Patent Publication Number: US-2012023910-A1

Title: Particulate Filter Regeneration Control System and Method

Description:
TECHNICAL FIELD 
     The present disclosure relates to particulate filter regeneration. 
     BACKGROUND 
     A byproduct of fuel combustion, especially diesel fuel combustion, is carbon particles, which are referred to as soot. Emissions regulations limit the amount of soot and particulates that an engine may exhaust to the environment. 
     Emission control devices, such as particulate filters, reduce the amount of soot emissions from an engine by trapping soot particles. As the particulate filter becomes saturated with soot, the filter may be regenerated, to decrease the amount of trapped particulate matter and restore the performance of the filter. Regeneration is typically achieved by raising the temperature of the filter to a predetermined level to oxidize or burn the accumulated particulate matter. 
     Regeneration may be accomplished by injecting additional fuel into the exhaust stream, or altering the operation of the engine to increase exhaust temperature. Typically, filter regeneration may be performed during normal driving conditions and does not affect vehicle driveability so that the driver is unaware that regeneration of the filter has occurred. However, various applications may also include an operator commanded regeneration, such as during vehicle servicing, or for off-road vehicles including industrial and construction vehicles, for example. 
     SUMMARY 
     A system and method for controlling regeneration of a diesel particulate filter in a vehicle engine exhaust is provided. In one embodiment, the system and method include detecting a distance of an object from the exhaust and controlling a regeneration event if the distance is less than a threshold value. In another embodiment, the system and method include a particulate filter disposed in the exhaust of the vehicle and a proximity sensor disposed adjacent an exhaust opening and positioned to detect presence of an object near the opening. A controller in communication with the proximity sensor is adapted for controlling regeneration of the particulate filter in response to the proximity sensor detecting the object near the opening. 
     According to another embodiment, the system and method include terminating the regeneration event if the distance detected by the proximity sensor is less than the threshold value. In a further embodiment, the system and method include preventing initiation of the regeneration event if the distance detected by the proximity sensor is less than the threshold value. In yet another embodiment, the system and method include displaying a message for an operator if the distance is less than the threshold value. 
     Embodiments according to the present disclosure may provide various advantages. For example, systems and methods for controlling DPF regeneration according to the present disclosure reduce or eliminate the possibility for heat discharged during regeneration to adversely affect any object or person near the vehicle exhaust. Use of existing vehicle proximity sensors that may also be used for parking and/or back-up maneuvers provides additional feature functionality without requiring additional vehicle hardware and associated costs and complexity. 
     The above advantages and other advantages and features will be readily apparent from the following detailed description of representative embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating operation of a system or method for controlling an internal combustion engine and exhaust system according to an embodiment of the present disclosure; 
         FIG. 2  illustrates a vehicle including the engine and exhaust system according to  FIG. 1 ; and 
         FIG. 3  is a flow chart illustrating operation of a system or method for controlling regeneration of a particulate filter according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed representative embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the claimed features. As those of ordinary skill in the art will understand, various features of the present disclosure as illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce embodiments of the present disclosure that may not be explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. 
       FIG. 1  illustrates a schematic diagram showing one cylinder of multi-cylinder engine  10 , which may be included in a propulsion system of a vehicle, such as an automobile, truck, or stationary or mobile construction or industrial vehicle, for example. Those of ordinary skill in the art will recognize that various components of engine  10  may vary depending on the particular type of engine and/or the particular application. Engine  10  generally represents a compression ignition engine powered by diesel fuel. However, various features of the present disclosure may also be applied to spark-ignited engines powered by gasoline, gaseous fuel, or dual fuel engines, for example. 
     Engine  10  may be controlled at least partially by a control system including a controller  12  and by input from a vehicle operator  14  via an input device  16 . In this example, the input device  16  includes an accelerator pedal and a pedal position sensor  18  for generating a proportional pedal position signal PP. Other input devices may also be used. For example, in construction or industrial applications, input device  16  may be implemented by a dial, knob, lever, digital control, etc. The combustion chamber or cylinder  30  of engine  10  may include combustion chamber walls  32  with a piston  36  positioned therein. The piston  36  may be coupled to crankshaft  40  so that reciprocating motion of the piston  36  is translated into rotational motion of the crankshaft  40 . The crankshaft  40  may be coupled to at least one drive wheel of a vehicle via an intermediate transmission system. Further, a starter motor may be coupled to crankshaft  40  via a flywheel to enable a starting operation of engine  10 . 
     The cylinder  30  may receive intake air via an intake passage  42  in intake manifold  44  and may exhaust combustion gases via exhaust passage  48 . The intake manifold  44  and exhaust passage  48  can selectively communicate with the cylinder  30  via respective intake valve  46  and exhaust valve  50 . In some embodiments, the cylinder  30  may include two or more intake valves and/or two or more exhaust valves. A fuel injector  52  is illustrated coupled directly to the cylinder  30  for injecting fuel directly into the cylinder  30 . The fuel injector  52  injects fuel in proportion to the pulse width of signal FPW received from controller  12 . In this manner, the fuel injector  52  provides what is known as direct injection of fuel into the cylinder  30 . The fuel injector  52  may be mounted along the side of the cylinder  30  or in the top of the cylinder, for example. 
     Fuel may be delivered to fuel injector  52  by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail. In some embodiments, the fuel injector  52  is arranged in intake passage  42  in a configuration that provides what is known as port fuel injection of fuel into the intake port upstream of the cylinder  30 . Although  FIG. 1  shows only one cylinder of a multi-cylinder engine, each cylinder may similarly include its own set of intake/exhaust valves, fuel injector, spark plug, etc. 
     The intake passage  42  may include a throttle  62  having a throttle plate  64 . In this particular example, the position of the throttle plate  64  may be varied by controller  12  via a signal provided to an electric motor or actuator included with the throttle  62 , a configuration that is commonly referred to as electronic throttle control (ETC). In this manner, the throttle  62  may be operated to vary the intake air provided to the cylinder  30  among other engine cylinders. The position of throttle plate  64  may be provided to the controller  12  by the throttle position signal TP. The intake passage  42  may include a mass air flow (MAF) sensor  60  and a manifold air pressure (MAP) sensor  66  for providing the MAF and MAP signals, respectively, to the controller  12 . Various implementations may use other airflow control devices in combination with or in place of throttle  62 . For example, applications having electromagnetically actuated intake/exhaust valves  46 , 50  may use valve timing to control intake airflow. Some compression ignition engines, particularly those that do not use exhaust gas recirculation, may not include a throttle  62 . 
     The controller  12  may receive various signals from sensors coupled to engine  10 . In addition to those signals previously discussed, the controller may receive signals measuring engine coolant temperature (ECT) from temperature sensor  54  coupled to cooling sleeve  56 ; a profile ignition pickup signal (PIP) from Hall effect sensor  58 , or other suitable sensor, coupled to crankshaft  40 ; or throttle position (TP) from a throttle position sensor. An engine speed signal, RPM, may be generated by the controller  12  from signal PIP. The manifold pressure signal MAP from the manifold pressure sensor  66  may be used to provide an indication of vacuum, or pressure, in the intake manifold. Note that various combinations of the above sensors may be used, such as a MAF sensor  60  without a MAP sensor  66 , or vice versa. During stoichiometric operation, the MAP sensor  66  can give an indication of engine torque. Further, the MAP sensor  66 , along with the detected engine speed, can provide an estimate of charge, including air, inducted into the cylinder  30 . In one example, sensor  58 , which is also used as an engine speed sensor, may produce a predetermined number of equally spaced pulses every revolution of the crankshaft  40 . 
     The cylinder  30 , or one or more other the cylinders of engine  10 , may be operated in a compression ignition mode, with or without an ignition spark provided by an associated spark plug (not shown). Further, engine  10  may be turbocharged by a compressor  70  disposed along the intake manifold  44  and a turbine  72  disposed along the exhaust passage  48  upstream of the exhaust after-treatment system  80 . 
     An exhaust gas sensor  74  is illustrated coupled to exhaust passage  48  upstream of the exhaust gas after-treatment system  80 . The exhaust gas sensor  74  may be any suitable sensor for providing an indication of exhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. An exhaust gas recirculation (EGR) system  76  may be coupled to the exhaust passage  48 . The EGR system may include an EGR valve  77  and an EGR cooler  78  disposed along the EGR conduit  79 . 
     The exhaust gas after-treatment system  80  may include a plurality of emission control devices, each of which may carry out an exothermic reaction with excess oxygen present in the exhaust during selected conditions, such as selected temperatures. For example, the exhaust gas after-treatment system  80  may include a diesel oxidation catalyst (DOC)  82  disposed along exhaust gas conduit  48  downstream of turbine  72 . A selective catalytic reduction (SCR) catalyst  84  may be disposed along the exhaust gas conduit  48  downstream of the DOC  82 . The selective catalyst reduction process may use a diesel exhaust fluid injector  85 . The diesel exhaust fluid injector  85  may be a urea sprayer, or any suitable ammonia source. The diesel exhaust fluid injector  85  may be disposed upstream of the SCR catalyst  84  and downstream of the DOC  82 . 
     The exhaust gas after-treatment system  80  also includes a diesel particulate filter (DPF)  86 . The DPF  86  may be disposed along the exhaust conduit  48  downstream of the SCR catalyst  84 . Pressure and/or temperature sensors  88 ,  90 ,  92 , and  94  may be disposed at points along the exhaust gas conduit  48  both upstream and downstream of each after-treatment device in the after-treatment system  80 . Further, an oxygen sensor  96 , such as an UEGO sensor, may be disposed downstream of the exhaust after-treatment system  80 . It is also contemplated that in a gasoline application, the exhaust gas after-treatment system may include a particulate filter, such as a gas particulate filter (GPF). 
     The DPF  86  may be manufactured from a variety of materials including cordierite, silicon carbide, and other high temperature oxide ceramics. Once soot accumulation in the DPF  86  has reached a predetermined level, regeneration of the DPF  86  may be automatically initiated and controlled according to the present disclosure. Alternatively, a DPF regeneration may be requested by an associated operator alert, message, light, etc. to suggest a manual or operator-initiated DPF regeneration, which is initiated by the operator. Similarly, a DPF regeneration may be manually initiated during vehicle servicing. Soot accumulation in the DPF  86  may be identified by a pressure drop, for example across pressure and/or temperature sensors  88 ,  90 ,  92 , and  94 . 
     It should be understood that exhaust after-treatment system  80  may include a plurality of after-treatment device configurations not shown in  FIG. 1 . In one example, the exhaust after-treatment system  80  may only include a DOC  82 . In another example, the exhaust after-treatment system  80  may include a DOC  82  followed downstream by a DPF  86 . In another example, the exhaust after-treatment system  80  may include the DOC  82  followed downstream by a DPF  86  then the SCR catalyst  84 . In still another example, the SCR catalyst  84  shown in  FIG. 1  may be replaced with a lean NOx trap (LNT). Further, the order of the different catalysts and filters in the exhaust after-treatment system  80  may also vary. The number of pressure and/or temperature sensors disposed within the exhaust after-treatment system  80  may also vary according to the application. Though the oxygen sensor  96  is shown in  FIG. 1  at a point located downstream of exhaust after-treatment devices, it may be located upstream of any of the devices in the after-treatment system  80 , in which case it can only monitor the catalysts upstream of the oxygen sensor  96 . It is also contemplated that in a gasoline application, the exhaust gas after-treatment system may include a three-way catalyst (TWC), or other suitable catalyst, instead of or the DOC and a GPF instead of a DPF. 
     Regeneration of the DPF  86  may be accomplished by heating the DPF  86  to a temperature that will burn soot particles at a faster rate than the deposition of new soot particles, for example 400-600 degrees Celsius. In one example, the DPF  86  can be a catalyzed particulate filter containing a washcoat of precious metal, such as platinum, to lower soot combustion temperature and also to oxidize hydrocarbons and carbon monoxide to carbon dioxide and water. 
     In another embodiment, an injector  87  may be used to deliver fuel from the fuel tank or from a storage vessel to the exhaust system to generate heat for heating the DPF  86  for regeneration purposes. The injector  87  may be located upstream of the DOC  82 . In addition, late fuel injection by the injector  52  during an exhaust stroke of the piston  36  may be used to raise exhaust temperature for regeneration purposes. 
     Alternatively, to regenerate the DPF  86 , a regeneration injection strategy may be implemented. The regeneration injection strategy may implement an injection profile including a plurality of injection events such as a pilot fuel injection, a main fuel injection, a near post fuel injection, and/or a far post fuel injection. It will be appreciated that the aforementioned fuel injections may include a plurality of injection events, in other embodiments. Thus, the DPF  86  may be regenerated during operation of the engine  10 . For example, the temperature downstream of the DOC  82  and upstream of the DPF  86  may be controlled to a desired value to promote combustion of particulate matter within the DPF  86 , by adjustment of the amount of the various injections. In this example, a temperature set-point downstream of the DOC  82  and upstream of the DPF  86  may be established to facilitate regeneration of the DPF  86 . 
     The controller  12  in  FIG. 1  may be a microcomputer also referred to as a central processing unit (CPU), including microprocessor unit, input/output ports, and electronic storage medium for executable programs and calibration values. Computer readable storage media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM may be used to store various operating variables or control system parameter values while the CPU is powered down. Computer-readable storage media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions or code, used by the controller  12  in controlling the engine or vehicle into which the engine is mounted and for performing on-board diagnostic (OBD) monitoring of various engine/vehicle features. Computer-readable storage media may also include floppy disks, CD-ROMs, hard disks, and the like. 
     The controller  12  may communicate with various engine/vehicle sensors and actuators via an input/output (I/O) interface that may be implemented as a single integrated interface providing various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to the controller  12 . 
     The controller  12  may also communicate with a vehicle cluster display  98 . The cluster display  98  may be located in the passenger compartment  102  to alert the driver of service information relative to engine  10  or exhaust after-treatment system  80 , for example. As described in greater detail herein in  FIG. 3 , the controller  12  may monitor at least one exhaust after-treatment system  80  parameter to determine whether DPF regeneration is needed. Controller may display information to an operator relative to regeneration of the DPF using cluster display  98 . The controller  12  includes control logic to detect when the DPF  86  requires regeneration. This information may be communicated to the operator using cluster display  98 . Depending on the particular application and implementation, cluster display  98  may also provide a user input to request a manual or operator-initiated DPF regeneration using a touch screen, switch, button, etc. The controller  12  may also communicate with a proximity sensor  110 , described in more detail below. Proximity sensor  110  may be used to detect an object within a predetermined distance of the exhaust with cluster display  98  used to display a corresponding message when DPF regeneration is otherwise indicated. 
     Referring now to  FIG. 2 , a vehicle  100  including the engine  10  and exhaust after-treatment system  80  is shown. The vehicle  100  includes the proximity sensor  110  mounted along the rear panel or portion  112  of the vehicle. In one embodiment, as illustrated in  FIG. 2 , the proximity sensor  110  is mounted on the bumper  114  of the vehicle  100 . In another embodiment, the vehicle  100  may include a plurality of proximity sensors  110  which are mounted at spaced apart locations along the rear portion  112 . By mounting the proximity sensors  110  along the rear portion  112  or the bumper  114 , the proximity sensors  110  may be mounted adjacent an exhaust opening or tailpipe  116 . 
     In most vehicles, DPF regeneration can occur while the vehicle is driving during normal operation because the exhaust temperature and regeneration strategies may be implemented with little or no effect on the drivability of the vehicle. However, some vehicles and drivers never experience drive cycles which allow automatic regeneration. For example, urban commuters and utility trucks, which do not experience highway driving and/or have start-and-stop driving cycles, will generally not have exhaust temperatures sufficient for regeneration and, therefore, need to have operator initiated regeneration. Elevated exhaust temperatures may adversely affect objects in the proximity of the engine exhaust opening during an operator-initiated regeneration when the vehicle is stopped. The exhaust temperature may be between 400° C. and 600° C. which may adversely impact people or objects such as trees, buildings, garage doors, fuel containers, or other combustible objects close to the exhaust during regeneration. 
     The proximity sensors  110  may be used to detect the presence and/or distance of an object  120  from the tailpipe  116  to control the regeneration of the DPF  86 . The proximity sensors  110  are sensors which may detect a distance of an object from the sensor. Proximity sensors  110  may be any suitable sensors such as a sonar-based proximity sensor, a laser-based proximity sensor, an ultrasonic-based proximity sensor, or any other sensor suitable for detecting the presence and/or distance of an object. The proximity sensors  110  may include electrical wiring for electrically connecting the proximity sensor  110  to the controller  12  or, alternatively, the proximity sensors  110  may communicate wirelessly with the controller  12 . The proximity sensors  110  may be parking-aid sensors or back-up sensors already present in some vehicle systems. By utilizing existing components, this DPF regeneration system minimizes cost and vehicle complexity. The proximity sensors  110  may also offer advantages over back-up cameras which require operator monitoring and do not automatically detect the distance of an object  120 . Further, it is possible to include a plurality of proximity sensors  110  located at spaced apart locations to offer a wider range for detecting objects  120  behind and along the side of the vehicle  100 , for example. 
     In one embodiment, vehicle  100  includes a proximity sensor  110  disposed adjacent to an exhaust opening of tailpipe  116  and positioned to detect distance “x” and/or presence of an object  120  near the opening. Controller  12 , in communication with proximity sensor  110  is adapted for controlling regeneration of particulate filter  86  in response to proximity sensor  110  detecting object  120  near the opening. In the representative embodiment illustrated in  FIG. 2 , a plurality of proximity sensors  110  are mounted on bumper  114  of vehicle  100  proximate the exhaust opening of tailpipe(s)  116 . 
     Referring now to  FIG. 3 , a simplified block diagram or flowchart is shown illustrating operation of a system for controlling the regeneration of the DPF using proximity sensors  110 . The regeneration event may be operator-initiated or automatically initiated in appropriate vehicle circumstances. As those of ordinary skill in the art will understand, the functions represented by the flowchart may be performed by hardware and/or software. Depending on the particular processing strategy, such as event driven, interrupt driven, etc., the various functions may be performed in an order or sequence other than that illustrated in  FIG. 3 . Likewise, one or more steps or functions may be repeatedly performed although not explicitly illustrated. Similarly, one or more of the steps or functions illustrated may be omitted in some applications or implementations. In one embodiment, the functions illustrated are primarily implemented by software instructions, code, or control logic stored in a computer-readable storage medium and executed by a microprocessor based computer or controller to control operation of the vehicle, such as controller  12  ( FIG. 1 ). 
     First, the controller monitors the DPF conditions, as represented by a block  210 . Various strategies may be used to determine the condition of the DPF and whether the DPF should be regenerated. In some examples, a threshold pressure differential across the DPF may be used to determine the condition of the DPF and whether the DPF should be regenerated. However, in other examples, condition of the DPF is approximated based on vehicle mileage or hours of engine operation and whether the vehicle has traveled over a threshold distance or has surpassed a threshold time interval of engine operation. In another example, as illustrated in  FIG. 3 , the condition of the DPF and whether the DPF should be regenerated is determined based on whether the amount of stored particulate is greater than a maximum threshold. 
     As represented by block  212 , the vehicle cluster display or message center may display information for the operator based on the condition of the DPF. Of course, a dedicated light or other service indicator may be used to convey similar information to the operator. The amount of particulate accumulated in the DPF may be displayed as a percentage where 100% would indicate that the DPF is full and requires regeneration. Alternatively, a percentage representing estimated remaining DPF capacity could be used. As the DPF nears a corresponding threshold, such as 100% particulate load, the vehicle cluster display informs the operator that the exhaust filter is full, as represented by block  214 . The vehicle cluster display may also display a message requesting operator input. The operator input may include pressing a button or switch or pressing an input on the vehicle cluster display or some other input from the operator such as a sequence of putting the vehicle in park and/or depressing the brake pedal, accelerator pedal, etc. 
     Once the controller has received the operator input, the controller checks the vehicle surroundings using the proximity sensors, as represented by block  216 . The controller determines if any objects are within a threshold distance of the vehicle. If any objects are detected within the threshold distance of the vehicle, the vehicle cluster display displays an appropriate message to the operator indicating that regeneration has been inhibited as represented by block  220 . In one embodiment, the threshold distance may be a fixed distance within which distance regeneration is inhibited. In another embodiment, the threshold distance may be a variable distance depending on various circumstances, such as the type of object detected by the proximity sensors. For example, if the proximity sensors detect a metallic object, the threshold distance may be less than if the proximity sensors detect an object such as a person or a tree. The threshold distance may also be variable depending on the detected exhaust temperature. If the exhaust temperature is lower, the threshold distance may be shorter. Alternatively, the sensors may only detect the presence of an object and indicate a yes/no signal if the object is within the range of the sensors, where the range of the sensors may be the threshold distance. Depending on the application, the threshold distance may be one meters to five meters, for example. Of course, other threshold distances are contemplated depending on the exhaust conditions. 
     If the controller does not detect any objects within a threshold distance of the vehicle, the vehicle cluster displays a message to the operator requesting the operator to confirm the vehicle is in a suitable location to initiate regeneration, as represented by block  222 . The operator may indicate the vehicle is in a suitable location using the operator input, as previously described. When the controller receives confirmation input, the controller initiates DPF regeneration as represented by block  223  using a strategy as previously described to increase the temperature of the exhaust provided to the DPF. The vehicle cluster display may then display a message to the operator indicating a regeneration event is occurring, as represented by block  224 . 
     Once the DPF regeneration is initiated, the controller may continue to monitor the surroundings of the vehicle using the proximity sensors during the regeneration event as represented by block  226 . If the controller does not sense any objects within the threshold distance, the regeneration event continues to complete cleaning of the exhaust filter, as represented by block  228 . However, if the proximity sensors detect an object within the threshold distance during DPF regeneration, the controller suspends and/or terminates the regeneration event, as represented by block  229 . The vehicle cluster display then displays an associated message that the exhaust cleaning has stopped as represented by block  230 . The vehicle cluster display may also indicate that an object has been detected near the exhaust as represented by block  232 . 
     Regeneration of the DPF may also be terminated by the operator, or stopped because of various vehicle conditions. The operator may terminate the regeneration event through an input such as pressing the brake pedal, shifting the vehicle into a drive gear, or by pressing a button or switch, for example. Once the regeneration event is terminated, the vehicle cluster display will indicate that the exhaust cleaning has stopped, as represented by block  230 , and the operator may reset the process. 
     In parallel with monitoring the proximity sensors, the controller monitors the regeneration event to determine if the exhaust cleaning is completed, as represented by block  234 . Monitoring of the regeneration event may include monitoring differential pressure or continuing the event for a specified time period, for example. The controller will automatically terminate the regeneration event when the DPF is cleaned and the vehicle cluster display will display a message indicating to the operator that the exhaust filter is cleaned and regeneration is completed, as represented by block  236 . 
     Those of ordinary skill in the art will recognize that various features of the present disclosure may be applied to engine and vehicle applications other than DPF regeneration where exhaust temperatures within some proximity of the vehicle may adversely affect surrounding objects. 
     As such, systems and methods for controlling DPF regeneration according to the present disclosure reduce or eliminate the possibility for heat discharged during regeneration to adversely affect any object or person near the vehicle exhaust. Use of existing vehicle proximity sensors that may also be used for parking and/or back-up maneuvers provides additional feature functionality without requiring additional vehicle hardware and associated costs and complexity. 
     While the best mode has been described in detail, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. Various embodiments may have been described as providing advantages or being preferred over other embodiments and/or prior art devices in regard to one or more desired characteristics. However, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. Any embodiments described herein as being less desirable in one aspect or another to other embodiments and/or prior art devices with respect to one or more characteristics are not outside the scope of the disclosure or claims.