DE102011116819A1 - Method for controlling piezoelectric actuator for e.g. proportional valve of valve device for controlling e.g. fluid cylinders, involves adding preset waiting time to point of time of occurrence of difference in threshold value interval - Google Patents

Abstract

The method involves determining a reference value-actual value difference. Supply of electrical energy to adjusting units (11, 12) at a control time point is changed if the difference exceeds a preset threshold value or falls below another preset threshold value. The change of the supply of electrical energy is completed if the difference occurs in a threshold value interval between the threshold values. A preset waiting time is added to a point of time of the occurrence of the difference in the threshold value interval while the supply of electrical energy is not changed. An independent claim is also included for a valve device.

Description

The invention relates to a method for actuating an electrically operable actuating means for a fluid control valve, wherein the actuating means is coupled to a valve body which is arranged movably in a valve chamber of a fluid control valve for influencing a fluidic cross section between an input port and a working port relative to a valve seat to influence a fluid flow from a fluid source to a fluid consumer and a fluid effluent from the fluid consumer into a fluid sink, comprising the steps of: determining an actual pressure value provided to the fluid consumer, in particular in the valve space, comparing the actual pressure value with a predefinable desired pressure value and determining a setpoint-actual value difference and changing a supply of electrical energy to the actuating means at a first activation time, wherein a change in the provision of electrical energy is provided when the setpoint Istwer t difference exceeds a first predetermined threshold or falls below a second predetermined threshold. Furthermore, the invention relates to a valve device.

With such a method, for example, a 3/3-way fluid control valve can be operated, with the aid of which a fluid flow to a consumer and is influenced by a consumer. The 3/3-way fluid control valve has a valve space in which first actuating means for influencing a free fluid cross section between a supply port, to which a source of pressurized fluid is connectable, and a working port, which is connected to the fluidic consumer arranged is. Further, a second adjusting means is provided in the valve space, which is for influencing a free fluid cross section between the working port and a vent port, can be discharged through the pressurized fluid in a fluid sink as a fluid tank or in the environment. The adjusting means are electromechanical transducers that convert a supplied electrical energy into a movement, for example, a coil drive or a piezo drive. By suitable control of the first and the second actuating means, each associated with a valve body which can be sealingly applied by the movement of the respective actuating means to a valve seat or removed therefrom to effect the desired influence of the fluid flow, the connected at the working port fluidic consumers are ventilated or vented, for example. The control of the two actuating means takes place as a function of a predefinable desired pressure value and of a measured actual pressure value, which are set in relation to one another in order to determine therefrom a manipulated variable with which the actuating means are actuated. To avoid permanent pressure fluctuations, a three-point control is provided, in which only a control of the actuating means takes place when the setpoint-actual value difference exceeds a predetermined first threshold or falls below a second predetermined threshold. For setpoint-actual value differences, which lie between the first and the second threshold, no activation of the actuating means takes place.

The DE 19516627 A1 discloses a method for controlling an output of a process comprising the steps of: detecting a sample of the output, comparing the sample of the output with a setpoint and determining a setpoint deviation, calculating a value of a setpoint dependent on the determined setpoint deviation such that the output of the process is inputting the set value, and inputting the manipulated variable into the process, after a latency has elapsed, re-determining a value of the manipulated variable, the waiting time being variable and based on the difference between the value of the manipulated variable and an earlier value of the manipulated variable Calculated based on an earlier sample.

The object of the invention is to provide a method for controlling an electrically operated actuating means of a valve device and a valve device, which have an improved control behavior with dynamically changing boundary conditions.

This object is achieved according to a first aspect of the invention with the features of claim 1. It is provided that the change in the provision of electrical energy is terminated when the setpoint-actual value difference in a threshold interval between the first and the second threshold occurs and that at the time of entry of the setpoint-actual value difference in the threshold interval predeterminable waiting time followed, during which there is no change in the provision of electrical energy.

By means of this measure it is achieved that during a dynamic change of the boundary conditions for the fluid control valve to be actuated according to the method, for example by changes of the desired pressure value and / or the actual pressure value, a reaction delayed by the waiting time takes place. As a result, an undesirable overshoot of the fluidic system, which is formed from the fluid control valve and the fluidic consumer, can be avoided.

When changing the supply of electrical energy can be a provision electrical energy starting from a state to which the or the adjusting means were not subjected to electrical energy. Alternatively, the change in the provision of electrical energy may mean a complete shutdown of a previous supply of electrical energy. In a further alternative, the change in the provision of electrical energy may mean an increase or reduction of an electrical voltage and / or a current flow that is provided to the adjusting means.

Advantageous developments of the invention are specified in the subclaims.

It is useful if, during the waiting time, a determination of the target actual value difference is made and that after a leakage of the setpoint actual value difference from the threshold interval and a subsequent reentry of the target actual value difference in the threshold interval during the waiting time a restart the waiting time takes place. This approach is based on the consideration that there is no need for influencing the re-entry of the desired-actual value difference in the threshold interval during the waiting time for the fluidic system until the end of the subsequent waiting time. The waiting time can be selected constant, in particular be predetermined by parameterization. Alternatively it can be provided that the waiting time is adapted dynamically to the requirements of the fluidic system, for example as a function of the pressure which the fluid source provides and / or of other operating parameters. Furthermore, it can additionally or alternatively be provided that the subsequent waiting time is set as a function of when the re-entry of the setpoint-actual value difference into the threshold interval during the previous waiting time has taken place and / or how long the setpoint-actual value difference during the waiting time was outside the threshold interval.

It is expedient if a change amount for the provision of electrical energy is selected independently of the activation time or as a function of the nominal value-actual value difference. By way of example, either at the first activation time or after one or more waiting time intervals have elapsed at a second activation time, the actuating means is actuated with a predefinable and always the same amount of electrical energy. Accordingly, the actuator provided with the fluid control valve is preferably operated in the manner of a switching valve, which allows either a blocking or a complete release of a fluidic flow cross-section between the input port and the working port.

Alternatively, it can be provided that the change in the provision of electrical energy for the first or second activation time is dependent on the setpoint-actual value difference. In this case, the fluid control valve is preferably designed as a proportional valve, which is adapted to adjust the free fluid cross section between the input port and the working port between a blocking position and a release position gradually or continuously freely selectable.

It is advantageous if the change in the provision of electrical energy takes place as providing or switching off a predefinable electrical supply voltage. Thus, only two different states of the provision of electrical energy are provided to the actuating means, either no provision of electrical energy or provision of electrical energy at a predeterminable level, for example a predeterminable voltage level. In this way, the structure of the provided for providing the provision of electrical energy control unit can be kept simple, since no complex, for example stepless, influencing the provision of electrical energy is necessary.

Preferably, the waiting time is given by a, preferably adjustable, timer. The timer can be realized electrically or electronically, preferably the timer is implemented in a program sequence of a microprocessor or microcontroller, which is used for the control of the actuating means, and can thus be adjusted by parameterization.

The object of the invention is achieved according to a second aspect with the features of claim 6. In this case, a valve device is provided with a control unit for providing control signals to a fluid control valve and a fluid control valve, wherein the fluid control valve comprises an electrically operable actuating means which is coupled to a valve body which is in a valve chamber of the fluid control valve for influencing a fluidic cross-section between an input port and a working port is movably disposed relative to a valve seat to affect a fluid flow from a fluid source to a fluid consumer and a fluid flow from the fluid consumer into a fluid sink and wherein the control unit is designed for carrying out the method according to claims 1 to 5. The valve device can be designed as a single module for controlling one or more fluid consumers. It can be provided that by means of one or more controls such as an electric push-button control of the valve device by an operator can take place in order to influence this influence on a fluidically coupled to the valve means fluid consumers such as a fluid cylinder or a fluid motor. Such an arrangement is provided for example in a personal support device such as a pneumatically adjustable hospital bed. Alternatively, the valve device is designed for integration into a module chain, which can be constructed from a plurality of at least substantially identically designed valve devices and a control device. As a result, for example, a plurality of fluid consumers such as linear actuators in a device, for example in a production machine, are controlled centrally. By implementing the method according to the invention in the control unit of the valve device, a control behavior for the individual fluid consumers is achieved, in which unwanted pressure fluctuations are at least largely suppressed.

It is expedient if the adjusting means is designed as a piezoelectric actuator. A piezoelectric actuator allows a very fast adjusting movement for the coupled valve member and thus ensures that a provided drive signal leads in a short time to the desired adjusting movement of the valve body relative to the valve seat. Thus, the waiting time and the waiting time can be set directly because virtually no latency of the actuating means must be considered.

It is advantageous if a pressure sensor which is electrically coupled to the control unit and which is designed to provide the actual pressure value is arranged in the valve space. As a result, a simple construction of the valve device and a simple electrical connection of the valve device are ensured.

An advantageous embodiment of the invention is shown in the drawing. Hereby shows:

1 a schematic sectional view through a valve device and

2 a signal waveform diagram for a known control of the valve device according to 1 and

3 a signal waveform diagram for an inventive control of the valve device according to 1 ,

In the 1 is a fluidic system 1 shown schematically, the one valve device 2 and a fluid consumer 3 includes. The valve device 2 includes a control unit 4 for providing control signals to a fluid control valve 5 is formed and a fluid control valve 5 , The fluid control valve 5 is exemplified as a 3/3-way valve and has a supply connection 6 , a work connection 7 and an output terminal 8th on. At the supply connection 6 is an example of a trained as a compressed air source fluid source 9 connected. At the work connection 7 is the exemplified as a pneumatic cylinder fluid consumers 3 connected. At the output terminal 8th is an example of a silencer 10 attached, which ensures an attenuation of the noise occurring in this case with an outflow of fluid into the environment. The control unit 4 is electrically connected to the fluid control valve 5 connected to there a first and a second adjusting means 11 . 12 to control and signals from a pressure sensor 15 capture.

The first and the second adjusting means 11 . 12 are exemplified in each case as a bending beam made of piezoelectric material and in one of a valve housing 13 enclosed valve space 14 arranged. Both adjusting agents 12 . 13 is in each case at a front, freely movable end of a valve body 16 . 17 assigned. This valve body 16 . 17 can depend on a voltage supplied by the control unit 4 is made available by a voltage-dependent bending movement of the respective actuating means 11 . 12 from a respective associated valve seat 18 . 19 lifted off or on the valve seat 18 . 19 be pressed. As a result, a fluidic cross section through one at the respective valve seat 18 . 19 opening out fluid channel 20 . 21 be set between a blocking position and a release position. The two fluid channels 20 . 21 each lead into the valve chamber 14 , In the valve room 14 is also the pressure sensor 15 arranged to detect the actual pressure in the valve chamber 14 is trained.

With the help of the two adjusting means 11 . 12 and at the fluid channels 20 . 21 connected components (fluid source 9 and silencers 10 ) may be a fluid flow from the fluid source 9 through the valve chamber 14 to the fluid consumer 3 and, alternatively, a fluid effluent from the fluid consumer 3 through the valve chamber 14 be evoked into the environment. This can cause a fluid pressure at the work connection 7 and thus at the fluid consumer 3 be set with the working connection 7 via a fluid line 22 connected is.

The pressure in the fluid space 14 is determined by the position of the two actuating means 11 . 12 , by the properties of the fluid source 9 as well as by the operating state of the fluid consumer 3 affected. Usually, the fluid source provides 9 a substantially constant pressure, allowing a change in the pressure conditions in the valve chamber 14 from external forces on the fluid consumer 3 and / or the position of the two actuating means 11 . 12 depends. By an introduction of external forces on the fluid consumer 3 , For example, by loading the designed as a headboard pivoting portion 23 of the illustrated example hospital bed 24 with a weight force, can increase the pressure in the valve chamber 14 occur. Additionally or alternatively, an unillustrated user by pressing a bedside 24 provided keypad 25 Control commands to the control unit 4 send to the swiveling section 23 with the help of a linear movement of the fluid consumer 3 lower or raise. The control operations occurring in such a change of the target pressure value in the control unit 4 are exemplary in the 2 shown.

The 2 shows a waveform diagram 28 , which reproduces the control behavior of a known three-level controller according to the prior art. In the 3 is a waveform diagram 29 illustrated, the exemplary control behavior of the invention and in the control unit 4 implemented controller shows.

The in the waveform diagram 28 in the 2 given starting situation is exemplified in that at the time t0a a sudden change in a target pressure value 31 from a lower level to a higher level. As a result, at time t0a, a setpoint-actual value difference occurs between the setpoint pressure value 31 and an actual pressure value 30 on, since the actual pressure value 30 suddenly below the target pressure value 31 lies. The nominal pressure value 31 is from the time t0a exemplarily at a constant level. The change of the target pressure value 31 at time t0a, for example, due to a user input via the in 1 illustrated keypad 25 he follows. While in the 2 shown period from t0a to t11a and t0b to t8b according to the 3 no further setpoint change takes place.

Due to the difference between the actual pressure value 30 and the desired pressure value 31 at time t0a generates the control unit 4 a to the first actuating means 11 directed control signal 34 to increase the pressure in the valve chamber 14 to achieve by supplying pressurized fluid and thus to reduce the setpoint-actual value difference.

Therefore, the first actuating means opens 11 the fluidic cross-section between the fluid source 9 and at the work connection 7 connected fluid consumers 3 , so that the desired pressure increase can take place. As the valve room 14 has a very small volume and a pressure equalization with the fluid line 22 and the fluid consumer 3 with a time delay that is significantly greater than the switching time of the actuating means 11 . 12 is found by the opening process in the valve chamber 14 a sudden pressure increase in the form of a positive pressure peak instead. It exceeds the one in the valve chamber 14 measured fluid pressure quickly reaches the lower threshold 32 , for example, equidistant spaced by a predetermined amount to the setpoint 31 can be settled. When the lower threshold is reached 32 at time t1a is from the control unit 4 a to the first actuating means 11 directed control signal 34 provided to further fluid supply into the valve space 14 to interrupt. This will be the first actuating means 11 brought back into a position in which no further fluid supply into the valve chamber 14 he follows. However, between the detection of the actual pressure value 30 in the valve room 14 and the shutdown of the fluid supply in the valve chamber 14 a certain amount of time passed, within which the actual pressure value 30 in the valve chamber has continued to rise and also an upper threshold 33 also equidistant from the setpoint by a predeterminable amount 31 can be settled. As a result, another switching operation, but now with a switching signal 35 for the second adjusting agent 12 in the control unit 4 caused, which serves the pressure in the valve chamber 14 again below the upper threshold 33 adjust. This allows the fluidic system 1 settle only after some time and there are a variety of switching operations (venting and venting) for the two actuating means 11 . 12 , Among other things, to an undesirable emission of switching noise due to the high frequency recurring operation of the actuating means 11 . 12 leads.

To reduce these noises, the driving method according to the invention is used, as shown in the 3 is shown. This results in the waveform diagram 29 illustrated switching behavior for the actuating means 11 . 12 , Starting from the same starting situation as with the waveform diagram 28 is initially present at the time t0b an actual setpoint difference, which without delay with a switching operation (switching signal 34 at time t0b) for the actuating means 11 is answered. This is due to the fact that the control unit 4 is exemplarily designed such that it is at actual pressure values outside of the threshold values 32 . 33 limited threshold interval immediately a control of the respective actuating means 11 . 12 makes, in the present case so the actuating means 11 with the switching signal 34 to cause an increase in pressure. At time t1b, the actual pressure value reaches the lower threshold value 32 , resulting in the control unit 4 a timer not shown in detail is activated, which specifies a waiting time tw. During this first wait tw be from the control unit 4 Although changes in the actual setpoint difference continue to be considered, however, no change in the provision of electrical power takes place, regardless of the setpoint-actual value difference that occurs during the waiting time tw Energy to the two actuating means 11 . 12 instead of. If, during the waiting time tw, there is both a leakage of the actual pressure value 30 from the threshold interval as well as reentry of the actual pressure value 30 come into the threshold interval, as in the 3 by way of example at the time t2b or t3b is present, so at the time of reentry of the actual pressure value in the setpoint interval, in this case at the time t3b, a restart of the waiting time tw. The second waiting time tw extends in the 3 from time t3b to time t4b. Since during the second waiting time tw, ie between t3b and t4b, the actual pressure value 30 has left the setpoint interval, but at the end of the waiting time tw, ie at the time t4b has not reentered the threshold interval, there is no restart of the waiting time tw. Rather, the waiting time tw runs off completely, which is why it is shown in cross-hatching. At time t4b, due to the deviation of the actual pressure value 30 from the setpoint interval a control of the actuating means 11 to increase the pressure in the valve chamber 14 to effect and the actual pressure value 30 back into the setpoint interval.

The control signal 34 ends at the time t5b with the occurrence of the actual pressure value 30 in the threshold interval. At the same time, at the time t5b, the waiting time tw is started again, in the present case for the third time. Because the actual pressure value 30 Although the setpoint interval leaves at the time t6b during the third waiting time tw, but again enters the setpoint interval at the time t7b before the third waiting time has elapsed, the wait time tw is restarted at the time t7b for the fourth time. The fourth waiting time tw extends from the time t7b to the time t8b and, because it is a complete expiration of the waiting time tw, is shown in crosshatching. Since there is a setpoint-actual value difference at time t8b, the amount of which is smaller than the difference between the upper threshold value 33 and the lower threshold 32 is, no further adjustment of the actual pressure value 30 needed and the two adjusting means 11 . 12 remain in the respective position.

Accordingly, due to the respective waiting time tw, an inclination of the fluidic system for swinging up is markedly reduced, so that with a similar reaction speed a reduced number of switching cycles for the actuating means 11 . 12 per unit time and thus a reduced noise level for the fluid control valve 5 can be guaranteed.

In an embodiment of the invention which is not shown, provision is made for the waiting time to be selected as a function of a previously determined maximum setpoint / actual value difference such that the waiting time is selected shorter for a large setpoint / actual value difference than for a small setpoint / actual value. Difference.

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 19516627 A1 [0003]

Claims (8)

Method for controlling an electrically operable actuating means ( 11 . 12 ) for a fluid control valve ( 5 ), wherein the actuating means ( 11 . 12 ) with a valve body ( 16 . 17 ) coupled in a valve space ( 14 ) of the fluid control valve ( 5 ) for influencing a fluidic cross-section between an input terminal ( 6 . 8th ) of the fluid control valve ( 5 ) and a work connection ( 7 ) of the fluid control valve ( 5 ) relative to a valve seat ( 18 . 19 ) of the fluid control valve ( 5 ) is movably arranged to receive a fluid flow from a fluid source ( 9 ) through the fluid control valve ( 5 ) to a fluid consumer ( 3 ) and a fluid effluent from the fluid consumer ( 3 ) through the fluid control valve ( 5 ) in a fluid sink, with the steps: determining a to the fluid consumer ( 3 ) provided actual pressure value, in particular in the valve chamber ( 14 ), Comparing the actual pressure value with a predefinable desired pressure value and determining a nominal value-actual value difference and changing a provision of electrical energy to the actuating means ( 11 . 12 ) at a first activation time, when the setpoint-actual value difference reaches a first predefinable threshold value ( 33 ) or a second predefinable threshold ( 32 ), characterized in that the change in the provision of electrical energy is terminated when the setpoint-actual value difference in a threshold interval between the first and the second threshold ( 32 . 33 ) occurs and that at the time of entry of the setpoint-actual value difference in the threshold interval followed by a predetermined waiting time (TW), during which there is no change in the provision of electrical energy. A method according to claim 1, characterized in that during the waiting time (tw) a determination of the desired-actual value difference is made and that after a leakage of the setpoint-actual value difference from the threshold interval and a subsequent reentry of the setpoint actual value difference in the threshold interval during the waiting time a restart of the waiting time takes place. A method according to claim 1 or 2, characterized in that a change amount for the provision of electrical energy is selected independently of the activation time or in dependence on the setpoint-actual value difference. A method according to claim 1, 2 or 3, characterized in that the change in the provision of electrical energy takes place as providing or switching off a predeterminable electrical supply voltage. Method according to one of claims 1 to 4, characterized in that the waiting time (tw) is given by a, preferably adjustable, timer. Valve device with a control unit ( 4 ) for providing control signals to a fluid control valve ( 5 ) and with a fluid control valve ( 5 ), which is an electrically operable actuating means ( 11 . 12 ), which is connected to a valve body ( 16 . 17 ) coupled in a valve space ( 14 ) of the fluid control valve ( 5 ) for influencing a fluidic cross-section between an input terminal ( 6 . 8th ) and a work connection ( 7 ) relative to a valve seat ( 18 . 19 ) is movably arranged to receive a fluid flow from a fluid source ( 9 ) to a fluid consumer ( 9 ) and a fluid effluent from the fluid consumer ( 9 ) in a fluid sink, characterized in that the control unit ( 4 ) is designed for carrying out a method according to one of the preceding claims. Valve device according to claim 6, characterized in that the actuating means ( 11 . 12 ) is designed as a piezoelectric actuator. Valve device according to claim 6 or 7, characterized in that in the valve chamber ( 14 ) with the control unit ( 4 ) electrically coupled pressure sensor ( 15 ) arranged to provide the actual pressure value.

Images