DC torque motor actuated anti-lock brake controller

Abstract

A wheel lock control system is described for a wheel braking system that includes a motor driven actuator for applying controlled hydraulic brake pressure to the wheel brake that is determined by motor current. The motor current corresponding to the brake pressure producing the maximum possible braking effort during each brake pressure application is identified and a value related thereto is reapplied to the motor after an incipient wheel lockup condition is sensed.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value proportional to the value of the motor current;   means for determining the tire torque tending to accelerate the wheel during the application of brake pressure;   means for storing the value of motor current corresponding to the maximum determined value of tire torque;   means for detecting an incipient wheel lockup condition; and   means for establishing the motor current following a detected incipient wheel lockup condition at a value having a predetermined relationship to the stored value of motor current to control the brake pressure at a predetermined braking condition.   
     
     
       2. A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value proportional to the value of the motor current;   means for determining the tire torque tending to accelerate the wheel during the application of brake pressure;   means for storing the value of motor current corresponding to the maximum determined value of tire torque during periods of application of brake pressure;   means for detecting an incipient wheel lockup condition;   means for decreasing the motor current in response to a detected incipient wheel lockup condition to allow wheel speed recovery; and   means for reestablishing the motor current following wheel speed recovery to a value having a predetermined relationship to the stored value of motor current.   
     
     
       3. A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value proportional to the value of the motor current;   means for determining the tire torque tending to accelerate the wheel during the application of brake pressure;   means for storing the value of motor current corresponding to the maximum determined value of tire torque during the application of brake pressure;   means for detecting an incipient wheel lockup condition; and   means for establishing the motor current following a detected incipient wheel lockup condition to a value that is a predetermined fraction of the stored value of motor current to control the brake pressure which establishes substantially the maximum possible braking force. .Iadd.   
     
     
       4.  A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a motor for controlling the applied brake pressure;   means for detecting an incipient wheel lockup condition;   means for storing the value of a motor condition related to the applied brake pressure substantially at the time an incipient wheel lockup condition is detected;   means for controlling the motor in response to a detected incipient wheel lockup condition to release brake pressure to allow wheel speed recovery; and   means for reestablishing the motor condition following wheel speed recovery to a value having a predetermined relationship to the stored value of the motor condition..Iaddend. .Iadd.5. A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising:   an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a motor for controlling the applied brake pressure;   means for detecting an incipient wheel lockup condition;   means for storing the value of a motor condition related to the applied brake pressure corresponding to a predetermined braking condition between the wheel and the road surface;   means for controlling the motor in response to a detected incipient wheel lockup condition to release brake pressure to allow wheel speed recovery;   means for reestablishing the motor condition following wheel speed recovery to a value having a predetermined relationship to the stored value of the motor condition; and   means for controlling the motor following the establishment of the motor condition to increase brake pressure until an incipient wheel lockup   
     
     
        condition is again detected..Iaddend. .Iadd.6.  A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value related to the value of the motor current;   means for detecting an incipient wheel lockup condition;   means for storing a value of motor current substantially at the time an incipient wheel lockup condition is detected;   means for decreasing the motor current in response to a detected incipient wheel lockup condition to allow wheel speed recovery; and   means for reestablishing the motor current following wheel speed recovery to a value having a predetermined relationship to the stored value of   
     
     
        motor current..Iaddend. .Iadd.7.  A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor current;   means for detecting an incipient wheel lockup condition;   means for storing a value of motor current corresponding to a predetermined braking condition between the wheel and the road surface;   means for decreasing the motor current in response to a detected incipient wheel lockup condition to allow wheel speed recovery; and   means for reestablishing the motor current following wheel speed recovery to a value having a predetermined relationship to the stored value of   
     
     
        motor current..Iaddend. .Iadd.8.  A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising: an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value related to the value of the motor current;   means for detecting an incipient wheel lockup condition;   means for storing a value of motor current corresponding to the brake pressure establishing a critical slip between the wheel and the road surface;   means for decreasing the motor current in response to a detected incipient wheel lockup condition to allow wheel speed recovery; and   means for reestablishing the motor current following wheel speed recovery to a value having a predetermined relationship to the stored value of motor current..Iaddend. .Iadd.9. A wheel lock control system for limiting the brake pressure applied to the brake of a vehicle wheel traveling over a road surface, the system comprising:   an actuator for controlling the brake pressure to the brake of the wheel, the actuator including a torque motor for generating a motor torque in response to motor current to control the applied brake pressure in accordance with the value of the motor torque, the motor torque having a value related to the value of the motor current;   means for detecting an incipient wheel lockup condition;   means for storing a value of motor current corresponding to the brake pressure establishing a critical slip between the wheel and the road surface;   means for decreasing the motor current in response to a detected incipient wheel lockup condition to allow wheel speed recovery;   means for reestablishing the motor current following wheel speed recovery to a value having a predetermined relationship to the stored value of motor current; and   means for ramping the motor current following the establishment of the motor current in direction to increase brake pressure until an incipient wheel lockup condition is again detected..Iaddend.