TECH BRIEFS EBOOK 2020 Guide to Smart Sensor Technology, Connectivity and the IoT TECH BRIEFS EBOOK 3 Contents 3 The Expanding Role of Sensors in the IoT/IIoT 6 Smart Sensor Technology for the IoT 11 Networking the IoT with IEEE 802.15.4/6LoWPAN 11 14 The Sensors Behind the GEN II Wearable Device 18 Key Factors to Consider When Designing a Smart Factory 20 Executive Forum: Sensors & the IoT 14 18 ABOUT ON THE COVER The increasing variety of Internet of The IoT, sensors, and machine vision Things (IoT) applications, whether for city are powerful tools many companies are infrastructures, factories, or wearable integrating into their manufacturing devices, is driving predictions that the techniques. Augmented reality can be sales volume for sensors will reach 75 used to connect human personnel with billion units by 2025. The 2020 Guide to the digital spectrum. Learn more in the Smart Sensor Technology, Connectivity article “Key Factors to Consider When and the IoT compiles the top resources in Designing a Smart Factory” on page 18. smart sensor technology from Tech Briefs and Sensor Technology magazines. 2 SMART SENSORS EBOOK Fig. 1 Dual optical image image stabilization (OIS) sensors. The Expanding Role of Sensors in the IoT/IIoT New Applications Are Demanding New and More Sophisticated Sensors. he increasing variety of applications for the Internet of more intelligent and to achieve ever higher levels of performance. Things is driving predictions that the sales volume for For the foreseeable future, this trend will be seen both for con- sensors will reach 75 billion units by 2025. Applications sumer applications (IoT) and industrial applications (IIoT), although unforeseen just five years ago, some of which are de- generally, the requirements for industrial applications are an order scribed in this article, are requiring sensors to become of magnitude more demanding than for consumer applications. T Fig. 2 Checking on machine performance. SMART SENSORS EBOOK 3 THE EXPANDING ROLE OF SENSORS Fig. 3 Drone out for delivery. Smart Phones noise, to provide the best possible user experience. For the very high Consumers are now looking for a level of photo quality in slim smart- precision required by VR and AR controllers, sensors also need high phones that had earlier only been possible with expensive and bulky resolution to be able to accurately handle the slow and precise move- DSLR cameras — and this while walking, if not running. To achieve such ments of a hand. image quality with the limited optics that can be accommodated in such a tight space, OEMs have deployed Optical Image Stabilization (OIS) Navigation and Electronic Image Stabilization (EIS) solutions. The performance of Dead-reckoning systems are used for navigation in both consumer the OIS/EIS components, especially the motion sensor, has a major im- and commercial applications. They provide location data in the ab- pact on overall performance. For example, the Google Pixel 2 device, sence of GNSS/GPS signals by means of inertial measurement units which has a camera with both OIS and EIS, received the highest DXO (IMU), which use linear acceleration information derived from ac- Mark score from DxOMark Image Labs ever given to a smartphone. The celerometers, and angular rotation rate from gyroscopes, to calculate technology that led to that high performance is a motion tracking sensor altitude, angular rate, linear velocity, and position. The accuracy of with extremely low gyroscope and accelerometer noise (<0.004 these measurements is critical because errors are additive — they in- dps/√Hz and <100 µg/√HZ respectively), sensitivity error within 0.5%, crease over time. For high-precision navigation, a gyroscope needs and very tight temperature stability (less than ±0.016%/°C). to have extremely low gyro offset for temperature (between 3 to 5 mdps/°C) and low gyro noise density (below 4 mdps/√Hz). The Variety of Realities: VR, AR, and XR It is not just cameras that require precise motion sensor perform- Location ance. Virtual reality (VR), augmented reality (AR), and mixed reality A promising consumer application for dead-reckoning navigation, (XR) all need low noise and extremely good temperature stability. is to sense one’s location inside a shopping mall. It is particularly chal- For these applications, the gyroscope noise requirement is similar lenging to sense the floor someone is on. It would allow users to know to that for OIS, (<0.004 dps/√Hz), but the ac celerometer noise has which shops are near them. But more importantly, it could save time to be even lower, (<75 µg/√HZ). Other key parameters are a very low and lives by providing emergency services with the specific floor and sensitivity error (<0.5%) for both gyroscope and accelerometer, and location where the mobile caller requested help, rather than searching also good temperature stability (<10 mdps/~C) for the gyroscope. floor by floor. This can be achieved with high-precision, low-noise Another system-level feature that is beneficial for VR/AR/XR appli- pressure sensors that can measure individual stairs. This is now cations is the ability to synchronize the various sensors to a ppm-level achievable because pressure sensors are available that can go as low (0.0001%) accuracy system clock, so that timing errors stemming as one pascal, or about 10 cm, in precision. from less accurate internal oscillator clocks (1% clock error for PLL) can be avoided in applications that depend on precise timing. Factory Maintenance VR stand-alone head-mounted devices (HMD) especially, need Predictive maintenance (PdM) is one of the most important appli- good temperature linearity and stability, as well as low hysteresis and cations for sensors in the IIoT. It is a system in which machine and 4 SMART SENSORS EBOOK THE EXPANDING ROLE OF SENSORS other processing parameters are continuously monitored. Managers lenging environments. These ultrasonic solutions can meet the can therefore have an ongoing picture of machine health throughout needs of access control: a false acceptance rate (FAR — giving ac- a factory, enabling them to schedule maintenance when data indi- cess to an unauthorized person) of at least one in 50,000 and false cates there might be an impending problem. This is an alternative to rejection rate (FRR — not giving access to an authorized person) of waiting for a failure to occur or shutting down at regular intervals less than one in 50. whether or not it is necessary. Continuous online monitoring can provide benefits such as reduc- What’s Ahead ing downtime by as much as 70%, extending motor lifetimes by up These applications are only the tip of the iceberg for sensor to 30%, and reducing energy consumption by up to 10%. Although applications in the rapidly growing world of interconnectivity. these types of sensors are now being integrated into new production There is a push-pull relationship between sensor performance equipment, they can also be added to older equipment. and applications. The proliferation of new and improving appli- cations drives the birth of new sensor technologies and the con- Agriculture stant improvement of existing sensor performance. At the same Another example is driverless agri cultural tractors. In addition to time the availability of new types of sensors and higher levels the other requirements for autonomous vehicles, tractors have to deal of performance can suggest applications that weren’t pos- with extreme vibration, which can cause navigational errors because sible before. These two trends will be the engine to of its effects on the motion tracking sensors. The sensors in the pre- drive the ever expanding IoT and IIoT connected cision navigation system therefore require vibration isolation — bias world. stability of below 2°/hr for gyroscopes and below 10 µg for ac- This article was written by Nicolas Sauvage, Sr. celerometers, an angle random walk (ARW) of 0.084°/√hr, and ve- Director Ecosystem, at InvenSense, a TDK Group locity random walk (VRW) of 0.016 m/s/√hr. It is also important to Company, San Jose, CA. For more information, have very small misalignment and mounting errors — less than 0.05° contact Nicolas Sauvage at nicolas.sauvage@ for both. invensense.com. Home Microphones Microphones are increasingly de ployed in home automation. For example, smart speakers have multiple microphones — the Amazon Echo has seven. You can easily imagine a future where a family has more than 100 microphones inside their home. These would have to be high performance, with a signal-to-noise-ratio (SNR) of more than 70 dB, while having an acoustic overload point (AOP) of more than 120 dB. One device that meets these specs is the InvenSense ICS- 40730 microphone, which has a 74 dB SNR and 123 dB AOP. This allows the microphone to listen to everything happening near the smart speaker even in the presence of loud noises, like a door closing too hard, or a TV playing an action movie too close to the speaker. Autonomous Vehicles Range-finding or time-of-flight (ToF) sensors with improved performance are starting to ad- dress the requirements of machines that move, such as self-driving cars, service robots, and in- dustrial monitoring drones. For them to be able to “see” their surroundings precisely and avoid obstacles, they need very precise sensors. For example, ultrasonic-based sensors are now able to measure distances up to five meters very precisely. However, different sensor parameters are im - portant for different applications. For example, drones care more about bias, time, and tem- perature stability, while house-cleaning robots care mostly about bias stability and noise. Access Control Improved ultrasonic-based sensors can also enhance access control systems. For example, they enable fingerprint sensors that can work well even under metal or plastic, allowing for operation in chal- Fig.4 Fingerprint access.