PLC-API Requirements 5.4.6 FB_CTRL_PARAMETER_SWITCH This function block can be used to switch the parameter set used by FB_CTRL_PID_SPLITRANGE. Behaviour of the output: Description of the function block: This function block is used to switch over the parameter set used by FB_CTRL_PID_SPLITRANGE . This function block is particularly intended to switch the parameter sets of controllers that can use two actuators to heat and to cool, and to set the limits for the controller. The time tMinWaitTime is specified as an input parameter.
At least this time must elapse when switch-over is requested to allow for the parameter range to be changed, and for the controller limits set in such a way that it is possible to switch from heating operation to cooling operation. The intention of this is to prevent the operation mode being changed immediately simply because the controller overshoots slightly. For heating operation, the parameter range eCTRL_PARAMETER_RECORD_HEATING = heating is selected, while for cooling operation the parameter range is eCTRL_PARAMETER_RECORD_COOLING = cooling . The controller's parameter sets must be specified in accordance with this arrangement.
The request for a changeover itself is provided by a 2-point element (see image). The controller's output value, in other words the control value, should be used as the input value for the illustrated characteristic hysteresis curve. A request for changeover created by the hysteresis element must be present for at least the specified waiting time, so that the parameter range can be changed. TS4100 49 Version: 1.1 Development Environment Target System PLC libraries to include TwinCAT v2.8 PC (i386) TcControllerToolbox.lib TwinCAT v2.9 from Build 947 BC [} 10] TcControllerToolbox.lb6 TwinCAT v2.9 from Build 956 BX [} 10] TcControllerToolbox.lbx