Showing papers on "Wireless sensor network published in 1996"

Low power systems for wireless microsensors

Abstract: Low power wireless sensor networks provide a new monitoring and control capability for civil and military applications in transportation, manufacturing, biomedical, environmental management, and safety and security systems. Wireless microsensor network nodes, operating at average and peak power levels constrained by compact power sources, offer a range of important challenges for low power methods. This paper reports advances in low power systems spanning network design, through power management, low power mixed signal circuits, and highly integrated RF network interfaces. Particular attention is focused on methods for low power RF receiver systems.

CDMA for wireless SAW sensor applications

Abstract: A well known spread spectrum technique is used to get the sensor information from an individually addressed SAW sensor. Coded ID tag type and BPSK type SAW sensors are picked out of a number of sensors by correlating the received signal with the known code of a particular sensor. The ID-tag type and BPSK-coded SAW sensor's function is observed as a scaling of time and shape respectively. The time scaling factor is equal to the mechanical extension of the substrate of a sensor due to temperature, etc. This scaling factor is evaluated by use of correlative signal processing techniques. The principal concept, mathematical simulations, numerical estimations and finally an overview of the implemented SAW sensor system are shown. Preliminary results for readout of OOK and BPSK coded passive remote SAW sensors using the wavelet transform processed within a SAW convolver are presented.

Requirements for wireless extensions of a FIP fieldbus

Abstract: We study wireless communications within the context of industrial applications. The question of interest is whether or not wireless connections can be used for accessing distant sensors and actuators through fieldbus. Another question of interest is whether the bandwidth of currently available wireless connections allow the access to distant sensors/actuators through a fieldbus protocol. The paper describes a repeater design for the extension of a FIP standard fieldbus.

A Distributed, Wireless MEMS Technology for Condition Based Maintenance

Abstract: : Distributed MEMS networks can revolutionize critical military, industrial, and civil surveillance, transportation, manufacturing, and environmental management systems. Low cost sensor network development, coupled with the high performance of compact computing systems can provide new monitoring and control capability. Embedded microsensors and microactuators may provide control for improved dynamical response of large structures, for reduced requirements on dimensional precision, and for health monitoring and failure prediction of airframes, powerplants, buildings, and other structures. The installation of wireline networks for sensors raises important questions for condition based maintenance (CBM) system cost. For example, the installation of sensor network cables may require major modification to capitol equipment and vehicle systems, particularly for rotating component diagnostics. Thus, the development of autonomous, low power, wireless microsensors offers an opportunity to provide CBM at low cost to a wide range of applications. This presentation will describe fully integrated, wireless MEMS devices implemented with new RF communication and MEMS integration methods.

A smart sensing microsystem with a capacitive sensor interface

Abstract: This paper describes a smart microsystem that utilizes a generic interface circuit capable of interfacing with a large variety of capacitive sensors. This wireless microsystem includes a microcontroller for signal processing, sensors that measure temperature, pressure, humidity, and acceleration, and a 315 MHz transmitter for data output. An interface chip handles communication between the microcontroller and the sensors over a standard sensor bus and provides readout circuitry for the capacitive transducers. This interface circuit is highly programmable, can interface with up to six external sensors, supports sensor self-test, and includes three programmable internal reference capacitors in the range of 0.2-12 pF and a temperature sensor. The chip dissipates less than 2.2 mW from a single 5 V supply and can resolve input capacitance variation better than 1 fF.

Wavelength division multiplexed optical point-sensor networks using injection laser diode sources

Abstract: Wavelength division multiplexing (WDM) offers an elegant solution to the problem of increasing sensor numbers on an optical point-sensor network. In this paper the provision of WDM optical point-sensor networks is examined by determining the optical power budgets required for their implementation. A substantial increase in the number of distributed optical point-senors is demonstrated when using injection laser diode sources in conjunction with two new power-efficient WDM sensor network topologies.

Medium access control for wireless extensions of ATM networks

Abstract: Wireless access to broadband communication networks is becoming an important issue. This paper discusses medium access aspects for a wireless extension of high-speed asynchronous transfer mode (ATM) networks. A centralized control scheme for a coordinated medium access is required in order to efficiently accommodate ATM traffic on wireless links. It turns out that the scheduler algorithm needed for the coordinated access strongly influences the cell delay which is most important for delay sensitive services. The performance of a first-come first-serve scheduler in terms of cell delay is analyzed for video-phone services. By modelling the cell stream of each terminal with an independent Bernoulli process the average queue length and cell delay can be evaluated in terms of the burstiness of the sources.

Decentralized processing for multitarget motion analysis

Abstract: Track estimation of targets from passive-sensor data is one of the typical and hard applications in both distributed artificial intelligence and distributed sensor networks. Multitarget motion analysis, where there is more than one target, is to associate targets and sensor data, and estimate target tracks based on that association. This is an NP-hard problem in general, and solved using stepwise relaxation. However, it is hard to obtain the optimal solution, or in other words, to locate the global optimum out of many local optima in the search space. This paper proposes a new approach to improve estimation, decentralized cooperative search using several processors. Simulation shows this approach achieves almost the same estimation as a stochastic relaxation based on simulated annealing, and much better performance.

Fault detection systems

Abstract: Publisher Summary This chapter presents the example of fault detection systems. An example is the optical sensor network system, which is characterized by the use of an optical-fiber network connecting optically the devices in the field with the central computer system. In this system, the detection operations themselves are performed directly by means of optical methods or the electric signals from the usual sensors are changed into optical signals in a sensor-interface processor. The other example is the group of new sensors for the detection of faults. These sensors are based on various optical principles. The technical fields required in the development of fault detection systems are divided into two groups: (1) the abnormality and its type and degree are derived from the signals from the usual sensors, which are not specially developed, and (2) on the other hand, the real difficulties arising in fault detection systems, in many cases, have been caused by the difficulties of access for the usual sensors because of physical hazards or narrow spaces, or by the inadequacies of the sensors themselves with respect to the detection of physical data from the faults. In the chapter, an optical-fiber network system and the optical apparatuses used in the network, which are useful for construction of intrinsically safe systems, and optical sensors developed specially for difficult inspection targets have been presented. The optical techniques may be useful for the further development of sensing systems in this field.

Optonet system: a 64 on/off fiber optic sensor network designed for industrial and military applications

Abstract: The OPTONET system monitors up to 64 ON/OFF fiber optic sensors. It is based on Optical Time Domain Reflectometry (OTDR). An optical pulse emitted by a pulsed laser diode is splitted between the sensors through an opticalstar network including delay lines to separate the pulses reflected back from the sensors. A dual wavelength emission boardis implemented to garantee line surveillance and optical path loss compensation, in order to minimize the error rate, andinformation discrepancy. These characteristics also combined with the well known advantages of fiber optic sensors makethis system attractive in military or harsh environment. Various reflective sensors can be connected to the OPTONETsystem ; we describe here sensors developped for a French Navy application. Keywords : OTDR, fiber optic sensor, multiplexing, Rayleigh backscattering, intensity referencing, liquid detection, temperature detection. 1. SYSTEM DESCRIPTION The system developped and described hereafter is dedicated to the monitoring of a French Navy system. The aim was to builda complete fiber optic sensor network demonstrator to evaluate the advantages and the viability of this new type of systemfor a specific Naval application. The overall system, includes ON/OFF sensors, such as limit switches, water detectionsensors, together with analog single point sensors. This paper will only focus on the ON/OFF sensor network.The principle of the system is based on OTDR 1,2,3,4,5 and derived from previous developments. The system has fouroptical outputs and incorporates two detectors and an optical star architecture network (Figure 1). The effort was focused tosecure the information. So a dual wavelength scheme was implemented to achieve optical path loss compensation andoptical line surveillance. In each sensor is incorporated a dichroic filter that is reflective at the chosen reference wavelength.The measurement wavelength pulse is transmitted to the transducer and reflected or not according to the sensor state. A linefailure is detected by the absence of the reflected pulse at the reference wavelength. Secondly the sensor state information is