Enhanced active brake control system functionality through system integration with adaptive cruise control

A control system for controlling braking and ACC functions of a vehicle includes a braking algorithm. A first signal processor receives input signals from at least one sensor and transmits transfer signals to the braking algorithm. The control system also includes an ACC algorithm. A second signal processor receives input signals from at least one sensor and transmits transfer signals to the ACC algorithm. Transfer signals are generated by the braking algorithm and transmitted to the ACC algorithm. Transfer signals are generated by the ACC algorithm and transmitted to the braking algorithm. Output signals are generated by the braking algorithm and transmitted to a hydraulic control unit to control vehicular braking. Output signals are generated by the ACC algorithm and transmitted to ACC actuators.

BACKGROUND OF THE INVENTION
 This invention relates in general to electronically-controlled vehicular
 braking and suspension systems. In particular, this invention is concerned
 with vehicular control systems that integrate braking and ACC functions.
 Electronically-controlled vehicular braking systems can include anti-lock
 braking (ABS), traction control (TC), and vehicle stability control (VSC)
 functions. In such braking systems, sensors deliver input signals to an
 electronic control unit (ECU). The ECU sends output signals to
 electrically activated devices to apply, hold, and dump (relieve) pressure
 at wheel brakes of a vehicle. Oftentimes, electrically activated valves
 and pumps are used to control fluid pressure at the wheel brakes. Such
 valves and pumps can be mounted in a hydraulic control unit (HCU). The
 valves can include two-state (on/off or off/on) solenoid valves and
 proportional valves.
 SUMMARY OF THE INVENTION
 This invention relates to electronically-controlled vehicular systems that
 integrate braking and ACC functions. Braking functions can include
 anti-lock braking, traction control, and vehicle stability control. An
 integrated control system according to this invention receives input
 signals, calculates a desired response with braking and ACC algorithms,
 and directs devices to perform the desired functions.
 In a preferred embodiment, a control system for controlling braking and ACC
 functions of a vehicle includes a braking algorithm. A first signal
 processor receives input signals from at least one sensor and transmits
 transfer signals to the braking algorithm. The control system also
 includes an ACC algorithm. A second signal processor receives input
 signals from at least one sensor and transmits transfer signals to the ACC
 algorithm. Transfer signals are generated by the braking algorithm and
 transmitted to the ACC algorithm. Transfer signals are generated by the
 ACC algorithm and transmitted to the braking algorithm. Output signals are
 generated by the braking algorithm and transmitted to a hydraulic control
 unit to control vehicular braking. Output signals are generated by the ACC
 algorithm and transmitted to an ACC actuator.
 In other embodiments of an integrated control system, only the braking
 algorithm transfers signals to the ACC algorithm. In yet other
 embodiments, only the ACC algorithm transfers signals to the braking
 algorithm.
 The following defines the three primary points of the invention that are
 considered to be new:
 ACC system provides vehicle ground speed information to VSC system for
 enhanced active braking control.
 Communication between the ACC and VSC systems provides a means for
 modifying the ACC system settings due to potential adverse road
 conditions. ACC actuation may activate either ABS or TCS requiring either
 an increase in headway distance or less aggressive acceleration or
 deactivation. If YSC activates during ACC operation, then the ACC system
 settings should also be modified to take into account the potential for
 unsafe operating conditions.
 Vehicle side slip estimation for YSC can be enhanced by using the ACC
 vehicle speed measurement and vehicle yaw rate sensor information.
 These three main points improve over the existing products because
 currently the two systems, ACC and VSC, operate independently even though
 the potential exists for the ACC system to activate either ABS or TCS.
 With the two systems communicating with one another, information about
 vehicle stability or operating condition can be shared in order to provide
 a safer system.
 Various objects and advantages of this invention will become apparent to
 those skilled in the art from the following detailed description of the
 preferred embodiment, when read in light of the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A first embodiment of a vehicular control system according to the present
 invention is indicated generally in FIG. 1. The control system is
 particularly adapted to control fluid pressure in an
 electronically-controlled vehicular braking system and an
 electronically-controlled ACC system. The braking system can include
 anti-lock braking, traction control, and vehicle stability control
 functions.
 The following terms may be used throughout this description:
 ACC--Adaptive Cruise Control
 ABS--Anti-lock Braking System
 TCS--Traction Control System
 YSC--Yaw Stability Control
 VSC--Vehicle Stability Control (comprised of ABS/TCS/YSC)
 EHB--Electrohydraulic Braking
 The largest benefit of interfacing the ACC system with an active brake
 control system is the capability of the ACC sensing system (traditionally
 either a radar or infrared technology based device) to provide true
 vehicle ground speed. The ACC system also contains a vehicle yaw rate
 sensor that either provides new information for systems such as ABS or TCS
 or shared information for a system such as YSC. Vehicle yaw rate
 information is useful in determining vehicle turning during limit handling
 conditions.
 True vehicle ground speed is something that is virtually impossible to
 measure via the wheel speeds. Braking torque, acceleration (drive) torque,
 and ground resistance are examples of external forces that affect the
 wheel speed from accurately measuring the vehicle speed. With an accurate
 measurement of vehicle speed a more precise estimation of wheel slip can
 be computed. With a better estimation of wheel slip, systems such as ABS,
 TCS and YSC can be significantly improved. The base brake algorithm of EHB
 also uses vehicle speed to compute a pressure command for each of the
 wheels. Hence a more accurate estimation of vehicle speed potentially
 could provide more effective braking for variable vehicle speeds. FIG. 1
 illustrates the two basic systems and the sensors available to each
 vehicle control system.
 ACC assumes that relatively good driving conditions exist during system
 operation (i.e. high surface coefficient of friction). ABS and TCS
 generally only activate during conditions of wheel instability (i.e.
 excessive wheel slip due to braking or accelerating beyond the limit of
 the surface). YSC activates when it is determined that the vehicle is not
 following the intended trajectory during a turning maneuver. If ABS, TCS
 or YSC activates during ACC operation, then communication between the two
 systems (ACC-VSC) is required to either deactivate or significantly modify
 the operation of the ACC system.
 ACC is designed to decelerate the vehicle up to a maximum of 3 m/sec.sup.2
 (0.3 g) and accelerate the vehicle up to approximately 2 m/sec.sup.2 (o.2
 g) in order to properly control the vehicle spacing. In the event the ACC
 is operational while the vehicle is traversing adverse road conditions,
 the ABS and TCS systems may provide assistance with vehicle stability. If
 either the ABS or TCS system activates because of an actuation command
 from the ACC system, then the ACC system is notified to reduced its
 current acceleration request or modify its headway distance command for
 safer driving distances. If ABS activity is enabled during an ACC braking
 event, then the ACC system must maintain its braking command to control
 the vehicle spacing, however, the desired headway distance is modified to
 maintain safer spacing for the given road conditions.
 In the event that ACC is enabled and the driver activates YSC during a
 turning maneuver, then the headway setting for the ACC system must be
 modified to ensure safer spacing due to the adverse road conditions.
 In accordance with the provisions of the patent statutes, the principle and
 mode of operation of this invention have been explained and illustrated in
 its preferred embodiment. However, it must be understood that this
 invention may be practiced otherwise than as specifically explained and
 illustrated without departing from its spirit or scope.