DE102017210479A1 - Valve control with freely definable dither signal - Google Patents

Abstract

The invention relates to a computing unit (100) for actuating a particularly hydraulic valve (200) which is set up to set a value of a current (I) for an electromagnetic actuator (210) of the valve (200) by a drive signal (x). and which is set up to superimpose a dither signal (D) on the drive signal (x), wherein the arithmetic unit (100) is further configured to generate the dither signal (D) with a freely definable signal form.

Description

The present invention relates to a computing unit, in particular a control unit, for controlling a, in particular hydraulic, valve an arrangement of a valve and such a computing unit and a driving method.

State of the art

Hydraulic valves such as continuous-pressure valves, pressure control valves or as continuous-way or control valves are usually controlled using a computer or a corresponding control device, in particular also regulated. Such a hydraulic valve has a valve actuator consisting of an electromagnetic drive (alternatively: actuator) and a corresponding hydraulic actuator (in particular, for example, a piston or cone), by means of which, by setting a specific current, a desired size, such as a. Volume flow or pressure, can be adjusted. The current for the magnetic actuator can be specified by applying a voltage, in particular in pulse width modulated form.

In such valves, there is the problem that, for example, due to friction effects, breakaway effects or hysteresis of the valve actuator does not move as desired. For this purpose, it is known to superimpose a so-called dither signal on the current or, in general, a manipulated variable. Such a signal is a kind of noise or jitter that results in a slight dithering movement of the valve actuator. The problems mentioned, such as breakaway effects, are avoided or at least reduced in this way.

The use of such a dither signal in a hydraulic valve is for example from DE 39 39 857 A1 known. From the DE 44 23 102 B4 It is also known to reduce the frequency of such a dither signal with increasing drive current. However, in particular with slow movement or small opening of the valve actuator and the drive current required for this purpose, the use of such a dither signal can lead to unwanted effects (for example so-called "seat bounces") and insufficient dithering effect. If the current controller behavior is unfavorable, a wrong (minimum) current may also be generated.

In addition, you can physically observe a clearly limited excitation behavior in simple end stage technologies, which in turn can lead to an increased impairment of the overall behavior.

Against this background, a possibility should be given to be able to control valves even better or more accurately.

Disclosure of the invention

According to the invention, a computing unit for controlling a (in particular hydraulic) valve, an arrangement comprising a valve and such a computing unit and a drive method having the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

In the context of the invention, a value of a current for the electromagnetic actuator (that is to say for a coil of the electromagnetic actuator) of the valve, such as, for example, an arithmetic unit set up for implementation, is generated by a drive signal. Proportional valve, which may also include a valve actuator (in particular also a valve piston or a poppet) or can move a Ventilaktor set. In addition, a dither signal is superimposed on the drive signal. Such a computing unit may in particular be a control unit or an electronic control unit, which may for example also be attached to the valve.

Furthermore, it is now provided to generate the dither signal with a freely definable signal form. The term "signal form" is to be understood here in particular as the course of the signal, in particular during a period. In the case of a pulse width modulated signal or a pulse width modulated control, which in particular a voltage can be applied to the electromagnetic actuator, it is expedient if the dither signal or a dither sampling frequency is synchronized with the pulse width modulated signal. However, such a synchronization is usually only necessary if the dithering is done via a so-called "duty cycle addition". On the other hand, with superimpositions on much higher fundamental PWM frequencies (for example dither 250 Hz and PWM 10 kHz), synchronization is not absolutely necessary. The predetermining or setting of the current can also take place, in particular, in the context of closed-loop control, in which case the voltage to be applied to the electromagnetic actuator or the drive signal, such as a duty cycle for a pulse width modulated signal, can be used in particular as a manipulated variable. By way of example, a pressure or a position can then be adjusted or regulated, for. In particular, a current regulator subordinated to the pressure or position controller can be provided.

The generation of a dither signal with a freely definable signal shape now makes it possible to respond to a wide variety of variables or changes in the operation of the hydraulic valve and in particular to use such waveforms, in which unwanted effects, such as so-called "seat bounces, occur even with small opening of the valve actuator ", Or insufficient dithering be avoided. Thus, for example, in the case of a dither signal having a symmetrical signal shape and a low current for the magnetic actuator in the case of a pulse-width-modulated drive, the mean value for the current would increase because the negative half cycle of the amplitude of the dither signal would be greater than that of the average duty cycle , With the invention, however, it is now possible to use, for example, asymmetric waveforms with which the problem addressed can be avoided. For example, here a pulse-shaped dither signal with a large positive amplitude and several small negative amplitudes can be used.

In general, significantly more different cases can be addressed in the control of hydraulic valves in this way. However, this would not be possible without the use of a triangular or rectangular shape for the waveform.

It is preferred in this case if a memory is provided in which one or more freely specifiable signal forms, in particular in the sense of a pattern or samples, are deposited or can be deposited. In this way, it is then very easy to select a desired signal shape which is used for the dither signal.

Preferably, a signal generator for generating the dither signal is provided with the freely definable waveform. Such a signal generator can be formed by suitable hardware components. However, it is also conceivable to provide such a signal generator by software. In both cases, for example, it is also possible to fall back on the signal forms or patterns lying in the mentioned memory in order to generate a desired dither signal and to superimpose it on the drive signal.

Advantageously, the signal shape and / or an amplitude and / or a frequency of the dither signal can be changed, preferably dynamically, in particular also during use or activation of the valve. It is likewise preferred if these signal variables can be generated as a function of at least one variable occurring during the activation of the valve and, in particular, also changed. In particular, the current (possibly also a desired value for this) and / or a temporal change of the current and / or a temperature of the valve and / or a supply voltage for the arithmetic unit come into consideration as the at least one variable occurring during the activation of the valve. In particular, historical data of the valve, such as device runtime, switching cycles, previously reached maximum temperature, etc., and / or data or signals of a higher-level controller are also suitable. This makes a particularly accurate and efficient operation of the valve possible. In particular, for example, for rapid movements of the valve conventional waveforms such as a triangular or rectangular shape can be used for a slower movement, however, then the already mentioned asymmetric or other suitable waveforms, in particular sawtooth or inverse sawtooth. In addition, a specific valve can also be operated as efficiently as possible at different operating points. For a detailed description and concrete implementation options, reference is made to the following statements.

It is also advantageous if the signal shape is generated as a function of a valve type and / or operating parameters of the valve. As a valve type come here in particular a continuous-pressure valve, a pressure control valve, a continuous-way valve and a control valve in question. In this way, the invention can be used very flexibly and for different types of valves and then especially for those valves with different operating parameters, which may for example also depend on the dimensions of the valve can be used.

The implementation of the invention in the form of a computer program is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore already exists. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories, such as e.g. Hard drives, flash memory, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of embodiments in the drawing and will be described in detail below with reference to the drawings.

list of figures

• 1 schematically shows a computing unit according to the invention in a preferred embodiment and a hydraulic valve.
• 2a and 2 B schematically show sections of further preferred embodiments of a computing unit according to the invention.
• 3a and 3b schematically show sections of further preferred embodiments of a computing unit according to the invention.
• 4a to 4f show different waveforms for use with a computing unit according to the invention.
• 5 shows a superposition of drive signal and dither signal.

Detailed description of the drawing

In 1 are schematically a computing unit according to the invention 100 in a preferred embodiment and a (here hydraulic) valve 200 shown. The arithmetic unit 100 can also be part of the valve 200 be or, for example, arranged thereon. This is then also an arrangement according to the invention in a preferred embodiment. At the hydraulic valve 200 it may be, for example, a pressure control valve or a directional control valve, which is not relevant for the general explanation of the invention below.

The arithmetic unit 100 , which may in particular also be a control unit or a control unit, is supplied with voltage by means of a supply voltage Uv. In the arithmetic unit 100 are now a parent controller 110 , depending on the type of valve, for example, a pressure or position controller, and a controller 110 subordinate current controller 120 intended. The regulator 110 may be, for example, a PI or PID controller. In simple magnetic current regulators such as for a pressure valve is usually no higher-level controller 110 available.

The regulator 110 receives as an input a setpoint y _should which, depending on the type of valve, may for example be a setpoint for a pressure or a position. This setpoint y _should is usually specified by a specific application. Furthermore, the controller receives 110 as an input one to the setpoint y _should associated actual value y _is Thus, for example, an actual value for a pressure in the valve or a position of a Ventilaktors. This actual value y _is can be detected using, for example, a suitable sensor.

The regulator 110 Now gives as output a setpoint I _should for a stream I out, which in a magnetic actuator 210 of the valve 200 should flow. This setpoint I _should is now as an input to the current regulator 120 , for example a PID or PI controller. As a further input receives the current controller 120 one to the setpoint I _should associated actual value I _is of the electricity. An output of the current controller 120 is a drive signal, here for example a duty cycle x for a pulse width modulated drive for applying a voltage U to the magnetic actuator 210 , At the duty cycle x this is a manipulated variable.

Furthermore, now is a signal generator 140 provided by means of which a dither signal D can be generated, which then the drive signal or duty cycle x is superimposed. This is a superimposed drive signal or a superimposed duty cycle x ' get that then a power amplifier 130 drives to the voltage U in particular in pulse width modulated form to the magnetic actuator 210 to apply. A frequency of the pulse width modulated signal (PWM signal) generated thereby can be constant. This usually depends on the specific parameters of the components used.

The signal generator can, for example, to a memory 141 access, in which various waveforms can be deposited, as will be explained later.

In the 2a and 2 B are now schematic sections of further preferred embodiments of the invention shown. In particular, here are each parts of the control loop for the current controller 120 out 1 shown.

At the in 2a shown section is the setpoint I _should before putting the current regulator 120 is fed, nor by two members 121 and 122 guided. At the limb 121 For example, it may be a ramp with a PT1 link to smooth the reference variable. At the limb 122 it can be a linearization to achieve an adaptation of the reference variable-controlled variable allocation.

Furthermore, here are a damping 123 and a factor 124 provided by means of which the signal generator 140 output signal can be adjusted to the dither signal D which then the drive signal x is superimposed to receive. With the damping 123 can be one in particular dynamic adjustment of the dither signal can be achieved in order to take into account a dependence of the dither effect on an excitation by the reference variable (ie, a setpoint value) and, to a lesser extent, also a disturbance variable. By the factor 124 one obtains a setpoint-dependent amplitude of the dither signal.

In 2 B is one to 2a very similar embodiment shown, however, the attenuation 123 and the factor 124 not here depending on the setpoint I _should of the current, but of the to a control variable such as pressure or position associated setpoint y _should specified. It is for the setpoint y _should another ramp 125 provided for a corresponding timing.

In the 3a and 3b are shown schematically cutouts of further preferred embodiments of the invention. In particular, here are each parts of the control loop for the current controller 120 out 1 shown.

These embodiments are similar to those of 2a and 2 B , but here are the influences of the setpoints I _should respectively. y _should on the factor 124 designed differently, namely even before the linearization 122 , In addition, the setpoints have I _should respectively. y _should an influence on the choice of the signal form of the dither signal, here over the signal generator 140 ,

For a more detailed description of the damping and the factor, reference is made to the following statements.

The 4a to 4f show different signal forms by way of example D ₁ to D ₆ for use in the invention. In particular, for example, suitable patterns of these signal forms can be stored in the mentioned memory. Depending on the signal generator, however, direct generation is also possible.

The waveform D ₁ according to 4a This corresponds approximately to an inverted SägezahnForm with amplitude A , The waveforms D ₂ and D ₃ according to 4b and 4c correspond to usual shapes with ideal sawtooth or triangle. The waveforms D ₄ and D ₅ according to 4d and 4e correspond to an asymmetric or symmetrical pulse shape. The waveform D ₆ according to 4f corresponds to a completely free predetermined form.

It is also conceivable that the original signal form of the dither signal in the superposition no longer appears completely, for example because of edge effects. For example, if the duty cycle is within a range of [0; 1], a dither signal in the form of a symmetrical (inverse or regular) sawtooth (similar to FIG 4a . 4b respectively. 4c shown) at very small duty cycles 0 and at very high duty cycles 1 cut off.

Thus, when decreasing the duty cycle, a signal waveform is created which is initially in the 4d shown course corresponds. It will be neither small nor large x ' limited and the actual course of the output duty corresponds to the overlay. The lower the current setpoint and thus the duty cycle, the closer the resulting signal waveform approaches x ' a (positive) pulse train, so that the drive signal x apparently only short, positive impulses are superimposed. In order to increase this effect, one could additionally use the multiplier function for these small setpoint ranges 124 achieve an increase in the positive momentum.

With reference to the embodiments shown, the mode of operation of the controller structure presented here will now be explained in more detail. For implementation, it is expedient to double a fundamental frequency of the PWM signal from, for example, the usual 488 Hz to 976 Hz. In the next step, this makes it possible to fix the dither signal to an overlapping frequency which is still effective on the one hand, and which, on the other hand, also lies above possible device-specific natural frequencies as far as possible. In principle, the superimposition can be independent of the basic current control and vice versa. Generally speaking, the fundamental frequency of the PWM signal can be a multiple of the dither sample frequency. However, as mentioned, the invention also basically works with a high basic PWM frequency and a not necessarily synchronized dither signal. The dither sampling frequency is the number of sampling steps with which the step size of the dither signal is determined (comparable to the number of steps in FIG 4a) ,

The duty cycle x of the current controller 120 becomes the dither signal D superimposed. In 5 For this purpose, a drive signal or duty cycle x represented by the dither signal with the shape D1 according to 4a or approximately the shape D ₂ according to 4b is superposed, creating a superimposed drive signal x ' is obtained. At the input signal x this is a horizontal (possibly wavy) line whose amount (or height or offset) corresponds to the mean magnet current or duty cycle.

The signal can also assume an asymmetrical surface area in certain applications. In order to achieve a certain behavior, it may be necessary, for example, to superimpose a dither signal that is not averaged. having symmetrical amplitudes or areas. For example, it may be desirable for a directional component of the heterodyne signal to predominate if the temporal behavior of the manipulated variable is direction-dependent.

The beat signal should be synchronized to the actual PWM signal so that the corresponding beat signal is present for each PWM pulse. The synchronization is particularly preferred for the case in which a dither signal is to be superimposed with a digital current regulator on a relatively slow basic PWM signal. Only one duty cycle setpoint is accepted or output within a PWM cycle. If the value changes in the meantime or if the overlay signal is switched on at different times, then this is not changed and thus it is not guaranteed that the overlay signal is output in the desired form. If, on the other hand, a PWM signal with a higher fundamental frequency or a DC voltage is used, this synchronization may not be necessary.

Another possible influencing factor for the determination of the superimposition is the consideration of state variables or interference variables on the actual control signal, ie the current or the pressure or the position, such as, for example, for rapid volume flow changes in a pressure regulating valve. In the case of a pressure-return valve, the size can be determined, for example, from internal values of the controller and taken into account in the case of the dither signal.

The frequency of the dither signal D results for the mentioned example with 976 Hz and an integer divisor. For example, in 4a In the case shown, the divider is six. The frequency of the dither signal D thus results in 162.67 Hz. With such a divider, the resolution of the waveform can be determined.

The shape of the dither signal to be superimposed corresponds to 4a in approximation of an inverse sawtooth. The shape itself becomes the drive signal or the duty cycle due to the PWM signal-synchronous addition of one value each x generated for the duration of a pulse. The illustrated waveform "inverse sawtooth" has been found to be particularly suitable for a steady-state pressure relief valve and / or pressure control valve in combination with a single-transistor power amplifier, but may also be advantageous in other power amplifiers. The use of the PWM signal-synchronous addition is advantageous regardless of the signal form.

Essential aspects here are firstly the slow current-decay rate compared to the current build-up and secondly the fact that the dynamic behavior of the armature movement (in the case of the electromagnetic actuator) is determined differently depending on the direction. Used here is the rapid increase in current against a hydraulic counterforce for a short movement impulse, while the current I , which is responsible for the magnetic force decreases more slowly at the time of the weaker damped backward movement.

For other applications, such as mid-position spool valves, other waveforms, such as the symmetric pulse, may be used 4e be more suitable. The in the 4a to 4f shown absolute values, as well as the course of the waveform itself, be adjustable. It is conceivable, however, to specify certain restrictions with regard to permissible values. However, the relative values of the individual pulses relative to one another are particularly important.

The fundamental superposition signal, as it is from the signal generator 140 is generated, then with an example of the setpoint I _should dependent factor 124 multiplied. This results in a setpoint-dependent amplitude of the dither signal, which generates a pressure oscillation that is constant over the widest possible range. Alternatively, the controller may also be prior to linearization 122 be tapped.

Since the effect of the dither signal behaves differently depending on the excitation by the reference variable and, to a lesser extent, possibly also that of the disturbance, a dynamic or quasi-dynamic adaptation of the superimposition is advantageous. This is done by the signal generator 140 generated signal - in addition to the factor 124 - With a dependent on the temporal behavior of the reference variable factor, the damping 123 , multiplied. It should be noted that not every small setpoint change should lead to an increase in attenuation as this can lead to noise.

For jumps of the reference variable, so here the setpoint I However, the damping should be activated. Thus, in principle, depending on a change amplitude and the frequency of occurrence, a damping can be generated. An increase in the attenuation can, for example, be ramped. If there is no further excitation by a reference variable (eg by a jump or a ramp), then the last set attenuation may, for example, decay with a PT1 behavior. Further occurrence of an event that results in an increase in attenuation may then produce a further increase in attenuation until, for example, a maximum attenuation value attributable to the event.

As already mentioned, dependencies of the dither signal on a temperature, in particular of the valve, the fluid or another component, or the supply voltage can also be used. Also conceivable are historical data of the valve and / or data or signals of a superimposed regulator. In the case of the supply voltage, for example, a further factor for the dither signal can be provided with which the signal generated by the signal generator is modified, for example multiplied.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3939857 A1 [0004]
• DE 4423102 B4 [0004]

Claims (15)

Arithmetic unit (100) for actuating a valve (200) which is set up to set a value of a current (I) for an electromagnetic actuator (210) of the valve (200) by a drive signal (x) and which is adapted to the control signal (x) a dither signal (D) to be superimposed, characterized in that the arithmetic unit (100) is further adapted to the dither signal (D) with a freely definable signal form (D ₁ , D ₂ , D _3rd D ₄ , D ₅ , D ₆ ). Arithmetic unit (100) according to Claim 1 , with a memory (141) in which one or more freely predeterminable signal forms (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) are deposited and / or can be stored. Arithmetic unit (100) according to Claim 1 or 2 , with a signal generator (140) for generating the dither signal (D) with the freely definable signal form (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ). Arithmetic unit (100) according to one of the preceding claims, wherein the signal form an asymmetric waveform (D ₄ , D ₆ ) and / or a sawtooth shape and / or an inverse sawtooth shape and / or a pulse-shaped waveform having a positive amplitude and a plurality of negative amplitudes smaller than the positive amplitude, includes. Arithmetic unit (100) according to one of the preceding claims, which is further adapted to the waveform (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) and / or an amplitude (A) and / or a frequency of the dither signal (D) during use with the valve (200). Arithmetic unit (100) according to one of the preceding claims, which is further adapted to the waveform (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) and / or an amplitude (A) and / or a frequency of the dither signal (D) as a function of at least one variable occurring during the activation of the valve (200). Arithmetic unit (100) according to Claim 6 , which is further adapted to the waveform (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) and / or the amplitude (A) and / or the frequency of the dither signal (D) in dependence to change from the at least one size, in particular dynamically. Arithmetic unit (100) according to Claim 6 or 7 , wherein the at least one size of the current (I) and / or a temporal change of the current (I) and / or a temperature of the valve (200) and / or a supply voltage (Uv) for the arithmetic unit (100) and / or historical Data of the valve and / or data or signals of a higher-level controller comprises. Arithmetic unit (100) according to one of the preceding claims, which is further adapted to the waveform (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) depending on a valve type and / or operating parameters of the valve ( 200). Arithmetic unit (100) according to one of the preceding claims, which is adapted to generate by means of the drive signal (x) a pulse width modulated signal to apply a voltage (U) to the electromagnetic actuator (210), wherein the dither signal or a dither Sampling frequency (D) are synchronized with the pulse width modulated signal. Arithmetic unit (100) according to one of the preceding claims, which is set up to predetermine and / or adapt the dither signal as a function of at least one state and / or disturbance variable. Arithmetic unit (100) according to one of the preceding claims, wherein the valve (200) is designed as a continuous-pressure valve, as a pressure control valve, as a continuous-way valve or as a directional control valve. Arrangement comprising a valve (200) and a computer unit (100) according to one of the preceding claims. A method for driving a valve (200), wherein a value of a current (I) for an electromagnetic actuator (210) of the valve (200) is set by a drive signal (x), wherein the drive signal (x) a dither signal (D ) is superimposed, characterized in that the dither signal (D) with a freely definable waveform (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ ) is generated. Method according to Claim 14 which is derived from an arithmetic unit according to one of Claims 1 to 12 is carried out.

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