Huang-Chen Lee

Design of a Multifunctional Wireless Sensor for In-Situ Monitoring of Debris Flows

Debris flows carrying saturated solid materials in water flowing downslopes often cause severe damage to the lives and properties in their path. Close monitoring and early warning are imperative to save lives and reduce damage. Current debris-flow-monitoring systems usually install sensor equipment along the riverbanks and mountain slopes to detect debris flows and track their data. Unfortunately, most of this equipment indirectly collects data only from a distance. So far, there is no way to understand what is happening inside a debris flow and to collect its internal parameters, not to mention doing this in real time. To answer this challenge, this paper presents a novel multifunctional wireless sensor for monitoring debris flows. The core idea is to let these sensors drift with the debris flow, to collect flow information as they move along, and to wirelessly transmit the collected data to base stations in real time. The design of such a sensor needs to address many challenging issues, including cost, deployment efforts, long-term standby, and fast reaction. This paper addresses these issues and reports our evaluation results.

Using mobile wireless sensors for in-situ tracking of debris flows

Most debris flow monitoring systems deployed today use indirect means to track information regarding debris flows. In this work, we introduce a novel debris flow monitoring system for in-situ and direct tracking of debris flows in real-time. The core idea is to throw wireless sensors into the debris flows and collect flow information as they move along. We will describe the design of the wireless sensors and present some preliminary performance results.

A Reliable Wireless Sensor System for Monitoring Mechanical Wear-Out of Parts

A ball screw is a typical mechanical part that experiences wear-out and is widely used in computer numerical control machine tools to control the movement of processing targets and spindles. These types of parts need frequent checks so that they are replaced before excessive wear occurs. Until now, there was no simple way to measure directly the state of wear quantitatively. An indirect approach is logging the signals (vibration, temperature, and preload change) during the operation of mechanical parts. This information can be used to construct a wear model for estimating its remaining lifetime. For embedding sensors into mechanical devices, wireless sensors bring advantages in that they may be installed freely without constraints from data or power cables. However, wireless transmission is subjected to interference. To make wireless sensors that can be used practically within an industrial environment, we propose a wireless sensor system that: 1) emphasizes low-power and low cost in hardware design; 2) logs the signals during the operation of a mechanical part that could experience wear; and 3) guarantees that all the logged data can be wirelessly delivered to the data server. To our knowledge, this is the first wireless sensor system for measurement of mechanical operation signals that guarantees complete data delivery and correctness. We designed, implemented, and evaluated this system in real environments. This ensures that the design is practical. We envision that a miniature version of our design could be embedded in the ball screw shaft and gearbox reducer for logging signals to enable the building of a wear model to estimate the parts lifetime.

The Tube: A Rapidly Deployable Wireless Sensor Platform for Supervising Pollution of Emergency Work

Natural disasters, such as severe storms and earthquakes, often cause bridge collapses and road damage. To ensure public safety, governments must repair damage as soon as possible. The jackhammers, dozers, and piling machines used in emergency work always generate significant amounts of pollution, including noise and vibration, and thus, pollution levels should be monitored in an effort to protect the local environment. We propose the Tube, a wireless sensor network platform that can be easily and rapidly deployed for monitoring pollution at multiple emergency work locations. Users may install Tubes in multiple locations to monitor pollution simultaneously without having to worry about the issues affecting traditional wireless communication. We designed and implemented this platform to monitor pollution at an actual site of emergency work; the results verify this system meets all expected goals and can offer valuable information for local authorities to control pollution effectively on emergency work sites.

A Self-Powering Wireless Environment Monitoring System Using Soil Energy

This paper presents a self-powering wireless environment monitoring system using renewable and cost-efficient soil energy. The D-size (55.8 cm3) soil energy cell with carbon and zinc electrodes can produce ~60-100 μW, depending on the water contents and microbial reactions in the soil. The RC circuit model of a soil cell is proposed for understanding the electrical characteristics of the cell. The wireless sensing system, including temperature and air moisture sensors, a custom low-power capacitive sensor readout silicon chip, a microcontroller, and a Bluetooth low-energy transmitter, is demonstrated for long-term environmental monitoring solely by the fabricated D-size soil cell. The capacitive sensor readout chip is fabricated in a 0.18-μm CMOS process and only consumes 3 μW. The capacitance readout range is 160-200 pF. The total power consumption of the wireless temperature and air moisture monitoring system is ~20 μW and 1 mW in the sleep mode and the active wireless data communication operations, respectively. The new technology can enable remote field environment monitoring with less labor-intensive work and battery replacement.

Design and implementation of non-autonomous mobile wireless sensor for debris flow monitoring

This demo presents a mobile wireless sensor system for debris flow monitoring. The objective of this system is to realize long-term and effective debris flow surveillance using low cost wireless sensors. In the system, a set of robust wireless sensors are designed to deploy on riverbed and cooperatively observe the moving debris flows. Our mobile sensors are intended to be carried along by the debris flow. As the sensors move along, they are able to measure the internal parameters, such as vibration frequency, amplitude, moving direction and velocity, of the debris flow. By utilizing the proposed energy-saving mechanism on the WSN platform, the mobile sensors can continuously operate up to six months with merely two alkaline D cell batteries. The proposed system provides the abilities to collect high-fidelity data for civil engineering applications to analyze and determine the occurrence of debris flows, as well as estimate the damage.

Design and Evaluation of an Open-Source Wireless Mesh Networking Module for Environmental Monitoring

Wireless mesh networking extends the communication range among cooperating multiple low-power wireless radio transceivers and is useful for collecting data from sensors widely distributed over a large area. By integrating an off-the-shelf wireless design, such as the XBee module, development of sensor systems with mesh networking capability can be accelerated. This study introduces an open-source wireless mesh network (WMN) module, which integrates the functions of network discovery, automatic routing control, and transmission scheduling. In addition, this design is open source in order to promote the use of wireless mesh networking for environmental monitoring applications. Testing of the design and the proposed networking module is reported. The proposed wireless mesh networking module was evaluated and compared with XBee. The average package delivery ratio and standard deviation of the proposed WMN module and the XBee are 94.09%, 91.19%, 5.14%, and 10.25%, respectively, in a 20 node experiment. The proposed system was demonstrated to have the advantages of low-cost combined with high reliability and performance, and can aid scientists in implementing monitoring applications without the complications of complex wireless networking issues.

Towards a general wireless sensor network platform for outdoor environment monitoring

As wireless sensor networks (WSNs) have developed over the last decade, environmental scientists have widely adapted this new technology to monitor various phenomena in the natural environment, for example, debris flows, pollution, volcanoes, and so on. However, significant efforts are still needed to customize WSN design for certain special requirements. To remedy the redundancy of efforts to customize similar applications, we explore the possibility of designing a general WSN platform that can be used for various monitoring applications in an outdoor environment. We survey the existing WSN applications, summarize their common requirements, and conclude with the specification of a general WSN platform for these applications.

Development of a long-lived, real-time automatic weather station based on WSN

The scale of weather monitoring is limited by the cost of the automatic weather stations (AWS), which is mainly the cost of high precision instruments and long-distance wireless telecommunication equipments. We propose a wireless sensor network (WSN) based AWS, which takes advantage of the low-cost, real-time and infrastructure-free characteristics of WSN [1]. We can therefore extend the scale of weather monitoring without increasing the number of telecommunication equipments. This WSN-based AWS is able to cover a plane and gather multiple sets of weather measurements in real-time at a better data resolution.

Open-Source Wireless Sensor System for Long-Term Monitoring of Slope Movement

Power consumption is one of the major issues associated with deploying a wireless sensor to monitor natural environments in the real world. It is not practical to frequently replace the battery of a sensor that is located in a remote mountainous area. While considering to save valuable energy, the sensor must be able to detect a particular event in a timely manner and report data. To satisfy these requirements, in this paper, we present a wireless sensor system, termed SMARTCONE, which is designed to monitor the slope movement and minimize the standby power consumption, while remaining active to detect events. Multiple SMARTCONEs need to synchronously change their operation modes to collect the physical parameters and transmit raw vibration data simultaneously. SMARTCONE is consuming a power of only 0.05 mA at 3.6 V in standby mode, which is significantly less than that consumed by the previous design. As far as we know, SMARTCONE is an unprecedented instrument for the monitoring of slope movement; no other instruments can achieve such a low-energy consumption while being triggered by external vibration and managed remotely. These complicated issues are considered while designing the SMARTCONE, whose performance is then evaluated. In order to prevent redundant effort and to reduce the entry-level knowledge required by the users who wish to design a system, and to promote the use of this design for monitoring natural environments, we would like to open source the design of SMARTCONE for the public. It can be modified for use in other applications to satisfy their requirements without the need to build from scratch.