Steer-by-wire system

• US 6,363,305 B1
• Filed: 09/18/2000
• Issued: 03/26/2002
• Est. Priority Date: 09/17/1999
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Byers, Michael D., Kaufmann, Timothy Wesley
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): MANCHO, RONNIE M
• Application Number:
  US09/666,497
• Time in Patent Office: 554 Days
• Field of Search: 701/41, 701/42, 701/43, 701/44, 701/33, 340/575, 340/465, 340/576, 303/139, 303/146, 303/191, 303/192, 332/031.8, 332/03, 180/402, 180/403, 180/444, 180/445, 180/446, 280/211, 280/5.51, 280/775, 280/779
• US Class Current: 701/41
• CPC Class Codes: B62D 5/001 Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

A closed loop steer by wire control system has three main components, a steering wheel unit, a roadwheel unit, and a master control unit. Signals generated by sensors in the steering wheel unit and roadwheel unit are passed back to the master control unit for processing. These signals include tie-rod force signals, and a steering wheel position signal. The master control unit uses these signals to calculate a steering wheel reaction torque signal which is sent back to the steering wheel unit to provide the operator with tactile feedback, while roadwheel command signals are sent to roadwheel units to provide steering direction. An Ackerman correction unit is also used to correct the left and right roadwheel positions to track about a common center.

Claims

1. A steer-by-wire control system comprising:

a master control unit;

at least one roadwheel unit electrically connected to said master control unit;

at least one steering wheel unit electrically connected to said master control unit;

a vehicle speed sensor for producing a vehicle speed signal, said vehicle speed sensor electrically connected to said master control unit;

wherein said at least one roadwheel unit includes a roadwheel position sensor and a least one tie rod sensor to produce and transmit a tie rod force signal;

wherein said at least one steering wheel unit includes a steering wheel position sensor to produce and transmit a steering wheel position signal;

wherein said master control unit calculates at least one roadwheel command signal in response to said tie rod force signal and said steering wheel position signal;

wherein said master control unit including a torque unit to calculate and produce a reaction torque signal in response to said tie-rod force signal and said vehicle speed signal; and

wherein said torque unit uses said tie rod force signal as an index to a plurality of torque look-up tables and blending the outputs thereof to generate a blended value.

2. The steer-by-wire control system of claim 1 wherein said look-up table outputs are blended in a ratio dependent upon said vehicle speed signal.

3. The steer-by-wire control system of claim 1 further comprising:

a position control unit, said position control unit calculates and produces a variable steering ratio signal in response to said steering wheel position signal and said vehicle speed signal.

4. The steer-by-wire control system of claim 3 wherein said variable steering ratio signal is calculated using said steering wheel position signal and said vehicle speed signal as inputs to a steering ratio look-up table.

5. The steer-by-wire control system of claim 3 wherein said position control unit further comprises a roadwheel command unit that calculates a theta correction and generates a theta corrected roadwheel command signal from said variable steering ratio signal and said steering wheel position signal.

6. The steer-by-wire control system of claim 3 wherein said position control unit calculates and produces at least one roadwheel command signal in response to said steering wheel position signal and said steering ratio signal.

7. The steer-by-wire control system of claim 6 wherein said position control unit further includes an Ackerman correction unit for producing a left roadwheel signal and a right roadwheel signal in response to said roadwheel command signal.

8. The steer-by-wire control system of claim 7 wherein said roadwheel unit includes a linear correction unit for calculating and producing a linear position command signal in response to a roadwheel command signal.

9. A method for controlling a vehicle comprising:

generating at least one tie-rod force signal;

generating a vehicle speed signal;

generating a steering wheel position signal;

combining said signals in a master control unit;

generating a steering wheel reaction torque signal in response to said tie rod force signal and said vehicle speed signal;

generating at least one roadwheel command signal in response to said steering wheel position signal and said vehicle speed signal;

calculating a first torque signal from a look-up table;

calculating a second torque signal from a second look-up table; and

calculating said steering wheel reaction torque signal as a blended value of said first and second torque signals.

10. A method for controlling a vehicle as in claim 9 comprising:

calculating and producing a variable steering ratio signal in response to said steering wheel position signal and said vehicle speed signal.

11. A method for controlling a vehicle as in claim 10 wherein:

said calculating and producing at least one roadwheel command signal is in response to said steering wheel position signal and said steering ratio signal.

12. A method for controlling a vehicle as in claim 11 comprising:

calculating an Ackerman correction factor;

modifying said roadwheel command signal with said Ackerman correction factor to adjust the vehicle wheels to track about a common center.

13. A method of controlling a vehicle as in claim 12 comprising:

calculating and producing a linear position command signal.

14. A method of controlling a vehicle as in claim 11 further comprising:

calculating and producing a left and right roadwheel command associated with the vehicles left and right roadwheel respectively.