Patents by Inventor David Alan Thatcher
David Alan Thatcher has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Patent number: 6895322Abstract: An improved ABS control method incorporates entry criteria for initiating ABS control based on brake pedal position and rate of depression, adaptively adjusted by a reference pedal position corresponding to a predefined vehicle deceleration. A periodically-updated characterization of the relationship between brake pedal position and vehicle deceleration is used to establish the reference brake pedal position, and when insipient wheel lock is detected, the initiation of ABS control is delayed by an entry delay period that decreases with increasing rate of pedal depression and with the degree to which the pedal position exceeds the reference pedal position. In this way, the entry conditions are predicated primarily on the manner of brake pedal depression, with adaptive adjustment for variations in braking effectiveness.Type: GrantFiled: October 15, 2001Date of Patent: May 17, 2005Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6859712Abstract: An improved anti-lock control method for a vehicle brake system identifies various factors that degrade the effectiveness of the brake system and adaptively adjusts a brake apply rate during anti-lock brake control to compensate for the identified degradation so that the optimal tractive force during anti-lock brake control is more nearly realized. The identified factors include fading due to brake heating, hydraulic leakage, mis-adjusted and non-releasing rear brakes, brake wear and excessive vehicle weight.Type: GrantFiled: August 31, 2001Date of Patent: February 22, 2005Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6728621Abstract: A method and apparatus for operating a vehicle anti-lock braking system includes a brake pedal and a brake modulator that reduces braking pressure by an initial pressure reduction after detecting insipient wheel lock. Vehicle deceleration is measured as a function of brake pedal position. A first table is updated with the vehicle deceleration and the brake pedal position. A coefficient of friction of a road surface is estimated based on the first table. A slip target for at least one wheel is estimated and is based on an estimated maximum slip of the at least one wheel before losing traction minus an estimated potential for vehicle rollover. A deceleration target for at least one wheel is estimated and is based on an estimated maximum deceleration of the at least one wheel before losing traction minus the estimated potential for vehicle rollover.Type: GrantFiled: October 4, 2002Date of Patent: April 27, 2004Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Publication number: 20040068358Abstract: A method and apparatus for operating a vehicle anti-lock braking system includes a brake pedal and a brake modulator that reduces braking pressure by an initial pressure reduction after detecting insipient wheel lock. Vehicle deceleration is measured as a function of brake pedal position. A first table is updated with the vehicle deceleration and the brake pedal position. A coefficient of friction of a road surface is estimated based on the first table. A slip target for at least one wheel is estimated and is based on an estimated maximum slip of the at least one wheel before losing traction minus an estimated potential for vehicle rollover. A deceleration target for at least one wheel is estimated and is based on an estimated maximum deceleration of the at least one wheel before losing traction minus the estimated potential for vehicle rollover.Type: ApplicationFiled: October 4, 2002Publication date: April 8, 2004Inventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6704635Abstract: A vehicle anti-lock braking system includes a brake pedal and a brake modulator. The brake system reduces braking pressure by an initial pressure reduction after detecting insipient wheel lock. Vehicle deceleration is measured as a function of brake pedal position. A first table is updated with the vehicle deceleration and the brake pedal position. A coefficient of friction of a road surface is estimated based on the first table. Wheel slip and deceleration target thresholds are determined based on the coefficient of friction. The wheel slip and deceleration target thresholds are used to populate a command table for the anti-lock braking system. Brake heat, brake torque, vehicle weight and grade are estimated. Release and apply pressures are calculated from an adjusted coefficient of friction, a coefficient of friction and the grade.Type: GrantFiled: June 26, 2002Date of Patent: March 9, 2004Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Publication number: 20040002804Abstract: A vehicle anti-lock braking system includes a brake pedal and a brake modulator. The brake system reduces braking pressure by an initial pressure reduction after detecting insipient wheel lock. Vehicle deceleration is measured as a function of brake pedal position. A first table is updated with the vehicle deceleration and the brake pedal position. A coefficient of friction of a road surface is estimated based on the first table. Wheel slip and deceleration target thresholds are determined based on the coefficient of friction. The wheel slip and deceleration target thresholds are used to populate a command table for the anti-lock braking system. Brake heat, brake torque, vehicle weight and grade are estimated. Release and apply pressures are calculated from an adjusted coefficient of friction, a coefficient of friction and the grade.Type: ApplicationFiled: June 26, 2002Publication date: January 1, 2004Inventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6553304Abstract: An improved anti-lock brake control method in which the brake pressure reduction initiated upon detection of insipient wheel lock is adaptively determined based on a periodically updated characterization of the relationship between brake pedal position and vehicle deceleration. The brake torque and vehicle weight are estimated based on the characterization data, corrected for variation in brake heating, and used to compute the surface coefficient of friction, which in turn, is used to schedule the initial anti-lock brake pressure reduction for optimal braking system performance.Type: GrantFiled: June 18, 2001Date of Patent: April 22, 2003Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Publication number: 20030074126Abstract: An improved ABS control method incorporates entry criteria for initiating ABS control based on brake pedal position and rate of depression, adaptively adjusted by a reference pedal position corresponding to a predefined vehicle deceleration. A periodically-updated characterization of the relationship between brake pedal position and vehicle deceleration is used to establish the reference brake pedal position, and when insipient wheel lock is detected, the initiation of ABS control is delayed by an entry delay period that decreases with increasing rate of pedal depression and with the degree to which the pedal position exceeds the reference pedal position. In this way, the entry conditions are predicated primarily on the manner of brake pedal depression, with adaptive adjustment for variations in braking effectiveness.Type: ApplicationFiled: October 15, 2001Publication date: April 17, 2003Inventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Publication number: 20030045989Abstract: An improved anti-lock control method for a vehicle brake system identifies various factors that degrade the effectiveness of the brake system and adaptively adjusts a brake apply rate during anti-lock brake control to compensate for the identified degradation so that the optimal tractive force during anti-lock brake control is more nearly realized. The identified factors include fading due to brake heating, hydraulic leakage, mis-adjusted and non-releasing rear brakes, brake wear and excessive vehicle weight.Type: ApplicationFiled: August 31, 2001Publication date: March 6, 2003Inventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6513886Abstract: A brake system control method for use in a vehicle in which wheel speed normalization factors are iteratively updated, comprising the steps of: monitoring a plurality of wheel speed signals from a plurality of wheel speed sensors; determining for each wheel a wheel acceleration responsive to the wheel speed signal; determining an acceleration dead band for each wheel, wherein the acceleration dead band is proportional to a measure of vehicle acceleration; comparing the wheel acceleration to the dead band; and if the magnitude of the wheel acceleration is greater than the magnitude of the dead band, inhibiting update of the normalization factors.Type: GrantFiled: May 7, 1996Date of Patent: February 4, 2003Assignee: General Motors CorporationInventors: John Andrew Weber, Alfred Russell Robertson, Kevin Gerard Leppek, Alexander Kade, Allen John Walenty, David Alan Thatcher
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Publication number: 20020193931Abstract: An improved anti-lock brake control method in which the brake pressure reduction initiated upon detection of insipient wheel lock is adaptively determined based on a periodically updated characterization of the relationship between brake pedal position and vehicle deceleration. The brake torque and vehicle weight are estimated based on the characterization data, corrected for variation in brake heating, and used to compute the surface coefficient of friction, which in turn, is used to schedule the initial anti-lock brake pressure reduction for optimal braking system performance.Type: ApplicationFiled: June 18, 2001Publication date: December 19, 2002Applicant: GENERAL MOTORS CORPORATIONInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 6405117Abstract: An improved method of diagnosing conditions of a vehicle braking system that degrade the braking effectiveness informs the driver of the condition so that repair or adjustment can be timely made. The relationship between brake pedal position and vehicle deceleration is determined during a calibration interval to construct a calibration table of brake effectiveness, and then periodically over the life of the braking system to develop a current brake effectiveness table. Braking system abnormalities that impair the braking effectiveness are diagnosed by analyzing the table values.Type: GrantFiled: June 21, 2001Date of Patent: June 11, 2002Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher
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Patent number: 5646848Abstract: A method of brake control, comprising the steps of: determining a deceleration of a vehicle; measuring a first wheel rotational velocity of a front wheel of the vehicle; measuring a second wheel rotational velocity of a rear wheel of the vehicle; determining a front wheel normalization value responsive to the deceleration and a front tire deformation constant; determining a rear wheel normalization value responsive to the deceleration and a rear tire deformation constant; determining a front normalized wheel rotational velocity responsive to the front wheel normalization value and the first wheel rotational velocity, wherein the front normalized wheel rotational velocity is responsive to a front tire deformation that occurs during a braking maneuver of the vehicle; determining a rear normalized wheel rotational velocity responsive to the rear wheel normalization value and the second wheel rotational velocity, wherein the rear normalized wheel rotational velocity is responsive to a rear tire deformation that oType: GrantFiled: August 9, 1995Date of Patent: July 8, 1997Assignee: General Motors CorporationInventors: Allen John Walenty, Kevin Gerard Leppek, David Alan Thatcher