Abstract:
An automotive vehicle includes engine start/stop (ESS) and adaptive cruise control with stop and go functionality (ACCS&amp;G). A method of coordinating operation of the ESS and ACCS&amp;G systems is provided. The ACCS&amp;G system brings the vehicle to a stop. After a delay and satisfaction of autostop conditions, the ESS system stops the engine. Upon receipt of an input and satisfaction of start conditions, the ESS system restarts the engine. The ACCS&amp;G system then resumes control of the restarted engine.

Description:
BACKGROUND OF INVENTION 
       [0001]    The present invention relates to a method of controlling an automotive engine and in particular to a method of coordinating an engine start/stop system with an adaptive cruise control stop-and-go system. 
         [0002]    Automotive vehicle powertrains may incorporate an engine start/stop (ESS) system to improve fuel economy. The ESS system stops an internal combustion engine under specified conditions when engine torque is not required and restarts the engine when torque is again required. For example, the ESS system may stop the engine of a vehicle after a driver brakes the vehicle to a stop at a traffic light, with the vehicle transmission in drive, and then restart the engine when the driver requests torque by depressing an accelerator pedal. 
         [0003]    Automotive vehicle powertrains may also incorporate an adaptive cruise control stop-and-go (ACCS&amp;G) system. The ACCS&amp;G system in a host vehicle monitors the position of a lead vehicle ahead of the host vehicle. The ACCS&amp;G system will automatically adjust a speed of the host vehicle to maintain a specified distance (which may be a function of speed) between the host and lead vehicles. For example, the ACCS&amp;G system in a host vehicle may command the host vehicle to stop when the lead vehicle has stopped and the specified distance (for that speed) between the host and lead vehicles can no longer be safely maintained. 
         [0004]    However, because the ESS and ACCS&amp;G systems both control operation of the powertrain, there is the possibility of conflicting commands. For example, for the vehicle having both ACCS&amp;G and ESS systems, the ACCS&amp;G system may make a torque request while the ESS system is executing an engine stop routine. This may occur when the host vehicle follows the lead vehicle to a stop, but almost immediately after the host vehicle has stopped, the lead vehicle resumes moving. Typically, the engine stop routine is completed before an engine start routine may be executed so that the vehicle may move. This may result in a delay before the torque request from the ACCS&amp;G system is executed. The delay may be problematic when the torque request is a result of the lead vehicle moving. The host vehicle remains stationary until the ESS system has restarted the engine, and while the host vehicle is stationary, the lead vehicle moves further and further from the host vehicle. This delay may reduce the drivability of the host vehicle having both ESS and ACCS&amp;G systems. 
       SUMMARY OF INVENTION 
       [0005]    An embodiment contemplates a method of controlling an engine. A first system brings a vehicle propelled by the engine to a stop while a second system is active. The second system, after a delay, stops the engine of the stationary vehicle upon detection of a status of the first system. The second system restarts the stopped engine upon receipt of an input. The first system resumes propelling the vehicle using the restarted engine. 
         [0006]    Another embodiment contemplates a method of controlling an engine. A first system automatically brings a vehicle propelled by the engine to a stop while a second system is active. The second system, after a delay, stops the engine of the stationary vehicle upon detection of a status of the first system. The first system detects an input and the second system controls the engine per the input. 
         [0007]    Another embodiment contemplates a method of controlling an engine. A driver of a vehicle activates a brake to bring the vehicle to a stop while a first system is deactivated and a second system is activated, the vehicle being propelled by the engine. The second system, after a delay, stops the engine while the vehicle is stationary and the first system remains deactivated. The driver activates the first system while the vehicle is stationary, the engine stopped, and the brake activated. The driver releases the brake while the first and second systems are activated and the engine stopped. The first system holds the vehicle stationary while the second system keeps the engine stopped. 
         [0008]    An advantage of an embodiment is that the ESS and ACCS&amp;G systems are coordinated. This will improve driveablity of the vehicle when the ACCS&amp;G and ESS systems commands may conflict. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a schematic view of an automotive vehicle. 
           [0010]      FIG. 2  is a flowchart for controlling an automotive powertrain. 
           [0011]      FIG. 3   a  is a flowchart for controlling an automotive powertrain. 
           [0012]      FIG. 3   b  is a flowchart for controlling an automotive powertrain. 
           [0013]      FIG. 4  is a flowchart for controlling an automotive powertrain. 
           [0014]      FIG. 5  is a flowchart for controlling an automotive powertrain. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  schematically illustrates an automotive vehicle  10  having a powertrain  12 . The powertrain  12  may be a typical automotive powertrain as understood by one skilled in the art. As illustrated, the powertrain  12  has an internal combustion engine  14 . One skilled in the art will understand that the powertrain  12  may have the engine  14  only or the engine  14  in conjunction with an electric machine. Alternatively, the powertrain  12  may have an electrical machine in lieu of the engine  14 . As illustrated, the powertrain  12  has a rear wheel drive configuration. One skilled in the art will understand that the powertrain  12  may have a front wheel drive or an all wheel drive configuration. Operation of the powertrain  12  is controlled by a powertrain controller  16 . 
         [0016]    The powertrain  12  includes an engine start/stop (ESS) controller  18 . The ESS controller  18  coordinates a typical ESS system as understood by one skilled in the art. The ESS controller  18  may be separate from or integrated with the powertrain controller  16 , and each may be made up of various combinations of hardware and software as is known to those skilled in the art. The term “system” as used herein means a mechanical and/or electrical assembly activated by a human to automatically carry out a procedure to a desired result. The ESS controller  18  monitors the vehicle  10  and, when predetermined conditions are present, signals the powertrain controller  16  to start or stop the engine  14 . For example, the ESS controller  18  may detect that the vehicle  10  has been stationary for a predetermined period of time, in which case the ESS controller  18  will signal the powertrain controller  16  to execute an engine stop routine. For example, the ESS controller  18  may detect that the vehicle  10  is stationary, the engine  14  was stopped by the ESS system, and a torque request is being made, in which case the ESS controller  18  will signal the powertrain controller  16  to execute an engine start routine. For example, a driver of the vehicle  10  may press an accelerator pedal while the ESS system has stopped the engine  14 . Pressing the accelerator pedal will make the ESS controller  18  signal the powertrain controller  16  to execute the engine start routine. The ESS system may be activated and deactivated by the driver, another system of the vehicle  10 , or by the ESS controller  18  detecting a predetermined condition. 
         [0017]    The powertrain  12  additionally includes an adaptive cruise control (ACC) controller  20 . The ACC controller  20  may be separate from or integrated with the powertrain controller  16 , and each may be made up of various combinations of hardware and software as is known to those skilled in the art. The ACC controller  20  coordinates a typical ACC system as understood by one skilled in the art. The ACC controller  20  uses a sensor  22  to detect a lead vehicle  24 . The sensor  22  may be a radar-based sensor, a laser-based sensor, or another sensor type known to those skilled in the art. The sensor measures a lead distance from the vehicle  10  to the lead vehicle  24  and communicates with the ACC controller  20 . The ACC controller  20  uses the lead distance, parameters of the vehicle  10  (such as a current speed of the vehicle  10 ), and preset limits to calculate whether to signal the powertrain controller  16  to increase or decrease torque produced by the powertrain  12  so that the lead distance may be maintained in accordance with a predetermined distance, which may be a function of vehicle speed. The ACC system may be activated and deactivated by the vehicle driver, another system of the vehicle  10 , or by the ACC controller  20  detecting a predetermined condition. For example, the driver may deactivate the ACC system by pressing a “CANCEL” button or a brake pedal  25 . 
         [0018]    The ACC system includes stop-and-go functionality. Hereinafter, the term “ACCS&amp;G” shall mean an ACC system that includes stop-and-go functionality. When the ACCS&amp;G system is activated and the vehicle  10  is following the lead vehicle  24 , if the vehicle  24  stops, the vehicle  10  will slow and stop behind the lead vehicle  24 . While ACCS&amp;G is slowing the vehicle  10  to a stop, the lead distance may be reduced less than the predetermined distance so that the vehicle  10  comes to a stop at a typical distance behind the lead vehicle  24 . When the lead vehicle resumes moving, ACCS&amp;G will start the vehicle  10  moving again. ACCS&amp;G will accelerate the vehicle  10  such that the lead distance is restored to the predetermined distance. 
         [0019]    The vehicle  10  includes a brake system  26  that is monitored by ESS controller  18 . The brake system  26  is a typical automotive brake system as understood by one skilled in the art. As illustrated, the brake system  26  is schematic and shown only for rear wheels of the vehicle  10 . As understood by one skilled in the art, the brake system  26  may also be used at other wheels of the vehicle  10 . 
         [0020]      FIG. 2  will now be discussed with reference to  FIG. 1 .  FIG. 2  is a flowchart illustrating a first coordinated operation  100  of the powertrain controller  16 , the ESS controller  18 , and the ACC controller  20  to stop the engine  14 . 
         [0021]    The ESS system is active in a step  102  and the ACCS&amp;G system is active in a step  104 . In a step  106 , the vehicle  10 , using the ACCS&amp;G system, is following a lead vehicle  24 . In a step  108 , the lead vehicle has stopped and in a step  110 , the vehicle  10 , using the ACCS&amp;G system, has slowed to a stop as well. 
         [0022]    In a step  112 , a time duration is measured starting when the ACCS&amp;G system stops the vehicle  10  in the step  110 . The time duration must exceed a minimum duration for the ESS system to command the engine  14  to stop. The minimum duration allows the vehicle  10  to quickly resume movement, for example, if the lead vehicle  24  makes only a brief stop for less than the minimum duration or the driver overrides the ACCS&amp;G system by requesting acceleration. For example, the minimum duration may be 3 seconds. 
         [0023]    If the lead vehicle  24  is not stopped for the minimum duration, then the ACC controller  20  directs the vehicle  10  to resume following the lead vehicle  24  in a step  114 . If the lead vehicle  24  is stopped for at least the minimum duration, then the ACC controller  20  signals the ESS controller  18  and, in a step  116 , the ESS controller  18  verifies if all autostop conditions have been satisfied. The autostop conditions include that the ACCS&amp;G system is activated, not requesting acceleration, and is requesting braking to stop the vehicle  10  and that the vehicle  10  is being held stationary by the brake system  26 . If the autostop conditions are not satisfied, then the step  112  is repeated. If the autostop conditions are satisfied, then in a step  118  the ESS controller  18  commands the powertrain controller  16  to stop the engine  14 . In a step  120 , the engine  14  has stopped. 
         [0024]      FIG. 3   a  and  FIG. 3   b  will now be discussed with reference to  FIG. 1 .  FIG. 3   a  and  FIG. 3   b  are a flowchart illustrating a second coordinated operation  200  of the powertrain controller  16 , the ESS controller  18 , and the ACC controller  20  to start the engine  14 . The second coordinated operation  200  may be used after the engine  14  has been stopped using the first coordinated operation  100 . 
         [0025]    In a step  202  the vehicle  10  is stopped, in a step  204  the ESS system has stopped the engine  14 , and in a step  206  the ACCS&amp;G system is active. In a step  208 , the ACC controller  20  determines if the lead vehicle  24  is stationary. If the lead vehicle  24  is stationary, then in a step  210 , the powertrain controller  16  determines if the accelerator pedal has been pressed. 
         [0026]    If the accelerator pedal has been pressed, then, in a step  212 , the ESS controller  18  determines if at least one restart condition has been satisfied. The restart conditions include the ACCS&amp;G system requesting acceleration and not requesting braking to stop the vehicle  10 , and the vehicle  10  not being held stationary by the brake system  26 . If no restart condition has been met, then the step  212  is repeated. If at least one restart condition is satisfied, then in a step  214  the ESS controller  18  commands the powertrain controller  16  to start the engine  14 . In a step  216  the engine  14  is started and in a step  218  the vehicle  10  creeps forward. 
         [0027]    If the accelerator pedal has not been pressed, then the ACC controller  20  determines if the lead vehicle is still stationary in the step  208 . If, in the step  208 , the lead vehicle  24  is not stationary, then in a step  220  the ACC controller  20  will determine if the lead vehicle  24  has moved. If the vehicle has moved in the step  220 , then, in a step  222 , the ACC controller  20  determines if a “RESUME” button has been pressed by the driver. 
         [0028]    If the “RESUME” button has been pressed in the step  222 , then in a step  224  the ESS controller  18  will determine if at least one of the restart conditions has been met. If no restart condition has been met, then the step  224  is repeated. If at least one restart condition is satisfied, then in a step  226  the ESS controller  18  commands the powertrain controller  16  to start the engine  14 . In a step  228  the engine  14  is started and in a step  230  the vehicle  10  accelerates slowly before the ACCS&amp;G system resumes control of the powertrain  12 . 
         [0029]    If, in the step  222 , the “RESUME” button has not been pressed, then in a step  232  the powertrain controller  16  determines if the accelerator pedal has been pressed. If the accelerator pedal has been pressed, then in a step  234  the ESS controller  18  will determine if at least one of the restart conditions has been met. If no restart condition has been met, then the step  234  is repeated. If at least one restart condition is satisfied, then in a step  236  the ESS controller  18  commands the powertrain controller  16  to start the engine  14 . In a step  238  the engine  14  is started and in a step  240  the vehicle  10  accelerates in accordance with the accelerator press by the driver. Once the driver ends the accelerator press, then the ACCS&amp;G system resumes control of the powertrain  12  in a step  242 . 
         [0030]    If, in the step  232 , the accelerator pedal has not been pressed, then in a step  244  the ESS controller  18  will determine if at least one of the restart conditions has been met. If no restart condition has been met, then the step  244  is repeated. If at least one restart condition is satisfied, then, in a step  246 , the ESS controller  18  commands the powertrain controller  16  to start the engine  14 . In a step  248  the engine  14  is started and in a step  250  ACCS&amp;G is resumed. 
         [0031]      FIG. 4  will now be discussed with reference to  FIG. 1 .  FIG. 4  is a flowchart illustrating a third coordinated operation  300  of the powertrain controller  16 , the ESS controller  18 , and the ACC controller  20  when the brake pedal  25  is pressed after the engine  14  has been stopped by the ESS system. The third coordinated operation  300  may be used after the engine  14  has been stopped using the first coordinated operation  100 . 
         [0032]    In a step  302  the vehicle  10  is stopped, in a step  304  the ESS system has stopped the engine  14 , and in a step  306  the ACCS&amp;G system is active. In a step  308 , the ACC controller  20  determines if the brake pedal  25  is pressed. If the brake pedal  25  is pressed, then in a step  310  the ACCS&amp;G system is deactivated and in a step  312  the engine  14  remains stopped. 
         [0033]    If the brake pedal  25  is not pressed, then in a step  314  the ACC controller  20  determines if the ACCS&amp;G system was deactivated by a means other than by pressing the brake pedal. For example, the ACCS&amp;G system may be deactivated when an automatic transmission is not in drive or low gear, the driver applies an electric parking brake, the ACCS&amp;G system times out (for example, after  3  minutes), or the driver deactivates the ACCS&amp;G system with a command input (for example, pressing an “ON/OFF” button). If the ACCS&amp;G system was not deactivated in the step  314  by a means other than pressing the brake pedal, then the step  314  is repeated. If the ACCS&amp;G system was deactivated in the step  314  by a means other than pressing the brake pedal, then in a step  316  the ESS controller  18  will determine if at least one of the restart conditions has been met. If no restart condition has been met, then the step  316  is repeated. If at least one restart condition is satisfied, then in a step  318  the ESS controller  18  commands the powertrain controller  16  to start the engine  14 . In a step  320  the engine is started. 
         [0034]      FIG. 5  will now be discussed with reference to  FIG. 1 .  FIG. 5  is a flowchart illustrating a fourth coordinated operation  400  of the powertrain controller  16 , the ESS controller  18 , and the ACC controller  20  when the ACCS&amp;G system is activated while the vehicle  10  has been stopped. 
         [0035]    In a step  402  the ESS system is active, in a step  404  the ACCS&amp;G system is inactive, in a step  406  the driver has applied the brake system  26 , and in a step  408  the vehicle  10  has stopped. In a step  410 , a time period is measured from when the vehicle  10  has stopped in the step  408 . If the time period does not exceed a minimum duration, then the ESS system is inhibited from stopping the engine  14  in a step  412  and the step  410  is repeated. For example, the minimum duration may be  3  seconds. If the time period exceeds the minimum duration, then in a step  414  the ESS controller  18  commands the ACC controller  20  to stop the engine  14 . In a step  416  the engine is stopped and in a step  418  the driver activates the ACCS&amp;G system. In a step  420  the driver releases the brake pedal and in a step  422  the vehicle  10  is held stationary by the ACC controller  20 . 
         [0036]    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.