the basis of the instruction; ii) detecting whether the latch has performed the operation or has malfunctioned; iii) generating an error signal if a malfunction has been detected.  
           [0010]    The invention is also directed to a closed loop control system for a vehicle door latch. The closed loop control system comprises a controller, a latch including at least one sensor and at least one power actuator. The system is able to detect when the latch has failed or will fail to carry out an instruction from the controller due to a latch malfunction and is configured to attempt to prevent or overcome the malfunction.  
           [0011]    Yet another aspect of the invention is directed to a method of controlling a closed loop control system having a controller and a vehicle door latch including at least one sensor and at least one power actuator. The method comprises interpreting an input from a vehicle user and instructing the latch to perform a predetermined operation on the basis of the instruction, detecting whether the latch has performed the operation or has malfunctioned, and attempting to overcome the malfunction if a malfunction is detected.  
           [0012]    A further aspect of the present invention is directed to a method of controlling a closed loop control system comprising a controller and a vehicle door latch including at least one sensor and at least one power actuator. The method comprises the steps of interpreting an input from a vehicle user to perform an operation, determining whether the latch is capable of performing the operation or whether carrying out the operation will cause a malfunction, and attempting to prevent the malfunction when instructing the latch to perform the operation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic diagram of a latch incorporating a control system according to one embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is a table illustrating functions of the control system of FIG. 1;  
         [0015]    [0015]FIG. 3 is a diagram illustrating a normal function of the control system of FIG. 1;  
         [0016]    [0016]FIG. 4 is a diagram illustrating the function of the control system of FIG. 1 during a malfunction;  
         [0017]    [0017]FIG. 5 is a further diagram illustrating the function of the control system of FIG. 1;  
         [0018]    [0018]FIG. 6 is a diagram illustrating a normal function of a control system according to another embodiment of the present invention;  
         [0019]    [0019]FIG. 7 is a diagram illustrating a potentially malfunctioning state of the latch of FIG. 1 in the absence of the inventive control system; and  
         [0020]    [0020]FIG. 8 is a diagram illustrating operation of the latch of FIG. 1 with a control system according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0021]    [0021]FIG. 1 is a schematic illustrating a control system  10  for a vehicle door latch  12  according to one embodiment of the invention. In FIG. 1, mechanical connections are illustrated by arrows with solid lines and electrical connections are illustrated by arrows with broken lines. An inside door handle (IDH)  14  fitted to an interior face of a vehicle door (not shown) is operably connected to the inside release lever (IRL)  16  of the latch by a mechanical connection such as a cable or rod. The inside release lever is coupled to an intermediate release lever  25  via a first locking mechanism  18 . In turn, the intermediate release lever  25  is coupled to a pawl  20  arranged to releasably retain a latch bolt in the form of a rotatable claw  22 . The rotatable claw  22  is provided with pawl abutments (not shown) corresponding to a first safety position and a fully latched position of the claw  22  when the abutments are engaged by the pawl  20 .  
         [0022]    To selectively provide a block or break in the transmission path from the inside door handle  14  to the pawl  20  at the first locking mechanism  18  for locking purposes, a power actuator, such as an inside motor  38  is provided. Additionally, the latch  12  may be locked manually by a known locking device, such as a conventional key. A controller  30  in the system provides instructions, such as electrical signals, instructing the motor  26  to change the state of the first locking mechanism  18  between a locked and unlocked state. In one embodiment, the controller  30  is located remotely from the latch  12 . The controller  30  is preferably in the form of a micro-processor and may, in other embodiments, be integrated into the latch  12 .  
         [0023]    An outside door handle  31  mounted on an outer face of the vehicle door is operably connected to an outside release lever  34 , which is in turn operably connected to the pawl  20  through a second locking mechanism  36 . A block or break may be provided in the transmission path by a outside motor  38  through the second locking mechanism  36 , with this block or break representing the mechanism  36  being locked from the outside. In this case, the outside motor  38  is also controlled by the controller  30 .  
         [0024]    In this embodiment, the latch  12  is provided with two sensors. The first sensor is an inside release lever (IRL) switch  24  that signals the controller  30  when the inside door handle  14 , and hence the inside release lever  16 , are being actuated by a vehicle user. The IRL switch  24  also signals the controller  30  when the intermediate release lever  25  is actuated independently of the inside release lever  16 . The second sensor is a door ajar (DA) switch  28 , which is associated with the claw  22  and signals the controller  30  when the claw  22  has been released from its fully latched position. In one embodiment, the door ajar switch  28  is triggered when the claw  22  has rotated to a position approximately halfway between the fully latched and first safety abutments.  
         [0025]    A power release actuator  32  having an actuator motor  33  is also associated with the latch  12 . In this description, the term “power actuator” is intended to cover any form of motor powered by a vehicle power source, such as the vehicle battery, and excludes actuators, such as handles, where the power source is manual energy applied by the vehicle user.  
         [0026]    When the actuator  32  receives the appropriate signal from the controller  30 , the actuator  32  drives the release lever  25  to lift the pawl  20  out of engagement with the claw  22 , thereby releasing the latch  12 . Under normal circumstances, the latch  12  is released by the power release actuator  32 . The mechanical transmission paths from the inside door handle  14  and the outside door handle  31  to the pawl  20  are provided as a back-up release mechanism in case the power to the latch is disconnected due to, for example, an accident or a dead battery.  
         [0027]    [0027]FIG. 2 shows the operation of the latch  12  in response to outputs received from the door ajar switch  28  and the inside release switch  24  according to one embodiment of the invention. As shown in FIG. 2, the logic of the controller  30  can interpret every possible combination of outputs from the door ajar switch  28  and the inside release switch  24  (including output transitions from 0 to 1 and 1 to 0) to correspond to a particular state of the latch  12  and hence the associated door (not shown). Although FIG. 2 and the examples described below focus on components operable by the inside door handle  14 , the inventive concepts are equally applicable to components operable by the outside door handle  31 .  
         [0028]    Where appropriate, the logic of controller  30  may instruct one or more of the first and second motors  26  and  38  and the power release actuator motor  33  to unlock the latch  12  or conduct power release of the latch  12 .  
         [0029]    It can be seen that in this embodiment, the controller  30  logic has been programmed to provide a two-pull override function for the inside door handle  14 . In other words, a first pull of the inside door handle  14  will send a signal from the inside release switch  24  to the controller  30 , which in turn instructs the inside and outside motors  26  and  38  to remove the block or break in the inside and outside locking mechanisms  18  and  36 . When the inside door handle  14  is released, the controller  30  then stores data indicating that the inside door handle has been pulled once.  
         [0030]    If the inside door handle  14  is pulled a second time, the controller  30  determines that the latch  12  should be released and accordingly instructs the power release actuator motor  33  to lift the pawl  20 . If the power release operation fails, the latch  12  may be released via the mechanical linkage from the inside and outside door handles  14 ,  31  to the pawl  20 . This may require a greater force to be exerted by a vehicle user on the inside door handle  14  or outside door handle  31  to release the latch  12 .  
         [0031]    Normal operation of the latch  12  is illustrated by the timing diagram in FIG. 3. The latch  12  starts in a latched and unlocked state. FIG. 3 illustrates the output signal of the door ajar switch  28 , the positions of the intermediate release lever  25  and the inside release lever  16 , the voltage applied to the power release actuator motor  33 , the output signal of the inside release lever switch  24 , and the position of the inside handle  14 . All of the various switches, motors and levers start in a rest position in this example.  
         [0032]    When the inside door handle  14  is pulled, the inside release lever switch  24  emits an output corresponding to the “1” state described in FIG. 2. Because the latch  12  is in an unlocked state at this time, the controller  30  signals the power release actuator motor  33  to act on the pawl  20  to release the claw  22  from the fully latched position. In turn, rotating the claw  22  to a position between the fully latched and first safety positions causes the door ajar switch  28  to signal the controller  30  that the latch  12  has been released. In this embodiment, once the latch release has been detected, the controller  30  signals the power release actuator motor  33  to drive itself back to its normal rest position.  
         [0033]    To close the door, the vehicle user simply pushes the door shut. When the door is closed, the claw  22  engages with a corresponding striker (not shown) on the door surround (not shown), causing the claw  22  to rotate back to its latched position. The door ajar switch  28  then indicates that latch closure has been achieved, as shown in FIG. 3.  
         [0034]    Referring to FIG. 4, the normal latch operation sequence is shown in broken lines and the actual position/state of each component in this example is shown in unbroken lines. As shown in FIG. 4, the intermediate release lever  25  may remain stuck in an actuated state despite the release of the inside door handle  14 . This may occur due to jamming of the inside release lever  16  from rust, ice, or dirt ingress or the like or because a malfunction causes the power release actuator motor  33 , which drives the intermediate release lever  25 , to continue to be powered. Since the intermediate release lever  25  remains actuated in this case, the pawl  20  cannot engage any claw abutment when an attempt is made to latch the latch  12 . This means that although the door ajar switch  28  may indicate a latch closure, actual latching will not have successfully occurred in this condition.  
         [0035]    The “jammed” condition is illustrated by line B in the release motor impact voltage graph in FIG. 4. In this condition, the power release actuator motor  33  is back-driven, causing a jam. The voltage applied to the power release actuator motor  3  is then dropped to zero by a motor overload prevention device (not shown), as shown in FIG. 4. The motor malfunction condition is illustrated by line A in FIG. 4, which shows a continued voltage being applied to the motor  33 . In one embodiment, a dog clutch connection between the intermediate release lever  25  and the inside release levers  16  nevertheless enables the inside release lever to return to its rest position despite the motor malfunction.  
         [0036]    A timer is provided in controller  30 . Once the controller  30  determines that the inside release switch  24  is continuing to generate a high output after a predetermined time period set by the timer, the controller  30  generates an error code that may be sent to a vehicle diagnostic system and/or a dashboard warning light or a buzzer, for example. Alternatively, an error code may be generated as a result of a continued high output from the inside release switch  24  while the door ajar switch  28  is incorrectly indicating that the latch  12  is closed in its fully latched position. Thus, even though a malfunction prevents correct operation of the latch  12  in this case, the inventive system alerts vehicle users to the malfunction, allowing users to take appropriate steps to rectify it due to the closed loop configuration of the invention.  
         [0037]    [0037]FIG. 5 illustrates another embodiment of the inventive control system operation. In this embodiment, the latch  12  is provided with a single pull override unlocking function. In these circumstances, the user pulls the inside handle  14 , triggering activation of the inside release lever  16  and the intermediate release lever  25 . This in turn causes the inside release switch  24  to emit a high output. In this case, the controller  30  is programmed to simultaneously signal the outside lock  36  to unlock and to signal the release motor  33  to lift the pawl  20  from the claw  22 , thereby releasing the latch  12 . As before, once latch release is detected by the door ajar switch  28 , the controller  30  instructs the release motor  33  to back-drive to its rest position. Once the intermediate release lever  25  is back in its rest position, the inside lock  18  is unlocked by the inside motor  38 . By delaying the unlocking until after latch release has occurred, the release process may occur more quickly. Thereafter, the door may be slammed shut as before, returning to a latched but unlocked state.  
         [0038]    [0038]FIG. 6 illustrates another embodiment of the inventive control system operation. This embodiment may complement the control system of the first embodiment described above. In FIG. 6, the latch  12  starts in a locked condition. A first pull of the inside release lever  16  causes the inside release switch  24  to emit a high output. This output is processed by the controller  30 ; as explained above, the logic in the controller  30  dictates that the first pull of the outside door handle  31  and the inside door handle  14  should signal the outside motor  38  and the inside motor  26  to unlock the outside and inside lock mechanisms  36  and  18 , respectively. For unlocking of the inside lock mechanism  36  to occur, the inside release lever  16  must return to its rest position, whereas unlocking of the outside lock mechanism  36  may occur at any time. Thus, both the outside and inside lock mechanisms  36  and  18  change to an unlocked state, with the unlocking of inside unlocking mechanism  18  being slightly delayed.  
         [0039]    There then follows a delay x of greater than a selected time period, such as 50 milliseconds, between the first pull of the inside handle  14  and a second pull (as represented by inside release lever  16 ). This time period x is selected to be sufficient for both the outside and inside motors  38  and  26  to unlock the latch  12 . Because the controller  30  has stored the current state of the outside and inside locks  36  and  18  as being unlocked from the first pull, the second pull of the inside door handle  14  causes the controller  30  to signal the power release actuator  32  to release the claw  22 . A successful release is detected by the door ajar switch  28  as in the previous embodiment. Alternatively, the power unlatching actuator  32  may be omitted from the latch  12  with unlatching occurring via mechanical transmission paths.  
         [0040]    [0040]FIG. 7 illustrates operation of a prior art system that does not contain the inventive control system and where the time delay x between the first and second pulls of the inside handle  14  is less than the selected time period (e.g., 50 milliseconds). In this case, the inside motor  26  is driven to unlock the inside lock mechanism  18  as the second pull of inside door handle  14  occurs. However, because of the construction of the latch mechanism in this example, it is not possible for the inside lock  18  to be unlocked while the inside door handle  14  is being pulled. Thus, the unlocking operation of the inside lock  18  fails and the second pull fails to release the latch, as reflected by a continued low output from the door ajar switch  28 .  
         [0041]    With this type of prior art control system, an additional, third pull on the inside door handle  14  would be required to complete unlocking, with a fourth pull then being required to release the latch  12 . Clearly, this represents an inconvenience to a vehicle user.  
         [0042]    [0042]FIG. 8 illustrates a similar situation as FIG. 7 except that the inventive control system is used to control operation of the latch  12 . Like the example shown in FIG. 7, FIG. 8 shows an operation where the time delay x is less than the selected time period, meaning that unlocking of the inside lock mechanism  18  fails. However, the controller  30  in this case is programmed to expect receipt of an output from the door ajar switch  28  shortly after the second pull (as represented by broken line  40 ). If the controller  30  does not receive this signal, the logic of controller  30  recognizes this as an unlocking malfunction. The controller  30  then signals the inside motor  26  a second time to unlock the inside lock  18  before signalling the power release actuator  32  (not shown in FIG. 8) to release the claw  22 , thereby causing the door ajar switch  28  to emit a high output. Alternatively, in latches not having power release capabilities, the inside handle  14  may be pulled a third time to release the claw  22  manually.  
         [0043]    Because the invention is constructed as a closed loop system that monitors the inside release lever switch  24  and door ajar switch  28 , it is possible to maintain proper functioning of the latch  12  even if a vehicle user provides an input that falls outside of the normal double-pull operating parameters of the latch  12 .  
         [0044]    In another embodiment, the controller  30  determines that an instruction from a vehicle user will cause a malfunction in a latch  12  before instructing the latch  12  to execute the instruction (e.g., because it has stored the time delay an actuator requires to perform a certain function). In this case, the controller  30  is programmed to delay one or more steps in a sequence of instructions to prevent the anticipated malfunction from occurring.  
         [0045]    It will be appreciated by those skilled in the art that the principle of closed loop control may be applied to other latch operating functions. A typical latch  12  may include or be associated with switches in addition to the inside release switch  24  and door ajar switch  28 , such as a lock status indicator switch, central door locking switch, superlock switch, release switch, closure switch interior light (often fitted to the striker or hinge face of the door), child safety switch, as well as two switches per motor that are triggered at the extremes of the motor&#39;s drive. Additionally, latches may be fitted with the additional actuators, such as actuators controlling superlocking, closure and child safety. Any or all of these switches and actuators may be incorporated into and controlled by the inventive control system without departing from the scope of the invention.  
         [0046]    By monitoring the status of these various switches and by providing the appropriate logic within the controller to interpret the latch operation from the switches, the inventive closed loop control system is capable of performing vehicle security functions, vehicle safety functions, latch diagnostic functions, and vehicle comfort functions as well as determining when state changes of various latch components should be conducted by one or more of the actuators described above. The present invention also relates to a method of controlling a latch using a closed loop control system. It should be noted that although the system has been described in relation to the control of a single latch, it may be employed in relation to more than one latch on the same vehicle.  
         [0047]    It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.

Summary:
A vehicle door latch control system detects latch malfunctions via a closed loop system that includes a first switch that is triggered by operation of a door handle and a second switch that indicates whether a latch is in a fully latched position. A controller monitors the operating states of the first and second switches and interprets these operating states to determine door and latch operation as well as detect a latch malfunction.