EP2000875B1 - Method for automatic calibration of a control unit for an adjustable fluid infeed - Google Patents

Abstract

The method involves coupling of throttle device with an actuator. A position signal of a position detection system is detected by a control device. The position signal is stored as an end position signal in the control device, if the position signal in a time period is changed around less than other minimum value. A control characteristic value is computed from end-reference values and the end position signals in the control device and storage of characteristic line. An independent claim is also included for an automatic calibration control device for controlled fluid supply for a gas burner.

Description

The invention relates to the calibration of actuators or actuators for controllable fluid supply. In particular, the invention relates to actuating devices with actuators, which adjust a mechanical throttle device in the fluid supply of a gas consumption device.

In the field of gas use, especially in gas burners, the fluid supply is adjusted depending on the required operating parameters and performance requirements. For this purpose, a volume flow change of the respective fluid is made with actuators in gas or air lines and using coupled actuators or throttle devices.

From the WO 99/50580 a valve with control system for flow control is known, which balances the position signals of a control system with calibration data during operation.

The US 4506642 describes a positioning system from another area of technology. With an electronic accelerator, an actual range of the pedal is adjusted with a predetermined range.

An actuator is controlled with a setpoint signal, for example, a current signal, which is in a predetermined setpoint signal range (eg 4-20mA). The actuator moves the actuator or the throttle device according to the predetermined setpoint signal. Since actuators for a variety of different applications should be used, the setpoint signal ranges are regularly fixed - the actuator is the correct implementation of the setpoint signal in an actual control value of the throttle device left. When frequently used in the gas use throttle as throttle devices, for example, regularly rotational angle of 0 ° to 90 ° can be approached to achieve the change in volume flow. The setpoint specifications are to be transferred to this rotation angle range. at Delivery of a setting device this is already regularly pre-calibrated to a setting range.

Throttle end positions are limited to limit switches operated by shift cams mounted on the drive shaft, in accordance with generally accepted standards. This measure interrupts the power supply to the drive motor as soon as a corresponding end position is reached. In particular, the switches fulfill a safety function, since a reliable start-up of the end positions must be ensured, for example during pre-rinsing of the burner.

Depending on the actual application, however, an individual setting range of the actuator deviating from the delivery state is required in a fluid supply. For example, a smaller range of rotation angles may be desired for a throttle. The cams which actuate the limit switches are set to the required setting range during commissioning by an installer.

However, in order to ensure the mentioned wide compatibility, the actuator continues to be supplied with reference value signals in the predetermined reference signal range. However, in order to transfer the specified setpoint signal range to the changed setting range of the actuator in the respective application, a calibration of the actuator is required. During calibration, the specified ranges (setpoint signal and setting range) are related by a characteristic curve (often a characteristic curve). In the case of a correspondingly calibrated actuator, the entire setting range can then be approached using the full width of the setpoint signal. It is desirable that the setpoint signal range is mapped to the entire range, which is limited by the limit switches.

Since the new end positions of the setting range are determined by the limit switches or switching cams, the characteristic must be calibrated.

This is done in the prior art either by manual adjustment of potentiometers, the zero point and slope of the characteristic curve or characteristic curves or both endpoints of the characteristic curve or by manually programming the characteristic endpoints.

The setting by means of a potentiometer is iterative, because after each change it must be checked whether the end positions were made with the potentiometer setting. In the so-called manual programming, the drive is manually moved to the open or closed position and manually triggered a memory function in the respective positions. The control system can then calculate a characteristic from the predetermined values.

There is therefore the problem that recalibration of the actuator requires user intervention in multiple actuator positions.

The object of the invention is to simplify the calibration of an actuator for a variety of possible applications and to reduce the susceptibility to errors.

This object is achieved by a method according to claim 1 and a corresponding device according to claim 10.

According to the invention, an actuator has a control device which controls a program-controlled device, e.g. having a microcontroller. The actuator also has an actuator coupled to the controller. A mechanical throttle device is coupled to the actuator and adjustable by this in a control range between two end positions.

The control device can be controlled by specifying setpoint signals in a predetermined setpoint signal range. The types of signals can be arbitrary, in particular current signals or digital signals can be used.

The actual actuator forms part of the adjusting device and is formed from the control device with associated microcontroller and the actuator, wherein the actuator also has a drive.

If the calibration method according to the invention is started (initiated), the control device controls under control of a in the microcontroller running program the entire calibration process.

The controller controls the actuator to move the throttle device in a first direction. During activation for movement, repeated detection of the position of the actuator by the control device takes place. In this case, a position signal of a position detection system associated with the actuator is detected by the control device in order to determine a standstill of the actuator. This standstill will be present when a limit switch limits the end of the control range and interrupts the motor current.

If the position signal changes by less than a first minimum value in a first time period, the control device detects a standstill of the actuator. The position signal is then stored as the first end position signal in the control device.

Subsequently, the actuator is actuated by the control device in order to move the throttle device in a second direction. Again, the position of the actuator is detected repeatedly by the control device, the position signal of the position detection system being detected by the control device. If the position signal changes by less than a second minimum value in a second period of time, the control device determines the standstill of the actuator and thus the reaching of the second end position and stores the position signal as a second end position signal in the control device.

The control device now has two end position signals as well as the known limitations of the setpoint signal range. From the final setpoint values and the final position signals, a control characteristic or a functional relationship is calculated and stored in the control device.

On the basis of the characteristic thus determined, the entire predefined setpoint signal range can be used for the control and is optimally transmitted in the control device to the setting range determined during the calibration. It is not a complex user intervention for the calibration required and the process runs quickly, with little effort and with low error rate.

A particular advantage of the invention is that the signals of an already existing position sensor are evaluated. Additional monitoring of signals (e.g., the limit switches) to detect reaching the end positions is not required. As an essential aspect according to the invention, therefore, the temporal evaluation of the position information is used to detect the achievement of the end positions and the resulting standstill of the actuator.

The determination of the standstill of the actuator takes place when a minimum change in position in a time interval is not detected. However, on the basis of this finding, a further check of the standstill (for example renewed detection of the change in position after elapse of a further period of time) can take place.

In a preferred embodiment of the invention, the control device monitors during the movement of the throttle device in the first and the second direction exceeding an allowable maximum duration, and aborts the method and generates an error message when the allowable maximum duration is exceeded.

In this development, a time limit for performing the calibration is monitored. As far as e.g. If, for some reason, the adjusting movement does not come to a standstill (for example due to faulty coupling of the actuator with the actuator or faulty limit switches), the process is terminated. The termination can be displayed to a user visually or acoustically.

In a preferred embodiment, when the control unit detects at the start of the calibration process that the position signal changes by less than a predetermined third minimum value in a predetermined third time period, the initial direction of movement of the actuator is reversed.

By continuous or periodic detection of the position data is a standstill of the actuator or an irregular or defective movement detected quickly. However, it happens that the calibration is started in a state of the actuator in which an end position has already been reached. A movement control in the direction of this end position then has no movement of the actuator result, although there is no error. The method is then restarted by the controller, with the initial direction of travel reversed.

The detected end position signals are preferably subjected to a plausibility check in the control device. It is checked whether the end position signals are within a predetermined range of values. A plausibility check will provide further assurance of proper installation and calibration. Faulty cam positions and limit switches can be detected in this way.

The invention will now be explained in more detail with reference to the accompanying drawings.

FIG. 1 shows a diagram showing the representation of a characteristic change by the calibration method.

FIG. 2a shows a flowchart of a first subsection of the calibration method according to the invention.

FIG. 2b shows a flowchart of a second section of the calibration method according to the invention.

FIG. 3 shows a schematic diagram of a control device according to the invention.

In the present embodiment, the actuator is used for volume flow change in an air line of a gas burner. In the air line, a throttle valve is used, which can limit the passage of air variable. The actuator has a control device with a microcontroller. With the control device, an actuator is coupled, which has an associated drive. The controller controls the actuator which is coupled to the throttle and thus changes the angular position of the throttle in the air line.

When commissioning the device, the control cam mounted on the drive shaft are adjusted. The switching buttons limit the adjustment range of the throttle. The cams actuate when reaching an end position of a micro-switch, which defines an end position of the throttle.

In the given embodiment, the control cams are set on the drive shaft in such a way that the adjustment range of the throttle valve is limited to rotational angles of 20 ° and 80 ° (0 ° corresponds to a throttle position transverse to the direction of flow, ie a closed position and 90 ° corresponds to one Position parallel to the flow direction, ie an open position).

The controller accepts set point signals in the range of 4 to 20 mA, according to a predetermined standard. This setpoint signal range should be able to be used for control over the entire setting range defined by the cam position.

As in FIG. 1 shown, the control current or the setpoint signal is entered on the abscissa of the diagram. The corresponding rotation angle is shown on the coordinate.

In the delivery state of the actuator this is pre-calibrated and accordingly a control current of 4 mA with a rotation angle of 0 ° and a control current of 20 mA with a rotation angle of 90 ° are related. The corresponding characteristic curve 1 shows the functional relationship between setpoint specification and angle of rotation.

After the actuator has been adapted to the respective application during commissioning, the cams mounted on the drive shaft are set in such a way that the limit switches are approached in positions 2 and 3, ie at 20 ° and 80 °. It can be seen that the setpoint range between 4 and 8 mA as well as between 18 and 20 mA has no corresponding accessible adjustment ranges of the rotation angle.

In the case of an appropriately performed calibration, the characteristic curve 1 is converted into a characteristic curve 4, wherein the entire setpoint range of 4 to 20 mA covers the control range of 20 ° to 80 ° limited by the switching cams. To establish such a linear relationship, it is sufficient to define two value pairs.

The automated method according to the invention converts the actuator from the original or delivery state into a calibrated state, wherein the corresponding characteristic curve 4 is stored in the control device.

In FIG. 2A a first section of an embodiment of the calibration method according to the invention is shown. Starting from a manual, time-controlled or event-controlled start 100, the control device, which has a microcontroller which executes a corresponding program, controls the actuator for movement in the direction of the open position. The actuator moves at 110 in the direction of the open position and thereby rotates the coupled to the actuator throttle in the direction of increasing rotation angle. This movement maintains the controller for a predetermined period of time of X seconds, with the period being regularly between 0.5 and 5 seconds. The controller monitors at 120 based on the signals of a position detection, which is formed from a coupled to the drive shaft potentiometer, whether the angular position of the throttle changes. If not, proceed to step 135, which is explained below. However, if movement is detectable, at 130 the actuator continues to move the throttle under control of the controller toward the open position. During the procedure, a timeout is checked. If a predetermined acceptable period of time for reaching the open position is exceeded, an abort of the calibration process is initiated at 140 with the output of a corresponding error message. At 150, it is checked whether the drive is still in motion, ie whether the position information of the position detection system change over time. If so, it returns to step 130. If the drive is no longer moving, the position of the actuator is temporarily stored at 170 as the new maximum position for the open position.

This in FIG. 2A at position A ending diagram is in FIG. 2B continued at A. After the new maximum position has been latched, the controller drives the actuator at 180 to move the throttle closer Angle of rotation, ie to adjust in the direction of the closed position. Again, in steps 190 and 200, the maximum total time allowed is monitored and motion of the actuator is monitored. Once the standstill of the actuator is reached, the position is cached at 220 as a new minimum position. In step 230, the control device checks whether plausible data for the minimum and maximum position are available, in particular whether they are within a permissible setting range.

In the case of a positive check, the minimum and maximum positions are stored in step 240 and the characteristic curve 4 is calculated. The control device has the data which minimum position is to be approached with a nominal value of 4 mA, which corresponds to a position of the throttle valve of 20 °. In addition, it has the information that at a setpoint of 20 mA, the maximum position is to be approached, which corresponds to an angle of rotation of 80 ° of the throttle valve.

If the method is started when the throttle is already in the open position, it is detected at step 120 that the actuator is not moving. In this case, the method is executed in steps 135, 145, 155, 175 such that first the new minimum position which corresponds to the closed position is determined and in steps 185, 195, 205, 225 a new maximum position is determined and is stored. This ensures that proper calibration can be performed from any throttle position.

It can be provided that the calibration is carried out again after successful execution in order to check the reproducibility of the calibration data. The calibration can be time-controlled or user-triggered as often as desired. During the calibration process, the actuator for external signals can be completely disabled so as not to affect the calibration. User control of the calibration process is not required, but data output can be made to allow a user to verify. Based on this data, faulty cam positions can be detected automatically, for example if the cam position is outside the possible working range.

FIG. 4 shows a schematic circuit diagram of a setting device according to the invention.

The control device 300 has a microcontroller. The program for carrying out the method according to the invention is stored in the memory of the microcontroller. Coupled to the controller 300 is an operator interface 305 having display means and a start switch for initiating the calibration procedure. A contact strip 310 coupled to the control device has terminals for the actual value and desired value signals. The set point signals may be provided to the controller 300 in various predetermined set point signal ranges, e.g. as current signals in the range of 4-20 mA (other signal ranges are selectable).

Coupled to the control device is the position detection system 315, which has a potentiometer and supplies position signals of a drive shaft to the control device 300. The position detection system is disposed on the actuator 320, and converts its rotational position in the relayed position signal.

A contact strip 325 has various connections of the group L1. The terminals L1-on and L1-to serve the operation of the actuator and the throttle device, bypassing the control device. The L1 enable terminal provides the operating voltage for the operation of the actuator under the control of the controller. If a corresponding voltage is present at L1 enable, a corresponding signal is applied to the control device via line 330 (after suitable conversion).

The controller then actuates the switches 335 by applying a signal on line 340, thereby excluding activation of the actuator via L1-to and L1-on.

In this state, the controller 300 can take over the control of the actuator via the signal lines 345 and 350 and perform the calibration process.

The limit switches S3 and S4 interrupt when performing the method when reaching the end positions of the throttle valve, the power supply of the actuator 320 via circuit one of the switch 355. The control for a continued movement in this direction is then inhibited and the end positions are defined. The control device 300 detects the standstill of the actuator via the signal of the device 315 and performs the movement of the actuator in the other direction, in which case the other of the switch 355 is actuated in the opposite end position.

It should be noted that the controller exclusively utilizes the location information of the device 315 to perform the calibration. A connection of the switch 355 with the controller 300 does not exist.

In the context of the invention various modifications are possible. For example, it is possible to use arbitrarily complex functional relationships in the determination of the characteristic, a linear relationship is not necessarily required.

Claims (10)

1. A method of automatically calibrating a control device of a controllable fluid infeed for a gas consuming device, wherein the control device has an actuator, a controller coupled to the actuator and a mechanical throttle device, which is coupled to the actuator and is movable within a control region between two end positions, wherein the controller is controllable by means of a predetermined range of values of desired control values, which lie between two end desired values,
   including the steps of:

   initiating the automatic calibration process, whereby the controller performs the following steps in a program-controlled manner in reaction to the initiation:

   controlling the actuator by the controller in order to move the throttle device in a first direction,

   repeated detection of the position of the actuator by the controller, whereby a position signal of a position detecting system associated with the actuator is detected by the controller in order to monitor movement or stoppage of the actuator,

   when the position signal alters by less than a first minimum value in a first period of time, storing the position signal as a first end position signal in the controller,

   controlling the actuator by the controller in order to move the throttle device in a second direction,

   repeated detection of the position of the actuator by the controller, whereby the position signal of the position detection system is detected by the controller,

   when the position signal alters by less than a second minimum value in a second period of time, storing the position signal as a second end position signal in the controller,

   calculating a control curve from the predetermined desired end values and the stored end position signals in the controller and storing the curve.
2. A method as claimed in Claim 1, wherein during the movement of the throttle device in the first and second directions, the controller monitors when a permissible maximum duration is exceeded and, when the permissible maximum duration is exceeded, interrupts the method and generates an error signal.
3. A method as claimed in Claim 1 or 2, wherein when the controller system detects at the start of the calibration process that the position signal alters by less than a predetermined third minimum value in a predetermined third period of time, the controller reverses the initial direction of movement of the actuator.
4. A method as claimed in one of Claims 1 to 3, wherein the end position signals are subjected in the controller to a plausibility check wherein it is checked whether the end position signals lie in a predetermined value range.
5. A method as claimed in one of Claims 1 to 4, wherein the controller performs the calibration process at least twice and, in the event of deviation of the results above a predetermined difference, generates an error signal.
6. A method as claimed in one of Claims 1 to 5, wherein the controller produces optical indications relating to the current performance of the calibration, the successful conclusion of the calibration and an interruption of the calibration.
7. A method as claimed in one of Claims 1 to 6, wherein a signal from a potentiometer, constituting a position signal, is analysed.
8. A method as claimed in one of Claims 1 to 6, wherein a signal from an incremental sensor, constituting a position signal, is analysed.
9. A method as claimed in one of Claims 1 to 8, wherein a throttle flap, a valve or a slide plate is used as the throttle device.
10. A self calibrating control device for a controllable fluid infeed for a gas burner, wherein the control device has
    an actuator, which has a controllable drive,
    a controller, which is coupled to the actuator and which has a microcontroller, wherein the microcontroller includes storage means, which stores the instructions for performing the calibration method as claimed in one of Claims 1 to 9.

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