Abstract:
A vehicle and a method of controlling a dynamometer mode operation of a vehicle that includes requesting the dynamometer mode; monitoring for at least one non-dynamometer vehicle operating condition; if at least one of the non-dynamometer vehicle operating conditions is detected, prohibiting dynamometer mode; and if none of the non-dynamometer vehicle operating conditions is detected, operating the vehicle in dynamometer mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application 61/660,667, filed Jun. 15, 2012, which is incorporated herein by reference. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to a method of vehicle operation and more particularly to vehicle operating strategies for use with chassis dynamometer testing. 
     During vehicle development, vehicles may be tested on chassis dynamometers, where the powered wheels are mounted on some type of roller system to allow the vehicle operations to be tested while the vehicle is stationary. Today&#39;s modern vehicles have many different computer controlled systems that, under normal operating conditions (normal mode), monitor and automatically change vehicle operation based on the monitored vehicle systems. There may be difficulty testing vehicles on a single roll chassis dynamometer when the vehicle controllers are set to operate under normal operating conditions because of the operation of anti-lock brake and other systems which will set malfunction indications when all four wheels are not turning. For hybrid vehicles in particular, such operation faults may inhibit proper testing of vehicle functions such as stop-start, regenerative brakes and other hybrid vehicle functions making the dynamometer test results non-representative of the emission and fuel economy of the vehicle under normal use on the road. 
     Accordingly, while operating a vehicle on a chassis dynamometer, vehicle operation algorithms may be employed to control the vehicle that are not active when the vehicle is operating under normal driving conditions. These dynamometer operation algorithms (dynamometer mode operation) enable the particular testing to be accomplished on the dynamometer. The dynamometer operation algorithms may also require additional component redundancy or complex algorithms to determine when to start and when to exit execution of the dynamometer control mode algorithms, which may support safe operation of the vehicle on the dynamometer and also assure the dynamometer mode is not activated when the vehicle is not on a dynamometer. 
     SUMMARY OF INVENTION 
     An embodiment contemplates a method of controlling a dynamometer mode operation of a vehicle comprising: requesting the dynamometer mode; monitoring for at least one non-dynamometer vehicle operating condition; if at least one of the non-dynamometer vehicle operating conditions is detected, prohibiting dynamometer mode; and if none of the non-dynamometer vehicle operating conditions is detected, operating the vehicle in dynamometer mode. 
     An embodiment contemplates a vehicle having a dynamometer operation algorithm to operate in a dynamometer mode comprising: a sensing system configured to detect a non-dynamometer vehicle operating condition; and a controller configured to monitor the sensing system for the non-dynamometer vehicle operating condition while the vehicle is operating in the dynamometer mode and automatically switching out of the dynamometer mode when at least one of the non-dynamometer vehicle operating conditions is detected. 
     An advantage of an embodiment is that simple detection of non-dynamometer vehicle operation is detected to assure that dynamometer operation algorithms are used while undergoing dynamometer tests, but are not employed when the vehicle is not undergoing dynamometer testing. 
     An additional advantage of an embodiment is that the dynamometer operation monitoring makes use of information that is already readily available on the vehicle, that is the sensors and related signal feedback that already exists for use under normal vehicle operating conditions (i.e., real world vehicle operation). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of a front wheel drive vehicle mounted in a chassis dynamometer. 
         FIG. 2  is a schematic view of a rear wheel drive vehicle mounted in a chassis dynamometer. 
         FIG. 3  is a schematic view of a vehicle and systems and sensors that may be employed on the vehicle. 
         FIG. 4  is a flow chart illustrating a method of operating the vehicle. 
         FIG. 5  is a flow chart illustrating monitoring and detecting potential non-dynamometer operating conditions for the vehicle. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a front wheel drive vehicle  20  with the front wheels  22  mounted on rollers  24  of a chassis dynamometer  26  and rear wheels  23  that are non-rolling during dynamometer testing. The vehicle  20  may be an automotive vehicle, or may be a truck, tractor, military vehicle, or other type of wheeled vehicle that may be tested on a dynamometer  26 . 
       FIG. 2  shows a rear wheel drive vehicle  28  with the rear wheels  30  mounted on rollers  32  of a chassis dynamometer  34  and front wheels  33  that are non-rolling wheels during dynamometer testing. 
     In addition, the dynamometer may be one that has rollers to allow for all wheel (four wheel) drive—that is, a dynamometer having two sets of rollers, one set of rollers  24  for the front wheels and one set of rollers  32  for the rear wheels. This may be similar to a combination of the dynamometers shown in  FIGS. 1 and 2 . Dynamometers that allow for all wheel (four wheel) drive are known to those skilled in the art and will not be discussed further herein. 
       FIG. 3  illustrates the vehicle  20  (or  28 ) and the systems that may be employed to determine if dynamometer operation algorithms may be executed (dynamometer mode) or if the dynamometer operation algorithms will be exited when conditions are not desirable for such algorithms to operate. 
     The vehicle  20  includes a steering system  40 , which may be hydraulic or electric, having a steering wheel  42  connected to a steering assembly  44  that causes turning of the front wheels  22 . The steering system  40  may include a measurement device(s), for example one or more sensor(s)  46 , that may be capable of measuring a steering wheel position/angle, an applied force/torque to the steering wheel  42 , and/or a power steering pump state (if the system is hydraulic); and/or a measurement device(s), such as one or more sensor(s)  48  that measures applied lateral force on a wheel, and/or a wheel turn (angle) position. These measurement devices  46 ,  48  may communicate with a control system  50  for the vehicle  20 . 
     The control system  50  may include, for example, an engine controller  52 , a body controller  54  and various other controllers on a vehicle, as are known to those skilled in the art. These controllers may be integrated into a single controller assembly, or may be separate, and may be made up of various combinations of electronic hardware and software as is known to those skilled in the art. 
     The control system  50  may also include an adaptive cruise control system  56 , a roll stability and/or yaw control system  58 , a global positioning system (GPS)  60 , a collision avoidance and/or radar system  62 , and/or other systems  64  that may provide vehicle orientation, location, and/or direction indication. One or more of the vehicle systems noted above, which may already be installed on a particular vehicle for use during normal mode of vehicle operation (i.e., typical real world vehicle operation), can be used to provide an indication of a non-dynamometer vehicle operating condition. 
       FIG. 4  illustrates a method of vehicle operation for automatically switching out of dynamometer mode when a non-dynamometer operating condition is detected. The method can also be used to prevent switching into a dynamometer mode when the non-dynamometer operating conditions are detected. 
     An initial request for initiation of dynamometer operation algorithms may be made by a technician preparing to conduct dynamometer tests on the vehicle, block  100 . A check is made to detect if a non-dynamometer operating condition exists, block  102 . Such a check may include, for example, detecting if the steering wheel is being used, such as detecting a steering wheel angle other than straight ahead, applied force on a portion of the steering system indicating a turning condition, lateral force applied to the wheels, a power steering pump state indicating wheel turning, and/or detection that the front wheels are turned. Since the vehicle on a dynamometer is run with the wheels facing straight ahead, any of these indicators may then be interpreted to mean that the vehicle is not mounted in or ready for dynamometer testing—i.e., the vehicle is being operated in a non-dynamometer operating condition. In such a case, the vehicle does not enter the dynamometer operating mode, block  104 . 
     Other indications of non-dynamometer operating conditions may be employed instead of or in addition to the steering indications. For example, an adaptive cruise control system, a roll stability and/or yaw control system, a GPS system, a collision avoidance and/or radar system, and/or other systems that provide vehicle orientation, location and/or direction indication may be used to detect non-dynamometer operating conditions. For example, a vehicle system that can detect movement of the vehicle or a change in orientation of the vehicle allows for detection of the vehicle not being mounted in a dynamometer since the vehicle does not move linearly or change direction/orientation while in the dynamometer. 
     If a non-dynamometer operating condition is not detected, then the vehicle enters dynamometer mode, block  106 . The typical vehicle tests that are run on a dynamometer can now be executed. These tests may be conventional and so will not be described in detail herein. While in this mode, one or more vehicle operating conditions that are indicative of a non-dynamometer operating condition are monitored while operating the vehicle in the dynamometer mode, block  108 . If one or more non-dynamometer vehicle operating conditions are detected, block  110 , then the dynamometer operating mode is exited, block  112 . 
     Otherwise, the vehicle may continue operating in the dynamometer mode while the vehicle undergoes further dynamometer testing. Once dynamometer mode is activated, it may remain active through multiple vehicle ignition cycles so long as non-dynamometer operating conditions are not detected. This allows completion of a set of driving cycles that makes up, for example, an emission or fuel economy test without having to reactivate dynamometer mode after every time the vehicle is turned off and then restarted. 
       FIG. 5  illustrates a flow chart showing examples of one or more vehicle operating conditions that may be monitored to determine if a non-dynamometer operating condition is present. One or more of these processes may be monitored as desired for a particular vehicle. That is, not all vehicles will have all of the various systems described relative to  FIG. 5 , depending upon the vehicle options. For example, employing a vehicle Global Positioning System (GPS) to detect a change in vehicle location may be desirable for detecting a non-dynamometer operating condition, but if the particular model of vehicle does not include a GPS system, then this type of monitoring cannot be employed for this model of vehicle. But one or more of the other vehicle operating conditions may be used instead for detecting a non-dynamometer operating condition. Not all of the processes relating to vehicle operating conditions shown need to be monitored, as one may select certain vehicle processes that are sufficient to determine when a non-dynamometer operating condition exists. 
     Steering usage may be monitored, block  120 . That is, one may monitor when a vehicle system detects the wheels turning, which is not part of a dynamometer test and so indicates a non-dynamometer operating condition. This steering usage monitoring may take the form of, for example, steering wheel position, applied steering torque, power steering pump state (for a hydraulic steering system), or lateral force applied to the wheels. If steering usage is detected, block  122 , then dynamometer mode vehicle operation is prohibited, block  124 . If no steering usage is detected, then dynamometer mode vehicle operation is not prohibited, block  126 . The detection of steering usage may be set at some predetermined minimal threshold that is close to straight ahead wheel orientation in order to allow for some minimal inadvertent deviation without removing the vehicle from dynamometer mode operation. 
     Non-rolling wheel movement may be monitored, block  128 . This applies to two wheel drive vehicle tests as opposed to four wheel drive dynamometer testing. In a dynamometer test for a two wheel drive vehicle, only the driven wheels are on the rollers, so the non-driven wheels moving (rolling) indicates a non-dynamometer operating condition. This monitoring may take the form of, for example, tire monitors monitoring the non-rolling wheels or tires or sensors associated with an adaptive cruise control or anti-lock brake system. If non-rolling wheel movement is detected, block  130 , then dynamometer mode vehicle operation is prohibited, block  124 . If no non-rolling wheel movement is detected, then dynamometer mode vehicle operation is not prohibited, block  126 . The detection of this wheel movement may be set at some predetermined minimal threshold that is close to no wheel movement in order to allow for some minimal inadvertent deviation without removing the vehicle from dynamometer mode operation. 
     Vehicle orientation may be monitored, block  132 . This monitoring may take the form of, for example, roll stability control or yaw control systems that can detect changes in vehicle orientation. If a change in vehicle orientation is detected, block  134 , then dynamometer mode vehicle operation is prohibited, block  124 . If change in vehicle orientation is not detected, then dynamometer mode vehicle operation is not prohibited, block  126 . Again, some predetermined minimum threshold may be used in order to allow for some minimal inadvertent change in orientation without removing the vehicle from dynamometer mode operation. 
     Vehicle location may be monitored, block  136 . This monitoring may take the form of, for example, a Global Positioning System (GPS) that can detect changes in the location of the vehicle, which is not part of a dynamometer test. If a change in vehicle location is detected, block  138 , then dynamometer mode vehicle operation is prohibited, block  124 . If a change in vehicle location is not detected, then dynamometer mode vehicle operation is not prohibited, block  126 . Again, some predetermined minimum threshold relating to changes in vehicle location may be used to allow for minimal change in location without removing the vehicle from the dynamometer mode operation. 
     The direction that a vehicle is facing may be monitored, block  140 . This monitoring may take the form of, for example, a compass that can detect changes in the direction that the vehicle is facing, which is not part of a dynamometer test. If a change in vehicle direction is detected, block  142 , then dynamometer mode vehicle operation is prohibited, block  124 . If change in vehicle direction is not detected, then dynamometer mode vehicle operation is not prohibited, block  126 . Again, some predetermined minimum threshold relating to changes in vehicle direction may be used to allow for minimal change in direction without removing the vehicle from the dynamometer mode of operation. 
     If all vehicle operating conditions that are being monitored (steering usage, non-rolling wheel movement, vehicle orientation, vehicle location, and/or vehicle direction) indicate that dynamometer mode vehicle operation is not prohibited, then dynamometer mode vehicle operation is allowed, block  126 . But, if any of these vehicle operating conditions that are being monitored indicate non-dynamometer mode vehicle operation, then the dynamometer mode vehicle operation is prohibited. If prohibited, the vehicle may then produce a visual and/or audio signal indicating to the vehicle operator that the vehicle will not operate in dynamometer mode at the present time. Such a signal may include an indication of the reason why the mode cannot be entered. 
     Other basic vehicle operating conditions may also be used to determine when a vehicle is allowed to switch from normal vehicle operating mode to dynamometer mode. For example, such a switch to dynamometer mode may require that the vehicle transmission is in park or neutral, that the wheel speed for all wheels is close to or at zero, and/or the engine is not currently running. 
     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.