Brake system with adaptive offset compensation

• US 5,362,135 A
• Filed: 02/14/1994
• Issued: 11/08/1994
• Est. Priority Date: 02/14/1994
• Status: Expired due to Term

• Current Assignee: BWI Company Limited SA (Shougang Corporation)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Littlejohn, Deron C., Riddiford, Bryan P.
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US08/195,242
• Time in Patent Office: 267 Days
• Field of Search: 303/3, 303/20, 303/91-112, 303/2, 303/15-18, 303/13-14, 303/115.2, 303/50-56, 303/113.4, 303/9.61, 303/9.62, 303/9.71, 303/DIG. 1, 303/DIG. 2 , 303/DIG. 3, 303/DIG. 4, 74/512, 74/513, 74/514, 180/197, 180/165, 180/65.1-65.8, 318/375, 318/376, 188/162, 188/156, 188/161, 188/158, 188/159, 188/163, 188/106 P, 188/106.F, 188/181 T, 188/152, 364/426.01, 364/426.02, 364/426.03
• US Class Current: 303/3
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/429 Current
• CPC Class Codes: B60L 2240/80 Time limits
• CPC Class Codes: B60L 2250/26 by pedal actuation
• CPC Class Codes: B60L 3/0061 relating to electrical machines
• CPC Class Codes: B60L 3/0076 relating to braking
• CPC Class Codes: B60L 3/0084 relating to control modules
• CPC Class Codes: B60L 3/108 whilst braking, i.e. ABS
• CPC Class Codes: B60L 7/12 for vehicles propelled by dc motors
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60L 7/26 Controlling the braking effect
• CPC Class Codes: B60T 13/586 the retarders being of the electric type
• CPC Class Codes: B60T 13/66 Electrical control in fluid-pressure brake systems
• CPC Class Codes: B60T 13/70 by fluid-controlled switches
• CPC Class Codes: B60T 13/741 acting on an ultimate actuator
• CPC Class Codes: B60T 2270/602 ABS features related thereto
• CPC Class Codes: B60T 8/267 for hybrid systems with different kind of brakes on different axles
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y10S 303/03 : Electrical pressure sensor

Abstract

In a vehicle brake system having braking control responsive to a pressure signal from a pressure transducer in a hydraulic brake line, a method of operation comprising the steps of: (a) determining whether a brake pedal is depressed; (b) when the brake pedal is determined to be depressed: (i) controlling the brake system responsive to the pressure signal and a stored offset value for the pressure transducer, and (ii) resetting a timer; (c) when the brake pedal is determined to be not depressed: (i) cycling the timer, (ii) determining whether the timer has timed out, and (iii) if the timer has timed out, (iii.i) receiving the pressure signal from the pressure transducer, (iii.ii) comparing the pressure signal to a predetermined limit value indicative of an acceptable maximum sensor output when the pedal is not depressed, and (iii.iii) updating the stored offset value responsive to the pressure signal.

Claims

1. In a vehicle brake system having braking control responsive to a pressure signal from a pressure transducer in a hydraulic brake line, a method of operation comprising the steps of:

(a) determining whether a brake pedal is depressed;

(b) when the brake pedal is determined to be depressed;

(i) controlling the brake system responsive to the pressure signal and a stored offset value for the pressure transducer, and

(ii) resetting a timer;

(c) when the brake pedal is determined to be not depressed;

(i) cycling the timer,

(ii) determining whether the timer has timed out, and

(iii) if the timer has timed out, (iii.i) receiving the pressure signal from the pressure transducer, (iii.ii) comparing the pressure signal to a predetermined limit value indicative of an acceptable maximum sensor output when the pedal is not depressed, and (iii.iii) updating the stored offset value responsive to the pressure signal.

2. In a vehicle brake system comprising a depressible brake pedal, at least one hydraulic brake line and at least one pressure sensor providing an outputs signal responsive to a pressure in the hydraulic line, a method of controlling the brake system comprising the steps of:

determining whether a brake pedal is depressed;

if the brake pedal is depressed, controlling the brake system responsive to the output signal and a stored offset value representative of an offset of the sensor;

if the brake pedal is not depressed, thereafter

determining if the brake pedal has not been depressed for a predetermined time limit;

if the brake pedal has not been depressed for a predetermined time limit, updating the stored offset responsive to the sensor output signal.

3. In a vehicle brake system comprising a depressible brake pedal, at least one hydraulic brake line and at least one pressure sensor providing an output signal responsive to a pressure in the hydraulic line, a method of controlling the brake system comprising the steps of:

determining whether a brake pedal is depressed;

if the brake pedal is depressed, controlling the brake system responsive to the output signal and a stored offset value representative of an offset of the sensor;

if the brake pedal is not depressed, thereafter

determining if the brake pedal has not been depressed for a predetermined time limit;

if the brake pedal has not been depressed for a predetermined time limit and the sensor output signal is within a predetermined range indicative of an acceptable range of output values for the sensor when the pedal is not depressed, updating the stored offset responsive to the sensor output signal, wherein the offset for the pressure sensor in the brake system is continuously updated and is adaptive to sensor aging and the vehicle environment.

4. A vehicle brake system comprising:

a depressible brake pedal;

at least one hydraulic brake line;

at least one pressure sensor providing an output signal responsive to a pressure in the hydraulic line;

a brake actuator responsive to a brake command to command friction braking of the vehicle at a braking torque indicated by the brake command;

a brake controller coupled to the pressure sensor and to the brake actuator comprising

(a) means for determining whether the brake pedal is depressed;

(b) means for determining the brake command when the brake pedal is determined to be depressed, wherein the brake command is determined responsive to the output signal and a stored offset value for the pressure sensor;

(c) means for applying the brake command to the brake actuator;

(d) means for determining whether the brake pedal has not been depressed for a predetermined time period and

(e) means for updating the offset value when the brake pedal is determined to have been not depressed for the predetermined time period, wherein the means for updating the offset value comprises means for receiving the output signal, means for comparing the output signal to a predetermined limit, and means for storing the received output signal in memory as the updated offset value,

wherein the brake unit adaptively updates the sensor output signal, compensating for sensor aging and environmental conditions of the vehicle.