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IDEC OPENNET User Manual
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IDEC OPENNET User Manual

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April 22, 2002
O
N
C
PEN
ET
ONTROLLER
PID I
NSTRUCTION
Buy: www.ValinOnline.com | Phone 844-385-3099 | Email: CustomerService@valin.com

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Summary of Contents for IDEC OPENNET

  • Page 1 April 22, 2002 ONTROLLER PID I NSTRUCTION Buy: www.ValinOnline.com | Phone 844-385-3099 | Email: CustomerService@valin.com...
  • Page 2 • Special technical knowledge about the PID control is required to use the PID function of the Warning . Use of the PID function without understanding the PID control may cause OpenNet Controller to perform unexpected operation, resulting in disorder of the control sys- OpenNet Controller tem, damage, or accidents.
  • Page 3 PID I NSTRUCTION Source Operand S1 (Control Register) Store appropriate values to data registers starting with the operand designated by S1 before executing the PID instruction as required, and make sure that the values are within the valid range. Operands S1+0 through S1+2 are for read only, and operands S1+23 through S1+26 are reserved for the system program.
  • Page 4 PID I NSTRUCTION S1+0 Process Variable (after conversion) When the linear conversion is enabled (S1+4 set to 1), the data register designated by operand S1+0 stores the linear con- version result of the process variable designated by operand S4. The process variable (S1+0) takes a value between the lin- ear conversion minimum value (S1+6) and the linear conversion maximum value (S1+5).
  • Page 5 PID I NSTRUCTION S1+3 Operation Mode When the start input for the PID instruction is turned on, the CPU module checks the value stored in the data register des- ignated by S1+3 and executes the selected operation. The selection cannot be changed while executing the PID instruction. 0: PID action The PID action is executed according to the designated PID parameters such as proportional gain (S1+7), integral time (S1+8), derivative time (S1+9), and control action (S2+0).
  • Page 6 PID I NSTRUCTION Example: When the transducer connected to the analog input module has an input range of –50°C through +199°C, set the following values. The temperature values are multiplied by 10 to calculate the process variable. Control mode (S1+4): 1 (enable linear conversion) Linear conversion maximum value (S1+5): 1990 (199.0°C)
  • Page 7 PID I NSTRUCTION When the derivative time is set to a large value, the derivative action becomes large. When the derivative action is too large, hunching of a short period is caused. While the PID action is in progress, the derivative time value can be changed by the user. S1+10 Integral Start Coefficient The integral start coefficient is a parameter to determine the point, in percent of the proportional term, where to start the integral action.
  • Page 8 PID I NSTRUCTION Example – Sampling period: 80 msec, Scan time: 60 msec (Sampling period > Scan time) 1 scan 1 scan 1 scan 1 scan 1 scan 1 scan 1 scan 1 scan 60 msec 60 msec 60 msec 60 msec 60 msec 60 msec...
  • Page 9 PID I NSTRUCTION S1+16 Output Manipulated Variable Upper Limit The value contained in the data register designated by operand S1+16 specifies the upper limit of the output manipulated variable (S1+1) in two ways: direct and proportional. S1+16 Value 0 through 100 When S1+16 contains a value 0 through 100, the value directly determines the upper limit of the output manipulated vari- able (S1+1).
  • Page 10 (S1+9), and control action (S2+0) automatically. The uses the step response method to execute OpenNet Controller auto tuning. To enable auto tuning, set four parameters for auto tuning before executing the PID instruction, such as AT sampling period (S1+19), AT control period (S1+20), AT set point (S1+21), and AT output manipulated variable (S1+22).
  • Page 11 PID I NSTRUCTION Source Operand S2 (Control Relay) Turn on or off appropriate outputs or internal relays starting with the operand designated by S2 before executing the PID instruction as required. Operands S2+4 through S2+7 are for read only to reflect the PID and auto tuning statuses. Operand Function Description...
  • Page 12 PID I NSTRUCTION S2+2 Output Manipulated Variable Limit Enable The output manipulated variable upper limit (S1+16) and the output manipulated variable lower limit (S1+17) are enabled or disabled using the output manipulated variable limit enable control relay designated by operand S2+2. To enable the output manipulated variable upper/lower limits, turn on S2+2.
  • Page 13 For example, when the analog input module is mounted in the first slot from the CPU module among all functional mod- ules such as analog I/O and OpenNet interface modules (not including digital I/O modules) and when the analog input is connected to channel 0 of the analog input module, designate link register L100 as source operand S4.
  • Page 14 PID I NSTRUCTION Destination Operand D1 (Manipulated Variable) The data register designated by destination operand D1 stores the manipulated variable of –32768 through 32767 calcu- lated by the PID action. When the calculation result is less than –32768, D1 stores –32768. When the calculation result is greater than 32767, D1 stores 32767.

  • Page 15: Application Example

    PID I NSTRUCTION Application Example This application example demonstrates a PID control for a heater to keep the temperature at 200°C. In this example, when the program is started, the PID instruction first executes auto tuning according to the designated AT parameters, such as AT sampling period, AT control period, AT set point, and AT output manipulated variable, and also the temperature data inputted to the analog input module.

  • Page 16: System Setup

    PID I NSTRUCTION System Setup Relay Output Module Analog Input Module CPU Module FC3A-AD1261 FC3A-R161 POWER ERROR HSC OUT Transducer –50° to 500°C Fuse Thermocouple 24V DC Output Q1 High Alarm Light Heater Output Q0 Heater Power Switch Digital Output from Analog Input Module vs. Process Variable after Conversion Process Variable after Conversion (S1+0) Linear Conversion Maximum Value (S1+5): 5000 (500°C) High Alarm Value (S1+14): 2500 (250°C)
  • Page 17 PID I NSTRUCTION Ladder Program The ladder diagram shown below describes an example of using the PID instruction. The user program must be modified according to the application and simulation must be performed before actual operation. When input I0 is turned on, 0 is stored to 27 data registers MOV(W) S1 –...
  • Page 18 PID I NSTRUCTION Ladder Program (continued) While monitor input I1 is on, the temperature is monitored. CMP>=(W) S1 – S2 – D1 – When the temperature is higher than or equal to 250°C, L100 M10 is turned on. 4000 × 250/1300 = 769.23 When M10 is on while monitor input I1 is on, Q0 (heater power switch) is forced off and Q1 (high alarm light) is forced on.