Patent Publication Number: US-2017349167-A1

Title: Real-time driver-controlled dynamic vehicle balance control system

Description:
TECHNICAL FIELD 
     The present disclosure relates to automotive vehicles, and more particularly to automotive vehicle having at least one active system for affecting vehicle understeer. 
     INTRODUCTION 
     In an automotive vehicle, understeer and oversteer refer to differences between a yaw rate commanded at the steering wheel and an actual yaw rate of the vehicle. Understeer refers to the phenomenon when the actual yaw rate of the vehicle is less than that commanded at the steering wheel, while oversteer refers to the phenomenon when the actual yaw rate of the vehicle is greater than that commanded at the steering wheel. Various vehicle systems, including suspension and vehicle aerodynamic surfaces, may contribute to understeer or oversteer. 
     SUMMARY 
     An automotive vehicle according to the present disclosure includes a steering system and a steering wheel configured to control the steering system. The vehicle additionally includes a dynamic vehicle balance control system configured to modify a yaw rate of the vehicle during a drive cycle to modify understeer behavior. The vehicle also includes a sensor configured to detect an operator force applied to the steering wheel. The vehicle further includes a controller. The controller is configured to, in response to a detected operator force applied to the steering wheel, command the dynamic vehicle balance control system to modify the yaw rate of the vehicle. 
     According to various embodiments, the sensor includes a pressure transducer arranged to detect an operator translational force applied to the steering wheel or a pressure transducer arranged to detect an operator pivot moment applied to the steering wheel. 
     According to an exemplary embodiment, the steering wheel is configured to move a calibrated distance in response to an operator force applied to the steering wheel. 
     According to an exemplary embodiment, the dynamic vehicle balance control system includes an active aerodynamic control member having a first position and a second position. In such an embodiment, commanding the dynamic vehicle balance control system to modify the yaw rate of the vehicle includes commanding the aerodynamic control member to move from the first position to the second position to adjust a pitch moment of the vehicle. 
     According to another exemplary embodiment, the dynamic vehicle balance control system includes an electronic limited slip differential. In such an embodiment, commanding the dynamic vehicle balance control system to modify the yaw rate of the vehicle includes commanding the electronic limited slip differential to unevenly distribute torque to vehicle wheels. 
     According to yet another exemplary embodiment, the dynamic vehicle balance control system includes a first dynamic vehicle balance control subsystem and a second dynamic vehicle balance control subsystem. In such an embodiment, the controller is configured to, in response to the detected operator force applied to the steering wheel and vehicle speed being below a threshold, command the first dynamic vehicle balance control subsystem to modify the yaw rate of the vehicle. The controller is further configured to, in response to the detected operator force applied to the steering wheel and vehicle speed not being below the threshold, command the second dynamic vehicle balance control subsystem to modify the yaw rate of the vehicle. 
     A method of controlling an automotive vehicle according to the present disclosure includes providing an automotive vehicle with at least one dynamic vehicle balance control system. The method additionally includes controlling the balance control system according to a default schedule during a drive cycle. The method further includes, in response to an operator input, controlling the dynamic vehicle balance control system to modify a vehicle yaw rate to increase or decrease an understeer resulting from the default schedule. 
     According to an exemplary embodiment, the dynamic vehicle balance control system includes an active aero system. In such an embodiment, controlling the dynamic vehicle balance control system to modify a vehicle yaw rate includes controlling an aerodynamic member of the active aero system. 
     According to another exemplary embodiment, the dynamic vehicle balance control system includes an electronic limited slip differential. In such an embodiment, controlling the dynamic vehicle balance control system to modify a vehicle yaw rate includes controlling a clutch pressure of the electronic limited slip differential. 
     According to various additional embodiments, the dynamic vehicle balance control system includes an active drivetrain device, an active suspension device, an active torque vectoring device, am active rear steering device, an active toe control device, an active camber control device, or an active aero device. 
     According to various exemplary embodiments, the operator input includes an operator translational force applied to a vehicle steering wheel or an operator pivoting moment applied to a vehicle steering wheel. 
     According to a further embodiment, the method additionally includes storing the operator input and a location at which the operator input was received in non-transient data memory storage. In response to the vehicle being at the location at which the operator was received during a subsequent trip, the dynamic vehicle balance control system is controlled to modify the vehicle yaw rate in the absence of operator input. 
     A system for controlling an automotive vehicle according to the present disclosure includes a dynamic vehicle balance control system having a default control schedule. The system additionally includes at least one sensor configured to detect a first operator input requesting an increase in understeer and to detect a second operator input requesting a decrease in understeer. The system further includes a controller. The controller is configured to, in response to the first operator input, control the dynamic vehicle balance control system to increase understeer relative to the default control schedule. The controller is also configured to, in response to the second operator input, control the dynamic vehicle balance control system to decrease understeer relative to the default control schedule. 
     According to an exemplary embodiment, the system additionally includes a steering wheel. In such an embodiment, the sensor may include a pressure transducer arranged to detect a translational force applied to the steering wheel and/or a pressure sensor arranged to detect a pivoting moment applied to the steering wheel. 
     According to another exemplary embodiment, the dynamic vehicle balance control system includes an active aerodynamic control member having a first position and a second position. In such an embodiment, controlling the dynamic vehicle balance control system to increase understeer relative to the default control schedule includes controlling the aerodynamic control member to move from the first position to the second position to adjust a pitch moment of the vehicle. 
     According to an additional exemplary embodiment, the dynamic vehicle balance control system includes an electronic limited slip differential. In such an embodiment, controlling the dynamic vehicle balance control system to increase understeer relative to the default control schedule includes controlling the electronic limited slip differential decrease a pressure of the clutch. 
     According to various additional embodiments, the dynamic vehicle balance control system includes an active drivetrain device, an active suspension device, an active torque vectoring device, am active rear steering device, an active toe control device, an active camber control device, or an active aero device. 
     Embodiments according to the present disclosure provide a number of advantages. For example, systems and methods according to the present disclosure enable an operator of an automotive vehicle to modify vehicle handling characteristics, e.g. adjusting an amount of understeer, in real-time. Moreover, an operator may do so using an easily understood and operated input device, e.g. incorporated into the steering wheel. 
     The above advantage and other advantages and features of the present disclosure will be apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a vehicle according to the present disclosure; 
         FIG. 2  is a schematic representation of a vehicle according to the present disclosure; 
         FIG. 3  illustrates a first embodiment of an operator-controlled dynamic vehicle balance control interface according to the present disclosure; 
         FIG. 4  illustrates a second embodiment of an operator-controlled dynamic vehicle balance control interface according to the present disclosure; and 
         FIG. 5  is a flowchart representation of a method of controlling a vehicle according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could 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 present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Referring now to  FIGS. 1 and 2 , an automotive vehicle  10  according to the present disclosure is illustrated. The vehicle  10  includes a body  12  with a longitudinal axis  14  extending from a front portion to a rear portion, a lateral axis  16  extending from a passenger side to a driver side, and a vertical axis  18  extending orthogonal to the longitudinal axis  14  and lateral axis  16 . Rotation of the body  12  about the longitudinal axis  14  is referred to as roll, rotation of the body  12  about the lateral axis  16  is referred to as pitch, and rotation of the body  12  about the vertical axis  18  is referred to as yaw. 
     In this embodiment, the vehicle  10  is arranged as a rear-wheel-drive vehicle. It should be noted that other considered embodiments may be configured otherwise, such as front-wheel-drive or all-wheel-drive. 
     The vehicle  10  includes two front traction wheels  20  coupled to a front axle  22 . In addition, the vehicle  10  includes two rear traction wheels  24  coupled to rear half shafts  26 . An electronic limited-slip differential (eLSD)  28  is configured to distribute torque from a drive shaft  30  to the rear half shafts  26 . The eLSD  28  is configured to selectively permit a speed differential between the respective rear half shafts  26 . 
     A steering system  32  is configured to pivot the front wheels  20  to steer the vehicle. The steering system  32  is configured to pivot the front wheels  20  in response to a steering force from a steering column  34  based on an operator input to a steering wheel  36 . A pressure transducer  38  is coupled to the steering column  34 , as will be discussed in further detail below. 
     A rear wing  40  is provided at a rear portion of the body  12 . The rear wing  40  acts as an aerodynamic control member configured to generate a downforce at the rear portion of the body  12 . The rear wing  40  is carried by at least one stanchion  42 . At least one actuator  44  is provided to pivot the rear wing  40  relative to the stanchion  42  and adjust the angle of attack of the rear wing  40 . The actuator  44  is configured to pivot the rear wing  40  between at least a first position and a second position, distinct from the first position. The actuator  44  may thus adjust the downforce generated by the rear wing  40 . Because the actuator  44  may modify aerodynamic characteristics of the rear wing  40  during a drive cycle, the rear wing  40  may be referred to as an “active” aerodynamic control member. 
     The eLSD  28 , pressure transducer  38 , and actuator  44  are all in communication with or under the control of a controller  46 . The controller  46  is configured to control the eLSD  28 , actuator  44 , and optionally one or more additional systems, as will be discussed in further detail below. While depicted as a single controller in  FIG. 2 , the controller  46  may include one or more other controllers, collectively referred to as a “controller.” The controller  46  may include a microprocessor or central processing unit (CPU) in communication with various types of computer readable storage devices or media. Computer readable storage devices or media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the CPU is powered down. Computer-readable storage devices or 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, used by the controller in controlling the engine or vehicle. 
     Under certain conditions, during high speed turns the vehicle  10  may experience understeer or oversteer. Understeer refers to situations when the vehicle travels straighter than the trajectory commanded by the operator, e.g. the actual yaw rate of the vehicle is less than desired. This may occur, for example, when the front tires reach their limit of adhesion during a turn while the rear tires still maintain traction. Oversteer refers to situations when the vehicle turns more sharply than the trajectory commanded by the operator, e.g. the actual yaw rate of the vehicle is greater than desired. This may occur, for example, when the rear tires reach their limit of adhesion during a turn while the front tires still maintain traction. While oversteer is generally viewed as less advantageous, the vehicle  10  may be configured to provide a quantity of understeer. 
     Various vehicle systems may be controlled to affect understeer behavior of the vehicle  10 . As an example, the rear wing  40  generates a downforce at the rear portion of the body  12 . The downforce creates a pitch moment about the center of gravity of the body  12 . By controlling the actuator  44  to adjust the angle of attack of the rear wing  40 , the magnitude of the downforce and, in turn, the magnitude of the pitch moment may be adjusted. By adjusting the pitch moment, the relative loading of the front tires  20  and rear tires  24 , and likewise the relative lateral force of the front tires  20  and rear tires  24  during a turn, may be modified. By adjusting the relative lateral force of the front tires  20  and rear tires  24 , the controller  46  may affect whether and when the front tires  20  and rear tires  24  reach their limit of adhesion during a turn and, in turn, affect the understeer behavior of the vehicle  10 . 
     In other considered embodiments, the rear wing  40  may be part of an active aerodynamic control system, or “active aero” system. In such embodiments, the active aero system may include one or more additional active aerodynamic control members provided at other portions of the vehicle. Any additional active aerodynamic control members may likewise be controlled to adjust vehicle pitch moment or otherwise influence understeer behavior of the vehicle  10 . 
     As another example, the eLSD  28  may be controlled to increase or decrease slippage, e.g. to adjust the allowable speed differential between the respective rear half shafts  26 . Generally, a reduction in slippage corresponds to an increase in understeer. Thus, the controller  46  may control the eLSD  28  to affect the understeer behavior of the vehicle  10 . 
     In other considered embodiments, other systems may also be controlled to affect understeer behavior of the vehicle  10  in real-time, e.g. during a drive cycle in response to a command from a controller. Such systems may include other active drivetrain devices, active suspension devices such as active springs or active MR dampers, active torque vectoring, active rear steering, active toe control, active camber control, active aero devices, and/or other active pitch control or roll control devices capable of modifying vehicle yaw rate during a drive cycle. 
     Collectively, the actuator  44 , eLSD  28 , and other systems for affecting the understeer behavior of the vehicle  10  in real-time may be referred to as dynamic vehicle balance control systems. 
     Such systems, including the actuator  44 , eLSD  28 , and other devices, are generally controlled according to one or more schedules, e.g. as a function of vehicle speed, acceleration, traction, and/or other parameters. The schedules are configured to provide consistent behavior for a given set of operating parameters. In an exemplary embodiment, the schedules are provided in non-transient data memory accessible by the controller  46 . 
     However, different operators have different expectations and/or preferences regarding vehicle dynamic response during high-speed turns. Some operators may prefer a relatively high amount of understeer on corner entry, while other operators may prefer a relatively low amount of understeer. The schedule is generally tuned toward an average driver preference, which may result in decreased satisfaction for drivers who prefer a greater or lesser amount of understeer on corner entry. 
     Referring now to  FIG. 3 , a first embodiment of an operator-controlled dynamic vehicle balance control interface according to the present disclosure is illustrated. The steering wheel  36  is configured to turn about a central axis  48  in response to an operator input, similar to known steering wheels. In addition, the steering wheel  36  is provided with the pressure transducer  38  coupled to the steering column  34 . The pressure transducer  38  is configured to detect a force F applied to the steering wheel  36  in a direction generally parallel the central axis  48  and provide a signal corresponding to a magnitude of the force F. 
     In an exemplary embodiment, the steering wheel  36  is configured to translate parallel to the central axis  48  under the force F. In an exemplary embodiment, the allowable distance of translation and resistance to translation are calibrated to provide a desired force feedback to an operator. In addition, a so-called “dead zone” may be provided, such that small applications of force to the steering wheel  36  do not result in a modification to understeer behavior. Understeer behavior is only modified in response to a force application exceeding a threshold force. 
     In response to the signal from the pressure transducer  38  corresponding to the magnitude of the force F, the controller  46  is configured to control at least one dynamic vehicle balance control system to modify understeer behavior of the vehicle. 
     In an exemplary embodiment, in response to a force F corresponding to an operator pushing on the steering wheel  36 , the controller  46  controls at least one dynamic vehicle balance control system to decrease understeer, while in response to a force F corresponding to an operator pulling on the steering wheel  36 , the controller  46  controls at least one dynamic vehicle balance control system to increase understeer. Of course, other configurations may be provided. 
     In an exemplary embodiment, controlling a dynamic vehicle balance control system to increase or decrease understeer includes controlling the dynamic vehicle balance control system to deviate from the base schedule. The deviation may be a scalar value corresponding to the magnitude of the force F. Thus, a higher magnitude force F will result in a larger change in understeer behavior. 
     In various embodiments, a single dynamic vehicle balance control system may be controlled, or multiple dynamic vehicle balance control systems or subsystems may be coordinated together to affect understeer. In an exemplary embodiment, a first dynamic vehicle balance control system may be controlled to affect understeer in response to vehicle speed being below a first threshold, and a second dynamic vehicle balance control system may be controlled to affect understeer in response to vehicle speed being above a first threshold. 
     In addition to providing real-time understeer control, operator inputs received by the pressure transducer  38  may be recorded in non-transient data storage and processed for subsequent use. 
     As an example, the controller  46  may be configured to activate a track learning mode in response to an operator input. With the track learning mode active, an operator may drive the vehicle  10  around a track while providing inputs to the steering wheel  36  indicating desired understeer behavior. The inputs are stored, along with a location at which the input was received, to “learn” the operator&#39;s preferences for the track. During subsequent laps around the same track after the operator&#39;s preferences are learned, the controller  46  may automatically control the at least one dynamic vehicle balance control system to provide the desired understeer behavior, without requiring the operator to provide inputs to the steering wheel  36 . 
     As another example, operator inputs to the steering wheel  36  indicating desired understeer behavior may be communicated to a remote processing location, e.g. via cellular data transmission, enabling subsequent analysis to aid a manufacturer in chassis tuning. In such embodiments, operator opt-in may be required before communicating the operator inputs to the remote processing location. 
     Variations on the above system are considered within the scope of the present disclosure. Referring now to  FIG. 4 , an alternative embodiment of an operator-controlled dynamic vehicle balance control interface according to the present disclosure is illustrated. A steering wheel  36 ′ is configured to turn about a central axis  48 ′ in response to an operator input. In addition, the steering wheel  36 ′ is provided with a pressure transducer  38 ′ coupled to a steering column  34 ′. The pressure transducer  38 ′ is configured to detect a pivoting moment M applied to the steering wheel  36 ′ in a direction generally perpendicular the central axis  48 ′ and provide a signal corresponding to a magnitude of the pivoting moment M. Understeer behavior may be adjusted based on the signal in a generally similar manner as discussed above with respect to  FIG. 3 . 
     Other considered embodiments include, but are not limited to, providing a throttle grip or actuatable paddles on a vehicle steering wheel. These or other similar operator interfaces may be used to signal, in real-time, an operator&#39;s desire for increased or decreased understeer. 
     Referring now to  FIG. 5 , a method of controlling a vehicle according to the present disclosure is illustrated in flowchart form. The method begins at block  60 . A vehicle is provided with at least one dynamic vehicle balance control system, as illustrated at block  62 . The dynamic vehicle balance control system may include an active aero system and/or an eLSD, as illustrated at block  64 . The dynamic vehicle balance control system is operated according to a default schedule during a drive cycle, as illustrated at block  66 . An operator input is received, as illustrated at block  68 . The operator input may include a translational force or pivoting moment applied to a steering wheel, as illustrated at block  70 . In response to the operator input, the dynamic vehicle balance control system is controlled to modify a vehicle yaw rate, e.g. to increase or decrease an understeer resulting from the default schedule, as illustrated at block  72 . The operator input may be stored for subsequent processing, as illustrated at block  74 . The method ends at block  76 . 
     As may be seen, systems and methods according to the present disclosure enable an operator of an automotive vehicle to modify vehicle handling characteristics, e.g. adjusting an amount of understeer, in real-time. Moreover, an operator my do so using an easily understood and operated input device, e.g. incorporated into the steering wheel. 
     The processes, methods, or algorithms disclosed herein can be deliverable to/implemented by a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms can be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms can be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. Such example devices may be on-board as part of a vehicle computing system or be located off-board and conduct remote communication with devices on one or more vehicles. 
     As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.