PID Functional block with Digital O/P
I need to control one Digital control valve(DCV) who is having two Solenoid Coils one for upstream and one for downstream.
This controlling will be based on the flow and quantity of the fluid being filled in the Tank.
Flow will be having following phase.
1. Initial cut:- The flow will be less than 100 liter per minute, as if there is any leakage we can cross check.
2. After certain quantity like 10% of the preset the flow will ramp up to a high value.
3. This high flow will be maintained till 90% of the Preset.
4. After this ramp down process will start and flow will slow down till the 100% value of preset is delivered.
Now as we have analog input:- "Flow and Quantity being filled" and we need to control DCV.
How to acheive this function through PID block in Compact Control Builder M. Front end is Compact HMI.
Is there any PID block with single or doulbe digital output.
or is there any way to do this through PID block?
There is no system library for PID block compromising your requirement only way to achieve this develop your own custom compare real block to control Digital output.
else if you are using PCDevlib then there is default block available for PID controlling digital output based on the input v/s setpoint
The Standard Block for INC/DEC control is a "ThreePositionReal" found in Control Simple Lib. Connect the Output of the PID Controller to the In of the function block.
Note that there is a significant problem in the ThreePositionReal Block when used with valve feedback connected to FBPos. The block does not "pause" to allow the actuator time to move and settle before making another control action, hence the block will tend to "hunt" unless the Hysteresisis is overly large.
There are 2 solutions to this ...
1. Dont use Actuator Feedback. This is the default case when you have no valve position feedback. Set the ActPosT to be the time to go from 0 to Full Scale MV.
2. Force the Block to Simulate feedback while the Inc Or Dec Outputs are moving. This is suggested if you have an actual actuator position feedback. If INC or DEC is true, then FBPosConn should be set False. Delay Turning on FBPosConn until the "Settling Time" of the actuator has passed. Set the ActPosT to be the Time to move the actuator fro 0 to 100%.