Abstract:
The present invention is a method and apparatus of performing vehicle obstruction sensing during vehicle reverse and liftgate opening movements. The invention uses the same sensors to perform both functions. When the vehicle is in reverse, the invention produces a visible and/or audible signal to the operator of the vehicle when an obstruction detected within the monitoring range of the sensor or sensors. When the vehicle transmission is in any position other than park, the liftgate driver is disabled. When the vehicle is in park, the liftgate sensing system is enabled. The invention either stops the liftgate opening movement or reverses the liftgate movement when an obstruction is detected. The invention can also signal an alarm when an obstruction is detected in the path of the liftgate. The present invention incorporates any number of existing sensors.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates in general to sensors located on a vehicle used to detect obstructions.  
         BACKGROUND OF THE INVENTION  
         [0002]    Vehicles with reverse sensing systems use one or more sensors on the rear bumper of the vehicle to sense obstacles to the rear of the vehicle while it is backing up. The sensors typically alert the driver through audible and/or visible indicators. In general, a reverse sensing system is only enabled when the vehicle gear select lever is in the “reverse” position.  
           [0003]    Some vehicles are equipped with a power liftgate actuator system. In such systems, the liftgate is driven to the open position at the touch of a button. Vehicles with this system are at a risk of the liftgate colliding with outside obstacles and causing vehicle damage during the opening movement if the operator is not diligent at assuring that the liftgate path is clear of obstacles. Some software algorithms used to control the liftgate have sensing to react when an obstruction is encountered, then reverse or discontinue the drive power to the liftgate. This method does not prevent the damage from occurring, but only reacts after impact, thereby failing to eliminate the risk of vehicle damage.  
           [0004]    What is needed is the ability to sense obstacles in the path of the liftgate prior to any contact with the liftgate and to automatically stop the opening movement of the liftgate when an obstacle is detected. Ideally, such a system should be integrated with the rear obstacle detector system.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention employs the sensors used for sensing objects when a vehicle is in reverse to also prevent vehicle damage when the power liftgate is activated. Specifically, the method for sensing an obstruction to the rear of a vehicle comprises the steps of disposing at least one sensor in the liftgate and generating a first signal when the sensor indicates an obstruction when the liftgate is opening. In another aspect of the invention, the method further comprises the step of generating a second signal when the sensor indicates an obstruction when the vehicle is reversing.  
           [0006]    The apparatus of the present invention comprises at least one sensor disposed in the liftgate and means for generating a first signal when the sensor indicates an obstruction when the liftgate is opening. In another aspect of the invention, the apparatus further comprises means for generating a second signal when the sensor indicates an obstruction when the vehicle is reversing.  
           [0007]    Preferably, the first signal sent from the controller when the sensor indicates an obstruction in the liftgate path could be either an audible and/or a visible alarm, or it could be a signal stopping or reversing the liftgate driver, typically a motor. The second signal sent from the controller when the sensor indicates and obstruction to the rear of the vehicle while it is reversing could be either an audible and/or a visible alarm.  
           [0008]    In one aspect of the invention, the system disables the power liftgate driver when the vehicle is not in park.  
           [0009]    Thus, the present invention, by locating the sensor or sensors at one or more locations on the liftgate, allows the sensors to remain functional as detectors for obstacles when the vehicle is reversing, continuing to activate appropriate warnings for the vehicle operator. Further, when the power liftgate is deployed, the sensor or sensors act as anticipators to prevent liftgate collisions with outside obstructions by stopping or reversing the liftgate or warning the vehicle operator. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The various features, advantages, and other uses of the present invention will become more apparent by referring to the following detailed description and drawings in which:  
         [0011]    [0011]FIG. 1A is a pictorial diagram of a vehicle with a liftgate, which vehicle incorporates the present invention;  
         [0012]    [0012]FIG. 1B is the rear view of the vehicle of FIG. 1A;  
         [0013]    [0013]FIG. 2 is a data flow diagram of vehicle control components involved in carrying out the present invention; and  
         [0014]    [0014]FIG. 3 is a flow diagram illustrating the method according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0015]    Referring to FIGS. 1A and 1B, shown is a vehicle incorporating the present invention. The vehicle  10  includes a power liftgate  12  and a bumper  14 . Disposed in the liftgate  12  is at least one sensor  16  located toward the bottom edge of the liftgate  12  near the bumper  14 . In one aspect of the invention, one sensor  16  is disposed in the center of the liftgate  12 . In another aspect of the invention, two sensors  16  are disposed in opposite corners of the liftgate  12  on the same horizontal plane. Although the invention is shown incorporating either one or two sensors  16 , more than two sensors could be used. The number of sensors used is dependent on the field of view of the sensors. The sensors  16  should be placed so that their fields of view overlap and/or cover the entire length of the bumper  14  from end to end. Additional sensors could be located on the bumper  14  to perform sensing when the vehicle is reversing.  
         [0016]    The sensors  16  are common sensors used for electronically sensing objects in the path of the sensors, which would indicate an obstruction to the vehicle on which the sensor is mounted. Such sensors  16  may be ultrasonic, charge coupled device (CCD) camera, radar, etc. A typical sensor includes a transceiver that transmits signals and subsequently receives signals reflected from an object in the sensor path. The reflected signals are emitted as a signal to a processor coupled to the transceiver, where the processor analyzes the received signal to detect the presence, and often the distance, of an obstruction. A conventional ultrasonic sensor typically emits ultrasonic waves utilizing the resonance phenomena exhibited by an ultrasonic resonator, and the resonator receives reflected waves from an object, which waves are analyzed by the processor. Similarly, a CCD camera emits light according to a predetermined wavelength and receives a reflection of that light for analysis. The radar sensor generally operates using transmission of a frequency modulated carrier signal. An example of a vehicle exterior object sensor is described in U.S. Pat. No. 5,844,471, which is incorporated herein by reference.  
         [0017]    Referring now to FIG. 2, the engine controller  62  receives an indication of gear position. The controller  62  may be a conventional microcontroller which includes such elements as a central processing unit (CPU), read only memory, random access memory, input/output control circuitry, and analog to digital conversion circuitry. The controller  62  is activated upon application of ignition power to an engine. When activated, the controller  62  carries out a series of operations stored in an instruction-by-instruction format in memory for providing engine control, diagnostic and maintenance operations. Preferably, the transmission  60  of the vehicle provides the indication of gear position to the controller  62 . Alternatively, the vehicle gear select lever provides the gear indication.  
         [0018]    The sensors  16  provide signals  64  to the controller  62  indicating the presence of an object in the path of each sensor. The controller  62  receives and analyzes the signals  64  to determine whether an obstruction is present, requiring an actuator signal to a liftgate driver  66 , usually a motor, or a signal to an automobile warning system  68  or both.  
         [0019]    [0019]FIG. 3 shows how the sensors  16  are used to perform reverse sensing and liftgate damage avoidance according to the method of the present invention. The procedure starts at step  20  upon initialization of power to an engine controller  62 . Then, the procedure makes a query as to whether the vehicle ignition is “on” or not in step  21 . If the vehicle ignition is “on,” the procedure advances to step  22 , where a query is made as to whether the vehicle is in park. If the vehicle is in park, the procedure advances to step  24 . At step  24 , a query is made as to whether the power liftgate  12  is active, which means that the liftgate driver  66  is energized. If the liftgate  12  is not active, then the procedure returns to step  22 . If, however, the liftgate  12  is active, the procedure advances to step  26 .  
         [0020]    Returning now to step  21 , if the vehicle ignition is not “on,” the procedure advances directly to step  24  to determine whether the power liftgate  12  has been activated.  
         [0021]    Powered systems for opening and closing a vehicle liftgate are known in the art. Generally, such systems comprise a pair of drive units attached to the vehicle frame and connected to the liftgate. Each drive unit includes a bracket secured to the vehicle body, supporting several parts including a reversible electric driver, usually a motor, a gear train, a rack and a cradle mounted on the bracket. The electric driver drives the rack from a retracted position to an extended position and back via an output gear with an axis. The rack slides in the cradle, which cradle is pivotally mounted on the bracket so that the cradle pivots about the axis of the output gear to hold the teeth of the rack in engagement with the teeth of the output gear. The electric driver is controlled via electric motor controls, well known to those skilled in the art.  
         [0022]    In step  26 , the liftgate sensing system is enabled when the power liftgate is activated. The procedure then advances to step  28 , where a query is made as to whether an obstruction has been detected by the sensors  16 . If an obstruction has not been detected, i.e., an object is not within the range of view of a sensor  16 , the sensors  16  continue to be monitored until the liftgate  12  is no longer activated, shown in step  30 . If the liftgate  12  is activated, then the procedure returns to step  28  to determine if an obstruction is detected. If the liftgate  12  is no longer activated, then the procedure advances to step  32 , where the liftgate sensing system is disabled. The procedure then ends at step  34 .  
         [0023]    Returning now to step  28 , if an obstruction is detected by the sensors  16 , then the procedure advances to step  36 , where the operation of the liftgate is halted or reversed by an actuator signal provided to the electric driver  66  of the power liftgate actuator system. In one aspect of the invention, in addition to halting or reversing the operation of the liftgate, a warning could be transmitted to the driver, similar to the warning provided to the driver when an obstruction is detected by the reverse sensing system. The procedure advances to step  32 , where the liftgate sensing system is disabled. Then, the procedure ends at step  34 .  
         [0024]    Returning now to step  22 , if the vehicle is not in park, the procedure advances to step  38 , where the power liftgate driver  66  is disabled. Next, a query is made in step  40  as to whether the vehicle is in reverse. If the vehicle is not in reverse, the procedure ends at step  34 . If the vehicle is in reverse, then the procedure advances to step  42 . In step  42 , the reverse sensing system is enabled. In step  44 , the query is made as to whether the sensors  16  have detected an obstruction. If an obstruction has not been detected in step  44 , the procedure advances to step  46  where a query is made as to whether the vehicle is still in reverse. If the vehicle is still in reverse, the procedure returns to step  44  to check the sensors  16  for detected objects. If, however, the vehicle is no longer in reverse, then the procedure advances to step  48  where the reverse sensing system is disabled. The procedure then ends at step  34 .  
         [0025]    Returning now to step  44 , if an obstruction is detected by the sensors  16 , the procedure advances to step  50 , where a warning is sent to the driver. The warning can be a visual and/or an audible alarm, conventional in the art. An audible alarm is generally a solid state piezoelectric alarm, while a visual alarm generally comprises a lamp or lamps lit or flashing when an obstruction is detected. Generally, the audible alarm sounds a warning of an obstruction that beeps faster and/or at a higher pitch as the vehicle approaches the obstruction. Similarly, the closer the obstruction is to a vehicle equipped with a visual alarm, the increasingly bright the lamp, or the faster the lamp flashes. After the warning is sent, the procedure returns to step  46  where a query is made as to whether the vehicle is in reverse. If the vehicle is still in reverse, the procedure returns to step  44  to check the sensors  16  for detected obstructions. If, however, the vehicle is no longer in reverse in step  46 , the reverse sensing system is disabled in step  48 . The procedure then ends at step  34 .  
         [0026]    The procedure runs continuously at predetermined intervals while engine power is on. When the engine is off, the procedure is performed when the liftgate  12  is activated.  
         [0027]    The method and apparatus of the present invention provides a vehicle with a unique system that provides detection of obstructions while the vehicle is reversing, and also provides a sensing system to avoid liftgate damage. The invention uses the same sensors to perform both functions.