شبیه سازی سیستم کنترل یکپارچه برای پشتیبانی از تغییرات استراتژی مسیریابی در سیستم خودکار جریان مواد

Increased demand for customised products, sophisticated scheduling requirements caused by shorter product life cycle and hardly foreseeable disturbances have created a new challenge for the manufacturing industry. Planned production schedules often become ineffective in actual execution on the shop floor. If forecasts become less and less accurate, support for continuous changes is helpful. Given the high degree of automation in manufacturing systems, automatic control systems have become central to shop floors’ responsiveness. However, their state-of-the-art architectures are unable to cope with the challenge successfully. Improvements in information and communication technology makes the integration of simulation and control system more promising. The paper proposes an approach for supporting changes of routing strategy in an automated material flow system by utilising the integration. The approach includes (re-)planning of the automated material flow system, commissioning its logic control and controlling the material flow.

Impacts of globalisation have created a new challenge for manufacturing industry. The possibility for greater integration within the world economy through movements of goods and services, capital, technology and labour is leading to hardly predictable market situation. Customers are coming from all over the globe and demand for more customised products. Besides, global competitors keep competing for introducing new products which effects on shortening the product life cycle. The implications of this situation are the diversity of environments within which the production planning and control system must operate have increased and will continue to do so [1]. In other word the scheduling become more sophisticated and even worst the planned production schedules often become ineffective in actual execution on the shop floor due to barely foreseen disturbance. As forecasting and planning become less and less reliable, the support for continuous changes is helpful. Short response times and high changeability in layout and in processes for the production and logistics structures are strongly required [2]. Changeability is used as a generic term for various abilities to carry out change within the manufacturing industry [3]. Changeability is defined as a characteristic of a production system that enables an economical, timely and proactive adaptation of all factory components, levels, and processes [4]. Nyhuis et al. differentiates changeability from flexibility by its ability and potential to realize fast adaptation within narrow range of change, both at the organization and thestrategic levels, with low investment (Fig.1) [5]. In current practices, ad-hoc solutions have been developed in response to changes, which the implementation often took several months or years.Frequently, the expenses used to implement the solution did not produce the expected payback, since the next change wave often starts while earlier adjustments are still taking place [6]. It will not only deprive of time and cost, unexpected results also might appear during the implementation.

In respond to routing changeability challenge for a PLC-controlled material flow system, the paper presented an approach for supporting reconfiguration of its control system due to changes in routing strategy while maintaining predictable and stable system behaviour. To give the explicit picture of the approach, the architecture and an application study are described. The outcomes of the study have seen to be positive. The changes from one routing strategy to another can be performed in significant short time due to no conversion is needed from the PLC language to simulation language. Using the same model for planning and controlling the automated material flow system has ensured direct implementation of the planned routing strategy. The difference of completion times between simulation and real system has been expected due to some simplification in the model e.g. neglecting of times taken by stopper for reaction. This issue however can be improved.From the presented approach, possibilities for expansion and improvement can be seen either at the organisation aspect or technical aspect. Further initiative has been taken in integrating the approach with others aspect of planning e.g. scheduling of production orders. Some further work also has been planned in including resources such as industrial robot in the approach. The idea is to use material flow simulation software not only for controlling the material flow system but it wills also managing the utilisation of their connected resources.