Method for controlling a material feed, and metering system

Abstract

The method is suitable for controlling or regulating a material feed for filling a first container with a material from a second container. In the method, a rate of change of a fill level of the first container is determined. If the rate of change is positive, the material feed is reduced and, if the rate of change is negative, the material feed is increased. The rate of change is determined by means of a capacitive sensor.

Description

[0001] Description

[0002] Method for controlling a material feed and dosing system

[0003] A method for controlling a material feed is specified. Furthermore, a dosing system, which in particular has a material feed that can be operated using such a method, is specified.

[0004] One of the problems to be solved is, among other things, to provide an improved method for controlling a material feed and to provide an improved dosing system.

[0005] These objects are achieved, inter alia, by the subject-matter having the features of patent claims 1 and 9.

[0006] According to at least one embodiment of the method for controlling a material feed, the method is suitable for controlling or regulating a material feed for filling a first container with a material from a second container. In the method, a rate of change of a fill level of the first container is determined. If the rate of change is positive, the material feed is reduced, and if the rate of change is negative, the material feed is increased. The rate of change is determined by means of a capacitive sensor.

[0007] The material feed is, for example, a chain feed. For example, a conveyor chain or transport chain is driven by the material feed. Alternatively, the material feed is, for example, a screw feed. In this case, a screw conveyor is particularly preferably driven by the material feed.

[0008] The second container could be, for example, a storage container in which the material is stored or kept. During normal operation, the material can be conveyed from the second container into the first container using a transport unit driven by the material feed.

[0009] The transport unit is, for example, a conveyor chain or a transport chain. Alternatively, the transport unit is, for example, a conveyor screw.

[0010] The first container can be a dosing container from which the material can preferably be emptied in a controlled and / or uniform manner. For example, the material is applied evenly to a surface from the first container. This means, in particular, that the thickness of the material on the surface after application is homogeneous or substantially homogeneous. The material is, for example, grit. The surface to which the material is applied is, for example, a road or a prepared, e.g., rolled, subsurface.

[0011] By filling the first container with material from the second container and by possibly emptying the first container, the fill level of the first container changes. In order to ensure controlled emptying of the first container, it is advantageous if the fill level does not fall below a certain minimum. It is also desirable if the fill level does not rise above a certain maximum value in order to reduce the risk of the first container overflowing or to prevent overflowing. The method described here for controlling the material feed can advantageously be used to adjust the filling of the container in such a way that the fill level always lies between the desirable minimum and maximum values.

[0012] For example, if the first container is emptied faster than it is filled, the fill level will exhibit a negative rate of change, so the material feed rate must be increased to prevent the fill level from falling below the minimum value. If, on the other hand, the first container is filled faster than it is emptied, the fill level will exhibit a positive rate of change, so the material feed rate must be reduced accordingly.

[0013] The method for controlling the material feed described here allows the fill level of the first container to be adapted to different emptying or filling situations and to be kept within the limits of the minimum and maximum values.

[0014] The method described here is based, among other things, on the following technical considerations. The fill level of a container can be monitored using a capacitive sensor. A "capacitive sensor" here and below refers to a sensor with a capacitive measuring principle. In the following, the "capacitive sensor" may also be referred to simply as a "sensor". A capacitive sensor, referred to below as a "sensor", operates in particular with the capacitive measuring principle and is a capacitive sensor.

[0015] One measuring principle of the sensor is based on the fact that a capacitance of the sensor changes when the fill level changes, because a space in the sensor is filled with a dielectric material, namely the material in the container. As a result of the capacitance change of the sensor, a voltage applied to the sensor changes and can be detected as a measured value or signal. Alternatively, a current can be measured at the sensor, which also changes with the capacitance of the sensor. In this case, the current is the measured value. Consequently, a measured value or signal value, in particular the entire signal of the sensor, is material-dependent. The reason for this is in particular the different dielectric properties of different materials. This means that at the same fill level, different materials result in a different initial value for the capacitive sensor.Therefore, to determine the absolute fill level, the capacitive sensor must be calibrated. The disadvantage of this is that the calibration must be repeated each time a different material is added to the container. Furthermore, such calibration is prone to errors. Incorrect calibration can lead to malfunctions, including a complete standstill of the material feed or a machine using the first container.

[0016] The method described here utilizes the idea of ​​considering a gradient, or a rate of change in the fill level. By determining the rate of change, the material-dependent absolute signal value of the capacitive sensor, which corresponds to the absolute fill level, can be equalized. Therefore, material properties, especially the dielectric properties of the material in the container, are irrelevant.

[0017] Advantageously, this eliminates the need to calibrate the capacitive sensor to the material in the container. Only a so-called zero adjustment to the ground potential is necessary. This can, however, be performed at the factory, for example, and advantageously does not need to be repeated.

[0018] According to at least one embodiment or at least one of the embodiments described above, the sensor is arranged in the first container. In particular, the sensor is arranged in the first container such that a material with which the first container is filled or emptied passes the sensor during emptying or filling.

[0019] The capacitive sensor comprises, for example, an electrically conductive sensor element and a grounded housing. The electrically conductive sensor element is, for example, an electrically conductive cable, such as a metal cable. In this case, the capacitive sensor is also referred to as a cable sensor. Alternatively, the electrically conductive sensor element is, for example, a rod, such as a metal rod or a metal plate.

[0020] The sensor element is preferably electrically insulated from the grounded housing. The housing functions, for example, as the first electrode and the sensor element as the second electrode of the capacitive sensor. The housing of the capacitive sensor is preferably identical to the first container. This means, in particular, that the sensor is formed by the sensor element and the first container.

[0021] When the first container is filled, the capacitance of the capacitive sensor changes, with a corresponding capacitor being formed by the housing or the first container as the first electrode and the sensor element as the second electrode. If a voltage is applied to the capacitive sensor, this change in capacitance can be detected as a change in voltage. The voltage applied to the capacitive sensor corresponds in particular to a signal from the capacitive sensor. An individual voltage value of the applied voltage corresponds to a signal value from the capacitive sensor.

[0022] According to at least one embodiment of the method or at least one of the embodiments described above, the rate of change is determined independently of the material with which the first container is filled or emptied. Since, in the method, the material feed is adjusted only based on the rate of change of the signal value of the capacitive sensor and not on the basis of the absolute signal values, the material feed can be adjusted independently of the material in the first container.

[0023] According to at least one embodiment of the method or at least one of the embodiments described above, the following sub-steps are carried out to determine the rate of change. In the first sub-step, a plurality of change values ​​of the signal from the capacitive sensor are recorded over a plurality of time intervals. This means that the change value recorded is how the signal value changes within a specific time interval. In other words, the change value corresponds to the average gradient of the signal in a time interval, in particular in a graphical plot of the signal versus time.

[0024] Preferably, a large number of change values ​​are recorded and stored.

[0025] In a further substep, the rate of change is determined by calculating an average from the large number of change values. For example, the stored change values ​​are arithmetically averaged. The rate of change thus corresponds to an average over a large number of changes in individual time intervals.

[0026] According to at least one embodiment of the method or at least one of the embodiments described above, the rate of change is determined by averaging over several change values. In particular, 10 or more change values ​​are averaged to determine the change values. For example, the rate of change is determined by averaging exactly over 10 change values.

[0027] According to at least one embodiment of the method or at least one of the embodiments described above, in the case of a positive rate of change, the rate of change is multiplied by a first weighting factor and in the case of a negative rate of change, the rate of change is multiplied by a second weighting factor.

[0028] Multiplying the rate of change by the weighting factors preferably results in a control signal for the material feed. The control signal is preferably proportional to the rate of change. The control signal, in particular, corresponds to the material feed.

[0029] Preferably, the weighting factors are selected so that a relative change in the material feed rate is no more than 10%. This advantageously reduces very large changes in the material feed rate and protects the hydraulic system of the entire machine.

[0030] According to at least one embodiment of the method or at least one of the embodiments described above, the first container has metering locks for emptying the first container. When the metering locks are closed, the material feed is stopped. In other words, if the first container is not emptied, it will not be further filled.

[0031] The dosing locks are, in particular, rotatable. This means that the first container is emptied by rotating the dosing lock. In the case of rotatable dosing locks, for example, the dosing locks are rigid when closed. Rotatable dosing locks allow the first container to be emptied in a particularly controlled manner and the material from the first container to be distributed particularly evenly over a surface or the like.

[0032] According to at least one embodiment of the method or at least one of the embodiments described above, the method further comprises the following steps . In a step A), a signal value of the capacitive sensor is determined . The signal value is in particular a raw value or a measured value of the capacitive sensor . This means that this value is preferably not

[0033] Weight factor or another factor.

[0034] In step B), this signal value is compared with a minimum signal value. This comparison ensures that the fill level within the first container has a minimum value. This means that the minimum signal value specifies a lower limit for the fill level. Calibration of the capacitive sensor can advantageously be dispensed with, since the minimum signal value can be selected such that a sufficient fill level is present for every conceivable relevant material when the minimum signal value is exceeded.

[0035] In a further step C ) the material feed is increased by 1 % in the case that the initial signal value is smaller than the minimum signal value .

[0036] In particular, steps A) to C) are carried out before determining the rate of change.

[0037] Preferably, steps B) and C) are carried out alternately until the signal value is greater than the minimum signal value.

[0038] Preferably, steps A) to C) are carried out before the first container is emptied. Steps A) to C) can ensure, in particular, that a minimal amount of material is present in the first container before the first container is emptied, so that uniform emptying of the container is possible. Subsequent control during the emptying of the first container is carried out, in particular, by considering the rate of change as described here.

[0039] Furthermore, a dosing system for a material is specified. The dosing system comprises, in particular, a control unit configured to carry out a method described herein. This means that all features disclosed for the method are also disclosed for the dosing system, and vice versa.

[0040] According to at least one embodiment, the dosing system comprises a first container with a capacitive sensor and dosing locks for emptying the first container. The dosing system also comprises a second container. This is in particular a storage container for the material. The dosing system further comprises a transport unit for filling the first container with material from the second container. The transport unit is in particular designed to be operated with a predeterminable material feed. Furthermore, the dosing system has a control unit which is designed to carry out a method described here and to predetermine the material feed.

[0041] With the dosing system, the material can be transferred from the second container into the first container and emptied from the first container in a controlled manner via dosing locks.

[0042] The dosing system can, for example, be integrated into a construction vehicle or the like for spreading grit. The material is then, for example, grit that is spread via the first container and the dosing locks. For example, the grit should be distributed evenly over a surface, such as a road or the like. It is particularly advantageous if the grit is distributed evenly. For this purpose, the first container is preferably filled to a certain fill level. The method described here can ensure that the fill level always remains within a desired range.

[0043] For example, the first container serves as an intermediate container between the storage container and the dosing locks and is designed to distribute the material, for example the grit, evenly to the dosing locks.

[0044] Further advantages and advantageous embodiments and further developments of the method and the dosing system will become apparent from the following in conjunction with the exemplary embodiments shown in the schematic drawings. Identical, similar and similarly acting elements are provided with the same reference symbols in the figures. The figures and the relative sizes of the elements shown in the figures are not generally to scale. Rather, individual elements may be shown exaggeratedly large for clarity and / or to improve comprehensibility.

[0045] It shows :

[0046] Figure 1 shows a schematic perspective view of a dosing system described here according to an embodiment; Figure 2 shows a diagram of a time course of a signal value of a sensor described here;

[0047] Figure 3 is a schematic block diagram of a method described here according to an embodiment;

[0048] Figure 4 is a schematic illustration of a sensor as it can be used in a method described here.

[0049] The dosing system 1 of Figure 1 comprises a first container 2 and a second container 3. The first container 2 can be filled with material 20 from the second container 3 via a transport chain 6, which can be operated with a material feed 100.

[0050] The second container 3 is, in particular, a storage container for the material 20. The material 20 is, for example, grit that can be applied to a surface in a controlled and preferably uniform manner using the dosing system 1.

[0051] The first container 2 has rotatable dosing locks 5. The first container 2 can be emptied through the rotatable dosing locks 5.

[0052] The first container 2 further comprises a capacitive sensor 10. The sensor 10 has an electrically conductive sensor element 12, such as a metal cable. The sensor 10 is, for example, a cable sensor. The sensor element 12 is preferably electrically insulated from the first container 2. The first container 2 is a housing 11 for the sensor 10. The sensor 10 is a capacitive sensor. During normal operation, a voltage is applied to the sensor 10, the housing 11 being grounded and the sensor element 12 being brought to a specific electrical potential. The housing 11 forms a first electrode of the capacitive sensor 10 and the sensor element 12 forms a second electrode.

[0053] If a fill level changes in a space between the housing 11 and the sensor element 12, i.e. between the first and second electrode of the sensor 10, the capacitance of the sensor 10 and the voltage applied to the sensor 10 change. In this way, a fill level of the first container 2 can be determined on the basis of the voltage measured at the sensor 10. A signal value 15 of the sensor 10, which corresponds to the measured voltage, is, however, material-dependent, since different materials influence the change in the capacitance of the sensor 10 differently due to their different dielectric constants. Therefore, a calibration of the sensor 10 is necessary in order to obtain an absolute value for the fill level.

[0054] The method described here makes use of the idea of ​​not considering the absolute signal values ​​15 of the sensor 10, but of determining a rate of change 4 from a change in the voltage of the sensor 10 or the signal of the sensor 10 in order to regulate the material feed 100. This makes it possible, for example, to regulate the filling or emptying of the container 2 so that the container 2 does not overflow or is completely emptied. It is therefore possible to keep the fill level of the container 2 within predeterminable limits using the sensor 10 described here. Figure 2 shows a diagram illustrating a temporal progression of a signal value 15. The signal value 15 is plotted against time 51. In the exemplary embodiment of the method shown in Figure 2, a large number of change values ​​l On are recorded. The change values ​​l On are recorded at time intervals l In.This means that in the method described here, a temporal change in the signal value 15 in a specific time interval l ln is recorded and stored as a change value l On . Figure 2 illustrates the recording of a change value l On in a time interval l ln .

[0055] In the method described here, a change rate 4 of the fill level of the first container 2 is determined from these change values ​​l On . For this purpose, the change values ​​l On are averaged, for example.

[0056] In the method according to the exemplary embodiment of Figure 3, a first signal value 15 is determined in a first method step 201. In method step 201, the signal value 15 is compared with a minimum signal value 19. The signal value 15 corresponds to a fill level of the first container.

[0057] If the signal value 15 is smaller than the minimum signal value 19, the material feed 100 is increased in method step 210 in order to increase the signal value 15. For example, in method step 210 the material feed 100 is increased relatively by 1% every 100 ms. The signal value 15 is continuously determined and compared with the minimum signal value 19. If the signal value 15 is greater than the minimum signal value 19, it is determined in a method step 202 whether the dosing locks 5 are open or closed. If the dosing locks are rotatable dosing locks, it is determined in step 202 whether the dosing locks are rigid or rotating.

[0058] If the dosing locks are closed or rigid, the material feed 100 is stopped in step 211. The reason for this is that if the dosing locks are closed or rigid, the first container is no longer emptied, and further filling of the first container 2 with material 20 from the second container 3 carries the risk of the first container 2 overflowing.

[0059] If the dosing locks 5 are open or rotating, a change rate 4 is determined in method step 203, and it is established whether a new change rate 4 is available. If no new change rate 4 is available, i.e., if the change rate 4 has not changed compared to a previous run of the method, for example, no change takes place (method step 212).

[0060] If the rate of change 4 has changed, it is determined in step 204 whether the rate of change 4 is positive or negative. If the rate of change 4 is negative, the rate of change 4 is multiplied by a first weighting factor 41 in step 207 in order to obtain a control value 40 in method step 208 (method step 208).

[0061] If, however, the change rate 4 is positive, the change rate 40 is multiplied by a second weighting factor 42 in method step 205 in order to obtain a control value 40 (method step 208).

[0062] The weighting factors 41, 42 are selected such that the material feed rate 100 changes by a maximum of 10%. The control value 40 has a direct correspondence to the material feed rate 100. Preferably, the control value 40 is proportional, in particular directly proportional, to the change rate 4.

[0063] Subsequently, the process can be repeated several times in order to achieve continuous control of the material feed 100.

[0064] The sensor 10 of Figure 4 is used, for example, in the dosing system 1 of Figure 1. The sensor 10 has a housing 11 and an electrically conductive sensor element 12. The housing 11 can be the first container 2. The sensor 10 is arranged in the first container 2 in particular such that when the container 2 is filled or emptied, a material 20 passes through the sensor 10. This makes it possible to detect a change in the capacitance of the sensor 10. For this purpose, the housing 11 has an inlet opening 17 and an outlet opening 18.

[0065] The sensor 10 further comprises a measuring device 13 and an evaluation unit 14. The measuring unit 13 and the evaluation unit 14 together form, in particular, a control unit 16. For example, a signal and a signal value 15 of the sensor 10 can be determined via the measuring unit 13. For example, the measuring unit 13 is a voltmeter or an ammeter. The evaluation unit 14 is particularly configured to carry out the method described here.

[0066] The invention described here is not limited by the description based on the exemplary embodiments.

[0067] Rather, the invention encompasses any new feature and any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments.

[0068] Reference symbol list

[0069] 1 dosing system

[0070] 2 first containers

[0071] 3 second container

[0072] 4 Rate of change

[0073] 5 dosing locks

[0074] 6 transport unit

[0075] 10 Sensor

[0076] 11 housings

[0077] 12 Sensor element

[0078] 13 measuring unit

[0079] 14 Evaluation unit

[0080] 15 Signal value

[0081] 16 Control unit

[0082] 17 Entrance opening

[0083] 18 Exit opening

[0084] 19 minimum signal value

[0085] 20 materials

[0086] 40 Control value

[0087] 41 first weighting factor

[0088] 42 second weighting factor

[0089] 51 Time

[0090] 100 Material feed l On Change value l ln Time interval

[0091] 201...212 process steps

Claims

Claims 1. A method for controlling a material supply (100) for filling a first container (2) with a material (20) from a second container (3), comprising - determining a change rate (4) of the level of the first container (2), wherein - in the case of a positive change rate (4) of the material supply (100) is reduced, - in the case of a negative change rate (4) of the material supply (100) is increased, and wherein - the change rate (4) is determined by means of a capacitive sensor (10).

2. The method according to claim 1, wherein - the sensor (10) is arranged in the first container (2), and - the sensor (10) comprises a current-carrying sensor element (12) and a grounded housing (11).

3. Method according to claim 1 or 2, wherein the rate of change (4) is determined independently of the material (20) with which the first container (2) is filled.

4. Method according to one of the preceding claims, wherein determining the rate of change (4) comprises the following steps: - Determination of a plurality of change values ​​(lOn) of a signal (15) of the sensor (10) over a plurality of time intervals (lln), - Determination of the rate of change (4) by forming an average value from the plurality of change values ​​(101, .10n).

5. The method according to claim 4, wherein a plurality of change values ​​(lOn) are averaged to determine the rate of change (4).

6. Method according to one of the preceding claims, wherein - in the case of a positive rate of change (4), the rate of change (4) is multiplied by a first weighting factor (41) is multiplied, and - in the case of a negative rate of change (4), the rate of change is multiplied by a second weighting factor (42), wherein the weighting factors (41, 42) are each selected such that a relative change in the material feed (100) is at most 10%.

7. Method according to one of the preceding claims, wherein - the first container (2) dosing locks (5) for emptying the first container (2) and - when the dosing locks (5) are closed, the material feed (100) is stopped.

8. Method according to one of the preceding claims, further comprising A) Determining a signal value (15) of the sensor (10), B) Comparison of the signal value (15) with a minimum signal value (19), C) Increase of the material feed (100) by 1% in case the initial signal value (15) is smaller than the minimum signal value (19) , where - steps A) to C) are carried out before determining the rate of change (40), and - steps B) and C) are carried out alternately as long as the signal value (15) is smaller than the minimum signal value (19).

9. Dosing system (1) for a material (20) comprising - a first container (2) with a sensor (10) and Dosing locks (5) for emptying the first container (2) , - a second container (3) , - a transport unit (6) for filling the first container (2) with material (20) from the second container (3) , - a control unit (16), wherein - the transport unit (6) is designed to be operated with a predeterminable material feed (100), and - the control unit (16) is configured to carry out a method according to one of the preceding claims and to specify the material feed (100).

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