JP4337101B2 - Time proportional controller - Google Patents

Description

  The present invention relates to a time-proportional control apparatus suitable for controlling temperature by turning on / off a cooler, for example.

  In the temperature control in the thermostatic chamber, the temperature control of the plastic raw material in the injection molding machine, etc., the heating capability by the heater (heater) and the cooling capability by the cooler (cooler) are properly used. This type of control is referred to as heat-cool control, and the heating is performed exclusively according to the deviation between the control target temperature (set value SP) set by the operator and the temperature of the control target (control value PV) detected by the sensor. An operation amount MV for the heater or the cooler is obtained, and the operations of the heater and the cooler are respectively controlled according to the operation amount MV (see, for example, Patent Document 1). Specifically, for example, the heater is turned on / off controlled according to the operation amount MV, and the compressor operation in the cooler is turned on / off.

  Incidentally, the manipulated variable MV is obtained, for example, by a PID control calculation incorporated in a feedback control loop (see, for example, Patent Document 2). When the operation of the cooler (compressor) is controlled in the control system described above, a time proportional output according to the operation amount MV is exclusively used. This time proportional output is obtained by changing the ratio of the ON time and the OFF time of the output signal within a preset period (cycle time) according to the manipulated variable MV. For example, when the manipulated variable MV is 50%. In some cases, the signal is output as a signal in which the first half time of one cycle time is on (high) and the second half time is off (low).

Specifically, when controlling the operation of the cooler (compressor), considering the durability (life) of the actuator that is a mechanically movable part of the cooling control system, the cycle time of the time proportional output described above is For example, it is set long as 10 to 30 seconds. On the other hand, the energization control of the heater (heater) is performed exclusively without using mechanically movable parts, and therefore, for example, the cycle time is set to be as short as about 1 second.
Japanese Patent Laid-Open No. 5-289704 Japanese Patent Laid-Open No. 2004-227062

  By the way, in the control system in which the cycle time of the time proportional output is set to be long as described above, for example, when the manipulated variable MV largely changes with the change of the control target temperature (set value SP), the timing of the change is the cycle. If it is in the middle of the time, the time proportional output does not change until the next cycle time, so it cannot be denied that a significant control delay occurs. Specifically, the cycle time of the time proportional output is 30 seconds, and even if the manipulated variable MV changes greatly when the cycle time has elapsed 10 seconds, the time proportional output is continued until the next cycle time 20 seconds later starts. Will not change. Therefore, there is a problem that a desired control result cannot be obtained.

The present invention has been made in view of such circumstances, and its purpose is to operate the control system in accordance with a change in the control target temperature (set value SP), for example, in a control system having a long cycle time of time proportional output. An object of the present invention is to provide a time proportional control device capable of obtaining a control result with good responsiveness by changing the time proportional output with good followability even when the amount MV changes greatly.
In particular, an object of the present invention is to provide a time-proportional control device suitable for controlling the temperature of a constant temperature bath or the like by controlling on / off of the operation of a cooler, for example.

In order to achieve the above-described object, the time proportional control device according to the present invention provides a time proportional output that is turned on at predetermined intervals to a controller that is controlled to be turned on / off and changes the state of the controlled object. together is turned on the controller over the on-time in the time-proportional output given deviation between the value indicating the state of the control target value and the controlled object the on-time of the time-proportional output for the control object is zero A time-proportional control device that controls so that
When the control target value is changed within the cycle time defined by the predetermined period, the deviation changed with the change of the control target value at the time of change of the control target value is set to zero. While newly obtaining the on-time of the time proportional output,
Compare the newly determined ON time of the time proportional output with the ON elapsed time of the time proportional output already output in the current cycle time,
When the newly determined on-time is longer than the on-elapsed time, a time proportional output of the on-time that compensates for the difference between the on-time and the on-elapsed time in the remaining period of the current cycle time, A means for newly generating a value change point as a base point is provided .

  Incidentally, the controlled object is, for example, a temperature controlled by a cooler, and the time-proportional output is obtained as a signal that defines an on-time of the cooler within a predetermined period (cycle time). Item 2]. Alternatively, the object to be controlled is, for example, a temperature controlled by a cooler and a heater, and the time proportional output is a signal that prescribes an ON time of the cooler within a predetermined first period, or The signal may alternatively be generated as a signal that defines the on-time of the heater within a predetermined second period.

For the time proportional output, for example, an output value of a counter that sequentially outputs a value corresponding to 0 to 100% over one cycle time, and an operation amount corresponding to the deviation given as a value of 0 to 100%. And is obtained as a signal that is output over a period in which the manipulated value exceeds the output value of the counter and defines the ON time in the cycle time,
When the deviation is changed, the operation amount corresponding to the ON time of the time proportional output that has already been output up to the time of the deviation change from the operation amount corresponding to the new deviation given as a new value of 0 to 100%. In addition to subtracting, the output value of the counter at the time of the deviation change is added to obtain a correction operation amount within the cycle time , and the correction operation amount is compared with the output value of the counter. Control may be performed so as to obtain an additional time proportional output over a period exceeding the output value .

  According to the time proportional control apparatus having the above-described configuration, for example, when the control target value SP for the controlled object is changed and the deviation from the value indicating the state of the controlled object is changed accordingly, the time until the deviation changes is reached. Compare the on-elapsed time of the time proportional output within the output current cycle time with the on-time of the time proportional output according to the new deviation, and if the on-time according to the new deviation is long, The time proportional output is newly generated over a time corresponding to the difference between the on-time and the on-elapsed time with a deviation change time as a trigger. That is, when the on-time of the time proportional output is insufficient within the cycle time, a time proportional output corresponding to the shortage time is newly generated and output.

  As a result, the sum of the on-time of the time proportional output within the cycle time can be made to correspond to the changed deviation, so control with good responsiveness is eliminated by eliminating the control delay depending on the cycle time of the time proportional output. The result can be obtained. In addition, since the cycle time of the time proportional output does not shift, even when a plurality of controlled devices are operated in synchronization with each other, the synchronization of the control system for these controlled devices may be disturbed. Absent. Since it is only necessary to reset itself and generate a new time-proportional output based on this reset timing, the control response can be effectively improved with only simple control.

  Especially when the temperature of the cooler is controlled by on / off control, the on-time of the time proportional output can be increased without shortening the cycle time of the time proportional output and without shifting the cycle time. Therefore, while maintaining synchronization with a large number of devices, the control responsiveness can be improved practically without sacrificing the durability (life) of the actuator in the cooling control system. An effect is produced.

Hereinafter, with reference to the drawings, a time proportional control device according to an embodiment of the present invention will be described by taking as an example a case in which a cooler is on / off controlled by a time proportional output for performing temperature control of an object to be controlled.
FIG. 1 is a diagram showing a schematic configuration of a control system in this time proportional control device. 10 is a control unit (time proportional control device) mainly composed of a microprocessor or the like, and 20 is a control object such as a thermostatic bath. . The temperature of the controlled object 20 is controlled using the cooler 21, and the temperature (control value PV) is detected via the temperature sensor 22.

  The control unit (time proportional control device) 10 basically includes a control target temperature (target set value SP) 12 set by an operator via an operation unit 11 such as a keyboard or a touch panel, and the temperature sensor 22 described above. In accordance with the deviation from the temperature (control value PV) 13 of the control object 20 detected in this way, for example, the operation amount MV corresponding to the deviation is obtained as a PID output by the PID control unit 14 and set in advance in the time proportional output unit 15. A time proportional output Ton corresponding to the manipulated variable (PID output) MV is obtained every cycle (cycle time).

  Incidentally, the PID output is composed of, for example, a continuous voltage output of 0 to 10 V corresponding to an operation amount MV of 0 to 100%, or a continuous current output of 4 to 20 mA. Further, the time proportional output Ton, for example, the ratio of the output time of the continuous ON signal in the cycle time of 30 seconds is linearly changed over 0 to 100% corresponding to the operation amount MV of 0 to 100%. It consists of a signal that turns off later. The cooler 21 described above operates only during the output period (on period) of such a time proportional output Ton to cool the controlled object 20.

  Basically, the present invention is characterized in the control unit 10 configured to have such a function when the control target temperature (target set value SP) 12 set by the operation unit 11 is changed. Alternatively, when the operation amount (PID output) MV obtained by the PID control unit 14 changes greatly, the time proportional output of the on time corresponding to the change amount of the operation amount (PID output) MV is within the cycle time. In addition, an output control unit 16 for controlling the operation of the time proportional output unit 15 is provided.

  Specifically, the output control unit 16 outputs the time proportional output Ton having a time width corresponding to 30% of the cycle time when the operation amount (PID output) MV is 30%, for example, and then the operation amount (PID). Output) When the MV is changed to 50%, a time proportional output Ton having a time width corresponding to a change amount of 20% of the manipulated variable (PID output) MV is added and output with the change time as a trigger. The operation of the time proportional output unit 15 is controlled. Then, by adding this time proportional output Ton, the output time (on time) of the total time proportional output Ton at that cycle time is set to 50%, thereby changing the manipulated variable (PID output) MV. It is intended to promptly follow.

Here, the generation of the time proportional output Ton in the time proportional unit 15 based on the control of the output control unit 16 will be described according to the control procedure shown in FIGS. 3 and 4 with reference to the timing chart shown in FIG.
The time proportional unit 15 includes, for example, a counter that counts a value corresponding to 0 to 100% over one cycle time, and the operation amount (PID output) indicating a value of 0 to 100% as shown in FIG. By comparing the MV with the count value (counter value) TC of the counter, a signal that is turned on over a period in which the manipulated variable MV exceeds the counter value TC is generated as the time proportional output Ton described above, and output Configured to do. Then, when the set value SP is changed in the middle of the cycle time, or when the operation amount (PID output) MV changes greatly, the time width corresponding to the change amount of the operation amount MV is explained as follows. The proportional output Ton is newly generated with the change point of the manipulated variable MV as a trigger.

  Specifically, in the time proportional calculation, first, as shown in FIG. 3, the count value (counter value) TC of the counter is acquired as the current cycle time elapsed time (%) <Step S1>, and then the count value TC is obtained. The process starts by determining whether or not one cycle time (100%) has been reached, that is, whether or not one cycle time has ended (step S2). If the counter value TC reaches 100%, the counter is reset and the counter value TC is initialized to [0] (step S3). Further, the parameters STC, TAT, TSC, TR used for controlling the additional generation of the time proportional output To are initialized to [0], respectively, and the ON history (flag) of the time proportional output is initially set to OFF <Step S4>. .

  The time proportional output ON history (flag) is information indicating whether or not the time proportional output Ton has already been output within one cycle time. Normally, when the ON history of the time proportional output is ON [1], generation of a new time proportional output Ton within the cycle time is prohibited. The parameter STC is information indicating the time elapsed (ON time) after the time proportional output Ton is turned on, and the parameter TAT is the time proportional output Ton currently output added within one cycle time. This is information (flag) indicating whether or not. The parameter TSC is information indicating the sum of times when one time proportional output Ton is turned on, and the parameter TR is information indicating the output cumulative time of the time proportional output Ton within one cycle time.

  After completing the initialization process at the end of one cycle time as described above, or when the current cycle time elapsed time, that is, when the count value (counter value) TC is less than one cycle time, first, The PID output at the time is acquired as an operation amount MV used for generation (output control) of the time proportional output Ton (step S5). Incidentally, the PID output is sequentially obtained, for example, every 0.1 second in a cycle shorter than one cycle time set sufficiently long as 30 seconds or the like in consideration of the life of the actuator for turning on and off the refrigerator, for example. In other words, the processing routine shown in FIG. 3 is repeatedly executed at high speed in synchronism with the period in which the PID output is obtained.

  If the manipulated variable MV is acquired as described above <Step S5>, it is then determined whether or not a condition (trigger) for adjusting the time proportional output is generated within one cycle time <Step S6>. This determination is performed, for example, by examining the parameter TAT described above. This parameter TAT is set to ON [1] when the manipulated variable MV is updated as the set value SP is changed as shown in FIG. 4, for example. The proportional output ON history (flag) is forcibly set to OFF. By forcibly turning off the ON history (flag), for example, even when the time proportional output Ton has already been output within one cycle time, the generation of the time proportional output Ton within the cycle time is permitted again. Is done.

  If it is confirmed that the parameter TAT is [0] and the condition (trigger) for adjusting the time width of the time proportional output Ton is not particularly generated, the manipulated variable MV is not changed, and accordingly. Since it is not necessary to newly generate the time proportional output Ton, the count value TC is directly taken as the parameter STC, and the elapsed time from the start of the current cycle time to the present time is managed (step S7). And the process from step S9 mentioned later is performed.

On the other hand, when the parameter TAT is [1] and the condition (trigger) for adjusting the time width of the time proportional output Ton is satisfied, that is, the manipulated variable MV changes during one cycle time. When this is done, an operation amount MV * for generating a time proportional output Ton corresponding to the change in the operation amount MV is obtained based on the newly acquired operation amount MV <step S8>. That is, for example, when the manipulated variable MV increases with the change of the set value SP, in addition to the time proportional output Ton that has already been output, a time proportional output Ton having a time width corresponding to the increased amount is generated. The value of the parameter STC is added to the newly acquired operation amount MV, and the value of the parameter TR indicating the time width of the time proportional output Ton output in the past is subtracted. MV * = MV + STC−TR
Then, the operation amount MV * of the time proportional output to be newly generated is obtained <Step S8>.

  This process is performed from the start of this cycle time so that a new time proportional output Ton is generated by comparison with the count value (counter value) TC described above using the time when the manipulated variable MV is changed as a trigger. By adding the value of the parameter STC, which is the elapsed time until the operation amount MV is changed, the elapsed time is corrected with respect to the counter value TC. However, when the value corrected in this way is compared with the counter value TC described above to generate a new time proportional output Ton, the time width corresponds to the changed operation amount MV. Therefore, a correction amount corresponding to the amount of change in the manipulated variable MV is obtained by subtracting the time width (parameter TR) of the time proportional output Ton already output in the cycle time from the value [MV + STC] corrected by adding the parameter STC. Is calculated as [MV + STC-TR]. Then, the operation amount MV * obtained by such processing is used for comparison with the counter value TC described above.

  Thereafter, it is determined whether or not the ON history of the time proportional output is ON [1], or whether or not the above-described count value TC exceeds the manipulated variable MV (or MV *) <step S9>. When the ON history of the time proportional output is OFF [0] and the manipulated variable MV (or MV *) exceeds the count value TC, the condition for outputting the time proportional output Ton is satisfied. The output Ton is turned on and output (step S10), and the ON history of the time proportional output is turned on [1] (step S11). Then, the value of the parameter STC described above is updated to manage the on-time (duration time) of the time proportional output Ton (step S12).

  On the other hand, when the ON history of the time proportional output is ON [1], or when the above-described count value TC exceeds the manipulated variable MV / MV *, that is, the manipulated variable MV / MV * is less than the count value TC. Means that the condition for outputting the time proportional output Ton is not satisfied. Therefore, in this case, first, the time proportional output Ton is turned off, and the output is stopped <step S13>. Then, it is determined whether or not the time proportional output Ton is on [1] in the previous processing routine and the time proportional output Ton is off [0] in the current processing routine <step S14>.

  When the time proportional output Ton is turned off for the first time in the current processing routine, the parameter TR indicating the cumulative ON time of the time proportional output Ton described above is added to the parameter indicating the total output time of the current time proportional output Ton. The parameter TR is updated by adding TSC <step S15>. Then, the parameter TSC is initialized to [0] <Step S16>. Then, after the initialization of the parameter TSC, or when it is determined in step S14 described above that the time proportional output Ton is also on in the previous processing routine, the above-described count value TC is newly set to the parameter STC. And the elapsed time for which the time proportional output Ton is on is updated from the start time of the cycle time (step S17).

  By sequentially executing such a processing routine, when the operation amount MV is changed during one cycle time, the change amount is caused to follow the change of the operation amount MV with the change point of the operation amount MV as a trigger. A time proportional output Ton having a time width corresponding to is additionally generated. Specifically, after comparing the operation amount MV with the counter value TC and outputting a time proportional output Ton having a time width corresponding to the operation amount MV, when the operation amount MV is changed within the cycle time, A time-proportional output Ton having a time width corresponding to the change amount is newly generated and output using the change time point as a trigger. As a result, the total output time of the time proportional output Ton in the cycle time becomes equivalent to the changed manipulated variable MV, and it is promptly accompanied by the change of the manipulated variable MV regardless of the cycle time period. The time proportional output Ton is corrected.

  Thus, according to the time proportional control device described above, even if the control target temperature (target set value SP) 12 is changed, the changed control target temperature (target set value SP) 12 and the temperature of the control target 20 (control value PV). ) Since the operation of the cooler 21 can be quickly controlled according to the deviation from 13, the control response delay can be eliminated and a desired control result can be obtained with good followability. In addition, by adding a simple control algorithm that additionally generates a time proportional output Ton having a time width corresponding to the amount of change in the manipulated variable MV, the control responsiveness of the cooler 21 is maintained while maintaining the control specifications (cycle time). Can be improved.

  That is, according to the present invention, when the target set value SP is changed, as shown in FIG. 5 in which the response characteristic X by the time proportional control according to the present invention is compared with the response characteristic Y by the conventional time proportional control. Since a new time proportional output Tc is promptly generated, it is possible to control the control target without time delay and to quickly follow the new target set value SP. Therefore, the responsiveness with respect to the change of the target set value SP can be improved.

  By the way, when temperature control of the controlled object 20 is performed, the cooling capacity of the cooler 21 and the heating capacity of the heater (heater) may be used in combination. In this case, for example, as shown in FIG. 6, the PID output given as the operation amount MV of 0 to 100% is set to the operation amount MVheat for heating control of 0 to 100% with the boundary of 50%, and 0 to 100%. The operation amount MVcool for cooling control is converted to MVcool, and the heater and the cooler are selectively operated according to these operation amounts MVheat and MVcool. Even in this case, for example, as shown in FIG. 7, the time proportional outputs Th and Tc are obtained according to the operation amounts MVheat and MVcool, respectively, as shown in FIG. The heater and cooler may be controlled on and off.

  However, as described above, the time proportional control for the heater is performed in a short cycle, and only the time proportional control for the cooler 21 is performed in a long cycle. Therefore, the delay in the control response becomes a problem mainly due to the time proportional control with respect to the cooler 21. Therefore, when the time proportional output is changed with the large change in the operation amount MV as described above, the cooler 21 is changed. It is sufficient to control only the time proportional output on the side.

  Further, when performing temperature control using such a heater and a cooler together, if the PID output changes in the vicinity of 50%, the operation amount MV is specifically heated at 55%. When the operation amount MV changes to 45% from the state where the cooler is in operation, and it is necessary to operate the cooler 21 instead of the heater, the cooler 21 becomes 0 It is necessary to operate quickly from a resting state with a% time proportional output Ton. Even in such a situation, according to the time proportional control device of the present invention, the cycle time of the time proportional output to the cooler 21 is reset as described above in accordance with a large change in the manipulated variable MV. When the temperature changes from heating to cooling, the cooler 21 can be quickly operated by time proportional control. Therefore, it is possible to effectively prevent a delay in switching the control mode and obtain a desired control result without delay.

  Furthermore, by providing the cycle time reset function described above, for example, when performing auto-tuning as disclosed in Patent Document 2 described above, even if the execution timing is in the middle of the time proportional cycle, the time proportional output is performed. Can be changed and set to 100% without delay, so that it is possible to effectively perform auto-tuning.

  The present invention is not limited to the embodiment described above. For example, it goes without saying that the present invention can be similarly applied to the case where the control object other than the above-described temperature is subjected to time proportional control. Needless to say, the algorithm for newly generating the time proportional output Ton when the manipulated variable MV is changed can be variously modified. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

The schematic block diagram of the temperature control system using the time proportional control apparatus which concerns on one Embodiment of this invention. The timing diagram which shows the control form of the time proportional output in the time proportional control apparatus shown in FIG. The figure which shows the production | generation control procedure of the time proportional output in the time proportional control apparatus shown in FIG. The figure which shows the change process of the control parameter at the time of change of the operation amount MV. The figure which shows the effect of the time proportional control which concerns on this invention in contrast with a prior art example. The figure which shows the relationship between the PID output in the temperature control system which used the heater and the cooler together, and the operation amount for heating and cooling. The figure which shows the principal part schematic structure of the time proportional control apparatus in the temperature control system which used the heater and the cooler together.

Explanation of symbols

10 Control unit (Time proportional control device)
DESCRIPTION OF SYMBOLS 11 Operation part 14 PID control part 15 Time proportional output part 16 Output control part 20 Control object 21 Cooler 22 Temperature sensor

Claims (3)

A time-proportional output that is turned on every predetermined cycle is given to a controller that is turned on / off to change the state of the controlled object, and the controller is turned on for the on-time of the time-proportional output. with operating, a time proportional controller for controlling so that the difference between the value indicating the state of the control target value and the controlled object the on-time of the time-proportional output for said control object becomes zero,
When the control target value is changed within the cycle time defined by the predetermined period, the deviation changed with the change of the control target value at the time of change of the control target value is set to zero. While newly obtaining the on-time of the time proportional output,
Compare the newly determined ON time of the time proportional output with the ON elapsed time of the time proportional output already output in the current cycle time,
When the newly determined on-time is longer than the on-elapsed time, the difference between the on-time and the on-elapsed time is obtained, and the time proportional output of the on-time that compensates for the difference in the remaining period of the current cycle time The time proportional control device further comprises means for newly generating the control target value as a base point . The controlled object is a temperature controlled by a cooler as the controller,
The time proportional control device according to claim 1, wherein the time proportional output includes a signal defining an ON time of the cooler within the one cycle time . The controlled object is a temperature controlled by a cooler and a heater as the controller,
The time proportional output, said heating in the second period defining said signal defines an ON time of the cooler in the first period for defining the control cycle of the cooler or the control period of the heater, 2. The time proportional control device according to claim 1, wherein the time proportional control device is alternatively generated as a signal defining the on-time of the device.

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