Intelligent distributed system removes the risks, complexity and cost from project management of control systems

Citation

(2004), "Intelligent distributed system removes the risks, complexity and cost from project management of control systems", Assembly Automation, Vol. 24 No. 3. https://doi.org/10.1108/aa.2004.03324caf.004

Intelligent distributed system removes the risks, complexity and cost from project management of control systems

Intelligent distributed system removes the risks, complexity and cost from project management of control systems

Keywords: Control systems

The ever increasing size, sophistication and complexity of sortation and handling systems, as stores strive to increase efficiency and offer greater consumer choice, is a constant problem for the OEMs and system integrators (SI) who build such systems. In particular, the growing trend towards larger capacity systems, which increase throughput rates and provide greater flexibility to deal with product variation and changing supply demand, place increased pressure on SIs and OEM's to get things right on time and within budget, often in the face of loose specifications and fiendishly large and complex software programs. In view of these demands it comes as no surprise that, when designing and integrating a control scheme, control engineers prefer to use past practice to minimise risk.

In the case of materials handling and sortation control systems “Past Practice” for SIs and OEMs translates into a system employing standard programmable logic controllers (PLCs) and motor starters mounted within a central cabinet with point-to-point cabling to motors and field devices. In the mid-1980s, the emphasis was placed on reducing the cabling costs and installation times of these centralized systems, via the introduction of Fieldbus technologies and PLC remote I/O modules. However, despite these advances and the partial migration towards decentralisation, the vast majority of installations are still designed around costly, multi-bay cabinets housing power distribution, motor controllers and rack type PLCs.

By adopting the centralized route, OEMs and SIs are locking themselves into an uncompetitive cost spiral as systems continue to grow in size and complexity.

These costs become evident in the escalating levels of software expertise required, and with the fact that, even for small systems, central software execution programs can exceed 100,000 lines of code. In addition, the increasing requirements for high-speed sortation and complex algorithms for batch handling, data manipulation and product tracking, means that high-level languages are increasingly being employed. This, in turn, means costly, top of the range processors with expensive software licences and, probably, specialist communication devices.

As a result of these issues software has perhaps become the major consideration for SIs and OEM's due to its impact on all stages of the project lifecycle from tendering through to commissioning.

One solution to address the software complexity issue, and, at the same time, equip the OEM and SI with far greater certainty in control system specification and manufacture, is an intelligent distributed control system architecture.

By distributing intelligence, a control system is simplified into smaller independent control nodes, communication network traffic is reduced because decisions are being taken locally and, crucially, project costs are much reduced – anywhere between 20 and 60 per cent, depending on the size and configuration of the system.

As a result, intelligent distributed control architectures provide the ideal solution for such tasks as high and low level conveyor control, materials handling, sortation, palletising, intelligent picking and routing.

There are, of course, many PLC vendors offering distributed control products, but these are generally uncompetitive when one considers the separate processor, power and communication modules needed for every section of a conveyor system. In contrast, modular PLC's with remote distributed I/O cards could be economically viable, but they are a compromise and do not provide the peer-to-peer communications, which are essential for an intelligent distributed architecture, enabling interlocks and sequence signals to be sent between nodes.

An alternative to the compromise of PLCs is IDC's “Intelligent” Simplicon system. UK designed and developed, the Simplicon system enables even the most complicated machine sequences to be broken down into simple, separate control tasks, each task having its own intelligent processor relating to the mechanical subassembly or plant section being controlled. Once this is achieved, each module is networked via RS485 or Ethernet communications to provide a true multi- processor system solution, the peer-to-peer system resulting in a more efficient communication network where traffic is reduced as a result of decisions being taken locally (Plate 5).

Plate 5 Simplicon system enables even the most complicated machine sequences to be broken down into simple, separate control tasks

The key element of the Simplicon system is IDC's multi-processor Windows-based Simplinet software.

With this IEC61131 compatible package IDC have overcome the cost and dependency on high- level software programming skills and in-depth communications knowledge. Simplinet is incredibly easy to use and the fact that it is modular eliminates repetition, whilst the provision of pre-programmed functions provide the control system designer and system user with the benefits of tested designs and proven performance.

Where Simplicon is both different to and superior to existing technology but does not have obvious advantages of reduced cabling costs, or quicker instillation times, but in the hidden benefits that extend throughout the whole lifecycle of a project. By providing a control methodology that is modular in both hardware and software, Simplicon takes out the risks in project management. It achieves this by fixing the costs of control systems early in a project and by facilitating standardisation of designs and documentation, from initial design proposal through to final commissioning. What this means for the SI and OEM is that project tendering and estimating can be much more accurately defined. In addition, bid interpretation, defining an offer and presenting a control solution can be much more easily quantified and qualified. Finally, if a system needs upgrading or extending at any time this can easily be achieved, in contrast to centralised systems, where cabinet space would otherwise prohibit.

For further information, contact: Kevin Buckly, IDC Ltd, Keynes House, Chester Park, Alfreton Road, Derby. DE2I 4AS. Tel: +44 (0) 1332 604 030; Fax: +44 (0)1332 604 031; E-mail: sales@idc.gb.com; Web site: www.idc.bg.com