Anti-skid brake control system

• US 5,141,294 A
• Filed: 09/22/1989
• Issued: 08/25/1992
• Est. Priority Date: 03/23/1987
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Van Zanten, Anton, Kost, Friedrich
• Primary Examiner(s): Butler, Douglas C.
• Assistant Examiner(s): BALLATO, JOSIE
• Application Number:
  US07/423,464
• Time in Patent Office: 1,068 Days
• Field of Search: 303/103, 303/104, 303/DIG. 4, 303/109, 303/100, 303/108, 303/107, 303/109, 364/426.02, 364/426.03, 364/572, 364/724.14, 364/724.15
• US Class Current: 303/182
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems

Abstract

An anti-skid brake control system for a motor vehicle includes at least one sensor for determining the deceleration V_R of a vehicle wheel, a device for determining the deceleration V_F of the vehicle, a device for determining the difference D of the vehicle and wheel decelerations (D=V_F -V_R), a control circuit responsive to the difference D for producing brake pressure control signals, and a brake pressure control device for increasing and decreasing the given brake pressure in response to the control signals from the control circuit. The difference D is also supplied to a ladder filter. During phases in which brake pressure is maintained at a constant level, the ladder filter is switched to identification by the control circuit and determines a reflection coefficient. The control signals then affect the brake pressure so as to select a slippage value on a stable branch of the μ slippage curve and near its maximum is derived from the distance of the reflection coefficient from the value "1".

Claims

1. Antiskid brake control system for a motor vehicle having wheels, said wheels during braking exhibiting slippage characterized by a μ

-slippage curve having a stable portion, an unstable portion, and a limit therebetween, said system comprising

means for determining the deceleration V_R of a wheel,

means for determining the deceleration V_F of the vehicle,

means for determining the difference D=V_F -V_R,

brake pressure control means which receives brake pressure control signals for increasing brake pressure, maintaining brake pressure constant, and reducing brake pressure,

a ladder filter which receives the difference D and uses the difference D to determine reflection coefficients during periods when brake pressure is maintained constant, and

a control circuit which receives the difference D and uses the difference D to generate said brake pressure control signals for said brake pressure control means, said control circuit providing a signal to said ladder filter to cause determination of said reflection coefficients when said brake pressure is maintained constant, said control circuit receiving said reflection coefficients and generating control signals which effect a slippage on the stable portion of the μ

-slippage curve and close to the limit from the distance of the highest reflection coefficient from a value of 1.

2. Antiskid brake control system as in claim 1 wherein said ladder filter also determines covariance, said control circuit using said covariance to generate said control signals when said covariance surpasses a threshold.

3. Antiskid brake control system as in claim 1 further comprising a low pass filter which filters the difference D, reception of said difference D by said control circuit being interrupted when said difference D surpasses a threshold of said filter, whereby generation of said reflection coefficients by said ladder filter is interrupted.

4. Antiskid brake control system as in claim 1 wherein said ladder filter is a normalized ladder filter.