1. The Development of Programmable Automation Controllers (PACs) is an Inevitable Trend. Over a decade ago, when the Internet was in its infancy and PC-based instruments were not yet available, PLCs dominated the automation field. Even today, engineers using digital I/O for simple control still feel that PLCs are the best choice. However, if we consider adding vision, motion, instrumentation, and analysis capabilities to PLCs for comprehensive automation, only the next generation of Programmable Automation Controllers (PACs) can gradually take over. This is a necessity for the development of control systems today. It is well known that when designing and building control systems, engineers always hope to achieve more functionality with fewer devices. Especially today, they need control systems that can not only handle digital I/O and motion but also integrate vision functions and modular instruments for automated monitoring and testing. They must also be able to process control algorithms and analysis tasks in real time and transmit data back to the enterprise. In other words, engineers want both the functionality of a PC and the reliability of a PLC (Programmable Controller). A Programmable Automation Controller (PAC) is such a platform, optimally combining the advantages of both PCs and PLCs (see Figure 1). It offers open industry standards, scalable domain functions, a universal development platform, and advanced performance. It is a relatively complete emerging controller in the field of industrial automation. So, "What is a PAC?" What are its characteristics and advantages? This article will analyze the advantages of PAC by comparing its various features with those of a PLC. First, let's define what a PAC is. The term PAC defines a new type of controller. This controller combines the advantages of a PC's processor, RAM, and software with the inherent reliability, robustness, and distributed nature of a PLC. PACs utilize existing commercially available technologies (COTS), making them well-suited for industrial environments. They are scalable, easy to maintain, and have a low failure time. 2. PAC Platforms The rapidly growing PAC platform is based on PXI. Because PXI combines the circuitry of the PCI bus with the robust Eurocar mechanical structure of Compact PCI, this architecture has been successfully used in industrial environments for many years. Today, vendors such as NI, Chroma, LeCroy, and JTAG offer over 1,000 unique I/O modules, including analog I/O, digital I/O, vision, motion, and high-precision data acquisition. Typical PAC hardware platforms include the following four: * PXI improves upon industrial PCs, featuring a real-time OS, standard cooling, optional non-spinning solid-state drives, and built-in inter-module synchronization. The PXI standard requires all chassis to provide 25W of airflow cooling for each module slot, preventing overheating or shortened lifespan even when using high-power relays, high-speed PXI, or CompactPCI cards. * Compact FieldPoint uses industrial-grade components to withstand strong shocks and vibrations, operates in a temperature range of -40ºC to 70ºC, and is Class 1 Division 11 and Lloyd's certified. It also uses conductive cooling instead of a rotating fan, improving reliability due to the absence of moving parts. * The Compact Vision system is a rugged controller specifically designed for machine vision. It uses the IEEE standard 1394 FireWire interface and can communicate with up to 16 cameras in vision applications. * CompactRIO is a new type of reconfigurable embedded system based on LabVIEW FPGA and LabVIEW real-time technology. The CompactRIO system uses an FPGA chip with 3 million gates to control modular digital and analog I/O. These FPGA chips can run code embedded in the chip, with a digital loop rate of up to 1MHz and an analog loop rate of 150kHz. The FPGA can transmit information back to a floating-point processor running LabVIEWRT for advanced computation, data logging, and communication. Due to its metal housing and conductive cooling, this controller is well-suited for harsh environments. 3. Analysis of the reasons why PACs are superior to PLCs. The reasons why PACs are superior to PLCs will be analyzed from six aspects: cost, advanced functions, form factor, controller, I/O, and software. 3.1 Cost - The Most Economical Choice: A single controller saves costs. It features a single controller and chassis for handling digital and analog I/O, motion and vision functions, and modular instrumentation, eliminating the need to purchase multiple controllers. Therefore, if a control system requires multiple functions, such as vision or modular instrumentation, then a PAC is the most economical choice. 3.2 Advanced Functions with Multifunctional Real-Time Control: * Advanced Control Optimized for Process Control: Due to the high cost of energy or materials, engineers often optimize PID control algorithms for process control to minimize waste. These algorithms often employ control design techniques such as fuzzy logic or neural networks, thereby minimizing process control settling time. Traditional PLC-based PID control algorithms are not optimized for specific process controls. Advanced control algorithms require powerful floating-point processors and significant memory usage, but a PAC platform can meet the requirements for optimized process control. * Real-Time Monitoring and Analysis: Systems that monitor machine operation require real-time data acquisition from analog or digital I/O channels to effectively detect fault conditions. This might require complex tasks such as real-time order tracking and vibration analysis to effectively monitor machine conditions. However, for these applications, PAC's efficient platform can be used for real-time analysis. *Control System Connections to Databases and Networks: Utilizing real-time data from within the plant, operators can make decisions from the control room based on the information obtained. However, enabling a control system to output field data is challenging. Enterprise systems typically use standard ODBC, ADO, and XML to obtain data from automation systems. PLCs can only communicate via standard OPC, meaning an additional PC is needed to acquire data using OPC and transmit it to the enterprise using standards such as ODBC (Open Database Connectivity), ADO (Design for Data Automation), and XML (Extensible Description Language). To effectively transmit field data to the ERP system, the control system must be able to communicate directly with external databases; PAC can perfectly accomplish this. *Data Encryption During Network Transmission: Security is a crucial consideration when connecting the control system to databases and networks. For security reasons, many manufacturers choose not to connect their automation systems to their enterprise databases. However, for most manufacturers, the benefits of connectivity far outweigh the security concerns. While PLCs can be locked to prevent unauthorized access to the factory network, they are not suitable for preventing hacking because they send unencrypted packets over Ethernet. PACs, on the other hand, can encrypt data when transmitting it over the network. Although this is not currently the primary consideration, it will be a major reason for the adoption of PACs in distributed systems within the factory in the future. *Deterministic Applications with Multiple Speeds and Cycles PLCs can only operate at a fixed speed and are not designed to process data independently at different cycle rates. However, today's complex control systems often require deterministic applications at multiple speeds, requiring multiple cycles, each running at a different rate. This necessitates parallel processing capabilities, a feature only operating systems running on PACs possess. 3.3 Flexible and Robust Architecture *Suitable for Factory Environments A common reason for choosing a PLC is its ability to operate normally in a factory environment. However, most PLCs are installed in nematic boxes. However, in such an environment, the PXI platform's added cooling system, robust exterior, and enhanced shock and vibration resistance give the system the same reliability as a PLC. * **Strong Scalability:** Engineers desire flexible automation systems to meet ever-evolving requirements, necessitating modularity, flexibility, and scalability in their control systems. While PLC systems, limited by I/O constraints, offer scalability only in digital and motion aspects, PACs not only possess the scalability of PLCs but also allow for the addition of vision systems, modular instruments, or high-speed analog I/O. Multiple PCs can be used via Ethernet, with the number of PCs added or removed as needed. * **Easy Module Upgrades or Replacements:** Minimizing downtime is crucial for field engineers. Updating or replacing I/O modules in the control system requires minimal effort. PACs' modularity meets this requirement. 3.4 Controller * Featuring a Pentium 4 Processor and Gigabytes of RAM Because existing hardware is used to build the PAC-based system, the PAC controller can utilize a Pentium 4 processor and has gigabytes of RAM, meeting the requirements of high-speed processors and large memory capacity needed for high-speed monitoring of machine status. * Information Storage Function The PAC can record data according to specified time, method, and data format. What's the use of information if it can't be saved and viewed? PLCs traditionally lack data logging capabilities. * Digital I/O Provides 24V Voltage, Up to 500mA Drive Current, and Optical Isolation Traditionally, PLC platforms' digital I/O can only provide standard voltage drive current for industrial sensors and actuators. However, newer modules such as the N1 651x series offer 24V voltage, up to 500mA drive current, and optical isolation. They also feature a watchdog timer, programmable power-on status, and input filters for enhanced safety and reliability, all at a cost of only $5 per channel. * Analog Input Rate Up to 200 Mbps: While some PLCs have analog I/O modules, their programming is complex and unsuitable for high-resolution and large-data-volume applications. PACs, on the other hand, offer analog input rates up to 200 Mbps with 24-bit resolution, primarily due to the high speed of the PCI bus technology, allowing for PC-based analog I/O. * Up to 8 Axes of Motion: Software plays a crucial role across various platforms, especially when more than two axes of motion are required. Motion controllers on PXI platforms can provide up to 8 axes of motion, and the system can be easily configured using NI Motion Assistant. * Data Transfer Rate for Vision Applications: Data transfer rate is the biggest obstacle to providing vision functionality on PLC platforms. Currently, whether for automatically monitoring parts or inspecting pharmaceutical packaging, analog, digital, and FireWire cameras for vision applications can be used on PXI platforms. Various vision algorithms, such as pattern matching, optical character recognition, color matching, and specification and color detection, can be integrated into the control program. * Interconnectivity via various industrial fieldbuses: Similar to PLCs, PACs can interconnect via various industrial fieldbuses, such as FOUNDATION Fiedbus, DeviceNet, CAN, Modbus, Ethernet, PROFIBUS, and serial ports. PACs can function not only as master devices for distributed I/O modules but also as slave devices added to existing systems. 3.5 Software * Real-time Operating Systems: Real-time operating systems (RTOS) such as RTLinux, PharlapETS, QNX, and VxWorks can be used on the PAC platform. Generally, programming real-time systems is difficult, but software like LabVIEW RT can change the way engineers develop real-time systems. Engineers can now download programs developed on Windows to real-time platforms, such as PXL controllers. * Graphical Display of HMI (Human Machine Interface): Especially in hybrid and process control industries, most control systems require a human-machine interface to connect to the control system. An HMI consists of a touchscreen and may or may not include an embedded controller. Because PAC-based systems utilize the same controller for I/O, there's no need to add an additional embedded controller for HMI image display. *Easy Development Environment: While traditional ladder logic programming is well-suited for digital I/O programming, it's cumbersome for analog I/O, motion, or vision programming. PACs offer great flexibility by allowing control programs to be written in common languages, including C, C++, Visual Basic, LabVIEW, and even traditional ladder logic. 4. The above illustrates the functional differences between PACs and PLCs. PACs can perform more advanced tasks: * Real-time vibration analysis, image processing, motion control, and CAN; * Executing automatically adjusting PID control or adjustable gain PID control, and fuzzy logic; * Communication using built-in web servers, FTP servers, and e-mail functionality. 5. Conclusion PAC is a new generation of PLC, and its advantages can be summarized in five main characteristics: * Multiple functions: at least two logic, motion, PID control, drive, and processing functions on a single platform; * A single multi-process function development platform, using common tags and a single database to access all parameters and functions; * Software tools allow designing processes across multiple machines or processing units, and can be integrated with IEC 61131-3, user manuals, and data management; * An open modular structure, reflecting industrial applications from factory machine layout to unit operations in machining workshops; * Employing practical standard network interfaces, languages, etc., such as TOP/IP, OPC, XML, and SQL queries. Because PAC can add the necessary PC functionality for advanced control, real-time analysis, or connection to enterprise databases while maintaining the reliability of a PLC, it may be an excellent choice if you need more than just integrated digital I/O and motion control, or faster computer processing power. Therefore, for today's engineers, in addition to PLC control, PAC is an optimal choice, and it is taking over the field of automation. The PAC concept will play an important role in factory automation today and in the future. References: 1. ACs Video Technology Guide, 2005. 2. Niu Wenyong et al. Monitoring System for Medium and Heavy Plate Rolling Machines Based on Industrial PCs and PLCs, Metallurgical Automation, 2001.