Apr. 12, 2019

Industrial Testbeds Structure





Up to now, two real testbeds have been constructed, the first one was installed in a screws production company which is a member of the Green Forge Innovation Cluster. The second one was installed at the WSK “PZL-Rzeszów” in the department which produces major rotating parts for the aviation industry. It should be emphasized that the department size is similar to medium sized Polish companies but on the other hand WSK “PZL-Rzeszów” is one of the biggest companies in Poland which produces parts for the aviation industry. The first testbed consists of two machines sections formed by pushing machines for cold forging. The first section includes machines without PLC controllers but the second one consists of six modern machines equipped with PLCs and advanced cold forge process monitoring devices. The WSK testbed includes one production line with four CNC vertical turning lathes and two CNC machining centers.





The machines in the testbeds have been operated by experienced operators who interact with the system using RFID cards, barcode readers, electronic calipers and industrial panel pc with touch screen. Due to a reasonable cost and broad range of hardware platforms with different computational power capabilities PACs from Beckhoff [WWW-1], i.e. embedded PCs controllers were chosen. There are two kinds of Windows systems available for the controllers, i.e. Windows CE and Windows XP Embedded. Windows CE is equipped with .Net Compact Framework, Windows XP Embedded is equipped with .Net Framework.





There are benefits of using the XP Embedded platform, e.g. homogeneity of the software platform for controllers and PC stations as well as availability of network and virus protection. Due to the financial reasons Ethernet network for communication and controllers with Windows CE were chosen for the two testbeds. Current system structure implemented in the testbeds is shown in Fig. 1. There is one controller with an industrial 15” touch panel in each machine section or production line installed. The controller is connected with six machines via distributed EtherCAT communication devices equipped with digital or analog inputs and outputs.

















Embedded PCs are equipped with Windows CE 6.0 operating system, real-time PLC subsystem TwinCAT [WWW-1], UPS, Ethernet as well as RS-232/485 interfaces for communication and DVI/USB interfaces for touchable monitors connection.





The software part of the system consists of three layers: a shop-floor level software for embedded PC, a data and application server and www client stations. Detailed communication software structure for the shop-floor level is shown in Fig. 2. In the software for an embedded PC four layers can be distinguished:





• the PLC program written in the ST language;

• the middleware module for communication between the PLC program and other system parts, written in C# with utilization of the Automation Device Specification (ADS) protocol [WWW-1];

• the HSI module - operator’s GUI written in C#;

• the communication module written in C# for communication with database using web services technology.









PLC control programs run in the PLC layer on the same device simultaneously with GUI, data processing and database communication modules which run in Windows CE (Fig. 2). The ADS protocol enables C# programs to read and write data directly from and to PLC programs via names of PLC variables. It significantly simplifies the communication between PLC and C# applications. In the data and application server layer the PostgreSQL database has been used together with the GlashFish application server and web services written in Java. In the www client stations layer websites written in JSF, JSP, Ajax and JavaScript are used. Communication between the controllers and the database and between the presentation layer and the database is performed using web services or EJB technology. The presented approach simplifies communication inside the system in a heterogeneous software environment.