Lasse Eriksson

Bio: Lasse Eriksson is an academic researcher from Aalto University. The author has contributed to research in topics: Wireless sensor network & Wi-Fi array. The author has an hindex of 6, co-authored 14 publications receiving 256 citations.

A Synchronized Wireless Sensor Network for Experimental Modal Analysis in Structural Health Monitoring

Abstract: Structural health monitoring aims to provide an accurate diagnosis of the condition of civil infrastruc- tures during their life span using data acquired by sen- sors Wireless sensor networks represent a suitable mon- itoring technology to collect reliable information about the structure's condition, replacing visual inspections, and reducing installation and maintenance time and costs This article introduces a time synchronized and configurable wireless sensor network for structural health monitoring enabling a highly accurate identification of the modal properties of the monitored structure The wireless sensor nodes forming the network are equipped with a 3-axis digital accelerometer and a temperature and humidity sensor The implemented Medium Access Con- trol layer time synchronization protocol (μ-Sync) en- sures a highly accurate synchronicity among the samples collected by the nodes, the absolute error being constantly below 10 μs, also when high sampling frequency (up to 1 kHz) and extended sampling periods (up to 10 min- utes) are applied The experimental results obtained on a wooden model bridge, compared with those derived from acceleration signals acquired by high-quality wired sensors, show that the so synchronized wireless sensor nodes allow a precise identification of the natural fre- quencies of vibration of the monitored structure (1% maximum relative difference)

Structural Health Monitoring in Wireless Sensor Networks by the Embedded Goertzel Algorithm

Abstract: Structural health monitoring aims to provide an accurate diagnosis of the condition of civil infrastructures during their life-span by analyzing data collected by sensors. To this purpose, detection and localization of damages are fundamental tasks. This paper introduces a wireless sensor network for structural damage detection and localization in which the sensor nodes, in order to estimate the energies of specific frequency bands, process the acceleration data locally in real-time using the Goertzel algorithm. The nodes then share their results inside the network and exploit them to compute transmissibility functions, which can be exploited as damage indicators and for correctly localizing damages within the monitored structure. The use of the embedded Goertzel algorithm prevents the nodes from transmitting large volumes of acceleration data to the sink node for off-line analysis, reducing the latency and increasing the life time of the cyber-physical system by 80 % and 52 %, respectively. The tests performed on a truss structure confirm the capability of the distributed approach in correctly detecting and localizing structural damages.

Distributed RSSI processing for intrusion detection in indoor environments

Abstract: In the context of WSNs, the RSSI has been traditionally exploited for localization, distance estimation, and link quality assessment. Recent research has shown that variations of the signal strength in indoor environments where nodes have been deployed can reveal movements of persons. Moreover, the time-histories of the RSSI over multiple links allow reconstructing the paths followed by the persons inside the monitored area. This approach, though effective, requires the transmission of multiple entire RSSI time-histories to a sink where these signals are processed, increasing latency and power consumption. This work aims at applying distributed processing of the RSSI signals for intrusion detection. Through distributed processing, the nodes are able to detect and localize moving persons autonomously. The latency and power consumption of the proposed intrusion detection system is minimized by transmitting to the sink only alert notifications related to significant events. Moreover, an accurate time-synchronization allows the nodes to keep the radio off most of the time. The proposed system was able to detect the intrusion of a person walking inside the monitored area, and to correctly keep track of the path he had followed. Possible applications of such a system include surveillance of critical buildings, support to emergency workers in locating people e.g. during fires and earthquakes, and to police in hostage situations or terrorist attacks.

On the performance of the PIDPLUS controller in wireless control systems

Abstract: The PIDPLUS algorithm is one of the candidates to be used in wireless automation systems. The control performance of this algorithm under packet losses is investigated in the paper. First, the performance of PIDPLUS is evaluated with respect to packet loss rates for a general first-order plus time-delay process, a model widely used for controller tuning. This simulation study reveals how the performance is affected by packet losses in a wireless control system. Secondly, we will elaborate on the implementation of PIDPLUS and discuss its design, tuning and performance in wireless control systems in light of an unstable case process. The results suggest that PIDPLUS can well be used for wireless control, but better performance could be attained by further development of the controller tuning methodology.

Review of Cyber-Physical System in Healthcare

Abstract: Cyber-physical system (CPS) is an integration of physical processes with computation and communication. It has the ability to add more intelligence to social life. Wireless sensor networks (WSN) can be a vital part of CPS as strong sensing capability is one of the major driving factors for CPS applications. CPS is still considered to be a nascent technology, and there are many challenges yet to be addressed. A few CPS applications in healthcare have been proposed to date, and they lack the flexibility of technology integration, such as integration of computing resources with sensor networks. This paper presents a survey of CPS in healthcare applications that have been proposed to date by academia as well as industry. A comprehensive taxonomy is also provided that characterizes and classifies different components and methods that are required for the application of CPS in healthcare. The taxonomy not only highlights the similarities and differences of the state-of-the-art technologies utilized in CPS for healthcare from the perspective of WSN and Cloud Computing but also identifies the areas that require further research. It is expected that this taxonomy and its mapping to relevant systems will be highly useful for further development of CPS for healthcare.

Wireless MEMS-Based Accelerometer Sensor Boards for Structural Vibration Monitoring: A Review

Abstract: Monitoring and analysing the integrity of structures and machinery is important for economic, operational, and mission critical reasons. In recent years, there has been growing interest in performing structural health monitoring (SHM) by monitoring structural dynamic response via micro electro-mechanical system accelerometers. In addition, the possibility of embedding these devices within a wireless sensor network and allowing measured data to be wirelessly transmitted has contributed to the development of many new applications not possible just a few years ago. These sensors, for use in SHM applications, need to detect low-amplitude and low frequency vibrations, operations which are not always feasible with the conventional low-cost sensor boards. Since the late 1990s, several accelerometer board prototypes have been proposed for achieving accurate vibration monitoring. This paper presents a summary review of the systems developed in the ten years following 2006 with particular emphasis on the sensing characteristics, performances, and applications of the designed sensor boards for microvibration detection and analysis.