Standard PID Control

Loadable function blocks for small or medium- scale closed-loop control tasks

Description

Standard PID Control is a pre-configured controller structure that is easily adapted by connecting or disconnecting functions to and from the control process. The controller structure is implemented in a function block to be loaded into the CPU. The structure is graphically configured with the appropriate parameterization software.

Standard PID Control is implemented wherever small or medium- scale closed-loop control tasks are needed: in temperature control, pressure control, flow control as well as fill-level control. Standard PID Control is particularly well suited to applications that had previously been automated with compact controllers.

Standard PID Control contains the following pre-configured examples:

  • Step controller with path simulation

  • Continuous-action controller with path simulation

  • Multi-loop ratio control

  • Blending control

  • Cascade control

Pulse controller

The pulse controller is combined with the continuous-action controller in the same block, including conversion to a pulse/pause signal (pulse shaper). This simplifies parameterization and commissioning of the pulse controller.

It is also possible to independently adjust the sampling time of the controller and the period duration of the pulse shaper. As a result the period duration can be set longer than the sampling time.

  • The advantage of a shorter sampling time is found in the rapid response of the controller to faults and operating commands.

  • The longer period duration, however, protects the final controlling element due to the lower switching frequency. The oscillation of actual values is suppressed because the effective cycle duration is automatically shortened.

  • Another advantage is the reduced loading on the CPU because the pulse shaper can be used at fewer frequent intervals.

  • The example provided for a pulse controller with a 3-point output "HEATING - OFF - COOLING" simplifies commissioning of the temperature control.

Step controller

An adjustment algorithm ensures that for the same control accuracy, step controllers can have up to 50% fewer switching actions as conventional step controllers. This protects the connected final control elements and increases their service life considerably.

The following functions can be selected for manual/automatic changeover by setting parameters:

  • Bumpless manual/automatic changeover

  • Bumpless manual/automatic changeover with a corresponding step change in controller output for faster compensation of the system deviation

  • Manual value follow-up in automatic mode

User-friendly parameterization

Parameterization is graphically supported with a controller structure display, loop display, graphic plotter and controller optimization function. The clearly comprehensible controller structure makes it easy to connect and disconnect functions using software switches. Parameter changes can be performed in the RUN state of the CPU or when the graphic plotter or loop display are active.

Test functions

Commissioning and diagnostics have been simplified thanks to comprehensive test functionality. Similiar to FM 355/455 closed-loop control modules and Modular PID Control, a control loop display is available with a bar chart and a graphic plotter for recording the signal charts. The controller structure, the entered parameters and their effects on the result can be simultaneously displayed. The curves plotted with the graphic plotter can be archived in files and subsequently processed with MS Excel, for example.

Test functions

Controller optimization

The parameterization software contains a self-tuning function that can be used to adjust the controller extremely quickly without the need for exact knowledge of the controlled system. The process is activated with a step change in controller output or a setpoint change. During the transient response, the process values are automatically acquired and displayed. The program calculates a mathematical model of the controlled system from the values and determines the most favorable controller parameters for PI and PID controllers according to the optimum value.

There is a choice of two different transient responses for controller self-optimization:

  • Response of the control loop with overshoot of up to 10%

  • Transient response without overshoot

For online self-optimization, the PID Self Tuner is recommended