### SCUV – Step controller unit with velocity input

Block SymbolLicensing group: STANDARD

Function Description
The block SCUV substitutes the secondary position controller SCU in the step controller loop when the position signal is not available. The primary controller PIDU (or some of the derived function blocks) is connected with the block SCUV using the block inputs mv, dmv and SAT.

If the primary controller uses PI or PID control law ($\mathtt{\text{CWOI}}=\mathtt{\text{off}}$), then all three inputs mv, dmv and SAT of the block SCUV are sequentially processed by the special integration algorithm and by the three state element with parameters thron and throff (see the TSE block, use parameters $\mathtt{\text{ep}}=\mathtt{\text{thron}}$, $\mathtt{\text{epoff}}=\mathtt{\text{throff}}$, $\mathtt{\text{en}}=\mathtt{\text{-thron}}$ and $\mathtt{\text{enoff}}=\mathtt{\text{-throff}}$). Pulse outputs of the three state element are further shaped in such a way that the minimum pulse duration time dtime and minimum pulse break time btime are guaranteed at the block outputs UP and DN. The parameter RACT determines the direction of motor moving. Note, the velocity output of the primary controller is reconstructed from input signals mv and dmv. Moreover, if the deviation error of the primary controller with $\mathtt{\text{icotype}}=\mathtt{\text{4}}$ (working in automatic mode) is less than its dead zone ($\mathtt{\text{SAT}}=\mathtt{\text{on}}$), then the output of the corresponding internal integrator is set to zero.

The position pos of the valve is estimated by an integrator with the time constant trun. If signals from high and low limit switches of the valve are available, they should be connected to the inputs HS and LS.

If the primary controller uses P or PD control law ($\mathtt{\text{CWOI}}=\mathtt{\text{on}}$), then the deviation error of the primary controller can be eliminated by the bias ub manually. In this case, the control algorithm is slightly modified, the position of the motor pos is used and the proper settings of thron, throff and the tracking time constant tt are necessary for the suppressing of up/down pulses in the steady state.

There is also a group of input signals for manual control available. The manual mode is activated by the $\mathtt{\text{MAN}}=\mathtt{\text{on}}$ input signal. Then it is possible to move the motor back and forth by the MUP and MDN input signals. It is also possible to specify a position increment/decrement request by the mdv input. In this case the request must be confirmed by a rising edge (off$\to$on) in the DVC input signal.

The overall control function of the SCUV block is obvious from the following diagram:

The complete structures of the three-state controllers are depicted in the following figures:

Inputs

 mv Manipulated variable (controller output) double dmv Controller velocity output (difference) double ub Bias (only for P or PD primary controller) double SAT Internal integrator reset (connected to the SAT output of the primary controller) bool HS Upper end switch (detects the upper limit position of the valve) bool LS Lower end switch (detects the lower limit position of the valve) bool MUP Manual UP signal bool MDN Manual DN signal bool mdv Manual differential value (requested position increment/decrement with higher priority than direct signals MUP/MDN) double DVC Differential value change command (off$\to$on) bool MAN Manual or automatic mode bool off .. Automatic mode on ... Manual mode

Outputs

 UP The "up" signal bool DN The "down" signal bool pos Position output of motor simulator double MR Request to move the motor bool off .. Motor idle ($\mathtt{\text{UP}}=\mathtt{\text{off}}$ and $\mathtt{\text{DN}}=\mathtt{\text{off}}$) on ... Request to move ($\mathtt{\text{UP}}=\mathtt{\text{on}}$ or $\mathtt{\text{DN}}=\mathtt{\text{on}}$)

Parameters

 thron Switch-on value  $↓$0.0 $\odot$0.02 double throff Switch-off value  $↓$0.0 $\odot$0.01 double dtime Minimum width of the output pulse [s]  $↓$0.0 $\odot$0.1 double btime Minimum delay between two subsequent output pulses [s]  $↓$0.0 $\odot$0.1 double RACT Reverse action flag bool off .. Higher mv $\to$ higher pv on ... Higher mv $\to$ lower pv trun Motor time constant (determines the time during which the motor position changes by one unit)  $↓$0.0 $\odot$10.0 double CWOI Controller without integration flag bool off .. The primary controller has an integrator (I, PI, PID) on ... The primary controller does not have an integrator (P, PD) tt Tracking time constant  $↓$0.0 $\odot$1.0 double

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