Runtime Environment

The success of a concept is not least dependent on its technical realization. The current automation technology poses particular challenges to runtime systems. For example:

• Real-time capability

• Determinism

• Supporting IEC 61131-3-compatible languages

• Supporting heterogeneous hard- und software

• Integration into the existing infrastructure

The ACPLT-runtime environment meets these requirements by utilizing ANSI C and a strict and cyclic execution sequence of the components and also by implementing the function block language as basis capsulation mechanism. For communication purposes, the open protocol ACPLT/KS is applied in binary and in XML form. Additionally, each server is equipped with an HTTP-interface.

The highly portable system cannot only be used on different hardware-platforms (x86, ARM, -Controller) but also on different operating systems (Windows, GNU/Linux). Due to this versatility, the system can also be used on various levels of the automation pyramid.

The proven ACPLT/OV-system provides the basis for the runtime environment. This makes the use of object-oriented paradigms like inheritance, polymorphism and reflection possible. Furthermore, a persistence mechanism is provided for already generated instances so that they continue to exist in case of a system reboot.

schematic diagram of the runtime environment Copyright: PLT

The type-development takes place offline (see figure) and in higher programming languages like C. A typical example of a type is a complex controller that is encapsulated as a function block (dark colored parts of the figure). In general, function blocks are used as smallest units for the program organization (POUs).

The engineering phase usually takes place during runtime and consists of the parameterization of the block instances and merging them together into function block diagrams. The overall stability of the server is not threatened during the engineering procedure. The structure of the created diagrams can always be explored by means of reflection mechanisms.

In addition to these diagrams, several languages for the description of procedures are also available during the engineering phase (Sequential State Charts, similar to sequence languages and UML Statecharts). The interaction of these three paradigms enables both, Black- and White-box encapsulations and the recycling of software-components during the entire lifecycle of the runtime system.

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