Selecting the right sensors, along with the processors, memory, and timing devices, is key to advancing the capabilities of automated building management.
Presence detection solutions are not one-size-fits-all. The core sensors and technologies required to accomplish the variety of features and use cases are as diverse as the applications and environments in which they are used. This series of articles on presence detection will feature examples of use cases across commercial, industrial and retail applications, and will highlight core sensing capabilities, networking and processing considerations, and technology solutions that can be architected together to achieve the desired feature set.
In each case, system architectures must take into consideration environmental factors, the shape, structure and layout of the space, power availability, node-to-node communications requirements and constraints, as well as data and information security. The first installment covered social distancing in retail applications. The second installment (below) focuses on presence detection for commercial building automation.
Human interaction with our products and environments is becoming increasingly frictionless. At first driven by consumer expectation of ease of use, the pandemic of 2020 is accelerating this trend. Whereas before, touchless and automated access and control were matters of convenience, they are now also a matter of health and safety. We have become hyperconscious of every surface, handle, and button we have to physically engage. Automated presence detection systems eliminate the need to touch common points like light switches and door handles.
In addition to reducing or eliminating touch points, automated presence detection systems can trigger air quality management and HVAC systems to promote healthy air flow and air purification, optimized for the exact occupancy and occupant coordinates. Healthy air flow is critical in minimizing the circulation and spread of both dust and airborne infection disease particles.
Advanced levels of presence detection are not only a matter of convenience and cleanliness, they will also have a significant impact on building safety and security. Imagine how much more safely and efficiently emergency service personnel could respond to fires or medical alerts if the building itself accounted for the whereabouts of all of its occupants.
The digitalization of a building floorplan combined with the exact locations of every person in the building could be transmitted to first responders dynamically, and could autonomously navigate them to the emergency in real time. By navigating directly to the known location of a person, the risk to fire response personnel is also greatly reduced.
While some level of automation is common today, it tends to be fairly simplistic, and does not allow us to fully capitalize on all of the health and safety benefits that could be realized from a more accurate, interconnected solution.
Advancements in presence detection capabilities
Rudimentary forms of presence detection have existed in building controls for many years. Many office and residential spaces use simple motion detection devices to activate everything from lights to security devices and climate control systems. Typically, these systems are implemented using basic passive infrared (PIR) or radar-based technologies to detect motion and trigger events such as device wakeup. You have probably encountered these systems in your own environments: room lighting that turns on when you enter, a touchscreen thermostat that “wakes up” when you walk past, or a security camera that only records when it is “tripped” by a moving object.
While convenient, these systems have a number of limitations. They lack the ability to differentiate between people and other moving objects, and thus are susceptible to false alarms triggered by animals, or even inanimate objects blown by the wind. And if you’ve ever worked in an office with automated lighting control, then perhaps you’ve experienced firsthand being plunged into total darkness after too many minutes of typing at your computer without enough motion to keep the lights on! In addition to these issues, presence detection systems of the future will require advanced functionality that the current systems cannot provide, such as people counting, or even exact position within a given space.
Clearly, such examples of false positives and false negatives demonstrate a need for the systems to be more accurate if they are to inform more sophisticated building management systems and safety protocols. Choosing the appropriate sensor technologies is key in elevating the capabilities of these systems. Adding processing and memory to these localized nodes is also necessary to increase the detection fidelity, and to create additional feature sets. A variety of sensor technologies can be considered for this application, and in some cases, by combining sensor technologies, the accuracy, efficiency and functionality of the system can be greatly improved.
Time of flight (ToF) optical sensors are well suited for many of the advanced presence detection features described here. Where PIR sensors provide a binary indication of motion within the field of view, ToF sensors provide a distance measurement to the nearest object. As well, multi-zone ToF sensors can determine direction of motion, which is particularly useful in differentiating between entrance and exit events.
By mounting a ToF sensor above a door and combining it with the appropriate processing logic and memory for event triggers and counting, the number of occupants in a room can be exactly tracked. In this application, ToF is also well suited for more reliable determination of a person because it can filter out other objects based on measured height. For even more accurate location information, several such sensor nodes could be placed around a given room or space. Occupancy tracking in this fashion would be much more difficult to achieve using PIR sensors due to their lack of object and motion direction differentiation.
More sophisticated optical technologies such as global shutter, thermal imaging, and 3D scanning would provide a very high level of sensing capability, including absolute object recognition and tracking. Development of such a system is becoming more and more turnkey with widespread availability of off-the-shelf image processing libraries that can be embedded on the edge devices. However, systems based on optical sensors would be data and computing intensive, and are likely to be cost prohibitive to deploy on mass scale.
Ultrasonic microphones could also be used to create a presence detection sensor node, and are an excellent choice for determining presence. They are sensitive enough to pick up the sound of someone typing or even breathing, and in most office environments, are capable of isolating these sounds from low level ambient background noise. They would, however, have limited use in tracking occupancy level, and the ability to differentiate between humans and other animals would be dependent on how substantially unique breathing characteristics are between different species.
Most current presence detection nodes do not include any advanced local processing capabilities beyond signal conditioning and some very basic data filtering logic. These nodes will need to include microcontrollers or processors, real time clocks or timing devices, and embedded memory in order to increase their level of intelligence and provide the more advanced levels of presence detection necessary for automated building management.
Both ultrasonic microphones and PIR sensors do provide excellent “wake up” signals for intelligent presence detection nodes. This significantly reduces the power consumption of the overall sensor node by activating the optical sensor only when there is indication of an event. Additionally, this would serve as a wake up signal to the embedded microcontroller, where for the majority of the time the microcontroller (MCU) would reside in a low power or sleep state.
Interconnectivity with building management solutions
Most of these legacy systems do not include any form of connectivity other than an on-device integration to provide the switching logic for the function being controlled. They are localized, used for the sole purpose of triggering a response from the device they are initiating — for example, the light in a particular room. In order for the presence information to be used by a centralized building management software, the presence detection device will need to communicate its events to a central data collection point, like a building controller or gateway, or directly to a cloud-based data management repository.
Historically, most building control infrastructure has relied on wired connectivity, but wireless communication protocols are being deployed coexistent to wired infrastructure in newer building control systems. Wireless communications offer greater flexibility in installing nodes and adding new building control features, eliminating the need for invasive rewiring. As wireless communication protocols increase in reliability and signal range, they will likely become standard as part of the building communication infrastructure. With the inclusion of presence detection events and data, high bandwidth communication becomes more important than ever before, particularly if video streaming is included.
The most common building automation communication protocol is BACnet. BACnet provides a standard by which the object types and services are defined within the protocol. Any device that is part of the building automation schema can participate via this protocol, including HVAC, fire & security nodes, and lighting control. This is advantageous because it allows for interoperability between devices and device suppliers, such that a building owner is not necessarily supplier-limited when choosing new or additional equipment.
There are a number of physical layers and data links approved for use with the BACnet protocol, including RS-232, RS-485, Ethernet and variations of Ethernet/IP for wired connectivity. For wireless connectivity, many building automation equipment suppliers have developed proprietary 900-MHz or 2.4-GHz wireless radios for BACnet implementation.
Zigbee was approved as the first mesh networking wireless standard for BACnet. There are several emerging data links that would be appropriate for building automation, which could significantly improve installation and maintenance conditions as well, including SPE (wired) and 5G (wireless).
Architecturally, many building automation node devices are routed to a centralized data collection point, or to a router (if all devices are on BACnet) or gateway (if there are multiple communication protocols in use). For wired infrastructures, this is especially necessary to minimize physical cable routes. However, as more building management software platforms move from physical on-site servers to cloud platforms, wireless connectivity will become more popular and will drive the already increasing availability of direct-to-cloud options for edge devices.
Generally, building automation systems can be integrated with other core functional components such as HVAC and security on common power and communication busses. However, fire and safety systems often run on separate power and communication networks in order to ensure their uptime and availability. Thus, integrating fire and safety nodes with a centralized building automation system may require some redundancy in the communication networks or nodes in order for them to feed information directly to the safety loop in parallel to providing information to a general building automation system.
Presence detection and the future of building management
Sensor and edge processing technologies have advanced to the point that intelligent, feature-rich presence detection systems can be available on a mass scale. The broad availability of hardware, firmware and software kits specifically designed for presence detection greatly reduces the time and human capital necessary to develop these systems. The core components are cost effective, and the benefits provided will greatly improve building safety and energy efficiency, such that measurable financial value is realized.
Intelligent presence detection solutions will become a critical data source for automated building management systems. Nearly all suppliers of commercial building equipment, from HVAC to safety, security and access solutions, have invested heavily in automated building management software and digital platforms. These platforms aggregate data from all of the building equipment and process that data to provide a comprehensive picture of building functionality, safety, status, efficiency and health. The potential of these platforms is only limited by the amount of physical information that is provided by the building itself. As we move into the future, intelligent presence detection will provide information critical to the full automation of building management.
— Andrea Berry is the market development manager of Industrial group at STMicroelectronics