It is not just Industry 4.0 or Ethernet-based fieldbus protocols that are bringing real-time solutions into focus. There has been a demand for real-time capable control and automation systems in many sectors for decades. It applies in particular to decentralized systems for a predominantly heterogeneous automation infrastructure, which can often only be met with customer-specific developments based on real-time operating systems.

As early as the 1980s, sectors such as the automotive and aviation industries, mechanical engineering, energy suppliers, biotechnology companies and the pharmaceutical industry were already demanding alternatives to non-deterministic, linear PLC programming. Even then, real-time computers with an open computer architecture and bus systems such as VMEbus and PMC/PCI were able to create these alternatives. Today, compact real-time automation systems are able to perform fast control and regulation tasks in a decentralized manner. They are characterized by powerful processors, an open communication level using standardized protocols and the use of real-time operating systems such as QNX, VxWorks or OS-9.

Real-time system versus PLC

The fieldbus and programmable logic controllers (PLCs) considerably simplified industrial and plant automation in the 1980s. Today, PLCs as a mass product are an inexpensive standard solution with high availability and simple programming. They are 'all-rounders', but with limitations: the many processing levels, for example via modules and system bus, lead to asynchrony. In addition, a rigid sequence of cyclical processing, slow reaction to sudden events and the difficulty of recording short-term processes are also considered disadvantages.

On the other hand, there are real-time automation systems with an open computer architecture based on PowerPC, ARM and Intel processors. They have open communication levels with interfaces to Ethernet and common fieldbuses as well as a modular operating system. By programming close to the processor using high-level languages, real-time applications can be implemented, as required for axis control and motion control applications and others. Alternatively, they can also be programmed as soft PLCs under Codesys in accordance with IEC 61131-3.

Even though powerful CPUs are also used in PLCs today, they are often not fast enough in synchronization processes due to the need to operate many applications. There is also no chance of programming close to the CPU core and thus guaranteeing deterministic behavior. Their linear program sequence is limited to the pure control function, without linking controls or processing, visualizing or archiving data.

Real-time automation systems are always based on powerful, state-of-the-art CPUs. Operating systems that have been tried and tested over decades ensure real-time operation. This gives them the flexibility to respond to time-critical variables. The open communication level offers interfaces to Ethernet-based protocols and/or fieldbus protocols such as Profinet, Ethercat, Ethernet IP as well as CAN, CANopen, Profibus, DeviceNet, etc.
Modular PLC systems with a standard PC architecture under Linux offer almost deterministic behavior, but this is often not sufficient for very fast control processes. Fast real-time control is particularly important if full automation is to be achieved reliably for economic reasons, for example in plant automation with conveyor belts and feeders.

Industrial PC for fast tasks

The Hanover-based company esd Electronics specializes in individual control and automation systems. Based on proven components and standardized interfaces, esd has developed an industrial PC as a standard product. The result is a versatile single-board computer that minimizes risk and costs for the user.

Real-time automation systems have an open communication level with standardized protocols and support real-time operating systems such as RTOS UH, VxWorks or QNX.

© esd Electronics

The EPPC-T10 single-board computer from esd Electronics is a compact and powerful industrial PC that masters fast control and regulation tasks, even with real-time requirements. It is equipped with a PowerPC QorlQ CPU and has three independent 1 GBit Ethernet interfaces. In order to be able to process Ethercat data quickly via these Ethernet interfaces, the Ethercat master stack from esd is required. This software manages the cyclical exchange of process data and is used to configure the Ethercat networks. In this combination, the EPPC-T10 can also be used in Ethercat applications. The Ethercat master stack is available for Linux as well as for several real-time operating systems such as QNX, VxWorks or OS-9. The software can also be used on computers from other manufacturers with the supported operating system.

Up to three machines

The EPPC-T10 can be used to implement an autonomous control system for up to three machines or three drives. When integrated into the control level above, for example, two drives or a redundant drive can be controlled. Within the control level, the single-board computer can also be used as a gateway between Industrial Ethernet, Ethernet OPC UA and/or the cloud with the appropriate software. Despite the defined scope of performance, the option of customized modifications remains available.

The EPPC-T10 single-board computer can be used in Ethercat applications with up to three independent networks.

© esd Electronics

The single-board computer is based on an embedded 64-bit PowerPC QorIQ-T1014 from NXP with 1.2 GHz. It has a 64-bit core based on power architecture technology. The processor is also available with four cores for higher requirements. The integrated DPAA (Data Path Acceleration Architecture) enables high-performance, direct data exchange between the various integrated interfaces of the CPU, which reduces the load on the cores. The local memory bus is 64 bits wide with an additional 8-bit ECC and a total capacity of 512 MByte. The computer contains the standard program 'U-Boot', which enables different operating systems to be booted from different media depending on the data volume: from the on-board flash, via the network, via USB, from a microSD card or optionally from the SATA SSD. The single-board computer also has a double-precision floating point unit and is equipped with a real-time clock (RTC) with battery backup. The computer measures 117 mm × 31 mm × 160 mm (L × W × H) and is suitable for mounting on the DIN EN mounting rail (TS 35). The standard version of the EPPC-T10 runs under Linux, other (real-time) operating systems such as QNX, VxWorks or OS-9 are available on request.

Safe operation in industrial environments

The 1 GBit Ethernet interfaces can be connected in the front panel via RJ45 sockets. The computer also offers an RS232 and a USB 2.0 interface (host), a microSD card slot and an internal PCI Express mini slot for hardware expansions. Safe operation in industrial environments is primarily achieved by monitoring the local voltages and temperatures as well as a fail-safe firmware update via fallback flash. Secondly, the guaranteed operating temperature range of 0 °C to +55 °C, a watchdog function and multi-stage overtemperature protection increase operational safety.

If these performance features are not sufficient, customer-specific requirements can also be taken into account for larger quantities, such as the alternative use of the PowerPC QorIQ T1022 power-saving dual-core processor, a parallel or serial MRAM with 512 KByte, an extended DDR3 RAM with 2 GByte, a larger flash memory up to 2 × 128 MByte. A PCI Express slot can also be integrated, for example to expand I/Os with the help of PMC modules via a PMC add-on module, including the necessary housing adaptation.

Authors:
Renate Klebe-Klingemann is a technical editor at esd Electronics;
Dirk Flege is Sales Manager at esd Electronics.

From the field

When new technologies or systems need to be introduced, companies often turn to external service providers such as esd Electronics:

• Fast booting
  In the search for a single-board computer for an existing 3U VPX system with CAN bus interfaces and other performance features, a company from the military sector became aware of a PCI/CAN board from esd Electronics. In addition to the CAN interfaces, the following interfaces were required for the application: a serial interface, an Ethernet and a USB host interface as well as digital inputs and outputs according to the company's own specification. The CPU board also had to be able to operate without a fan at ambient temperatures of -20 to +85 °C. esd offered to develop a customer-specific board using its own CAN core (esdACC).
  
  A critical point of the application was the requirement that the PC system with Intel Atom processor had to boot in less than ten seconds. To prove that the selected combination of processor and operating system met the time requirements, esd carried out a preliminary study using an evaluation board. After a successful series of tests, the order was placed for the development of the CPU module. The quality of the prototypes was so high that they could be used as a pilot series. This was possible because the tried-and-tested CPU module with Intel Atom processor and the CAN core, which had been tried and tested in other products, could be used. In order to safely dissipate the heat at an ambient temperature of 85 °C, a specially adapted heat sink was developed for the board, which is thermally connected to the conduction-cooled chassis. This resulted in a customer-specific CPU system that the customer can use for their own configurations.

• Up to 3000 meters water depth
  A manufacturer of deep-water systems was looking for a compact computer as part of the control and monitoring system in a hammer drill. He opted for a customized control computer from esd with PowerPC architecture, a CompactPCI system and CANopen communication. In addition, several serial RS485 interfaces were replaced by redundant DSL lines (bandwidth up to 5 MBit/s). The computer has eight serial interfaces as well as CAN-CBX I/Os for 32 analog inputs, which integrate devices such as a compass, depth pressure sensor and acceleration sensor (gyro). There are also 16 Pt100 inputs for recording various temperatures and conductivity, which can be used to draw conclusions about water ingress, water pressure, oil temperature or the proportion of water in the oil. The control unit also offers 64 digital inputs and outputs as well as two Ethernet interfaces. The computer is part of the control and monitoring system and has been integrated into a pressure-resistant system box, which is installed directly on the hammer drill and therefore in water depths of up to 3000 m. Only a single cable with lines for the supply voltage and DSL communication is required for operation at depth.