Hardy J. Pottinger

Lessons learned about wireless technologies for data acquistion

In recent years the electronics for developing sensor networks have become compact and cheaper. This has led to an interest in creating communities of distributed sensors that can collect and share data over a large area without being physically connected by wires. The Intelligent Systems Center at the University of Missouri-Rolla (UMR) has for several years been using commercial off-the-shelf (COTS) hardware and custom software to develop a system of stationary sensing nodes capable of pre processing their data locally and sharing processed data to produce global details. This distributed sensing and processing array is targeted for use in monitoring a wide variety of infrastructures. It has been laboratory tested for use in civil, automotive, and airframe monitoring. This paper is an overview of the technologies investigated and the level of functionality obtained from each hardware/sensor/target set. The current system consists of a web server, a central cluster and a collection of satellite clusters. The central cluster is a PC104 X 86 based computer with the satellite clusters being 8051 based single board computers. The satellite clusters are of the order 6 inch X 5 inch X 2 inch in size. There is an effort under way to place a short-range radio with a processor and a PZT sensor into a 2 inch X 1.5 inch X.5 inch package. Exercises have been carried out to demonstrate the ability of the central clusters to remotely control the satellite clusters and the web servers ability to control the central cluster. Further work is under way to integrate the entire system into a web server attached to the Internet and to a long distance communication device, currently employed is a cellular modem into the monitoring array. The web server communicates over standard phone lines to the central cluster, which is equipped with a cellular modem. The central cluster communicates with the satellite clusters using short-range wireless equipment. Proxim rangelan, Erickson Bluetooth, and Linx Technologies RF modules have all been tested as short-range wireless communication solutions. We have demonstrated a system that consists of a structure with an array of smart sensors, preprocess and collect data, and post this data on a web server for global inspection and manipulation. This will enable data sharing and collaborative data analysis to extend the knowledge of structural health monitoring.

Web-controlled Wireless Network Sensors for structural health monitoring

Wireless network sensors are being implemented for applications in transportation, manufacturing, security, and structural health monitoring. This paper describes an approach for data acquisition for damage detection in structures. The proposed Web-Controlled Wireless Network Sensors (WCWNS) is the integration of wireless network sensors and a web interface that allows easy remote access and operation from user-friendly HTML screens. The WCWNS is highly flexible in terms of functions and applications. Algorithms and tools for data analysis can be directly installed on and executed from the web server. This means WCWNS will have unlimited capabilities in performing data analysis. Data can be analyzed for damage detection either on site distributed amongst the intelligent sensors or off site either in the web server or at an end users location after downloading from the web server. This feature allows for a variety of health monitoring algorithms to be investigated by researchers of all backgrounds and abilities. In addition, both short-range and long-range communications devices handle data exchange and communications in WCWNS. The system can be setup to operate efficiently in any topological arrangement. Short-range communications devices facilitate fast and low-power local data transfer, while long-range communications devices support high quality long-distance data exchange. The proposed system is demonstrated on an experimental setup.

Microsensors for health monitoring of smart structures

Health monitoring of structural systems has gained a lot of interest in recent times. In this paper, we consider the wireless data acquisition for health monitoring of smart structures. Some of the work done towards development of micro sensors for wireless health monitoring of smart structures is presented. The concept of smart sensors is demonstrated with the help of commercially available micro controller and wireless Rx/Tx modules. Application of these smart sensors in health monitoring is also demonstrated on a laboratory set up. A subspace system identification method known as N4SID is used for getting the state space matrices of the nominal and the damaged systems. The concepts are demonstrated on simple test article. Finally, the future goals in the development of micro sensors are given.

Design and implementation of digital controllers for smart structures using field-programmable gate arrays

Implementation issues represent an unfamiliar challenge to most control engineers, and many techniques for controller design ignore these issues outright. Consequently, the design of controllers for smart structural systems usually proceeds without regard for their eventual implementation, thus resulting either in serious performance degradation or in hardware requirements that squander power, complicate integration, and drive up cost. The level of integration assumed by the Smart Patch further exacerbates these difficulties, and any design inefficiency may render the realization of a single-package sensor-controller-actuator system infeasible. The goal of this research is to automate the controller implementation process and to relieve the design engineer of implementation concerns like quantization, computational efficiency, and device selection. We specifically target Field Programmable Gate Arrays (FPGAs) as our hardware platform because these devices are highly flexible, power efficient, and reprogrammable. The current study develops an automated implementation sequence that minimizes hardware requirements while maintaining controller performance. Beginning with a state space representation of the controller, the sequence automatically generates a configuration bitstream for a suitable FPGA implementation. MATLAB functions optimize and simulate the control algorithm before translating it into the VHSIC hardware description language. These functions improve power efficiency and simplify integration in the final implementation by performing a linear transformation that renders the controller computationally friendly. The transformation favors sparse matrices in order to reduce multiply operations and the hardware necessary to support them; simultaneously, the remaining matrix elements take on values that minimize limit cycles and parameter sensitivity. The proposed controller design methodology is implemented on a simple cantilever beam test structure using FPGA hardware. The experimental closed loop response is compared with that of an automated FPGA controller implementation. Finally, we explore the integration of FPGA based controllers into a multi-chip module, which we believe represents the next step towards the realization of the Smart Patch.

Computer-Aided Testing of Electrical Machines: Software Development

Computer-aided test stations have been developed for research, experimentation, and testing of electric motors and generators. Data acquisition and control of the machines and drives are provided through a computer and its interfaces. Machines are connected to the computer through transducers for data acquisition, and power electronic drives for machine control. General software was written to enable the monitoring of all transducers continuously on the CRT screen while giving the user manual control of the machines and drives. Specialized software was written for automatic control of the induction, dc, and synchronous machines for specific experiments on each type of machine.

Distributed computing and sensing for structural health monitoring systems

Structural health monitoring involves automated evaluation of the condition of the structural system based on measurements acquired from the structure during natural or controlled excitation. The data acquisition and the ensuring computations involved in the health monitoring process can quickly become prohibitively expensive with the increase in size of the structure under investigation. In this paper, we propose a distributed sensing and computation architecture for health monitoring of large structures. This architecture involves a central processing unit that communicates with several data communication and processing clusters paced on the structure by wireless means. With this architecture the computation and acquisition requirements on the central processing unit can be reduced. Two different hardware implementation of this architecture one involving RF communication links and the other utilizing commercial wireless cellular phone network are developed. A simple health monitoring experiment that uses neural network based pattern classification is carried out to show effectiveness of the architecture.

An FPGA Based Reconfigurable Coprocessor Board Utilizing a Mathematics of Arrays

Work in progress at the University of Missouri-Rolla on hardware assists for high performance computing is presented. This research consists of a novel field programmable gate array (FPGA) based reconfigurable coprocessor board (the Chameleon Coprocessor) being used to evaluate hardware architectures for speedup of array computation algorithms. These algorithms are developed using a Mathematics of Arrays (MOA). They provide a means to generate addresses for data transfers that require less data movement than more traditional algorithms. In this manner, the address generation algorithms are acting as an intelligent data prefetching mechanism or special purpose cache controller. Software implementations have been used to provide speedups on the order of 100% over classical methods to the solution of heat transfer equations on a uniprocessor. We extend these methods to application designs for the Chameleon Coprocessor.

Hardware assists for high performance computing using a mathematics of arrays

Work in progress at the University of Missouri-Rolla on hardware assists for high performance computing is presented. This research consists of a novel field programmable gate array (FPGA) based reconfigurable coprocessor board (the Chameleon Coprocessor) being used to evaluate hardware architectures for speedup of array computation algorithms. These algorithms are developed using a Mathematics of Arrays (MOA). They provide a means to generate addresses for data transfers that require less data movement than more traditional algorithms. In this manner, the address generation algorithms are acting as an intelligent data prefetching mechanism or special purpose cache controller. Software implementations have been used to provide speedups on the order of 100% over classical methods to the solution of heat transfer equations on a uniprocessor. We extend these methods to application designs for the Chameleon Coprocessor.

Design and implementation of digital controllers for smart structures using field programmable gate arrays

Implementation issues represent an unfamiliar challenge to most control engineers, and many techniques for controller design ignore these issues outright. Consequently, the design of controllers for smart structural systems usually proceeds without regard for their eventual implementation, thus resulting either in serious performance degradation or in hardware requirements that squander power, complicate integration, and drive up cost. The level of integration assumed by the smart patch further exacerbates these difficulties, and any design inefficiency may render the realization of a single-package sensor - controller - actuator system infeasible. The goal of this research is to automate the controller implementation process and to relieve the design engineer of implementation concerns like quantization, computational efficiency, and device selection. Field programmable gate arrays (FPGA) are specifically targeted as a hardware platform because these devices are highly flexible, power efficient, and reprogrammable. The current study develops an automated implementation sequence that minimizes hardware requirements while maintaining controller performance. Beginning with a state space representation of the controller, the sequence automatically generates a configuration bitstream for a suitable FPGA implementation. MATLAB functions optimize and simulate the control algorithm before translating it into the VHSIC hardware description language (VHDL). These functions improve power efficiency and simplify integration in the final implementation by performing a linear transformation that renders the controller computationally friendly. The transformation favors sparse matrices in order to reduce multiply operations and the hardware necessary to support them; simultaneously, the remaining matrix elements take on values that minimize limit cycles and parameter sensitivity. The proposed controller design methodology is implemented on a simple cantilever beam test structure using FPGA hardware. The experimental closed loop response is gathered for an automated FPGA controller implementation. Finally, the integration of FPGA based controllers into a multi-chip module (MCM) is explored, which represents the next step towards the realization of the smart patch.

Distributed arithmetic implementation of multivariable controllers for smart structural systems

Smart structural systems require the electronic control systems which are integrated into the structures to be small, light weight and power-efficient. The field programmable gate array (FPGA) is a good platform to implement such controllers. In our previous work, FPGA-based digital controllers were built and tested on a simple structural system. In order to implement multivariable controllers, the hardware resources for FPGA-based architecture need to be further reduced. Distributed arithmetic (DA) has long been proven to be a very efficient means to mechanize computations that are dominated by inner products involving constant multiplicand. The computational requirements of the smart structural controllers match this type very well. In this paper various DA structure controllers are designed and results are compared with multiply-and-accumulate structure controllers. Single- and multi-variable controllers are implemented and tested on a cantilevered beam.