DE19832198A1 - Controlling armature motion in electromagnetic actuator used to operate internal combustion engine valve - Google Patents

Abstract

During initial pull-in, the voltage (U) is reduced to zero. Just before impact of the armature (4d) on either coil, (4a, 4b), the voltage is reapplied for braking effect. Switching instants are time-optimized.

Description

The invention relates to a control method for the final phase movement an armature of an electromagnetic actuator, in particular for actuation supply of a gas exchange stroke valve of an internal combustion engine, the Armature oscillating between two solenoid coils against each other Force at least one return spring by alternating energization of the Electromagnetic coils is moved, and being with an approximation of Anchor to the initially energized coil during the so-called catch the electrical on the coil capturing the armature Tension is reduced. The technical environment is based on the DE 195 30 121 A1 referenced.

A preferred application for an electromagnetic actuator with the features of claim 1 is the electromagnetically actuated valve powered by internal combustion engines, d. H. the gas exchange globe valves of a stroke Piston internal combustion engines are desired by such actuators actuated way, d. H. oscillatingly opened and closed. At a Such electro-mechanical valve train, the globe valves are individually  or also in groups via electromechanical actuators, the so-called Aktua gates moved, the time for opening and closing each Lift valves can be chosen essentially completely freely. This allows the valve timing of the internal combustion engine optimally to the current Operating state (this is defined by speed and load) and to the respective requirements with regard to consumption, torque, emissions, Comfort and responsiveness of a driven by the internal combustion engine been adapted vehicle.

The essential components of a known actuator for actuating the lift valves of an internal combustion engine are an armature and two electromagnets for holding the armature in the position "lift valve open" or "lift valve closed" with the associated solenoid coils, and also return springs for the Movement of the armature between the positions "lift valve open" and "lift valve closed". For this purpose, reference is also made to the attached FIG. 1, which shows such an actuator with associated lifting valve in the two possible end positions of the lifting valve and actuator armature, and the course between the two states or positions of the actuator / lifting valve unit shown of the armature stroke or armature path between the two solenoid coils and also the course of the current flow in the two solenoid coils each over time is shown in accordance with a known state of the art (compared to DE 195 30 121 A1 mentioned earlier).

As can be seen in Fig. 1, the closing process of an internal combustion engine valve is shown, which is designated by the reference number 1 . As usual, this valve valve 1 is attacked by a valve closing spring 2 a, further acting on the stem of the lifting valve 1 - here with the interposition of a hydraulic valve lash compensation element 3 - the actuator designated in its entirety by 4 . This consists in addition to two electromagnetic coils 4 a, 4 b from an acting on the stem of the globe valve 1 push rod 4 c, which carries an armature 4 d, which is guided between the electromagnet coils 4 a, 4 b to be longitudinally displaceable. At the end of the push rod 4 c facing away from the stem of the lift valve 1 , a valve opening spring 2 b also engages.

This is thus is an oscillatory system for wel ches the valve closing spring 2 a and the valve opening spring 2 b a first as a second return spring form for which consequently the further precisely if the reference numerals 2 a, 2 may be used b. On the left side in Fig. 1, the first end position of this vibratory system is shown, in which cher the lift valve 1 is fully open and the armature 4 d is applied to the lower electromagnetic coil 4 b, which is also referred to as opener coil 4 b in the following after this coil 4 b holds the globe valve 1 in its open position. On the right side in Fig. 1, the second end position of the oscillatory system is shown, in which the globe valve 1 is fully closed continuously and the armature 4 d is applied to the upper electromagnetic coil 4 a, which is also referred to below as a closer coil 4 a after this coil 4 a holds the globe valve 1 in its closed position.

In the following, the closing operation of the globe valve 1 is now briefly described, ie in FIG. 1 the transition from the left-hand state to the state shown on the right; in between, the corresponding courses of the electrical currents I flowing in the coils 4 a, 4 b and the stroke course or the path coordinate z of the armature 4 d are respectively plotted over the time t.

Starting from the left-hand position "lifting valve open", the opening coil 4 b is first energized to hold the armature 4 d in this position against the ge valve closing spring 2 a (= lower first return spring 2 a), the current I in this coil 4 b is shown in dashed lines in the It diagram. If the current I of the opening coil 4 b is switched off for a desired transition to "lift valve closed", then the armature 4 d releases from this coil 4 b and the lift valve 1 is closed by the tensioned valve closing spring 2 a Accelerated to its central position (upwards), however, moves further due to its inertia and tensions the valve opening spring 2 b, so that the globe valve 1 (and the armature 4 d) are braked thereby. Then the make coil 4 a is energized at a suitable time (the current I for the coil 4 a is shown in a solid line in the It diagram), whereby this coil 4 a captures the armature 4 d - these are the so-called catching process -, and finally holds it in the position shown on the right "lifting valve closed". After the armature 4 d is securely caught by the coil 4 a, this is switched to a lower holding current level in the rest of this (see. It diagram).

The reverse transition from "lift valve closed" to "lift valve open" takes place analogously from the position shown on the right in FIG. 1 by switching off the current I in the make coil 4 a and switching the current for the break coil 4 b at different times . In general, an adequate electrical voltage is applied to the coils 4 a, 4 b while the switching off of the electrical current I is initiated by a reduction in the electrical voltage to the value "zero". The electrical energy required for the operation of each actuator 4 is either taken from the vehicle electrical system of the vehicle driven by the associated internal combustion engine or is provided via a separate energy supply adapted to the valve train of the internal combustion engine. The electrical voltage is kept constant by the energy supply, and the coil current I of the internal combustion engine lift valves 1 associated actuators 4 is controlled by a control device such that the necessary forces for opening, closing and holding the lift valve or valves 1 in the desired position.

In the prior art just explained, the coil current I during the so-called catching process, in which one of the two coils 4 a, 4 b seeks to capture the armature 4 d (this is the end phase of the armature movement mentioned at the beginning), from the mentioned control unit or from a control unit regulated by clocking to an essentially constant value which is large enough to safely capture the anchor 4 d under all conditions. Now the force of the catching electromagnetic coil 4 a or 4 b on the armature 4 d approximately proportional to the current I and inversely proportional to the distance between the coil and armature. If - as in the known prior art - a substantially constant current I is set, the magnetic force acting on the armature 4 d increases with its approach to the respective coil 4 a or 4 b capturing it inversely proportional to remaining gap, whereby the armature acceleration and the armature speed increase. This results in a high impact speed of the armature 4 d on the respective electromagnetic coil 4 a or 4 b, which on the one hand causes high wear in the actuator 4 , but on the other hand also results in a high level of noise. Another disadvantage are the switching losses of the transistors that occur in the briefly described clocked current control, which result in increased power consumption and thermal stress on the control device used and increased electromagnetic radiation in the feed lines of the actuators.

Improvements in particular with regard to noise as the actuator wear brings that from the above  DE 195 30 121 A1 known prior art. Here is a procedure for Reduction of the speed at which an anchor hits an electroma genetic actuator proposed, with an approach of the armature to the pole face of the coil capturing the armature, the one lying on it Voltage is limited to a predeterminable maximum value (i.e. essentially Chen reduced), so that the current flowing through the coil during part of the time of the voltage limitation drops. In this said Scripture also speaks of the extent of the tension limit or voltage reduction can be defined in a map can, whereby it can be assumed that the corresponding values and in particular the time at which this voltage reduction should begin to be determined experimentally.

In contrast, it is the task of the to show further improvements lying invention, d. H. it is supposed to be simple and practical tes control method for the end-phase movement of an anchor electromagnetic actuator according to the preamble of claim 1 to be shown. The term "final phase movement" stands for that section in the oscillating movement of the armature between between the two solenoids, in which the armature is attached to one of the Magnet coils are located approximately in front of and from this solenoid to be captured. In other words, this is supposed to Control procedure for the final phase movement during the so-called The speed of impact of the anchor on which it catches ing magnetic coil can be reduced.

The solution to this problem is characterized in that the Voltage first reduced to the value "zero" and thus switched off is, so that there is a braking phase to the catching phase of the catching process connects, and that just before the armature hits the coil  this again applied electrical voltage and thus switched on is, the respective switching times from an essentially time optimal regulation can be derived. Advantageous training and further education conditions are the content of the subclaims.

The invention is explained in more detail with reference to a preferred embodiment example, for which optional additions are also specified. This preferred embodiment already contains components represent the additions to the actual invention and consequently in stop of the subclaims. For better understanding some of these relevant components are already in the basic Be include writing.

It is generally proposed according to the present invention that be known current regulation or the also known (to be determined empirically de) voltage reduction during the catching process for the anchor by to replace an essentially time-optimal control, which the electri tension during the catching process (i.e. in the final phase of the start ker movement) initially reduced to the value "zero" and thereby the so-called Interruption phase interrupts, so that a so-called braking phase se, and which shortly before the anchor hits the Coil - d. H. still during the catching process within a so-called Impact phase - electrical voltage is applied to this coil again, whereby the respective switching times for switching off and switching on the electrical voltage from said (at least essentially) time optimal regulation can be derived.

In this case, the time-optimal control that executes the time-optimal regulation can Regarding an additional regulator, the approach of the An kers to the coil catching him, and in which the target trajectory Torias taken from the time-optimal controller and time or  are stored depending on the route, and in particular an additional regulation special in the impact phase, whereby the reg The state variables required are reconstructed by a so-called observer become.

In Fig. 2, the corresponding control concept is shown as a block diagram, the time-optimal controller is given the reference number 10 , and the control is carried out using the signals of a so-called observer 11 , whose signals are processed by an additional controller 12 which is adjacent to the controller 10 . The output variable of the control concept (or of the two controllers 10 , 12 ) is the one on the armature 4 d (cf. FIG. 1), a catching coil 4 a or 4 b applied or applied to the electrical voltage U.

The stroke of the lift valve 1 or armature 4 d corresponding position of the armature 4 d between the coils 4 a, 4 b by the path coordinate z - this is measured in a suitable manner - an input variable of the control concept described here, which the observer 11 communicated and further processed in this. For the sake of simplicity, the position of the armature is referred to directly with "z" in the following, without using the explanatory term "path coordinate".

From this path coordinate or anchor position z, the movement speed of the armature and the armature acceleration can be estimated or ascertained by one or two derivations over time t. These derived variables are determined by the observer 11 and communicated to the controllers 10 , 12 .

Another input variable of the control concept described here, which is communicated to the observer 11 and processed further in it, is - as shown in FIG. 2 - the current flow I determined in the respective coils 4 a, 4 b (cf. FIG. 1).

The time-optimal controller 10 preferably divides the entire catching process of the armature 4 d into three phases, namely:

• - firstly, a catch phase FP,
• - secondly, a subsequent braking phase BP, and
• - thirdly, a subsequent impact phase AP.

Fourthly, the latter is followed by the usual holding phase HP, in which the armature 4 d is held on the armature 4 d after it has safely hit the respective electromagnetic coil 4 a or 4 b. These individual phases are shown in FIG. 3, which will be explained in detail later. In this case, an electrical voltage is applied to the respective armature 4 d or coil 4 a or 4 b in the catching phase FP and in the impact phase AP (and thus a current flow I is initiated), while in the braking phase BP the one at the respective Coil applied voltage is reduced to the value "zero" and is therefore switched off.

The electrical current and voltage profile in the FP capture phase can be freely selected. In the braking phase BP and in the impact phase AP, additional fine control of the impact process can optionally be carried out by the additional controller 12 already mentioned. Furthermore, the speed and acceleration profile of the armature movement can be specified as a function of position or path.

According to the invention, the two switchover conditions between the three phases FP, BP, AP are determined by a so-called button (this is a map) and by a switching curve (this is a characteristic curve in this button) and ins special (ie initially only for the following explanations) by the (at least essentially) time-optimal controller 10 .

In addition to these two familiar to those skilled in control engineering Be a "button" and a "switching curve" in the following the also known term "trajectory" is used, which is the trajectory of the object to be controlled by means of the time-optimal controller 10 in the State space (later referred to as ZR net) is concerned, here is the trajectory of the armature 4 d in the state space ZR (see FIG. 3 again in advance) on its way between the two coils 4 a, 4 b.

A preferred time-optimized controller 10 will now be described in more detail below:
In order to achieve a desired reduction in its impact speed on the coil 4 a or 4 b catching it, the armature 4 d (cf. FIG. 1) must be braked in its flight phase, ie before the actual impact, in the so-called Braking phase BP. However, this braking phase BP should not extend the opening and closing times of the internal combustion engine lift valve 1 actuated by the actuator 4 more than necessary. This question about the fastest control process to reach an end position is answered by the theory of time-optimal control. Accordingly, the optimal profile of a manipulated variable is a switchover of the input variable between minimum value and maximum value, the number of switchovers depending on the system order of the controlled system.

For an aperiodic n-order system, suffice according to one known to the person skilled in the art from Feldbaum a switch-on, n-1 Um circuits and switching off the maximum manipulated variable, each for right time to all state variables from any start bring values to their final values in the shortest possible time, d. H. to lead the system to the rest position.  

The system order of the actuator 4 must therefore be known in order to design the time-optimal control. It is determined by the number of independent status variables. From a physical point of view, the state of a dynamic system is determined at all times by the energy content of the independent energy storage system in the system; the current state of the system is clearly defined by the current values of the state variables.

In the present application (cf. also FIG. 1), the magnetic flux Φ in the coil or coils 4 a, 4 b corresponds to the energy of the magnetic field, the movement speed z of the armature 4 d to the kinetic energy of the moving masses (substantially zusammenset zend from lift valve 1, the push rod 4 and c armature 4 d) and the armature position z with the potential energy of the two return springs 2 a, 2 b.

Because of the three independent energy stores, the present system of third order, so that a time-optimal 3rd order control with the State variables Φ,, z and would be possible. This possible choice of to Stand sizes are not mandatory and in particular not limited to the actual memory variables; it is essential that the system state is clearly defined by the state variables. So can e.g. B. instead of the flux Φ also the magnetic force, or the coils current I or the armature acceleration can be used.

For the further explanations, in addition to the armature position z and armature speed, the armature acceleration is selected as the third state variable for the design of the time-optimal controller 10 , since it represents an easily interpretable quantity as a direct derivation of the armature speed. In principle, the control can also be built up with any other of the variables mentioned. It is particularly advantageous if the time-optimal controller 10 is of the third order, as a result of which the delayed build-up of the magnetic field and magnetic force can be taken into account in the control concept.

According to the theory of time-optimal regulation are 3rd order for a system to determine two switching points, the first switching point being a radio tion of all three state variables (and thus one - already briefly spoken - button) and the second switching point a function of two of the three state variables (and thus one - also - also mentioned briefly - Switching curve).

For the application of the proposed time-optimal control, it must also be taken into account that the system is not in the idle state at the beginning of the control process, but already in the transition from the previous holding phase HP to the other, which now catches the armature 4 d opposite coil ( 4 b or 4 a).

It must therefore be taken into account that the electrical voltage at the coil 4 d now catching the armature is switched on during a flight movement of the armature.

. The attached and explained in the following Figure 3 shows the single pha se of the time-optimal control during the fishing operation of the armature 4 d by one of the two coils 4 a, 4 b for a system of Fig. 1:
In each case over the time t, the voltage U applied to the electromagnetic coil capturing the armature is carried up in the upper diagram, while the associated path coordinate z of the armature 4 d (= armature position z) is shown in the lower diagram. In the upper diagram, the individual phases according to the invention, namely the catching phase FP, the braking phase BP, and the impact phase AP, which are followed by the usual holding phase HP, are identified.

As far as the start of the capture phase FP at time t ₁ is concerned, at which the coil capturing the armature is supplied with electrical voltage U, this switch-on time t _{1 can in} principle be chosen freely; it only has to be ensured that the anchor 4 d can still be captured at all. For the sake of simplicity, it will be suggested here that the voltage U is switched on when the Ankerpo position z exceeds a certain, selectable threshold (this is referred to as z ₁ ). In principle, this threshold z _{1 can} also be variable, where additional conditions such as. Example, different to the force acting to lift valve 1 moving external forces (such as in particular gas forces) can be taken into into account in different operating points of the internal combustion engine.

The braking phase BP following the catching phase FP is started according to the invention by switching off the electrical voltage U as soon as the armature position z reaches a button z ₂ which is spanned by the three state variables armature position z, movement speed of the armature and armature acceleration.

In FIG. 3 an attempt has been made to graphically represent this button z ₂ in the associated state space ZR spanned by (z,,); this representation is located between the Ut diagram and the zt diagram and is associated with the time t ₂ at which the braking phase BP is started. Three possible trajectories T ₁ , T ₂ , T ₃ , ie trajectories on which the armature 4 d can move, for example, are shown in this state space ZR.

As soon as the respectively applicable, ie current, trajectory T ₁ (with i = 1, 2, 3,..., N) hits button z ₂ in state space ZR (at time t ₂ ), the electrical voltage becomes U switched off at the armature 4 d catching coil 4 a (or 4 b), ie reduced to the value "zero". This has the consequence that the armature 4 d not only does not accelerate further from the now current position z ₂ (it is now at the time t ₂ namely on the button z ₂ ) but because of the inevitable friction and eddy current desired here - Losses are braked as desired.

In order to achieve the smoothest or softest possible impact of the armature 4 d on the electromagnetic coil 4 a or 4 b currently capturing it, with the least possible time delay, the so-called impact phase AP is started after the braking phase BP, namely by How to turn on the electrical voltage U in the coil 4 a or 4 b concerned. This takes place according to the invention at the time t ₃ as soon as the armature position z reaches a switching curve z ₃ which is located in the button z ₂ and which is defined by the two state variables movement speed of the armature and armature acceleration.

This switching curve z ₃ is also assigned to the time t ₃ in the state space ZR including possible trajectories T ₁ , T ₂ , T ₃ , along which the anchor 4 d can move in this state space ZR on the button z ₂ .

Now that the armature 4 d has safely hit the respective coil 4 a or 4 b it catches or bears against it, the holding phase HP, which is already known in the prior art, is initiated, namely by switching to holding current control, what how represented by a clocked application of the respective coil 4 a, 4 b with the (equivalent) electrical voltage U.

The embodiment of the time-optimal controller 10 described here as such of a third order is the most advantageous for the actuators 4 currently under development for actuating internal combustion engine lift valves 1 . However, variants of this are also possible:
Time-optimized second-order control is also conceivable, especially if the electromagnetic subsystem can react significantly faster than the mechanical subsystem in a future actuator design. Then the actuator can be assumed to be a 2nd order system and the controller order can be reduced accordingly.

However, fourth-order time-optimal regulation is also possible. This can become necessary if the effects in a future actuator design eddy currents in the armature or in the coil to the dynamic Ver holding the actuator can not be neglected. Furthermore, one time optimal fifth-order regulation conceivable, if in a future actua the effect of eddy currents in the armature and in the coil not be neglected on the dynamic behavior of the actuator can.

Finally, "essentially time-optimal regulation" is also possible Lich, which according to the theory of control engineering is not a "pure" time represents optimal regulation, which however in the previous and following Explanations contained insights uses to the final phase loading movement of an armature of an electromagnetic actuator in particular for the actuation of an internal combustion engine gas exchange valve as ge wishes to regulate, d. H. especially the anchor impact speed to reduce.

As can be clearly seen from the above detailed description of the time-optimal control of the third order, this (essentially) time-optimal control is able to compensate for any disturbances that occur before the respective anchor trajectory T ₁ , T ₂ , T ₃ on the Button z ₂ hits.

Faults that occur later can be done with this relatively simple basic form of the regulatory concept, however, can no longer be corrected.

In order to compensate for any residual errors that may occur afterwards, the approach of the armature 4 d to the respective coil 4 a, 4 b can be monitored by the additional controller 12 (see FIG. 2) which has already been briefly mentioned, the target trajectories T ₁ from the time-optimal controller 10 and can be stored in the additional controller 12 as a function of time or distance. Depending on the size of the residual error that occurs, regulation is possible only in the impact phase AP or additionally in the braking phase BP.

In the following, an additional controller 12 acting in the impact phase AP is briefly described. The following different embodiments are possible for this:
In the form of a classic controller (PI, PD, PID controller), the additional controller 12 is designed, for example, using a linearized model of the actuator 4 for the final phase of the movement sequence of the armature 4 d. However, it can be shown that an actuator like the present one cannot be fully controlled with a classic controller, ie it is not possible to achieve impinging speeds of any desired value. The actual impact speeds depend on the respective actuator, the shape of the target trajectories and the interference forces that occur. An advantage of the classic controller that should not be underestimated, however, is its simple implementation.

In the form of a linear state controller, the additional controller 12 is also designed on the basis of a linearized model of the actuator for the end phase of the movement sequence. As a design process comes e.g. B. consider the pole specification. With such an additional controller 12 , the entire system can be completely controlled, ie, in principle, impingement speeds of any kind can be achieved. Since the design is based on a linear approach, but the actuator shows a strongly non-linear behavior, the robustness of the controller with regard to changed actuator behavior (manufacturing tolerances, aging) is low.

A non-linear status controller for the additional controller 12 is also possible, by means of which increased robustness is achieved, in particular if the status controller is preferably designed as a "sliding mode control". In such a "sliding mode controller", the fact can also be taken into account that the power electronics can only implement control signals of a certain height in clocked operation. With a design according to the "sliding mode principle" one obtains the following law:

with λ, S _min , S _max as applicable parameters. A bridge circuit is assumed as the power electronics, which has a freewheeling circuit (U = 0) and blocking circuit (U = U _min ). For the additional control of the impingement phase AP, the button z ₂ (,) of the time-optimal controller 10 can now be used as a setpoint for a three-point controller (U _min / 0 / U _max ), which corrects the current armature position z when an excessive deviation occurs yaws.

In the following, the observer 11 already briefly mentioned at the beginning of the description of the preferred embodiment (cf. also FIG. 2 and FIG. 4 explained below) will be discussed:
As is apparent from the foregoing description, both of the time-optimal controller 10 and the optionally present additional regulator 12 need to carry out their function three state variables, namely preferably z is the armature position, the moving speed of the armature 4 d and the armature acceleration . In principle, it is possible to measure these state variables using suitable sensors. However, in order to save sensors or to replace expensive sensors with inexpensive sensors, at least two of these state variables can also be reconstructed by a so-called observer 11 , who is shown in a block diagram in FIG. 4.

In this observer 11 , the actuator 4 is connected in parallel with an actuator model 114 , which is fed with the same input variable as the actuator 4 , namely with the voltage U applied to the respective coil 4 a, 4 b. The anchor position estimated on this basis is compared with the actual measured anchor position z, and the difference therefrom (z-) is fed back via a correction function 115 to the state variables of the actuator model 114 . In the event of a model error or an incorrect estimate of the initial states, the observer 11 adjusts the estimated states to the actual states on the basis of the correction function 115 . The design of the correction function 115 can be carried out by various methods of linear or non-linear control theory and will not be dealt with in more detail here.

The preferred embodiment of the actuator model 114 for determining the estimated armature position is described below. In this actuator model 114 , the mechanical and electromagnetic behavior of the actuator 4 must be taken into account. The mechanics can be simulated by a spring-mass oscillator, while the electromagnetic behavior is described using the induction equation, so that the following system of differential equations results:

with the following constants:
U: coil voltage
R: ohmic resistance of the coil
I: coil current
N: number of turns of the coil
F: magnetic flux
z: anchor position, air gap
m: sum of the moving masses
k _fr : coefficient of friction
k _sp : spring constant
and the following maps
I = f ₁ (Φ, z)
F _mag = f ₂ (Φ, z)
where f ₁ (Φ, z) and f ₂ (Φ, z) are to be determined from measurements or magnetic field simulations.

To simplify, these relationships can be described via a magnetic network and its force effect:

with A = area perpendicular to the flux at the interface between the solenoid and the air gap and
I = 1 / N. (Φ, z) .Φ
the magnetic resistance being calculated for a network according to FIG. 5.

As with the controllers 10 , 12 described so far, different embodiments are also possible with the actuator model 114 . In particular, the magnetic force, the coil current I or the armature acceleration can be used instead of the magnetic flux verwendet. It is also important here that, in addition to the mechanics, the delayed build-up of magnetic field and magnetic force is taken into account in the actuator model 114 . As with the controller 10 or 12 , a modified actuator design can also be taken into account in the actuator model 114 by adapting the model order.

According to an advantageous further development of the method according to the invention, at least one additional function can be integrated in the control concept, according to which the target trajectories of the time-optimal controller 10 do not result in an end position of the controller 10 which corresponds to the mechanical end position of the armature 4 d, as follows is described in more detail using three possible additional functions. While, according to the previous explanations, the so-called target trajectories T _i were designed so that the mechanical end position of the armature 4 d, in which it rests on one of the two coils 4 a, 4 b of the actuator 4 (and in the holding phase HP is held there), with the end position of the (essentially) time-optimal controller 10 , a control strategy deviating therefrom is also possible. The described (essentially) time-optimized controller principle allows namely a controller-specific end position, which differs from the mechanical end position of the armature 4 d, so that - in the preferred application as an actuator for actuating at least one internal combustion engine lift valve 1 (cf. again Fig. 1) - quasi any intermediate positions of this globe valve 1 between its two end positions "lift valve fully open" and "lift valve closed" can be quasi stationary.

It should be expressly pointed out that this possible addition functions (alone or cumulative) not only in the classic theory the control technology "pure" time-optimal controllers applicable or around are settable, but also in "essentially time-optimal controllers", d. H. those based on the principles described in the present invention use.  

After a first possible additional function, a so-called floating position of the armature 4 d can be set in a fictitious end position, in which the armature 4 d remains at least slightly spaced from the coil 4 a or 4 b capturing it. Thus, instead of the mechanical end position of the armature 4 d when opening and / or closing the globe valve 1, a fictitious end position in front of the respective electromagnetic coil 4 a or 4 b is started, and the armature in this intermediate position by a regulator in suspension held. Since then no impingement of the armature 4 d on the respective coil 4 a or 4 b takes place, the noise is thereby significantly reduced Lich by another.

Such floating of the armature 4 d and thus the globe valve 1, however, requires complete controllability; ie the regulator of the floating phase must therefore be a linear or non-linear state regulator, as has already been described in connection with the additional regulator 11 .

According to a second possible additional function, a floating position of the armature 4 d can be set in a (different) fictitious end position, in which the armature 4 d remains at least slightly spaced from the coil 4 a or 4 b that previously released it. Thus, for example, with an opening movement of the lift valve 1, not the opening coil 4 b (cf. again Fig. 1), but a fictitious end position of the armature near the closing coil 4 a is approached, for example, a minimal Valve stroke of the lift valve 1 corresponds to approx. 1 mm to 2 mm. If the armature 4 d and thus the lifting valve 1 is held in such a position in suspension, this function can in particular when using the actuator 4 to actuate the internal combustion engine inlet valve for improved mixture preparation and in the event of actuation of the internal combustion engine outlet valves are used to optimize the charge movement.

According to a third possible additional function, a first quasi-end position of the armature 4 d can be approached, in which the armature 4 d remains at least slightly spaced from the coil 4 a or 4 b capturing it, after which a second end position is approached which is mechanical End position of the armature 4 d corresponds. With this function, an electronic valve clearance compensation in the lift valve drive of an internal combustion engine is practically possible. Accordingly, in a closing operation of the engine lifting valve 1 , a first end position of the armature 4 d is first approached, which corresponds to the placement of the lifting valve 1 on its valve seat. Then the armature 4 d is moved into a second end position, which corresponds to its own mechanical end position. When opening the lift valve 1 , a first end position is then approached according to the valve clearance and then a second end position, which corresponds to the mechanical end position of the core 4 d on the break coil 4 b. Instead of the mechanical end positions, fictitious end positions can also be used.

Finally, the significant advantages of the method according to the invention, resulting from the use of an (at least essentially) time-optimal controller 10 and, if appropriate, the described additional elements or functions are summarized:
The proposed complete state feedback enables the Dar position arbitrarily low impact speeds of the armature 4 d on the respective electromagnetic coil 4 a or 4 b.

The inevitable extension of the flight time by the braking phase BP is kept to a minimum. The (essentially) time-optimal controller 10 defines the achievable limit.

The (essentially) time-optimal controller 10 operates with a minimum switching frequency; Switching losses in power electronics and electromagnetic interference fields are minimized.

Through an additional regulation, especially in the impact phase AP, the Robustness against manufacturing tolerances, aging and disturbing forces (such as e.g. B. acting on the globe valve gas forces) can be increased.

A further increase in robustness is provided by an additional regulation in the braking phase BP is reached.

The described possible additional function of floating, in which the armature 4 d assumes a controller end position, which differs from the mechanical end position, enables a further reduction in the noise level.

The described possible additional function of a minimal valve lift of the internal combustion engine lift valve 1 enables improved mixing preparation and charge movement in or on the internal combustion engine ne, without this requiring structural changes to the actuator 4 .

The described possible additional function of the electronic valve backlash compensation enables backlash compensation on the internal combustion engine valve, likewise without design changes to the actuator 4 . In particular, the hydraulic valve lash compensation element shown in FIG. 1 and designated by the reference number 3 is no longer required.

Furthermore, the problem of measuring all the required state variables is solved by using the observer 11 based on the measured variables Ven tilhub or armature position z and coil current I.

Finally, it should be pointed out that a large number of Details quite different from the embodiment shown can be without leaving the content of the claims.  

Reference list

1

Lift valve

2nd

a valve closing spring = (first) return spring

2nd

b Valve opening spring = (second) return spring

3rd

Valve clearance compensation element

4th

Actuator

4th

a Electromagnetic coil = normally open coil

4th

b Electromagnetic coil = normally closed coil

4th

c Push rod

4th

d anchor

10th

time-optimal controller

11

observer

114

Actuator model

115

Correction function

12th

Additional controller
AP impact phase
BP braking phase
FP catch phase
HP hold phase
I current flow in

4th

a,

4th

b
U electrical voltage on

4th

a,

4th

b
T _i

Target trajectory in ZR
ZR state space
t time
z position of the anchor

4th

d = path coordinate of the anchor position
Movement speed of the anchor

4th

d
Anchor acceleration
z ₁

Threshold = anchor position to start FP
z ₂

Button in ZR
z ₃

Switching curve on z ₂

Claims (9)

1. Control method for the end phase movement of an armature ( 4 d) of an electromagnetic actuator ( 4 ), in particular for the actuation of a gas exchange stroke valve ( 1 ) of an internal combustion engine, the armature ( 4 d) oscillating between two electromagnetic coils ( 4 a, 4 b) is moved against the force of at least one return spring ( 2 a, 2 b) by alternating energization of the electromagnet coils ( 4 a, 4 b), and with an approach of the armature ( 4 d) to the first energized coil ( 4 a or 4 b) during the so-called catching process, the electrical voltage (U) applied to the coil ( 4 a, 4 b) capturing the armature ( 4 d) is reduced, characterized in that the voltage (U) first reduced to the value "zero" and thus switched off, so that a braking phase (BP) closes at the catching phase (FP) of the catching process, and that shortly before the armature ( 4 d) hits the coil ( 4 a , 4 b) to this again electrical tension (U) and this is therefore switched on, the respective switching times being derived from an essentially optimal time control. 2. The method according to claim 1, characterized in that a time-optimal regulation of third order used. 3. The method according to claim 1, characterized in that a time-optimal control second Order or fourth order or fifth order to apply is coming. 4. The method according to claim 2, characterized in that the position of the armature (z), the sen movement speed () and the armature acceleration () are taken into account as state variables in a time-optimal controller ( 10 ). 5. The method according to any one of claims 2 or 4, characterized in that in the course of a flight movement of the core ( 4 d) towards the electromagnet coil capturing it ( 4 a, 4 b)

• - The catching phase (FP) is started by loading this coil ( 4 a, 4 b) with electrical voltage (U) as soon as the anchor position (z) reaches a selectable threshold (z ₁ ),
• - The subsequent braking phase (BP) is started by switching off the electrical voltage (U) as soon as the armature position (z) reaches a button (z ₂ ) that is above the three state variables armature position (z), speed of movement () Anchor and anchor acceleration () is spanned,
• - The subsequent impact phase (AP) is started by switching the electrical voltage (U) on again as soon as the armature position (z) reaches a switching curve (z ₃ ) located in the button (z ₂ ), which is determined by the two state variables Movement speed () of the armature and armature acceleration () is defined,
• - The subsequent holding phase (HP) by switching to holding current control is started as soon as the armature ( 4 d) is securely connected to the electromagnet coil ( 4 a, 4 b) capturing it.

6. The method according to any one of the preceding claims, characterized in that the time-optimal controller ( 10 ) to a set controller ( 12 ) is secondary, which monitors the approach of the armature ( 4 d) to the coil capturing it ( 4 a, 4 b) , in which the target trajectories (T _i ) are taken from the time-optimal controller ( 10 ) and stored as a function of time or distance, and which performs an additional regulation, in particular in the impact phase (AP). 7. The method according to any one of the preceding claims, characterized in that the state variables required by the controller ( 10 , 12 ) are reconstructed by an observer ( 11 ). 8. The method according to any one of the preceding claims, characterized in that at least one additional function is integrated, according to which the target trajectories (T _i ) of the time-optimal controller ( 10 ) does not correspond to an end position corresponding to the mechanical end position of the armature ( 4 d) of the controller ( 10 ). 9. The method according to claim 8, characterized in that at least one of the following functions can be generated by the additional function:

• a floating position of the armature ( 4 d) in a fictitious end position, in which the armature ( 4 d) remains at least slightly spaced from the coil ( 4 a, 4 b) capturing it,
• a floating position of the armature ( 4 d) in a fictitious end position, in which the armature ( 4 d) remains at least slightly spaced from the coil ( 4 b, 4 a) that previously released it,
• - Moving to a first quasi-end position of the armature ( 4 d), in which the armature ( 4 d) remains at least slightly spaced from the coil ( 4 a, 4 b) catching it, and then moving to a second one End position that corresponds to the mechanical end position of the armature ( 4 d).