Active chassis control for a motor vehicle

Abstract

An active chassis control for a motor vehicle with an adaptive control circuit for reducing body vibrations (A.sub.actual) of the motor vehicle, in which a control unit is integrated, which, depending on a current body vibration (A.sub.actual) or a parameter correlating therewith (a), controls a chassis actuator. The control unit is followed by an adaptive unit which adapts an actuating signal (S) generated by the control unit with a driving speed-dependent scaling factor (f(v)), in particular by generating an adapted actuating signal (S′) with which the chassis actuator can be controlled. Depending on the situation, a factor allowance (Δf) can be added to the driving speed-dependent scaling factor (f(v)) in the event of a significantly greater body vibration (A.sub.o) in order to effectively dampen the significantly greater body vibration (A.sub.o).

Claims

1. An active chassis control for a motor vehicle with an adaptive control circuit for reducing body vibrations of the motor vehicle, comprising: a control unit which controls a chassis actuator depending on a current body vibration or a parameter correlated therewith, wherein the control unit is followed by an adaptive unit, which adapts an actuating signal generated by the control unit with a driving speed-dependent scaling factor by generating an adapted control signal with which the chassis actuator is controlled, wherein the driving speed-dependent scaling factor is determined in a signal generation unit as a function of a current driving speed such that, (1) as the driving speed-dependent scaling factor increases, a body vibration damping effect of the chassis actuator increases with a simultaneous reduction in ride comfort and (2) as the driving speed-dependent scaling factor decreases, the body vibration damping effect of the chassis actuator is reduced with a simultaneous increase in ride comfort, and wherein an evaluation unit is assigned to the signal generation unit and the evaluation unit determines, given a significantly greater body vibration, a factor allowance that is added to the driving speed-dependent scaling factor, specifically by generating a scaling factor with which, in the adaptive unit, the adapted actuating signal is generated in order to effectively dampen the significantly greater body vibration.

2. The active chassis control of claim 1, wherein the evaluation unit does not determine the factor allowance if there is no significantly greater body vibration, so that the scaling factor in the adaptive unit corresponds to the driving speed-dependent scaling factor.

3. The active chassis control of claim 1, wherein a size of the current body vibration is represented by correlating parameters comprising at least one of a body acceleration and a body speed, and wherein a body sensor is assigned to the evaluation unit which detects at least one of the body acceleration and the body speed.

4. The active chassis control of claim 1, wherein the evaluation unit has a comparator module in which a size of the current body vibration or the parameter correlating therewith is compared with a lower limit value, and wherein the comparator module determines an absence of the significantly greater body vibration if the current body vibration is smaller than the lower limit value, so that the evaluation unit does not determine the factor allowance.

5. The active chassis control of claim 4, wherein the comparator module determines the presence of the significantly greater body vibration if the current body vibration is greater than the lower limit value so that the evaluation unit determines the factor allowance.

6. The active chassis control of claim 5, wherein, with the current body vibration between the lower limit value and an upper limit value, the evaluation unit continuously adapts the factor allowance as a function of a magnitude of the current body vibration, and/or wherein, when the upper limit value is reached, the factor allowance assumes a driving speed-dependent maximum value.

7. The active chassis control of claim 6, wherein, when the current body vibration is greater than the upper limit value, the factor allowance remains unchanged at the driving speed-dependent maximum value, and wherein the driving speed-dependent maximum value comprises a maximum value characteristic curve, in which the maximum values are plotted as a function of the driving speed.

8. The active chassis control of claim 1, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

9. The active chassis control of claim 8, wherein the predetermined period of time corresponds at least to a period of the significantly greater body vibration.

10. The active chassis control of claim 7, wherein all values of the driving speed-dependent scaling factor form a minimum value characteristic curve, and wherein, between the minimum value characteristic curve and the maximum value characteristic curve, a value range is spanned in which the scaling factor is located.

11. The active chassis control of claim 2, wherein a size of the current body vibration is represented b correlating parameters comprising at least one of a body acceleration and a body speed, and wherein a body sensor is assigned to the evaluation unit which detects at least one of the body acceleration and the body speed.

12. The active chassis control of claim 2, wherein the evaluation unit has a comparator module in which a size of the current body vibration or the parameter correlating therewith is compared with a lower limit value, and wherein the comparator module determines an absence of the significantly greater body vibration if the current body vibration is smaller than the lower limit value, so that the evaluation unit does not determine the factor allowance.

13. The active chassis control of claim 3, wherein the evaluation unit has a comparator module in which a size of the current body vibration or the parameter correlating therewith is compared with a lower limit value, and wherein the comparator module determines an absence of the significantly greater body vibration if the current body vibration is smaller than the lower limit value, so that the evaluation unit does not determine the factor allowance.

14. The active chassis control of claim 2, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

15. The active chassis control of claim 3, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent sealing factor over a predetermined period of time using the timer.

16. The active chassis control of claim 4, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

17. The active chassis control of claim 5, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

18. The active chassis control of claim 6, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

19. The active chassis control of claim 7, wherein a timer is assigned to the signal generation unit, and wherein, given the significantly greater body vibration, the factor allowance is added to the driving speed-dependent scaling factor over a predetermined period of time using the timer.

20. The active chassis control of claim 18, wherein all values of the driving speed-dependent scaling factor form a minimum value characteristic curve, and wherein, between the minimum value characteristic curve and the maximum value characteristic curve, a value range is spanned in which the scaling factor is located.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) An exemplary embodiment of the invention is described below by means of the appended figures. In the figures:

(2) FIG. 1 shows a replacement model of a chassis of a motor vehicle with associated chassis control;

(3) FIG. 2 shows diagrams of the time profiles of different parameters during chassis control;

(4) FIG. 3 shows a diagram that illustrates the damping of a significantly greater body vibration; and

(5) FIG. 4 shows a diagram with the maximum value characteristic and minimum value characteristic curves.

DETAILED DESCRIPTION

(6) In the replacement model of FIG. 1. a vehicle body 1 is supported via a suspension/damping system 3 on a chassis, whose vehicle wheel 5 rolls on a roadway 7. The suspension/damping system 3 consists of a suspension spring 9 and an adjustable shock absorber 11, which are supported between the vehicle body 1 and the vehicle wheel 5 in FIG. 1. The controllable shock absorber 11 is integrated into an adaptive control loop, with which a body vibration A.sub.actual of the vehicle body 1 is reduced during driving.

(7) For this purpose, the control circuit has a body sensor 13, which detects a body acceleration a which correlates with the current vibration A.sub.actual. The body sensor 13 is connected to the signal input of a control unit 15 in terms of signal transmission. A control signal required for vibration compensation of the body vibration A.sub.actual is generated in the control unit 15. An adaptive unit 17 is connected downstream of the control unit 15 in the signal flow direction. In the adaptive unit 17, the control signal S is multiplied by a scaling factor f, specifically by generating an adapted control signal S′, with which the controllable shock absorber 11 can be controlled in order to reduce the current body vibration A.sub.actual.

(8) The scaling factor f is determined in a signal generation unit 19. In FIG. 1, this unit has a database 21, in which a characteristic curve K.sub.min is stored, from which a driving speed-dependent scaling factor f(v) can be determined as a function of the current driving speed v. The current driving speed v is detected by a speed sensor 23 which is connected to the database 21 in terms of signals. In addition, the signal generation unit 19 has an evaluation unit 25. This consists of a comparator module 27, a determination module 29 and a timer 31. With the aid of the evaluation unit 25, a factor allowance Δf is determined during driving operation depending on the situation (for example when driving over a bump in the road). The factor allowance Δf is added to the scaling factor f(v), which is dependent on the driving speed, in a summing module 33, resulting in the scaling factor f, which is read into the adaptive unit 17.

(9) In FIG. 1, a parameter correlating with the size of the detected body vibration A.sub.actual is present at the signal input of the comparator module 27, namely the body speed v.sub.A, which follows the body vibration A.sub.actual and therefore oscillates approximately at the natural frequency of the body, which is, for example, at 1.3 Hz. The body speed v.sub.A is generated in a converter module 35 on the basis of the body acceleration a detected by the body sensor 13.

(10) The body speed v.sub.A is compared in the comparator module 27 with a lower limit value v.sub.u and an upper limit value v.sub.o. If the body speed v.sub.A is less than the lower limit value v.sub.u, the comparator module 27 determines that there is no significantly greater body vibration A.sub.0 (FIG. 2). In this case, no factor allowance Δf is determined in the determination module 29. This means that the scaling factor f read into the adaptive unit 13 is identical to the driving speed-dependent scaling factor f(v). If the current body vibration is smaller than the lower limit value v.sub.u, the comparator module 27 determines that a significantly greater body vibration A.sub.0 is present. In this case, a factor allowance Δf is determined in the determination module 29, which is added to the driving speed-dependent scaling factor f(v).

(11) As long as the body speed v.sub.A is between the lower limit value v.sub.u and the upper limit value v.sub.o, the factor allowance Δf is continuously adjusted in the determination module 29 as a function of the magnitude of the body speed v. When the upper limit value v.sub.o is reached, the factor allowance can assume a driving speed-dependent maximum value. If the body speed v.sub.A is greater than the upper limit value v.sub.o, the factor allowance Δf remains unchanged at the driving speed-dependent maximum value.

(12) The driving speed-dependent maximum value is part of a maximum value characteristic curve K.sub.max, which is plotted in the diagram in FIG. 4. Accordingly, the maximum values can be determined as a function of the driving speed v from the maximum value characteristic curve K.sub.max. In the same way, all values of the driving speed-dependent scaling factor f(v) form a minimum value characteristic curve K.sub.min. Both characteristic curves are drawn in the diagram in FIG. 4. Accordingly, a value range is spanned between the minimum value characteristic curve K.sub.min and the maximum value characteristic curve K.sub.max, in which the values of the scaling factor f that can be determined in the signal generation unit 19 are located.

(13) As an example, the chassis control at a driving speed in the low speed range of about 40 km/h (FIG. 2, first diagram from above) is explained below with reference to FIG. 2. In this case, the body sensor 13 detects a time profile of body acceleration a, which is shown in the second diagram from the top in FIG. 2. From this, the time profile of the body speed v.sub.A is calculated in the converter module 35 (see the third diagram from the top in FIG. 2). The absolute value over time is shown in the fourth diagram from the top. The absolute value over time of the body speed v.sub.A is compared in the comparator module 27 with the two limit values v.sub.u and v.sub.o.

(14) As can be seen from the time course of the absolute body speed v.sub.A (fourth diagram from the top in FIG. 4), driving takes place up to a time to on a level road surface without a bump in the road, so that there is no excessively large body vibration A.sub.actual. The comparator module 27 therefore determines that an excessively large body vibration A.sub.0 is not present. Correspondingly, the evaluation unit 25 does not generate any factor allowance Δf up to the point in time t.sub.0. This means that the scaling factor f read into the adaptive unit 17 is identical to the driving speed-dependent scaling factor f(v). At a driving speed of 40 km/h this factor has a very low value of about 0.3 (see also FIG. 4). Such a low scaling factor f reduces the damping effect of the chassis actuator 11. However, the damping effect is reduced in favor of increased ride comfort, which is of great importance for occupant comfort in the low speed range, in contrast to a damping of body vibrations, which are unproblematic for the vehicle occupants in the lower speed range.

(15) At time t.sub.0, for example, a road bump is driven over with an otherwise even road surface. This leads to a significantly greater body vibration A.sub.0, which is detected by comparator module 27. If the body vibration A.sub.0 is present, calculation module 29 calculates a factor allowance Δf. In the present example, the factor allowance Δf is around 0.5 (cf. also FIG. 4). A scaling factor f of approximately 0.8 therefore results in summing module 33, which factor is read into the adaptive unit 17. With such a high scaling factor f, the adaptive unit 17 generates a correspondingly adapted actuating signal S′, with which the chassis actuator 11 can effectively dampen the body vibration A.sub.0.

(16) If there is a significantly greater body vibration A.sub.0, the factor allowance Δf is added to the driving speed-dependent scaling factor f(v) over a predetermined period of time Δt with the aid of the timer 31. As can be seen from FIG. 4, the period of time Δt specified by the timer 31 is greater than the period of the significantly greater body vibration A.sub.0, which essentially corresponds to the natural body vibration of the vehicle body 1.

LIST OF REFERENCE NUMERALS

(17) 1 vehicle body 3 suspension/vibration damping system 5 vehicle wheel 7 vehicle track 9 suspension spring 11 adjustable shock absorber 13 body sensor 15 control unit 17 adaptive unit 19 signal generation unit 21 database 23 speed sensor 25 analysis unit 27 comparator module 29 determination module 31 timer 33 summing module 35 converter module A.sub.actual current body vibration A.sub.0 significantly greater body vibration a body acceleration v body speed f(v) driving speed-dependent scaling factor Δf factor allowance f scale factor v.sub.u lower limit value v.sub.o upper limit value K.sub.min minimum value characteristic curve K.sub.max maximum value characteristic curve S actuating signal S′ adapted actuating signal t.sub.0 point in time at which a significantly greater body vibration occurs Δt time period