Method for detecting brake circuit failure

Abstract

A method is provided for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit and a second hydraulic brake. The first hydraulic brake circuit includes a pressure sensor. A pressure is measured within the first hydraulic brake circuit of the vehicle using the pressure sensor. An expected vehicle acceleration is estimated in response to the measured pressure. An actual vehicle acceleration is measured. A determination is made whether the expected vehicle acceleration is within a predetermined range of the actual acceleration. A first and second wheel differential is determined. A determination is made whether the first wheel differential and second wheel differential satisfy a predetermined condition. A fault in the hydraulic brake system is detected in response to determining whether the first and second wheel differentials satisfy a predetermined condition and in response to determining whether the actual and estimated acceleration are within the predetermined range.

1 . A method for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit for actuating a first set of vehicle brake actuators for a first set of wheels and a second hydraulic brake circuit for actuating a second set of vehicle brake actuators for a second set of wheels, said first hydraulic brake circuit including a pressure sensor, said method comprising the steps of: 
 measuring a pressure within said first hydraulic brake circuit of said vehicle using said pressure sensor;    estimating an expected vehicle acceleration in response to said measured pressure;    determining an actual acceleration of said vehicle; and    detecting said fault in response to a comparison of said actual acceleration and said expected acceleration.    
   
   
       2 . The method of  claim 1  wherein said vehicle includes a vehicle brake module, said method further comprising the step of deactivating brake modulation by said vehicle brake module in response to detecting said fault.  
   
   
       3 . The method of  claim 1  wherein said comparison of said actual acceleration and said expected acceleration includes determining whether said actual acceleration and said estimated acceleration are within a predetermined range.  
   
   
       4 . The method of  claim 1  further comprising the step of determining a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels and a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels.  
   
   
       5 . The method of  claim 4  wherein said step of detecting said fault is further responsive to said first wheel differential and said second wheel differential satisfying a predetermined condition.  
   
   
       6 . The method of  claim 5  wherein said first wheel differential and said second wheel differential are opposite signs.  
   
   
       7 . The method of  claim 5  wherein said satisfying predetermined conditions includes multiplying said first wheel differential and second wheel differential and producing a negative result.  
   
   
       8 . The method of  claim 4  wherein said first wheel differential comprises a comparison of a velocity of said first wheel of said first set of wheels with a velocity of said first wheel of said second set of wheels.  
   
   
       9 . The method of  claim 8  wherein said second wheel differential comprises a comparison of a velocity of said second wheel of said first set of wheels with a velocity of said second wheel of said second set of wheels.  
   
   
       10 . The method of  claim 4  wherein said first wheel differential comprises a first delta slip, said first delta slip being determined in response to a difference between a velocity of said first wheel of said first set of wheels and a velocity of said first wheel of said second set of wheels divided by said velocity of said first set of wheels.  
   
   
       11 . The method of  claim 10  wherein said second wheel differential comprises a second delta slip, said second delta slip being determined in response to a difference between a velocity of said second wheel of said first set of wheels and a velocity of said second wheel of said second set of wheels divided by said velocity of said second set of wheels.  
   
   
       12 . A method for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit for actuating a first set of vehicle brake actuators for a first set of wheels and a second hydraulic brake circuit for actuating a second set of vehicle brake actuators for a second set of wheels, said first hydraulic brake circuit including a pressure sensor, said method comprising the steps of: 
 measuring a wheel velocity of each wheel of said vehicle;    determining a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels;    determining a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels; and    detecting said fault in response to said first wheel differential and said second wheel differential satisfying a predetermined condition.    
   
   
       13 . The method of  claim 12  wherein said first wheel differential and said second wheel differential are opposite signs.  
   
   
       14 . The method of  claim 12  wherein said satisfying a predetermined condition includes multiplying said first wheel differential and second wheel differential and producing a negative result.  
   
   
       15 . The method of  claim 12  wherein said vehicle includes a vehicle brake module, said method further comprising the step of deactivating brake modulation by said vehicle brake module in response to detecting said fault.  
   
   
       16 . The method of  claim 12  wherein said first wheel differential comprises a comparison of a velocity of said first wheel of said first set of wheels with a velocity of said first wheel of said second set of wheels, and wherein said second wheel differential comprises a comparison of a velocity of said second wheel of said first set of wheels with a velocity of said second wheel of said second set of wheels.  
   
   
       17 . The method of  claim 12  wherein said first wheel differential comprises a first delta slip, said first delta slip being determined in response to a difference between a velocity of said first wheel of said first set of wheels and a velocity of said first wheel of said second set of wheels divided by said velocity of said first set of wheels, and wherein said second wheel differential comprises a second delta slip, said second delta slip being determined in response to a difference between a velocity of said second wheel of said first set of wheels and a velocity of said second wheel of said second set of wheels divided by said velocity of said second set of wheels.  
   
   
       18 . The method of  claim 12  further comprising the steps of: 
 measuring a pressure;    estimating an expected vehicle acceleration; and    comparing an actual vehicle acceleration and said expected vehicle acceleration;    wherein said step of detecting said fault is further responsive to said comparison of said actual acceleration and said expected acceleration.    
   
   
       19 . A method for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit for actuating a first set of vehicle brake actuators for a first set of wheels and a second hydraulic brake circuit for actuating a second set of vehicle brake actuators for a second set of wheels, said first hydraulic brake circuit including a pressure sensor, said method comprising the steps of: 
 measuring a pressure within said first hydraulic brake circuit of said vehicle using said pressure sensor;    estimating an expected vehicle acceleration in response to said measured pressure;    determining an actual vehicle acceleration of said vehicle;    determining if said expected vehicle acceleration is within a predetermined range of said actual acceleration;    providing whether said vehicle acceleration and said actual vehicle acceleration are within said predetermined range, then determining a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels and determining a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels; and    detecting said fault in response to said first wheel differential and said second wheel differential satisfying a predetermined condition.    
   
   
       20 . The method of  claim 19  wherein said first wheel differential and said second wheel differential are opposite signs.  
   
   
       21 . The method of  claim 20  wherein said satisfying predetermined conditions includes multiplying said first wheel differential and second wheel differential and producing a negative result.  
   
   
       22 . The method of  claim 19  wherein said vehicle includes a vehicle brake module, said method further comprising the step of deactivating brake modulation by said vehicle brake module in response to detecting said fault.  
   
   
       23 . A method for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit for actuating a first set of vehicle brake actuators for a first set of wheels and a second hydraulic brake circuit for actuating a second set of vehicle brake actuators for a second set of wheels, said first hydraulic brake circuit including a pressure sensor, said method comprising the steps of: 
 measuring a wheel velocity of each wheel;    determining a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels;    determining a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels;    determining if said first wheel differential and said second wheel differential are opposite signs;    if said first wheel differential and said second wheel differential are opposite signs, then measuring a pressure within said first hydraulic brake circuit of said vehicle using said pressure sensor;    estimating an expected vehicle acceleration in response to said measured pressure;    determining an actual vehicle acceleration of said vehicle;    determining if said expected vehicle acceleration is within a predetermined range of said actual acceleration; and    detecting said fault in response to said determination of said estimated vehicle acceleration and said actual vehicle acceleration within said predetermined range.    
   
   
       24 . The method of  claim 23  wherein said vehicle includes a vehicle brake module, said method further comprising the step of deactivating brake modulation by said vehicle brake module in response to said detection.  
   
   
       25 . The method of  claim 23  wherein said first wheel differential comprises a comparison of a velocity of said first wheel of said first set of wheels with velocity of said first wheel of said second set of wheels, and wherein said second wheel differential comprises a comparison of a velocity of said second wheel of said first set of wheels with a velocity of said second wheel of said second set of wheels.  
   
   
       26 . The method of  claim 23  wherein said first wheel differential comprises a first delta slip, said first delta slip being determined in response to a difference between a velocity of said first wheel of said first set of wheels and a velocity of said first wheel of said second set of wheels divided by said velocity of said first set of wheels, and wherein said second wheel differential comprises a second delta slip, said second delta slip being determined in response to a difference between a velocity of said second wheel of said first set of wheels and a velocity of said second wheel of said second set of wheels divided by said velocity of said second set of wheels.  
   
   
       27 . A method for detecting a fault in a hydraulic brake system of a vehicle having a first hydraulic brake circuit for actuating a first set of vehicle brake actuators for a first set of wheels and a second hydraulic brake circuit for actuating a second set of vehicle brake actuators for a second set of wheels, said first hydraulic brake circuit including a pressure sensor, said method comprising the steps of: 
 measuring a pressure within said first hydraulic brake circuit of said vehicle using said pressure sensor;    determining an actual vehicle acceleration of said vehicle;    determining a correlation ratio between said pressure and said actual vehicle acceleration;    determining whether said correlation ratio is within a first predetermined range, measuring a wheel velocity of each wheel;    determining a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels;    determining a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels;    determining whether said first wheel differential and said second wheel differential are opposite signs;    detecting said fault in response to said step of determining said first wheel differential and said second wheel differential are opposite signs and in response to said step of determining whether said correlation ratio is within said predetermined range.    
   
   
       28 . The method of  claim 27  wherein said vehicle includes a vehicle brake module, said method further comprising the step of deactivating brake modulation by said vehicle brake module in response to detecting said fault.  
   
   
       29 . The method of  claim 27  wherein said step of determining whether said correlation ratio is within a predetermined range correlation ratio includes a comparison between said expected vehicle acceleration and said actual vehicle acceleration.  
   
   
       30 . The method of  claim 27  wherein said step of deactivating said brake modulation includes deactivating an anti-lock brake function.  
   
   
       31 . The method of  claim 27  wherein said step of deactivating said brake modulation includes deactivating a traction control function.  
   
   
       32 . The method of  claim 27  wherein said step of deactivating said brake modulation includes deactivating a yaw stability function.  
   
   
       33 . A vehicle control system comprising: 
 a braking control system including an vehicle brake module that is operable in at least one operating state;    a first circuit of pressurized brake fluid for providing pressurized hydraulic brake fluid to a first set of brake actuators;    a second circuit of pressurized brake fluid for providing pressurized hydraulic brake fluid to a second set of brake actuators;    a plurality of sensors for monitoring wheel velocity and acceleration; and    a pressure sensor for monitoring a pressure within said first circuit of pressurized brake fluid;    wherein said vehicle brake module determines an estimated acceleration based on said pressure within said first hydraulic brake circuit and compares to said estimated acceleration to an actual acceleration, wherein said vehicle brake module further determines a first wheel differential and a second wheel differential from said wheel velocity, and wherein said vehicle brake module deactivates said at least one operating state in response to said first wheel differential and said second wheel differential satisfying a predetermined condition and said comparison of said actual acceleration and said estimated acceleration.    
   
   
       34 . The vehicle control system of  claim 33  wherein said first wheel differential and said second wheel differential are opposite signs.  
   
   
       35 . The method of  claim 33  wherein said satisfying predetermined conditions includes multiplying said first wheel differential and second wheel differential and producing a negative result.  
   
   
       36 . The vehicle control system of  claim 33  wherein said at least one operating state includes a anti-lock braking state.  
   
   
       37 . The vehicle control system of  claim 33  wherein said at least one operating state includes a traction control state.  
   
   
       38 . The vehicle control system of  claim 33  wherein said at least one operating state includes a yaw stability state.  
   
   
       39 . A hydraulic brake circuit fault detection system comprising: 
 a braking control system including an vehicle brake module that is operable in at least one operating state;    a pressure sensor for monitoring a hydraulic brake circuit; and    a controller for receiving a plurality of vehicle operating inputs, said controller determining a wheel slip of a first set of wheels and a second set of wheels and an expected acceleration in response to said received inputs;    wherein said controller compares said expected acceleration with an actual vehicle acceleration, wherein said controller determines a first wheel differential between a first wheel of said first set of wheels and a first wheel of said second set of wheels; wherein said controller determines a second wheel differential between a second wheel of said first set of wheels and a second wheel of said second set of wheels; wherein said controller determines whether said first wheel differential and said second wheel differential satisfy a predetermined condition, and wherein said controller detects a fault in response to said determination of satisfying said predetermined condition and in response to said comparison of said expected acceleration and said actual acceleration.    
   
   
       40 . The detection system of  claim 39  wherein said satisfying predetermined conditions includes multiplying said first wheel differential and second wheel differential and producing a negative result.  
   
   
       41 . The detection system of  claim 39  wherein said controller deactivates said vehicle brake module in response to detecting said fault.  
   
   
       42 . The detection system of  claim 39  wherein said vehicle brake module includes at least one operating state for controlling said vehicle braking.  
   
   
       43 . The detection system of  claim 42  wherein said at least one operating state includes an anti-lock braking state.  
   
   
       44 . The detection system of  claim 42  wherein said at least one operating state includes a traction control state.  
   
   
       45 . The detection system of  claim 42  wherein said at least one operating state includes a yaw stability control state.