Smart Sensor Module

An assembly that contains a sensor, sensor-signal-conditioning circuitry, a sensor-readout analog-to-digital converter (ADC), data-storage circuitry, and a microprocessor that runs special-purpose software and communicates with one or more external computer(s) has been developed as a prototype of smart sensor modules for monitoring the integrity and functionality (the health ) of engineering systems. Although these modules are now being designed specifically for use on rocket-engine test stands, it is anticipated that they could also readily be designed to be incorporated into health-monitoring subsystems of such diverse engineering systems as spacecraft, aircraft, land vehicles, bridges, buildings, power plants, oilrigs, and defense installations. The figure is a simplified block diagram of the smart sensor module. The analog sensor readout signal is processed by the ADC, the digital output of which is fed to the microprocessor. By means of a standard RS-232 cable, the microprocessor is connected to a local personal computer (PC), from which software is downloaded into a randomaccess memory in the microprocessor. The local PC is also used to debug the software. Once the software is running, the local PC is disconnected and the module is controlled by, and all output data from the module are collected by, a remote PC via an Ethernet bus. Several smart sensor modules like this one could be connected to the same Ethernet bus and controlled by the single remote PC. The software running in the microprocessor includes driver programs for operation of the sensor, programs that implement self-assessment algorithms, programs that implement protocols for communication with the external computer( s), and programs that implement evolutionary methodologies to enable the module to improve its performance over time. The design of the module and of the health-monitoring system of which it is a part reflects the understanding that the main purpose of a health-monitoring system is to detect damage and, therefore, the health-monitoring system must be able to function effectively in the presence of damage and should be capable of distinguishing between damage to itself and damage to the system being monitored. A major benefit afforded by the self-assessment algorithms is that in the output of the module, the sensor data indicative of the health of the engineering system being monitored are coupled with a confidence factor that quantifies the degree of reliability of the data. Hence, the output includes information on the health of the sensor module itself in addition to information on the health of the engineering system being monitored

Signal Parameter Estimation Based on one-bit Quantized Data from Multiple Sensors

We consider the problem of signal parameter estimation using a collection of distributed sensors. Each sensor quantizes its data to one-bit information and sends it to a fusion processor for the estimation of the parameter. Estimation of a constant signal in additive noise is considered. Since the emphasis is for the case of a moderately large number of sensors, we consider in this study two cases of estimation with 8 sensors and 20 sensors. We formulate several estimators based on one-bit sensor data and evaluate their mean squared error performances through simulation studies. Two parametric noise densities are simulated to ascertain the efficacies of various estimators. Results from this study show that robust estimation of parameter is possible by using a moderately large number of one-bit quantized sensor data

Diabetic Patients Foot Care Using Smart Materials to Prevent Ulcerations/Amputations

A major cause of illness and disability in diabetic patients is complications affecting the lower limbs, particularly the feet where loss of feeling may result in ulcerations, and ultimately to partial or total amputation. Traditional remedies for this problem still remains in measuring the foot pressures and then designing a passive shoe insert that absorbs the high pressures. This process may then be repeated multiple times during the lifetime of the patient. This paper describes the conceptual design of an automatic system that monitors and controls the pressure levels in diabetic patients’ feet in real time. The scheme is based on the constant measurement of pressure levels and then actively changing the shape of the shoe insert so as to decrease the high pressure levels. The sensing and the actuation is done by the use of smart materials powered by a battery pack in the insert. The sensing is done by using piezoceramic patches while the actuation is done by use of electroactive polymer (EAP) actuators. All the circuitry is envisioned to be on a single VLSI chip embedded in the shoe insert, hence making the shoe insert completely autonomous. The greatest strength of the system is that it is an active real time system that will adapt to changes in the locations of high stress points, and, hence, is far superior to currently used passive shoe inserts and other forms of diabetic foot care

Physical Intelligent Sensors

This paper proposes the development of intelligent sensors as part of an integrated systems approach, i.e. one treats the sensors as a complete system with its own sensing hardware (the traditional sensor), A/D converters, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow them to get better with time. Under a project being undertaken at the NASA s Stennis Space Center, an integrated framework is being developed for the intelligent monitoring of smart elements. These smart elements can be sensors, actuators or other devices. The immediate application is the monitoring of the rocket test stands, but the technology should be generally applicable to the Integrated Systems Health Monitoring (ISHM) vision. This paper outlines progress made in the development of intelligent sensors by describing the work done till date on Physical Intelligent Sensors (PIS). The PIS discussed here consists of a thermocouple used to read temperature in an analog form which is then converted into digital values. A microprocessor collects the sensor readings and runs numerous embedded event detection routines on the collected data and if any event is detected, it is reported, stored and sent to a remote system through an Ethernet connection. Hence the output of the PIS is data coupled with confidence factor in the reliability of the data which leads to information on the health of the sensor at all times. All protocols are consistent with IEEE 1451.X standards. This work lays the foundation for the next generation of smart devices that have embedded intelligence for distributed decision making capabilities

A Genetic Algorithm Approach for Model Reference Adaptive Control of Ionic Polymer Metal Composites

Electroactive polymers undergo physical deformation to external voltage stimuli. These electrically activated polymers possess extraordinary features making them capable as lightweight sensors and actuators in manifold applications. The characteristics of applied voltage and environmental conditions, especially the moisture content surrounding the polymer, have a combined influence on the dynamical behavior of these polymers. In order to characterize these polymers under varying environmental conditions, this paper discusses the experimental procedure and modeling techniques used to derive a representative model. Ionic polymer metal composite polymers are used for this humidity relative electrodynamical study. Insight on the numerous applications of electroactive polymers as actuators and the built model enabled a controller is designed for a typical tracking problem. The control architecture includes a model reference adaptive scheme along with pole-placement control strategies to achieve the goal of tracking. A genetic algorithm approach is implemented to carryout an optimized control action. Tracking control of ionic polymer metal composites as actuator resembling that of a real-world scenario is simulated and reveals promising results

The Integrated Systems Engineering Laboratory- An Innovative Approach to Vertical Integration using Modern Instrumentation

The current paradigm in engineering course instruction builds on a lecture prerequisite structure but ignores the need for a laboratory prerequisite structure. Educational quality is therefore diminished as instructors optimize specific laboratories but fail to optimize the overall program laboratory experience. This paper presents a learning environment based on modern instrumentation that forces students to use not only concepts and skills acquired from the lecture, but also actual data and models acquired from lower division laboratories, in upper division laboratories. The vertical integration occurs because students must utilize their previous laboratory work as a reference and/or building blocks as they study the different facets of the same experimental set-ups in multiple engineering laboratories. The students learn to appreciate the integrated nature of modern systems since they get to use the same set-ups in multiple courses. Set-ups such as the inverted pendulum, mobile robot, a model airplane, a model train and a wind tunnel make heavy use of data-acquisition systems, programs written and developed in LabVIEW and MATLAB, and modern communication protocols such as RS485. The entire interface is through virtual instrumentation, and the lab is also being given the capability of remote access to the students. There are other indirect advantages of this approach in terms of financial economy and faculty professional development. This project has been funded by the National Science Foundation (NSF) and has resulted in the development of the Integrated Systems Engineering Laboratory (ISEL) that houses vertically integrated laboratory exercises for twelve courses from three different curricula

Real-time Measurement of Surface Deformation of Rotating Blades

This paper presents the results for the real-time measurement of surface deformation of rotating elements. A digital image correlation technique is used to estimate the surface displacements and strains. Speckle patterns are spray painted on the surface of interest and digital images taken before and during deformation caused by rotary motion. The digital image of the deformed blade is taken by freezing the speckled pattern with the help of a stroboscope. The technique provides several advantages over traditional methods in terms of obtaining whole-field deformation profiles, a non-invasive measurement scheme, and a simple and economical set-up. Results are presented for 1D uniform strain as well as 2D strain in a region next to a hole in a rubber specimen that is rotated at different speeds. The scheme presented in this paper can also be extended to measuring out-of-plane deformation by the use of an additional camera. The proposed technique can be used for measuring deformations in turbine blades, helicopter blades, or any other rotating elements

Local Material Properties Meausrement Using Ultrasonic C-Scan Techniques

Mechanical material properties of concrete specimen are evaluated locally and non-destructively using an ultrasonic C-scan system. The time of flight of the sound wave between front surface and back surface for test samples was measured. Local Young\u27s modulus at scanning point and average Young\u27s modulus of entire specimen are calculated. Testing techniques are developed by calibrating the transducer not only to compensate for the time delay but also to control the measurement of properties of interest, such as true density and local thickness. In order to obtain additional mechanical property, such as Poisson\u27s ratio, the transverse velocities of the wave through the specimen need to be measured. This non-destructive evaluation technique is an important alternative material property measurement method to replace the traditional testing methods that destroy specimens after testing. Advantage of high accuracy and time saving is also expected from this study

Physical Intelligent Sensors

This paper proposes the development of intelligent sensors as part of an integrated systems approach, i.e. one treats the sensors as a complete system with its own sensing hardware (the traditional sensor), A/D converters, processing and storage capabilities, software drivers, self-assessment algorithms, communication protocols and evolutionary methodologies that allow them to get better with time. Under a project being undertaken at the NASA s Stennis Space Center, an integrated framework is being developed for the intelligent monitoring of smart elements. These smart elements can be sensors, actuators or other devices. The immediate application is the monitoring of the rocket test stands, but the technology should be generally applicable to the Integrated Systems Health Monitoring (ISHM) vision. This paper outlines progress made in the development of intelligent sensors by describing the work done till date on Physical Intelligent Sensors (PIS). The PIS discussed here consists of a thermocouple used to read temperature in an analog form which is then converted into digital values. A microprocessor collects the sensor readings and runs numerous embedded event detection routines on the collected data and if any event is detected, it is reported, stored and sent to a remote system through an Ethernet connection. Hence the output of the PIS is data coupled with confidence factor in the reliability of the data which leads to information on the health of the sensor at all times. All protocols are consistent with IEEE 1451.X standards. This work lays the foundation for the next generation of smart devices that have embedded intelligence for distributed decision making capabilities