METHOD FOR CONTROLLING A HYDRAULIC ACTUATOR

Abstract

A method for adjusting and adapting an operating point of a hydraulic actuator arrangement, in which a volume flow source is connected to a hydraulic cylinder via a pressure line that is filled with a hydraulic fluid. The method includes regulating a volume of the hydraulic fluid by the volume flow source, wherein an operating point of a position of the actuator arrangement corresponds, with respect to a predefined parameter, to a device which is to be actuated by the actuator arrangement. A modified volume of the hydraulic fluid which is necessary to adjust the operating point is derived from a rotational position of a volume flow source motor and/or of the volume flow source.

Claims

1. A method for adjusting and adapting an operating point of a hydraulic actuator arrangement, in which a volume flow source is connected to a hydraulic cylinder via a pressure line which is filled with a hydraulic fluid, the method comprising: regulating a volume of the hydraulic fluid by the volume flow source, wherein an operating point of a position of the actuator arrangement corresponds, with respect to a predefined parameter, to a device which is to be actuated by the actuator arrangement, and wherein a modified volume of the hydraulic fluid which is necessary to adjust the operating point is derived from a rotational position of a volume flow source motor and/or of the volume flow source.

2. The method as claimed in claim 1, wherein to determine the rotational position, a current rotational angle of the volume flow source motor and/or of the volume flow source is measured, which is regulated to a reference rotational angle of a preceding rotational angle control cycle of a rotational angle regulation which is contained in a pressure/angle regulator.

3. The method as claimed in claim 2, wherein the volume of the hydraulic fluid is determined by multiplying the measured current rotational angle by the volume of the volume flow source per unit rotational angle.

4. The method as claimed in claim 2, wherein the modified volume of the hydraulic fluid which is necessary to adjust the operating point is set via the rotational angle regulation below a predefined operating point and via a pressure regulation executed by the pressure/angle regulator above the predefined operating point.

5. The method as claimed in claim 4, wherein the rotational angle regulation and the pressure regulation are superimposed in an area of the predefined operating point.

6. The method as claimed in claim 4, wherein a point of contact of the device is used as the predefined operating point.

7. The method as claimed in claim 3, wherein a calculated leakage is taken into account when determining the volume of the hydraulic fluid.

8. (canceled).

9. The method as claimed in claim 1, wherein the modified volume of the hydraulic fluid is used as a feedforward control value in a control loop which regulates a position and/or a pressure of the device by the hydraulic actuator arrangement.

10. A hydraulic actuator arrangement, for a motor vehicle drive train, comprising a volume flow source driven by a motor, which is connected to a hydraulic cylinder via a pressure line, wherein an angle sensor for measuring a rotational angle of the motor or of the volume flow source is arranged on the motor and/or the volume flow source in order to provide an input variable for an operating point adaptation of the actuator arrangement, wherein the angle sensor is connected to an operating point adaptation unit.

11. The method as claimed in claim 1, wherein the device is a clutch.

12. The hydraulic actuator arrangement of claim 10, further comprising a clutch actuated by the hydraulic cylinder via an engagement bearing.

13. The hydraulic actuator arrangement of claim 10, further comprising a pressure sensor positioned in the hydraulic cylinder and configured for measuring a pressure of a hydraulic fluid in the pressure line.

14. The hydraulic actuator arrangement of claim 13, wherein the pressure is used as input for the operating point adaptation of the actuator arrangement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The disclosure permits numerous embodiments. One of these is to be explained in more detail by using the figures illustrated in the drawing, in which:

[0020] FIG. 1 shows an exemplary embodiment of a hydraulic actuator arrangement according to the disclosure,

[0021] FIG. 2 shows a profile of operating parameters of the hydraulic actuator arrangement when engaging a directly actuated clutch by means of the method according to the disclosure,

[0022] FIG. 3 shows an exemplary embodiment of the method according to the disclosure.

DETAILED DESCRIPTION

[0023] FIG. 1 shows an exemplary embodiment of a hydraulic clutch actuator arrangement 1 according to the disclosure, as is used, for example, in a drive train of a motor vehicle, wherein the hydraulic clutch actuator arrangement 1 is used to actuate a clutch 2. A volume flow source, formed as a pump 3 by way of example, is connected via a high-pressure hydraulic line 4 to a hydraulic cylinder 5, which acts on the clutch 2 via an engagement bearing 6. Via the pump 3, hydraulic fluid is taken in by the pump 3 from a hydraulic reservoir 7 via a low-pressure hydraulic line 8 and supplied to the hydraulic cylinder 5 via the high-pressure hydraulic line 4. By means of the hydraulic fluid, a piston of the hydraulic cylinder 5 is displaced, by means of which the engagement bearing 6 is moved and the clutch 2 is likewise displaced.

[0024] The pump 3 is driven by an electric motor 9, on which there is positioned an angle sensor 10, which determines the rotational position of the electric motor 9 in the form of a rotational angle . Positioned in the hydraulic cylinder 5 is a pressure sensor 11 for measuring the pressure p of the hydraulic fluid established in the high-pressure hydraulic line 4. The angle sensor 10 can preferably be formed here as a multi-turn sensor, which even detects the rotational angle over 360.

[0025] Given sufficiently fast rotation of the pump 3, leakage can be disregarded or represented reproducibly, so that a clutch characteristic curve which represents a clutch torque M over the rotational angle can be created. Such a clutch characteristic curve is illustrated in FIG. 2a. Likewise, a clutch characteristic curve over a volume V instead of the rotational angle can be determined, wherein the volume V can be determined without any integration step by multiplying the rotational angle by the pump volume per unit angle.

[0026] FIG. 2b shows an actuator characteristic curve, in which the pressure p of the hydraulic fluid acting in the hydrostatic actuator arrangement 1 is illustrated over the rotational angle of the electric motor 9 or of the pump. The delivered volume V over the time t is shown in FIG. 2c. The ideal delivered volume V, without taking a leakage rate into account, results in a linear relationship, wherein, in the event that a leakage rate occurs, the volume curve V.sub.leak decreases over time, the decrease already beginning before the point of contact. The point of contact TP that is important for the characteristic curves is identified in all the graphs of FIG. 2, wherein the point of contact TP is understood to mean the position of the clutch actuator arrangement 1 at which the clutch 2 begins to transmit a torque.

[0027] Since the pump 3 has a certain leakage, the rotational angle cannot be used or cannot be used exclusively over a relatively long time period t, in particular at higher pressures p or when maintaining the pressure p. Therefore, upon reaching an operating point which has been reached via the rotational angle , for example in the form of the point of contact TP, the drive strategy of the clutch actuator arrangement 1 is changed, as emerges from FIG. 2d. Here, a change is made from the rotational angle regulation R to a pressure regulation P. The control model is plotted on the Y axis of FIG. 2d. The pressure regulation P is implemented, for example, in a PID or state controller. The changeover from the rotational angle regulation R to the pressure regulation P is preferably carried out in the vicinity of or directly at the point of contact TP. This preferred region is identified by a dashed line.

[0028] An exemplary embodiment of the method according to the disclosure, which is formed as a control loop, is illustrated in FIG. 3. Illustrated is an implementation with a combined pressure/displacement regulation 12, in which the control type can be changed over between pressure p and rotational angle of the pump. Here, the pressure regulation is used in working ranges with high pressure gradients. The pump angle regulation is carried out in working ranges with low pressure gradients. This is carried out as a function of the pressure p which is exerted by the hydraulic fluid in the clutch arrangement 1. The changeover can be made during an actuation of engaged clutches above a pressure limit. The selection of the respective control method is made via a controller. The controller predefines a reference pressure p.sub.ref and/or a reference volume V.sub.ref.

[0029] The pressure regulation P is traditionally carried out by taking into account the control difference between the reference pressure value p.sub.ref and the actual pressure value p.sub.act. Depending on the selection output by the control system in block 200, the appropriate output signal from the pressure regulation or the rotational angle regulation is passed on to the pump 3. The reference volume V.sub.ref is converted via the pump characteristic value: volume per unit angle, into a reference angle .sub.ref. The difference from this actual rotational angle .sub.act measured by the angle sensor 10 and the newly calculated reference angle .sub.ref forms the input to the rotational angle regulation.

[0030] With the aid of the rotational angle .sub.act determined on the pump 3 and the actual pressure p.sub.act of the pressure p, which is determined by means of the pressure sensor 11 in the hydraulic cylinder 5, a volume V.sub.BPnew for setting a new operating point is adapted (block 210). For this purpose, the actual rotational angle .sub.act is previously converted into an actual volume V.sub.act (block 220). This new volume V.sub.BPnew of the hydraulic fluid is applied to the control system in block 200, which determines the reference value V.sub.ref of the volume V from this new volume V.sub.BPnew, which corresponds to the new operating point. Via the linear relationship between volume V and rotational angle , a reference rotational angle .sub.ref is also calculated from the reference volume V.sub.ref (block 230). From this reference rotational angle .sub.ref and the actual rotational angle .sub.act, the difference is determined and is supplied to the rotational angle regulation, which regulates the actual rotational angle .sub.act to the reference value .sub.ref.

[0031] The operating point to be adapted is defined via a pressure p.sub.BP (block 240). Once this pressure p.sub.BP is reached, the actual volume V.sub.act, which has been derived from the actual rotational angle .sub.act, is defined as a new volume V.sub.BPnew of the operating point at this time and is output to the control system (block 200).

[0032] The rotational angle regulation can optionally take into account a calculated leakage V.sub.leak, in order to improve the results of the rotational angle regulation. For the purpose of adaptation of the leakage V.sub.leak, the actual rotational angle .sub.act and the actual pressure p.sub.act are likewise used. Here, the actual pressure p.sub.act is used for the adaptation of the leakage (block 250) only when the actual pressure p.sub.act is greater than/equal to a predefined threshold value p.sub.min (block 260). The leakage rate Q.sub.leak(t) calculated from the actual rotational angle .sub.act and the actual pressure p.sub.act in block 270 is integrated in block 280. The result of this integration over time represents the leakage volume V.sub.leak, which is taken into account both in the determination of the actual volume value V.sub.act (block 290) and in the determination of the reference volume value V.sub.ref (block 300). The path of the leakage feedforward control is illustrated dashed in FIG. 3.

[0033] A comparison of the operating point that is moved to with the stored reference value V.sub.ref or p.sub.ref can be made via the pressure or, if the operating point moved to lies above the point of contact, via the clutch torque. In addition, despite changing over the regulation, the rotational angle can continue to be followed in the software and the associated parameters can be compared.

LIST OF REFERENCE NUMBERS

[0034] 1 Hydraulic clutch actuator [0035] 2 Clutch [0036] 3 Pump [0037] 4 High-pressure hydraulic line [0038] 5 Hydraulic cylinder [0039] 6 Engagement bearing [0040] 7 Hydraulic reservoir [0041] 8 Low-pressure hydraulic line [0042] 9 Electric motor [0043] 10 Angle sensor [0044] 11 Pressure sensor [0045] 12 P/ regulation [0046] .sub.act Actual rotational angle [0047] .sub.ref Reference rotational angle [0048] V.sub.ref Reference volume [0049] V.sub.act Actual volume [0050] V.sub.act new New actual volume [0051] p.sub.act Actual pressure [0052] p.sub.ref Reference pressure