TWI767693B - Fluid machinery and control method thereof - Google Patents

Abstract

A control method for fluid machinery is provided. The control method of fluid machinery includes: detecting a system pressure of the fluid machine, and calculating the pressure change rate in first time interval to obtain a previous pressure change rate and a current pressure change rate in sequence; filtering processing according to length of the first time interval, the previous pressure change rate and an updated previous pressure change rate, and updating the current pressure change rate with the processing result of the filtering processing to generate an updated current pressure change rate; and determining whether to perform a loading action or an unloading action according to the updated current pressure change rate. The updated previous pressure change rate is generated through the previous execution of the filtering process. In addition, corresponding fluid machinery is provided.

Description

Fluid machinery and its control method

The present invention relates to a control method of a fluid machine, and more particularly, to a control method of a fluid machine that determines the timing of loading or unloading according to the pressure change rate after filtering.

Air compressor refers to a machine used to compress air to increase gas pressure, which can provide power for various tools, transportation equipment, lifting equipment and snatch equipment. Therefore, air compressors are widely used in machinery manufacturing, metallurgy, shipbuilding, electronics, chemicals, oil and gas and other fields.

The air pressure in the air compressor cavity is expected to be maintained within a desired pressure band. Generally speaking, when it is detected that the system pressure of the air compressor rises and touches the upper limit of the expected pressure band, the control unit of the air compressor will control the motor and the intake valve to close to make the system pressure drop. On the contrary, when the system pressure of the air compressor is detected to drop and reach the lower limit of the expected pressure band, the control unit of the air compressor will control the motor and the intake valve to start, so as to pull the system pressure up. However, for safety reasons, there is a delay time interval between the motor overpower and the opening of the intake valve. That is to say, although the motor will run during the aforementioned delay time interval, the system pressure will continue to drop and exceed the lower limit of the expected pressure band because the intake valve has not been opened. And this is a situation that people in the industry are not happy with.

Therefore, a solution is needed to precisely control the closing timing of the motor and the intake valve to avoid the system pressure from exceeding the expected pressure band.

The invention provides a fluid machine and a control method thereof, which can precisely control the closing timing of the actuator.

The control method of the fluid machine of the present invention is suitable for an air compression device. The control method of the fluid machine includes: detecting the system pressure of the fluid machine, and calculating the pressure change rate in the first time interval, so as to obtain the previous pressure change rate and the current pressure change rate in sequence; The pressure change rate and the updated previous pressure change rate are filtered, and the current pressure change rate is updated according to the processing result of the filtering process to generate the updated current pressure change rate; and according to the updated current pressure change rate, it is determined whether to perform a loading action or unloading action. Wherein, the previous pressure change rate after the update is generated by performing the filtering process in the previous time.

The fluid machine of the present invention includes at least one compression device and a control circuit. The compression device includes an actuator. The actuator is driven to cause the compression device to pressurize the fluid. The control circuit is used to receive the detected pressure value of the system pressure of the fluid, and calculate the pressure change rate in the first time interval according to the pressure value, so as to obtain the previous pressure change rate and the current pressure change rate in sequence. The control circuit is further configured to perform filtering processing according to the length of the first time interval, the previous pressure change rate and the updated previous pressure change rate, and update the current pressure change rate with the processing result of the filtering process to generate the updated current pressure change rate. Wherein, the previous pressure change rate after the update is generated by performing the filtering process in the previous time. The control circuit also decides whether to restart or shut down the actuator of the fluid machine to perform the loading action or the unloading action according to the updated current pressure change rate.

Based on the above, the present invention can determine the restarting and closing timing of the actuator through the updated current pressure change rate. Therefore, the present invention can turn off/restart the actuator for unloading or loading before the pressure value touches the upper/lower limit value of the expected pressure band, so as to avoid the occurrence of higher/lower than expected upper/lower pressure values of the pressure band. problem with the lower limit. The degree of fluctuation of the pressure value controlled with the present invention is small.

FIG. 1A is a schematic structural diagram of a fluid machine according to an embodiment of the present invention. Referring to FIG. 1A , the fluid machine 100 includes a compression device 110 , a flow control circuit 120 and a control circuit 150 . The compression device 110 includes an actuator and a moving member (not shown) coupled with each other. The actuator can be driven according to the control signal to drive the moving element, thereby pressurizing the fluid in the cavity to generate the pressurized fluid 101 . It should be noted that FIG. 1A includes an omission mark (pointed by the arrow of the pressurized fluid 101 ) commonly used in the field of the present invention, which is used to omit the moving element to discharge the pressurized fluid 101 until the pressurized fluid 101 is collected by the pressure sensor 140 Measure all piping and equipment between pressures. An input valve (not shown) opens after the aforementioned loading action has been performed to deliver fluid into the cavity. The flow control circuit 120 influences the compression device 110 to start or stop air supply according to the control signal generated by the control circuit 150 . The output port 130 is used to output pressurized fluid to provide power for other devices. In this embodiment, the fluid machine 100 may be an air compression device, wherein the fluid is air, the input valve is an intake valve, and the output port 130 is an exhaust port. The pressure sensor 140 is used to continuously detect the pressure of the pressurized fluid 101 in the cavity (hereinafter referred to as the system pressure). The control circuit 150 is coupled to the pressure sensor 140 to obtain a measurement of the system pressure from the pressure sensor 140 .

FIG. 1B is a schematic structural diagram of a fluid machine according to another embodiment of the present invention. The function of each element shown in FIG. 1B can be referred to the description of the element with the same name in FIG. 1A , which will not be repeated here. The difference between FIG. 1B and FIG. 1A is only in the scope of the fluid machine 100 locks. The fluid machine 100 of FIG. 1A includes a compression device 110 , a flow control circuit 120 and a control circuit 150 , and the fluid machine 100 of FIG. 1A further includes a pressure sensor 140 . Moreover, both the fluid machine 100 shown in FIG. 1A and the fluid machine 100 shown in FIG. 1B can be regarded as a controlled body in the control method of the fluid machine of the present invention. It should be noted that, the descriptions for the subsequent drawings can be applied to the embodiment shown in FIG. 1A and the embodiment shown in FIG. 1B at the same time. The function of the control circuit 150 will be described in more detail below with reference to FIG. 2 .

FIG. 2 is a flow chart showing the steps of the control method of the fluid machine of the present invention. Please refer to Figure 1A, 1B and Figure 2 at the same time. The pressure sensor 140 is coupled to the compression device 110 . In step S210, the pressure sensor 140 is used to continuously detect the system pressure. The present invention does not limit the installation position of the pressure sensor 140 . In one embodiment, the pressure sensor 140 may be disposed at the exhaust port, so that the pressurized fluid 101 discharged from the fluid machine 100 can be measured by the pressure sensor 140 after passing through the exhaust port. In another embodiment, the pressurized fluid 101 discharged from the fluid machine 100 may be measured by the pressure sensor 140 after passing through a pipeline, an air bucket, a filter, a dryer and other equipment. That is, the pressure sensor 140 may be provided at any position, including inside and outside the air compressor. The control circuit 150 is coupled to the pressure sensor 140 . The control circuit 150 samples the pressure sensor 140 at intervals of a first time interval to obtain a plurality of pressure values. The length of the aforementioned first time interval can be adjusted by the designer according to actual needs.

In step S210, the control circuit 150 is further configured to calculate the pressure change rate in the first time interval according to the plurality of pressure values. For example, when the control circuit 150 receives the first pressure value, the second pressure value and the third pressure value (assuming the current pressure value) in sequence, the control circuit 150 can use the second pressure value and the third pressure value according to Calculate the pressure change rate in the first time interval as the current pressure change rate. Before this, the storage circuit (not shown) of the fluid machine 100 has stored the previous pressure change rate calculated previously, wherein the previous pressure change rate is calculated according to the first pressure value and the second pressure value.

In step S220, the control circuit 150 is used to control the filter (not shown) of the fluid machine 100, so that the filter is based on the cutoff frequency, the length of the first time interval, the previous pressure change rate and the updated previous pressure change rate filter processing. The control circuit 150 updates the current pressure change rate with the processing result of the filtering process to generate the updated current pressure change rate. Wherein, the previous pressure change rate after the update is generated by performing the filtering process in the previous time. The detailed steps of the filtering process will be described later, so it will not be described here for the time being. In step S230, the control circuit 150 further determines whether to restart/close the actuator (eg motor) of the fluid machine 100 and the opening/closing timing of the intake valve to perform the loading/unloading action according to the updated current pressure change rate. It should be noted that "loading" in the present invention may be defined as causing the fluid machine to output pressurized fluid, and "unloading" may be defined as causing the fluid machine to stop outputting pressurized fluid. In addition, unlike screw air compressors, scroll air compressors mostly do not have an intake valve. Therefore, when the present invention is applied to a model without an intake valve (eg, a scroll air compressor), the loading/unloading action can only be performed by restarting/shutting down the actuator (eg, motor) of the fluid machine 100 .

In short, the present invention can determine the restart/close timing of the actuator through the updated current pressure change rate. Since the updated current pressure change rate is calculated based on the past previous pressure change rate, when the current pressure value changes greatly compared to the previous pressure value due to noise interference, such as Reflected in the updated current rate of pressure change. Often, the pressure value needs to be controlled at a fixed value, and the pressure value controlled in the manner of the present invention has the advantage of less fluctuation. Various embodiments of the fluid machine control method of the present invention will be proposed below.

），並將前述差值除以第一時間區間的長度（記做

），以得到當前壓力變化率（記做

；R=

）。 3A is a flow chart showing the steps of a control method of a fluid machine according to an embodiment of the present invention, which is applicable to an air compression device. 1A, 1B and FIG. 3A at the same time, the process starts at step S310. Step S320 selects to execute step S330 or step S340 according to whether the control function is activated (ie, whether the control circuit 150 is activated). When the control function is not activated, the flow ends (step S330 ). When the control function is activated, the process proceeds to step S340. In step S340, the current pressure change rate is calculated by the control circuit 150. For example, the control circuit 150 calculates the difference between the aforementioned second pressure value and the third pressure value (the current pressure value) (denoted as

), and divide the aforementioned difference by the length of the first time interval (denoted as

) to get the current rate of pressure change (recorded as

;R=

).

Next, in step S350 , the control circuit 150 performs filtering processing to obtain the updated current pressure change rate (referred to as Rs). As mentioned above, the updated current pressure change rate Rs is calculated based on the previous pressure change rate. On the premise that the controlled body (including the air supply system of one or more air compressors) is allowed to perform the loading action and the current pressure change rate Rs after the update is less than 0 (step S360 ), the control circuit 150 calculates that the pressure threshold is reached (the lower limit of the expected pressure band) the remaining time (denoted as Tr1; Tr1=(P _load ) _­ -P)/Rs) (step S370). Otherwise, go back to step S320. It should be noted that, after the update, the current pressure change rate Rs is less than 0, indicating that the change trend of the system pressure is downward. In addition, excluding the situation that the controlled body (such as one or more air compressors) has been loaded, failed or implemented protective measures, the rest are the so-called allowable loading.

In step S370 , specifically, the control circuit 150 divides the value obtained by subtracting the current pressure value (denoted as P) from the pressure threshold value (denoted as P _load ) by the updated current pressure change rate Rs. In this way, a value corresponding to the remaining time (denoted as Tr1 ) until the system pressure reaches the pressure threshold P _load can be obtained. Finally, the control circuit 150 compares the length of the remaining time Tr1 with the length of the second time interval (denoted as Th1 ) through, for example, a comparison circuit (step S380 ). When the comparison result shows that the length of the remaining time Tr1 is less than or equal to the length of the second time interval Th1, the control circuit 150 sends a control signal to the actuator to perform the loading action (step S390). Otherwise, go back to step S320.

3B is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention, which is applicable to an air compression device. Steps S310 to S350 in FIG. 3B are the same as steps S310 to S350 in FIG. 3A , and thus will not be described again. The difference between FIG. 3B and FIG. 3A is only in the steps after step S350.

1A, 1B and 3B at the same time, under the premise that the controlled body is allowed to perform the unloading action and the current pressure change rate Rs after the update is greater than 0 (step S361), the control circuit 150 calculates that the pressure threshold (expected pressure is reached) The remaining time of the upper limit of the belt) (denoted as Tr2; Tr2=(P _{unload ­} -P)/Rs) (step S371). Otherwise, go back to step S320. It should be noted that, after the update, the current pressure change rate Rs is greater than 0, indicating that the change trend of the system pressure is upward. In addition, excluding the situation that the controlled body (such as one or more air compressors) has been unloaded, malfunctioned or implemented protective measures, the rest are the so-called situations that allow unloading.

In step S371 , specifically, the control circuit 150 divides the value obtained by subtracting the current pressure value (denoted as P) from the pressure threshold value (denoted as P _unload ) by the updated current pressure change rate Rs. In this way, a value corresponding to the remaining time (denoted as Tr2) until the system pressure reaches the pressure threshold P _unload can be obtained. Finally, the control circuit 150 compares the length of the remaining time Tr2 with the length of the third time interval (denoted as Th2) through, for example, a comparison circuit (step S381). When the comparison result shows that the length of the remaining time Tr2 is less than or equal to the length of the third time interval Th2, the control circuit 150 sends a control signal to the actuator to execute the unloading action (step S391). During the unloading action, the motor or intake valve is closed. Otherwise, go back to step S320. The length of the third time interval Th2 may be the same as the length of the second time interval Th1. However, the present invention is not limited to this, and in other embodiments, the length of the third time interval Th2 may also be different from the length of the second time interval Th1.

It should be noted that, when the present invention is actually implemented, step S360 and step S361 may be considered simultaneously. Specifically, on the premise that the controlled body is allowed to be loaded and unloaded, the control circuit 150 executes different steps according to the updated trend of the current pressure change rate Rs (Rs is less than 0 or greater than 0). If the current pressure change rate Rs has a downward trend after the update (Rs is less than 0), steps S370 , S380 and S390 of FIG. 3A are executed. If the current pressure change rate Rs has an upward trend after the update (Rs is greater than 0), steps S371 , S381 and S391 of FIG. 3B are executed. In order to keep the drawing concise and to facilitate the description, the implementation steps of the upward/downward trend of the current pressure change rate Rs after the update are respectively drawn in FIGS. 3A and 3B . It can be known from step S320 in FIG. 3A and FIG. 3B that the aforementioned control function (ie, controlling loading or unloading) can be enabled or disabled.

4A is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention, which is applicable to an air compression device. The steps shown in FIG. 4A differ from the steps shown in FIG. 3A only in S470-S490. Since steps S410 to S460 are respectively similar to steps S310 to S360 of FIG. 3A , detailed descriptions are omitted. 1A, 1B and FIG. 4A at the same time, under the premise that the controlled body is allowed to be loaded and the current pressure change rate Rs after the update is less than 0 (step S460), the control circuit 150 predicts the pressure estimate after the second time interval Th1. The measured value (denoted as Pf1) (step S470).

Th1)。控制電路150通過例如比較電路來比較壓力估測值Pf1與壓力閾值P _load（步驟S480）。當比較結果顯示壓力估測值Pf1小於或等於壓力閾值P _load時，由控制電路150向致動器發送一控制信號以使其執行加載的動作（步驟S490）。反之則回到步驟S420。在本實施例中，第二時間區間Th1的長度為10秒。然而本發明不以此為限，在其他實施例中，第二時間區間Th1的長度也可以是5秒（或是其他數值）。 Regarding step S470, specifically, the control circuit 150 performs a product operation on the updated current pressure change rate Rs and the length of the second time interval Th1, and adds the operation result to the current pressure value (denoted as P) to obtain the pressure Estimated value Pf1(=P+Rs

Th1). The control circuit 150 compares the estimated pressure value Pf1 with the pressure threshold value P _load by, for example, a comparison circuit (step S480 ). When the comparison result shows that the estimated pressure value Pf1 is less than or equal to the pressure threshold value P _load , the control circuit 150 sends a control signal to the actuator to perform the loading action (step S490 ). Otherwise, go back to step S420. In this embodiment, the length of the second time interval Th1 is 10 seconds. However, the present invention is not limited to this, and in other embodiments, the length of the second time interval Th1 may also be 5 seconds (or other values).

FIG. 4B is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention, which is applicable to an air compression device. The steps shown in FIG. 4B differ from the steps shown in FIG. 3B only in S471 to S491. Since steps S410 to S450 and S461 are respectively similar to steps S310 to S350 and S361 of FIG. 3B , they will not be described again. 1A, 1B and 4B at the same time, under the premise that the controlled body is allowed to unload and the current pressure change rate Rs after the update is greater than 0 (step S461), the control circuit 150 predicts the pressure estimate after the third time interval Th2. The measured value (denoted as Pf2) (step S471).

Th2)。控制電路150通過例如比較電路來比較壓力估測值Pf2與壓力閾值P _unload（步驟S481）。當比較結果顯示壓力估測值Pf2大於或等於壓力閾值P _unload時，由控制電路150向致動器發送一控制信號以使其執行卸載的動作（步驟S491）。在執行卸載的動作時，致動器或進氣閥關閉。反之則回到步驟S420。其中，第三時間區間Th2的長度可與第二時間區間Th1的長度相同。然而本發明不以此為限，在其他實施例中，第三時間區間Th2的長度也可不同於第二時間區間Th1的長度。 Regarding step S471 , specifically, the control circuit 150 performs a product operation on the updated current pressure change rate Rs and the length of the third time interval Th2 , and adds the operation result to the current pressure value (P) to obtain a pressure estimate Value Pf2(=P+Rs

Th2). The control circuit 150 compares the estimated pressure value Pf2 with the pressure threshold value P _unload through, for example, a comparison circuit (step S481 ). When the comparison result shows that the estimated pressure value Pf2 is greater than or equal to the pressure threshold value P _unload , the control circuit 150 sends a control signal to the actuator to perform the unloading action (step S491 ). During the unloading action, the actuator or intake valve is closed. Otherwise, go back to step S420. The length of the third time interval Th2 may be the same as the length of the second time interval Th1. However, the present invention is not limited to this, and in other embodiments, the length of the third time interval Th2 may also be different from the length of the second time interval Th1.

Similarly, when actually implementing the present invention, step S460 and step S461 can be considered simultaneously. Specifically, on the premise that the controlled body is allowed to be loaded and unloaded, the control circuit 150 executes different steps according to the updated trend of the current pressure change rate Rs (Rs is less than 0 or greater than 0). If the current pressure change rate Rs has a downward trend after the update (Rs is less than 0), steps S470 , S480 and S490 in FIG. 4A are performed. If the current pressure change rate Rs has an upward trend after the update (Rs is greater than 0), steps S471 , S481 and S491 of FIG. 4B are executed. In order to keep the drawing concise and to facilitate the description, the implementation steps of the upward/downward trend of the current pressure change rate Rs after the update are respectively drawn in FIGS. 4A and 4B .

The above-mentioned embodiments provide different approaches under the same essence for the control method of the fluid machine. One is the time remaining to reach the pressure threshold as a comparison object. The other is to compare pressure estimates.

。在本實施例中，截止頻率f例如為10Hz。接著，由控制電路150依據截止頻率f與第一時間區間的長度

來計算係數K（步驟S504）。具體來說，控制電路150可以計算公式(1)以得到係數K。係數K被儲存起來。後面會用到的第一比例與第二比例是基於係數K來決定的。 K=exp(-2

f

)           公式(1) 其中f代表該截止頻率，ΔT代表該第一時間區間的長度，計算結果為該係數K。 FIG. 5 is a flowchart showing the steps of the filtering process of the present invention. 1A, 1B and FIG. 5 at the same time, the process starts at step S501. First, the control circuit 150 determines whether a coefficient (denoted as K) has been initialized (step S502). If yes, go to step S505 directly. If not, go to step S503. In step S503, the cut-off frequency of the filter (denoted as f) and the length of the first time interval are read in by the control circuit 150

. In this embodiment, the cutoff frequency f is, for example, 10 Hz. Next, according to the cutoff frequency f and the length of the first time interval, the control circuit 150

to calculate the coefficient K (step S504). Specifically, the control circuit 150 may calculate the formula (1) to obtain the coefficient K. The coefficient K is stored. The first ratio and the second ratio, which will be used later, are determined based on the coefficient K. K=exp(-2

f

) Formula (1) where f represents the cutoff frequency, ΔT represents the length of the first time interval, and the calculation result is the coefficient K.

In step S505 , the current pressure change rate R and the coefficient K are read in by the control circuit 150 . Next, the control circuit 150 determines whether the current pressure change rate Rs after the update is calculated for the first time (step S506 ). If yes, go to step S507. In step S507, the control circuit 150 directly regards the current pressure change rate R as the updated current pressure change rate Rs, and outputs the current pressure change rate R and the updated current pressure change rate Rs (step S508). Next, the updated current pressure change rate Rs and the current pressure change rate R are respectively stored by the control circuit 150 (referred to as the value Rs* and the value R*) (step S509 ). The above actions can also be regarded as the control circuit 150 replacing the initial value in one storage space with the updated current pressure change rate Rs, and replacing the initial value in another storage space with the current pressure change rate R. Then, the flow ends (step S510 ).

K + R*

(1-K))。如前面所述，第一比例與第二比例是基於係數K來決定的。在本實施例中，第一比例等於係數K，第二比例等於1減去係數K的值。接著，回到步驟S508，由控制電路150輸出當前壓力變化率R以及更新後當前壓力變化率Rs（步驟S508），並在更新值Rs*與R*（步驟S509）後，結束流程（步驟S510）。 When the judgment result of step S506 is no (not the first calculation and update of the current pressure change rate Rs), the values in the above two storage spaces are read (step S511 ), namely the value Rs* and the value R*. Next, the updated current pressure change rate Rs is calculated by the control circuit 150 according to the value Rs* and the value R* (step S512 ). It should be noted that at this time, the two storage spaces have pre-stored the results generated by the previous filtering operation. In step S512, the product of the first ratio K and the value Rs* is calculated by the control circuit 150, and the product of the second ratio (1-K) and the value R* is calculated. The control circuit 150 adds the above two product results to obtain the updated current pressure change rate Rs (=Rs*

K + R*

(1-K)). As described above, the first ratio and the second ratio are determined based on the coefficient K. In this embodiment, the first scale is equal to the coefficient K, and the second scale is equal to 1 minus the value of the coefficient K. Next, returning to step S508 , the control circuit 150 outputs the current pressure change rate R and the updated current pressure change rate Rs (step S508 ), and after updating the values Rs* and R* (step S509 ), the flow ends (step S510 ). ).

That is to say, when the control circuit 150 is performing the first calculation and the coefficient K has not been calculated, the control method of the present invention will execute steps S501 to S510 in sequence. At this time, the value Rs* and the value R* are updated with the current pressure change rate R as it is. When the control circuit 150 is performing the second calculation and the coefficient K has been calculated, steps S501 , S502 , S505 , S506 , S511 , S512 , S508 to S510 are executed in sequence. At this time, the value Rs* and the value R* used for the calculation in step S512 are the results stored after the first calculation. After the updated current pressure change rate Rs is output, the value R* is updated with the current pressure change rate R calculated for the second time (before the update), and the value Rs* is updated with the updated current pressure change rate Rs. Similarly, the value Rs* and the value R* used in the third calculation were also produced by the second calculation. The subsequent calculation process can be deduced in the same way.

It has been proved that the pressure value under the control of the present invention has the advantage of less fluctuation. In addition, the restart/close timing of the actuator is determined by the updated current pressure change rate, the present invention can make the actuator restart/close before the pressure value reaches the expected lower/upper limit value of the pressure band to load/unload. Therefore, it is possible to avoid the problem that the pressure value is smaller/larger than the lower/upper limit value of the expected pressure band. The results without and with the present invention will be compared graphically below.

FIG. 6 is a schematic diagram showing the change of pressure value with time. Please refer to FIG. 6 , the curve 601 and the curve 602 respectively represent the pressure change without using the present invention and using the present invention. It can be seen that when the curve 601 touches the lower limit value of the expected pressure band P, the control circuit that does not adopt the control method of the present invention will control the restart of the motor (time point t1 ). However, since the motor is idling for a delay time after restarting, the pressure value will continue to drop until the intake valve opens again after the delay time expires. As a result, the curve 601 will exceed the range of the expected pressure band P. Looking back at the curve 602, the control circuit using the control method of the present invention can estimate the remaining time for the pressure value to reach the lower limit value of the pressure band P, or by estimating whether the pressure value will be equal to or less than the second time interval Th1 The lower limit value of the pressure band P is used to advance the timing of restarting the motor to avoid the situation that the curve 602 exceeds the expected range of the pressure band P. In addition, when the curve 601 touches the upper limit value of the expected pressure band P, the control circuit that does not adopt the control method of the present invention will control the motor to turn off. Compared to this, the control circuit using the control method of the present invention can turn off the motor in advance to avoid the curve 602 from touching the upper limit value of the pressure band P.

FIG. 7 is a schematic diagram showing a curve diagram of the pressure change rate using the filtering process of the present invention and the pressure change rate without the filtering process. Referring to FIG. 7, curve 701 shows the unfiltered pressure change rate, and curve 702 shows the filtered pressure change rate. It can be seen from FIG. 7 that the curve 701 fluctuates greatly with time. Relatively speaking, the fluctuation of curve 702 over time is much smaller.

FIG. 8A shows the simulation result of the present invention for pressure. Referring to FIG. 8, curve 801 shows the unfiltered pressure change rate, and curve 802 shows the filtered pressure change rate. It can be seen from FIG. 8A that the fluctuation range of the curve 801 is aggravated by the delay time when the loading is performed, and even drops below the straight line 803 (the lower limit value of the pressure band). Relatively speaking, the curve 802 can still be maintained above the straight line 803 due to the earlier loading time point. The fluctuations of the two differ by about 0.25 bar at time t3. Therefore, the designer can move the target pressure down (for example, from 6.5 bar to 6.25 bar) and simultaneously move down the upper limit of the pressure band and the lower limit of the pressure band.

FIG. 8B shows the simulation result of the pressure after adjusting the working pressure. Referring to Figure 8B, the relevant parameters of the loading control corresponding to curve 802' It should be noted that, in FIG. 8B , although the curve 802 ′ is lower than the lower limit value of the expected pressure band at the time point t3 (see straight line 803 ), the lower limit value of the expected pressure band is higher than the customer’s specification. , so the curve 802 still does not touch the lower limit specified by the customer. In this way, after the work pressure is reduced, it is expected to save energy by 1% to 2% of the total.

The foregoing embodiments are only used to control a single fluid machine, but the present invention is not limited thereto. FIG. 9 is a schematic diagram showing the structure of the present invention applied to multiple fluid machines. Referring to FIG. 9 , the control circuit 150 can receive the sensed pressure value from the pressure sensor 140 , and control the controlled objects A1 and A2 to simultaneously pressurize the fluid 101 according to the sensed pressure value. FIG. 10 is another schematic structural diagram of the present invention applied to multiple fluid machines. Please refer to Figure 10, the control circuit is not independent as shown in Figure 9, but the controlled body A1_M shoulders the responsibility of the control circuit. The controlled object A1_M can receive the sensed pressure value from the pressure sensor 140, and control itself and A2_S to simultaneously pressurize and generate the fluid 101 according to the sensed pressure value. It should be noted that, in order to keep the drawings concise and facilitate the description, FIG. 9 and FIG. 10 only show two controlled objects, but this should not be a limitation of the present invention. In practical applications, the controlled body can be other quantities.

In summary, the present invention can determine the restart/close timing of the actuator through the updated current pressure change rate, and can restart the actuator before the pressure value reaches the expected lower/upper limit value of the pressure band /close for loading/unloading. Therefore, it is possible to avoid the problem that the pressure value is smaller/larger than the lower/upper limit value of the expected pressure band. In addition, compared to directly using the current pressure change rate, the present invention using the updated current pressure change rate as the estimation basis also has the advantage of having less fluctuation of the pressure change rate with time. Therefore, the probability of system malfunction is reduced. Further, since the loading or unloading action of the system is advanced by a time length equivalent to the second time interval (or the third time interval), the pressure fluctuation is small. In this way, the set working pressure can be further lowered to achieve the effect of energy saving.

100: Fluid Machinery 101: Fluid 110: Compression device 120: Flow control circuit 130: output port 140: Pressure sensor 150: Control circuit 601, 602, 701, 702, 801, 802, 802’: Curve 803: Straight A1, A1_M, A2, A2_S: the controlled body P: pressure belt S210~S230, S310~S391, S410~S491 S501~S512: Steps t1~t3: time point

FIG. 1A is a schematic structural diagram of a fluid machine according to an embodiment of the present invention. FIG. 1B is a schematic structural diagram of a fluid machine according to another embodiment of the present invention. FIG. 2 is a flow chart showing the steps of the control method of the fluid machine of the present invention. FIG. 3A is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention. FIG. 3B is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention. FIG. 4A is a flowchart showing the steps of a control method of a fluid machine according to an embodiment of the present invention. FIG. 4B is a flow chart showing the steps of a control method of a fluid machine according to an embodiment of the present invention. FIG. 5 is a flowchart showing the steps of the filtering process of the present invention. FIG. 6 is a schematic diagram showing the change of pressure value with time. FIG. 7 is a schematic diagram showing a curve diagram of the pressure change rate using the filtering process of the present invention and the pressure change rate without the filtering process. FIG. 8A shows the simulation result of the present invention for pressure. FIG. 8B shows the simulation result of the pressure after adjusting the working pressure. FIG. 9 is a schematic diagram showing the structure of the present invention applied to multiple fluid machines. FIG. 10 is another structural schematic diagram of the present invention applied to multiple fluid machines.

S210~S230: Steps

Claims (14)

A control method of a fluid machine, suitable for at least one air compression device, the control method of the fluid machine comprising: detecting a system pressure of the fluid machine, and calculating a first time interval (

) to obtain a previous pressure change rate (R*) and a current pressure change rate (R) in sequence; according to the length of the first time interval (

), the previous pressure change rate (R*) and an updated previous pressure change rate are subjected to a filtering process, and the current pressure change rate is updated with the processing result of the filtering process to generate an updated current pressure change rate (R→ Rs); and determine whether to perform a loading action or an unloading action according to the updated current pressure change rate (Rs), wherein the updated previous pressure change rate is generated by performing the filtering process last time. The control method for a fluid machine as claimed in claim 1, wherein the filtering step includes: comparing a cutoff frequency (f) and the length of the first time interval (

) performs an operation to generate a coefficient (K), and generates a first ratio (K) and a second ratio (1-K) according to the coefficient; the updated previous pressure change rate of the first ratio and the The previous pressure change rates of the second scale are summed to obtain the processing result of the filtering process. The control method of a fluid machine as claimed in claim 2, wherein the process of generating the coefficient comprises calculating: exp(-2

f

), where f represents the cutoff frequency, ΔT represents the length of the first time interval, and the calculation result is the coefficient, where the coefficient is used as the first ratio, and the sum of the first ratio and the second ratio is 1 . The control method for a fluid machine according to claim 1, wherein the step of determining whether to perform the loading action or the unloading action according to the updated current pressure change rate (Rs) comprises: When the current pressure change rate after the update indicates a downward trend of the system pressure (Rs<0), a value obtained by subtracting a current pressure value of the system pressure from a pressure threshold is divided by the current pressure change rate after the update , to obtain a remaining time for the system pressure to reach the pressure threshold; and When the length of the remaining time is less than or equal to the length of a second time interval (Th1), the loading action is performed. The control method for a fluid machine according to claim 1, wherein the step of determining whether to perform the loading action or the unloading action according to the updated current pressure change rate (Rs) comprises: When the current pressure change rate after the update indicates an upward trend of the system pressure (Rs>0), a value obtained by subtracting a current pressure value of the system pressure from a pressure threshold is divided by the current pressure change rate after the update , to obtain a remaining time for the system pressure to reach the pressure threshold; and When the length of the remaining time is less than or equal to the length of a third time interval (Th2), the unloading action is performed. The control method for a fluid machine according to claim 1, wherein the step of determining whether to perform the loading action or the unloading action according to the updated current pressure change rate (Rs) comprises: When the current pressure change rate after the update indicates a downward trend of the system pressure (Rs<0), a product operation is performed on the updated current pressure change rate (Rs) and the length of a second time interval (Th1), adding a current pressure value of the system pressure to the operation result to obtain an estimated pressure value; and The loading action is performed when the estimated pressure value is less than or equal to a pressure threshold. The control method for a fluid machine according to claim 1, wherein the step of determining whether to perform the loading action or the unloading action according to the updated current pressure change rate (Rs) comprises: When the current pressure change rate after the update indicates an upward trend of the system pressure (Rs>0), a product operation is performed on the updated current pressure change rate (Rs) and the length of a third time interval (Th2), adding a current pressure value of the system pressure to the operation result to obtain an estimated pressure value; and The unloading action is performed when the estimated pressure value is greater than or equal to a pressure threshold. A fluid machine, comprising: at least one compression device including an actuator driven to cause the at least one compression device to pressurize a fluid; and a control circuit for: receiving detected a pressure value of a system pressure of the fluid; calculating a pressure change rate in a first time interval according to the pressure value to obtain a previous pressure change rate (R*) and a current pressure change rate (R) in sequence ; and according to the length of the first time interval (

), the previous pressure change rate (R*), and an updated previous pressure change rate are subjected to a filtering process, and the current pressure change rate is updated with the processing result of the filtering process to generate an updated current pressure change rate, wherein the The previous pressure change rate after the update is generated by performing the filtering process last time; wherein, the control circuit determines whether to restart or close the actuator of the fluid machine according to the current pressure change rate after the update to perform a loading action or an unloading action action. The fluid machine as claimed in claim 8, wherein the control circuit is used for performing the filtering process, comprising: comparing a cutoff frequency (f) and the length of the first time interval (

) performs an operation to generate a coefficient (K), and generates a first ratio (K) and a second ratio (1-K) according to the coefficient; the updated previous pressure change rate of the first ratio and the The previous pressure change rates of the second scale are summed to obtain the processing result of the filtering process. The fluid machine of claim 9, wherein the control circuit is further configured to calculate: exp(-2

f

), where f represents the cutoff frequency, ΔT represents the length of the first time interval, and the calculation result is the coefficient, where the coefficient is used as the first ratio, and the sum of the first ratio and the second ratio is 1 . The fluid machine of claim 8, wherein the control circuit is further used to: When the current pressure change rate after the update indicates a downward trend of the system pressure (Rs<0), a value obtained by subtracting a current pressure value of the system pressure from a pressure threshold is divided by the current pressure change rate after the update , to obtain a remaining time for the system pressure to reach the pressure threshold; and When the length of the remaining time is less than or equal to the length of a second time interval (Th1), the actuator is controlled to restart to perform the loading action. The fluid machine of claim 8, wherein the control circuit is further used to: When the current pressure change rate after the update indicates an upward trend of the system pressure (Rs>0), a value obtained by subtracting a current pressure value of the system pressure from a pressure threshold is divided by the current pressure change rate after the update , to obtain a remaining time for the system pressure to reach the pressure threshold; and When the length of the remaining time is less than or equal to the length of a third time interval (Th2), the actuator is controlled to be turned off to perform the unloading action. The fluid machine of claim 8, wherein the control circuit is further used to: When the current pressure change rate after the update indicates a downward trend of the system pressure (Rs<0), a product operation is performed on the updated current pressure change rate (Rs) and the length of a second time interval (Th1), adding a current pressure value of the system pressure to the operation result to obtain an estimated pressure value; and When the estimated pressure value is less than or equal to a pressure threshold, the actuator is controlled to restart to perform the loading action. The fluid machine of claim 8, wherein the control circuit is further used to: When the current pressure change rate after the update indicates an upward trend of the system pressure (Rs>0), a product operation is performed on the updated current pressure change rate (Rs) and the length of a third time interval (Th2), adding a current pressure value of the system pressure to the operation result to obtain an estimated pressure value; and When the estimated pressure value is greater than or equal to a pressure threshold, the actuator is controlled to be closed to perform the unloading action.

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