DE102005002443B4 - Method for controlling a hydraulic actuator and control unit - Google Patents

Abstract

Method for controlling a hydraulic actuator (30), characterized by the following method steps:
Detecting a pressure prevailing on the high-pressure side (13, 11, 9) of a hydraulic actuator (30) (p _{rail_0} ) at a first reference time (t = t _R0 ),
Prediction of a pressure (p _{rail_ob} ) prevailing at the beginning of a setting process (t = t _ob ) on the high-pressure side (13, 11, 9) of the hydraulic actuator (30) taking into account in a first prediction _interval (Δt _pred ), which is at the first prediction _interval Reference time (t = t _R0 ) begins and ends with the beginning of the setting process (t = t _ob ), occurring pressure changes in the hydraulic system (13, 11, 9), and
Calculating the actuation duration (t _m1 ) of a first control valve (MV1) at least as a function of a set stroke (h _setpoint ) of the actuator (30) and on the high-pressure side (13, 11, 9) at the beginning of the setting process (t = t _ob ) the hydraulic actuator (30) prevailing pressure (p _{rail_ob} ).

Description

The The invention relates to a method for controlling a hydraulic Stellers, in particular a hydraulic actuator for actuating a Gas exchange valve of an internal combustion engine, according to the preamble of claim 1 and a controller according to the sibling Claim.

Application Background such hydraulic actuator and the method according to the invention are electro-hydraulic adjustment systems, for example, the activity of valves, such as the gas exchange valves of an internal combustion engine or a compressor, or for actuating flaps, such as fast switching flaps in the intake manifold of a cylinder of an internal combustion engine, or to operate other mechanisms are used. Of particular interest are while hydraulic adjustment systems or working cylinder, a variable stroke, or a variable end position allow an adjustment.

In The rule is in such adjustment a fixed starting position present, from which an adjustment is carried out. In the example of the electro-hydraulic adjustment of a gas exchange valve is such a starting position by the concern of the gas exchange valve defined in a valve seat. For the inventive method However, this is not essential. There may be adjustment operations considered out of any rest position or starting position become.

object or object of the method according to the invention is generally the adjustment of the piston of a working cylinder from a given home position to a desired end position from Case by case may vary. It is important the end position or the adjustment or stroke sufficiently accurate adjust.

following This method is exemplified by an electro-hydraulic adjustment of gas exchange valves of an internal combustion engine or a compressor presented and formulated. With a direct transfer of the terms, for example the replacement of valve lift by travel or stroke, valve lift sensor by travel sensor or position sensor, speed by repetition frequency the operation an actuator, and gas exchange valve by piston of a working cylinder, this presentation also describes the more general applications.

For electro-hydraulic camshaft-less valve controls, as z. B. from the DE 101 27 205 A1 and the DE 101 34 644 A1 are known, stroke and timing of the gas exchange valves of an internal combustion engine can be freely programmed in principle. As a result, the operating behavior of the internal combustion engine as well as their specific fuel consumption and their emission behavior can be improved.

Indeed have electro-hydraulic camshaft-free valve controls yet an optimization potential with regard to the control of the valve lift on. The possible Improvements lie in the adjustment accuracy of the valve lift and in the time required for the representation of the stroke control technical effort. This also applies analogously for the control of adjustment or positioning operations in the other, the beginning mentioned systems, for the invention can be used.

Furthermore, from the DE 101 30 232 A1 a method for controlling and regulating an actual pressure of a transmission is known, in which control parameters are variable as a function of a control difference, wherein the actual pressure can be reduced by changing the control parameters quickly or slowly and an actuator is acted upon by appropriate control signals.

The present invention provides a development of the solutions already described. The particular challenge and central task is to provide a new and advantageous method and apparatus for calculating a stroke-determining oil pressure (p _oil ), with the required accuracy of the stroke control of a hydraulic actuator specifically can also be ensured in such cases, in which a mean oil pressure (p _rail ) can be adjusted in a high-pressure accumulator (rail) with potential high dynamics, this pressure accumulator provides the auxiliary power to operate the hydraulic actuator.

These Task is with a method for driving a hydraulic Stellers with the features of claim 1 and with control unit with the Characteristics of claim 19 solved.

In the method according to the invention, it is provided that a pressure prevailing on the high-pressure side of a hydraulic actuator determines pressure at a first reference time, for example based on a current detection value, and, based thereon, on the high-pressure side of the hydraulic actuator prevailing at the beginning of an actuating process (execution time) Pressure is predicted, this prediction occurring in the so-called prediction high pressure side Estimates pressure change. In this case, the prediction interval begins at the named first reference time, or at the last past acquisition time, and ends with the execution time of the adjustment. Furthermore, it is provided that the actuation duration (t _m1 ) of a first control valve (MV1) of the hydraulic actuator is calculated at least as a function of a setpoint stroke (h _setpoint ) of the actuator and a stroke-determining oil pressure (p _oil ) in whose determination the predicted value of the at the beginning of the adjustment on the high pressure side of the actuator prevailing pressure is received.

Advantages of invention

With the method according to the invention Is it possible, at a calculation time, for example the first reference time, if necessary, clearly before the start (execution time) of the actual Stellvorgangs is the ruling at the beginning of the adjustment process in the high-pressure accumulator Predict pressure. This prediction succeeds considering the values measurable at the first reference time, in particular the rail pressure, and in the knowledge of the (first) prediction interval present or occurring influences, for example, other actuating processes or the flow rate the high pressure pump, causing pressure changes in the high-pressure accumulator lead.

Even with very fast and strong changes in the pressure in the rail, for example, by appropriate control of a high-pressure pump brought can be and in typical applications also occur is the goodness of inventive pressure prediction very well. As a result, the accuracy of the stroke control according to the invention greatly improved without any additional Sensors would be required or particularly high demands on a control unit with regard to computing power and storage space.

at an advantageous embodiment considered the invention the estimate the pressure changes in high-pressure storage during of the prediction interval expiring settlements of other hydraulic actuators connected to the high-pressure accumulator are connected, or required for these adjustments oil quantities.

there be in a further advantageous embodiment of the method according to the invention the for an opening process or closing process required quantities of oil according to the respective change calculated by internal volumes of the volume, by simple formulas dependent on the set stroke (h) and the geometry of the actuator can be displayed are.

In order to improve the prediction according to the invention, a so-called "biasing quantity" (Q _bias ) can also be taken into account, which is the amount of oil required to bring a first working space of the hydraulic actuator to an equilibrium pressure, typically about half of that in the high-pressure accumulator prevailing pressure to bring.

In a simple, exemplary construction, a hydraulic actuator has a working cylinder and a piston movable therein with two different sized effective surfaces, an upper surface (A _ob ) and a lower surface (A _unt ). The amounts of oil needed to open or close the actuator can be calculated in this example using the following simple formulas: Q Drain, open = Q leader + (A if - A unt ) · H, (1) Q Outflow, closing = A unt ·H. (2)

When further influence, which leads to a decrease in the pressure in the high-pressure accumulator can a leakage, for example in the form of a mean leakage volume flow, considered with the total amount of leakage in the prediction interval as Product of length this time interval and the currently determined value of the leakage volume flow results.

By These programmable easy-to-control calculation rules Is it possible, the quantities of oil, which mainly by Stellvorgänge in the first prediction interval removed from the high-pressure accumulator be calculated, and in a further step the resulting To quantify pressure drops. This is a first essential step for a sufficiently accurate prediction the oil pressure done at the beginning of the setting process.

In Another advantageous embodiment of the invention will be in the Calculation of during the prediction interval occurring pressure changes the flow rate or the delivery volume flow a high pressure pump and any changes in this flow rate considered, for example, through the change a control, that is, be brought about by an adjustment of this pump.

In this way, in the method according to the invention, a complete mass balance of the high-pressure accumulator is set up during the entire first prediction interval. Starting from the time of the first reference, For example, measured pressure in the high pressure accumulator is thus a sufficiently accurate prediction of the oil pressure in the high-pressure accumulator, or the stroke-determining oil pressure (p _oil ), possible for the execution time of a considered setting process.

In further advantageous embodiment of the method according to the invention is provided during the of the first prediction interval occurring changes the delivery volume flow the high pressure pump in dependence a control (Tastv) of this pump can be determined. In particular, will assuming a control by a pressure regulator, in dependence a desired pressure and an actual pressure in the high-pressure accumulator and of a current volume flow requirement such a control (tastv) certainly.

Thereby is it possible according to the invention while of the first prediction interval occurring changes the delivery volume flow the high pressure pump, for example, by a deviation of the at the first reference time determined actual pressure from one to first reference time previously known target pressure caused into prediction the oil pressure flow in allow. This will increase the accuracy of the prediction of the oil pressure further improved.

In Advantageous embodiment of the method according to the invention is the controller the high-pressure pump designed as a PI controller. This controller type is for the said control of the flow rate the high-pressure pump suitable and easily controllable control technology.

In further advantageous embodiment of the method according to the invention it is envisaged that the conversion of the quantities of oil required and used for and / or the flow rate of High pressure pump during the first prediction interval, into the corresponding pressure changes the high-pressure accumulator in dependence of a substance size (elasticity) of the oil and a effective volume takes place, in particular the volume of the High-pressure accumulator and the associated lines received. The elasticity is dependent on determined by pressure and temperature of the working medium. This can a conversion of the required oil quantities based on the operating point or the promotion amount in pressure changes be made, which further improves the accuracy of the method according to the invention elevated.

Finally, a further improvement in the prediction of the stroke-determining oil pressure (p _oil ) of a setting process can be achieved by determining or predicating further hydraulic effects, such as pressure oscillations or spatially-temporally localized pressure changes (pulses) in the high-pressure accumulator. In particularly advantageous embodiments of the method according to the invention, a correction variable is provided for the consideration of such an effect, for example a pressure oscillation, which is read out as a function of the operating point from a characteristic map with empirically determined data.

The inventive method can be further improved if at the first reference time still further operating variables of hydraulic actuator, such as the temperature in the high-pressure accumulator and / or a measure of the adjustment the high pressure pump, are detected, and if these other operating variables for prediction the pressure and / or to calculate the driving time of the first control valve to be used. It can the other company sizes an average of several measured values or a single value measurement be won.

Around the accuracy of the method according to the invention even with changes to ensure the properties of components or hydraulic oil or to improve, the inventive prediction algorithm may be running be adapted on the basis of detected errors of the prediction, this means, Deviations of a predicted value from a corresponding measured value.

In further supplement the method according to the invention can be provided that at a second reference time in the high-pressure accumulator prevailing pressure taking into account the in a second prediction interval, which starts at the first reference time and at the second reference time ends, occurring pressure changes in this memory it is calculated that the pressure in the high-pressure accumulator is measured at the second reference time, and by the comparison of the pressure measured at the second reference time with that for this Timing predicted pressure a prediction error is determined.

By the determination of the prediction error is the goodness of the prediction procedure quantizifiable and it may be in a further advantageous addition, the inventive method dependent on this prediction error be adapted. For this it is sometimes only necessary, individual Parameters of sub-calculations, such as a time constant a dynamic model of the pump, or data of an operating point-dependent calculation a leakage volume flow, adjust accordingly.

As a result, it is possible by the application of the method according to the invention, Abwei tions of the pressure predicted for the execution time of a setting operation from the actual pressure occurring at that time to a negligible order of magnitude.

This is without additional Expenditure on sensors and without one - in terms of memory or computing power - especially powerful control unit possible, so that the inventive method has a broad scope.

Further Advantages and advantageous embodiment of the invention are the following Drawings, the description and the claims can be removed. All described in the drawings, the description and the claims Features can both individually and in any combination with each other invention essential be.

drawings

It demonstrate:

1 an embodiment of a hydraulic actuator according to the invention;

2 time profiles of the pressure in the high-pressure accumulator and the strokes of two actuators during a period of time which includes a prediction interval for one of the two actuating operations;

3 a flow diagram of an embodiment of a method according to the invention;

4 to 6 Block diagrams of functional modules according to the invention;

7 chronological courses of the pressure in the high pressure accumulator as well as the control and the travel of the high pressure pump;

8th to 16 Block diagrams of further functional modules;

17 the time course of rail pressure and predicted oil pressure in an application example (single-cylinder engine) with sudden changes in target pressure and valve lifts;

18 the time course of the valve lifts and the flow rate of the high pressure pump for the application example 17 ;

19 the time course of the relative errors of the valve lifts for the application example 17 with inventive pressure prediction; and

20 the time course of the relative errors of the valve lifts for the application example 17 waiver of a pressure prediction.

description the embodiments

In 1 an example of a hydraulic control system is shown as a block diagram, on the basis of which the inventive control of a gas exchange valve 1 should be executed as an example. The gas exchange valve 1 can be designed both as an inlet valve and as an outlet valve. If the gas exchange valve 1 is closed, it lies on a valve seat 2 an internal combustion engine.

The gas exchange valve is actuated 1 by a hydraulic working cylinder 3 , which is the central mechanical-hydraulic component of an electrohydraulic actuator 30 represents. Furthermore, the in 1 exemplified actuator 30 a first control valve MV1 and a second control valve MV2, hydraulic lines 11 such as 19a and 19b , a valve brake 29 and an optional check valve RV1.

The components mentioned are in typical embodiments of a Stellers 30 integrated in a structural unit.

The working cylinder 3 is as a differential cylinder with a piston 5 formed with one-sided piston rod. The working cylinder 3 However, can also be performed with double-sided piston rod (not shown).

The piston 5 has a larger upper effective area A _ob and a smaller lower effective area A _unt . The upper effective area A _ob limits a first working space 7 of the working cylinder 3 , The lower effective area A _unt limits a second working space 9 , Both workrooms 7 and 9 be from a feedline 11 which are made up of the sections 11a . 11b and 11c supplied with pressurized hydraulic fluid, such as hydraulic oil supplied. For this purpose, the working cylinder 3 high pressure side via the feed line 11 and a first check valve RV1 installed therein with a high pressure accumulator 13 hydraulically connected, which provides the hydraulic energy for the adjustment process. The high-pressure accumulator 13 may include a gas spring accumulator (not shown). This gas spring accumulator serves to pressure fluctuations in the high-pressure accumulator 13 to reduce.

When the first workroom 7 via the feed line 11b pressurized hydraulic fluid is applied, the gas exchange valve moves 1 in the direction of an arrow 15 and thus lifts off the valve seat 2 from, because the upper effective area A _ob grö SSER _unt is lower than the effective area A. In the section 11b the feed line 11 which the second control room 9 and the first control room 7 connects, a first control valve MV1 is arranged. In the in 1 shown switching state, it is closed and de-energized.

The hydraulic fluid in the first working space 7 can via a preferably pressureless or with low pressure level applied return line 19 which are made up of the sections 19a . 19b and 19c composed, be dissipated. In the return line 19 a second control valve MV2 is arranged, which in 1 is shown open. The second control valve MV2 is advantageously opened normally.

In the second workroom 9 can a closing spring 27 be provided, which is the gas exchange valve 1 with unpressurized working cylinder 3 in the closed position, that is in contact with the valve seat 2 , brings or holds in this position.

In a likewise advantageous alternative embodiment of the hydraulic actuator of the working cylinder 3 be designed as a single-acting cylinder. In this case, the work space remains 9 essentially unpressurized, the connecting line 11c not applicable and the closing spring 27 is designed so that it applies the force required for the operation of the hydraulic actuator for the closing operation. In an advantageous development of this embodiment, the spring is designed progressively, that is with an over the travel of the piston 5 increasing spring force.

It is also beneficial to the possibilities of hydraulic and mechanical power generation, as described above, to combine to the closing To provide force of the hydraulic actuator.

The high-pressure accumulator 13 is via a high pressure pump 17 supplied with high pressure hydraulic oil (not shown). The delivery power w _pump the high-pressure pump 17 is adjustable in the embodiment shown. This regulation can be achieved, for example, via a pulse-width-modulated control of the high-pressure pump 17 respectively. This control is in 1 indicated by the duty cycle tastv. The high pressure pump is activated 17 as well as the control valves MV1 and MV2, from a controller 31 , It is also possible feedback to the control unit via the Pumpenstellweg psw 31 to convey. Of course, the invention is not on controllable high pressure pumps 17 limited.

In the section 11a the feed line, which the high-pressure accumulator 13 with the steller 3 connects, a first check valve RV1 is provided, so that a return flow of hydraulic fluid from the second working space 9 in the high-pressure accumulator 13 is prevented.

Between the first workspace 7 and the second control valve MV2 is a hydraulic brake device 29 intended. This hydraulic braking device 29 works as follows: when the piston 5 moved upwards and consequently the volume of the first working space 7 is reduced, the hydraulic fluid flows out of the first working space 7 through the section 19a the return line 19 off, until the top of the piston 5 the section 19a the return line 19 closes. Thereafter, the hydraulic fluid from the first working space 7 only via the hydraulic braking device 29 , which consists essentially of a throttle, drain, since the connection to the hydraulic braking device 29 at the top of the workroom 7 is arranged. By compared to the flow resistance of the section 19a the return line increased flow resistance of the hydraulic braking device 29 becomes the piston 5 braked before the gas exchange valve 1 on the valve seat 2 rests.

In high pressure storage 13 are temperature sensors T _rail and pressure sensors p _rail arranged, which via signal lines to the control unit 31 are connected. The high pressure pump 17 , the first control valve MV1 and the second control valve MV2 are also via signal lines to the controller 31 connected and are controlled by this. Also, the hydraulic brake device 29 , as in 1 indicated, be designed as an active braking device and a signal line from the controller 31 be controlled if necessary. The signal lines are in 1 shown as dashed lines.

If, as in 1 shown, the first control valve MV1 closed and the second control valve MV2 is opened, the pressure causes p _udr in the second working space 9 that is the gas exchange valve 1 against the direction of the arrow 15 moved and thus closed.

The force required for this is provided by the second working space 9 with high pressure hydraulic fluid from the feed line 11 is supplied while the pressure p _odr in the first working space 7 due to the hydraulic connection to the return line 19 drops rapidly and ultimately the very low pressure p _R1 in the section 19c the return line equalizes.

To open the gas exchange valve 1 the second control valve MV2 are closed and the first control valve MV1 is opened. Thereby finds a pressure equalization between the first working space 7 and the second workspace 9 instead of.

As a result, the gas exchange valve opens 1 because of the first workroom 7 pressurized face A _ob the piston 5 is larger than that of the second workspace 9 pressurized annular surface A _{unt of} the piston 5 ,

This in 1 illustrated system for electro-hydraulic control of the gas exchange valve 1 is only one embodiment, which should serve to explain the method according to the invention. The inventive method is not on the in 1 shown limited system, and in particular regardless of the intended use of the hydraulic actuator 30 , It is obvious to a person skilled in the art that, for example, the number and location of the sensors for detecting the pressure can be varied. Similarly, unlike in 1 shown, also a single-acting hydraulic cylinder 3 and / or a piston 5 with above the stroke variable upper effective area A _ob are used. Common to all systems, however, is that at least one control valve (MV1, MV2) must be present around the hydraulic actuator 3 to press.

The following are based on an in 2 The process of the invention and the dynamic processes that are essential for the solution of the problem will be briefly explained.

In 2 two curve diagrams are shown on top of each other, on the abscissa time t is plotted. The upper diagram is a time course 34 represented by the pressure p _rail , with the settling processes of two different gas exchange valves 1 corresponds. The corresponding lifting curves 32 and 33 are shown in the diagram below. Various times, including calculation, sampling and execution times, are entered on the t-axis, which are explained below.

First of all on the choice of calculation times. It understands itself that controls the gas exchange valves of a Internal combustion engine synchronized with the rotation of the crankshaft the internal combustion engine must drain. In a four-stroke process means this in relation to a single cylinder, that in principle every two revolutions of the crankshaft corresponding similar Repeat control operations. In a multi-cylinder internal combustion engine must in principle for each cylinder the same repeated control operation be made, wherein the only difference between the control of different cylinders It is that based on the rotation of the crankshaft the Control of the gas exchange valves of different cylinders with a time delay to each other.

As a result, for example, in a four-cylinder four-stroke engine every 180 ° crank angle is a corresponding calculation of the required control variables for the control of a gas exchange valve 1 performed a respective current cylinder. That is, the respective calculation timings follow each other in synchronism with the rotation of the crankshaft at a distance of 180 °. In this case, the sequence of the control of the four cylinders of course depends on the firing order of the internal combustion engine. In internal combustion engines with other numbers of cylinders, the crank angle distance of the calculation times changes accordingly.

In 2 are corresponding, consecutive calculation times marked as the first and second reference time t _R0 and t _R1 . As already mentioned, these reference times, or their time interval, depend on the position or the rotational speed (rotational speed) of the crankshaft of the internal combustion engine.

At time t _R0 in this example, the control of a first gas exchange valve 1 calculated. The lift curve resulting from this control is in the lower diagram in 2 through the line 33 shown. This also is the time t _whether the onset of the stroke movement shown, which is regarded as the time of execution of this adjustment process.

The period of time between calculation time t _R0 and execution time t _ob represents an initial interval already mentioned, the length of which is designated Δt _pred . In this case, it is assumed in this case without restriction of generality that takes place at the time of calculation, a current measurement of the rail pressure. The last past detection time t ₀ thus coincides with t _R0 . In the case that t _{0 is} before t _R0 , the prediction _interval is extended accordingly. The current rail pressure determined at reference time t _R0 is in 2 _denoted by p _{rail_0} .

The object of the pressure _{prediction according} to the invention, carried out at the time t _R0 , consists essentially of the rail pressure p _{rail_ob} for the execution time t _{ob of} the setting process, the lifting curve 33 to determine as well as possible the stroke h of the gas exchange valve 1 , a setpoint h _set accordingly, with the required accuracy.

In the in 2 example shown is further adjustment of a second gas exchange valve 1 , with lifting curve 32 , within the prediction interval. In the case of pressure prediction, therefore, the quantities of oil are those during the opening movement of this second gas exchange valve 1 in the time interval t _ob2 to t _oe2 and during the closing operation between t _sb2 and t _se2 the high-pressure _accumulator 13 be taken into account. Corresponding short-term influences of these oil withdrawals on the pressure p _rail are in curve 34 visible, noticeable.

It should be emphasized that the situation shown in this example, in particular the not insignificant length of the prediction interval between the times t _R0 and t _ob , represent a typical situation for a motor control system. The calculation times must be chosen early enough with regard to their fixed reference to the position of the crankshaft in order to be able to carry out the necessary calculations in good time even for the earliest desired start of a setting process. This consideration must include a calculation time required for the calculations as well as the maximum possible speed of the crankshaft. However, the disadvantage of the long prediction interval is the advantage of a uniform and high utilization of one in the control unit 31 counteract the processor used to perform the calculations, so that no particularly fast and expensive processor is needed. In contrast, the latter would be the case if, in an alternative embodiment, the complete calculations required for the control processes were carried out shortly before a respective execution time, and thus on a case-by-case basis at different crank angles.

As already said, so the calculations that control the lift curve 33 a gas exchange valve 1 be required already performed at time t _R0 .

This includes in particular the calculation of a control variable (activation duration) t _m1 for the first solenoid valve MV1 of the relevant actuator 30 (please refer 1 ), wherein the stroke h is adjusted by the opening duration of the solenoid valve MV1. An important _parameter for the activation time t _m1 is the pressure p _{rail_ob} in the high-pressure _accumulator 13 t at the beginning _whether the driving operation in the gas exchange valve, 2 shown. According to the invention, this pressure is predicted on the basis of the information present at the first reference time t _R0 , in particular starting from a pressure p _{rail_0} measured at the time t _R0 . In the prediction, a possible deviation of the actual pressure P _{rail_ob} present at the later time t _ob is _estimated from the measured pressure P _{rail_0} at the time t _Ro . This deviation is from the upper diagram of 2 clearly visible.

The time profile of the pressure in the mentioned (first) prediction interval between the first reference time T _R0 and the start of the opening of the gas exchange valve at the time t _ob can be characterized by three phenomena:
First is the upper diagram of 2 to infer that the pressure P _rail represented by the line 34 increases. This rise, which is illustrated by a connecting line between the pressure P _{rail_0} and the pressure P _{rail_ob} , is superimposed on two pressure reductions, which coincide with the setting operations of the second gas exchange valve (see the lower diagram of _FIG 2 ).

Namely, while the first control valve MV1 of the actuator 30 This second gas exchange valve is open and thus this gas exchange valve opens, is from the high-pressure accumulator 13 Hydraulic fluid removed, resulting in a pressure drop. This opening process of the second gas exchange valve begins at time t _ob2 and ends with the closing of the solenoid valve (MV2) at time t _oe2 .

At time t _sb2 , the second gas exchange _valve 1 closed again. This closing process ends at time t _se2 . In the time interval between t _sb2 and t _se2 hydraulic fluid is also removed from the hydraulic actuator, resulting in a second pressure reduction in the high-pressure _accumulator 13 leads. This second pressure reduction is also in the upper diagram of FIG 2 clearly visible.

The aim of the method according to the invention is, starting from the measured value P _{rail_0} , which is detected at the first reference time t _R0 , to calculate or predict the pressure P _{rail_b} ZU prevailing at the beginning of the opening of the first gas exchange _valve at the time t _ob .

For this purpose, it is necessary to have a mass balance for the entire storage volume of the high-pressure accumulator 13 and, if necessary, further connected volumes or lines. In this quantity balance are the outflow of hydraulic fluid, which occurs by adjusting operations during the first prediction period .DELTA.t _pred , as well as those of the high-pressure pump 17 during this interval in the high-pressure accumulator 13 considered amount of fluid to be considered.

Furthermore, in advantageous embodiments of the method according to the invention even the change in the elasticity of the oil, or an effective volume elasticity of the entire memory, be taken into account with the changing pressure p _rail . In the volume elasticity, that is, the proportionality factor between change in quantity and pressure change, in particular, the effect of one with the high-pressure accumulator goes 13 connected spring accumulator (in 1 not shown), if any.

Because in the control unit 31 , which controls the control of all hydraulic actuators 30 an internal combustion engine and optionally the high-pressure pump 17 - If it is a regulated pump - carries out the information about all in the first prediction .DELTA.t _prad running actuators and possibly also via the control of the high-pressure pump 17 are present, a very accurate prediction of the pressure P _{rail_ob} at time t _ob can already be made for the first reference time t _R0 .

In this case, the oil quantity used for an opening operation during the first prediction _interval Δt can be calculated according to the formula already mentioned above: Q Drain, open = Q leader + (A if - A unt )·H. (see 1)

Q _leader is the bias set already explained above. The area A _ob is the effective area of the piston 5 on the side of the first workroom 7 and A _unt the corresponding second active surface, the second working chamber 9 of the working cylinder 3 limited. The symbol h denotes the stroke of the setting process, whereby a corresponding setpoint can be used for the calculation. In the present example h = h _{2 would} be set because the second gas exchange valve is to be opened to the desired stroke h ₂ .

Similarly, as stated above, the amount of oil needed to close a gas exchange valve can be calculated: Q Outflow, closing = A unt ·H. (see 2)

It goes without saying that the representation according to 2 is only an exemplary representation of the time course of the pressure p _rail and in internal combustion engines with a different number of cylinders possibly other _settling processes completely or partially during the first prediction _interval .DELTA.t _prad expire. According to the method of the invention, these setting processes must also be taken into account in the prediction of the oil pressure for a time t _ob , starting from the measured pressure p _{rail_0} at the time t _R0 .

The following is based on the 3 the basic sequence of the method according to the invention explained with reference to a flowchart.

The method begins in a block "Start" at a first calculation time, for example at the time t = t _R0 . In a following block 35 is the in the high-pressure accumulator 13 prevailing mean pressure p _{rail_0} at time t _R0 measured or calculated on the basis of one or more measured values. Optionally, at the time t _R0 even more operating _variables , such as the temperature T _{rail of} the hydraulic fluid in the high-pressure accumulator 13 measured.

In a block 37a the quantities of oil which are predicted during the first prediction _interval Δt by _{adjusting operations} from the high-pressure accumulator are calculated 13 be removed.

In a block 39a is the flow rate of the high pressure pump 17 calculated in the first prediction _interval Δt _pred .

In a block 41a are the quantities of oil or volume changes that occur in the blocks 37a and 39a calculated, converted into pressure changes.

Starting from the determined for the time t = t _R0 , for example, measured value p _{rail_0} the mean pressure in the high-pressure _accumulator 13 , and with the help of the block 41a calculated pressure changes can now be in one block 43 the calculation of the pressure p _{rail_ob} at time t = t _ob done.

In a block 45 subsequent calculations are carried out, including the determination of the control variable t _m1 for the considered setting process. Further calculations, for example for the purpose of adaptation, can be added here. Alternatively, they can be carried out further forward, that is to say in one of the preceding blocks.

In a block 47 the next calculation time t _R1 = t _R0 + Δt _{sync is} determined, or waiting for the occurrence of this time. Thereafter, the inventive method begins before the block 35 again. This method according to the invention is carried out anew at each reference time t _Ri , i = 0, 1, 2..., As long as the internal combustion engine is in operation.

Based on 4 the calculation is required for the digits of the stroke h = h _setpoint triggering time t _m1 of the magnetic valve MV1 f by means of the so-called inverse Hubtransferfunktion _tm1 explained. The underlying method is the subject of the above-cited, unpublished patent applications on which the provisional application is based.

In the inventive calculation of the control variable t _m1 the context t m1 = f tm1 (h; T; Oil , p Oil , ...) (3) evaluated. In this calculation, according to the invention in 4 function module h_to_tm1 shown, go as operating point specific parameters a stroke-determining oil pressure p _oil and in general an oil temperature T _oil and possibly other influencing variables, for example, a measure of the on the gas exchange valve 1 acting gas forces.

The parameter p _Oel is calculated by the function module ber_p_Oel. To an accurate result for to achieve at h = h _setpoint adjusted stroke would, in the calculation of the activation time t _m1 according to equation (3) the values of the parameters at execution time t be used _whether the observed setting operation, the time of calculation, by way of example to a Time t _R0 , but still unknown or not measurable.

The determination of the pressure p _oil is therefore based, according to the invention, on a prediction which succeeds _essentially on _{account of} the prediction of a mean rail pressure p _{rail_ob} at the time t _ob . In an exemplary embodiment of the function module ber_p_Oel, shown in 5 , this task is taken over by the submodule ber_p_präd, which calculates and outputs an estimated value p _pred for p _{rail_ob} . The prediction, as already described, is based on measured values of the pressure, represented by an input variable p _rail , as well as information on further setting processes, represented here by an input E _X.

Another module ber_p_Oel_puls_korr is responsible for the determination of an additive correction _variable p _{Oel_puls_korr} , in which the above-mentioned effects of pulsations in the high-pressure _accumulator 13 be imaged. This includes, for example, a superposition of locally-temporally localized pressure fluctuations as a result of simultaneous or overlapping setting processes.

The calculation of the variable p _{Oel_puls_korr} in the function module ber_p_Oel_puls_korr can be based, for example, on empirical values depending on the operating point, which values are stored, for example, in tabular form in the electronic control unit. Alternatively, a physical description may be based on the causative influences - that is, volume decreases in valve events as well as volume flow according to that of the high pressure pump 17 delivered volume flow - be used in one version of the module ber_p_Oel_puls_korr.

In the case of a large effective rail volume or the use of a spring accumulator, the required accuracy of the stroke control can sometimes also be achieved without consideration of this correction, ie with p _{Oel_puls_korr} = 0. In this case, the module ber_p_Oel_puls_korr can be omitted.

In the execution according to 5 a third submodule ber_p_Oel_h_komp is used to compensate for _{intra-stage pressure oscillations} by an additive correction _variable P _{Oel_h_komp} . In particular, this submodule uses the input quantity h _setpoint , that is to say the setpoint value of the stroke for the control process under consideration. For further information on the last-mentioned submodule, reference is made to the first of the patent applications cited above, on which the present invention is based.

The correction _quantities p _{Oel_h_komp} and P _{Oel_puls_korr} become as in 5 shown added to p _pred to determine the effective (stroke-determining) oil pressure p _oil for the currently considered setting process.

following becomes an essential part of the invention, namely the design of the functional module ber_p_präd described. This functional module is responsible for the stronger changes rail pressure in a short time otherwise - when using obsolete Pressure information - resulting lifting error by means of a prediction this pressure change to reduce or avoid.

The decisive aspect is the inclusion of the electronic control unit 31 available Information about the causes of such pressure changes. These are, as already described, on the one hand, the extraction of oil quantities by valve positioning operations. These operations are performed by the controller 31 triggered and are therefore basically - also in terms of their effect on the rail pressure - known.

To the changed others the average rail pressure is due to the inflow of oil from the high-pressure pump, the balance of this inflow and outflow through the adjustments for the total change the average rail pressure prevail is.

The volume flow w _{pump of} the high-pressure pump 17 and its temporal change are in the control unit 31 also known. The required and existing information includes in the case of an adjustable high-pressure pump 17 also the control of this pump. For this purpose, for example, a function module "pump control" according to 6 present, which has a control variable Tastv, corresponding to a duty cycle (see also 1 ).

By way of example, the functional module as a PI controller can be executed, the on the basis of a difference formation of a preset value p _target for the average rail pressure and the actual value detected by the rail pressure sensor _is p, and on the basis of a mitt _{Requirement of} the currently pending valve actuator events, which determines the currently required duty cycle, probv. If necessary, the last value of the duty cycle is also included in this calculation.

For example, it is assumed that the calculations of the function modules of the pump control ( 6 ), as well as the calculations of the stroke control (see 4 ) synchronously with the rotation of the crankshaft of the engine equipped with the valve control system under consideration. The mentioned reference _times t _R0 , t _R1 , ... are also used as calculation times of the pump control. In an alternative embodiment, however, the pump control can also operate on a time-based basis or be executed in a time-synchronized manner. The inventive method is equally applicable in this case.

Based on the knowledge of the control variable Tastv the high-pressure pump 17 estimate the delivery rate of the pump in the prediction interval. This calculation is as a step 39a of the method according to the invention in the flowchart of 2 listed.

To illustrate this part of the method according to the invention are in the 7 , in addition to 2 and corresponding to the signals shown there, the courses of further signals for the in 2 considered example presented. In the first case, this is an example of an assumed course of the control variable "tastv" of the pump 17 in the lower of the three superimposed diagrams of 7 is shown.

Second, a manipulated variable pwsr of the pump resulting from the control is shown in the middle diagram of the pump 7 represented as a function of time. The variable pswr is defined by way of example as the relative size of a so-called pump travel path, relative to its maximum position. At the same time, it provides a relative measure of the delivery flow rate of the pump 17 represents.

Next is in the upper diagram of the 7 the course of the _rail pressure p _rail 2 shown again, which has an increase in pressure on average and with regard to the short-term pressure fluctuations with the quantity withdrawals by the adjusting operations of the gas exchange valves 1 corresponds, whose lift curves 32 and 33 in 2 are shown.

In the 7 displayed to the reference time points t _R0, t _R1, ... present values of the sizes and tastv pswr the sample solution for the functional module occur in the following exemplary ber_p_präd as stepwise on successive calculation timings to be determined sizes.

Accordingly, the suffix "old" or "new" is used with respect to the current time - here t _R0 - to indicate the assignment to the last or the current calculation step for the respective size. In the case of pswr, this is a variable to be estimated or predicted, and in the case of palv, an output or control variable, as already described.

Changes in the control of the high-pressure pump 17 , that is, the size tastv, are in the in 7 shown scenario delayed in the Pumpenstellweg pswr effective, this behavior of the pump 17 described here by way of example in a control engineering representation as a series connection of a dead time element and a first-order low-pass element (PT ₁ element); please refer 8th ,

The module modPSW off 8th represents a model, or a calculation rule, for the estimation of the size pswr on the basis of the control variable palp. Such a dynamic model for a suitable relative measure of the pump position (here pswr), or the delivery volume flow of the high-pressure pump 17 , is particularly advantageous for the present purposes and at the same time sufficiently accurate in practical cases. Stationary in this model pswr = tastv.

The two time parameters T _tot and T _V can be considered as a function of the oil pressure p _rail and the oil temperature T _rail and / or the pump travel path pswr. Technically, these dependencies can be represented in the control unit, for example in tabular form by means of maps or curves.

In the exemplary embodiment of the ber_p_präd function, an in 9 shown subfunction ber_pswr responsible for the current calculation time t _R0 , to which also a possibly modified control variable is tastv = tastv _{new determined} by the module pump control (see 7 ), to calculate an intermediate value pswr _zw , which estimates the Pumpenstellweg, which is present after the dead time. The old values of pswr and tastv are included.

The model of the time behavior of the pump used as an example proceeds, as already stated, essentially from a first-order low-pass filter. This low pass is realized for the exemplary execution of the module ber_pswr as a transfer function "pt1_step" for a variable time step dt in a multiply executable representation, programmatically for example as a procedure (subroutine) 10 shows one such implementation of the module pt1 step, wherein for the implementation of the mathematical function f (x) = exp (-x) by way of example a characteristic curve "expminus" is used.

In the presentation of the module ber_pswr according to 9 the calculation pt1_step is called three times, whereby the input variables each assume different values. In a first part of the calculation algorithm, the calculation pt1_step is carried out for the time step of length dt = T _tot and thus the intermediate value pswr _{zw is} determined.

In an analog further sub-calculation of the module ber_pswr, starting from the intermediate value pswr _zw, the new high-pressure pump is _newly activated under the influence of the new control 17 successive change of pswr over the remaining prediction interval until time t _ob ( 7 ) and thus for a time step of length dt = Δt _pred - T _tot predicts, giving the value pswr _pred .

In a final sub-step of the calculation ber_pswr, 9 Is provided _R1 and the estimated value for the pump pswr _new position for the next calculation time t, which is required for a subsequent execution of ber_pswr at this time. Starting from the state pswr _zw , this means a time step of length Δt = Δt _sync - T _tot .

The in 9 For the sake of simplicity, the algorithm represented is restricted to the consideration of the cases in which the values Δt _{pred -t tot} and Δt _sync -T _{tot of} the time parameter dt are positive. The other cases are also easy to handle as special cases.

Furthermore, the assumption is made in simplifying terms that t _ob from t _{RO is} no further in the future than the time interval Δt _sync + T _tot , the synchronization time Δt _{sync being defined} as the difference of the crankshaft synchronous timestamps t _R1 -t _RO and thus for Speed of the motor is inversely proportional. This requirement can be met in practical cases by appropriate design of the calculations for valve actuation, especially for the control of the stroke considered here. However, the general case of further predictive prediction may also be dealt with in the same way as in the present embodiment. For this purpose, further sub-steps "pt1_step" as in 9 or "pt1_integ" as in 12 run through.

Analogously, the prediction of the rail pressure p _pred = P _{rail_0} which is also possible _here also _succeeds for a likewise possible time-synchronous execution of the function module "pump controller" mentioned above, possibly by considering a larger number of substeps "pt1_step" and "pt1_integ", as well as output values Pump controller in the prediction interval are approximately calculated in advance.

For further partial calculations of the function module ber_p_präd 5 which relate to the calculation of the volume inflow in the prediction interval and to the step 39a from the in 3 flowchart of the method according to the invention include a linkage of the pump position pswr with the funded volume flow w _{pump is} required. In 11 By way of example and without limitation of generality, a corresponding model is shown in which the volume flow w _pump depends linearly and in terms of a static transfer function on the pump travel path pswr. A possible non-linear dependence can be treated analogously by adapting the algorithms. The dependence of the coefficient, that is the maximum delivery volume flow, of the pump speed n _pump and optionally of pressure and temperature of the oil is described by way of example by a map-based representation.

In 12 the example implementation of the further function module is shown ber_zufluss, which estimates as a further sub-calculation within the function ber_p_präd the volume flows from the pump into the pressure rail, in the considered sub-intervals (see 7 ) of the prediction interval. Corresponding to the three in the module ber_pswr, 9 , Partial calculations performed in the module ber_zufluss three analog sub-steps are performed, which - in the form shown here by way of example on the basis of a multiple executable function or procedure "pt1_integ" - the inflowing oil quantities in the interval t _R0 to t _{0 '} = t _R0 + T _tot and estimate at the intervals from t _{0 '} to t _ob or t _R1 . The corresponding additive combination of the partial results supplies the output _quantities Q _{zu_präd} for the entire prediction interval and Q _{zu_tast} for the sampling interval t _RO ... t _R1 .

In this case, the necessary in this calculation transmission to w of pswr _pump according to the above - Adoption taken (see - without loss of generality 11 ) are taken into account by multiplication with the current value w_pump_max of the maximum delivery flow at the end of the respective partial calculation.

The in 13 An example of a block diagram of the function module pt1_integ results from the explicit integration of the low-pass behavior of pswr over a time step dt.

To complete the balance of the inflows and outflows of oil for the high pressure rail is another in 14 Function module shown over drain available, which by leakage and determined by adjusting operations of gas exchange valves 1 in the prediction interval, or in the crankshaft synchronous sampling interval (synchro-interval), the outflowing oil quantities Qab_präd respectively Q _{ab_tast} .

The calculation overflow corresponds to the step 37a from the in 3 shown flowchart of the method. The information required for this calculation are the times t _{ob of} the opening and t _{se of} the closing and the desired stroke h _{desired of} the said actuating operations, which are completely known for the prediction interval and the synchro-interval. The calculations in the module overflow are based on the above equations (1) and (2) for the oil extraction of a valve actuator when opening or closing. If single opening relationship way closing edges only partially covered in the prediction interval or sync interval, can be a simple division of the flanks to the adjacent intervals using an average rate v _at or _about made for opening v of the closing and so the relevant for the considered time interval proportionate removal quantity can be determined. The parameters v _on and v _can be represented for example by maps depending on oil pressure and oil temperature. The dependence of a _leakage volume flow Q _leakage from the operating point can also be described in a map-supported manner. Preferably, the calculation of Q _{leakage is implemented} in adaptable form; see below.

After the calculation of the volume inflows and outflows, which takes place at each crankshaft-synchronous calculation time, the conversion of oil volumes into pressure changes or resulting pressures is carried out in a subsequent calculation step Q_to_p which also belongs to the inventive function module ber_p_präd. In the flowchart of 3 These are steps through block 41a and block 43 shown.

15 shows by way of example an algorithm of this sub-calculation as a block diagram, wherein the decisive for the conversion and experimentally determinable for different pressures and temperatures volume elasticity of the high-pressure rail is stored here as a map E _vol in dependence of these parameters.

Starting from the rail pressure p _{rail_0} at time t _R0 and the oil quantities Q _{zu_präd} and Q _{ab_präd} calculated in advance for the prediction interval to t _ob , the pressure p _{pred is calculated} in this case as estimated value for the (average) rail pressure at time t _ob . This is step 43 of the flowchart 3 completed.

In subsequent calculations, the step 45 in the flowchart of the method according to the invention 3 first, the stroke-determining oil pressure p _oil and, based thereon, finally the control variable t _{m1 of} the observed setting process are determined. Responsible for these calculations are the modules ber_p_Oel according to 5 as well as h_to_tm1 according to 4 ,

In a second analogue embodiment of the function module Q_to_p, on the basis of the likewise pre-calculated oil quantities Q _{zu_tast} and Q _{ab_tast} (see 12 respectively 14 ), the rail pressure for the next _{synchronization} time t _{R1 is predicted} as estimated value p _{pred_tast} . This calculation can be used, for example, to evaluate the quality of the models used in the prediction in a later comparison of this estimated value with an actual value of p _rail determined from measured values for the time t _R1 . This can, for example, as in 16 shown, serve, if present. of systematic deviations to bring about a change in parameters of these models, for example an adjustment of the parameter TV and / or the operating point-dependent _leakage volume flow Q _leakage , and in this way to improve the model-based prediction of the oil pressure by means of a model adaptation executed in this invention.

In 17 is an exemplary time course of the actual value p _ist and the inventively determined value p _pred for the mean pressure in a high-pressure _accumulator 13 shown, are each connected to the two hydraulic actuator for the intake and exhaust valves of a single-cylinder engine. Here, the same setpoint h _setpoint is set for all the gas exchange valves, wherein p _{is intended} in the scenario shown, both the target value h _target and the target value of the pressure in the accumulator 13 be subjected to sudden changes.

The course of p _soll is also in 17 shown; he shows a jump from 65 bar to 130 bar. The corresponding course p _actual results, on the one hand, from the oil consumption of the actuating processes, whose short-term effects on the pressure p _{actual are recognizable} as high-frequency fluctuations of the pressure signal, and, on the other hand, from the delivery volume flow w _{pump of} a controllable high-pressure pump, which is adjusted by a regulator.

In 18 is this volume flow w _pump in an upper diagram and the course of the Sollhubs h _{Soll shown} in a lower diagram. The setpoint jumps at intervals between 4 and 10 mm. The reaction of the volumetric flow w _pump to corresponding control interventions of the pump control can be clearly seen, in particular, in the desired pressure jump and in the jump jumps. The impact conditions of the jump jumps are also the pressure signal p _Ist in 17 clearly.

In this highly dynamic scenario, a very high quality of the stroke control is achieved by virtue of the prediction of the oil pressure according to the invention. This is due to the in 19 shown curves of the relative lifting error (in%) of the intake and exhaust valves clearly visible. The errors are negligible.

In contrast, clear lifting errors result in the same scenario when the pressure prediction according to the invention is dispensed with in the context of the stroke control. The relative lifting errors resulting in this case are in 20 to see. They reach unacceptably high values of up to 10% at the set pressure jump. The achievable with the invention advantage for the accuracy of the stroke control is thus impressively demonstrated.

Claims (19)

Method for controlling a hydraulic actuator ( 30 ), characterized by the following method steps: - detecting one on the high pressure side ( 13 . 11 . 9 ) of a hydraulic actuator ( 30 ) prevailing pressure (p _{rail_0} ) at a first reference time (t = t _R0 ), - prediction of a at the beginning of a setting process (t = t _ob ) on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ) taking into account in a first prediction _interval (Δt _pred ), which begins at the first reference time (t = t _R0 ) and ends with the beginning of the setting process (t = t _ob ), occurring pressure changes in the hydraulic system ( 13 . 11 . 9 ), and - calculating the actuation duration (t _m1 ) of a first control valve (MV1) at least as a function of a desired stroke (h _setpoint ) of the actuator ( 30 ) and at the beginning of the setting process (t = t _ob ) on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ). A method according to claim 1, characterized in that in the prediction of the beginning of a setting process on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ) oil quantities are taken into account, which for the during the first prediction _interval (Δt _pred ) running operations of other hydraulic actuator ( 30 ;) are needed. A method according to claim 2, characterized in that the required amount of oil (Q _{outflow_Open} ) is calculated for an opening operation according to the following formula: Q abfluss_Öffnen = Q leader + (A if - A unt )·H, with: Q _prefix : amount of oil needed to create a first working space ( 7 ) of the hydraulic actuator ( 30 ) to an equilibrium pressure, for example about half of that in the high-pressure accumulator ( 13 ) of prevailing pressure (p _rail ). A method according to claim 2 or 3, characterized in that the required amount of oil (Q _{outflow_Close} ) is calculated for a closing operation according to the following formula: Q abfluss_Schließen = A unt ·H Method according to one of the preceding claims, characterized in that the pressure changes occurring on the high-pressure side during the prediction _interval (Δt _pred ) ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) in response to a leakage volume flow associated with a gradual pressure loss on the high pressure side. Method according to one of the preceding claims, characterized in that the pressure changes occurring on the high-pressure side during the prediction _interval (Δt _pred ) ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) as a function of a flow rate of a high-pressure pump ( 17 ) in the first prediction _interval (Δt _pred ). Method according to claim 6, characterized in that in the calculation of the pressure changes occurring on the high-pressure side during the first prediction _interval (Δt _pred ) ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) Changes in the flow rate of the high-pressure pump ( 17 ). A method according to claim 7, characterized in that during the first prediction _interval (Δt _pred ) occurring changes in the _delivery rate of the high-pressure pump ( 17 ) depending on the output of a regulator of the high-pressure pump ( 17 ) and / or as a function of an estimated or measured adjustment position (psw) of the high-pressure pump ( 17 ) and / or in dependence on a setpoint pressure (P _soll ) and an actual pressure (P _ist ) on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) as well as a mean volumetric flow _demand (w _demand ) during the first prediction _interval (Δt _pred ). Method according to Claim 8, characterized in that the regulator of the high-pressure pump ( 17 ) is designed as a PI controller. Method according to one of claims 6 to 9, characterized in that the conversion of the required quantities of oil (Q _{outflow_Open} , Q _{outflow_Close} ) and / or the delivery rate of the high-pressure pump ( 17 ) and / or a leakage quantity in pressure changes (Δp _i ) as a function of the elasticity and the volume of the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ), in particular a high-pressure accumulator ( 13 ), as well as, if necessary, depending on the pressure (p _{rail_ob} ) and the temperature (T _rail ) of the oil. Method according to one of the preceding claims, characterized in that at the beginning of a setting process (t = t _ob ) on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ) and / or an oil pressure (p _oil ) relevant for the adjusting process (t = t _ob ) calculated from this pressure, as a function of pressure pulsations and elastic oscillations on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) is determined. Method according to claim 11, characterized in that the contribution of pressure pulsations and elastic oscillations on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) is determined by calculating at least one correction _quantity (p _{Oel_puls_korr} ). A method according to claim 12, characterized in that the correction _quantity (p _{Oel_puls_korr} ) is determined on the basis of at least one characteristic map, the empirically determined values depending on the operating point (h _Soll , P _Oel , T _Oel ) are stored. Method according to one of the preceding claims, characterized in that at the first reference time (t = t _R0 ) further operating _variables (T _rail , ...) of the hydraulic actuator system ( 13 . 17 . 30 ), and that these further operating _{variables are used to predict} the pressure (p _{rail_ob} ) and / or to calculate the activation _duration (t _m1 ) of the first control valve (MV1). Method according to one of the preceding claims, characterized in that the on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _rail (t _R0 )) and / or the operating variables (T _rail , ...) of the hydraulic actuator ( 30 ) are formed by an average of a plurality of measured values. Method according to one of the preceding claims, characterized in that at a second reference time (t = t _R1 ) on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) pressure (p _{rail_1} ) taking into account the pressure changes in the hydraulic system occurring in a second prediction _interval (Δt _sync ) which starts at the first reference time (t = t _R0 ) and ends at the second reference time (t = t _R1 ) ( 13 . 11 . 9 ) is calculated that the on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) pressure is measured (p _{rail_1} ) at the second reference time (t = t _R1 ), and that by comparing the measured at the second reference time (t = t _R1 ) (p _{rail_1} ) and for the second reference time (t = t _R1 ) predicted pressure (p _{pred_tast} ) a prediction _{error is} determined. Method according to claim 16, characterized in that in that the methods according to one of claims 1 to 15 are dependent the prediction error be adapted. Method according to one of the preceding claims, characterized in that it uses a computer program for a control unit ( 31 ) of an internal combustion engine can be performed when a suitable program code is executed on a computer. Control unit ( 31 ) for an internal combustion engine ( 1 ), in particular of a motor vehicle, which works according to one of the methods according to claims 1 to 17, - with a first functional module (ber_pöl), one on the high pressure side ( 13 . 11 . 9 ) of a hydraulic actuator ( 30 ) Prevailing pressure _{(prail_0)} at a first reference point (t = t _R0) detected, - with a supply module (ber_p_präd) of the first functional module (ber_pöl) for predicting a start of a parking operation (t = t _if) on the high pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ) taking into account in a first prediction _interval (Δt _pred ), which begins at the first reference time (t = t _R0 ) and ends with the beginning of the setting process (t = t _ob ), occurring pressure changes in the hydraulic system ( 13 . 11 . 9 ) ,. And with a second functional module (h_to_tm1) for calculating the actuation duration (t _m1 ) of a first control valve (MV1) at least as a function of a setpoint stroke (h _setpoint ) of the actuator ( 30 ) and at the beginning of the setting process (t = t _ob ) on the high-pressure side ( 13 . 11 . 9 ) of the hydraulic actuator ( 30 ) prevailing pressure (p _{rail_ob} ).