EP3811161A1

EP3811161A1 - Adaptive two-position controller and method for adaptive two-position control

Info

Publication number: EP3811161A1
Application number: EP19730323.3A
Authority: EP
Inventors: Sebastian Leonow; Martin Mönnigmann
Original assignee: Ruhr Universitaet Bochum
Current assignee: Ruhr Universitaet Bochum
Priority date: 2018-06-25
Filing date: 2019-06-11
Publication date: 2021-04-28
Also published as: DE102018004989B3; WO2020001974A1; US20210247725A1; US11733658B2

Abstract

The invention relates to a method for the two-position control of an actuator (1) on the basis of a binary sensor signal (y) of a sensor unit (2), which senses a process variable (P), which can be influenced by the actuator (1), in such a way that the sensor unit outputs a first sensor signal value (y1) when a first switching value (Sw1) is exceeded and a second sensor signal value (y0) when a second switching value (Sw1, Sw2) is fallen below, wherein: the actuator (1) is controlled with a manipulated variable (u), which assumes either a first control value (u1) or a second control value (u2); the first control value (u1) and the second control value (u2) are dynamically adapted during the operation of the actuator (1), in dependence on a fall time (t_fall) corresponding to the duration of the first sensor signal value (y1) and a rise time (t_rise) corresponding to the duration of the second sensor signal value (y0), in such a way that the first and second control values converge. The invention further relates to a two-position controller (10) designed to carry out the method and to an actuator (1) comprising said two-position controller (10).

Description

Adaptive two-point controller and method for adaptive two-point control

The invention relates to a method for two-point control of an actuator, based on a binary sensor signal from a sensor unit that detects a process variable that can be influenced by the actuator such that it outputs a first sensor signal value when a first switching value is exceeded and a second sensor signal value when the value falls below a second switching value Actuator is controlled with a manipulated variable that either accepts a first manipulated variable or a second manipulated variable. In addition, the invention relates to a two-point controller for controlling an actuator based on a binary sensor signal, having an input for a binary sensor signal and an output for a manipulated variable for controlling an actuator. Furthermore, the invention relates to an actuator which has the two-point controller according to the invention.

Two-point controllers are discontinuous controllers that operate

Control the actuator with two manipulated values, whereby an upper or a lower manipulated value is output, depending on whether the actual value is above or below the setpoint. A binary output signal with two manipulated variable values is thus output on the basis of a binary sensor signal from a sensor unit that detects a process variable. Two-point controllers are usually used when the manipulated variable is not continuously variable, but only between two states (e.g.

on / off) and / or if the sensor unit is not a constant one

Process variable outputs the corresponding signal, but provides a binary sensor signal.

With a two-point controller, a control loop for controlling a

Realize the process variable, for example a fill level or a temperature, with an inexpensive sensor unit that delivers a binary output signal, for example with a float switch or a bimetal switch. For example, a pump in a wastewater pumping station can be operated using a Operate two-point controller, in which the pump is only switched on or off cyclically as required, whereby an activation or deactivation in

Dependence of the level in a pump sump is controlled by a float switch. However, frequent on-off changes lead to increased wear and energy consumption.

Actuators whose manipulated variable can be continuously adjusted, i.e. where the manipulated variable can be controlled with intermediate values between the on and off states, make it possible to adapt the manipulated variable value to the requirements. For example, in pump units that have a frequency converter for speed control, the speed can be regulated as a manipulated variable value, thus preventing repeated repetitive switching on and off. According to DE 10 2013 007 026 A1, a fill level sensor is required for the need-based control of the speed, which continuously determines the level and sets an energy-optimized speed based on the level. The disadvantage is that a level sensor is required, which is more maintenance-intensive and more expensive than a sensor unit that emits a binary signal.

The object of the invention is based on a simple, robust and

To provide cost-effective sensor unit a method for controlling an actuator, which operates the actuator in an energy-efficient and low-wear manner. It is also an object of the invention to provide a controller which, based on a simple, robust and inexpensive sensor unit, enables an actuator to be controlled in an energy-efficient and low-wear manner. Furthermore, it is an object of the underlying invention an actuator for

To make available that can be operated in an energy-efficient and low-wear manner by means of the controller according to the invention.

The underlying object is achieved by a method which has the features of claim 1, advantageous embodiments being set out in the dependent claims 2 to 14. A controller solving the underlying task has the features of claim 15. An actuator according to the invention has the features of claim 16. The underlying process is characterized in that the first

The actuating value of the actuator and the second actuating value of the actuator as a function of a fall time, which corresponds to the duration of the first sensor signal value, and a rise time, which corresponds to the duration of the second sensor signal value, can be dynamically adjusted during operation of the actuator such that they converge with one another.

In a method that has the features from the preamble, the manipulated variable of the actuator is set to the first manipulated value or the second manipulated value depending on the sensor signal value. For example, a heating device that heats a container or room and represents an actuator in the sense of the invention is switched off when a certain process variable value or one

Temperature is reached and the first sensor signal value is present. A drop in the temperature in the container or room leads to the temperature falling below a second switching value, so that the sensor outputs a second sensor signal value and the heating device for heating the container or room is switched on. After the temperature has been exceeded, the heating device turns on again

switched off. As a result, the heater is alternately turned on and off with the temperature fluctuating between the switching values. The setting of the first switching value and the subsequent second switching value is referred to below as a cycle.

The first signal value is present in the period between exceeding the first switching value and falling below the second switching value. During this period, the actuator is actuated with a manipulated variable that leads to the

Process variable falls, accordingly the duration of the first signal value is called the fall time. The second signal value lies between

Falling below the second switching value and exceeding the first switching value. During this period, the actuator is actuated with a manipulated value that leads to an increase in the process variable. Accordingly, the duration of the second signal value is referred to as the rise time.

For example, the heating device, which heats a container or room and at which the temperature is the process variable, is driven with a lower heating power which is so low that the temperature in the container drops when the first switching value has been exceeded and the first sensor signal value is present. The heating device is operated with the lower heating power until the temperature falls below the second switching value and the sensor unit supplies the second sensor signal. As soon as the second sensor signal is present, the heating device is controlled so that it is operated with an upper heating power that is so high that the temperature in the

Container or room rises. The actuator is activated with the signal for the upper heating power as long as the second sensor signal is present. The fall time and the rise time are determined from the duration of the sensor signals.

The manipulated values are dynamically adjusted based on the rise and fall times. Dynamic adaptation in the sense of the invention is to be understood as a recalculation of the first manipulated variable and the second manipulated variable for each subsequent cycle.

The method according to the invention provides for the first manipulated variable and the second manipulated variable to be dynamically adapted, specifically in such a way that the two values converge with one another. With each new cycle, the actuator is controlled with a manipulated variable in which the difference between the first and second manipulated variable is smaller than in the previous cycle. With decreasing amplitude of the manipulated variable change, the switching losses and the wear of the

Actuator. Incidentally, the switching frequency also decreases because the difference between the first and second manipulated variable is getting smaller and the process variable changes more slowly. The decrease in the switching frequency also leads to a reduction in wear and energy consumption.

For example, in a heating device which is provided for heating a container or room, the difference from lower to upper heating power in a heating device operated with the method becomes smaller and smaller from cycle to cycle, so that the amplitude of the manipulated variable change decreases successively.

The switching frequency also decreases because the temperature of the container or

Room changes more slowly with decreasing amplitude of the manipulated variable change. In this way, wear and switching losses are reduced, among other things. The first manipulated variable and the second manipulated variable are preferably adapted dynamically such that the fall time and the rise time successively assume the same value. The first and the second manipulated value are adjusted accordingly after each cycle so that the fall time and the rise time approach each other. For example, to increase the waste time compared to

Rise time of the first manipulated variable is increased less than the second manipulated variable is reduced, so that the process variable changes more slowly when falling. By aligning the fall time with the rise time, it is achieved that the first and the second

Vary the manipulated value symmetrically by one value. This value represents a

Control loop, in which the process variable constantly changes from outside, represents the optimal operating point. In the example of the heating device that heats a container or room, this means that the value at one

constant heat loss represents the optimal operating point.

Advantageously, a symmetrical switching of the actuator around an optimal operating point is thus achieved, which permits low-wear and efficient operation of the actuator.

An embodiment of the invention is characterized in that the method repeatedly comprises the following steps:

- A first step in which the actuator is controlled with the first manipulated variable, which is the difference between a manipulated variable mean and one

Corresponding manipulated variable amplitude, and the fall time is determined when the

Sensor unit outputs the first sensor signal value,

a second step, in which the actuator is activated with the second manipulated value, which corresponds to the sum of the manipulated variable mean value and the manipulated variable amplitude, and the rise time is determined when the sensor unit outputs the second sensor signal value, and

- A third step, in which a new manipulated variable is determined from the fall time and the rise time.

In this embodiment of the invention, the first manipulated variable and the second manipulated variable are based on a manipulated variable mean and a

Command value amplitude set. In the event that the sensor unit outputs the first sensor signal value, the actuator is activated with the first control value, this being the difference between the manipulated variable mean and the

Corresponding manipulated variable amplitude. In the case of a control loop in which the process variable reacts positively to a change in the manipulated variable, such control of the actuator leads to the process variable falling. In this case, the duration of the first sensor signal value corresponds to the fall time. As soon as the second

Sensor signal value is present, that is, the process variable has fallen below the second switching value, the second step is carried out, the actuator being actuated with the second manipulated value, which corresponds to the sum of the manipulated variable mean value and the manipulated variable amplitude. This means that the process size increases when the second step is carried out. Until the first one

Switching value is exceeded, which leads to the sensor unit outputting the first sensor signal value. The duration of the second sensor signal value corresponds to the rise time. In the third step, on the basis of the determined fall time and rise time, a new manipulated variable mean value is determined, on the basis of which the first manipulated value and the second manipulated value are recalculated when the first and second steps are repeated. The repeated execution of the first, the second and the third step achieves a targeted regulation of the manipulated variable around the manipulated variable mean value, the manipulated variable fluctuating around the manipulated variable mean value with the manipulated variable amplitude. The

The mean value of the manipulated variable and the manipulated variable amplitude are advantageously determined on the basis of measured values; the determination of these quantities then does not require user intervention.

In the case of a heating device that heats a container or room, this means, for example, that the heating device is activated in the first step with a signal for a heating power that corresponds to the difference between an average heating power and an amplitude, the temperature inside the tank or

Due to the reduced heating output. After falling below the second switching value, the sensor unit outputs the second sensor signal value and the second step is carried out, the heating device having an upper one

Heating power is controlled, which corresponds to the sum of an average heating power and the amplitude. As a result, the temperature in the container or room rises. As soon as the first switching value is exceeded, the sensor unit outputs the first sensor signal value, the duration of this value being the rise time equivalent. In the third step, based on the fall time and the rise time, a new average heating output is calculated as the manipulated variable mean value, which is used when the first and second steps are carried out again. The

The heating power of the heating device thus fluctuates with the amplitude around the average heating power.

An alternative embodiment of the invention provides that the method repeatedly comprises the following steps:

Corresponds to the manipulated variable amplitude, and in which the rise time is determined when the sensor unit outputs the second sensor signal value,

a second step, in which the actuator is activated with the second manipulated variable, which corresponds to the sum of the manipulated variable mean value and the manipulated variable amplitude, and in which the fall time is determined when the sensor unit outputs the first sensor signal value, and

This variant affects control loops in which the process variable reacts negatively to an increase in the manipulated variable. For example, an increase in the speed of a pump that is intended to empty a container leads to an increase in the outflow and thus a drop in the level, that is to say the process variable reacts negatively. In this case, the actuator is actuated with a first manipulated variable, which is the difference between the manipulated variable mean and

The manipulated variable amplitude corresponds to the fact that the process variable increases. The process variable is increased when the sensor unit receives the second

Outputs sensor signal value, i.e. as soon as the second switching value is undershot until the first switching value is exceeded. As soon as the first switching value is exceeded, the sensor unit outputs the first sensor signal value and the second step is carried out, in which the actuator is controlled with the second manipulated value, which corresponds to the sum of the manipulated variable mean value and the manipulated variable amplitude. This causes the process variable to drop, the fall time being determined as the duration of the first sensor signal value. The third step is based on the Fall time and the rise time a new manipulated variable mean is calculated, which in turn is used when the first and second steps are carried out again. In the example of the pump emptying a container, this would mean that the pump is controlled in the first step at a lower speed, that is the difference between an average speed and a

Speed amplitude corresponds and is controlled in the second step with an upper speed, the sum of an average speed and one

Speed amplitude corresponds. The outflow from the container is thus regulated so that the level fluctuates back and forth between the first switching value and the second switching value.

The method preferably has a fourth step in which the manipulated variable amplitude is reduced.

Reducing the manipulated variable amplitude means that the first manipulated variable and the second manipulated variable are adjusted so that they converge with one another. As a result, the level of the switching steps to be performed by the actuator decreases, so that the actuator is operated with little wear and energy efficiency. For example, the speed amplitude is reduced in a pump, so that switching losses are reduced when switching between the lower and the upper speed.

A preferred embodiment of the method provides that the fourth

Method step is carried out repeatedly until a non-zero minimum manipulated variable amplitude is reached.

A repeated reduction in the manipulated variable amplitude leads to the first manipulated variable converging to the second manipulated variable. In the method according to the invention, it is important to determine the fall time and the rise time in order to adapt the first and the second manipulated value on the basis thereof, so that an albeit minimal fluctuation in the process variable is desired. For that it will

Actuator controlled at least with a manipulated variable, in which the manipulated variable fluctuates with a minimum manipulated variable amplitude around a manipulated variable mean. Such operation is particularly necessary to avoid any disruption to the Determine control loop that lead to an increase or a reduction in the rise or fall time. Preferably the minimum

The manipulated variable amplitude is selected so that the energy losses and

Sign of wear on the actuator is as minimal as possible.

One embodiment of the method according to the invention provides that the fall time and the rise time are compared with one another,

- The new manipulated variable mean being increased if the rise time is greater than the fall time, or

- The new manipulated variable mean is reduced if the rise time is less than the fall time.

By comparing the fall time with the rise time, it can be determined whether the manipulated variable mean value is the optimal operating point for a control loop in which the process variable constantly changes from outside. On

The difference between the fall time and the rise time indicates that a new correction of the manipulated variable mean value is necessary. The manipulated variable value must be increased if the rise time is greater than the fall time. A reduction of the manipulated variable mean value is necessary if the rise time is less than the fall time. This is a constant adaptation of the

Average control value achieved by changing the process variable.

An embodiment of the invention provides that the new manipulated variable mean value according to u_mean = u_mean + k * delta

is determined, where k is a correction factor that depends on the fall time and the

Rise time depends. The correction factor preferably depends on the ratio between the fall time and the rise time.

A correction factor, which depends on the fall time and the rise time, is added to the manipulated variable mean value in order to adapt the manipulated variable mean value to changes in the process variable. The factor depends in particular on the relationship between the rise time and the fall time, so that an adjustment between the rise time and the fall time is achieved if the mean value of the manipulated variable is corrected several times. The correction factor is multiplied by the manipulated variable amplitude, which leads to the fact that the correction with reduction of the manipulated variable amplitude becomes smaller and smaller from cycle to cycle and that the manipulated variable mean value approaches an optimal value. An approximation takes place in particular when an externally induced change in the process variable is constant, for example when the outflow quantity for a container to be filled is constant over time.

The correction factor in the method according to the invention is preferably k = 1 - t_fall / t_rise

determined if the rise time is greater than the fall time, and after

k = t_rise / t_fall - 1

determined if the rise time is less than the fall time.

In this way, the new manipulated variable mean is increased when the

Rise time is greater than the fall time, and decreases when the rise time is less than the fall time, depending on the relationship between the rise time and the fall time. If the rise time and fall time are identical, k = 0, so that the new manipulated variable mean value is not corrected.

An alternative embodiment variant of the method provides that the

correction factor

k = 1 - sqrt (t_fall / t_rise)

is when the rise time is greater than the fall time, and the correction factor

k = sqrt (t_rise / t_fall) - 1

is when the rise time is less than the fall time.

Forming the root of the ratio between the rise time and the fall time has the advantage that the correction takes place smoothly, or the change in the new manipulated variable mean is smaller than when the ratio between the rise time and fall time is used purely.

In a preferred embodiment of the method, a start step is first carried out in which the actuator is controlled with a manipulated variable which leads to the first switching value being exceeded or the second switching value being exceeded

is undercut. The start step is used to bring the control loop into a state in which the first four process steps are carried out repeatedly and the

Process variable alternates between the first switching value and the second switching value. In a control loop in which the process variable depends positively on the manipulated variable and is below the switching values, a manipulated variable is set that causes the process variable to increase until it reaches the first switching value

exceeds. The above-mentioned steps are then carried out, in which case a first step is carried out in which the actuator is controlled with the first manipulated variable which corresponds to the difference between a manipulated variable mean value and a manipulated variable amplitude, so that the process variable falls. Subsequently, the aforementioned steps are carried out in such a way that the process variable alternates around the switching values, in particular between the first and the second

Switching value alternates. In a control loop in which the process variable is negatively dependent on the manipulated variable and in which the process variable is larger than the switching values, the actuator is controlled with a manipulated value that leads to a drop in the

Process size leads. As soon as the value falls below the second switching value, in this case the actuator is actuated with a first manipulated value in a first step, which corresponds to the difference between a manipulated variable mean value and a manipulated variable amplitude, so that the process variable increases. Then the

The aforementioned method steps are carried out in such a way that the process variable alternates around the switching values. The starting step is preferably carried out to bring the control loop into a state in which it is based on the binary

Sensor signal of a sensor unit can be operated alternately.

A preferred embodiment of the invention provides for the fall time and / or the rise time to be compared with an average of the two times and for a deviation to be reset. In particular, the manipulated variable mean value (u_mean) and the manipulated variable amplitude (delta) are set to their output values.

The comparison between the rise time and the descent time takes place in order to detect any faults in the control loop, since a significant change in the process variable is reflected in a change in the rise time or descent time. If there is such a difference between the rise time and the descent time determined, the manipulated variable is reset, in particular by the

The manipulated variable mean value and the manipulated variable amplitude can be set back to their initial values. In this way, malfunctions in the process variable are identified and remedied.

One embodiment of the invention provides that the first switching value and the second switching value have the same value.

This embodiment variant aims at a sensor unit which has only one switching value, a first sensor signal being output when this switching value is exceeded and a second signal value being output when this switching value is undershot. In this case, the inertia of the control loop causes the process variable to alternate around the individual switching value. By determining the fall time, which corresponds to the duration of the first signal value and the rise time, which corresponds to the duration of the second signal value, the first manipulated variable and the second manipulated variable can be adapted such that they converge with one another. The aforementioned method steps can be applied analogously. This

Embodiment corresponds to the simplest form of a sensor unit,

for example a float switch or a thermostat.

The actuator is preferably a pump, a valve, a pickling device or a cooling device.

The underlying method can be used for actuators whose manipulated variable can be continuously adjusted. In the case of a valve, the process variable is, for example, a flow rate, a level or a pressure, the process variable e.g. is the degree of opening of the valve. For a heating or

The cooling device is the process variable, for example a temperature, the manipulated variable in the meat processing device being an electrically generated output.

The actuator is preferably a speed-controlled pump, the manipulated variable being the speed of the pump. With the aforementioned actuators, low-wear and energy-efficient operation can be implemented on the basis of a binary sensor signal using the underlying method. The invention also relates to a two-point controller for regulating an actuator based on a binary sensor signal, having an input for the binary sensor signal and an output for a manipulated variable for controlling the

Actuator, the two-point controller being set up to carry out the method according to the invention.

Such a two-point controller can preferably be implemented by a microcontroller that carries out the underlying method. The implementation of the underlying method by means of an analog circuit is particularly preferred, since this can be implemented with simple components such as operational amplifiers and logic gates, and thereby advantages, e.g. in certification for safety-critical applications.

The invention also relates to an actuator which has a controller according to the invention.

Embodiments of the invention are explained below with reference to figures, wherein

1 a shows an application in which the process variable is positive from the

Manipulated variable depends, namely a container or room that is heated by means of a heating device,

Fig. 1 b shows an application in which the process variable is negative

Manipulated variable depends, namely a container that is emptied by means of a pump,

Fig. 2a shows the time course of a process variable, which by means of

underlying process is influenced,

2b shows the time course of a sensor signal, the one

Outputs sensor unit, 2c shows the time course of the manipulated variable with which the actuator is controlled, as well as the corresponding manipulated variables and the corresponding manipulated variable amplitude,

Fig. 3 shows a process diagram illustrating the features of the

underlying method, which lead to the temporal courses of Figures 2a, 2b and 2c, and

Fig. 4 schematically shows a two-point controller according to the invention, which is realized by means of analog components.

1 a shows an application example of the underlying method, in which the process variable P is positive from a manipulated variable u

Actuator 1 is influenced. It is a container 3 which is heated by means of a pickling device 1, the level P, in the example the temperature, being measured inside the container by means of a sensor unit 2. The

Sensor unit supplies a binary sensor signal y, which depends on the level P.

In particular, the sensor unit 2 outputs a first sensor signal value y1 when the process variable P exceeds a first switching value Sw1. If the

Process variable P falls below a second switching value Sw2, the sensor unit 2 outputs a second sensor signal value yO. In the illustrated case, the pickling device 1 is the actuator and the thermal output of the pickling device 1 is the manipulated variable u, which is controlled by means of the two-point controller 10. The straight arrows represent the flow direction of the medium to be heated. The flow rate of the medium varies as required.

1 b shows an application example in which the process variable P is negatively dependent on the manipulated variable u. It is a container 3 which is emptied by means of a pump 1, the level P inside the container 3 being measured by means of a sensor unit 2 which provides a binary sensor signal y. In this application, the level P falls with increasing manipulated variable u, or the speed of the pump 1. The control value u is controlled by the

Two-point controller 10, which is set up to carry out the method according to the invention. FIGS. 2a, 2b and 2c show, by way of example, the course of the process over time, the process variable P being positively dependent on the manipulated variable u, that is to say increasing as the manipulated variable u increases. The time t is given in seconds. At the maximum manipulated variable (u = 10), as it is at the beginning of the timeline, the increases

Process variable P an. 2b shows the binary sensor signal y, the first sensor signal value y1 being present when the process variable P is the first

Switching value Sw1 exceeds. The first signal value y1 is present until the process variable P falls below the second switching value Sw2, at which moment the second sensor signal value yO is output by the sensor unit. As shown in FIG. 2c, the manipulated variable u of the actuator 1 is controlled on the basis of the binary sensor signal y, the manipulated variable u in the present case assuming a first manipulated value u1 when the first sensor signal value y1 is present. When the second sensor signal value yO is applied, the manipulated variable takes on the second manipulated value u2. This can be seen particularly well in the time range between t = 800 s and t = 1000 s, since in this range the switching times between the first manipulated variable u1 and the second manipulated variable u2 are relatively long. As long as the actuator 1 is activated with the first manipulated value u1, the process variable P falls, so that the duration of the first sensor signal value y1 corresponds to a fall time t_fall. The process variable P falls when the actuator 1 assumes the second manipulated value u2, so that the duration of the second sensor signal value yO corresponds to a rise time t_rise.

The durations of the sensor signal values y1 and y2 are used in the underlying method to dynamically adapt the first manipulated variable u1 and the second manipulated variable u2 during the operation of the actuator 1 such that they converge with one another. As can be seen in FIG. 2c, the first manipulated variable u1 and the second manipulated variable u2 approach each other during the operation of the actuator 1. As a result, the switching jumps between the first manipulated variable u1 and the second manipulated variable u2 become smaller and smaller, which leads to a reduction in switching losses when the actuator 1 is set. This advantageously enables an energy-efficient and low-wear operation of the actuator 1, that is to say, for example a pump or a pickling device. By converging the first manipulated variable u1 to the second manipulated variable u2, the differences between the manipulated values are smaller, so that the change in the process variable P is slower he follows. A slower change in the process variable P has the consequence that the fall time t_fall and the rise time t_rise increase from cycle to cycle, so that the manipulated variable u is switched less and less. This also leads to the fact that the actuator 1 consumes less energy during operation and the

Wear on actuator 1 is reduced. The convergence of the manipulated values u1 and u2 can be seen particularly well in the time ranges around t = 200 s, t = 700 s and t = 1200 s.

The first manipulated variable u1 and the second manipulated variable u2 are adjusted so that the fall time t_fall and the rise time t_rise converge to the same value.

The adjustment of the fall time t_fall to the rise time t_rise can be seen in FIG. 2c in the time ranges before t = 500 s, before t = 1000 s and before t = 1500 s.

The first place value u1 and the second place value u2 are preferably calculated on the basis of a manipulated variable mean value u_mean and a manipulated variable amplitude delta. In the case shown, the first manipulated variable u1 corresponds to the difference between the manipulated variable mean u_mean and the manipulated variable amplitude delta. It is applied when the sensor unit 2 outputs the first sensor signal value y1, that is, when the process variable P exceeds the first switching value Sw1. As a result of the control with a reduced manipulated variable u, the process variable P falls until it falls below the second switching value Sw2 and the sensor unit 2 outputs the second sensor signal value y2. The duration of the first sensor signal value y1 corresponds to the fall time t_fall. As soon as the second sensor signal value y2 is present, the actuator 1 is driven with the second manipulated value u2, which then corresponds to the sum of the manipulated variable mean value u_mean and the manipulated variable amplitude delta.

The increased manipulated variable u causes the process variable P to increase, the second sensor signal value y2 being present until the process variable P has exceeded the first switching value Sw1. The actuator 1 is then actuated with the first manipulated variable u1, based on a newly determined manipulated variable mean value u_mean and a newly determined manipulated variable amplitude delta, which are determined on the basis of the fall time t_fall and the rise time t_rise. As can be seen from FIG. 2c, the manipulated variable amplitude delta is successively reduced, so that the first manipulated variable u1 and the second manipulated variable u2 converge with one another. In addition, the mean value of the manipulated variable is gradually adjusted u_mean, which converts after a plurality of cycles to a value at which the fall time t_fall and the rise time t_rise are the same.

The time profiles from FIGS. 2a, 2b and 2c are based on a method which is represented by the method diagram from FIG. 3, which is usually referred to as a structogram. The manipulated variable u is controlled as a function of the state of the control method, a distinction being made between states 1, 2 and 3.

The state 1 corresponds to a start step 101, in which the actuator 1 is controlled with a manipulated variable u, which leads to the first switching value Sw1 being exceeded or the first sensor signal value y1, ie y = 1, being present.

For this purpose, a manipulated variable u is created which corresponds to the sum of the manipulated variable mean u_mean and the manipulated variable amplitude delta, the output values u_mean = 5 and delta = 5. As soon as the first sensor signal value y1 is output by the sensor unit 2, that is to say y = 1, the system switches to state 2, which is represented by state = 2 and a dashed arrow.

State 2 corresponds to a first step 102, in which the actuator is controlled with a manipulated variable u which corresponds to the difference between the manipulated variable mean value u_mean and the manipulated variable amplitude delta. For the first cycle, this means that u = 0 since u_mean = 5 and delta = 5. The control with such a manipulated variable u causes the process variable P to increase. As soon as the process variable P has reached the first switching value Sw1, the sensor unit 2 outputs the second sensor signal value yO, ie y = 0, so that the right column of the

State 2 is running. The fall time t_fall is thus determined and changed to state 3, which is represented by state = 3 and a dashed arrow.

State 3 corresponds to a second step 103, in which a manipulated variable u is set which corresponds to the sum of the manipulated variable mean value u_mean and the manipulated variable amplitude delta. In the first cycle, the manipulated variable is u = 10 because the output values are u_mean = 5 and delta = 5. Due to the control with the maximum manipulated variable, the process variable P increases, with the sensor unit 2 continues to output the second sensor signal value yO, ie y = 0. As soon as the process variable P exceeds the first switching value Sw1, the sensor unit 2 outputs the first sensor signal value y1, ie y = 1. As a result, the left column of state 3 is executed, the rise time t_rise being determined.

Then, in a third step 104, a new manipulated variable mean value u_mean is determined on the basis of the rise time t_rise and the fall time t_fall. In the exemplary embodiment, when determining the new manipulated variable mean value u_mean, it is first queried whether the rise time t_rise is greater than the fall time t_fall. If this is the case, a correction factor according to k = 1 - sqrt (t_fall / t_rise) is determined. The new manipulated variable mean u_mean is based on the

Correction factor k is determined, where u_mean = u_mean + k ^* delta. In this case, the ratio of fall time t_fall and rise time t_rise is greater than 1, so that the correction factor k is positive and thus the new one

The manipulated variable mean is greater than the previous manipulated variable mean. In the event that the fall time is greater than the rise time, the correction factor k is calculated according to k = sqrt (t_rise / t_fall) - 1. In this case, the correction factor k is negative because the ratio of both times is less than 1. The new manipulated variable mean u_mean is in this case smaller than the old manipulated variable mean u_mean. By such

Correction is achieved that the new manipulated variable approaches u_mean a value at which the rise time t_rise is equal to the fall time t_fall. This

Adaptation of the manipulated variable mean value u_mean is shown in FIG. 2c by the light gray line. After the calculation of the new manipulated variable mean value ujnean, a fourth step 105 is carried out in the exemplary embodiment, in which the

Manipulated variable amplitude delta is reduced. This corresponds to the new one

Manipulated variable amplitude 0.9 times the old manipulated variable amplitude delta. If the reduction is carried out again, the manipulated variable amplitude delta decreases exponentially. After reducing the manipulated variable amplitude, state 2 is carried out, the newly determined one for calculating the manipulated variable u

The manipulated variable mean u_mean and the newly determined manipulated variable amplitude delta can be used. In the present case, the manipulated variable u corresponds to the difference between the new manipulated variable mean u_mean and the new manipulated variable amplitude delta. Due to the control with a reduced manipulated variable, the

Process variable P decreases again. As soon as the process variable P falls below the second switching value Sw2, the sensor unit 2 outputs the second sensor signal value yO, ie y = 0, so that the controller is switched to state 3, that is to say carries out the second step 103. Accordingly, the first step 102, the second step 103, the third step 104 and the fourth step 105 are carried out in succession and repeatedly, the manipulated variable mean value u_mean being adapted and the

Manipulated variable amplitude delta is successively reduced. After several cycles, the manipulated variable mean value u_mean approaches a value at which the fall time t_fall is equal to the rise time t_rise.

The manipulated variable amplitude delta is reduced until a minimal one

Manipulated variable amplitude value delta_min is reached. In the diagram of FIG. 2c, this is the case in the areas before t = 500 s, before t = 1,000 s and before t = 1500 s. A minimum manipulated variable amplitude delta_min is required in order to be able to determine fall times t_fall and rise times t_rise even if the

The manipulated variable mean u_mean reaches a value at which the rise time t_rise is equal to the fall time t_fall. The constant fluctuation of the process variable P and the associated repeated determination of the times t_fall and t_rise is necessary in order to be able to recognize any disturbances in the process variable P from the outside.

In the present embodiment, state 2 is when the first

Sensor signal value y1 (y = 1) is present, a test step 106 is carried out, in which the Fall time is compared with an average of the two times t_span (see Fig. 3 left column state 2). If the fall time t_fall is more than twice as long as twice the mean value from both times t_span, a reset takes place by resetting the manipulated variable mean value u_mean and the manipulated variable amplitude delta to their initial values. In the present case u_mean = 5 and delta = 5. In addition, the suppression of the manipulated variable calculation no_adj = 1 is switched on, so that no new calculation of the

The manipulated variable mean u_mean and the manipulated variable amplitude delta. 3, the query of suppression is represented by reference number 107. By suppressing the recalculation it is achieved that the control can quickly adapt to disturbances, so that the process variable P does not deviate too much from the desired value. In state 3, the test step 106 is carried out when the first sensor signal value yO (y = 0) is present.

In FIGS. 2a, 2b and 2c, a first disturbance is induced at time t = 500 s and a second disturbance is induced at time t = 1000 s. In the case of the first fault, the mean value u_mean is corrected upwards

required, whereby after several switching cycles an actuating value u_mean arises which is greater than the actuating value average u_mean at t = 500 s. In the example of heating a container with a pickling device, this disturbance could mean that the temperature has dropped due to the opening of the container, so that the output of the heating device must be increased in order to compensate for the temperature drop. In the case of the second fault, the manipulated variable mean value u_mean is corrected downward, with a manipulated variable mean value u_mean being obtained approximately after t = 1350 s, which corresponds to that at t = 500 s. The first malfunction is thus canceled out by the second malfunction, or the temperature drop through the opening is compensated for in the first malfunction.

In the exemplary embodiment, the manipulated variable u can be varied between 0 and 10 and represents an abstract value. It can be, for example, a voltage with which an actuator is operated. Based on the application example from FIG. 1 a, the heating power of the heating device would correspond to a value that is proportional to the manipulated variable u from FIG. 2 c. In an embodiment variant, not shown, the method can be transferred from the diagram in FIG. 3 to an application example in FIG. 1 b.

An exemplary embodiment of a controller 10 according to the invention is shown in FIG. 4

shown. The circuit diagram shown corresponds to an upper level, in which the individual blocks are each made up of analog circuits. In this case, the binary output signal y of the sensor unit 2 is applied to an input 11 and is output as a manipulated variable u at the output 12 by means of analog components, for example operational amplifiers and memory elements. The binary

Sensor signal y is applied to an input of a state machine 13, which has five states s1 to s5. State s1 serves to initialize the controller. State s2 is active when the first sensor signal value y1, ie y = 1, is present. State s3 is active when the second sensor signal value y2 is present, that is, y = 0. In state s4, the new manipulated variable mean u_mean is calculated. In state s5, the manipulated variable amplitude delta is reduced and the time measurement is reset. The states are subsequently changed by the state machine 13 in the sequence 1, 2, 3, 4, 5, 2, 3, 4, 5, 2 ... The state machine 13 outputs a signal rise, with which a first switch 21 is activated, so that the second manipulated variable u2 is present at the output 12, which leads to an increase in the process variable P. Does the

State machine 13 fails a signal, a switch 22 is controlled so that the first control value u1 is present at the output 12 and the process variable P falls.

In state s1, which corresponds to start step 101, in a first

Memory block 14 for the manipulated variable mean value u_mean set a voltage Vin1 which corresponds to the voltage from a voltage source 24, in the present case 5 volts. This supply voltage is also in a second memory block 15 for the

Manipulated variable amplitude delta set. The memory blocks 14 and 15 are sample-and-hold circuits with two predeterminable input values. The first memory block 14 and the second supply as output voltages

Memory block 15 each 5 volts, which are applied to the inputs of an adder 18 and a differentiator 19. The adder 18 supplies the sum of the two voltages as the output voltage, so that when the first switch 21 is activated, u = u_mean + delta is present at the output. The differentiator 19 delivers as Output voltage is the difference between the voltages so that a manipulated variable u = ujnean - delta is present at output 12 when the second switch 22 is activated.

In state s2, that is when the first sensor signal value y1 is present, a signal is applied to an input of a first integrator 16, the duration of the signal corresponding to the first signal value being output by means of the integrator 16 as voltage Vout. This voltage is applied to a mean calculation block 20 as t_fall.

When the state S3 is active, that is, when the second sensor signal value y0 is present, a signal is applied to a second integrator 17, the output voltage Vout of which corresponds to the rise time t_rise. The output voltage of the second

Integrators 17 is also used as the input of the mean value calculation block 20. The mean value calculation block 20 uses the fall time t_fall, the rise time t_rise, the manipulated variable mean value u_mean and the manipulated variable amplitude delta to determine a new manipulated variable mean value newUmean, which is applied to an input Vin2 of the first memory block 14.

As soon as the state s4 is activated, the calculation of the new one

Command value mean value newUmean carried out and this voltage set as output voltage in the first memory block 14 by activating the input setVin2. This output voltage is applied to the adder 18 and to the

Differentiators 19.

When state s5 is subsequently activated, the first integrator 16 and the second integrator 17 are reset. In addition, the value for the

The manipulated variable amplitude delta in the memory block 15 is reduced. The manipulated variable u at output 12 depends on the newly set manipulated variable mean of the first

Memory blocks 14 and the reduced manipulated variable amplitude of the second

Memory blocks 15 from.

The manipulated variable amplitude is not reduced if a reset is set by the mean value calculation block 20, which is applied to a flip-flop 30 and is combined with the second AND gate 29. In the same way Neither is a new manipulated variable mean value u_mean set when the reset is present, since the output s4 of the state machine and the output Q of the flip-flop 30 are linked to one another via a first AND gate 28. When the reset is activated, the first OR block 25 in the first memory block 14

Supply voltage of the voltage source 24 is set as the manipulated variable mean. In addition, when the reset is activated via a second OR gate 26 in the second memory block 15, the supply voltage of the voltage source 24 is shown as

Manipulated variable amplitude set. The reset is set by the mean value calculation block 20 if the fall time t_fall or the rise time t_rise deviates from the mean value of both times t_span.

With the circuit from FIG. 4, the underlying method can be implemented by means of an analog circuit, whereby these are only simple components such as

Operational amplifiers and logic gates required.

Such an analog circuit can be implemented as an integrated module which is inserted into an actuator 1, the actuator 1 being, for example, a pump, a valve, a heating device or a cooling device.

Advantageously, an energy-efficient and low-wear control of an actuator 1 can thus be implemented with little effort if a sensor unit 2 is used which provides a binary sensor signal y.

LIST OF REFERENCE NUMBERS

1 actuator

2 sensor unit

10 controllers

11 entrance

12 exit

13 state machine

14 first memory block (ujnean)

15 second memory block (delta)

16 first integrator (t_fall)

17 second integrator (t_rise)

18 adders

19 differentiators

20 mean calculation block

21 first switch (u1)

22 second switch (u2)

23 mass

24 voltage source

25 first OR gate

26 second OR gate

27 third OR gate

28 first AND gate

29 second AND gate

30 flip-flop

101 starting step

102 first step

103 second step

104 third step

105 fourth step

106 test step

107 Suppression query y sensor signal (binary) yi first sensor signal value

yo second sensor signal value

p Process size, level

Sw1 first switching value

Sw2 second switching value

u manipulated variable

u1 first manipulated variable

u2 second manipulated variable

t_fall fall time

t_rise rise time

t_span Average of the fall and rise times

u_mean command value mean

delta manipulated variable amplitude

delta_min minimum manipulated variable amplitude

k correction factor

state State of the controller

no_adj Suppression of the manipulated variable mean value calculation

Claims

Expectations

1. Method for two-point control of an actuator (1), based on a binary sensor signal (y) from a sensor unit (2), which detects a process variable (P) that can be influenced by the actuator (1) in such a way that when a first switching value (Sw1) is exceeded a first sensor signal value (y1) and at

Falling below a second switching value (Sw1, Sw2) a second

Outputs sensor signal value (yO), wherein the actuator (1) is controlled with a manipulated variable (u) that accepts either a first manipulated variable (u1) or a second manipulated variable (u2), characterized in that the first manipulated variable (u1) and second manipulated variable (u2) as a function of a fall time (t_fall), which corresponds to the duration of the first sensor signal value (y1), and a rise time (t_rise), which corresponds to the duration of the second sensor signal value (yO), during operation of the actuator (1) adjusted so dynamically that they converge.

2. The method according to claim 1, characterized in that the first manipulated variable (u1) and the second manipulated variable (u2) are dynamically adjusted so that the fall time (t_fall) and the rise time (t_rise) converge to the same value.

3. The method according to claim 1 or 2, characterized in that the

Procedure repeats the following steps:

- A first step (102), in which the actuator (1) is controlled with the first manipulated variable (u1), which is the difference from a manipulated variable mean

(u_mean) and a manipulated variable amplitude (delta), and the fall time (t_fall) is determined when the sensor unit (2) outputs the first sensor signal value (y1),

- a second step (103), in which the actuator (1) is controlled with the second manipulated variable (u2), which corresponds to the sum of the manipulated variable mean value (u_mean) and the manipulated variable amplitude (delta), and the rise time (t_rise) is determined when the sensor unit (2) outputs the second sensor signal value (yO), and

- A third step (104), in which a new manipulated variable mean value (u_mean) is determined from the fall time (t_fall) and the rise time (t_rise).

4. The method according to claim 1 or 2, characterized in that the

Procedure repeats the following steps:

- A first step in which the actuator (1) is controlled with the first manipulated variable (u1), which corresponds to the difference between a manipulated variable mean value (u_mean) and a manipulated variable amplitude (delta), and the rise time (t_rise) is determined when the Sensor unit (2) outputs the second sensor signal value (yO),

a second step, in which the actuator (1) is controlled with the second manipulated variable (u2), which corresponds to the sum of the manipulated variable mean value (u_mean) and the manipulated variable amplitude (delta), and in which the fall time (t_fall) is determined, when the sensor unit (2) outputs the first sensor signal value (y1), and

- a third step in which a new manipulated variable is determined (u_mean) from the fall time (t_fall) and the rise time (t_rise).

5. The method according to claim 3 or 4, characterized in that in a fourth step (105) there is a reduction in the manipulated variable amplitude (delta).

6. The method according to claim 5, characterized in that the fourth

Method step (105) is repeated until one of zero

different minimum manipulated variable amplitude (delta_min) is reached.

7. The method according to any one of the preceding claims, characterized in that the fall time (t_fall) and the rise time (t_rise) are compared with one another,

- The new manipulated variable mean value (u_mean) being increased if the rise time (t_rise) is greater than the fall time (t_fall), or

- The new manipulated variable mean (u_mean) is reduced if the rise time (t_rise) is less than the fall time (t_fall).

8. The method according to claim 7, characterized in that the new

Average manipulated variable (ujnean) according to

u_mean = u_mean + k * delta

is determined, where k is a correction factor which depends on the fall time (t_fall) and the rise time (t_rise), preferably on a ratio of fall time (t_fall) and rise time (t_rise).

9. The method according to claim 8, characterized in that the correction factor k = 1 - t_fall / t_rise

is when the rise time (t_rise) is greater than the fall time (t_fall) and the correction factor

k = t_rise / t_fall - 1

is when the rise time (t_rise) is less than the fall time (t_fall).

10. The method according to claim 8, characterized in that the correction factor k = 1 - sqrt (t_fall / t_rise)

k = sqrt (t_rise / t_fall) - 1

is when the rise time (t_rise) is less than the fall time (t_fall).

11. The method according to any one of the preceding claims, characterized in that first a starting step (101) is carried out, in which the actuator (1) is controlled with a manipulated variable (u), which leads to the fact that the first

Switching value (Sw1) exceeded or the second switching value (Sw2) is undershot.

12. The method according to any one of the preceding claims, characterized in that in a test step (106) the fall time (t_fall) and / or the rise time (t_rise) is compared with an average of both times (t_span) and a reset is carried out in the event of a deviation , especially where the

The manipulated variable mean value (u_mean) and the manipulated variable amplitude (delta) are set to their output values.

13. The method according to any one of the preceding claims, characterized in that the first switching value (Sw1) and the second switching value (Sw2) have the same value.

14. The method according to any one of the preceding claims, characterized in that the actuator (1) is a pump, a valve, a heating device or a cooling device.

15. Two-point controller (10) for controlling an actuator (1) based on a binary sensor signal (y), having an input for the binary

Sensor signal (y) and an output for a manipulated variable (u) for controlling the actuator (1), the two-point controller being set up to carry out the method according to claims 1 to 14.

16. Actuator (1) having a controller (10) according to claim 15.