A comparison of process control systems for the automation of production plants

Which automation system is the right one? ControlTech Engineering AG (CTE) from Liestal compares and supports systematic decision-making. Whether in industrial production, in energy and water supply or in the pharmaceutical industry - automation systems must be precisely tailored to the respective application.

How do we at CTE go about finding out which process control system is the right one? We compare according to predefined criteria. This always involves structure and design, sufficient flexibility for every requirement, good interfaces or support for industry standards such as ISA88/MTP, ProfiNet, OPC-UA, MQTT, etc.

We pay attention to the manufacturer's support as well as to license models and scalability during installation. We keep an eye on the capex costs of the basic installation as well as the anticipated scaling and corresponding opex costs. In this way, we avoid unpleasant surprises and unforeseen high follow-up costs.

Equally important is the clear presentation of the system components (libraries, software and hardware requirements). We also pay particular attention to customer requirements with regard to modularization. A central goal is to design software in such a granular way that several programmers can engineer in parallel and independently of each other and copy effects can be efficiently exploited by means of instantiation - both initially and in the case of large-scale software adaptations. This is not handled in the same way in all systems.

No major costs for small installations

Once we have evaluated the above criteria together with our customers, we look for possible solutions. In doing so, we focus on common process control systems that we use with the necessary expertise. We would like to take a closer look at the following three systems in this technical article: Emerson's DeltaV, PCS 7 from Siemens and zenon from Copa-Data.

DeltaV

DeltaV is a fully-fledged DCS (Distributed Control System) with a focus on consistency, online changeability and batch/S88 support. Very well suited for large scaling and deterministic online changes.

PCS 7

PCS 7 is a well-established DCS from the Siemens world, with a modular structure, flexible configuration and high PLC speeds at the control level, with central engineering (Simatic Manager) and fully tested components.

zenon

Zenon comes from the very sophisticated SCADA world, but already with virtual soft-PLC. Deliberately flexible, collaborative and hardware-independent, it is less of a classic, more open DCS. Ideal in heterogeneous field levels and for modular automation.

Three process control systems in comparison

In a brief comparison, we show what is possible with the three guidance systems. The clear comparison table has been reduced to the most important points. Of course, the selection is much more complex and the details are divided into many more criteria. However, the overview provides an initial overview:

Criterion	DeltaV (Emerson)	PCS 7 (Siemens)	zenon (COPA-DATA)
Mass/bulk engineering	Library-based CM/EM/modules; template duplication; DeltaV XML/import; OPC UA address space for generic mapping.	COMOS ↔ PAA ↔ PCS 7 (bidirectional); list/bulk engineering; automatic project derivation.	Smart Objects (SO) as reusable modules; multi-user engineering; variable mapping with wildcards.
Modularity (ISA-88/MTP)	MTP approach available via Emerson MTP solutions for module integration.	MTP engineering & runtime integration (VDI/VDE/NAMUR 2658) in PCS 7/Open OS; connect services/parameters.	zenon MTP Suite for end-to-end modular production.
Standards & connectivity	OPC UA server/client (App Station, Pro+; PK controller); DA/A&E/HDA profiles.	PCS 7 driver + OPC UA; MTP services can be linked from SFC/CFC/Batch.	>300 drivers; OPC UA, MQTT/IIoT; M2M communication.
Simulation / Virtual Commissioning	Software already executable on engineering stations and virtual controllers	SIMIT coupling (HW export, VC) for FAT/PoC; data flow PAA↔PCS 7↔SIMIT.	At DCS level simulation in softPLC, at field level manufacturer-independent, e.g. with SIMIT, LabView etc.
Batch/Recipes	DeltaV Batch (ISA-88) - modular per unit/phase; can be coupled via OPC UA/MTP.	SIMATIC Batch; MTP services can be connected from Batch.	zenon Batch & Recipe Management; Smart-Object-based. MTP and classic in the same batch system
Data/project flow	Versioned libraries & templates; export/import workflows.	Central data model in COMOS/PAA; derivation/sync to PCS 7	Project-wide reusable smart objects; team engineering.
MES/IIoT integration	OPC UA; full Syncade integration; MTP-based module integration.	OPC UA/MTP signal coupling in the direction of MOM/MES.	Native drivers, OPC UA & MQTT/IIoT connectors. PasX MSI Interface.

With the evaluation of the comparison table, we demonstrate our experience in the automation of manufacturing companies. The table is intended as a functional overview and supports the selection depending on the project requirements.

DeltaV: Aligned to ISA-88/batch with standardized libraries and a scalable unit/phase model. Strong integration for operation and recipe management. Suitable if a consistently standardized batch procedure is the priority.
PCS 7: DCS with integrated engineering chain (e.g. COMOS/PAA for mass engineering, SIMIT for virtual commissioning) and SIMATIC Batch. Suitable for plants with a high degree of standardization and close coupling between planning, engineering and operation.
zenon: Modular SCADA/soft PLC approach with smart objects, broad connectivity (including OPC UA, MQTT) and advanced MTP orchestration. Suitable for modular, quickly adaptable solutions.

All three platforms support common standards and protocols and can be integrated into higher-level systems. Which solution fits best depends on the objectives of the respective project - such as batch focus, engineering consistency or modular scalability.

Our conclusion: There is no such thing as the best system - just the right one for your application.

What is a DCS (Distributed Control System)?

A DCS is like the brain and nervous system of an industrial plant: it controls, monitors and automates processes - e.g. in:

Chemical plants
Power plants
Pharmaceutical production lines
Water/waste water systems
Food industry

It is not "centralized", but decentralized, distributed as independently as possible (controller, I/O modules, operating stations, historian, etc.) - hence the name. Several process stations work in parallel, but in a coordinated manner. The engineering platform is highly integrated. Not every controller is programmed individually, but via a central software environment. In contrast to SCADA, a DCS typically combines the control and management levels.