Automatic power steering system

• US 6,170,600 B1
• Filed: 08/14/1997
• Issued: 01/09/2001
• Est. Priority Date: 09/05/1996
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Shimizu, Yasuo
• Primary Examiner(s): Hurley, Kevin
• Assistant Examiner(s): Fischer, Andrew J.
• Application Number:
  US08/911,452
• Time in Patent Office: 1,244 Days
• Field of Search: 180/443, 180/446, 180/167, 180/168, 180/169, 701/41, 701/42
• US Class Current: 180/446
• CPC Class Codes: B62D 1/28 non-mechanical , e.g. following a line or other known markers

Abstract

In an automatic power steering system incorporated with a power steering system and an automatic steering system, a continuous switching unit carries out a switch over between a power steering mode and an automatic steering mode in a continuous manner depending on the magnitude of the manual steering torque applied to the steering wheel. Thus, a smooth transition from one of the steering modes to the other can be accomplished without involving any absence of control.

Claims

1. A steering control system for a vehicle, comprising:

a steering mechanism;

a power steering control unit coupled to said steering mechanism, wherein said power steering control unit applies an assist steering torque output to said steering mechanism according to a magnitude of a manual steering effort;

an automatic steering control unit coupled to said steering mechanism, wherein said automatic steering control unit continuously adds an automatic steering torque output to said steering mechanism according to road information; and

a continuous switching unit coupled to said power steering control unit and to said automatic steering control unit, wherein said continuous switching unit continuously changes, according to the magnitude of said manual steering effort, weights of said assist steering torque output and said automatic steering torque output in an overall steering torque output applied to said steering mechanism.

2. A steering control system according to claim 1, further comprising a steering torque sensor coupled to said steering mechanism, said sensor measuring said manual steering effort.

3. A steering control system according to claim 1, wherein said power steering control unit comprises:

a steering torque detecting means for detecting a manual steering torque applied to a steering wheel;

an actuator for producing said assist steering torque; and

a first target drive torque determining unit, said first target drive torque determining unit determining said assist steering torque according to a magnitude of said manual steering torque.

4. A steering control system according to claim 3, wherein said automatic steering control unit comprises:

a road configuration detecting unit detecting a configuration of a road on which the vehicle is traveling;

a target dynamic variable determining unit coupled to said road configuration detecting unit, said target dynamic variable determining unit determining a target dynamic variable for the vehicle according to an output from said road configuration detecting unit; and

a second target drive torque determining unit coupled to said target dynamic variable determining unit, said second target drive torque determining unit determining said automatic steering torque which is to be produced by said actuator according an output from said target dynamic variable determining unit.

5. A steering control system according to claim 4, wherein said continuous switching unit comprises:

an actual dynamic variable detecting unit measuring an actual value of said dynamic variable;

an estimated dynamic variable computing unit computing a hypothetical dynamic variable which would be produced when an output of said second target drive torque determining unit is applied to said steering mechanism; and

a dynamic variable weighting unit coupled to said actual dynamic variable detecting unit and to said estimated dynamic variable computing unit, said dynamic variable weighting unit weighting an output of said estimated dynamic variable computing unit and an output of said actual dynamic variable detecting unit according to an output of said steering torque detecting means;

wherein an output of said dynamic variable weighting unit is deducted from the output of said target dynamic variable determining unit to produce a difference output and said difference output is applied to said second target drive torque determining unit.

6. A steering control system according to claim 5, wherein said dynamic variable comprises a yaw rate of said vehicle.

7. A steering control system according to claim 5, wherein said dynamic variable comprises a lateral acceleration of said vehicle.

8. A steering control system according to claim 5, wherein said dynamic variable comprises a steering angle of a steerable wheel of said vehicle.

9. A steering control system for a vehicle comprising:

a steering mechanism;

a power steering control unit coupled to said steering mechanism, wherein said power steering control unit applies an assist steering torque output to said steering mechanism according to a magnitude of a manual steering effort;

an automatic steering control unit coupled to said steering mechanism and including a road configuration detecting unit, wherein said road configuration detecting unit detects a configuration of a road on which the vehicle is traveling, and wherein said automatic steering control unit continuously adds an automatic steering torque output to said steering mechanism according to road information; and

a continuous switching unit coupled to said power steering control unit and to said automatic steering control unit, wherein said continuous switching unit continuously changes, according to the magnitude of said manual steering effort, weights of said assist steering torque output and said automatic steering torque output in an overall steering torque output applied to said steering mechanism.

10. A steering control system according to claim 9, further comprising a steering torque sensor coupled to said steering mechanism, said sensor measuring said manual steering effort.

11. A steering control system according to claim 9, wherein said power steering control unit comprises:

a steering torque detecting unit for detecting a manual steering torque applied to a steering wheel;

an actuator for producing said assist steering torque; and

a first target drive torque determining unit, said first target drive torque determining unit determining said assist steering torque according to a magnitude of said manual steering torque.

12. A steering control system according to claim 11, wherein said automatic steering control unit further includes a target dynamic variable determining unit coupled to said-road configuration detecting unit, said target dynamic variable determining unit determining a target dynamic variable for the vehicle according to an output from said road configuration detecting unit, and a second target drive torque determining unit coupled to said target dynamic variable determining unit, said second target drive torque determining unit determining said automatic steering torque which is to be produced by said actuator according an output from said target dynamic variable determining unit.

13. A steering control system according to claim 12, wherein said continuous switching unit comprises:

an actual dynamic variable detecting unit measuring an actual value of said dynamic variable;

an estimated dynamic variable computing unit computing a hypothetical dynamic variable which would be produced when an output of said second target drive torque determining unit is applied to said steering mechanism; and

a dynamic variable weighting unit coupled to said actual dynamic variable detecting unit and to said estimated dynamic variable computing unit, said dynamic variable weighting unit weighting an output of said estimated dynamic variable computing unit and an output of said actual dynamic variable detecting unit according to an output of said steering torque detecting unit,

wherein an output of said dynamic variable weighting unit is deducted from the output of said target dynamic variable determining unit and applied to said second target drive torque determining unit.

14. A steering control system according to claim 13, wherein said dynamic variable comprises a yaw rate of said vehicle.

15. A steering control system according to claim 13, wherein said dynamic variable comprises a lateral acceleration of said vehicle.

16. A steering control system according to claim 13, wherein said dynamic variable comprises a steering angle of a steerable wheel of said vehicle.

17. A vehicle steering control system comprising:

a vehicle steering mechanism;

a power steering control unit coupled to the steering mechanism;

an automatic steering control unit coupled to the steering mechanism;

a continuous switching unit coupled to the automatic steering control unit; and

a dynamic variable weighted output that is output from the continuous switching unit to the automatic steering control unit, wherein the weighted output includes a first output associated with a detected value of a dynamic variable of the vehicle and a second output associated with an estimated value of the dynamic variable, and wherein the weights of the first and second outputs in the weighted output are continuously varied according to a magnitude of a manual steering effort.

18. The system of claim 17, wherein the dynamic variable comprises a yaw rate of the vehicle.

19. The system of claim 17, wherein the dynamic variable comprises a lateral acceleration of the vehicle.

20. The system of claim 17, wherein the dynamic variable comprises a steering angle of a steerable wheel of the vehicle.

21. The system of claim 17, wherein the power steering control unit comprises:

a first target drive torque determining unit coupled to the steering mechanism;

a steering torque sensor coupled to the first target drive torque determining unit and to the continuous switching unit;

a first target drive torque output that is output from the first target drive torque determining unit to the steering mechanism; and

a steering torque output associated with the magnitude of the manual steering effort, wherein the steering torque output is output from the steering torque sensor to the first target drive torque determining unit and to the continuous switching unit.

22. The system of claim 17, wherein the automatic steering control unit comprises:

a second target drive torque determining unit coupled to the steering mechanism;

a second target drive torque output that is output from the second drive torque determining unit to the steering mechanism;

a target dynamic variable determining unit coupled to the second target drive torque determining unit;

a target dynamic variable output that is output to the second target drive torque determining unit; and

a road configuration detecting unit coupled to the target dynamic variable determining unit.

23. The system of claim 17, wherein the continuous switching unit comprises:

a dynamic variable weighting unit coupled to the automatic steering control system, wherein the dynamic variable weighting unit outputs the dynamic variable weighted output to the automatic steering control system;

an actual dynamic variable detecting unit coupled to the dynamic variable weighting unit, wherein the actual dynamic variable detecting unit outputs the first output to the dynamic variable weighting unit; and

an estimated dynamic variable computing unit coupled to the dynamic variable weighting unit, wherein the estimated dynamic variable computing unit outputs the second output to the dynamic variable weighting unit.

24. The system of claim 17 further comprising:

a second target drive torque determining unit coupled to the steering mechanism;

a dynamic variable weighting unit coupled to the second target drive torque determining unit, wherein the dynamic variable weighting unit outputs the dynamic variable weighted output to the second target drive torque determining unit;

an actual dynamic variable detecting unit coupled to the dynamic variable weighting unit, wherein the actual dynamic variable detecting unit outputs the first output to the dynamic variable weighting unit; and

an estimated dynamic variable computing unit coupled to the dynamic variable weighting unit and to the second target drive torque determining unit, wherein the estimated dynamic variable computing unit outputs the second output to the dynamic variable weighting unit; and

a second target drive torque output that is output from the second drive torque determining unit to the steering mechanism and to the estimated dynamic variable computing unit.

25. The system of claim 24 further comprising:

a target dynamic variable determining unit coupled to the second target drive torque determining unit;

a target dynamic variable output that is output to the second target drive torque determining unit; and

a road configuration detecting unit coupled to the target dynamic variable determining unit.

26. The system of claim 25, wherein the road configuration detecting unit comprises a global positioning system (GPS) car navigation system and map information stored in the GPS system.

27. The system of claim 25 wherein the dynamic variable weighted output is deducted from the target dynamic variable output.

28. The system of claim 27, wherein the dynamic variable comprises a yaw rate of the vehicle.

29. The system of claim 27, wherein the dynamic variable comprises a lateral acceleration of the vehicle.

30. The system of claim 27, wherein the dynamic variable comprises a steering angle of a steerable wheel of the vehicle.