JP6255716B2 - Control device and control device for hot water supply system - Google Patents

Description

  The present invention relates to a control device and a water heater control device, and more particularly to a control device that controls output of a controlled object by combining feedforward control and feedback control.

  Feedforward control and feedback control are used to control the output of the controlled object following the target value. For example, Japanese Patent No. 3204050 (Patent Document 1) describes that the rotational speed of a fan motor for controlling the amount of air blown by a combustion device is controlled by a combination of feedforward control and feedback control. .

  Similarly, Japanese Patent No. 3504238 (Patent Document 2) describes the rotational speed control of a fan motor to which feedforward control is applied. Patent Document 2 describes that in order to reflect the individual difference of the fan motor, the rotational speed data when the fan motor is actually operated under a predetermined condition is stored to correct the feedforward control. .

Japanese Patent No. 3204050 Japanese Patent No. 3504238

  The feedback control described in Patent Document 1 is usually executed by a combination of proportional control and integral control. In general, transient deviations that occur in response to disturbances and changes in target values are compensated by proportional control, and steady deviations such as offsets such as individual differences in the control target are compensated by integral control. ing. However, in the integral control, if the control gain is increased due to the presence of a phase delay, there is a risk that periodic fluctuations in output (so-called hunting) may occur. On the other hand, when the control gain is small, the control response to the target value is lowered. Thus, adjustment of integral control is difficult.

  In addition, in the feedforward control described in Patent Document 2, a process for executing a special operation mode (FF amount correction mode) for actually operating a fan motor to obtain rotation speed data under a predetermined condition is an equipment. Since this is necessary every time, the workload increases.

  The present invention has been made to solve such problems, and an object of the present invention is to enhance the control accuracy of a control target by enhancing the function of a combination of feedforward control and feedback control. .

  The control device of the present invention is a control device for controlling an output value to be controlled to a control target value, and includes a feedback control unit, a feedforward control unit, a control correction unit, and a calculation unit. The feedback control unit calculates a feedback term based on an output deviation that is a difference between the detected value of the output value and the control target value. The feedforward control unit calculates a corresponding operation input value as a feedforward term when the output value is a control target value according to input / output characteristics obtained in advance between the operation input value and the output value to be controlled. . The control correction unit calculates a virtual input value corresponding to the detected value of the output value according to the input / output characteristics, and calculates a correction term based on a learning result of a difference between the actual operation input value to the control target and the virtual input value. To do. The calculation unit calculates an operation input value to the control target according to the feedforward term, the feedback term, and the correction term. The feedback control unit includes proportional control means for calculating a feedback term according to the product of the output deviation and the proportional control gain.

  According to the above control device, a change in the target value is followed by feedforward control, a steady deviation typified by an offset error is compensated by correction control for learning an input difference error, and proportional feedback is performed. Fordback control and feedforward control can be combined to control the output value of the controlled object so that the control compensates for a change in target value and a transient deviation corresponding to disturbance. As a result, by enhancing the combination of the feedforward control and the feedback control, the problem of phase delay in the integral feedback control can be solved and the control accuracy of the controlled object can be improved.

  Preferably, the control correction unit adds the correction term in the current control cycle and the difference between the operation input value and the virtual input value in the current control cycle according to a predetermined weighting, thereby correcting the correction term in the next control cycle. Is calculated.

  In this way, the learning speed in the control correction unit can be adjusted by changing the weighting, so that a control system including the correction control unit can be appropriately designed.

  Preferably, the feedback control unit does not execute the integral feedback control based on the integral value of the output deviation.

  In this way, after turning off the integral feedback control, which is likely to cause hunting when the gain is increased, the steady deviation represented by the offset error is compensated by the correction control that learns the error of the input difference. The control system can be designed.

  The control device for a hot water supply system of the present invention includes a feedback control unit, a feedforward control unit, a control correction unit, and a calculation unit. The feedback control unit calculates a feedback term based on an output deviation that is a difference between the detected value of the output value of the controlled object that is a component of the hot water supply system and the control target value. The feedforward control unit calculates a corresponding operation input value as a feedforward term when the output value is a control target value according to input / output characteristics obtained in advance between the operation input value and the output value to be controlled. . The control correction unit calculates a virtual input value corresponding to the detected value of the output value according to the input / output characteristics, and calculates a correction term based on a learning result of a difference between the actual operation input value to the control target and the virtual input value. To do. The calculation unit calculates an operation input value to the control target according to the feedforward term, the feedback term, and the correction term. The feedback control unit includes proportional control means for calculating a feedback term according to the product of the output deviation and the proportional control gain.

  According to the control system of the hot water supply system, the change of the target value is followed by the feedforward control, and the steady deviation represented by the offset error is compensated by the correction control for learning the error of the input difference, and Fordback control and feedforward control are combined to control the output value of the controlled object, which is a component of the hot water supply system, so as to compensate for the transition of the target value and the transient deviation corresponding to disturbance by proportional feedback control be able to. As a result, by enhancing the combination of the feedforward control and the feedback control, the problem of phase delay in the integral feedback control can be solved and the control accuracy of the controlled object can be improved.

  Preferably, the control target is a fan for supplying air to the combustion device, and the operation input value corresponds to a voltage value or a current value of an electric motor for driving the fan. The output value is the rotational speed of the fan.

  If it does in this way, the rotation speed of the combustion fan which is a component of the hot water supply system can be controlled at high speed and stably according to the target rotation speed.

  Preferably, the controlled object is a water heater, and the operation input value is a required amount of generated heat to the water heater. The output value is the temperature of hot water discharged from the water heater.

  If it does in this way, the hot water temperature of the water heater which is a component of the hot water supply system can be controlled at high speed and stably according to the set temperature.

  According to the present invention, the control accuracy of the controlled object can be increased by enhancing the combination of the feedforward control and the feedback control.

It is a block diagram which shows the structure of the hot water supply system controlled by the control apparatus according to embodiment of this invention. It is a functional block diagram for demonstrating the control structure shown as a comparative example. It is a conceptual diagram for demonstrating the input-output characteristic of the combustion fan which is a control object. It is a conceptual diagram for demonstrating the problem of integral feedback control. It is a functional block diagram for demonstrating the control structure by the control apparatus according to this invention. It is a Bode diagram for comparing gain characteristics of conventional integral feedback control and correction control used in the present embodiment. It is a Bode diagram for comparing gain characteristics of conventional integral feedback control and correction control used in the present embodiment. 10 is a chart for explaining a control target, an operation input value, an output value, and a feedforward arithmetic expression in the second embodiment by comparison with the first embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 is a block diagram showing a configuration of a hot water supply system 100 controlled by a control device according to an embodiment of the present invention.

  Referring to FIG. 1, hot water supply system 100 includes a water heater 110, a hot water supply pipe 180, a gas supply pipe 190, a hot water supply control unit 300, a fan control unit 310, and a burner control unit 320.

  The water heater 110 includes a can body 115, a gas burner 120, a heat exchanger 130, a combustion fan 160, and a fan motor 170.

  The functions of hot water supply control unit 300, fan control unit 310, and burner control unit 320 are realized by a microcomputer, for example. In the configuration example of FIG. 1, the hot water supply control unit 300, the fan control unit 310, and the burner control unit 320 are described as separate functional blocks. However, the functions of these functional blocks are realized by a common microcomputer. It is also possible to configure.

  The can body 115 is provided with an exhaust port 140 and an intake port 150. The gas burner 120 and the heat exchanger 130 are accommodated inside the can body 115. The gas burner 120 generates heat by burning the gas supplied from the gas supply pipe 190. The gas burner 120 is disposed close to the heat exchanger 130, and the amount of heat generated by the combustion of the gas burner 120 is transmitted to the water flowing through the hot water supply pipe 180 through the heat exchanger 130. Thereby, the water flowing through the hot water supply pipe 180 is heated.

  Combustion fan 160 is connected to intake port 150 and forcibly supplies combustion air into can 115. The exhaust port 140 discharges the exhaust after combustion to the outside of the can body 115. A gas proportional valve 200 is inserted and connected to the gas supply pipe 190. The gas proportional valve 200 is composed of, for example, a proportional electromagnetic valve. The gas pressure supplied to the gas burner 120 is controlled by the opening degree control of the gas proportional valve 200 according to the command from the hot water supply control unit 300. The gas supply amount per unit time to the gas burner 120 is controlled by controlling the gas pressure.

  The gas burner 120 is provided with a plurality of combustion pipes 125. The burner control unit 320 has a function of controlling the number of combustion pipes 125 to be supplied with fuel in response to a command from the hot water supply control unit 300. The burner control unit 320 has a function of controlling an electromagnetic valve (not shown) that is connected between the gas supply pipe 190 and each combustion pipe 125 and is controlled to open and close. The amount of heat output from the gas burner 120 to the heat exchanger 130 can be controlled by a combination of the number of combustion tubes 125 supplied with fuel and the gas pressure.

  Combustion fan 160 is driven by fan motor 170. The fan motor 170 is constituted by, for example, a DC motor. The amount of air supplied from the combustion fan 160 to the can body 115 changes according to the rotational speed of the combustion fan 160 (hereinafter also referred to as fan rotational speed). The fan speed is detected by the fan speed detector 240. The fan rotation speed detection unit 240 is configured by, for example, an electromagnetic pickup type sensor attached to a rotating body of the combustion fan 160 or the fan motor 170.

  The hot water supply pipe 180 is provided with a flow rate sensor 210 and temperature sensors 220 and 230. A hot water tap (not shown) is connected to the tip of the hot water supply pipe 180. When the hot-water tap is opened, the flow rate Q> 0. The flow rate Q changes according to the opening degree of the hot water tap. The flow rate sensor 210 detects the flow rate Q of the hot water supply pipe 180. The temperature sensor 220 is provided on the downstream side of the heat exchanger 130 and detects the tapping temperature Th. On the other hand, the temperature sensor 230 is provided on the upstream side of the heat exchanger 130 and detects the incoming water temperature Tc.

  The set temperature Tr * of the hot water supply system 100 is input to the hot water supply control unit 300. Further, detection values by flow sensor 210, temperature sensors 220 and 230, and fan rotation speed detection unit 240 are input to hot water supply control unit 300. The hot water supply control unit 300 controls the operation of the hot water supply system 100 so that the hot water temperature from the hot water supply pipe 180 is controlled according to the set temperature Tr *.

  Specifically, hot water supply control unit 300 sets required heat generation amount Qtl to hot water heater 110 based on set temperature Tr * and detected incoming water temperature Tc, outgoing hot water temperature Th, and flow rate Q. Furthermore, the hot water supply control unit 300 calculates a gas supply amount to the gas burner 120 based on the required generated heat amount Qtl, and generates an opening degree command of the gas proportional valve 200 corresponding to the calculated gas supply amount. The opening degree command is output to the gas proportional valve 200. The gas proportional valve 200 supplies the gas burner 120 with a gas amount corresponding to the required generated heat amount Qtl by being controlled to the target opening degree according to the opening degree command from the hot water supply control unit 300.

  The hot water supply control unit 300 further sets the target fan rotational speed Fr of the combustion fan 160 in conjunction with the control of the gas supply amount to the gas burner 120. The target fan speed Fr is sequentially set so that the air-fuel ratio in the gas burner 120 is maintained at a predetermined value. The target fan rotation speed Fr of the combustion fan 160 is output to the fan control unit 310.

  The fan control unit 310 controls the fan rotation number to the target fan rotation number Fr according to the fan rotation number Fc detected by the fan rotation number detection unit 240 and the target fan rotation number Fr instructed from the hot water supply control unit 300. Fan control command value Fm is set.

  The fan rotation speed changes according to the power (voltage × current) supplied to the fan motor 170 from a power converter (not shown). Therefore, the fan speed can be controlled by controlling the voltage or current supplied to the fan motor 170 in accordance with the fan control command value Fm from the fan control unit 310. For example, the fan control command value Fm can be a duty command value when the on-duty of the switching element of the power converter is subjected to pulse width modulation control.

  In the first embodiment, the fan control unit 310 constitutes a “control device” according to the present embodiment. That is, the combustion fan 160 is controlled by the control device according to the present invention. Accordingly, the fan rotation speed Fc corresponds to the “output value”, the target fan rotation speed Fr corresponds to the “control target value”, and the fan control command value Fm corresponds to the “operation input value”. In the present embodiment, it is assumed that digital control is performed in which an operation input value to be controlled is updated every predetermined control cycle.

  First, a conventional control configuration combining feedforward control and feedback control will be described as a comparative example.

FIG. 2 is a functional block diagram for explaining a control configuration shown as a comparative example.
Referring to FIG. 2, control system 500 # according to the comparative example includes a feedforward control unit (hereinafter referred to as FF control unit) 510, a feedback control unit (hereinafter referred to as FB control unit) 520, and a calculation unit 550.

  The output value X of the control object 600 changes according to the operation input value Ui. Control system 500 # sets operation input value Ui so as to control output value X to target value Xs. As an example, when the controlled object 600 is the combustion fan 160, X = Fc, Xs = Fr, and Ui = Fm.

  The FF control unit 510 calculates a feedforward control term (FF control term) Uff according to the target value Xs. The feedforward control is set according to a predetermined feedforward arithmetic expression that indicates the correspondence relationship between the output value and the operation input value of the control target 600 (combustion fan 160).

  FIG. 3 is a conceptual diagram for explaining the input / output characteristics of the combustion fan 160 to be controlled.

  Referring to FIG. 3, the fan rotation speed Fc of the combustion fan 160 that is the control target 600 changes according to the fan control command value Fm. A characteristic line 700 can be obtained by previously obtaining a correspondence relationship (hereinafter also referred to as input / output characteristics) of the fan rotation speed Fc with respect to the fan control command value Fm by an experiment or the like. A characteristic line 700 indicates input / output characteristics between the operation input value Ui and the output value X of the control object 600.

  According to the characteristic line 700, Fm = U0 can be obtained as the fan control command value Fm when the fan rotational speed Fc becomes the target fan rotational speed Fr. U0 corresponds to the operation input value Ui when the output value X becomes the target value Xs (X = Xs). The FF control unit 510 sets the FF control term Uff based on the target value Xs (target fan rotation speed Fr) according to the characteristic line 700. That is, in the example of FIG. 3, Uff = U0 is set.

  For example, by linearly approximating the characteristic line 700, a feedforward arithmetic expression FF [X] for calculating the FF control term Uff from the output value X is defined as a linear expression with X as a variable. Can be set as follows. In the equation (1), ka and kb are constants according to the characteristic line 700.

Uff = FF [X] = X × ka + kb (1)
The FF control unit 510 calculates the FF control term Uff according to the equation (2) by setting X = Xs (n) in the equation (1).

Uff (n) = Xs (n) × ka + kb (2)
By the feedforward control, the operation input value Ui (fan control command value Fm) is changed corresponding to the change of the target value Xs (target fan rotation speed Fr) reflecting the characteristics of the control target 600 (combustion fan 160). be able to.

  Actually, the characteristic line 700 of the combustion fan 160 has variations due to individual differences between devices. However, separately obtaining the characteristic line 700 for all the combustion fans 160 requires a large work load. Therefore, in the hot water supply system 100 having the same specifications, it is generally configured according to the common characteristic line 700. Is.

  As a result, when the feedforward control is executed using the common characteristic line 700, the combustion fan 160 that actually has the input / output relationship of the characteristic lines 701 and 702 due to individual differences causes an offset error ( It will be understood that U0-U1 or U2-U0) in FIG. In this way, a control error occurs in the output value due to individual differences of control objects, including feedforward control. This control error can be compensated by feedback control.

  The FB control unit 520 includes a deviation calculation unit 525, a proportional control calculation unit 530, an integral control calculation unit 540, and a calculation unit 545.

  The deviation calculator 525 calculates an output deviation ΔX of the output value X with respect to the target value Xs (ΔX = Xs−X). The proportional control calculation unit 530 calculates the FB control term Ufbp by proportional feedback control according to the product of the proportional gain Kp and the output deviation ΔX. For example, in the nth (n: natural number) control cycle, the proportional control calculation unit 530 executes the calculation of the following equation (3).

Ufbp (n) = Kp × ΔX (n) (3)
Note that ΔX (n) = Xs (n) −X (n) in the formula (3).

  Thus, the FB control term Ufbp is calculated so as to eliminate the output deviation ΔX caused by the change of the target value Xs or the occurrence of disturbance. That is, the proportional control mainly ensures transient control performance such as followability to the change of the target value Xs.

  The integration control calculation unit 540 calculates the FB control term Ufbi by integration control according to the product of the integral value of the output deviation ΔX and the integration gain Ki. For example, in the nth control cycle, the integral control calculation unit 540 executes the calculation of the following equation (4).

Ufbi (n) = Ufbi (i−1) + Ki × ΔX (n) (4)
Thereby, the operation input value is calculated mainly so as to eliminate the steady output deviation ΔX in a state where the target value Xs is stable. That is, the integral control mainly ensures control performance in a steady state such as convergence to the target value Xs.

  The arithmetic unit 545 adds the FB control term Ufbp by proportional control and the FB control term Ufbi by integral control to calculate the FB control term Ufb by the FF control unit 520.

  The arithmetic unit 550 adds the FF control term Uff by the FF control unit 510 and the FB control term Ufb by the FB control unit 520 to set the operation input value Ui of the control target 600 according to the following equation (5). .

Ui (n) = Uff (n) + Ufb (i) (5)
Thereby, the feedforward control for following the change of the target value Xs and the feedback control for compensating the output deviation ΔX are combined, and the output value X (fan rotation speed Fc) of the control target 600 is set to the target value Xs. It can be controlled to (target fan rotation speed Fr).

  That is, the control error caused by the individual difference of the control target 600 (combustion fan 160) described in FIG. 3 can also be compensated for by feedback control. As understood from FIG. 3, since the control error occurs as an offset error, it is compensated by integral feedback control as a steady-state deviation. However, the integral feedback control has a problem that the control gain cannot be increased.

FIG. 4 is a conceptual diagram for explaining the problem of integral feedback control.
Referring to FIG. 4, before time t0, output value X is lower than target value Xs. By setting FB control term Ufbi> 0 by integral feedback control, X rises toward Xs. As a result, ΔX decreases, but since ΔX> 0, the FB control term Ufbi continues to increase.

  At time t0, since X = Xs, the output deviation ΔX = 0. From this point on, ΔX <0 and the FB control term Ufbi begins to decrease, but since it is within the region of Ufbi> 0, the output value X continues to increase. That is, the output value X continues to increase until time t1 when the integrated value of ΔX becomes zero. After time t1, since Ufbi <0, the output value X starts to decrease.

  That is, in the integral feedback control, a phase delay that increases the output deviation ΔX by setting Ufbi> 0 occurs between times t0 and t1. Due to the presence of this phase delay, if the integral gain Ki is increased, there is a risk of causing a periodic fluctuation (hunting) of the output value. As a result, in normal integral control, it is difficult to increase the control speed for compensating for the offset error described in FIG.

  For this reason, the control device according to the present embodiment employs a control configuration that combines correction control for compensating for output deviations caused by individual variations of control targets.

  FIG. 5 is a functional block diagram for illustrating a control configuration by the control device according to the present invention.

  Referring to FIG. 5, control system 500 according to the present invention includes an FF control unit 510, an FB control unit 520, and a correction control unit 580.

  Similarly to FIG. 3, the FF control unit 510 calculates the FF control term Uff based on the target value Xs according to a preset feedforward arithmetic expression (for example, expression (2)).

  The feedback control unit 520 includes a deviation calculation unit 525 and a proportional control calculation unit 530. Deviation calculation unit 525 and proportional control calculation unit 530 calculate FB control term Ufbp by proportional feedback control according to the above-described equation (3).

  In the control system 500, the offset error is compensated by the correction control unit 580. As a result, the weight of the integral feedback control for compensating the steady output deviation can be reduced. Preferably, the integral feedback control, which inevitably includes a phase delay and is difficult to adjust, is turned off, and the feedback control can be executed only by the proportional feedback control. Therefore, preferably, the FB control term Ufb is set to Ufb (n) = Ufbp (n) = Kp × ΔX (n) according to proportional feedback control.

  Alternatively, the integral feedback control substantially does not contribute by reducing the integral gain Ki in the equation (4) from the normal value, which is substantially included in turning off the integral feedback control. . In this case, it is necessary to adjust the integral gain Ki in consideration that coexistence with the correction control unit 580 does not cause a control disturbance.

  The correction control unit 580 calculates the control correction term Ucr by learning individual differences in input / output characteristics of the control target 600 (combustion fan 160). The correction control unit 580 calculates a virtual input value Uv corresponding to the current output value X according to a reference input / output characteristic (for example, the characteristic line 700 shown in FIG. 3), and the virtual input value Uv and the actual input value Uv. An input difference ΔU that is a difference from the operation input value Ui is learned. The input difference ΔU is caused by an error between the actual input / output characteristic of the control target 600 and the reference input / output characteristic (characteristic line 700). Therefore, the control correction term Ucr calculated by learning the input difference ΔU is a value corresponding to an error between the characteristic line according to the actual input / output characteristic of the controlled object 600 and the characteristic line 700, particularly an offset error. It is understood.

  For example, the virtual input value Uv can be obtained by sharing the feedforward arithmetic expression FF [X] in the FF control unit 510 (Uv (n) = FF [X (n)] = X (n) × ka + kb. ). Further, the actual operation input value Ui (n) = Fm (i). Therefore, the input difference ΔU of the controlled object 600 (combustion fan 160) can be calculated according to the following equation (6). Furthermore, the control correction term Ucr corresponding to the learned value of the input difference ΔU can be calculated according to the following equation (7).

  In Expression (7), p is a learning parameter, and p is set within a range of 0 <p <1. As the learning parameter p increases, the learning speed for reflecting the input difference ΔU in the current output value to the control correction term Ucr increases.

  Alternatively, using the learning parameter L, the equation (7) can be transformed into the following equation (8). L is set in the range of L> 0. The smaller the learning parameter L, the faster the learning speed. That is, learning by the correction control unit 580 is performed by using the input difference ΔUi (n) in the current control cycle and the learned value Ucr (n) in the current control cycle according to a predetermined weight determined by the learning parameter L or p. By performing the addition, the next control cycle Ucr (n + 1) is executed.

  The calculation unit 550 sets the operation input value Ui of the control target 600 by adding the FF control term Uff, the FB control term Ufb, and the control correction term Ucr. In the first embodiment, fan control command value Fm (n) = Ui (n) is set. In response to this, the fan rotational speed Fc corresponding to the output value X of the controlled object 600 is controlled to the target fan rotational speed Fr corresponding to the target value Xs.

  Thus, in the control system 500 according to the present embodiment, correction control based on learning of individual differences in input / output characteristics of the controlled object 600 is executed instead of integral feedback control. Therefore, the frequency characteristics of the conventional integral feedback control and the correction control used in the present embodiment are compared.

  The integral feedback control is calculated according to the above equation (4). For this reason, the discretized transfer function H (z) is expressed by the following equation (9).

  With respect to the transfer function H (z) shown in Expression (9), the gain and phase difference with respect to the input of the angular frequency ω are expressed by Expression (10) and Expression (11), respectively.

  On the other hand, according to the calculation of the control correction term Ucr (n) shown in the equation (8), the discretized transfer function H (z) is expressed by the following equation (12).

  With respect to the transfer function H (z) shown in Expression (12), the gain and phase difference with respect to the input of the angular frequency ω are expressed by Expression (13) and Expression (14), respectively.

  6 and 7 are Bode diagrams for comparing the integral feedback control and the correction control. The horizontal axis of FIGS. 6 and 7 shows the frequency parameter f / fs obtained by dividing the input frequency f by the sampling frequency fs corresponding to the reciprocal of the control period. The vertical axis of FIG. 6 shows the input / output ratio (gain) of the transfer function H (z), and the vertical axis of FIG. 7 shows the phase difference of the output with respect to the input of the transfer function H (z).

  FIG. 6A shows the gain characteristic of the correction control, while FIG. 6B compares the gain characteristic of the integral feedback control. FIG. 7A shows the phase characteristic of the correction control, while FIG. 7B compares the phase characteristic of the integral feedback control.

  As understood from FIGS. 6B and 7B, in the conventional integral feedback control, the gain diverges in the low frequency region, and the occurrence of the phase delay is unavoidable.

  Therefore, the integral gain Ki cannot be so high in order to ensure stability in the low frequency region. As a result, it is difficult to shorten the time until the output value is settled with respect to the change of the target value. Further, there is a concern that the output value may be vibrated against low-frequency disturbances.

  On the other hand, as understood from FIG. 6A, in the correction control used in the present embodiment, the maximum gain value can be limited to 1.0 even when f = 0. In addition, the gain can be adjusted by changing the learning parameter L.

  Further, as understood from FIG. 7A, in the correction control, the phase delay can be changed by the learning parameter L (or p) at f = 0.

  From the characteristics shown in FIGS. 6A and 7A, it is understood that the correction control used in the present embodiment has a high compensation capability for a DC error. Therefore, it is possible to quickly compensate for the above-described offset error (for example, control error caused by a shift in input / output characteristics) caused by individual differences in the control target 600. Further, since the gain and phase characteristics can be adjusted by adjusting the learning parameter L (or p in the equation (7)), by setting an appropriate frequency characteristic even for high-frequency disturbances. Can be compensated.

  As described above, according to the embodiment of the present invention, the change of the target value is followed by the feedforward control, and the steady deviation represented by the offset error is corrected by the correction control instead of the conventional integral feedback control. Fordback control and feedforward control can be combined to compensate and compensate for transient deviations corresponding to target value changes and disturbances by proportional feedback control. As a result, by enhancing the combination of the feedforward control and the feedback control, the problem of phase delay in the integral feedback control can be solved and the control accuracy of the controlled object can be improved. In the example of the first embodiment, the rotational speed of the combustion fan 160 (fan rotational speed Fc) can be controlled stably and promptly according to the target fan rotational speed Fr.

  In particular, by using a common arithmetic expression for the correction control and the feedforward control, the correction control also has a function of compensating for an error in the feedforward control according to the characteristic line 700, so that the controllability is further improved.

[Embodiment 2]
With reference to FIG. 1 again, in the first embodiment, the example in which the combustion fan 160 is the control target 600 has been described. However, the control configuration according to the present embodiment can be applied even if the control target is another device. is there. In the second embodiment, an example in which the water heater 110 is the control target 600 will be described. Therefore, in the second embodiment, the hot water supply control unit 300 constitutes a “control device” according to the present embodiment.

  FIG. 8 is a chart for explaining the controlled object, operation input value, output value, and feedforward arithmetic expression in the second embodiment by comparison with the first embodiment.

  Referring to FIG. 8, when water heater 110 is controlled object 600 (FIG. 5), operation input value Ui of controlled object 600 becomes required heat generation amount Qtl of water heater 110. And the output value X becomes the hot water temperature Th from the water heater 110.

  Generally, in a hot water supply apparatus, the required generated heat quantity Qtl is calculated in units of numbers. The number = 1 corresponds to the amount of heat required to raise the hot water temperature by 25 degrees at a flow rate of Q = 1 (L / min). Therefore, in the following, the required heat generation amount Qtl is also referred to as an input number Qtl. As described above, the amount of gas supplied to the gas burner 120 (FIG. 1) is calculated based on the input number Qtl. Then, by controlling the opening degree of the gas proportional valve 200 in correspondence with the calculated supply gas amount, a gas amount for generating a heat amount corresponding to the input number Qtl is supplied to the gas burner 120.

  In order to set the tapping temperature Th in the water heater 110 to the set temperature Tr *, it is necessary to raise the water at the flow rate Q from the incoming water temperature Tc to the set temperature Tr *. Therefore, according to the definition of the above number, the feedforward arithmetic expression FF [X] having the tapping temperature as the variable (X) can be set according to the following expression (15).

FF [X] = (X−Tc) / 25 × Q (15)
Therefore, the feedforward control can calculate the FF control term Uff (n) in the nth control cycle according to the following equation (16) according to the set temperature Tr * that is the target value of the tapping temperature.

  The output deviation ΔX (FIG. 2) in the feedback control is a temperature deviation of the tapping temperature Th with respect to the set temperature Tr * (ΔX = Tr * −Th). Therefore, the FB control term Ufb is calculated by proportional feedback control of the temperature deviation. That is, the FB control term Ufb (n) in the nth control cycle can be calculated according to the following equation (17).

  In the second embodiment, in learning of individual differences in input / output characteristics of the controlled object 600 in the correction control, the virtual input value Uv corresponding to the current output value X is expressed by the feedforward arithmetic expression shown in Expression (15): It can be obtained by substituting X = Th. Further, the actual operation input value Ui (n) = Qtl (n). Therefore, the input difference ΔU for learning can be calculated according to the following equation (18).

  The control correction term Ucr can be calculated by learning the input difference ΔUi calculated for each control period according to Equation (18) according to Equation (7) or Equation (8).

  Using the FF control term Uff (n), the FB control term Ufb (n), and the control correction term Ucr (n) calculated in this way, the input number Qtl (n) of the water heater 110 is set. Thus, as in the first embodiment, a steady deviation represented by an offset error can be compensated by correction control instead of the conventional integral feedback control. Thereby, the problem of the phase delay in the integral feedback control can be solved, and the control accuracy of the controlled object can be improved.

  As a result, in the example of the second embodiment, the hot water temperature Th of the water heater 110 can be stably and quickly controlled to the set temperature Tr *.

  In the first and second embodiments, the example in which the control target of the control device according to the present embodiment is a component of the hot water supply system has been described. However, the application of the present invention is limited to the control target of the exemplified control target. It is not a thing. That is, if it is a control target that causes an offset-like output error due to individual differences, other components of the hot water system, or other devices other than the hot water system are also used to control the output value of the control target. The present invention can be applied.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 100 Hot-water supply system, 110 Hot-water supply unit, 115 Can body, 120 Gas burner, 125 Combustion pipe, 130 Heat exchanger, 140 Exhaust port, 150 Intake port, 160 Combustion fan, 170 Fan motor, 180 Hot-water supply pipe, 190 Gas supply pipe, 200 Gas proportional valve, 210 Flow rate sensor, 220, 230 Temperature sensor, 240 Fan rotation speed detection unit, 300 Hot water supply control unit, 310 Fan control unit, 320 Burner control unit, 500 control system, 510 FF control unit, 520 FB control unit, 525 Deviation calculation unit, 530 proportional control calculation unit, 540 integral control calculation unit, 545, 550 calculation unit, 580 correction control unit, 600 control target, 700, 701, 702 characteristic line, Fc fan rotation speed, Fm fan control command value , Fr Target fan speed, Q flow rate, Qtl Required heat generation (input number), Tc inlet water temperature, Th outlet temperature, Tr set temperature, Ucr control correction term, Ufb FB control term, Uff FF control term, Ui operation input value, Uv virtual input value, X output value, Xs Target value, f input frequency, fs sampling frequency.

Claims (5)

A control device for controlling an output value to be controlled to a control target value,
A feedback control unit for calculating a feedback term based on an output deviation that is a difference between the detected value of the output value and the control target value;
In order to calculate the corresponding operation input value as a feed-forward term when the output value is the control target value according to the input / output characteristic obtained in advance between the operation input value to be controlled and the output value A feedforward control unit of
According to the input / output characteristics, a virtual input value corresponding to the detected value of the output value is calculated, and a correction term based on a learning result of a difference between the actual operation input value to the control target and the virtual input value is calculated A control correction unit for
A calculation unit for calculating the operation input value to the control target according to the feedforward term, the feedback term, and the correction term;
The feedback control unit includes:
Look including a proportional control means for calculating the feedback term in accordance with the product of a proportional control gain and the output deviation,
The control correction unit adds the correction term in the current control cycle and the difference between the operation input value and the virtual input value in the current control cycle according to a predetermined weight, thereby correcting the correction in the next control cycle. A control device that calculates a term . The feedback control unit sets the integral feedback control based on the integral value of the output deviation not executed, according to claim 1 Symbol placement of the control device. A control device for a hot water supply system,
A feedback control unit for calculating a feedback term based on an output deviation that is a difference between a detected value of a control target output value that is a component of the hot water supply system and a control target value;
In order to calculate the corresponding operation input value as a feed-forward term when the output value is the control target value according to the input / output characteristic obtained in advance between the operation input value to be controlled and the output value A feedforward control unit of
According to the input / output characteristics, a virtual input value corresponding to the detected value of the output value is calculated, and a correction term based on a learning result of a difference between the actual operation input value to the control target and the virtual input value is calculated A control correction unit for
A calculation unit for calculating the operation input value to the control target according to the feedforward term, the feedback term, and the correction term;
The feedback control unit includes:
Look including a proportional control means for calculating the feedback term in accordance with the product of a proportional control gain and the output deviation,
The control correction unit adds the correction term in the current control cycle and the difference between the operation input value and the virtual input value in the current control cycle according to a predetermined weight, thereby correcting the correction in the next control cycle. A control device for a hot water supply system that calculates a term . The control object is a fan for supplying air to the combustion device,
The operation input value corresponds to a voltage value or a current value of an electric motor for driving the fan,
The hot water supply system control device according to claim 3 , wherein the output value is a rotation speed of the fan. The control object is a water heater,
The operation input value is a required heat generation amount to the water heater,
The hot water supply system control device according to claim 3 , wherein the output value is a temperature of hot water discharged from the water heater.

Images