Haptic braking method and system

[0002] 1. Field of the Invention

[0003] The present invention generally relates to control systems for automotive vehicles, and more particularly relates to a haptic braking system of a vehicle in an active cruise control mode.

[0004] 2. Description of the Related Art

[0005] Cruise control systems known in the art enable a driver of a vehicle to set a target vehicle speed. While such systems allow the driver to be less active in driving the vehicle, the driver must be aware of any potential rear end collision with any preceding vehicle. As such, there also exists technology in the art for providing a collision warning to the driver during an active cruise control mode. This technology includes visual indicators, tactile indicators, and audio indicators that are all designed to immediately notify the driver of a potential collision into a rear end of any preceding vehicle. Consequently, the driver has an opportunity to timely utilize a braking system of the vehicle as needed to avoid the collision. Recently, human factor research has indicated that one or more brake pulses may offer a better solution for notifying the driver of the potential collision. The automotive industry is therefore striving to incorporate haptic braking into a cruise control system of an automobile vehicle.

[0006] One form of the present invention is a haptic braking method. First, a signal indicative of a request to decelerate a wheel in a haptic manner is received. Second, brake fluid is applied to a brake adjacent the wheel in response to the signal. Third, a pressure level of the brake fluid is cyclically varied over at least one cycle.

[0007] A second form of the present invention is also a haptic braking method. First, a signal indicative of a request to decelerate a wheel in a haptic manner is received. Second, in response to the signal, a pump is operated to apply a brake fluid to a brake adjacent the wheel. Third, a valve is operated to cyclically vary a pressure level of the brake fluid over at least one cycle.

[0008] A third form of the present invention is a haptic braking system comprising a controller, a pump, and a valve. The controller is operable to provide control signals in response to a signal indicative of a request to decelerate a wheel in a haptic manner. In response to a first control signal, the pump is operable to apply a brake fluid to a brake adjacent the wheel. In response to a second control signal, the valve is operable to cyclically vary a pressure level of the brake fluid over at least one cycle.

[0009] A fourth form of the present invention is also a haptic braking system. The system comprises a means for applying a supply of brake fluid to a brake in response to a signal indicating a request to decelerate a wheel in a haptic manner. The system further comprises a means for cyclically varying a pressure level of the brake fluid over at least one cycle.

[0010] The foregoing forms, and other forms, features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.

[0011] FIG. 1 is a schematic diagram of a braking system known in the art, and one embodiment of a haptic brake controller in accordance with the present invention;

[0012] FIG. 2 is a flow diagram of one embodiment of a haptic braking routine in accordance with the present invention;

[0013] FIG. 3A is an exemplary graphic illustration of operational states of a pump assembly and valve assemblies of the FIG. 1 braking system;

[0014] FIG. 3B is an exemplary graphic illustration of a current signal provided to a solenoid of an ISO valve assembly during the FIG. 2 haptic braking routine; and

[0015] FIG. 4 is a block diagram of one embodiment of a current signal regulator in accordance with the present invention.

[0016] Referring to FIG. 1, a conventional braking system 10 for a wheel 20 and a brake 21 adjacent wheel 20 is shown. System 10 includes a braking assembly 11, a prime valve assembly 12, a brake fluid pump assembly 13, an apply valve assembly 14, a release valve assembly 15, an accumulator 16, and a variable isolation valve assembly 17. Braking assembly 11 has a brake pedal arm 11arotatably coupled to a wall W of a vehicle. A push rod 11bextends through wall W and is coupled to brake pedal arm 11aand a booster 11c. A pushing of push rod 11bin a direction toward wall W releases brake fluid from brake fluid tank 11dthrough a primary port of a master cylinder 11e.

[0017] Prime valve assembly 12 includes a prime valve 12aspring biased to a fully open position and a solenoid 12bfor closing prime valve 12ain response to a control signal in the form of a current signal CS₁. A hydraulic line H1 couples the primary port of master cylinder 11eand prime valve 12a.

[0018] Brake fluid pump assembly 13 includes a current driver 13afor selectively driving a motor M with piston structure 13bwhereby brake fluid from brake fluid tank 11dis pumped throughout braking system 10 in response to control signal in the form of a current signal CS₂. A hydraulic line H2 couples prime valve 12a, check valve 16b, and accumulator 16.

[0019] Apply valve assembly 14 includes an apply valve 14aspring biased to a fully open position and a solenoid 14bfor linearly closing apply valve 14ain response to a control signal in the form of a current signal CS₃. A hydraulic line H3 couples damper 13c, apply valve 14a, and an ISO valve 17aof variable valve assembly 17. Release valve assembly 15 includes a release valve 15aspring biased to a closed position and a solenoid 15bfor opening release valve 15ain response to a control signal in the form of a current signal CS₄. A hydraulic line H4 couples apply valve 14a, release valve 15a, and brake 21. Hydraulic line H5 couples release valve 15aand accumulator 16. A check valve 14cof apply valve assembly 14 prevents brake fluid from flowing from hydraulic line H3 to hydraulic line H4.

[0020] Variable isolation valve assembly 17 includes an ISO valve 17aspring normally biased into a fully open position and a solenoid 17bfor linearly closing ISO valve 17ain response to a control signal in the form of a current signal CS₅. A hydraulic line H6 couples the primary port of master cylinder 11eand ISO valve 17a. A check valve 17cof variable isolation valve assembly 17 prevents brake fluid from flowing from hydraulic line H3 to hydraulic line H6. A haptic brake controller 30 of the present invention implements a haptic braking method of the present invention in response to a request deceleration signal RD_sconventionally provided by an ACC controller 18. As appreciated by those having skill in the art, ACC controller 18 provides request deceleration signal RD_s(in analog or digital form) to controller 30 whenever wheel 20 needs to be decelerated during an active cruise control mode, e.g., a potential rear end collision with a preceding car. The haptic braking method of the present invention comprises three phases. In a pumping-up phase, brake fluid is applied to brake 21 to initiate a deceleration of wheel 20. In a haptic alert phase, a pressure level of the brake fluid being applied to brake 21 is cyclically varied over one or more cycles to cause a haptic braking of wheel 20. In a phase-out phase, brake fluid is drained from hydraulic lines H4→H3→H6.

[0021] Controller 30 is preferably an electronic circuit comprised of one or more components that are assembled as a common unit. Alternatively, for the multiple component embodiments, one or more of these components may be distributed throughout a vehicle housing controller 30. Controller 30 may be comprised of digital circuitry, analog circuitry, or both. Also, controller 30 may be programmable, a dedicated state machine, or a hybrid combination of programmable and dedicated hardware. To implement the principals of the present invention, controller 30 can further include any control clocks, interfaces, signal conditioners, filters, Analog-to-Digital (A/D) converters, Digital-to-Analog (D/A) converters, communication ports, or other types of operators as would occur to those having ordinary skill in the art.

[0022] In one embodiment, controller 30 includes an integrated processing unit (not shown) operatively coupled to one or more solid-state memory devices (not shown). It is also preferred that this memory contain programming corresponding to a haptic braking routine 40 (FIG. 2) for implementing the haptic braking method of the present invention and that this memory be arranged for reading and writing of data in accordance with the principals of the present invention. The memory may be either volatile or nonvolatile and may additionally or alternatively be of the magnetic or optical variety.

[0023] Referring additionally to FIG. 2, a haptic braking routine 40 in accordance with the present invention is shown. Controller 30 implements routine 40 in response to request deceleration signal RD_s. The pumping-up phase of routine 40 encompasses a stage S42, a stage S44, a stage S46, and a stage S48. The haptic alert phase of routine 40 encompasses a stage S50. The phase-out-phase of routine 40 encompasses a stage S52 and a stage S54.

[0024] During stage S42 of routine 40, controller 30 inputs an ambient temperature signal AT_sto conventionally determine a deceleration overshooting suppression as appreciated by those having ordinary skill in the art. In one embodiment, controller 30 executes a standard temperature model to determine if a temperature of the brake fluid will exceed a reference temperature when being applied to brake 21. If the temperature model indicates the temperature of the brake fluid will be less than the reference temperature when applied to brake 21, then controller 30 will activate the pumping-up phase and the haptic alert phase for a first standard period of time. For example, if the temperature model indicates the brake fluid will have a temperature that is less than −10° C. when applied to wheel 20, then controller 30 will activate the pumping-up phase and the haptic alert phase for 160 milliseconds. If the temperature model indicates the temperature of the brake fluid will be equal to or greater than the reference temperature when applied to brake 21, then controller 30 will activate the pumping-up phase and the haptic alert phase for a second standard period of time. For example, if the temperature model indicates the brake fluid will have a temperature that is equal to or greater than −10° C. when applied to brake 21, then controller 30 will activate the pumping-up phase and the haptic alert phase for eighty (80) milliseconds.

[0025] Controller 30 proceeds to stage S44 of routine 40 to determine pumping-up commands for selectively controlling prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17a. In one embodiment, controller 30 provides current signal CS₂to current driver 13ato activate motor M whereby brake fluid will be pumped into hydraulic line H4 and applied to brake 21. FIG. 3A illustrates an operating state of prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17aduring stage S44.

[0026] Controller 30 proceeds to stage S46 to monitor the speed of wheel 20 to thereby detect an initial deceleration of wheel 20. In one embodiment, controller 30 receives wheel speed signal WS_sfrom variable reluctance sensor V to thereby monitor wheel speed signal WS_s. During stage S48, controller 30 determines if wheel speed signal WS_sis indicating wheel 20 has experienced a reference level of deceleration. Controller 30 repeats stage S46 and stage S48 until wheel speed signal WS_sis indicating wheel 20 has experienced the reference level of deceleration.

[0027] During stage S50 of routine 40, controller 30 determines haptic alert commands for selectively controlling prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17a. In one embodiment, controller 30 provides current signal CS₅to ISO solenoid 17band undulates current signal CS₅between a fully energized level ENG (FIG. 3B) and de-energized level DENG (FIG. 3B). In response thereto, ISO valve 17aundulates between a fully open position and a closed position to cyclically vary the pressure level of the brake fluid within hydraulic line H3 and hydraulic line H4. As a result, wheel 20 experiences one or more haptic movements. Stage S50 is terminated upon the completion of the standard time period determined during stage S42. FIG. 3A illustrates an operating state of prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17aduring stage S50.

[0028] Referring additionally to FIG. 3B, in an another embodiment, controller 30 undulates current signal CS₅between an intermediate energized level INT1 and an intermediate energized level INT2 in order to undulate ISO valve 17abetween a first partially open state and a second partially open state. Intermediate energized level INT1 and an intermediate energized level INT2 are utilized in lieu of a fully energized level ENG and de-energized level DENG to minimize wear and tear on a seat of ISO valve 17a.

[0029] “Referring additionally to FIG. 4, a current signal regulator 31 of controller 30 is shown. Regulator 31 includes an error signal generator 32 and a PID 33. During stage S50, generator 32 provides an error signal E_Sthat is a differential between a level of request deceleration signal RD_Sas received from controller 20 and a level of an actual deceleration signal AD_Sthat is computed as a function of wheel speed signal WS_S. Error signal E_Sis provided to PID 33, and PID 33 outputs current signal CS₅having duty cycles as a function of error signal E_S. As such, the duty cycles of current signal CS₅are dynamically adjusted to thereby dynamically adjust the cyclical variance in the pressure level of the brake fluid. Actual deceleration signal AD_Sis provided to controller 20 to enable controller 20 to dynamically adjust the level of request deceleration signal RD_Sas needed.

[0030] Referring to FIGS. 1 and 2, during stage S52 of routine 40, controller 30 determines haptic phase-out commands for selectively controlling prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17a. In one embodiment, controller 30 de-energizes current signal CS₅to ISO solenoid 17bto fully open ISO valve 17awhereby brake fluid flows back to master cylinder 11e. FIG. 3A illustrates an operating state of prime valve 12a, motor M, apply valve 14a, release valve 15a, and ISO valve 17aduring stage S52. During stage S54 of routine 40, controller 30 conventionally provides a vacuum relief and elimination of trap pressure from hydraulic lines H1-H5.

[0031] System 10 includes additional wheels, brakes, and valve assemblies that were not shown for the simplicity of describing the present invention. However, those having ordinary skill in the art will appreciate that controller 30 can control haptic braking of two or more wheels of system 10.

[0032] While the embodiments of the present invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.