Anti-skid brake control system with fail-safe arrangement

• US 4,499,543 A
• Filed: 09/24/1982
• Issued: 02/12/1985
• Est. Priority Date: 09/28/1981
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Matsuda, Toshiro
• Primary Examiner(s): Dobeck, B.
• Assistant Examiner(s): BERGMANN, SAUL
• Application Number:
  US06/423,187
• Time in Patent Office: 872 Days
• Field of Search: 364/426, 303/92, 303/93, 303/110
• US Class Current: 701/76
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

In a fail-safe arrangement for an anti-skid brake control system, several related pairs of sensor and control signals are produced only in certain possible combinations. The fail-safe arrangement checks each pair of signals and produces an error signal if a non-conventional combination of any of the pairs of signals occurs. In response to the error signal, the automatic anti-skid control system is disabled in such a way as to allow continued manual brake operation.

Claims

1. An anti-skid brake control system for an automotive vehicle, comprising:

a detector associated with a wheel of said vehicle for detecting acceleration of said wheel and for producing an acceleration indicative signal having a value indicative of said detected wheel acceleration;

a reference signal generator for producing a plurality of reference signals, each differing in value from any of the other reference signals of said plurality of reference signals, and each representing a threshold value to be compared with the value of said acceleration indicative signal;

a comparator for respectively comparing the value of said acceleration indicative signal with the value of each of said plurality of reference signals and for producing a comparator signal which is a discrete combination of a plurality of outputs, each of said outputs resulting from a corresponding one of said respective comparisons;

a control signal generator responsive to said comparator signal for producing a control signal for controlling braking operation, said control signal having a value derived on the basis of the combination of said outputs; and

a fault detector responsive to said comparator signal for detecting whether said combination of outputs is a member of a predetermined set all possible combinations occurring in a non-malfunctioning control system, and for producing a fault signal whenever said combination of outputs constituting said comparator signal is detected not to be a member of said set, said fault signal being useable to demand a predetermined back-up operation.

3. The system as set forth in claim 1 or 2, wherein said reference signal generator determines at least two different slippage reference signals, and said sensing means comprises at least two comparators for comparing wheel slippage with said slippage reference signals and for producing comparator signals which define a wheel slipping condition in preselected combinations of said comparator signals.

4. The system as set forth in claim 3, wherein said fault detector comprises an AND gate connected to said comparators in such a manner that it produces said fault signal when abnormal combination out of said preselected combinations of said comparator signals is detected.

5. The system as set forth in claim 4, which further comprises means for disabling anti-skid control in response to said fault signal.

6. The system as set forth in claim 5, which further comprises a control valve controlling a hydraulic brake pressure, and said disabling means is adapted to disable said control valve operation.

7. The system as set forth in claim 1 or 2, wherein said reference signal generator comprises means for determining different acceleration and deceleration reference signals, and said sensing means comprises at least two comparators respectively comparing wheel acceleration and deceleration with said reference signals and producing comparator signals which define, in combination, a wheel slipping condition.

8. The system as set forth in claim 7, wherein said fault detector comprises an AND gate connected to said comparators in such a manner that said AND gate produces said fault signal when a combination indicating a malfunction is detected.

9. The system as set forth in claim 8, which further comprises means for disabling anti-skid control in response to said fault signal.

10. The system as set forth in claim 9, which further comprises a control valve controlling a hydraulic brake pressure, and said disabling means is adapted to disable said control valve operation.

2. An anti-skid brake control system for a vehicle having a brake system, comprising:

a sensor associated with a wheel of said vehicle for sensing the acceleration of said wheel and for deriving an acceleration indicative signal having a value representative of said sensed wheel acceleration;

a detector responsive to said acceleration indicative signal for producing a condition indicative signal having a value which varies with the acceleration and deceleration of said vehicle wheel, said acceleration and deceleration condition being detected on the basis of said acceleration indicative signal value;

a controller responsive to said condition indicative signal for deriving a control signal controlling operation of said brake system and optimizing braking operation; and

a fault detector for detecting whether the value of said condition indicative signal value varies from predetermined values which are representative of all of the possible conditions occurring in non-malfunctioning brake control operation, and for producing a fault signal whenever said value of said condition indicative signal is detected to vary from said predetermined values.

11. A fail-safe arrangement for an anti-skid brake control system applied to a vehicle brake system, comprising:

(a) at least one brake condition sensing means associated with a single wheel for sensing a vehicle operating condition pertaining to braking and outputting a plurality of sensor signals indicative thereof, the sensor signals being so produced that specific combinations of sensor signal values will not occur when said sensing means is functioning properly;

(b) logic means responsive to the sensor signals for outputting at least one control signal in accordance with the sensor signals;

(c) anti-skid actuating means responsive to the control signal for actuating and controlling the anti-skid brake control system in accordance with the control signal;

(d) detecting means for monitoring the sensor signals, detecting combinations thereof matching one of said specific combinations, and for outputting an error signal when the combination of said sensor signal values is one of said specific combinations; and

(e) a fail-safe device for preventing operation of said anti-skid actuating means in response to the error signal while allowing manual operation of the vehicular brake system.

12. The fail-safe arrangement of claim 11, wherein said logic means outputs at least two control signals in such a manner that only specific combinations of the control signals will occur when said logic means is functioning properly, and wherein said detecting means additionally outputs the error signal when the combination of the control signals is not one of said specific combinations.

14. The fail-safe arrangement of claim 11, 12, or 13, further comprising display means for indicating to vehicle occupants that the anti-skid brake control system is malfunctioning in response to the error signal.

13. A fail-safe arrangement for an anti-skid brake control system applied to a vehicle brake system, comprising:

(a) at least one brake condition sensing means associated with a single wheel for sensing a vehicle operating condition pertaining to braking, and for outputting a sensor signal made up of first pairs of binary signals indicative of said sensed vehicle operating condition, the sensor signal being so outputted that a first set of specific combinations of values of said first pairs of binary signals will not occur when said sensing means is not malfunctioning;

(b) logic means responsive to the sensor signal for outputting a control signal in accordance with the sensor signal, said control signal being made up of second pairs of binary signals in such a manner that a second set of specific combinations of values of said second pairs of binary signals will not occur when said one of said sensing means and said logic means is not malfunctioning;

(c) anti-skid actuating means responsive to the sensor signal for actuating and controlling the anti-skid brake control system in accordance with the sensor signal;

(c) detecting means for monitoring the sensor signal, for detecting combinations thereof matching one of said first set of specific combinations, for monitoring said control signal, for detecting combinations thereof matching one of said second set of specific combinations, for outputting an error signal when the combination of said sensor signal values is one of said first set of specific combinations, and for outputting an error signal when the combination of said control signal values is one of said second set of specific combinations, said detecting means comprising a plurality of AND gates, each of which receives as inputs a respective pair of binary values from a set of binary values consisting of said first pairs of binary values and said second pairs of binary values, with inverters provided at selected input terminals thereof such that at least one AND gate outputs a high-level signal in response to the presence of a specific combination, from one of said first and said second sets of specific combinations and an OR gate receiving as inputs the outputs of the AND gates and outputting the error signal in response to a high-level signal from any one of the AND gates;

(e) a fail-safe device for preventing operation of said actuating means in response to the error signal while allowing manual operation of the vehicular brake system.