ICS Regent ® PD-6044 Continuous Control Package for W INTERPRET Continuous Control Function Block for PID Control (T3834) Issue 1, March, 06 The Continuous Control package for WINTERPRET is an add-in software package which allows the user to create continuous control function blocks for Regent application programs. When installed on the PC, the continuous control package is seamlessly integrated with the base WINTERPRET software.
Continuous Control Package for WINTERPRET (T3834) distribution disk in order to run the setup procedure to install the Continuous Control package. To install the Continuous Control package, use the following sequence: 1. Insert the WINTERPRET base package distribution disk into drive A: or B: 2. Start Windows (if it isn’t already running). 3. Choose Run from the Program Manager’s File menu. 4. Type a:\setup.exe in the text box. (if you inserted the WINTERPRET base package disk in drive B: type b:\setup.exe.
Continuous Control Package for WINTERPRET (T3834) Shared variables are data values internal to the Regent that may be commonly referenced by all function blocks of any application program. Use the Shared Variable Editor to define the shared variables in the Regent. Each controller may have up to 10 alarms associated with it, each of which may be defined by assigning a name. Continuous Control is used to maintain a measured process signal at a predetermined value.
Continuous Control Package for WINTERPRET (T3834) Proportional Control Making the controlled output a continuous variable that is proportional to the process error provides a precise means of controlling the process. The process error is the difference between the setpoint and the process variable.
Continuous Control Package for WINTERPRET (T3834) TS = loop sample time Tl = reset time The amount of reset action is defined by the integral time constant: reset time (Tl). The reset time represents the time required for the integral sum to equal the proportional action. This assumes that the process error remains constant. Thus a smaller value for reset time creates more reset action. A larger value for reset time creates less reset action.
Continuous Control Package for WINTERPRET (T3834) The amount of derivative action is defined by the derivative time constant: rate time (TD). The rate time is the time period over which the error rate of change is extrapolated and a control action is based. A larger rate time causes more derivative action. A smaller rate time causes less derivative action. Derivative action is never used alone but only in conjunction with proportional or both proportional and integral.
Continuous Control Package for WINTERPRET (T3834) Using the Continuous Control (PID) Editor Continuous Control function blocks are created using Add Function Block or Insert Function Block from the Program Editor. After you have created a new function block the Continuous Control Editor window is opened as shown in Figure 1. Figure 1. The Continuous Control (PID) Editor Window. The Continuous Control Editor lets you create and edit continuous control function blocks.
Continuous Control Package for WINTERPRET (T3834) File Menu The File Menu gives you access to the standard function block file commands which include: Save Function Block, Revert to Last Saved, Compile, View Error Messages, Edit Function Block Description, Edit Function Block Details, Print Function Block, Print Setup, Log Off and Exit. For more information on all of these commands refer to Commands Common to all Function Blocks in Section 5 of the Regent User’s Guide.
Continuous Control Package for WINTERPRET (T3834) Figure 2.
Continuous Control Package for WINTERPRET (T3834) Low Scaling Value The low engineering value corresponding to the analog value of 0. The low scaling value must always be less than the high scaling value (-32768 < x < high scaling value). PID Controller Name The name of the control loop. Follows the same format as tag names. The controller name must not be the name of a variable. PID Controller Title A controller may be given a title containing up to 40 characters of descriptive text.
Continuous Control Package for WINTERPRET (T3834) Direct/Reverse (Control Direction) Determines the control output gain. In Direct mode, the control output increases as the gain increases (direct acting or positive gain). In Reverse mode, the control output decreases as the gain increases (reverse acting or negative gain). The default value is Direct. Sample Time The sample time is the time between loop calculations to determine how often the controller is solved. May be in the range 0.01 to 650 seconds.
Continuous Control Package for WINTERPRET (T3834) Setpoint High Limit The setpoint high limit is the largest value that the setpoint can become from the actions of bumpless transfer or cascade. May be in the range Setpoint Low < x < Scale High. There is no default value. Setpoint Tracking Select Yes or No. If Yes is selected, the setpoint becomes the process variable value upon mode change from manual to automatic (bumpless transfer).
Continuous Control Package for WINTERPRET (T3834) Error Rate The maximum rate of change of error allowed for the loop calculation (in engineering units). May be in the range 0 < x < Scaling Range. There is no default value. Differential Applicable only to the derivative term, calculations may be based on Error or Process differential. The default value is Error. Error SQR P Enables proportional action to be based on error (No) or error squared (Yes). The default value is No.
Continuous Control Package for WINTERPRET (T3834) The Alarms dialog is launched from the Controller dialog by pressing the ‘Alarms...’ button. All alarms are optional if required, an alarm is specified by entering a variable name. The same name may be used for alarms in different controllers within a function block, but a warning message will be displayed on compilation. Figure 3. The Continuous Control (PID) Alarms Dialog Box.
Continuous Control Package for WINTERPRET (T3834) Low Integral Windup Alarm On if the integral error is smaller than the low integral value. High Integral Windup Alarm On if the integral alarm error is larger than the high integral value. Maximum Error Alarm On when the error term is larger than the maximum error. Maximum Error Rate Alarm On when the rate of change for the error exceeds the maximum error rate. Setpoint Low Alarm On when the setpoint is lower than the setpoint low limit.
Continuous Control Package for WINTERPRET (T3834) Search Menu From the Search Menu the user can select the Go to Controller, Find and Find Next commands. Go To Controller The Go to Controller command lets you quickly move to different entries in the controller list. Figure 4. Go to Controller Dialog Box Entry Number: Enter the controller number that you want to go to. Go: Choose Go to move to the controller number that you entered in the Entry Number text box.
Continuous Control Package for WINTERPRET (T3834) Find The Find command can be used to locate variables in the controller list. Figure 5. The Find Dialog Box Find What text box: Type in the source name of the entry or character string you want to search for. The Find What text box retains the name of the last entry or character string that was searched for. Use the Find Next command button or press F3 to repeat the search.
Continuous Control Package for WINTERPRET (T3834) descriptions and whether the search should be casesensitive. Find Next The Find Next command searches for the next occurrence of whatever name (or character string) was previously searched for using the Find command. Options Menu The Options Menu allows you to enable and disable the Prompt for Delete option common to all delete operations used in WINTERPRET. Window Menu The Window menu commands are standard throughout all WINTERPRET windows.
Continuous Control Package for WINTERPRET (T3834) Using the Continuous Control (PID) Monitor The Continuous Control (PID) Monitor displays the current status of the continuous control function block defined in your system. When you have selected a Continuous Control function block in the Program Monitor window and chosen the Monitor command from the Control Menu, the Continuous Control Monitor window is opened as shown below. Figure 6. Continuous Control Monitor Window.
Continuous Control Package for WINTERPRET (T3834) Control Menu The Control Menu provides certain commands that are common to all function block monitors. These include Run, Stop and Scan commands to control the execution status of the entire application program. For descriptions of these commands see Commands Common to all Function Block Monitors in Section 7, Loading, Monitoring and Testing Application Programs in the Regent User’s Guide.
Continuous Control Package for WINTERPRET (T3834) Note: In order to tune a controller while it is running in a Regent, each parameter to be tuned should be defined as a variable (shared variables may be defined with initial values, local variables may not). The Data Monitor should be used to change the values of the variables as required. Monitor Controller The Monitor Controller command displays the dialog box shown in Figure 8.
Continuous Control Package for WINTERPRET (T3834) Window Menu The Window menu commands are standard throughout all WINTERPRET windows. For more information on using the Window menu commands see Commands Common to all WINTERPRET Windows in Section 3, Installing the WINTERPRET Application of the Regent User’s Guide. Help Menu The Help menu commands are standard throughout all WINTERPRET windows.
Continuous Control Package for WINTERPRET (T3834) P D -6044 M a r c h , 0 6 23
