Method of and apparatus for estimating surface friction

• US 5,394,329 A
• Filed: 04/27/1993
• Issued: 02/28/1995
• Est. Priority Date: 04/28/1992
• Status: Expired due to Fees

• Current Assignee: Lucas Industries Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Lucas Industries Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Bridgens, Barry J.
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/053,590
• Time in Patent Office: 672 Days
• Field of Search: 364/426.01, 364/426.03, 364/426.02, 180/197, 303/95, 303/97, 303/109, 303/113.2, 73/9, 73/529, 73/534
• US Class Current: 701/70
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2270/211 Setting or adjusting start-control threshold
• 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 8/175 Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control safety devices for propulsion unit control responsive to, or preventing, skidding of wheels B60K28/16
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems

Abstract

Measurements of wheel speed are compared to detect excessive wheel spin. An output of the wheel spin detector is supplied to a drive reducing device for reducing vehicle drive engine output in response to detection of excessive wheel spin. The reduced vehicle drive engine output is compared with a predetermined value by a subtracter. An estimate of surface friction is updated with a value dependent upon the output of the subtracter.

Claims

1. An apparatus for estimating surface friction during operation of a wheeled vehicle having an engine, said apparatus comprising:

detecting means for detecting excessive wheel spin;

drive reducing means for reducing engine output in response to detection of excessive wheel spin;

comparing means arranged to form a difference between the reduced engine output and a predetermined value; and

updating means for updating a surface friction estimate by adding to the surface friction estimate a value corresponding to the difference between the reduced engine output and the predetermined value.

2. An apparatus as claimed in claim 1, in which the value added to the surface friction estimate is proportional to the difference between the reduced engine output and the predetermined value.

3. An apparatus as claimed in claim 1, further comprising averaging means for periodically averaging the reduced engine output to provide an averaged reduced engine output, and wherein said comparing means is arranged to compare the average reduced engine output with the predetermined value.

4. An apparatus as claimed in claim 1, in which said updating means is arranged to periodically update the surface friction estimate as long as said drive reducing means reduces engine output.

5. A method of estimating surface friction during operation of a wheeled vehicle having an engine, comprising the steps of:

detecting excessive wheel spin;

reducing engine output in response to detected excessive wheel spin;

forming a difference between the reduced engine output and a predetermined value; and

updating a surface friction estimate by adding to the surface friction estimate a value corresponding to the difference between the reduced engine output and the predetermined value.