User Manual

Control concept

Control concept and control blocks

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5.1 Control concept and control blocks

The Desigo control concept is a set a rules that determine in general terms the

principles governing all control, reporting and monitoring operations and the

switching interventions in the Desigo system. The rule applies to block-internal

control (priority array) and to functional interactions among participating

blocks.

This specifically deals with:

● Structure and design of control as function blocks

● The hierarchical assignment of the function blocks among themselves

● The function hierarchy within the control chain for the function blocks

● Processing operational and fault messages

● Interventions in monitoring functions

● Impact of emergency switching

The open loop control strategy is based on the exchange of predefined signals

between functional units. Each functional unit is an image, or memory map, of

an actual element of the plant, e.g., ventilation or boiler plant.

Control functions

The open-loop control functions required for a given element are locally an

integral part of the functional unit (e.g., the increase, after a time delay, in the

speed of a multi-stage fan, or the demand-based switch-on of a boiler). In each

functional unit, various possible requirements are prioritized and evaluated. The

resulting operating mode is then passed on to the elements or subordinate

functional units. The functional unit already incorporates the I/Os needed for

the physical data points.

Structure control functions

In this way, complex control and monitoring functions of a plant can be logically

subdivided to allow for clear assignment of the function unit or the real element

of the plant. The higher-level control concentrates on the control and

monitoring of the overall plant, while the sub-control function units assume

internal control and monitoring of the given elements for the function unit.