Abstract:
A method for configuring a controller to operate a motor to position a seat, in which the controller includes an integrated current sensor and the seat includes a latch operatively coupled to the motor, includes determining an operating profile of the motor under one or more operating conditions, wherein the operating profile represents motor current values during activation of the latch, and wherein the activation of the latch includes at least one latch pulling condition and one latch release condition. The method further includes analyzing the operating profile in order to correlate the profile to the position of the latch. The method also includes loading the controller with instructions to enable comparison of a real-time current measured by the integrated current sensor to the stored operating profile, wherein the analysis enables determination of the latch condition in real-time.

Description:
BACKGROUND 
       [0001]    The present invention relates to a remote release actuating system for retracting and releasing a cable. 
         [0002]    Many conventional actuating systems, such as those for seat adjustment, use an external position sensor (e.g. an encoder, resolvers, hall-effect sensors, potentiometers, etc.) to provide positional feedback to a controller. While operationally sufficient for this purpose, external position sensors add additional cost and weight to the system and are often susceptible to failure. 
       SUMMARY 
       [0003]    In one embodiment, the invention provides a method for configuring a controller to operate a motor to position a seat, the controller including an integrated current sensor, the seat including a latch operatively coupled to the motor. The method includes determining an operating profile of the motor under one or more operating conditions, wherein the operating profile represents motor current values during activation of the latch, and wherein the activation of the latch includes at least one latch pulling condition and one latch release condition. The method further includes analyzing the operating profile in order to correlate the profile to the position of the latch. The method also includes loading the controller with instructions to enable comparison of a real-time current measured by the integrated current sensor to the stored operating profile, wherein the analysis enables determination of the latch condition in real-time. 
         [0004]    In another embodiment, the invention provides a method for controlling the operation of a motor to position a seat. The seat includes a latch operatively coupled to the motor. The motor includes a controller with an integrated current sensor and a pre-determined operating profile of the motor during operation of the latch. The method includes initiating operation of the motor and obtaining real-time motor current values from the current sensor. The method includes comparing the motor current values to the pre-determined operating profile. The method also includes determining if the latch has released and, based on the determination, ceasing or continuing operation of the motor. 
         [0005]    In another embodiment, the invention provides a remote release actuating system for releasing a vehicle seat latch. The seat latch is coupled to a cable including at least one latch pulling condition and one latch release condition. The system includes a gear assembly including a gear case containing a transmission. The gear assembly is coupled to the cable. A biasing member is configured to bias the cable in a first position. A motor has an output shaft operatively coupled to the gear assembly. The motor further includes a power supply with a solid state switch and an integrated current sensor to provide a measurement of the current flowing to the motor. A controller has memory loaded with an operating profile of the motor and is configured to compare the current obtained from the current sensor to the operating profile and determine the state of the latch without the use of a position sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a remote release actuating system. 
           [0007]      FIG. 2  is a perspective view of the motor assembly of the remote release actuating system of  FIG. 1 . 
           [0008]      FIG. 3  is another perspective view of the motor assembly of  FIG. 2 . 
           [0009]      FIG. 4  is a partial perspective view of the remote release actuating system of  FIG. 1  with select transmission components removed. 
           [0010]      FIG. 5  is a partial perspective view of the remote release actuating system of  FIG. 1  with the spool removed. 
           [0011]      FIG. 6  is a partial perspective view of the remote release actuating system of  FIG. 1  with the gear case cover removed. 
           [0012]      FIG. 7  is another partial perspective view of the remote release actuating system of  FIG. 1 . 
           [0013]      FIG. 8  is a schematic view of portions of the remote release actuating system circuit assembly. 
           [0014]      FIG. 9  is a plot of an electrical current operating profile of a motor without the remote release actuating system of  FIG. 1 . 
           [0015]      FIG. 10  is a plot of an electrical current operating profile of a motor with the remote release actuating system of  FIG. 1 . 
           [0016]      FIG. 11  is a flow chart of process steps embodying the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0018]      FIG. 1  illustrates a position-sensorless remote release actuating system  10  including a motor assembly  14 , a gear assembly  18 , and a biasing assembly  22  referenced with respect to a proximal end  26  and a distal end  30  of the system  10 . The system  10  will be described herein for implementation with a vehicle, but is not so limited in its application. 
         [0019]    Referring to  FIGS. 2 and 3 , the motor assembly  14  includes a motor  34  with an output shaft  38  and a worm gear  42  secured thereto for co-rotation. The motor assembly  14  further includes a circuit assembly  46 , the details of which will be further described below, with a circuit casing  50  at least partially covering the circuit assembly  46  to provide protection from the external environment. An electrical terminal  54  receives electrical power for operation of the motor assembly  14 , the source of which can be, for example, derived directly from the vehicle such as through the vehicle&#39;s power circuit. 
         [0020]    Referring to  FIGS. 4-6 , the gear assembly  18  is coupled to the motor assembly for transferring motive force from the output shaft  38 . As shown in  FIG. 4 , a gear case  58  of the gear assembly  18  contains a sun gear  62  integrally formed with an input gear  66 , which is configured to engage the worm gear  42 . Referring to  FIG. 5 , the sun gear  62 , together with planet gears  70  and a ring gear  74 , forms a planetary gear transmission  78 . A driving surface  82  positioned on the ring gear  74  rotates when the worm gear  42  drives the transmission  78 . The driving surface  82  engages and rotates a spool  86  mounted substantially coaxially with the sun gear  62 , as shown in  FIG. 6 . Referring also to  FIG. 7 , the spool  86  secures a proximal end  90  of a cable  94 , which is thereby wound and unwound about the spool  86  during operation. 
         [0021]    Referring again to  FIG. 1 , a distal end  98  of the cable  94  is coupled to a seat latch (not shown), such that the act of winding the spool  86  retracts the cable  94  into the gear case  58  and moves the latch from a first locked position to a second retracted position and, in some embodiments, to a third retracted position. For example, a two-stage latch, found in many vehicle seat applications, refers to a mechanism with two discrete latches, or a single latch with two different latch stages or positions, to be released consecutively via actuation of a single cable. Such a latch can move a seat from an upright position to a folded position and from a folded position to a “tumbled” position. 
         [0022]    The biasing assembly  22  includes a biasing member  102  in the form of a compression spring, a plunger  106 , and a housing  110  coaxially encasing the spring  102 , the plunger  106 , and a portion of the cable  94 . The plunger  106  includes an aperture  114  through which a portion of the cable  94  passes and is secured for movement therewith. The plunger  106  includes a flange  118  presenting a surface  120  on which the spring  102  is engaged such that retraction of the cable  94  compresses the spring  102  as the plunger  106  moves from a distal end  122  toward a proximal end  126  of the housing  110 . The spring compression biases the plunger  106  and correspondingly the cable  94  into a first position during retraction of the cable  94  into the gear case  58 . In an alternative embodiment, the biasing assembly  22  as previously described is replaced with a biasing member in the form of a torsional spring (not shown) positioned within the gear case  58  and mounted coaxially with the sun gear  62 . 
         [0023]    Referring to  FIGS. 2 ,  3 , and  8 , the circuit assembly  46  further includes a power supply in the form of a battery  130  coupled to the electrical terminal  54 . A controller  134  controls the supply of power to the motor  34 . A motor driver  140  includes a switch  150  such as a solid state switch (e.g., a MOSFET) with a gate for receiving a signal from the controller  134  to control the operation of the switch, either open or closed. The motor driver  140  includes an integrated current sensor  146  proximal the electrical switch to provide a measurement of the current flowing to the motor  34 . The current sensor  146  provides feedback that the controller  134  processes to determine the current level flowing though the electrical switch. The controller  134  includes a processor for carrying out real-time calculations (e.g. control algorithms) and memory for storing information (e.g. motor parameters). 
         [0024]    Electrical current levels to the motor  34  change as the corresponding load (seat latch positions) driven by the motor  34  changes. As will be further described below, the controller  134  releases the latch by comparing real-time electrical current measurements from the sensor  146  with a previously generated current waveform representative of unlatching the seat latch through its course of travel. 
         [0025]      FIG. 9  illustrates a current waveform, or profile  158  of a motor current as a function of time for the unlatching of a two-stage latch. As illustrated, the motor current value differs as the two-stage latch moves from a locked position (A) to a first unlocked position (B) in which the back of the seat is foldable, and from there to a second unlocked position (D) in which the entire seat can tumble forward. The electrical current drawn by the motor as the latch moves from a first position to a second position and/or a third position is unique and depends on both the latch and the operating conditions. 
         [0026]    With reference to  FIG. 11 , to utilize the characteristics of the motor&#39;s current waveform during operation, the controller  134  is configured to record the measured electrical current from the current sensor  146  during a testing procedure of the motor assembly  14  (step  200 ). Specifically, electrical current from the integrated current sensor  146  is measured and recorded through the full range of motion for an identified latch mechanism. Because changes in the load from the latch, the operating temperature, the operating life, and/or the supplied voltage can alter the current profile  158  of the motor, testing is done for a plurality of operating conditions in various combinations. The recorded current profiles from testing at different operating conditions provide a set of data representing the motor operational characteristics during release of the latch. 
         [0027]    Once recorded by the controller  134  this motor current data set is separately analyzed (e.g., using an external computer) in order to ascertain how it relates to the physical latch position (step  204 ). The current data exhibits recognizable characteristics (e.g., spikes, valleys, and plateaus) as a function of time. These characteristics include not only the values of the current over time but the changes in current levels within a certain time period (i.e., the slope of the current, di/dt) and are correlated directly with specific positions of the latch during the course of motor operation. Referring again to  FIG. 9 , an analysis of the current profile  158  demonstrates that the first stage of the two-stage latch is pulled at time A and released at time B. Following the release of the first stage latch, the second stage is pulled at time C and subsequently released at time D. Such an analysis thereby establishes an operating profile of the motor  34  for the latch that takes into account various operating conditions. This is saved into the controller memory  154 . 
         [0028]    The processor is loaded with instructions to enable comparison of the real-time current to the stored information using a pattern recognition technique (to, for example, calculate the rate of change of electrical current with respect to time) (step  208 ). In an alternative embodiment, the rate of change of electrical current can be calculated in hardware (e.g. analog circuits) in place of calculating the same using the processor. 
         [0029]    In operation, upon input by the user to position a seat, (e.g., through a push button) the controller  134  operates the power supply  130  to provide power to the motor  34  (step  212 ) and rotate the worm gear  42 . The worm gear  42  drives the transmission  78 , which rotates the spool  86  to wind the cable  94  thereon, retracting it into the gear case  58 . As the cable  94  is retracted into the gear case  58 , the plunger  106  of the biasing assembly  22  moves with the cable  94 , compressing the spring  102  as the plunger  106  slides within the spring housing  110 . 
         [0030]    As the cable  94  retracts, it activates the latch through one or more stages. The controller  134  accesses the operating profile information from memory  154  and compares the electrical current measurements obtained from the current sensor  146  in real-time (step  216 ), and in view of the operating time, to the stored operating profile information during the entire operation of the motor  34  (step  220 ). The controller  134  identifies when the latch is being pulled to a release point and when the latch has been released (e.g., when a single stage latch has been released or when the first and second stages of a two-stage latch have been released) (step  224 ). The controller  134  continues to operate the motor  34  and measures the current (step  216 ). After ascertaining that the latch has been released at step  224 , the controller  134  controls the power supply  130  to remove power from the motor  34 , ceasing rotation of the worm gear  42  (step  228 ). With no power supplied to the motor assembly  14 , the spool  86  is free to rotate and, under the biasing force of the spring  102 , rotates in the opposite direction as the cable  94  unwinds back to the first position. The cable  94  therefore moves from the retracted position to the first position without assistance from the motor  34 . 
         [0031]    Referring again to  FIG. 9 , without the control system of the invention, shortly after full release of the second latch (or position) of a two-stage latch, the cable reaches the end of its travel. Without proper control, the motor  34  remains powered and proceeds to a stall condition at time E after the second stage is released at time D (through a “hard stop” at the end of travel for the latch). A stall condition can damage and reduce the life of the motor  34 . Specifically, at time E, the motor enters a current limiting state and only then does the controller, after a time lag as illustrated, power down the motor  34  at time F. The motor shortly thereafter comes to a complete halt at time G. 
         [0032]    A recorded current profile  162  of the motor  34  with the controller  134  and method embodying the present invention is illustrated in  FIG. 10 . The latch is determined to be released by the controller  134  after the real-time comparison of the measured electrical current and the stored information from testing identifies the level, rate of change, and timing of the electrical current as matching the corresponding physical release of the latch for the given operating conditions. The current profile  162  eliminates the current limit condition at time E in  FIG. 9  by powering down the motor  34  at time H before a stall condition occurs. By stopping the motor  34  before the actuator assembly  10  is fully retracted, the motor  34  is protected from the damaging stall current condition resulting from continuing to power the motor  34  after the latch has been released. Specifically, at time H, the controller  134  determines the latch has been released (step  224 ) and powers down the motor  34  (step  228 ) allowing the biasing assembly  22  to act at time I. Following the return of the cable  82  to the first position, at time J the motor  34  has stopped rotating. 
         [0033]    To account for variability over time, a learning algorithm can be loaded onto the processor  150  to compensate for the load changes in the latch (for example, at step  208 ). The learning algorithm recognizes if the motor assembly  14  was powered for too long or not long enough based on the measured electrical current at the end of every actuation cycle and makes necessary adjustments during the subsequent actuation cycle. For example, if the motor  34  experienced a current limit in the previous actuation cycle as a result of a hard stop, then the controller  134  will, in the following actuation cycle, power down the motor  34  at an earlier point in time to keep the current within an acceptable range. 
         [0034]    As a result of being able to analyze the current profile  162  to determine if and when the latch releases, the recorded operating profiles in combination with the current readings from the sensor  146  can be substituted for conventional position feedback signals (e.g. from an encoder, resolver, Hall-effect sensor, potentiometer, etc.), reducing component costs and potential failure and saving space in any given application. 
         [0035]    Various features and advantages of the invention are set forth in the following claims.