Methods for transitioning into reduced braking performance modes upon failure of a primary braking system

Abstract

A method according to the present disclosure includes identifying a failure in functionality of the primary braking system, and upon identifying the failure, mitigating an abrupt increase in a pedal travel distance required to brake or otherwise decelerate the vehicle so as to provide a smooth transition from a primary braking mode to a fallback braking mode. Mitigating the increase in the pedal travel distance may include initiating a transition to the fallback braking mode, activating at least one of a plurality of transition braking modes, and gradually increasing the pedal travel distance by deactivating at least one of the at least one previously activated transition braking modes.

What is claimed is: 
     
         1 . A method for transitioning a braking system of a vehicle between primary and fallback modes, comprising:
 identifying a failure in functionality of the primary braking system;   upon identifying the failure, mitigating an abrupt increase in a pedal travel distance required to brake or otherwise decelerate the vehicle so as to provide a smooth transition from a primary braking mode to a fallback braking mode, the mitigating the increase in the pedal travel distance comprising:
 initiating a transition to the fallback braking mode; 
 activating at least one of a plurality of transition braking modes; and 
 gradually increasing the pedal travel distance by deactivating at least one of the at least one previously activated transition braking modes. 
   
     
     
         2 . The method of  claim 1 , wherein a first transition braking mode of the plurality of transition braking modes comprises reducing a working volume of a primary braking system so that hydraulic braking energy is supplied to wheels of an axle of a vehicle. 
     
     
         3 . The method of  claim 2 , wherein a second transition braking mode of the plurality of transition braking modes comprises selecting a source of braking energy to be supplied to wheels of an axle of the vehicle by an electronic parking brake. 
     
     
         4 . The method of  claim 3 , wherein selecting a source of braking energy includes:
 supplying braking energy via antilock braking when a determined speed of the vehicle is above a threshold speed; and   supplying braking energy via dynamic clamping in a slip dependent manner when the determined speed of a vehicle is at or below a threshold speed.   
     
     
         5 . The method of  claim 1 , wherein a third transition braking mode of the plurality of transition braking modes comprises actuating at least one additional method of applying dynamic counter-propulsive torque to the vehicle selected from the group consisting of an engine braking method, a transmission braking method, and an adding engine load method. 
     
     
         6 . The method of  claim 5 , wherein the engine braking method includes spark retarding or engine valve closure. 
     
     
         7 . The method of  claim 5 , wherein when the vehicle has an automatic transmission, the transmission braking method includes downshifting the automatic transmission. 
     
     
         8 . The method of  claim 5 , wherein when the vehicle has a shift-by-wire transmission the transmission braking method includes actuating a lower gear. 
     
     
         9 . The method of  claim 5 , wherein the adding engine load method includes engaging the air conditioning system of the vehicle. 
     
     
         10 . The method of  claim 5 , wherein the adding engine load method includes raising an alternator set point voltage of the vehicle. 
     
     
         11 . The method of  claim 1 , wherein a fourth transition braking mode of the plurality of transition braking modes comprises applying counter-propulsive force to the vehicle by using a shift-by-wire system to shift the vehicle into reverse or park.