Control device

Abstract

To provide a control device that constantly monitors an operation amount and expands a limit width including a cut portion of the operation amount.SOLUTION: The control device is provided with a first integral operation unit based on a deviation, a first addition unit for adding an output of the first integral operation unit and an inversion of a detected value, a proportional operation unit for calculating a proportional operation amount based on an output of the first addition unit, a differential operation unit for calculating a differential operation amount based on a detected value, a second addition unit for adding an output of the first addition unit and an inversion of an output of the differential operation unit, a first output limiter for limiting an output of the second addition unit, a switching unit for setting a turn-on state when the output of the first output limiter is not saturated, a second output limiter for limiting output to a value in an expanded limit width, and a second integral operation unit for expanding the limit width based on the deviation. The switching unit feeds back a value obtained by subtracting the output of the second output limiter from the output of the proportional operation unit to the first integral operation unit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for adjusting a physical quantity such as temperature to an optimum value, as typified by the temperature control of a molding machine, and in particular to a control device for solving the saturation problem in PID control. [Background technology]

[0002] 2. Description of the Related Art Conventionally, control of various physical quantities has been widely carried out in a variety of fields, as typified by temperature control using PID (Proportional-Integral-Differential Controller) control.

[0003] For example, Fig. 1 is an example of a block diagram showing the control flow in a conventional temperature adjustment unit. Fig. 1 shows a block diagram of automatic matching PID control, and the manipulated variable MV lim When saturated, the PID control output MV always matches its saturated value, i.e., the actual manipulated variable. Therefore, the so-called windup phenomenon does not occur. However, since the differential manipulated variable is also fed back as integral feedback, the unreflected manipulated variable cannot be corrected by integral action.

[0004] Therefore, Patent Document 1 discloses a temperature control device that reliably makes the temperature, which is a physical quantity, reach a set value by using a two-stage output limiter and widening the range from the lower limit to the upper limit. Figure 2 is an example of a block diagram showing the control flow in the temperature control device disclosed in Patent Document 2.

[0005] Figure 2 shows a block diagram of automatic matching PI control. By not including a differential manipulated variable and by performing feedback to the integral, the differential manipulated variable limited by the final output value can be compensated for by the integral manipulated variable, ensuring that the physical quantity reaches the set value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-203459 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, it depends on the limit width on the integral feedback side. That is, the limit width is set in advance (±10% in Patent Document 1), and since the differential manipulated variable has a differential gain, there remains a problem that there is a risk that the limit width may be exceeded and saturation may occur in many cases.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a control device that constantly monitors an operation amount and expands the limit width by including the amount of the operation amount being cut. [Means for solving the problem]

[0009] In order to achieve the above object, a control device according to the present invention includes a first integral calculation unit based on a deviation which is a value obtained by subtracting a detected value of a physical quantity from a set value of the physical quantity, a first adder unit that adds an output from the first integral calculation unit and an inversion of the detected value, a proportional calculation unit that calculates a proportional manipulated variable based on the output of the first adder unit, a differential calculation unit that calculates a differential manipulated variable based on the detected value, a second adder unit that adds an output from the first adder unit and an inversion of the output from the differential calculation unit, a first output limiter that limits the output from the second adder unit to between a first upper limit value and a first lower limit value, a switch unit that is turned on when the output of the first output limiter is not saturated, and a switch unit that extends the range between the first upper limit value and the first lower limit value. a second output limiter that limits an output between a second upper limit value and a second lower limit value that are extended from the first upper limit value and the second lower limit value; a second integral calculation unit that extends the second upper limit value and the second lower limit value and is based on a deviation that is a value obtained by subtracting the detection value from the set value; and a path that, when the switch unit is in an on state, inputs the output from the second integral calculation unit to the second output limiter and feeds back a value obtained by subtracting the output from the second output limiter from the output from the proportional calculation unit to the first integral calculation unit, wherein the proportional calculation unit includes a first gain setting unit having 100 / PB, the differential calculation unit includes a differentiator and a second gain setting unit having Td×(100 / PB), and the first integral calculation unit includes an integrator and a gain setting unit having (1 / T I a third gain setting unit having a second integral calculation unit including an integrator and (100 / PB)×(1 / T I )×(1 / 10) and a fourth gain setting unit having a fourth gain setting unit having a fourth output limiter, and the output from the first output limiter is output to a controlled object as a manipulated variable for controlling a physical quantity. I and Td represent the proportional band, integral time, and derivative time, respectively.

[0010] In addition, in the control device according to the present invention, the switch unit is outputa control amount determining unit that determines whether a second control amount output from the limiter is within a predetermined range above and below the first control amount output from the second adding unit, and when the control amount determining unit determines that the second control amount is within a predetermined range above and below the first control amount, the second integral calculation unit is set to the second integral calculation unit. output Preferably connected to a limiter. [Effects of the Invention]

[0011] According to the above invention, a switch unit is provided that inputs the output of the second integral calculation unit to the second limiter when the difference between the input and output to the first limiter converges within a predetermined range. Therefore, even if the detection value PV of the controlled object (e.g., the heating unit) does not reach the set value SV, the limit width can be expanded to ensure that it reaches the set value SV, thereby eliminating the offset. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram illustrating a control flow in a conventional temperature adjustment unit. [Figure 2] FIG. 1 is an exemplary block diagram showing a control flow in the temperature control device disclosed in Patent Document 2. [Figure 3] FIG. 1 is an example diagram of a block diagram equivalent to a PID calculation unit of a conventional control device. [Figure 4] FIG. 2 is an example of a block diagram equivalent to a PID calculation unit of the control device according to the embodiment of the present invention. [Figure 5] 1 is a schematic diagram showing a configuration of an injection molding machine to which a control device according to an embodiment of the present invention is applied; [Figure 6] 10 is a graph showing the relationship between the manipulated variable output to a heating unit and the detected temperature (detected value) in an injection molding machine M using a conventional control device. [Figure 7] 1 is a graph showing the relationship between the manipulated variable output to a heating unit and the detected temperature (detected value) in an injection molding machine M using a control device according to an embodiment of the present invention. [Figure 8]10 is a graph showing the relationship between the operation amount output to the heating section and the added amount of the limit width during actual molding in an injection molding machine using a control device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes in detail a control device according to an embodiment of the present invention with reference to the drawings. The following embodiments do not limit the invention described in the claims, and it goes without saying that not all of the combinations of the characteristics described in the embodiments are essential to the solution.

[0014] Furthermore, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments. The same elements are denoted by the same reference numerals throughout the embodiments.

[0015] According to an embodiment of the present invention, a switch unit is provided that inputs the output of the second integral calculation unit to the second limiter when the difference between the input and output to the first limiter converges within a predetermined range. Therefore, even if the detection value PV of the controlled object (e.g., the heating unit) does not reach the set value SV, the limit width can be expanded to ensure that it reaches the set value SV, thereby eliminating the offset.

[0016] Fig. 3 is an example of a block diagram equivalent to the PID calculation unit 11 of the conventional control device 1. Fig. 3 is essentially a modified representation of Fig. 2. As shown in Fig. 3, the PID calculation unit 11 of the control device 1 includes an integral calculation unit 111, a proportional calculation unit 112, a differential calculation unit 113, a first adder 114, a first output limiter 115, a path 116, a second adder 117, and a second output limiter 118.

[0017] The integral calculation unit 111 calculates an integral manipulated variable based on a deviation e, which is a value obtained by subtracting the detected value PV from the set value SV. The proportional calculation unit 112 calculates a proportional manipulated variable based on the detected value PV. The first adder 114 adds the output from the integral calculation unit 111 and the inverse of the output from the proportional calculation unit 112.

[0018] The first output limiter 115 is a first output limiter that limits the output from the first adder 114 (the manipulated variable MV PI ) between a first upper limit value and a first lower limit value. PI ) to the output from the first output limiter 115 (the manipulated variable MV PIlim ) is fed back to the integral calculation unit 111.

[0019] The differential operation unit 113 calculates a differential operation amount based on the detected value PV. The second adder 117 adds the output from the first adder 114 and the inverse of the output from the differential operation unit 113. The second output limiter 118 calculates the operation amount MV of the output from the second adder 117 (proportional operation amount, integral operation amount, and differential operation amount). PID ) is limited to a value between a second upper limit value (<first upper limit value) and a second lower limit value (>first lower limit value). The output from the second output limiter 118 (the manipulated variables MV PIDlim ) is output to the controlled object 20 as a manipulated variable.

[0020] In FIG. 3, the integral calculation unit 111 includes an integrator and a (1 / T I )×(100 / PB). Proportional calculation unit 112 includes a gain setting unit having 100 / PB. Path 116 includes a gain setting unit having PB / 100, and more specifically, the subtracted value (manipulated variable MV PI -Manipulated amount MV PIlim ) to the integration calculation unit 111. I and T d are the proportional band, integral time (seconds), and derivative time (seconds), respectively.

[0021] 3, the first upper limit value and the first lower limit value of the first output limiter 115 are 110(%) and -10(%), respectively. The second upper limit value and the second lower limit value of the second output limiter 118 are 100(%) and 0(%), respectively. The second upper limit value and the second lower limit value respectively represent the physical limits of the on / off operation of the controlled object 20. For example, if the controlled object 20 is a heater, it is controlled in a time-proportional manner, and the upper limit value (second upper limit value), which is the physical limit, means that the heater is always on for 100(%) of the time and the heater is always off for 0(%) of the time (no current flows).

[0022] 3, the first output limiter 115 is incorporated inside the second output limiter 118 so that the detected value PV can reach the set value SV even when the I-PD calculation result (PID output) is limited by the output limiter. The output range of the first output limiter 115 is set larger than the output range of the second output limiter 118.

[0023] Setting the output range of second output limiter 118 inside the output range of first output limiter 115 produces the same effect as extending the first upper limit value and first lower limit value of first output limiter 115 to the second upper limit value and second lower limit value of second output limiter 115. Therefore, it becomes possible to make detection value PV reach set value SV.

[0024] However, in the PID calculation unit 11 of the conventional control device 1 shown in Fig. 3, the second upper limit value and second lower limit value of the second output limiter 115 are fixed, and if the detected value PV is outside the range determined by the second upper limit value and second lower limit value, it is not guaranteed that the detected value PV will reach the set value SV. Therefore, in this embodiment, the second upper limit value and second lower limit value of the second output limiter 115 are changed depending on the magnitude of the detected value PV, thereby ensuring that the detected value PV will reach the set value SV.

[0025] 4 is an exemplary block diagram equivalent to the PID calculation unit 7 of the control device 10 according to the embodiment of the present invention. The configuration example is shown. As shown in FIG. 4, the PID calculation unit 7 of the control device 10 includes a first integral calculation unit 71, a first addition unit 72, a coefficient switching unit 73, a proportional calculation unit 74, a second addition unit 75, a differential calculation unit 76, a first output limiter 77, a switch unit 78, a second output limiter 79, a path 80, and a second integral calculation unit 81.

[0026] The first integral calculation unit 71 calculates an integral manipulated variable based on a deviation e, which is a value obtained by subtracting the detected value PV from the set value SV. The first addition unit 72 adds the output from the first integral calculation unit 71 to the inverse of the detected value PV.

[0027] The first adding unit 72 switches whether or not to add the set value SV depending on the switching coefficient CP in the coefficient switching unit 73. The switching coefficient CP is switched to 0 (zero) or 1 depending on the type of the controlled object 20.

[0028] The proportional calculation unit 74 calculates the manipulated variable (proportional manipulated variable+integral manipulated variable) MV based on the output of the first adder 72. PI The differential calculation unit 76 calculates a differential manipulated variable based on the detected value PV. The second adder 75 adds the output from the first adder 72 and the inverted output from the differential calculation unit 76. The second adder 75 calculates the output from the proportional calculation unit 74 (the manipulated variable MV PI ) and the inversion of the output of the differential calculation unit 76 based on the detected value PV.

[0029] The first output limiter 77 is a first output limiter that limits the output from the second adder 75 (the proportional manipulated variable, the integral manipulated variable, and the differential manipulated variable MV PID ) is limited between the first upper limit value and the first lower limit value to obtain the manipulated variable MV PIDlim In FIG. 2, the first upper limit value is set to 100(%) and the first lower limit value is set to 0(%). The calculated manipulated variable MV PIDlim is input to the controlled object 20, the detected value PV can be obtained.

[0030] The switch unit 78 is configured to receive the output (operation amount MV PIDlim ) and the output from the second adder 75 (the manipulated variable MV PID ) is within a predetermined range, the input to the second output limiter 79 is switched.

[0031] Specifically, the output from the first output limiter 77 (the manipulated variable MV PIDlim ) and the output from the second adder 75 (the manipulated variable MV PID ) is within a predetermined range, that is, when it is considered that the two are consistent, the manipulated variable is not saturated, so the switch unit 78 is turned on and the limit width is adjusted. Conversely, when the output from the first output limiter 77 (the manipulated variable MV PIDlim ) and the output from the second adder 75 (the manipulated variable MV PID ) exceeds a predetermined range, the amount of operation is saturated, so the switch unit 78 is turned off and the limit width is not adjusted.

[0032] When the switch unit 78 is turned on, the second integral calculator 81 calculates an integral manipulated variable (manipulated variable MV) based on the deviation e, which is the value obtained by subtracting the detected value PV from the set value SV. PIlim ) is calculated. In other words, when a deviation e occurs, the second upper limit value X_H and the second lower limit value X_L of the second output limiter 79 are changed to adjust the limit width. Specifically, the second output limiter 79 calculates the manipulated variable MV PIlim The second upper limit value X_H and the second lower limit value X_L are expanded so that the manipulated variable MV PIlim Output.

[0033] Output operation amount MV PIlim and the output from the proportional calculation unit 74 (operating amount MV PI) is added together, converted into a physical quantity of the set value via path 80, and the inverted value is fed back. That is, the deviation e, which is a value obtained by subtracting the detected value PV from the set value SV, is added to the inverted value fed back to recalculate the deviation e, and input it to the first integral calculation unit 71 and the second integral calculation unit 81. This makes it possible to calculate the manipulated variable with the limiter width of the output limiter expanded.

[0034] Thereafter, the above-described process is repeated based on the recalculated deviation e, and the output from the first output limiter 77 (the manipulated variable MV PIDlim ) and the output from the second adder 75 (the manipulated variable MV PID ) exceeds a predetermined range, that is, reaches a saturated state, the detected value PV reaches the set value SV.

[0035] In FIG. 4, the first integral calculation unit 71 includes an integrator and a (1 / T I The proportional calculation unit 74 includes a gain setting unit having 100 / PB. The second integral calculation unit 81 includes an integrator and a gain setting unit having (100 / PB)×(1 / T I Path 80 includes a gain setting having PB / 100, where PB, T I and Td mean proportional band, integral time (seconds), and derivative time (seconds), respectively.

[0036] In the PID control system shown in FIG. 4, the following arithmetic expression is established. First, the output from the second adder 75 (the manipulated variable MV PID ) is the output from the first output limiter 77 (operating amount MV PIDlim ), the output from the second adder 75 (the manipulated variable MV PID ) is calculated.

[0037]

number

[0038] Here, n is a natural number, and the calculation is repeated until the detected value PV reaches the set value SV. n is the detected value at the time of this sampling, and the detected value PV n-1 is the detected value at the time of the previous sampling. Next, the output from the first output limiter 77 (the manipulated variable MV PIDlim ) and the output from the second adder 75 (the manipulated variable MV PID ) is within a predetermined range, i.e., is approximately equal to the output (operation amount MV PID ) is calculated.

[0039]

number

[0040] Then, the output from the first output limiter 77 (the manipulated variable MV PIDlim ) is the output from the second adder 75 (the manipulated variable MV PID ), the output from the second adder 75 (the manipulated variable MV PID ) is calculated.

[0041]

number

[0042] Fig. 5 is a schematic diagram showing the configuration of an injection molding machine to which a control device 10 according to an embodiment of the present invention is applied. In Fig. 5, the control device 10 according to this embodiment is applied to an injection molding machine M to perform temperature control. The injection molding machine M shown in Fig. 5 includes an injection unit Mi and a mold clamping unit Mc.

[0043] The injection unit Mi shown in Fig. 5 includes a heating barrel as a heating unit for heating the resin material. In the example of Fig. 5, the heating barrel has a front portion 3a, a middle portion 3b, and a rear portion 3c, and an injection nozzle 21 is provided at the front end of the heating barrel, and a hopper 22 (material supply unit) for supplying the resin material is provided at the rear end. The configuration of the mold clamping unit Mc is well known to those skilled in the art, so a description thereof will be omitted.

[0044] As shown in Fig. 5, a screw 2 is inserted inside the heating barrel. A screw drive unit 23 is connected to the rear end of the screw 2, extending rearward from the material supply unit 22 to drive the screw 2 to rotate and move forward and backward. The configuration of the screw drive unit 23 is well known to those skilled in the art, so a description thereof will be omitted.

[0045] Three heating elements (heaters, etc.) 4a, 4b, and 4c that make up the heating section are attached to the outside of the heating barrel. Three temperature sensors 6a, 6b, and 6c are provided in the heating barrel (front section 3a, middle section 3b, and rear section 3c) to detect the temperature after heating. Solid pellets (resin material) supplied from a hopper 22 to the inside of the heating barrel are plasticized and kneaded by shearing due to the rotation of the screw 2 and heating by the heating barrel, producing molten resin to be injected and filled into the mold of the mold clamping unit Mc.

[0046] The control device 10 shown in Figure 5 controls the overall operation of the injection molding machine M, and controls not only the temperature but also the operation of the entire injection molding machine M, such as the screw drive unit 23 and the mold clamping device Mc.

[0047] Using the injection molding machine M shown in FIG. 5, the control device 10 (PID calculation unit 7) according to this embodiment is used to calculate the proportional manipulated variable, the integral manipulated variable, and the differential manipulated variable MV PIDlim 6 is a graph showing the relationship between the manipulated variable output to the heating unit and the detected temperature (detected value) in an injection molding machine M using a conventional control device 1.

[0048] 6, it can be seen that the integral manipulated variable 602 converges without exceeding a certain value relative to the manipulated variable 601 that controls the heating unit. Therefore, even though the detected temperature 603 has not yet reached the set temperature 604, the integral manipulated variable 602 cannot be increased, and so the detected temperature 603 converges before reaching the set temperature 604.

[0049] 7 is a graph showing the relationship between the manipulated variable output to the heating unit and the detected temperature (detected value) in the injection molding machine M using the control device 10 according to the embodiment of the present invention. As shown in FIG. 7, the limit width is expanded, so that the integral manipulated variable 602 can be increased compared to FIG. 6.

[0050] Therefore, when the detected temperature 603 reaches the set temperature 604, the integral manipulated variable 602 also converges, and the detected temperature 603 reaches the set temperature 604 and is in a stable state.

[0051] 8 is a graph showing the relationship between the manipulated variable output to the heating unit and the added amount of the limit width during actual molding in an injection molding machine M using the control device 10 according to an embodiment of the present invention. When molding begins, the pressure inside the heating barrel increases, causing the detected temperature to increase. Therefore, it becomes necessary to lower the detected temperature to the set temperature.

[0052] 8, the integral manipulated variable 801 is not generated between 20 and 100 seconds, indicating a saturated region. By varying the limit width addition amount 802, the integral manipulated variable 802 can be generated even in the saturated region between 20 and 100 seconds. This allows the detected temperature to reach the set temperature.

[0053] As described above, according to this embodiment, a switch unit is provided that inputs the output of the second integrator to the second limiter when the difference between the input and output of the first limiter does not converge within a predetermined range. Therefore, even if the detected value PV of the controlled object (for example, the heating unit) does not reach the set value SV, it can be ensured to reach the set value SV by expanding the limit width, thereby making it possible to eliminate the offset.

[0054] The present invention is not limited to the above embodiment, and various modifications and improvements are possible within the scope of the present invention. For example, the integral time T I The limit width is expanded by multiplying by 10, but it is not limited to 10 times. For example, by using the expansion variable a, the deviation e is multiplied by e / (T I × a) can also be generalized. [Explanation of symbols]

[0055] 1, 10 Control device 7, 11 PID calculation section 20 Control Objects 71 First integral calculation unit 72 First Addition Unit 73 Coefficient switching unit 74 Proportional calculation section 75 Second Addition Unit 76 Differential operation section 77 First Output Limiter 78 Switch section 79 Second Output Limiter 80 routes 81 second integral calculation unit

Claims

1. a first integral calculation unit based on a deviation obtained by subtracting a detected value of the physical quantity from a set value of the physical quantity; a first adding unit that adds an output from the first integral calculation unit and an inversion of the detected value; a proportional calculation unit that calculates a proportional manipulated variable based on an output of the first adder; a differential calculation unit that calculates a differential operation amount based on the detected value; a second adder that adds the output from the first adder and the inverse of the output from the differential operation unit; a first output limiter that limits an output from the second adder to a value between a first upper limit value and a first lower limit value; a switch unit that is turned on when the output of the first output limiter is not saturated; a second output limiter that limits an output between a second upper limit value and a second lower limit value that are extensions of the first upper limit value and the first lower limit value; a second integral calculation unit that extends the second upper limit value and the second lower limit value and is based on a deviation that is a value obtained by subtracting the detected value from the set value; When the switch unit is in an on state, an output from the second integral calculation unit is input to the second output limiter; a path for feeding back to the first integral calculation unit a value obtained by subtracting an output from the second output limiter from an output from the proportional calculation unit; Equipped with the proportional calculation unit includes a first gain setting unit having 100 / PB; the differential calculation unit includes a differentiator and a second gain setting unit having Td×(100 / PB); The first integral calculation unit includes an integrator and a (1 / T I a third gain setting unit having a the second integral calculation unit includes an integrator and a fourth gain setting unit having (100 / PB)×(1 / T I )×(1 / 10); The control device according to claim 1, wherein the output from the first output limiter is output to a controlled object as a manipulated variable for controlling a physical quantity. (PB, T I and Td represent the proportional band, integral time, and derivative time, respectively.

2. the switch unit includes an operation amount determination unit that determines whether or not the second operation amount output from the first output limiter is within a predetermined range above and below the first operation amount output from the second adder, 2. The control device according to claim 1, wherein when the operation amount determination unit determines that the second operation amount is within a predetermined range above and below the first operation amount, the second integral calculation unit is connected to the second output limiter.

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