General Information
In feeding systems, e.g. film feeding, slipping can occur due to faulty friction. This slippage is compensated for using the TB_SlipCtrl function module. For this purpose the actual velocity value of the encoder of the feed motor is compared to the actual velocity value of an additional encoder, which is situated directly on the material, e.g. film, via an encoder wheel.
Due to the highly suited control algorithm, it is possible to compensate for slippage up to approx. 50%. This occurs without any persistent control deviation.
The maximum influence regarding velocity can be limited with di_CtrlLim. Using the di_SlipPerc output, the current slippage can be monitored and, if necessary, responded to if the slippage is excessive, e.g. torn film or material backup.
The figure below shows how the function block behaves when the material speed (e.g. encoder wheel) is slower than the feed.
Then the di_Vel output is compensated in that its value is increased by the same amount, so that the material feed remains constant.
| Recommended task: | Event |
| Libraries used: | ARITHMETIC_xxbd00 or greater |
InOut Parameter
| none |
Input Parameter
| Marking: | Data type: | Description: |
|---|---|---|
| x_Enable | BOOL | TRUE:Activation of slippage control, output of the corrected velocity setpoint di_Vel = di_SetVel + correction. FALSE:Deactivation of slippage control; di_Vel = di_SetVel is output Control can be activated and deactivated any time during operation/while the drive is running. |
| di_SetVel | DINT | Velocity setpoint of the feed drive. The units of di_SetVel and di_ActVel must be the same. This is generally user units/Ts or e.g. 1/100th user units/Ts for upstream technology modules. Ts is the cycle time of the setpoint event task. |
| di_ActVel | DINT | Velocity actual value of additional encoder. The units of di_SetVel and di_ActVel must be the same. This is generally user units/Ts or e.g. 1/100th user units/Ts for upstream technology modules. Ts is the cycle time of the setpoint event task. |
| di_CtrlLim | DINT | Limit of velocity correction value in percent. If this input is not used, the default value 50 (%) is in effect, i.e. di_Vel is thus max. di_SetVel * 1.5. |
| i_Kp | INT | Proportional increase in slippage control. If the input is not used, the default value of 1 is in effect. The optimum value for Kp is 1. |
| u_SmoothNum | UINT | Smoothing of compensation. The value corresponds to the number of values over which smoothing occurs. If the input is not used, the default value of 20 is in effect, i.e. smoothing occurs over 20 values. |
| i_T_Cycle | INT | Call interval of the event task in which TB_SlipCtrl is called up; in ms. Valid values are 1 ms, 2 ms, 4 ms and 8 ms. |
Output Parameter
| Marking: | Data type: | Description: |
|---|---|---|
| x_Active | BOOL | TRUE:Slippage control active. FALSE:Slippage control not active. |
| di_Vel | DINT | Corrected setpoint velocity in the same unit as di_SetVel and di_ActVel! Ts is the cycle time of the setpoint event task. |
| di_SlipPerc | DINT | Current slippage in percent. Value used for display and/or monitoring. |
| di_CompPerc | DINT | Current compensation in percent. Value used for display and/or monitoring. |
| di_SlipUnits | DINT | Current slippage in units or 1/xth units. Value used for display, monitoring or as a measurement value for optimization. |