CPM2A_PROGRAMMING MANUAL (W353-E1-2) (986750), страница 70
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The strength of the integral action is indicated by theintegral time, which is the time required for the manipulated variable of the integral action to reach the same level as the manipulated variable of the proportional action with respect to the step deviation, as shown in the following illustration.The shorter the integral time, the stronger the correction by the integral actionwill be. If the integral time is too short, the correction will be too strong and willcause hunting to occur.Integral ActionStep responseDeviationManipulatedvariablePi Action and Integral TimeStep responseDeviationPI actionI actionP actionManipulatedvariableTi: Integral time399Section 7-18Data Control InstructionsDerivative Action (D)Proportional action and integral action both make corrections with respect to thecontrol results, so there is inevitably a response delay. Derivative action compensates for that drawback.
In response to a sudden disturbance it delivers alarge manipulated variable and rapidly restores the original status. A correctionis executed with the manipulated variable made proportional to the incline (derivative coefficient) caused by the deviation.The strength of the derivative action is indicated by the derivative time, which isthe time required for the manipulated variable of the derivative action to reachthe same level as the manipulated variable of the proportional action with respect to the step deviation, as shown in the following illustration. The longer thederivative time, the stronger the correction by the derivative action will be.Derivative ActionStep responseDeviationManipulatedvariablePD Action and Derivative TimeRamp responseDeviationPD actionP actionD actionManipulatedvariableTd: Derivative timePID ActionPID action combines proportional action (P), integral action (I), and derivativeaction (D). It produces superior control results even for control objects with deadtime.
It employs proportional action to provide smooth control without hunting,integral action to automatically correct any offset, and derivative action to speedup the response to disturbances.Step Response of PID Control Action OutputStep responseDeviationPID actionI actionP actionD actionManipulatedvariableRamp Response of PID Control Action OutputRamp responseDeviationPID actionI actionP actionManipulatedvariable400D actionSection 7-18Data Control InstructionsDirection of ActionWhen using PID action, select either of the following two control directions. Ineither direction, the MV increases as the difference between the SV and the PVincreases.• Forward action: MV is increased when the PV is larger than the SV.• Reverse action: MV is increased when the PV is smaller than the SV.Forward ActionReverse ActionProportionalbandProportionalband100%100%ManipulatedvariableManipulatedvariable0%0%LowtemperatureAdjusting PID ParametersHighSV temperatureLowtemperatureHightemperatureSVThe general relationship between PID parameters and control status is shownbelow.• When it is not a problem if a certain amount of time is required for stabilization(settlement time), but it is important not to cause overshooting, then enlargethe proportional band.Control by measured PIDSVWhen P is enlarged• When overshooting is not a problem but it is desirable to quickly stabilize control, then narrow the proportional band.
If the proportional band is narrowed toomuch, however, then hunting may occur.When P is narrowedSVControl by measured PID• When there is broad hunting, or when operation is tied up by overshooting andundershooting, it is probably because integral action is too strong. The huntingwill be reduced if the integral time is increased or the proportional band is enlarged.Control by measured PID(when loose hunting occurs)SVEnlarge I or P.401Section 7-19Comparison Instructions• If the period is short and hunting occurs, it may be that the control system response is quick and the derivative action is too strong.
In that case, set the derivative action lower.Control by measured PID(when hunting occurs in a short period)SVLower D.FlagsER:There is an error in the parameter settings.The cycle time is more than twice as long as the sampling period, soPID(––) cannot be executed accurately. PID(––) will be executed in thiscase.P1 and P1+32 are not in the same area or a parameter setting is notwithin the specified range.Indirectly addressed DM word is non-existent. (Content of *DM word isnot BCD, or the DM area boundary has been exceeded.)CY:ON when PID processing is being performed.
(OFF when the samplingperiod has not elapsed.)7-19 Comparison Instructions7-19-1 COMPARE – CMP(20)Ladder SymbolsOperand Data AreasCp1: First compare wordCMP(20)IR, SR, AR, DM, HR, TC, LR, #Cp1Cp2: Second compare wordCp2IR, SR, AR, DM, HR, TC, LR, #LimitationsWhen comparing a value to the PV of a timer or counter, the value must be inBCD.DescriptionWhen the execution condition is OFF, CMP(20) is not executed. When theexecution condition is ON, CMP(20) compares Cp1 and Cp2 and outputs theresult to the GR, EQ, and LE flags in the SR area.PrecautionsPlacing other instructions between CMP(20) and the operation which accessesthe EQ, LE, and GR flags may change the status of these flags.
Be sure to access them before the desired status is changed.FlagsER:EQ:LE:GR:Indirectly addressed DM word is non-existent. (Content of *DM word isnot BCD, or the DM area boundary has been exceeded.)ON if Cp1 equals Cp2.ON if Cp1 is less than Cp2.ON if Cp1 is greater than Cp2.Flag402AddressC1 < C2C1 = C2C1 > C2GR25505OFFOFFONEQ25506OFFONOFFLE25507ONOFFOFFSection 7-19Comparison InstructionsThe following example shows how to save the comparison result immediately.
Ifthe content of HR 09 is greater than that of DM 0000, 20000 is turned ON; if thetwo contents are equal, 20001 is turned ON; if content of HR 09 is less than thatof DM 0000, 20002 is turned ON. In some applications, only one of the threeOUTs would be necessary, making the use of TR 0 unnecessary. With this typeof programming, 20000, 20001, and 20002 are changed only when CMP(20) isexecuted.Example:Saving CMP(20) Results00000TR0CMP(20)HR 09DM 00002550520000Greater Than2550620001Equal20002Less Than25507AddressInstruction000000000100002LDOUTCMP(20)000000TRHRDM0000300004AddressOperandsANDOUT0000500006000070000800009000100900002550520000InstructionLDANDOUTLDANDOUTOperandsTRTR02550620001025507200027-19-2 TABLE COMPARE – TCMP(85)Operand Data AreasCD: Compare dataLadder SymbolsIR, SR, DM, HR, TC, LR, #TCMP(85)@TCMP(85)CDCDTBTBRRTB: First comparison table wordIR, SR, DM, HR, TC, LRR: Result wordIR, SR, DM, HR, TC, LRLimitationsDM 6144 to DM 6655 cannot be used for R.DescriptionWhen the execution condition is OFF, TCMP(85) is not executed.
When theexecution condition is ON, TCMP(85) compares CD to the content of TB, TB+1,TB+2, ..., and TB+15. If CD is equal to the content of any of these words, thecorresponding bit in R is set, e.g., if the CD equals the content of TB, bit 00 isturned ON, if it equals that of TB+1, bit 01 is turned ON, etc. The rest of the bits inR will be turned OFF.FlagsER:The comparison table (i.e., TB through TB+15) exceeds the data area.Indirectly addressed DM word is non-existent. (Content of *DM word isnot BCD, or the DM area boundary has been exceeded.)403Section 7-19Comparison InstructionsThe following example shows the comparisons made and the results providedfor TCMP(85).
Here, the comparison is made during each cycle when IR 00000is ON.Example00000TCMP(85)HR 00AddressInstruction0000000001LDTCMP(85)DM 0000HR00Upper limits0210DM 0000DM 0001DM 0002DM 0003DM 0004DM 0005DM 0006DM 0007DM 0008DM 0009DM 0010DM 0011DM 0012DM 0013DM 0014DM 0015Compare the data in IR 001with the given ranges.00000HRDM216CD: HR 00Operands000000216R: 2160100020002100400050006000210080009001000021012001300140002101600IR 21000IR 21001IR 21002IR 21003IR 21004IR 21005IR 21006IR 21007IR 21008IR 21009IR 21010IR 21011IR 21012IR 21013IR 21014IR 2101500100010001000107-19-3 BLOCK COMPARE – BCMP(68)Operand Data AreasCD: Compare dataLadder SymbolsIR, SR, AR, DM, HR, TC, LR, #BCMP(68)@BCMP(68)CDCDCBCBRRCB: First comparison block wordIR, SR, DM, HR, TC, LRR: Result wordIR, SR, AR, DM, HR, TC, LRNote BCMP(68) is an expansion instruction for the SRM1(-V2).
The function code 68is the factory setting and can be changed for the SRM1(-V2) if desired.LimitationsEach lower limit word in the comparison block must be less than or equal to theupper limit.DM 6144 to DM 6655 cannot be used for R.404Section 7-19Comparison InstructionsDescriptionWhen the execution condition is OFF, BCMP(68) is not executed. When theexecution condition is ON, BCMP(68) compares CD to the ranges defined by ablock consisting of CB, CB+1, CB+2, ..., CB+31. Each range is defined by twowords, the first one providing the lower limit and the second word providing theupper limit. If CD is found to be within any of these ranges (inclusive of the upperand lower limits), the corresponding bit in R is set.
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