Silviu Folea

A Low-Power Wireless Sensor for Online Ambient Monitoring

This paper presents the development of a compact battery-powered system that monitors the carbon dioxide level, temperature, relative humidity, absolute pressure, and intensity of light in indoor spaces, and that sends the measurement data using the existent wireless infrastructure based on the IEEE 802.11 b/g standards. The resulted devices characteristics and performance are comparable with the ones provided by recognized solutions, such as ZigBee-based sensor nodes. By combining Wi-Fi connectivity with ambient sensors, this solution can be used for the remote gathering and further processing of measurement data. Testing revealed that the system can operate continuously for up to three years on a single 3 V small battery.

Theoretical Analysis and Experimental Validation of a Simplified Fractional Order Controller for a Magnetic Levitation System

Fractional order (FO) controllers are among the emerging solutions for increasing closed-loop performance and robustness. However, they have been applied mostly to stable processes. When applied to unstable systems, the tuning technique uses the well-known frequency-domain procedures or complex genetic algorithms. This brief proposes a special type of an FO controller, as well as a novel tuning procedure, which is simple and does not involve any optimization routines. The controller parameters may be determined directly using overshoot requirements and the study of the stability of FO systems. The tuning procedure is given for the general case of a class of unstable systems with pole multiplicity. The advantage of the proposed FO controller consists in the simplicity of the tuning approach. The case study considered in this brief consists in a magnetic levitation system. The experimental results provided show that the designed controller can indeed stabilize the magnetic levitation system, as well as provide robustness to modeling uncertainties and supplementary loading conditions. For comparison purposes, a simple PID controller is also designed to point out the advantages of using the proposed FO controller.

Smart home automation system using Wi-Fi low power devices

Home automation is gaining popularity nowadays. A smart home automation system is based on ensuring security and making user life easier. It contains a large number of sensors which can control or monitor objects distributed in three-dimensional space. The sensors can be specialized in measuring temperature, humidity, pressure, light, noise, dust air, and so on. In this paper, a solution to transform a normal house in a smart house while reducing the energy consumption is proposed. This can be realized with the help of wireless sensor networks and of the LabVIEW™ graphical programming environment, which use the NI LabVIEW™ Statechart Module for collecting data from sensors.

Ultra-low power Wi-Fi tag for wireless sensing

G2 microsystems of Campbell, California, USA, released in 2007 the first ever ultra-low power Wi-Fi System on a Chip (SoC) named G2C501. This SoC includes a 32-bit CPU, crypto accelerator, real-time clock and a versatile sensor interface that can serve as a standalone host subsystem. The G2C501 goes beyond todaypsilas basic radio frequency identification (RFID) technology to offer intelligent tracking and sensor capabilities that leverage IEEE 802.11 (Wi-Fi) networks. Due to its support for multiple location technologies, small form factor and ultra-low power consumption, the G2 SoC can be integrated into Wi-Fi asset tags that lower cost of ownership and meet the needs of a variety of industries including consumer electronics, pharmaceuticals, chemical manufacturing, cold chain and more. G2 Microsystems offered companies from different industries participation into a beta program that granted early access to the silicon in 2007 with the idea of fine-tuning and testing the SoC firmware. One direction was to develop a device platform for ultra low-power Wi-Fi sensing which represents a deviation from G2psilas focus on asset location tracking. A battery powered, small size ultra low-power Wi-Fi wireless measurement node has been built for measurement of temperature, humidity, light, and vibration or motion. The node is able to read a sensor and send data to the network by using an IP-based application protocol such as UDP. This paper describes the wireless node hardware and firmware components, power consumption and power management, application software, and it also gives a performance analysis. The device being a sensor with IP capability was named the IP Sensor.

A Cyber-Physical System for Environmental Monitoring

This paper presents the development of a cyber-physical system that monitors the environmental conditions or the ambient conditions in indoor spaces at remote locations. The communication between the systems components is performed using the existent wireless infrastructure based on the IEEE 802.11 b/g standards. The resulted solution provides the possibility of logging measurements from locations all over the world and of visualizing and analyzing the gathered data from any device connected to the Internet. This work encompasses the complete solution, a cyber-physical system, starting from the physical level, consisting of sensors and the communication protocol, and reaching data management and storage at the cyber level. The experimental results show that the proposed system represents a viable and straightforward solution for environmental and ambient monitoring applications.

A cloud-based Cyber-Physical System for environmental monitoring

Cyber-Physical Systems (CPSs) represent a new generation of digital systems, where cyber entities and physical devices cooperate towards a set of common goals. The research presented in this paper aims to contribute to the development of CPSs by proposing an open architecture applicable in environmental monitoring, consisting of three layers. The paper provides a detailed description of each one of the CPSs main components. The bottom layer, composed of wireless sensor nodes, allows the acquisition of data and their transfer to the upper layers. The top and middle layers, composed of a measurements database, a knowledge base, a multi-agent society and web services, assure the proper operation of the CPS based on decision rules and complex data analyses. The proposed architecture provides a high degree of flexibility and scalability.

Wi-sensors: A low power Wi-Fi solution for temperature and humidity measurement

This paper presents a complete solution for temperature and humidity monitoring using low-power wireless devices, called Wi-Sensors. The Wi-Sensors use a RN-131C Wi-Fi chip as the core microcontroller and 4 configurable digital input/output lines to which temperature sensors can be attached. The digital 1-Wire and DHT22 protocols had been implemented in the embedded application running on the device. Therefore, for temperature and humidity measurements, any of the sensors operating with one of these two protocols can be used. The existing Wi-Fi 802.11 infrastructure can be used in order to send measurement data to remote destinations. The proposed solution also incorporates a data viewer and data processing application, which provides functionalities for alarming the users by email or by SMS in case previously configured limits are exceeded.

Tag4M, a Wi-Fi RFID Active Tag Optimized for Sensor Measurements

Tag4M is a Wi-Fi RFID active tag with the functionality of a multifunctional Input/Output measurement device. The tag offers a comb ination of Wi-Fi radio and measurement capabilities for sensors and actuators that generate output as voltage, current, or digital signal. Tag4M is very suitable for prototyping of wireless sensor measurements and also for teaching wireless measurement using the existing Wi-Fi infrastructure. In many applications cables need to be removed from measurement setups and replaced with wireless devices that are connected to sensors and send data wirelessly to the network and to computers. Wireless measurement devices that replace cabling need to be small and cheap and reliable in order to be a valid replacement for cabling. Mobile type measurement applications like monitoring of rotating machinery or moving objects also benefit from wireless measurement devices. Inside the class of wireless measurement devices there are those running on batteries. These devices are built around low or very low power microcontrollers, have the capability of going to sleep for long periods of time, and implement some kind of radio and associated communication protocol that are designed to save battery power. Wireless USB, ZigBee, Bluetooth and ultra low-power Wi-Fi are the most common radio platforms used in wireless measurement and communication. Basic performance benchmarks for comparison of these technologies, things like application domains, typical range, network connectivity, network topology and key attributes are available in the reference (Sidhu et al., 2007). Wireless USB devices, like the wireless mouse for example, are mostly used as computer peripherals. Bluetooth devices are more power hungry therefore this wireless technology is used in PDAs and computers that can be (re)charged overnight. The strength of Bluetooth lies in its ability to allow interoperability and replacement of cables. ZigBee and ultra low power Wi-Fi are the two wireless technologies best suited for sensor measurement. The one major difference between ZigBee and ultra-low power Wi-Fi is that ZigBee nodes use the ZigBee protocol and not any native Internet protocol like TCP/IP or UDP, and therefore ZigBee nodes need a dedicated Access Point that translates ZigBee into TCP/IP in order for the data to be sent over the network. ZigBee networks can support a larger number of devices and in most cases, longer range between devices than Bluetooth

Development and application of a PID auto-tuning method to a wastewater treatment process

This paper presents an application regarding a developed extension of the widely used relay-feedback PID auto-tuner. The proposed method consists of two steps: process identification and controller design. First, a non-iterative procedure is suggested for identification of one point on the process Nyquist curve. A second-order model (SOS) is obtained and then used for PID controller design based on the internal model principle (IMC). For the identification of the point on the Nyquist curve a relay in the feedback loop (as used in standard auto-tuning) which operates on the integral of the error is used. The method is illustrated on an application to a wastewater treatment process. In the considered process, the wastewater is treated in order to obtain an effluent having the substrate concentration within the standard limits. The performances of control algorithms are illustrated by simulation results. The influence of changing a design parameter in the desired closed loop behavior is shown.

Analysis of Three IoT-Based Wireless Sensors for Environmental Monitoring

The recent changes in climate have increased the importance of environmental monitoring, making it a topical and highly active research area. This field is based on remote sensing and on wireless sensor networks for gathering data about the environment. Recent advancements, such as the vision of the Internet of Things (IoT), the cloud computing model, and cyber-physical systems, provide support for the transmission and management of huge amounts of data regarding the trends observed in environmental parameters. In this context, the current work presents three different IoT-based wireless sensors for environmental and ambient monitoring: one employing User Datagram Protocol (UDP)-based Wi-Fi communication, one communicating through Wi-Fi and Hypertext Transfer Protocol (HTTP), and a third one using Bluetooth Smart. All of the presented systems provide the possibility of recording data at remote locations and of visualizing them from every device with an Internet connection, enabling the monitoring of geographically large areas. The development details of these systems are described, along with the major differences and similarities between them. The feasibility of the three developed systems for implementing monitoring applications, taking into account their energy autonomy, ease of use, solution complexity, and Internet connectivity facility, was analyzed, and revealed that they make good candidates for IoT-based solutions.