The global site of the UK's leading magazine for automation, motion engineering and power transmission
15 June, 2024

Twitter link

Ladder logic still dominates PLC programming

13 May, 2016

Ladder logic continues to be the dominant language for programming PLCs, accounting for more than 81% of the global market, despite the availability of several other languages defined in the IEC 61131-3 standard. New research from Technavio suggests that Functional Block Diagram (FBD) programming represents just over 11% of the market, with other languages accounting for the remaining 7.24%.

The Global PLC Software Market 2016-2020 report predicts that PLC programming will merge with motion control and robotics programming, and forecasts that the global market for PLC software will be worth $684m by 2020 – representing a CAGR of more than 7% since 2015, when it was worth $485m.

“Traditionally, industrial robots, motion controllers, and PLCs were programmed separately,” explains Technavio automation research analyst, Bharath Kanniappan. “PLCs are programmed in ladder logic, motion controls with their wide range are programmed using a PC library or other proprietary language, and industrial robots are programmed in complex proprietary languages that are difficult for non-technical personnel to understand.

“Therefore,” he continues, “end-users are demanding robots, motion controllers, and PLC to be programmed in familiar PLC languages, so that it can be easily understood by machine-builder programmers and maintained by end-users’ service personnel.”

Technavio suggests that as applications continue to grow, two types of industrial controls – robotics and motion – are merging in terms of deployment. Robotics is a path-dependent or event-based application. Motion control is typically a scan-based velocity or positioning application. The user interface in robotics is based on teach pendants, while motion control uses programming methods such as ladder logic and FBD.

Technavio estimates that the global market for ladder diagram (LD) programming software was worth $395.1m in 2015. Ladder diagrams mimic relay logic and are based on relay logic wiring schematics, reducing the need to retrain electricians, engineers, and technicians to use it. LD is widely used for sequential control and is useful for simple control systems and for replacing hardwired relay circuits.

As PLCs have become more sophisticated, LD programming has also improved and is now used in complex automation systems. Usually, ladder logic languages from different software suppliers are incompatible and even different PLC variants within the same brand may use different ladder notations and cannot be interchanged.

Global market shares of PLC programming languages in 2015
Source: Technavio

Technavio values the global market for functional block diagram (FBD) programming software at $54.53m in 2015. FBD presents a graphical image with underlying algorithms already defined. The programmer simply completes the required information within a block to complete each phase of the program. Reduced downtime and ease-of-use have accelerated the adoption of function block diagrams and libraries. The adoption of FBD has also been encouraged by the development of IEC standards.

FBDs are stable, and can be used in a wide range of applications. They reduce complexity and allow programmers to work without needing to understand the internal functionalities of the blocks. The FBD language also offers the flexibility to re-use the code.

Other forms of PLC programming software were worth $35.09m in 2015, according to Technavio. They include the instruction list (IL), sequential functional chart (SFC) and structured text (ST) languages. IL consists of lines of code that each focus on one operation. It has a systematic layout and format, which makes the incorporation of a simple mathematical functions easy. Programs written in IL can be moved easily between hardware platforms, and take up less PLC memory space.

Although IL has limited applications, it is popular in Europe, which places a higher premium on the transferability of programs. It is used mainly in the automotive, power generation and transmission, and water and wastewater industries. 

  • To view a digital copy of the latest issue of Drives & Controls, click here.

    To visit the digital library of past issues, click here

    To subscribe to the magazine, click here



"Do you think that robots create or destroy jobs?"



Most Read Articles