Overview

The TwinCAT temperature controller is a universally applicable PLC block for monitoring and controlling a wide variety of temperature-dependent processes. The controller can be operated in

• automatic (closed loop) and
• manual (open loop)

modes.

The control value can be accessed in digital or analogue form. The digital control value is pulse width modulated (PWM). A two-point or three-point output is also available. The control value is limited to the permitted maximum and minimum values.

The set value is also limited to permitted minimum and maximum values, and can also be ramped. A bit is available in the interface to the block that provides easy switching from the set value to a standby set value. A soft start can be parameterised to support "heater baking". This involves the set value (optionally ramped) being initially set to a low value, remaining there for a certain time, then being changed to the true set value (again optionally ramped).

The actual value can be digitally filtered.

The control algorithm is PID-based. An additional pre-regulator can be inserted in order to minimise overshoot.

The controller has a variety of parameterisable monitoring functions. There is

• tolerance band monitoring (two different tolerance bands),
• absolute value monitoring,
• sensor monitoring (open, back voltage, reverse) and
• monitoring of the heating current (open, short circuit, leakage current).

There is an algorithm for determination of optimal controller parameters that greatly simplifies the process of commissioning the controller. This algorithm evaluates a step, and uses a method of inflectional tangents to determine the maximum speed and delay time of the loop. This data allows a controller to be specified according to the rules of Chien, Hrones and Reswick. The parameters for the pre-controller are also determined here. If the controller parameters are already known, then the controller can also be operated using these externally supplied parameters.

Commissioning the controller in stages

Documentation of the Function Block and the structures.

For compatibility reasons the documentation of the old Temperature Controller Function Block and structure is also included in this document.