Vehicle steering system and method for controlling vehicle direction through differential braking of left and right road wheels

• US 6,021,367 A
• Filed: 08/24/1994
• Issued: 02/01/2000
• Est. Priority Date: 08/24/1994
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Ulsoy, Ali Galip, Pilutti, Thomas Edward, Hrovat, Davorin David
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/295,194
• Time in Patent Office: 1,987 Days
• Field of Search: 364/426.01, 364/426.02, 364/424.05, 364/447, 364/559, 364/561, 303/93, 303/97, 303/100, 303/99, 303/104, 303/107, 303/146, 180/197, 180/79.1, 180/141, 180/142, 180/153, 180/411, 701/70, 701/71, 701/41
• US Class Current: 701/41
• CPC Class Codes: B60T 2270/313 with less than three sensors (yaw rate, steering angle, lateral acceleration)
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60T 8/246 Change of direction
• CPC Class Codes: B60T 8/4827 in hydraulic brake systems

Abstract

A vehicle steering system in which brake steering forces intervene in the manual steering function wherein brake steering can be used to control the lateral position of a vehicle to supplement manual steering efforts, the system including brake controls for wheel brakes at the left and right sides of the vehicle which develop differential brake forces that result in a change in vehicle lateral position, the lateral position that is developed forming an input for a feedback regulator and brake controller, the magnitude of lateral position errors determining the brake forces that affect yaw rate and lateral position.

Claims

1. A differential braking system for an automotive vehicle for road use having road wheels including driver-controlled dirigible road-wheels and vehicle wheel brakes including driver-activated brake controls and means for controlling said dirigible wheels to effect a desired steering angle that results in a lateral position designated by the driver, the vehicle having a center of gravity between said wheel brakes and having means for detecting actual lateral position of said vehicle relative to said road;

means for computing braking forces at each of said wheels when said wheel brakes are activated and for determining the difference in said braking forces,

means for computing a yaw moment as a function of said difference in said braking forces;

means for computing rate of change of yaw and for computing lateral vehicle acceleration required to effect lateral tire force to change actual lateral position of said vehicle including means for computing cornering tire forces on said dirigible wheels as a function of said rate of change of yaw; and

means for comparing actual lateral position with said designated lateral position determined by said steering angle to create a lateral position error signal, and brake actuator means for activating said wheel brakes in response to said error signal independently of said driver-activated brake controls whereby differential braking forces are developed to effect steering intervention that complements driver steering of said driver controlled dirigible road wheels.

2. The system set forth in claim 1 wherein said vehicle has front and rear sets of road wheels, said front wheels being driver-controlled dirigible wheels, at least one of said road wheel sets being vehicle traction wheels, each wheel set having left and right driver activated wheel brakes;

said means for computing braking forces comprising means for computing braking forces at each wheel when said vehicle wheel brakes are activated.

3. A method for effecting brake steering of an automotive vehicle for road use and having traction road wheels, driver-controlled dirigible road wheels, driver-activated road wheel brakes including driver-activated brake controls, means for controlling said dirigible wheels to effect a desired steering angle that results in a lateral position and means for detecting actual lateral position of said vehicle relative to said road designated by the driver;

said method including the steps of computing braking forces at each of said road wheels when said brakes are applied;

comparing actual lateral position to said designated lateral position determined by said steering angle to create a lateral position error signal;

activating said driver-activated wheel brakes in response to said error signal independently of said driver-activated brake controls;

computing yaw moment as a function of the difference in said braking forces;

computing rate of change of yaw and computing lateral vehicle acceleration required to change said actual lateral position of said vehicle including the step of computing cornering tire forces on said dirigible wheels as a function of the rate of change of yaw whereby braking forces are developed to effect steering intervention that complements driver steering of said driver-activated dirigible road wheels.