Methods for feedback control, programs for feedback control, and filter systems

Abstract

To provide a rotary filter device control method where load is hardly imposed to a device even when shift to various different operation conditions in treatment capacity is necessary.SOLUTION: In a feedback control method of a rotary filter device where an endless belt-shaped filter movable by the rotation of a rotor is disposed,: a first parameter set and a second parameter set are previously set as the parameter sets of feedback control; the feedback control using the first parameter set is performed when a predetermined condition on water to be treated flowing in the rotary filter device is not satisfied; and the feedback control using the second parameter set is performed when the predetermined condition is satisfied.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005] , , ,

[0001] The present invention relates to a method of feedback control and a program for feedback control used for controlling a rotary filter device, and a filter system.

Background Art

[0002] A rotary filter device used for sewage treatment or the like is a device provided in the form of an endless belt-shaped filter in which a plurality of panel filters are connected. By rotating the endless belt-shaped filter, solids in the water to be treated are separated while the filter is regenerated. In this type of device, the processing capacity of the device can be adjusted by adjusting the rotation speed of the endless belt-shaped filter.

[0003] For example, Japanese Patent Application Laid-Open No. 8-177030 (Patent Document 1) discloses a method of operating a screen moving type dust collector in which when it is detected that the water level has risen to the set water level, the dust collector is controlled to be operated at a high speed and then the operating speed is gradually decreased, and when the water level is below the set water level, the dust collector is controlled to stop or operate at a very low speed and wait. According to the operation method of Patent Document 1, unnecessary high-speed operation can be avoided.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technology described in Patent Document 1, the speed change when switching the operating speed is discontinuous. For example, a change in drive speed in a very short time can cause the chain and sprocket to become misaligned, increasing the risk of tooth skipping. This can lead to increased load on rotating equipment such as rotors. Consequently, there was a risk of shortening the lifespan of the rotary filter device.

[0006] Therefore, even when it is necessary to switch to operating conditions with different processing capacities, control of the rotary filter device that does not place a heavy load on the equipment is desirable. [Means for solving the problem]

[0007] The feedback control method according to the present invention is a feedback control method for a rotary filter device provided with an endless strip filter that is movable by the rotation of a rotor, The feedback control is PI control or PID control, As a parameter set for feedback control, at least the first parameter set This parameter set is one in which proportional action contributes more significantly compared to the first parameter set mentioned above. Second parameter set and, This is pre-set, Each of the following equations (1) and (2) conditions at least one of If the condition is not met, feedback control is performed using the first parameter set. Each of the following equations (1) and (2) The conditions at the same time The method is characterized by performing feedback control using the second set of parameters if the conditions are met. L(t)>a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge used to measure the water level.

[0008] Furthermore, the program for feedback control according to the present invention is a program for feedback control of a rotary filter device provided with an endless strip filter that is movable by the rotation of a rotor, The feedback control is PI control or PID control, As a parameter set for feedback control, the first parameter set This parameter set is one in which proportional action contributes more significantly compared to the first parameter set mentioned above. Second parameter set and,When this is pre-configured and executed by the computer, Each of the following equations (1) and (2) A determination function that determines whether or not the conditions are met, and in the determination function Each of the following equations (1) and (2) conditions at least one of When it is determined that the condition is not met, a first control function performs feedback control using the first parameter set, and in the determination function Each of the following equations (1) and (2) The conditions at the same time The invention is characterized by realizing a second control function that performs feedback control using the second parameter set when it is determined that the conditions are met. L(t)>a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge used to measure the water level.

[0009] Furthermore, the filter system according to the present invention comprises a rotary filter device provided with an endless strip filter that is movable by the rotation of a rotor, and a control device that performs feedback control of the rotary filter device, The aforementioned feedback control is PI control or PID control, The control device, The aforementioned As a parameter set for feedback control, the first parameter set This parameter set is one in which proportional action contributes more significantly compared to the first parameter set mentioned above. Second parameter set and, The settings are predetermined, and the control device, Each of the following equations (1) and (2) conditions at least one of If the condition is not met, feedback control is performed using the first parameter set. Each of the following equations (1) and (2) The conditions at the same time The system is characterized by being configured to perform feedback control using the second set of parameters if the conditions are met. L(t)>a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge used to measure the water level.

[0010] According to these configurations, since feedback control is always performed regardless of which of the two parameter sets is used, the operating conditions of the device can be continuously changed. Therefore, even when it is necessary to shift to operating conditions with different processing capabilities, it is difficult to impose a load on the device. With these configurations, the operating conditions can be changed in accordance with the rise in water level, making it easier to prevent overflow on the primary side of the endless strip filter. With these configurations, the use of feedback control using the second parameter set can be limited to cases where there is a particularly high need. With these configurations, feedback control can be performed using an appropriate parameter set according to the degree of disturbance suppression required.

[0018] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments described with reference to the drawings.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing the configuration of a filter system according to an embodiment. [Figure 2] It is a flowchart showing the procedure of a feedback control method according to an embodiment.

Modes for Carrying Out the Invention

[0020] Embodiments of a feedback control method, program, and filter system according to the present invention will be described with reference to the drawings. Hereinafter, an example in which the feedback control method according to the present invention is applied to the control of a rotary filter device 1 provided in a filter system 100 will be described.

[0021] 〔Configuration of Filter System〕 The filter system 100 includes a rotary filter device 1 and a control device 2 (FIG. 1).

[0022] The rotary filter device 1 is a rotary filter type sludge separation device having a filter unit 11. The filter unit 11 is provided in the form of an endless strip filter in which multiple panel filters with mesh sizes of 0.1 to 1.0 mm are connected. The rotary filter device 1 is also provided with multiple rotors 12 for moving each panel filter of the filter unit 11. The rotors 12 are electrically connected to the control device 2 and transmit information about the operating state of the rotors 12 (rotation speed, current value, etc.) to the control device 2, and can also receive control signals from the control device 2 that determine the operating conditions of the rotors 12.

[0023] In the rotary filter device 1, a filter unit 11 is provided in such a manner that it crosses the flow path of the water to be treated W1 that flows into the rotary filter device 1. The filter unit 11 is provided in such a manner that it is inclined from the upstream side to the downstream side of the flow path of the water to be treated W1, and the rotation of the rotor 12 causes the panel filter to move from bottom to top on the primary side into which the water to be treated W1 flows. Debris S contained in the water to be treated W1 is blocked by the filter unit 11, and filtered water W2, which is the water in the water to be treated W1, passes through the filter unit 11. Debris S remaining on the panel filter of the filter unit 11 is transported as the panel filter moves and is detached from the filter unit 11 by the cleaning mechanism 13. The cleaning mechanism 13 includes, for example, a scraper 13a that scrapes off the debris S from the filter unit 11, and a spray 13b that sprays cleaning water from the back side of the filter unit 11 to detach the debris S from the filter unit 11.

[0024] A water level gauge 14 is provided on the primary side of the filter unit 11 of the rotary filter device 1, allowing detection of the water level on the primary side of the filter unit 11. The output of the water level gauge 14 is input to the control device 2.

[0025] The control device 2 is implemented as a known computer. Therefore, the control device 2 includes general computer components such as an arithmetic unit, a memory device, and an input / output device. The control device 2 has a control program installed for performing feedback control of the rotary filter device 1, and this control program is an example of a program according to the present invention. The control device 2 is electrically connected to the rotor 12 and the water level gauge 14, and can receive information regarding the operating state of the rotor 12 (rotation speed, current value, etc.) and the water level detected by the water level gauge 14, as well as transmit control signals that determine the operating conditions of the rotor 12. Such control signals are generated by the feedback control described below.

[0026] [Feedback control method] The feedback control method according to this embodiment is implemented by executing a control program installed in the control device 2. In this embodiment, the feedback control is implemented as PI control, and two sets of PI control parameters are pre-set. The first set of parameters is used for normal control, and the second set of parameters is used for emergency control. An emergency is when the load on the rotary filter device 1 suddenly increases due to external factors such as rainfall or cleaning of the pumping station, and normal conditions are when there is no emergency. The two sets of parameters are stored in the memory of the control device 2 and are read as needed.

[0027] Comparing the two parameter sets, the second parameter set is configured to be more sensitive to disturbances than the first parameter set. Specifically, the second parameter set has a larger contribution from proportional motion (larger proportionality constant) compared to the first parameter set. Also, the integration time is shorter with the second parameter set than with the first parameter set, but since the variables are larger when the second parameter set is applied compared to when the first parameter set is applied, the product of the variables and the integration time is the same regardless of which parameter set is applied. In other words, the contribution of integral motion is the same for both the first and second parameter sets. While adopting the second parameter set has a greater effect in suppressing disturbances, if it is used regularly, there is a risk of overshoot, and there is a concern that the load on the device itself (especially the rotor 12) will increase due to repeated starting and stopping at short time intervals. Therefore, in this embodiment, the second parameter set is adopted only when there is a strong need for disturbance suppression, i.e., in emergencies, and the first parameter set is adopted at all other times (normal times).

[0028] The determination of whether it is a normal or emergency situation is based on the output of the water level gauge 14 (the water level on the primary side of the filter unit 11). Specifically, an emergency situation is determined when the conditions expressed by the following equations (1) and (2) are met simultaneously. L(t)>a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the filter unit 11 at a certain time t, Δt is a predetermined unit period, and a and b are predetermined thresholds.

[0029] Specifically, the determination is made according to the procedure shown in flowchart 200 in Figure 2. The first determination is determination 201 based on equation (1), which is a determination concerning the current water level on the primary side of the filter unit 11. When the water level L(t) at a certain time t is less than or equal to a predetermined threshold a (determination 201: no), it can be said that there is sufficient capacity on the primary side of the filter unit 11 to accept the water to be treated W1. In this case, even if the inflow rate of the water to be treated W1 increases due to a disturbance, the system can continue to accept the water to be treated W1, and therefore, there is no need to switch to emergency control. Therefore, if the condition of equation (1) is not met, it is determined that it is a normal situation without making the determination of equation (2) (process 205), and feedback control using the first parameter set is continued (process 206). On the other hand, if the condition of equation (1) is met (determination 201: yes), the determination of equation (2) is then made.

[0030] The second determination is determination 202 based on equation (2), and is a determination relating to the rate of rise in water level. When the amount of rise in water level L(t)-L(t-Δt) in the unit period Δt immediately preceding a certain time t is less than or equal to a predetermined threshold b (determination 202: no), it can be said that the balance of the treated water W1 is roughly balanced. In this case, even if the water level is greater than the threshold a, the possibility of the water level rising suddenly is small, so there is no need to switch to emergency control. Therefore, even if the conditions of equation (1) are met, if the conditions of equation (2) are not met, it is determined that it is a normal state (process 205), and feedback control using the first parameter set is continued (process 206).

[0031] On the other hand, if the condition of equation (2) is met (Judgment 202: Yes), then both equation (1) and equation (2) are met simultaneously, the water level is relatively high, and the inflow of treated water W1 is greater than the processing rate (the balance of treated water W1 is not balanced). In this case, it is determined to be an emergency (Process 203). At this time, it is necessary to temporarily increase the processing rate of the rotary filter device 1 to prevent overflow of treated water W1, so feedback control using the second parameter set is performed (Process 204). As described above, the second parameter set is more sensitive to disturbances than the first parameter set, so it can react sensitively to a rapid rise in water level and increase the output of the rotor 12, thereby smoothly and quickly increasing the processing rate of the rotary filter device 1.

[0032] Subsequently, the same flow of judgment is repeated to appropriately select the parameter set used for feedback control according to the situation at the time the judgment is made.

[0033] The threshold a can be set considering conditions such as the capacity of the rotary filter device 1, the normal inflow rate of the water to be treated W1 at the installation site of the rotary filter device 1, the rated capacity of the rotor 12, and the processing capacity of the control device 2. As an example, the threshold a may be 60-70% of the full water level on the primary side of the filter unit 11.

[0034] The threshold b and unit period Δt can be set considering the capabilities of the water level gauge 14. For example, if we want to determine that an emergency has occurred when the rate of rise in the water level exceeds 0.5 cm per second in the second determination (determination 202), the combinations of threshold b and unit period Δt are not limited as long as b = 0.5 Δt, so there are infinitely many combinations such as 1 cm and 2 seconds, 2 cm and 4 seconds, 3 cm and 6 seconds, etc. In this case, it can be said that adopting a combination with a shorter unit period Δt is preferable in that the determination of an emergency is less likely to be delayed. On the other hand, if the threshold b is excessively small, the amount of rise in water level L(t) - L(t - Δt) compared with the threshold b will fall below the smallest unit of difference in water level that the water level gauge 14 can detect, and the reliability of the detected value of the amount of rise in water level L(t) - L(t - Δt) will be impaired, thus reducing the accuracy of the second determination (determination 202). Therefore, the threshold b and the unit period Δt can be determined as a combination of threshold b and unit period Δt that gives an appropriate value for threshold b in light of the accuracy of the water level gauge 14, among the combinations of threshold b and unit period Δt that give an appropriate rate of rise in water level when determining an emergency.

[0035] For example, the unit period Δt can be the period used to determine whether a situation is normal or an emergency. In this case, the rise in water level L(t)-L(t-Δt) can be defined as the difference between the water level L(t) at the time of determination in a given period and the water level L(t-Δt) at the time of determination one period prior to that period. That is, by repeatedly recording the water level at a period of unit period Δt, it can be determined that the condition of equation (2) is met when the difference between the latest water level and the water level one period prior exceeds the threshold b.

[0036] [Other Embodiments] Finally, other embodiments of the feedback control method, program, and filter system according to the present invention will be described. Note that the configurations disclosed in each of the following embodiments may be applied in combination with configurations disclosed in other embodiments, provided that this does not create a conflict.

[0037] In the above embodiments, examples were described in which predetermined conditions for determining the parameter set used for feedback control are expressed by equations (1) and (2). However, in the feedback control method according to the present invention, the predetermined conditions for determining the parameter set used for feedback control are not limited. That is, they may be conditions based on the water level, as in the above embodiments, or they may be conditions based on other physical properties of the water to be treated (such as flow rate, suspended solids (SS), turbidity, etc.).

[0038] In the above embodiment, a configuration in which the second parameter set contributes more to proportional action than the first parameter set was described as an example, but the invention is not limited to this configuration. In the feedback control method according to the present invention, the relationship between the first parameter set and the second parameter set is such that, depending on the purpose of setting predetermined conditions for determining the parameter set to be used for feedback control, it is possible to realize control suitable for each of the two states separated by said predetermined conditions.

[0039] In the above embodiment, a configuration in which feedback control is implemented as PI control was described as an example. However, the feedback control according to the present invention is not limited to PI control, and may be PID control, for example.

[0040] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention. [Industrial applicability]

[0041] The present invention can be used, for example, for sludge separation in activated sludge treatment facilities. [Explanation of Symbols]

[0042] 100: Filter System 1: Rotary filter device 11: Filter Unit 12: Rotor 13: Cleaning mechanism 13a: Scraper 13b: Spray 14: Water level gauge 2: Control device S: scum W1: Water to be treated W2: Filtered water

Claims

1. A feedback control method for a rotary filter device equipped with an endless strip filter that is movable by the rotation of a rotor, The aforementioned feedback control is PI control or PID control, As the parameter set for the feedback control, at least a first parameter set and a second parameter set which has a greater contribution to proportional operation compared to the first parameter set are set in advance. If at least one of the conditions expressed by the following equations (1) and (2) is not met, feedback control using the first parameter set is performed. A feedback control method that performs feedback control using the second parameter set when the conditions expressed by the following equations (1) and (2) are simultaneously satisfied. L(t) > a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge that measures the water level.

2. A program for feedback control of a rotary filter device equipped with an endless strip filter that is movable by the rotation of a rotor, The aforementioned feedback control is PI control or PID control, As the parameter set for the feedback control, a first parameter set and a second parameter set, which is a parameter set in which the contribution of proportional operation is greater than that of the first parameter set, are set in advance. When executed by a computer, A determination function that determines whether each of the conditions expressed by the following equations (1) and (2) is met, When the determination function determines that at least one of the conditions represented by the following equations (1) and (2) is not met, a first control function performs feedback control using the first parameter set, A program that implements a second control function that performs feedback control using the second parameter set when the determination function determines that the conditions expressed by the following equations (1) and (2) are simultaneously met. L(t) > a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge that measures the water level.

3. A filter system comprising: a rotary filter device provided with an endless strip filter that is movable by the rotation of a rotor; and a control device that performs feedback control of the rotary filter device, The aforementioned feedback control is PI control or PID control, The control device is pre-configured with a first parameter set and a second parameter set, which is a parameter set whose contribution to proportional operation is greater than that of the first parameter set, as the parameter sets for the feedback control. The control device, If at least one of the conditions expressed by the following equations (1) and (2) is not met, feedback control using the first parameter set is performed. A filter system configured to perform feedback control using the second set of parameters when the conditions expressed by equations (1) and (2) below are simultaneously satisfied. L(t) > a (1) L(t)-L(t-Δt)>b (2) In the formula, L(t) is the water level on the primary side of the endless strip filter at a certain time t, Δt is a predetermined unit period relating to the period for determining the parameter set to be used, a is a predetermined threshold determined based on the configuration of the rotary filter device, and b is a predetermined threshold determined based on the capacity of the water level gauge that measures the water level.

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