Happy’s Essential Skills: Computer-Aided-Manufacturing, Part 1—Automation Protocols
I have addressed automation planning previously in this series, so I hope by now you realize the difference between ‘automation’ and ‘mechanization.’ In printed circuit fabrication and assembly, most of what is advertised is mechanization. But when you get to assembly test, then you begin to see true automated solutions. The difference between the two is the networking and protocols that supply the information and data. An industry for us to look to as an example: our brothers in semiconductor fabrication. This industry has had fully automated factories since the mid-1980s.
This column is dedicated to the automation protocols that currently exist and some new ones just coming on the market. In Part 2, I will present some examples from my own projects.
The ‘messages and recipe data’ needed for production scheduling-to-machine connections has evolved over the years. The selections to be covered here are:
- Serial RS-232C/RS-485
- Parallel IEEE-488/HP-IB
- MAPS™ protocol
- SECS I & SECII/GEM protocols
- LAN (IEEE-802.3 and TCP/IP)
- Wireless and IoT
Recipe-to-Machine and Machine-to-Machine
When I started working with automation control in 1970, we had ASCII characters in parallel cabling. So we started by using these printer and teletype protocols to control machines. Sometimes, we had only BCD to work with! Today you have the ‘lights-out-factory’ and Industry 4.0 initiatives. A lot of progress is the result of the automotive industry’s application of PLCs and robots to manufacturing. Figure 1 shows what the Germans foresee for Industry 4.0. Figure 2 shows the 4-level hierarchy of CAM, while Figure 3 shows typical networked factory control units.
Figure 1: The scope of Industry 4.0 enables an intelligent plant (planet). (Source: Advantech)
Figure 2: Enterprise and plant control topology showing the 4-level hierarchy. (Source: Renesas Edge—Big Data in Manufacturing)
I was fortunate to be employed by Hewlett-Packard. Their 2116-model computers (and later, the 2110) were real-time-interrupt driven computers and ideal for machine control. HP had even developed a CNC machine control system but decided not to sell it since it did not fit their instrument or computer sales force’s experience. They sold all the CNC systems to Allen Bradley in Milwaukee, Wisconsin. Thus, I ended up working frequently with AB to buy back the software that HP had developed. This was serendipitous as AB introduced me to their programmable logic controller (PLC) technology. PLCs became a major tool in machine control.
Figure 3: Typical industrial automation controllers and PLCs. (Source: Wenatchee Valley College, Nevada)
For software, HP had already developed CAD tools for PCB design and mechanical engineering. It had data acquisition, supervisory control and data acquisition (SCADA) and test systems. The Business Computer division had developed MRP and ERP software. In 1982, HP acquired Genesis Corp. (IC-10 and six others like PC-10, software products for factory control). HP had a complete software solution for factory automation connectivity that they had developed for GM and the MAPSTM implementation. As this new software group was made into a division, they expanded their product line to include quality/test/inspection systems, CNC/machine control system, materials handling software and an industrial process control system (licensed from Mount Isa Mines, a mining company in Australia). The HP products were intended for typical factory automation networks are shown in Figure 4.
Figure 4: Industrial automation networking alternatives. (Source: Pinterest network for AB Inc.)
The interconnectivity for machine-to-machine is usually one or all of these connection standards (Figure 5):
Serial RS-232C—stands for Recommend Standard number 232 and C is the latest revision of the standard. The serial ports on most computers use a subset of the RS-232C standard. The full RS-232C standard specifies a 25-pin "D" connector of which 22 pins are used. Most of these pins are not needed for normal PC communications, and indeed, most new PCs are equipped with male D type connectors having only nine pins.
The RS-232C standard limits a cable length to 50 feet. You can usually ignore this standard, since a cable can be as long as 350 meters (1,000 feet) at baud rates up to 19,200 if you use a high quality, well shielded cable. The external environment has a large effect on lengths for unshielded cables. In electrically noisy environments, even very short cables can pick up stray signals. You can greatly extend the cable length by using additional devices like optical isolators and signal boosters. Optical isolators use LEDs and Photo Diodes to isolate each line in a serial cable including the signal ground. Any electrical noise affects all lines in the optically isolated cable equally, including the signal ground line. This causes the voltages on the signal lines relative to the signal ground line to reflect the true voltage of the signal and thus canceling out the effect of any noise signals.
Figure 5: Five typical connectivity standards for industrial automation.
Synchronous and Asynchronous Communication
Important explanations and details are provided by excerpts from TALtech’s “Introduction to Serial Communications” tutorial:
There are two basic types of serial communications, synchronous and asynchronous. With synchronous communications, the two devices initially synchronize themselves to each other, and then continually send characters to stay in sync. Even when data is not really being sent, a constant flow of bits allows each device to know where the other is at any given time. That is, each character that is sent is either actual data or an idle character. Synchronous communications allow faster data transfer rates than asynchronous methods, because additional bits to mark the beginning and end of each data byte are not required. The serial ports on IBM-style PCs are asynchronous devices and therefore only support asynchronous serial communications.
Asynchronous means "no synchronization," and thus does not require sending and receiving idle characters. However, the beginning and end of each byte of data must be identified by start and stop bits. The start bit indicates when the data byte is about to begin and the stop bit signals when it ends. The requirement to send these additional two bits cause asynchronous communications to be slightly slower than synchronous however it has the advantage that the processor does not have to deal with the additional idle characters.
An asynchronous line that is idle is identified with a value of 1 (also called a mark state). By using this value to indicate that no data is currently being sent, the devices are able to distinguish between an idle state and a disconnected line. When a character is about to be transmitted, a start bit is sent. A start bit has a value of 0 (also called a space state). Thus, when the line switches from a value of 1 to a value of 0, the receiver is alerted that a data character is about to come down the line.
RS-422 and RS-485 are high speed serial protocols that can achieve 10 Mbps up to 20 meters or to 1500 meters but at 100 Kbps.
Parallel IEEE-488—is a short-range digital communications 8-bit parallel multi-master interface bus specification. IEEE-488 was created from HP’s HP-IB (Hewlett-Packard Interface Bus) and is commonly called GPIB (General Purpose Interface Bus). Although originally created in the late 1960s to connect together Hewlett-Packard’s automated test equipment, it also had some success during the 1970s and ‘80s as a peripheral bus for early minicomputers, notably the Commodore PET. Newer standards have largely replaced IEEE-488 for computer use, but it still sees some use in the test equipment field.
In 1987, IEEE introduced Standard Codes, Formats, Protocols, and Common Commands, IEEE-488.2. It was revised in 1992. IEEE-488.2 provided for basic protocols and format exchange, as well as device-independent commands, data structures, and error protocols. IEEE-488.2 was built on IEEE-488.1 but without replacing it. Equipment can conform to the simpler IEEE-488.1 without following IEEE-488.2.
As explained in the Wikipedia definition of IEEE-488: “While IEEE-488.1 defined the hardware and IEEE-488.2 defined the protocol, there was still no standard for instrument-specific commands. Commands to control the same class of instrument (e.g., multimeters), would vary between manufacturers and even models…The United States Air Force, and later Hewlett-Packard, recognized this problem. In 1989, HP developed their TML language which was the forerunner to Standard Commands for Programmable Instrumentation (SCPI). SCPI was introduced as an industry standard in 1990. SCPI added standard generic commands, and a series of instrument classes with corresponding class-specific commands. SCPI mandated the IEEE-488.2 syntax, but allowed other (non-IEEE-488.1) physical transports.”
As explained in the IEEE Standards website: “In 2004, the IEEE and IEC combined their respective standards into a "Dual Logo" IEEE/IEC standard IEC-60488-1, Standard for Higher Performance Protocol for the Standard Digital Interface for Programmable Instrumentation - Part 1: General, replaces IEEE-488.1/IEC-60625-1, and IEC-60488-2,Part 2: Codes, Formats, Protocols and Common Commands, replaces IEEE-488.2/IEC-60625-2.”
MAPS™ protocol—Message Automation & Protocol Simulation (MAPS™)
As explained in GL Communications Inc. overview tutorial:
MAPS specifies a set of standard communication services for factory automation, and has been accepted as an international standard by the ISO. It is a protocol simulation and conformance test tool that supports a variety of protocols for such factory floor controllers as PLC, robots, group controllers and cluster controllers. MAPS is one of the oldest and most used of the factory floor automation protocols, being pioneered by General Motors and adopted by General Electric for its factories. MAPS is based on the Reference Model for Open Systems Interconnection (OSI) of the International Organization for Standardization (ISO). It has three main components: the File Transfer, Access, and Management services, the Manufacturing Message Specification services, and the X.500 services. The protocol such as SIP, MEGACO, MGCP, SS7, ISDN, GSM, MAP, CAS, LTE, UMTS, SS7 SIGTRAN, ISDN SIGTRAN, SIP I, GSM AoIP, Diameter and others. This message automation tool covers solutions for both protocol simulation and protocol analysis. The application includes various test plans and test cases to support the testing of real-time entities. Along with automation capability, the application gives users the unlimited ability to edit messages and control scenarios (message sequences). "Message sequences" are generated through scripts.
MAPS™ is designed to work on TDM interfaces as well as on the IP/Ethernet interfaces. MAPS™ also supports 3G & 4G mobile protocol standards for testing the rapidly evolving mobile technologies. MAPS™ can simulate radio signaling protocols such as LTE (S1, eGTP, X2) interfaces and UMTS (IuCS, IuPS, IuH), GPRG Gb, and GSM A over IP transport layer.
MAPS™ test suite is enhanced to simulate multiple UEs and IMS core elements such as P-CSCF, I-CSCF, S-CSCF, PCRF, MGCF in IMS core network. With the help of mobile phones, and other simulated wireless networks, the VoLTE Lab setup can be operated in real-time for making VoLTE calls and also for interworking with PSTN and VoIP networks. MAPS™ is enhanced to a high density version and a special purpose 1U network appliance that is capable of high call intensity (hundreds of calls/sec) and high volume of sustained calls (tens of thousands of simultaneous calls/1U platform).
A very good description of MAPS and how it works is available in the HP Journal articles of August, 1990.
SECS I & SECII/GEM Protocols
This is the Semiconductor Equipment & Materials International (SEMI) Open Standard. The semiconductor process equipment manufacturers have identified the need for their equipment to communicate with a larger host computer system and developed SEMI Equipment Communications Standard (SECS), which defines parts of all seven ISO open system interconnect (OSI) communications layers.
SECS/GEM standardizes two-way communication within a network or serial cable that connect equipment and is independent of any particular programming or computer operating system.
As explained in the HP Journal article:
SECS I incorporates the use of RS-232-C cabling and pin definitions and a relatively simple line protocol. SECS II defines messages to request and send status information, transfer recipe data, report alarm conditions, send remote equipment control commands, and handle material transfer. SECS I uses a simple ENQ-ACK handshake across an RS-232-C line with checksums at the end of each message. SECS I also defines time-out intervals between handshake responses, individual message characters, and message responses. Message headers are defined in SECS I to include equipment identifiers, message identifiers, message block numbers, and other system information.
SECS II defines message types, format, content, and directions. SECS streams are groups of messages assigned to a general set of equipment functionality. Within each stream, the individual messages are assigned function numbers. For example, SECS stream 1 function 5 (abbreviated S1 F5) is a formatted equipment status request, and stream 1 function 6 is the reply with the status information. Similarly, stream 7 function 5 is used to request the transfer of a process recipe and stream 7 function 6 is used to transfer the recipe. SECS II also defines whether a reply is required or not, the message content and format (including data item definition headers), and whether a message may be used from equipment-to-host and/or host-to-equipment.
A major limitation of the SECS standard is that it defines messages and their content only; it does not define how the messages are used together to perform a function. Equipment manufacturers are left to decide what messages to use to perform functions that were performed manually before. This, of course, makes it difficult to develop translators for external systems to communicate with such equipment.
Figure 6: SEMI’s SECSII/GEM communication standard documents machine connectivity and control / recipes. (Source: HP Journal, July 1985)
Figure 6 show more details of the SECS II/GEM standard built on the OSI 7-level communication model (Figure 7). There is a good free SECS/GEM document available from SEMETECH.
Figure 7: The 7-Layer OSI communication standard. (Source: HP Journal, Aug. 1990)
Open Manufacturing Language (OML)
OML provides an Internet of manufacturing intelligent connectivity platform for all PCB assembly production machines and processes, be they automated or manual, while enabling the support such as planning, supply-chain, quality management, and corporate systems such as MES, ERP, and PLM. The standard is the proprietary development of Mentor Graphics/Valor and has hardware that can be purchased from them. The OML carries on the long standing tradition of ODB++, the PCB design communication standard from Valor. No information has been presented if OML conforms to either MAP or SECS II standards.
IPC has a subcommittee (2-13 Shop Floor Communications Subcommittee) that brought together leading software developers, machine vendors, assembly equipment manufacturers and their customers to work on development of a new IPC standard to meet the current and future needs of industry that will fill a gap identified by the group. This new standard will provide uniformity of data protocols that will allow ease of machine to machine communication.
As reported by David Bergman of IPC at the 2016 IPC APEX EXPO, IPC Committee Works Report:
The subcommittee is firmly committed to developing the standard and is also working to provide an easy-to-understand definition of Industry 4.0 and its significance. Machine vendors want to engage quickly and all parties agree that a replacement for the current IPC-2541, Generic Requirements for Electronics Manufacturing Shop-Floor Equipment Communication Messages (CAMX) is needed and demanded by industry and speed of execution is critical.
I think the fastest way to implement an electronics shop-floor data protocol is to throw in with our semiconductor brothers and adopt the SECSII/GEM standard from SEMI. They are usually pleased to see us follow their lead and they have a 35-year head start with many factories, established software and vendors already in place. There still is a need for the IPC Committee because CAD data/definitions, components, processes and tests all have to be set up for the SECSII/GEM standards.
LAN (Ethernet, IEEE-802.3 & TCP/IP)
802.3 is a technology that supports the IEEE 802.1 network architecture and also defines LAN method using CSMA/CD. It is the physical layer and data link layers for media access control (MAC) of wired Ethernet. Ethernet is increasingly popular for factory automation due to the availability of numerous sources for the communication hub. It is also available as a wireless standard in IEEE 802.11.
Transmission Control Protocol/Internet Protocol is the most common communication language or protocol for the Internet. TCP/IP provides the connectivity detailing how data should be transmitted, organized, addressed, routed and received at the destination.
This protocol is organized into four virtual layers which are used to sort all related protocols according to the needs of the network. From lowest to highest, as seen in Figure 7, the layers are: the link layer, containing communication methods for data that remains within a single network segment (link); the internet layer, connecting independent networks, thus establishing internetworking; the transport layer handling host-to-host communication; and the application layer, which provides process-to-process data exchange for applications.
Wireless and IoT
The Internet-of-Things is a growing popular trend. We will see if it applies to factory automation? Right now it is headed for consumer use and for control and monitoring applications that are highly dispersed, like energy monitoring. The role of security is a big question and the specifics of individual factory automation challenging. If IoT can create Group Controllers or cluster controllers that are compatible with factory networking, then it may play a role. Wireless on the other hand is a different situation.
As explained by the Advantech SMARTWORXTM web post:
Unfortunately, many machines need to do their jobs in locations that make wired data communications and AC power installations impractical. What’s needed is a low power wireless solution that can extend the network edge to include those locations while providing “five nines” uptime. Based on the wireless IEEE 802.15.4e standard, a SmartMesh IP mesh network is an excellent choice, even in harsh, dynamically changing RF environments.
SmartMesh IP mesh networks provide redundant routing to the network gateway, as every sensor node in a mesh network serves as a router. Each node can receive data from any other network node that is within range, and transmit data to any other network node that is within range. If one path to the network gateway fails, the network nodes will reroute through another. Devices can transmit data over long distances by passing data through intermediate devices to reach more distant ones, and the network gateway doesn’t need to be within range of every device on the network. This makes SmartMesh IP networks highly scalable.
Industry 4.0 Initiatives
The term "Industrie 4.0" originates from a project in the high-tech strategy of the German government, which provides for the computerization of manufacturing. The first industrial revolution mobilized the mechanization of production using water and steam power. The second industrial revolution then introduced mass production with the help of electrical power, followed by the digital revolution and the use of electronics and IT to further automate production.
The term was first used in 2011 at the Hannover Fair. In October 2012, the Working Group on Industry 4.0, chaired by Siegfried Dais and Henning Kagermann, presented a set of Industry 4.0 implementation recommendations to the German federal government. On 8 April 2013 at the Hannover Fair, the final report of the Working Group Industry 4.0 was presented.
Design Principles for Industry 4.0 Scenarios
Excerpts from a Working Paper by the Technische Universitat−Dormund:
There are six design principles in Industry 4.0. These principles support companies in identifying and implementing Industry 4.0 scenarios.
- Interoperability: the ability of cyber-physical systems (i.e. workpiece carriers, assembly stations and products), humans and Smart Factories to connect and communicate with each other via the Internet of Things and the Internet of Services
- Virtualization: a virtual copy of the Smart Factory which is created by linking sensor data (from monitoring physical processes) with virtual plant models and simulation models
- Decentralization: the ability of cyber-physical systems within Smart Factories to make decisions on their own
- Real-Time Capability: the capability to collect and analyze data and provide the derived insights immediately
- Service Orientation: offering of services (of cyber-physical systems, humans or Smart Factories) via the Internet of Services
- Modularity: flexible adaptation of Smart Factories to changing requirements by replacing or expanding individual modules
Figure 8: Equipment operation and GEM capability for industrial automation. (Source: HP Journal, July 1985).
Characteristic for industrial production in an Industry 4.0 environment are the strong customization of products under the conditions of highly flexibilized (mass-) production. The required automation technology is improved by the introduction of methods of self-optimization, self-configuration, Self-diagnosis, cognition and intelligent support of workers in their increasingly complex work
Current activities addressed the prevalence of the Internet of Things in manufacturing and the consequent technology-driven changes which promise to trigger a new industrial revolution. At Bosch, and generally in Germany, this phenomenon is referred to as Industry 4.0. The basic principle of Industry 4.0 is that by connecting machines, work pieces and systems, businesses are creating intelligent networks along the entire value chain that can control each other autonomously. Some examples for Industry 4.0 are machines which can predict failures and trigger maintenance processes autonomously or self-organized logistics which react to unexpected changes in production.
There are differences between a typical traditional factory and an Industry 4.0 factory. In the current industry environment, providing high-end quality service or product with the least cost is the key to success and industrial factories are trying to achieve as much performance as possible to increase their profit as well as their reputation. In this way, various data sources are available to provide worthwhile information about different aspects of the factory. In this stage, the utilization of data for understanding current operating conditions and detecting faults and failures is an important topic to research. e.g. in production, there are various commercial tools available to provide this protocol.
Wikipedia further explains what Industry 4.0 includes:
Overall Equipment Effectiveness (OEE) information to factory management in order to highlight the root causes of problems and possible faults in the system. In contrast, in an Industry 4.0 factory, in addition to condition monitoring and fault diagnosis, components and systems are able to gain self-awareness and self-predictiveness, which will provide management with more insight on the status of the factory. Furthermore, peer-to-peer comparison and fusion of health information from various components provides a precise health prediction in component and system levels and force factory management to trigger required maintenance at the best possible time to reach just-in time maintenance and gain near zero downtime.
Challenges which have been identifiedinclude:
- IT security issues, which are greatly aggravated by the inherent need to open up those previously closed production shops
- Reliability and stability needed for critical machine-to-machine communication (M2M), including very short and stable latency times
- Need to maintain the integrity of production processes
- Need to avoid any IT snags, those would cause expensive production outages
- Need to protect industrial knowhow (contained also in the control files for the industrial automation gear)
- Lack of adequate skill-sets to expedite the march towards fourth industrial revolution
- Threat of redundancy of the corporate IT department
- General reluctance to change by stakeholders
Next time, in Computer Aided Manufacturing Part 2, I will offer automation examples from personal projects I have been involved with.
- Industry 4.0 Smart Manufacturing for the Future
- Introduction to Serial Communications, TalTech Instrumental Software Solutions.
- IEEE Standard Codes
- IEEE-488, Wikipedia.
- Message Automation & Protocol Simulation (MAPS™), GL Communications, Inc.
- “Semiconductor Productivity at HP,” HP Journal, July 1985.
- SEMI Standard E30, General Equipment Model.
- IPC Status of Standardization; IPC Committee Home Pages
- Smart IoT Technology for Machine Condition Monitoring
- Hermann, M., Pentek, T., Design Principles for Industrie 4.0 Scenarios, Working Paper No. 01/2015, technische universitat-Dortmund, 2015.
- Industry_4.0, Wikipedia.
Happy Holden has worked in printed circuit technology since 1970 with Hewlett-Packard, NanYa/Westwood, Merix, Foxconn and Gentex. He is the co-editor, with Clyde Coombs, of the recently published Printed Circuit Handbook, 7th Ed. To contact Holden, click here.