ENABLING DETECTION AND RANGING FOR THE INTERNET OF THINGS AND BEYOND
-This article was initially published in German magazine Elektronik Praxis, April 2015-
The IoT consists of things, objects, devices, or machines that are connected to the Internet over fixed and wireless networks; they are able to collect data and share it with other devices.
A key enabler for IoT is the development of next-generation sensors that provide a wealth of quality data from which to build new applications and capabilities. Their small footprint, low cost, low power consumption, high reliability and adaptability allows for easy integration into a variety of devices.
What Are Smart Sensors and How Important Are They?
To better understand the role of smart sensors in the IoT, let’s first define the smart sensor. What makes a smart sensor “smart” is its onboard signal/data-processing capabilities. According to one definition, a smart sensor2 “includes a microprocessor that conditions the signals before transmission to the control network. It filters out unwanted noise and compensates for errors before sending the data. Some sensors can be custom-programmed to produce alerts on their own when critical limits are reached.” They often integrate VLSI technology and MEMS devices to reduce cost and optimize integration.
With their core functions to collect valuable data, sensors are very closely linked to the IoT, which will be built around autonomous sensors with radio communication capabilities. As such, an IoT sensing device requires at least three elements – sensor(s), microcontrollers, and connectivity to the Internet, as shown in the figure below.
Figure 1. The Fundamental Components of the IoT-Enabled Smart Sensing Device
Hence, the IoT can collect large amounts of quality, sensor-based data anytime and from anywhere, and transmit it over a network in real time. This provides enhanced awareness of our immediate or remote environment, bringing forth opportunities for faster and better decision-making, as well as gains in efficiency and productivity.
Smart Detection and Ranging Sensors: Applications and Required Characteristics
An important sensing category for the IoT is remote sensing, which consists of acquiring information about an object without making physical contact with it; the object can be nearby or several hundred meters away.
Multiple technology options are available for remote sensing, and they can be divided into three broad functions:
- Presence or proximity detection – when just determining the absence or presence of an object is sufficient (e.g., security applications). This is the simplest form of remote sensing.
- Speed measurement – when the exact position of an object is not required, but accurate speed is (e.g., traffic monitoring applications).
- Detection and ranging (DAR) – when the position of an object relative to the sensor must be determined precisely and accurately (e.g. vehicle collision avoidance).
DAR is the most complex of the three. From the position information, presence and speed can be retrieved, so technologies capable of DAR apply to all remote sensing applications.
Figure 2. LeddarCore, a family of integrated circuits (ICs) providing Leddar technology, enables the development of high-performance optical time-of-flight sensors
A wide variety of applications, in numerous fields, currently leverage smart DAR sensors to improve processes, consumer products, safety, and energy consumption.
Smart vehicles make transport and commutes safer with automotive driver assistance and collision avoidance systems. Smart homes and buildings improve our quality of life with applications like perimeter control, lighting management, and smart appliances.
Manufacturing and industry is made smarter by improving safety and efficiency through collision avoidance, perimeter control, security and surveillance, and level sensing or bulk measurement applications.
Smart cities use DAR sensors to take on growth and sustainability challenges with intelligent transportation systems, traffic supervision and flow control, parking management, smart lighting, etc.
No matter how much they differ, such applications share common requirements to meet the demands of anticipated mass deployments in challenging environments: reliability, accuracy, robustness, cost-effectiveness, adaptability, a small form factor, and minimal power and bandwidth consumption.
Smart DAR: Main Technologies
Now, let’s review some of the main DAR technologies and how they compare to each other. The first step is to distinguish between passive and active approaches.
Although it is possible to obtain distance information with passive technologies (e.g., stereo triangulation of camera images), active technologies are more common. These involve sending a pulse towards an object, collecting the echo signal, and analyzing it to determine the position of one or several items located in the sensor’s field of view. Since energy is intentionally emitted towards the initial object, they are considered “active”.
While some active technologies rely on the geometric location of the return echo to infer position information, others rely on the time characteristic of the return echo. These are generally known as time-of-flight measurement technologies. Although the implementation differs, time-of-flight measurements can be accomplished with radio waves (RADAR), sound/ultrasonic waves (SONAR) or light waves (LIDAR and LEDDAR®).
The table below provides a brief comparison of different remote sensing technologies.
Table 1: Summary Comparison of Active Time-of-Flight DAR Technologies
|RADAR||Radio waves||Short to
Leddar Technology: Highly Efficient DAR that Meets IoT Requirements
Each of the above technologies presents strengths and weaknesses, so it is important to determine which is most suitable for a specific application. The latest technology is called Leddar, a highly efficient sensing approach that is perfectly suited to the requirements of IoT applications.
Using LEDs or other light sources, Leddar advanced light processing is based on direct time-of-flight measurements. However, a fundamental differentiator of Leddar is that, rather than working directly with the analog signal, it starts by sampling the received echo for the complete detection range of its sensor. Through patented methods, Leddar iteratively expands the sampling rate, resolution, and signal-to-noise ratio of this sampled signal, producing a higher range-to-power ratio. Finally, it analyzes the resulting discrete-time signal and recovers the distance for every object. Implemented in standard submicron CMOS processes, Leddar becomes the LeddarCore, an ultra-low-power sensor integrated circuit (IC) that will maximize the performance of any optical time-of-flight sensor.
Figure 3. Leddar optical time-of-flight signal processing
Some of the advantages of Leddar are its high sensitivity, immunity to noise and powerful data processing capabilities. Leddar can also extract the distance for every object found in the field of view. Its unique ability to leverage a diffuse light beam (such as the one produced by LEDs) allows it to cover a wide area at once. The technology applies to sensors built with either a single detection element to perform a dedicated measurement, or with multi-element arrays, which could be used to build 2D or 3D sensors with fast, parallel measurement and no moving parts, making the technology both highly versatile and robust.
The LeddarCore IC family provides three important benefits when developing DAR applications: a higher range-to-power ratio, the ability to detect targets in low visibility, and the ability to resolve multiple targets at once.
With their high efficiency and simple, flexible design, Leddar sensors can be easily integrated into a small footprint at a reasonable price while delivering consistent performance and reliability. Together, this makes Leddar ideally suited to ultra-high-volume deployments, fostering new possibilities for IoT applications.
The IoT will soon interconnect all types of devices across numerous industries. With its expected growth, ubiquity and potential to reshape our daily lives, many anticipate that this trend will also lead to an explosion of the sensors market. It is projected that a trillion sensors will be deployed yearly within the next decade3, and that up to 45 trillion sensors will be networked in 20 years3.
Rapid advancements in sensing are only reinforcing this movement. Smart sensors may represent just a small part of the IoT, but they will definitely play a vital role in its deployment and represent a key enabler for many new applications.
Author: Stéphane Duquet, Director, Strategic Marketing, Leddartech
3 Dr. Janusz Bryzek, Introduction to TSensors and TSensor Systems, Stanford University, October 2013: https://www.tsensorssummit.org/Resources/TSensors%20Summit%20Abstracts.pdf