Method for controlling the damping force of an adjustable damper in a motor vehicle

• US 20020183907A1
• Filed: 06/03/2002
• Published: 12/05/2002
• Est. Priority Date: 06/01/2001
• Status: Active Grant

• Current Assignee: Continental AG
• Original Assignee: Continental AG
• Inventors: Stiller, Alexander
• Granted Patent: US 6,847,874 B2
• Time in Patent Office: Days
• US Class Current: 701/37
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method
• CPC Class Codes: B60G 17/08 Characteristics of fluid dampers adjusting fluid dampers in general F16F9/44 - F16F9/53
• CPC Class Codes: B60G 2400/202 Piston speed; Relative velocity between vehicle body and wheel
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2500/10 Damping action or damper

Abstract

A method controls (open loop and/or closed loop) the damping force of adjustable dampers in vehicles, especially in motor vehicles, with active or semi-active damping systems. The method effects economically and rapidly a reliable control (open loop or closed loop). The control (open loop and closed loop) takes place in dependence upon the damper velocity (V_DK) and the damper velocity signals are determined with the aid of distance sensors and difference formation of the distance sensor signals over a predetermined time difference.

Claims

1. A method for controlling (open loop or closed loop) the damping force of an adjustable damper in a motor vehicle having an active or semi-active damping system, the method comprising the steps of:

determining damping velocity signals (V_dl, V_ds) over a fixed time difference utilizing distance sensors and a difference formation of the distance sensor signals (h_i); and

,

controlling (open loop or closed loop) said damping force in dependence upon the damping velocity (V_DK).

2. The method of claim 1, wherein the damping velocity (V_dl, V_ds) is determined individually for each component to be damped.

3. The method of claim 2, wherein said distance sensors measure the distance between a wheel and the bodywork of the motor vehicle.

4. The method of claim 1, wherein a first one of said damping velocity signals (V_ds) is determined via the difference formation of said distance sensor signal (h_i) over a first time interval and a second one of said velocity signals (V_dl) via the difference formation of said distance signal (h_i) over a second time interval;

and, said first time interval being less than said second time interval; and

, a selection is made based on fixed parameters as to which one of said damping velocity signals (V_dl, V_ds) is to form the basis of the control of said damping force (F_D).

5. The method of claim 4, wherein said first damping velocity signal (V_ds) is formed over a time interval of 0.5 msec to 5 msec and said second damping velocity signal (V_dl) is formed over a time interval of 5 msec to 50 msec.

6. The method of claim 4, wherein a fixed threshold value of the magnitude of said first damping velocity signal (V_ds) is used as one of said parameters;

said first damping velocity signal (V_ds) forms the basis of the control of said damping force (F_D) when said fixed threshold value is exceeded and said second damping velocity signal (V_dl) forms the basis of the control of said damping force (F_D) when said fixed threshold value is not exceeded.

7. The method of claim 4, wherein said distance sensor signal (h_i) is filtered with a first lowpass filter having a small time constant (T1) to determine a first output signal (h_s) and said distance sensor signal (h_i) is filtered with a second lowpass filter having a greater time constant (T2) to determine a second output signal (h_l);

and, said output signals (h_s, h_l) are used to compute said damping velocity signals (V_ds, V_dl).

8. The method of claim 1, wherein said distance sensor signal (h_i) is filtered with a first lowpass filter having a small time constant (T1) to determine a first output signal (h_s) and is filtered with a second lowpass filter having a greater time constant (T2) to determine a second output signal (h_l);

the magnitude of a difference signal (d_h) between said first and second output signals (h_s, h_l) is used as a parameter; and

, a selection is made based on a fixed threshold value of said difference signal (d_h) as to which of said damping velocity signals (V_ds, V_dl) forms the basis of said control of said damping force.

9. The method of claim 8, wherein said first damping velocity signal (V_ds) forms the basis of the control of said damping force (F_D) when a threshold value for the magnitude of said difference signal (d_h) is exceeded;

and, said second damping velocity signal (V_dl) is used to control said damping force (F_D) when said threshold value is not exceeded.

10. The method of claim 9, wherein said smaller time constant (T1) is 0.25 msec to 2.5 msec and said greater time constant (T2) is 2.5 msec to 25 msec.

11. The method of claim 9, wherein said first damping velocity signal (V_ds) forms the basis of the control of said damping force (F_D) when the threshold for the magnitude of said difference signal (d_h) and the threshold value of the magnitude of said first damping velocity signal (V_ds) are exceeded;

and, said second damping velocity signal (V_dl) forms the basis of said control of said damping force (F_D) when said threshold for the magnitude of said difference signal (d_h) and the threshold value of the magnitude of said first damping velocity signal (V_ds) are not exceeded.

12. The method of claim 4, wherein said damping force (F_D) is controlled in accordance with one of the following:

skyhook method, groundhook method or a combination of said skyhook and groundhook methods.

13. The method of claim 12, wherein said damping velocity (V_DK) is used to compute an inverse damping characteristic field and the bodywork velocity (V_A) is determined from an integration of a signal of an acceleration sensor mounted on the bodywork of said vehicle.

14. The method of claim 14, wherein said damping velocity (V_DK) is used for the determination of said inverse damping field and the bodywork velocity (V_A) is determined from a damping velocity signal (V_dl) having a filtered out wheel velocity component.

15. The method of claim 14, wherein said second one of said damping velocity signals (V_dl) is used as said damping velocity (V_DK).

16. The method of claim 1, wherein a highpass filter is used to filter out oscillations of low frequency below 2 Hz from said distance signal (h_i).

17. The method of claim 16, wherein said damping velocity signal (V_dl) is applied for the computation of the inverse damper characteristic field when said output signal of said highpass filter exceeds a limit value.