Abstract: A brake pressure controller, responsive to a wheel speed sensor and coupled to a brake, performs a cyclic control of pressure applied to the brake. A brake pressure cycle includes a pressure apply stage and a pressure dump stage having activation conditions based upon a slip threshold parameter. A predetermined base threshold quantity is modified in dependence upon a measured time duration of the pressure dump stage and/or a slip depth error quantity so that a greater amount of slip is added to the base slip threshold when braking on a deformable surface than when braking on a non-deformable surface.

Abstract: Method and system are provided for "filtering out" a faulty wheel speed input signal in a vehicle control system, such as an ABS and/or TC system in order to ensure that the faulty wheel speed input signal does not contaminate or corrupt wheel speed information contained in the other wheel speed input signals. If such faulty wheel speed input signal indicates an abnormally high speed, it will increase the other wheel speed information if undetected. The wheel speed information is essential in detecting wheel instability or slip. It is important that wheel speed is not over-estimated since this may result in false slip detection and false ABS activation. Over-estimation of the vehicle speed would occur if the information from a spinning wheel is not properly filtered or compensated for. In one embodiment of the present invention, a bad sensor is detected by detecting and compensating for a single outlying ramp (outlier) of wheel speed.

Abstract: A dynamic rear proportioning system is integrated with an existing vehicle anti-lock braking system (ABS) and performs the function of the rear brake pressure proportioning where ABS is not required. The rear brake hydraulic channel(s) are isolated from the master cylinder by activating the rear isolation valves, provided in the ABS, to provide the optimum brake force balance, regardless of vehicle loading, without the use of a load sensing mechanism. The system estimates vehicle and wheel deceleration, vehicle speed, and lateral acceleration as well as the rear wheel slip to dynamically control the rear brake force. By continually updating these control parameters, the system can further increase or decrease the rear brake pressure to maintain the optimum brake force balance throughout the braking maneuver.

Abstract: Methods and systems for detecting and compensating for rough roads in an anti-lock brake system (ABS) through the use of a desensitizer factor which is utilized in a slip threshold desensitization circuit to desensitize slip threshold are described. The desensitizer factor is dependent on wheel acceleration. The desensitizer factor normally decays over time as long as the current value of the desensitizer factor is greater than a peak value of wheel acceleration. Otherwise, the desensitizer factor assumes the peak value of wheel acceleration, thereby "capturing" the peaks of wheel acceleration. The system includes a wheel speed sensor for measuring the speed of each of the vehicle wheels, and a control unit for determining whether the anti-lock brake system should be activated based on the value of the desensitized slip threshold. The desensitized slip threshold is utilized by the ABS to compensate for vehicle travel on rough roads.

Abstract: A method and system for detecting an incorrect indication of front-rear locked four-wheel drive operation of a vehicle capable of both front-rear locked four-wheel drive and unlocked two-wheel drive. The relative speed difference, defined as the absolute value of the difference between the rear wheel velocity and the arithmetic average of the front wheel velocities divided by the vehicle reference speed, is measured repeatedly. A count of measured relative speed differences greater than a relative speed threshold is calculated. The incorrect indication is detected when the count exceeds a rejection threshold. The relative speed threshold is predetermined based on histograms of relative speed data for two-wheel drive and four-wheel drive modes of operation. Once an incorrect indication is detected, modifications are made to the antilock brake system control algorithm.

Abstract: A brake pressure controller, responsive to a wheel speed sensor and coupled to a brake, performs a cyclic control of pressure applied to the brake. A brake pressure cycle includes a pressure apply stage and a pressure dump stage having activation conditions based upon a slip threshold parameter. A predetermined base threshold quantity is modified in dependence upon a measured time duration of the pressure dump stage and/or a slip depth error quantity so that a greater amount of slip is added to the base slip threshold when braking on a deformable surface than when braking on a non-deformable surface.

Abstract: The method and system for controllably restricting the on time of a pump of an electro-hydraulic control system for a hydraulic brake system by modeling the amount of hydraulic brake fluid in a low pressure accumulator (LPA) of the hydraulic brake system. Sensors sense wheel speed of their respective wheels of a vehicle. Control valves, including isolation and dump valves, together with the pump, vary the amount of brake fluid in the LPA. A control unit electrically coupled to the pump, the control valves and the wheel speed sensors, initially detects an electro-hydraulic control event based on the sensed wheel speeds and then activates the control valves and pump which vary the amount of brake fluid in the LPA. The control unit models the amount of brake fluid in the LPA during the activation and controls the state of the pump based on the modeled amount of brake fluid in the LPA.

Abstract: A method and system are disclosed for controlling an anti-lock brake system based on vehicle deceleration. The system includes a wheel speed sensor and control unit for performing the method steps of sensing a wheel speed and determining a wheel deceleration and a vehicle deceleration therefrom. The control unit also performs the method steps of determining an initial deceleration threshold representing a pre-lockup condition, determining a final deceleration threshold based on the vehicle deceleration, comparing the wheel deceleration to the final deceleration threshold, and activating the vehicle anti-lock brake system if the wheel deceleration exceeds the final deceleration threshold.

Abstract: A method and system for modifying anti-lock brake control to a vehicle experiencing drivetrain-induced oscillations. A wheel speed of each of the wheels is sensed to generate a corresponding speed signal. A drivetrain-induced oscillation condition is detected in one of two ways. First, a wheel speed peak count is determined for each of the wheels. A drivetrain-induced oscillation is then detected if multiple peaks occur within a predetermined period of time. Alternatively, a frequency of oscillation for each of the wheel speeds is determined and compared to a predetermined frequency threshold. Upon determining that the vehicle is experiencing drivetrain-induced oscillation during an ABS event, brake pressure is applied to the driven wheels at approximately the same frequency as the frequency of oscillation of the drivetrain-induced oscillation.

Abstract: A method and system for detecting a braking event on a high mu surface while in four-wheel drive and modifying the anti-lock brake control accordingly. The method includes determining whether the vehicle is braking on a high mu surface and inhibiting brake pressure application to the rear wheels until it is determined the vehicle is braking on a high mu surface. The system includes wheel speed sensors, an electronic control unit and control valves for carrying out the method.

Abstract: A method and system for correcting an overestimated vehicle reference speed is presented. In one embodiment, speed, slip, and acceleration quantities are computed for at least one wheel of a vehicle. The speed, slip, and acceleration quantities are compared to selected speed, slip, and acceleration thresholds, respectively. A count is incremented if the quantities are consistent with at least one vehicle reference speed being overestimated. The existence of at least one overestimated vehicle reference speed is detected when the count attains a selected threshold. The vehicle reference speeds are modified when the overestimated vehicle reference speed is detected.

Abstract: A method and system for modifying anti-lock brake control to a vehicle braking on a surface having a low-mu to split-mu transition. The time duration of the apply stage of an anti-lock brake system cycle is measured for the two front wheels. The measured apply stage durations are compared to a threshold. The braking coefficients of the two front wheels are qualified based on these comparisons. Each wheel is qualified as normal-duration if the apply stage duration is less than the threshold, and long-duration if the apply stage duration is greater than the threshold. Normal low-mu pressure control is continued if both front wheels are qualified as normal-duration. Split-mu pressure control is activated when exactly one of the front wheels is qualified as long-duration. The split-mu pressure control restricts the rate of brake pressure applied to the long-duration wheel. Low-mu to high-mu pressure control is utilized when both wheels are qualified as long-duration.