Method for reducing chatter vibrations in a friction clutch in a drive train of a motor vehicle

Abstract

A method is disclosed for reducing chatter vibrations of a friction clutch controlled automatically by a clutch actuator on the basis of a target clutch torque (M(s)) assigned to a clutch torque which is to be transmitted. The friction clutch is positioned in a drivetrain between an internal combustion engine and a transmission, having a present actual clutch torque which is marked by vibrations as a result of vibrations (M(i)). From a transmission behavior of the present actual clutch torque (M(i)), an absolute amplitude and a phase of an input signal detected at the output of the friction clutch and conveyed to a regulator are ascertained, and a phase-selective disturbance torque is ascertained. From the phase-selective disturbance torque, a phase-correct correction torque (M(k)) is determined, and the target clutch torque (M(s)) is corrected by the regulator. The correction torque (M(k)) is weighted with a specifiable intensification factor.

Claims

1. A method for reducing chatter vibrations of a friction clutch controlled automatically by a clutch actuator based on a target clutch torque (M(s)) assigned to a clutch torque which is to be transmitted, said friction clutch is positioned in a drivetrain of a motor vehicle between an internal combustion engine and a transmission, having a present actual clutch torque which is marked by vibrations as a result of vibrations which occur occasionally (M(i)), the method comprising ascertaining an absolute amplitude and a phase of an input signal detected at output of the friction clutch from a transmission behavior of the present actual clutch torque (M(i)) and conveyed to a regulator, ascertaining a phase-selective disturbance torque from the absolute amplitude and the phase of the input signal determining a phase-correct correction torque (M(k)), and correcting a target clutch torque (M(s)) using the phase-correct correction torque by the regulator, and weighting the correction torque (M(k)) with a definable intensification factor.

2. The method according to claim 1, wherein the intensification factor is specified dependent on a value that is present within the method.

3. The method according to claim 1, wherein the intensification factor is specified dependent on a value that is specified outside the method.

4. The method according to claim 1, further comprising checking the input signal with regard to its regulating quality, and if quality is lacking the regulator is reset to an original state.

5. The method according to claim 1, further comprising making a determination of vibration components of the input signal, equidistant in a phase space of a reference frequency.

6. The method according to claim 5, further comprising depicting the vibration components in the form of vectors having an amplitude and a phase position in relation to the phase space, and the correction torque (M(k)) is ascertained on the basis of these.

7. The method according to claim 1, further comprising ascertaining a frequency response function of a changing transmission behavior from the target clutch torque (M(s)) and the present actual clutch torque (M(i)), and with changing transmission behavior providing a pre-control of the correction torque (M(k)) that depends thereon.

8. The method according to claim 1, further comprising correcting a phase shift dependent on detection of the input signal by a sensor.

9. The method according to claim 1, wherein the regulator is designed as an integral regulator and the correction torque (M(k)) is formed as a composite signal from an already issued phase-selective correction torque and a residual torque currently obtained from the input signal.

10. The method according to claim 1, wherein the phase-selective correction torque is formed phase-selectively opposite the residual torque by a time delay.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in further detail on the basis of the exemplary embodiment depicted in FIGS. 1 through 3. The figures show the following:

(2) FIG. 1 a block diagram of the execution of the proposed method,

(3) FIG. 2 a detail of the block diagram of FIG. 1 with a transformation of a rotational speed vector into a torque vector, and

(4) FIG. 3 a detail of the block diagram of FIG. 1 with a compensation for phase differences.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIG. 1 shows the block diagram 1 of the controlling of a friction clutch. Here, a target clutch torque M(s) is fed in from a driving strategy, and in the clutch control 2 in a position controller the distance signal, for example in the form of the control voltage V(c), is issued to the clutch actuator with the friction clutch 3. The friction clutch 3 transmits an established present actual clutch torque M(i) and is overlaid by the disturbance torque M(e), which is generated, for example, by geometric clutch errors and the like. The position controller of the friction clutch 3 is continuously readjusted by means of the disturbance torque M(e). From this results the transmission input speed n(g) at the transmission input 4. Because of the chatter behavior of the friction clutch 3, chatter vibrations develop depending on the speed of rotation and depending on the dynamic behavior of the drivetrain and the like, for example in driving-off and creeping processes and when engaging the clutch after a shifting process in the transmission; these chatter vibrations are corrected by means of the regulator 5. To this end, the chatter vibrations are identified at the transmission input by means of the regulator 5, for example a lock-in regulator, and converted to a phase-selective input torque M(k), with which the target clutch torque M(s) is corrected at the junction point 6, whereby the chatter vibrations are at least damped.

(6) In block 7, depending on the reference frequency f.sub.ref, which is fed in, for example, as a slip frequency of the friction clutch 3, as the transmission input speed n(g), as the speed of the combustion engine or the like, the regulator 5 converts the identified vibration component into the phase domain. In block 8, the Fourier components of the vibration components are determined. This is followed in block 9 by a conversion of the vibration components into torque components. The regulation of the torque components occurs in block 10 in the form of an integral control unit. Block 11 contains the phase position of the torque components on the basis of the reference frequency f.sub.ref, and output of the phase-selective correction torque M(k).

(7) FIG. 2 shows block 9 of FIG. 1 in detail. In block 9, rotational speed vector Z.sub.d is transformed into torque vector Z.sub.m. A phase shift of the rotational speed vector Z.sub.d caused, for example, by a rotational speed sensor is corrected here. In this case, the transformation vector Z.sub.t from the stored, for example saved frequency response is corrected at the junction point 13 by means of the correction vector Z.sub.k formed from the reference frequency f.sub.ref and the transmission input speed n(g). The transformation vector Z.sub.t transforms the rotational speed vector Z.sub.d into the torque vector Z.sub.m at the junction point 14.

(8) FIG. 3 shows block 10 of FIG. 1 in detail. The torque vector Z.sub.m, already corrected in block 9 with regard to a phase shift by the rotational speed sensor, is fed into block 10, which serves as an integral control unit. The torque vector Z.sub.m is reduced by the PT1 filter 15 to the filtered output Z.sub.m1. The filtered output signal Z.sub.m1 represents as it were the memory of the filter. New values are weighted and added to the previous filter value in each execution step, and then fed into the input of the PT1 filter 15. To this end, the filtered output signal Z.sub.m1 is multiplied by the correction vector Z.sub.s in a control loop at the junction point 16. The correction vector Z.sub.s is formed in junction point 19 from differential correction vector coefficients provided in block 17 and a reference frequency differentiated by time in block 18, and is fed in ahead of the PT1 filter 15. Prior to the output of the output signal Z.sub.m1 filtered by means of the vector and of correction vector Z.sub.s of the phase-selective correction torque M(k) from block 10, block 12 is provided for weighting the correction torque M(k). The correction torque M(k) can be weighted here in block 10 depending on external or internal parameters and values, in order to limit a negative influence of the regulator 5 on the target clutch torque M(s) (FIG. 1), for example in the case of an uncertain input signal in the form of the transmission input speed n(g) (FIG. 1) or the like and/or in the case of a desired intervention from outside, or to shut off the regulator 5. In order to synchronize the correction torque M(k) and the phase-corrected torque vector Z.sub.p formed from the filtered output signal Z.sub.m1 and the correction vector Z.sub.s with each other into the exact phase position, in block 20 the correction torque M(k) is delayed. The delay is half a cycle of the reference frequency f.sub.ref, with a time lag of the rotational speed sensor produced by a moving average in the Fourier component determination being compensated for here.

REFERENCE LABELS

(9) 1 block diagram 2 clutch control 3 friction clutch 4 transmission input 5 regulator 6 junction point 7 block 8 block 9 block 10 block 11 block 12 block 13 junction point 14 junction point 15 PT1 filter 16 junction point 17 block 18 block 19 junction point 20 block f.sub.ref reference frequency M(e) control torque M(i) present actual clutch torque M(k) correction torque M(s) target clutch torque n(g) transmission input speed V(c) control voltage Z.sub.d rotational speed vector Z.sub.k correction vector Z.sub.m torque vector Z.sub.m1 output signal Z.sub.p torque vector Z.sub.s correction vector Z.sub.t transformation vector