Latest Building Automation Articles

Energy management controls optimize electrical systems via building automation, IoT sensors, BMS/SCADA integration, demand response, and load-shedding to improve power quality, reduce peak demand, and enhance HVAC, lighting, and motor efficiency in industrial facilities.

What Are Energy Management Controls?

Automated systems that monitor, control, and optimize electrical loads to boost efficiency, uptime, and power quality.

✅ Integrates PLCs, BMS, and SCADA for centralized load control

✅ Implements demand response, peak shaving, and load shedding

✅ Meters energy, analyzes power quality, and optimizes setpoints

Energy management controls are conservation tools implemented to control heating, energy consumption, lighting systems, heathing ventilation and air conditioning (HVAC) systems. Modern Direct Digital Control (DDC) systems, which can accurately control building systems, have become very cost-effective in recent years. As a result, they are replacing traditional manual and electromechanical building control systems in retrofitted buildings and being installed in almost all new commercial and institutional facilities. However, maximizing energy efficiency requires strategic facility management control methods for controlling the HVAC, power and communications systems. For a deeper look at modern strategies, the overview at advanced energy management explains integration trends across HVAC and lighting.

Regardless of the technology used, deciding which energy management control mode to apply is important. It is important to understand that these modes can be implemented using many available technology types. In many cases, simple on-off control is adequate and very appropriate. In other cases, the desired effect can be on with modulating controllers. The following are basic control modes. The accompanying diagrams will illustrate typical system performance. Practical frameworks for selecting modes are discussed in energy management systems resources available to facility teams.

The term system capacitance refers to the rate of response of a system to a stimulus. Systems with a large capacitance tend to resist change, and the effects of control are felt more slowly than with systems of smaller capacitance. Comparing the effect to a flywheel or relative mass is a good way to describe this concept. Another useful example to illustrate system capacitance is an instantaneous electric water heater (small volume of water) compared to a standard residential tank-type water heater. Upon energizing the heater elements, the water temperature in the tank unit changes much more slowly because it has more mass, and we say it has greater system capacitance. Understanding capacitance helps in tuning building energy management systems for stability under variable loads.

The term gain is a control term synonymous with sensitivity and is usually an adjustable amplification value used to tune the devices. For example, if a quicker response is desired for a small input change, the gain is increased in a stronger output reaction from the controller. These parameters are typically adjusted within a centralized building automation system interface to synchronize responses across equipment.

On-off Energy Management Controls

Also called two-position control, this rudimentary mode is used with either on or off equipment. A nominal setpoint exists but is only achieved in passing. A range of control values must be tolerated to avoid short-cycling the equipment, and temperature ranges are often fairly wide. In the case of equipment that cannot be modulated, this is often the only choice. The smoothness of control depends strongly upon the system capacitance; systems with very low capacitance can experience short cycling problems using two-position control. In practice, on-off strategies often reflect principles introduced in what is building automation guidance that relates simple control to overall system behavior.

Floating Energy Management Controls

This hybrid combination of on-off and modulating control is also called incremental control. As with on-off control, there is a control range (cut-in/cut out). However, unlike on-off control, floating control systems can maintain a mid-position of the controlled device instead of being limited to full-on or full-off. The controlled device holds its last position between the cut-in and cut-out thresholds. The process variable is not under control within this range, and it floats with the load until it crosses a threshold to get another incremental nudge in the correcting direction. This control is tighter than simple on-off control, and although tight than true modulating control, it is inexpensive and reliable. Equipment items from small HVAC terminal units to 1000 HP water chiller inlet vanes are controlled in this manner with good success. Note that floating control is limited to processes that change slowly, and floating control actuators are usually selected as slow-moving. Selecting floating control as part of a broader energy management approach can reduce wear while maintaining comfort within acceptable bands.

Proportional-only Control (P)

This is the basic modulating control and what most commercial pneumatic and analog electronic systems utilize. It is an error-sensing device with an adjustable gain or amplification. A control output is issued to regulate a process, and the magnitude of the output is directly proportional to the size of the error. This type of control is economical and reliable. However, a characteristic offset (residual error) is natural with this type of controller, and the size of the offset will increase with load. This offset occurs because an error must increase (further off setpoint) before an output increase can occur.

If the proportional energy management controls are too sensitive (gain set too high), the controller’s response will be excessive, and oscillation or hunting will occur. When this occurs, the controller output (and the equipment connected) will oscillate up and down, open and closed, etc., and the control action will not settle out. Training and commissioning within an organized energy management program help operators set appropriate gains and avoid persistent hunting.

Conclusion

Automatic energy management controls are useful for basic regulation and quality control of processes and environments. They can also be leveraged for energy savings through optimization. Properly applied, these systems are reliable and cost-effective. Returning to the chapter's intent, the stated purpose of this chapter was to focus on the application of automatic system controllers as a tool to achieve energy savings. The reader should review the titles of each section, reflect on the key topics taken away, and decide if the stated objective was met. It is hoped that the reader has gained insight into how automatic energy management controls can help achieve energy goals. Therefore, they will endeavour to put these systems to work, optimizing processes and saving energy.

From: Energy Management Handbook, 7th Edition, The Fairmont Press

Related Articles

• Building Automation Channel

Industrial automation communication connects PLCs, sensors, drives, and SCADA via protocols like PROFINET, Modbus, OPC UA, and Ethernet/IP, enabling deterministic control, interoperability, diagnostics, safety, and IIoT data across electrical systems and networks.

What Is Industrial Automation Communication?

Networked real-time data exchange between PLCs, sensors, HMIs, and SCADA using standardized industrial protocols.

✅ Supports deterministic Ethernet (TSN) and legacy fieldbus integration

✅ Enables real-time control, diagnostics, and predictive maintenance

✅ Interoperates via PROFINET, Modbus, EtherNet/IP, and OPC UA

In the early 20th century, process control systems and the manufacturing systems were designed based primarily on the mechanical technology and with analog devices. After the period, the pneumatic control technology and the hydraulic power were introduced. The pneumatic control technology made it possible to control remote systems by a centralized control system. These technologies are still very common.

At the beginning of 1960, a digital computer was for the first time really applied as a digital controller. The term direct digital control (DDC) was used to emphasize that the computer directly controls the process. In the 1960s, the application of a minicomputer was still a fairly expensive solution for many control problems. In the meantime, programmable logic controller (PLC) was developed and it replaced the conventional, relay-based controller, having relatively limited control functions. In addition, many technologies were developed for machine tools and discrete production processes. The numerically controlled (NC) machine tool became to be controlled by computers and the robot was developed in this period.

With the more widespread use of digital computers and the associated technologies, industrial communication networks became to be developed with or converted to digital transmission. Proprietary digital communication networks for industrial use started in the 1960s as computers for automation systems were first linked together.

In mid 70s, the first distributed computer control system (DCCS) was announced by Honeywell as a hierarchical control system with a large number of microprocessors. Since its introduction in mid 1970s, the concept of the DCCS spread widely in many industrial automation systems such as power plant control systems, manufacturing systems, etc. The installation of distributed control systems in the newly planned plants or replacement of existing analogue or centralized control systems is presently a common decision of enterprise management. In sectors like power generation, advanced energy management strategies leverage DCS data to optimize load balancing and maintenance planning across units.

The use of local area networks to interconnect computers and automation devices within an industrial automation system has become popular since 1980. The high capacity low cost communication offered by local area networks has made distributed computing a reality, and many automation services. The 

As deployments expanded, many organizations realized that the benefits of industrial networks include lower downtime, scalable integration, and improved data visibility across operations.

industrial automation systems are often implemented as an open distributed architecture with communication over digital communication networks. Achieving high availability requires the right mix of industrial network components such as managed switches, protocol gateways, and ruggedized edge controllers.

It is now common for users connected to a local area network to communicate with computers or automation devices on other local area networks via gateways linked by a wide area network. Similar architectures now extend into transportation, where smart city automated level crossings depend on resilient networking to coordinate sensors, barriers, and central oversight.

As the industrial automation systems becomes large and the number of automation devices increases, it has become very important for industrial automation to provide standards which make it possible to interconnect many different automation devices in a standard way. Considerable international standardization efforts have been made in the area of local area networks. The Open Systems Interconnection (OSI) standards permit any pair of automation devices to communicate reliably regardless of the manufacturer. To plan these interoperable systems, designers often reference hierarchical levels in industrial networks to align plant-floor operations with supervisory and enterprise layers.

Industrial networks span many manufacturing applications. Standard industrial networks using digital communication technologies cover a wide range of manufacturing applications. In many applications, the types of devices and performance determine the type of network. Contrast the needs of two devices -- a proximity sensor used on a conveyor belt compared to a control valve used in a petroleum refinery. The proximity sensor has a single function - to transmit a Boolean on/off signal indicating the proximity of an object. We can accommodate this signal in a few bits of data. Diagnostic information from the sensor is probably limited to a single "health" indicator, which again requires very little data. However, we can expect the control valve to provide very sophisticated control functions and diagnostics, such as number of cycles since last servicing, packing friction, and ambient operating temperature. These parameters can be extremely critical in an environment such as a refinery -- failures can result in dangerous situations and costly downtime. Clearly, the proximity sensor and the control valve have different network requirements. Therefore, different types of industrial networks must address a variety of different needs. We must select the right network to address our specific application requirements.

What is an Industrial Network? By definition, an industrial network requires geographical distribution of the physical measurement I/O and sensors or functional distribution of applications. Most industrial networks transfer bits of information serially. Serial data transfer has the advantage of requiring only a limited number of wires to exchange data between devices. With fewer wires, we can send information over greater distances. Because industrial networks work with several devices on the same line, it is easier to add a new device to existing systems. Comparing fieldbus, Ethernet, and wireless backbones, understanding transmission methods in industrial networks helps engineers match latency, bandwidth, and environmental constraints.

To make all this work, our network must define a set of rules -- a communication protocol -- to determine how information flows on the network of devices, controllers, PCs, and so on. With improved communication protocols, it is now possible to reduce the time needed for the transfer, ensure better data protection, and guarantee time synchronization, and real-time deterministic response in some applications. Industrial networks also ensure that the system sends information reliably without errors and securely between nodes on the network.

For the lower level communication network for industrial automation, the industrial local area network solutions such as MAP are too expensive and/or do not reach the required short response times, depending on the application. The fieldbuses have been, therefore, developed to meet these requirements, and many efforts are now being made to make fieldbus standards for industrial automation applications. The same field-level connectivity principles underpin a modern building automation system where HVAC, lighting, and security integrate reliably across facilities.

Read More: Hierarchical Levels in Industrial Communication Networks

Related Articles

• Building Automation Channel

Hierarchical Levels Industrial Networks align device, control, and enterprise layers across PLCs, SCADA, MES, and ERP, using fieldbus, Ethernet/IP, and Profinet to ensure deterministic control, real-time data, cybersecurity, and scalable OT-IT integration.

What Are Hierarchical Levels Industrial Networks?

Layered OT networks linking devices, control, and enterprise systems for real-time, deterministic, secure automation.

✅ Defines device, control, and enterprise layers in OT/ICS

✅ Maps PLCs, HMIs, drives, and sensors to appropriate network tiers

✅ Ensures determinism, redundancy, and EMC-compliant cabling practices

The industrial automation systems can be very complex, and it is usually structured into several hierarchical levels. Each of the hierarchical level has an appropriate communication level, which places different requirements on the communication network. Figure 1.1 shows an example of the hierarchy of an industrial automation system. For a broader overview of protocols and trends, industrial automation communication resources explain how hierarchy influences network design across levels.

Industrial networks may be classified in several different categories based on functionality - field-level networks (sensor, actuator or device buses), control-level networks (control buses) and information-level networks. Organizations adopt these layers to gain measurable efficiencies, and the benefits of industry networks include improved interoperability, uptime, and lifecycle support.

We primarily use sensor and actuator buses to connect simple, discrete devices with limited intelligence, such as a photo-eye, limit switch, or solenoid valve, to controllers and computers. Sensor buses such as ASI and CAN are designed so information flow is reduced to a few bits and the cost per node is a critical factor. Selecting cabling, interfaces, and gateways depends on understanding industrial network components that shape reliability, diagnostics, and scalability.

Field level

The lowest level of the automation hierarchy is the field level, which includes the field devices such as actuators and sensors. The elementary field devices are sometimes classified as the element sublevel. The task of the devices in the field level is to transfer data between the manufactured product and the technical process. The data may be both binary and analogue. Measured values may be available for a short period of time or over a long period of time.

For the field level communication, parallel, multiwire cables, and serial interfaces such as the 20mA current loop has been widely used from the 

past. The serial communication standards such as RS232C, RS422, and RS485 are most commonly used protocols together with the parallel communication standard IEEE488. Those point-to-point communication methods have evolved to the bus communication network to cope with the cabling cost and to achieve a high quality communication. Comparisons of copper, fiber, and wireless media, along with signaling and topology choices, are covered in transmission methods for industrial networks to help match performance with environmental constraints.

Field-level industrial networks are a large category, distinguished by characteristics such as message size and response time. In general, these networks connect smart devices that work cooperatively in a distributed, time-critical network. They offer higher-level diagnostic and configuration capabilities generally at the cost of more intelligence, processing power, and price. At their most sophisticated, fieldbus networks work with truly distributed control among intelligent devices like FOUNDATION Fieldbus. Common networks included in the devicebus and fieldbus classes include CANOpen, DeviceNet, FOUNDATION Fieldbus, Interbus-S, LonWorks, Profibus-DP, and SDS.

These characteristics also underpin infrastructure applications such as rail crossings, where distributed sensors and controllers coordinate safety logic, as seen in smart city automated level crossings that rely on deterministic messaging.

Nowadays, the fieldbus is often used for information transfer in the field level. Due to timing requirements, which have to be strictly observed in an automation process, the applications in the field level controllers require cyclic transport functions, which transmit source information at regular intervals. The data representation must be as short as possible in order to reduce message transfer time on the bus.

Control Level

At the control level, the information flow mainly consists of the loading of programs, parameters and data. In processes with short machine idle times and readjustments, this is done during the production process. In small controllers it may be necessary to load subroutines during one manufacturing cycle. This determines the timing requirements. It can be divided into two: cell and area sublevels.

Cell Sublevel

For the cell level operations, machine synchronizations and event handlings may require short response times on the bus. These real-time requirements are not compatible with time-excessive transfers of application programs, thus making an adaptable message segmentation necessary.

In order to achieve the communication requirements in this level, local area networks have been used as the communication network. After the introduction of the CIM concept and the DCCS concept, many companies developed their proprietary networks for the cell level of an automation system. The Ethernet together with TCP/IP (transmission control protocol/internet protocol) was 

accepted as a de facto standard for this level, though it cannot provide a true real-time communication. Similar patterns appear in buildings, where building automation systems integrate HVAC, lighting, and security over IP while reserving real-time tasks for specialized buses.

Many efforts have been made for the standardization of the communication network for the cell level. The IEEE standard networks based on the OSI layered architecture were developed and the Mini-MAP network was developed in 1980s to realize a standard communication between various devices from different vendors. Some fieldbuses can also be used for this level.

Area sublevel

The area level consists of cells combined into groups. Cells are designed with an application-oriented functionality. By the area level controllers or process operators, the controlling and intervening functions are made such as the setting of production targets, machine startup and shutdown, and emergency activities.

We typically use control-level networks for peer-to-peer networks between controllers such as programmable logic controllers (PLCs), distributed control systems (DCS), and computer systems used for human-machine interface (HMI), historical archiving, and supervisory control. We use control buses to coordinate and synchronize control between production units and manufacturing cells. Typically, ControlNet, PROFIBUS-FMS and (formerly) MAP are used as the industrial networks for controller buses. In addition, we can frequently use Ethernet with TCP/IP as a controller bus to connect upper-level control devices and computers.

Information level

The information level is the top level of a plant or an industrial automation system. The plant level controller gathers the management information from the area levels, and manages the whole automation system. At the information level there exist large scale networks, e.g. Ethernet WANs for factory planning and management information exchange. We can use Ethernet networks as a gateway to connect other industrial networks. At this level, analytics platforms often drive energy KPIs, and advanced energy management strategies leverage network data for optimization and demand response.

Related Articles

• Building Automation Channel

Energy Management Program optimizes electrical loads via SCADA, submetering, and analytics, driving energy efficiency, demand response, peak shaving, load forecasting, and power factor correction to reduce kWh, cut OPEX, and improve power quality and reliability.

What Is an Energy Management Program?

An engineered method to monitor and control electrical loads, boosting efficiency, reliability, and cutting costs.

✅ Integrates SCADA, submeters, and IoT sensors for real-time visibility

✅ Implements ISO 50001, KPIs, and M&V for continuous optimization

✅ Enables demand response, peak shaving, and power factor correction

An energy management program is increasingly important in industrial, commercial, and institutional power systems due to growing concerns about energy efficiency, costs, and environmental impact. Implementing an effective energy management program (EMP) can help businesses save money, reduce their carbon footprint, and achieve sustainability goals. This article will delve into the key components of an energy management program and discuss how it can benefit businesses in various sectors. To understand the broader scope of best practices, resources on energy management provide context for implementation across sectors.

An effective EMP typically includes energy efficiency measures, energy audits, energy conservation strategies, building automation, energy monitoring, demand response initiatives, sustainable energy policies, and the implementation of EM systems. Facility management plays a crucial role in ensuring the success of such programs. For teams new to these concepts, a concise primer on what is building automation can help align terminology and roles.

One of the primary goals of an energy management program is to increase energy efficiency. This can be achieved by identifying areas where energy is wasted and implementing measures to reduce energy consumption. For instance, energy-efficient lighting, heating, and cooling systems can significantly reduce energy usage in commercial and institutional buildings. Incorporating energy management controls enables precise scheduling and setpoint optimization for measurable savings.

Energy audits are a vital component of an EMP, as they help identify areas of energy waste and provide recommendations for improving energy efficiency. These audits involve a thorough assessment of a facility's energy consumption patterns and equipment performance, which can lead to the implementation of cost-effective energy-saving measures. Audit findings are often operationalized through energy management systems that track KPIs and verify results.

Energy conservation strategies are another crucial aspect of an energy management program. These strategies aim to minimize energy consumption without compromising operational efficiency. Examples of energy conservation measures include optimizing equipment performance, implementing energy-saving operational procedures, and promoting energy-conscious behavior among employees. Modern analytics and automation in advanced energy management support continuous improvement in conservation programs.

Building automation systems play a significant role in energy management programs by allowing for the centralized control and monitoring of various building systems, such as HVAC, lighting, and security. These systems can help optimize energy usage by automatically adjusting settings based on factors like occupancy, time of day, and weather conditions. Selecting an open-protocol building automation system improves interoperability with meters and sub-systems for broader control.

Energy monitoring is essential for tracking the effectiveness of an energy management program. By continuously measuring and analyzing energy consumption data, businesses can identify trends, pinpoint inefficiencies, and implement corrective measures to optimize energy use further. Many organizations centralize this function within building energy management systems to visualize trends and trigger alerts.

Demand response initiatives can help businesses in industrial, commercial, and institutional power systems participate in energy markets by adjusting their energy consumption in response to market signals, such as electricity price fluctuations or grid reliability issues. This can help businesses reduce energy costs and support grid stability.

Sustainable energy policies guide businesses in adopting cleaner energy sources and reducing their reliance on fossil fuels, such as oil and gas. Examples of sustainable energy sources include solar, wind, and hydroelectric power. Integrating these sources into a facility's energy mix can help reduce greenhouse gas emissions and promote long-term sustainability.

EM systems support energy management programs by providing a platform for monitoring, controlling, and optimizing energy usage across a facility. These systems can help businesses identify opportunities for energy savings, improve equipment performance, and reduce energy costs.

Related Articles

• Building Automation Channel

Building Energy Management Systems integrate automation, efficiency, and monitoring of HVAC, lighting, and electrical loads. These systems optimize energy performance, reduce costs, and support sustainability goals for smart buildings and modern facilities.

What are Building Energy Management Systems?

Building Energy Management Systems (BEMS) are intelligent platforms that monitor, control, and optimize building energy usage for greater efficiency and sustainability.

✅ Automate HVAC, lighting, and power systems

✅ Lower operating costs through energy efficiency

✅ Support smart building and sustainability initiatives

Understanding Building Energy Management Systems

Building Energy Management Systems are crucial tools for optimizing energy use in industrial, commercial, and institutional facilities. By integrating advanced technologies such as the Internet of Things (IoT), machine learning, and predictive analytics, BEMS enable significant cost savings, improved performance, and measurable progress toward sustainability. The focus of building management systems is on long-term energy efficiency in commercial buildings, reducing consumption while enhancing comfort. Building Energy Management Systems are closely tied to advanced energy management strategies that help facilities optimize efficiency through real-time monitoring and automation.

How Building Energy Management Systems Work

A BEMS combines hardware and software components to monitor, control, and optimize energy consumption. Sensors, controllers, and actuators collect data on power usage, temperature, humidity, and occupancy. The system software utilizes algorithms and analytics to identify inefficiencies, optimize HVAC and lighting systems, and provide facility managers with actionable insights. IoT devices strengthen this process by enabling real-time communication between equipment, ensuring responsive and precise adjustments. A well-designed building automation system integrates HVAC, lighting, and power controls into a unified BEMS platform that improves performance and sustainability.

Generic BEMS Features: Comparison Table

Key Benefits of BEMS

Building Energy Management Systems improve efficiency by identifying waste and optimizing performance. Facility managers can address equipment malfunctions, poor insulation, or inefficient lighting while reducing carbon footprint. These adjustments lead to:

• Lower operating costs through reduced consumption

• Enhanced occupant comfort and productivity

• Long-term sustainability through emissions reduction

Organizations that implement energy management systems benefit from reduced costs, increased operational control, and the ability to meet regulatory requirements.

Case Studies and Industry Leaders

Global companies such as Schneider Electric, IBM, and Emerson offer BEMS platforms that demonstrate measurable returns. For example, AI-driven HVAC optimization has shown reductions of up to 15% in energy use by automatically adjusting based on occupancy and weather conditions. Real-world implementations demonstrate how BEMS not only reduce costs but also extend equipment life and enhance resilience. To achieve maximum value, facility managers often combine BEMS with specialized energy management controls that automate schedules, adapt to occupancy, and respond to changing conditions.

Standards and Certification

BEMS adoption aligns with international standards, such as ISO 50001, which provides a framework for continuous improvement in energy performance. Certification under ISO 50001 enhances credibility, helps organizations meet regulatory requirements, and supports recognition through programs like LEED and ENERGY STAR.

Best Practices for Implementation To maximize benefits, organizations should:

• Conduct comprehensive energy audits to pinpoint inefficiencies

• Set achievable energy-saving targets using benchmarking data

• Establish monitoring and verification systems for performance tracking

• Engage staff in awareness and training programs

• Update BEMS continuously as technology evolves

Sustainability goals are supported by green energy integration, allowing Building Energy Management Systems to incorporate renewable sources into daily operations.

Demand Response and Future Trends

Demand response strategies are becoming integral to BEMS. These involve adjusting consumption in response to grid fluctuations, price signals, or periods of peak demand. Automated demand response enables facilities to reduce their load without compromising comfort, often earning financial incentives and contributing to grid stability. Looking forward, artificial intelligence, predictive maintenance, and data-driven decision-making will further enhance the role of BEMS in creating smarter, more sustainable buildings. Successful deployment requires a broader energy management program that aligns strategy, technology, and staff engagement across the organization.

Building Energy Management Systems are no longer optional—they are essential for organizations seeking efficiency, cost savings, and environmental stewardship. By integrating advanced technology, following best practices, and aligning with global standards, BEMS deliver long-term value while helping to meet the urgent demand for sustainable building operations.

Related Articles

• Building Automation Channel

Industrial network components enable reliable Ethernet, fieldbus, and IIoT connectivity across PLCs, HMIs, drives, and sensors, using managed switches, routers, protocol gateways, and cybersecurity firewalls for real-time control, redundancy, and deterministic data.

What Are Industrial Network Components?

Hardware like switches, routers, gateways, and I/O modules that link PLCs and sensors for secure, deterministic control.

✅ Managed Ethernet switches enforce VLANs, QoS, and ring redundancy

✅ Gateways bridge Modbus, PROFIBUS, and PROFINET protocols

✅ Industrial routers add VPN, firewall, and IEC 62443 security

Industrial Network Components

In larger industrial and factory networks, a single cable is not enough to connect all the network nodes together. We must define network topologies and design networks to provide isolation and meet performance requirements. In many cases, because applications must communicate across dissimilar networks, we need additional network equipment. The following are various types of network components and topologies:

For an overview of how devices exchange data across varied protocols, see the guide on industrial automation communication best practices for plant networks.

• Repeaters -- a repeater, or amplifier, is a device that enhances electrical signals so they can travel greater distances between nodes. With this device, we can connect a larger number of nodes to the network. In addition, we can adapt different physical media to each other, such as coaxial cable to an optical fiber.
• Router -- a router switches the communication packets between different network segments, defining the path.
• Bridge -- with a bridge, the connection between two different network sections can have different electrical characteristics and protocols. A bridge can join two dissimilar networks and applications can distribute information across them.
• Gateway -- a gateway, similar to a bridge, provides interoperability between buses of different types and protocols, and applications can communicate through the gateway.

In planning placement of routers, bridges, and gateways, it's useful to map the hierarchical levels of industrial networks across field, control, and enterprise layers.

Network Topology

Industrial systems usually consist of two or more devices. As industrial systems get larger, we must consider the topology of the network. The most common network topologies are the bus, star, or a hybrid network that combines both. Three principal topologies are employed for industrial communication networks: star, bus, and ring as shown in Figure 3. Understanding media choices and signaling options is essential, and the overview of transmission methods for industrial networks explains tradeoffs between copper, fiber, and wireless.

A star configuration contains a central controller, to which all nodes are directly connected. This allows easy connection for small networks, but additional controllers must be added once a maximum number of nodes are reached. The failure of a node in a star configuration does not affect other nodes. The star topology has a central hub and one or more network segment connections that radiate from the central hub. With the star topology, we can easily add further nodes without interrupting the network. Another benefit is that failure of one device does not impair communications between any other devices in the network; however, failure of the central hub causes the entire network to fail. These design choices tie directly to the benefits of industrial networks that improve scalability and resilience.

In the bus topology, each node is directly attached to a common communication channel. Messages transmitted on the bus are received by every node. If a node fails, the rest of the network continues in operation as long as the failed node does not affect the media. This shared medium approach is often integrated under a facility's building automation system where distributed controllers share status and control signals.

In the ring topology, the cable forms a loop and the nodes are attached at intervals around the loop. Messages are transmitted around the ring passing the nodes attached to it. If a single node fails, the entire network could stop unless a recovery mechanism is not implemented.

In transportation settings like automated level crossings environments, deterministic performance and failover are crucial for safety.

For most networks used for industrial applications, we can use hybrid combinations of both the bus and star topologies to create larger networks consisting of hundreds, even thousands of devices. We can configure many popular industrial networks such as Ethernet, FOUNDATION Fieldbus, DeviceNet, Profibus, and CAN using hybrid bus and star topologies depending on application requirements. Hybrid networks offer advantages and disadvantages of both the bus and star topologies. We can configure them so failure of one device does not put the other devices out of service. We can also add to the network without impacting other nodes in the network. Hybrid architectures also support advanced energy management strategies that balance load and reduce downtime during maintenance.

Related Articles

• Building Automation Channel