Additional fallback level for the failure of, for example, angle sensors, for steer-by-wire systems not having a mechanical/hydraulic fallback connection

• US 20020033301A1
• Filed: 09/04/2001
• Published: 03/21/2002
• Est. Priority Date: 09/20/2000
• Status: Active Grant

• Current Assignee: Thyssenkrupp Presta Steertec GmbH (Thyssenkrupp AG)
• Original Assignee: Thyssenkrupp Presta Steertec GmbH (Thyssenkrupp AG)
• Inventors: Clephas, Bernd
• Granted Patent: US 6,755,276 B2
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/003 Backup systems, e.g. for manual steering B62D5/30 takes precedence
• CPC Class Codes: B62D 5/006 power actuated
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown

Abstract

The invention relates to a power-assisted steering system for non-trackborne vehicles and particularly motor vehicles, having a steering control (e.g. a steering wheel) operated by the driver, a wheel angle positioner to steer the wheels of the vehicle, angle sensors to sense the position of the steering control and/or the wheels of the vehicle, a “feel” provider to generate a “feel” torque to simulate a feedback of force to the steering control, the “feel” provider having an electric motor, at least one control unit for controlling the wheel angle positioner and the “feel” provider, in which in the event of at least one angle sensor, the at least one control unit and/or the “feel” provider failing, the angle to which the steering control is turned is continuously determined from the voltage which is induced in at least one winding of the electric motor by turning the steering control manually and/or from the induced current, and is used to control the steering angle at the wheels of the vehicle.

Claims

1. A power-assisted steering system for a non-trackborne vehicle having wheels, said system comprising:

a steering control operated by a driver,

a wheel angle positioner to steer the wheels,

angle sensors to sense the position of the steering control and/or the wheels,

a feel provider to generate a feel torque to simulate a feedback of force to the steering control, the feel provider having an electric motor with at least one winding,

at least one control unit for controlling the wheel angle positioner and feel provider,

wherein in the event of failure of one or more of the group selected from the at least one angle sensor, the at least one control unit and the feel provider, the angle to which the steering control is turned is continuously determined from a voltage which is induced in the at least one winding by turning the steering control manually and/or from the induced current, and is used to control the steering angle.

2. The power-assisted steering system according to claim 1,

wherein the terminal or source voltage(s) (EMF) which can be picked off from the terminals of the at least one winding is used to determine or estimate the angle of the steering control and/or its angular velocity.

3. The power-assisted steering system according to claim 2,

wherein a resistor is connected to each of the terminals of the at least one winding.

4. The power-assisted steering system according to claim 1, wherein the approximate angle of the steering control is determined starting from the last valid angle for the steering control determined by means of the angle sensors.

5. The power-assisted steering system according to claim 4, wherein the change in the angle of the steering control is calculated from the equation

Δ

φ

=a*_t1∫

^t2Udt=a*[U(t₂)−

U(t₁)]

(wherein the source voltage values U(t₂) and U(t₁) are within a presettable range).

6. The power-assisted steering system according to claim 5 wherein a change in angle of Δ

φ

=0 is set for source voltage values below a given threshold voltage.

7. The power-assisted steering system according to claim 2 wherein for source voltage values of different sizes different constants of proportionality as are used to calculate the change in the angle of the steering control.

8. The power-assisted steering system according to claim 1 wherein the electric motor is a commutator motor or a DC motor.

9. The power-assisted steering system according to claim 8 wherein the electric motor is a commutator motor and the passages through zero of the terminal voltages from the windings are monitored to allow the change in the angle of the steering control to be calculated.

10. The power-assisted steering system according to claim 9,

wherein when a first terminal voltage passes through zero, the source voltage and the direction of rotation of the steering control is determinable from the difference between the other terminal voltages and the sign of the other terminal voltages and/or the nature of the passage through zero.

11. The power-assisted steering system according to claim 1, wherein in calculating the virtual position of the steering control, full lock for the wheels is simulated by allowing the value calculated for the angle of the steering control only to lie within specified limits.

12. The power-assisted steering system according to claim 1, wherein as soon as the angle sensors for the steering control are again supplying valid values, the difference between a valid angle sensor value and the position of the steering control which had been determined by computation up to that point is allowed for by the control unit in its command signal to the wheel angle positioner.

13. The power-assisted steering system according to claim 1 being a steer-by-wire steering system.

14. The power-assisted steering system according to claim 1 wherein an additional control unit or an additional electrical circuit performs the calculation of the virtual angle of the steering control.

15. The power-assisted steering system according to claim 14, wherein the additional control unit or the electrical circuit controls the wheel angle positioner.

16. The power-assisted steering system according to claim 1 wherein the non-trackborne vehicle is a motor vehicle.

17. The power-assisted steering system according to claim 1 wherein the steering control is a steering wheel.

18. The power-assisted steering system according to claim 2 wherein the source voltages are ones that exist within the nominal speed range of the electric motor and when the nominal speed range is exceeded.

19. The power-assisted steering system according to claim 8 wherein the motor has a large number of poles.