Overall research plan of the PUB/CIEAC contains the following items:

1. Electromagnetic modelling of the FLUXSET sensor

(task 1.2, months: 1-12 = January 1998)

2. Development of the required electronics

(task 1.4, months: 6-14 = March 1998)

3. Enhancement of the measurement chain

(task 3.3, months: 8-20 = September 1998)

4. Application of the neural network for reconstruction

(task 4.6, months: 12-24 = January 1999)

5. Simulation of the measurement and comparison

(task 2.4, months: 14-30 = July 1999)

The general research objectives of the PUB/CIEAC are:

1. Development of a computer program able to simulate the output voltage of the sensor in an accurate manner.
2. Development of a simple model for the sensor and evaluation of the modelling errors.
3. Measurement performance analysis and the enhancement of the system. Numerical modelling and simulation of the measurement chain. Comparison with experimental results.
4. Implementation of the measurement and the reconstruction system (including use of neural networks).

The actions of the two tasks (1.2 and 1.4) planned for the first year are:

1. Analysis of the simplest sensor model (1D)

It was developed a theory based on the assumption that the magnetic field components orthogonal of the sensor's axis are neglected. The expression of the sensor's output voltage were obtained in the both cases: piece-wise linear magnetic characteristics and smooth magnetic characteristic as well as expressions for: sensor's sensitivity, measurement range and voltage pulse delay. Based on the results were draw recommendations for the electronic circuit specification and for B-H characteristic extraction procedure. The effect of the eddy currents in the sensor's ribbon shaped core was analysed and a SPICE model was established. Four computer programs (in the LINUX environment) were developed aiming:

• simulation of the FLUXSET sensor behaviour based on 1D model (MATLAB language);
• simulation of the circuit equivalent to the sensor (SPICE language);
• magnetic characteristic B(H) extraction from the i(t), u(t) oscilloscope images (C language and image-processing tools);
• evaluation of the measurement errors due to the eddy currents in the core (MATLAB language).

The 1D model prove to be very efficient in the understanding of the sensor's behaviour.

The results were presented to all partners at the kick-off meeting Budapest, March 20, 1997.



2. Analysis of a 2D-field model

For the modelling purposes, the core was considered as an equivalent cylinder with the same cross area. In this way the field problem became a 2.5D (axisymetric) one.

The solution of the problem was obtained by an original method (the linear PDE for the magnetic vector potential was solved by the separation variable method and the non-linear boundary conditions, which represents the core was solved by a suitable numerical method, of Ktzenelson type).

Based on this model, a computer program (in MATLAB language) was developed. It was used to simulate the sensor (to obtain its (i, H₀) characteristics) and to compute the relative sensitivities with design parameters.

The results were presented to the partners at the Reggio Calabria meeting, September 13, 1997.


3. Analysis of the 3D numerical model for the sensor

The most accurate models developed for the sensor are the 3D non-linear ones. Two techniques were used. The fist one is based on Finite Element Method (FEM) and the second on the Integral Equation Method (IEM). In the first case, has been used, in cooperation with the Bath team, the MEGA software package. For the second approach a dedicates code was successfully developed.

The results were presented to the partners at the Reggio Calabria meeting, September 13, 1997.


4. Development of a circuit model

Based on the field solutions obtained in the previous steps a dedicated SPICE model for the FLUXSET sensor was obtained. The approximation is based mainly on the least square technique. It allows to extract the circuit parameters from the field solution.

The results were presented to the partners at Reggio Calabria meeting, September 13, 1997.

An advanced and original technique based on 4 SID method was used to include the eddy current effects in the SPICE model

The results were presented to the partner at the Compumag Rio'97, November 3, 1997.


5. Electronic circuit specification

Based on the circuit and field analysis of the FLUXSET sensor the specification of an original VLSI circuit (named POLYFEM) was set-up. This circuit is dedicated to process the output signal of the sensor.

The last version of the specification is included in the section "Detailed Scientific Results".


6. Design of the VLSI circuit

The design started with the behaviour description of the electronic circuit, made in a hardware description language (VERILOG). The design was made in a hierarchical manner (top-drawn approach). In order to obtain a structural description high level synthesis was used. The obtained netlist allows to implement the design in FPGA technology.



7. Simulation of the VLSI circuit

Using the netlist generated by synthesis the system was simulated (by logic simulation) in order to check the complaining with the design specification.

The overall design procedure uses the methodology acquired by our lab as a member in EUROCHIP/EUROPRACTICE consortium (in the frame of ESPRIT program and a previous COPERNICUS project CP93 9093 - EUROEAST)..

The main problem encountered was related to the lack of financial resources for a such very complex and advanced research project. The quality of the research output is close linked with the financial resources allocated. The wages used in Romania are not enough attractive for the talented young people who prefer to go abroad or in the private sector.

The second problem is related to the difficulties to obtain a visa from EU member states Embassies in Bucharest.

Based on the 9 internal research reports and 2 MSc thesis which resulted from the work of the project in 1997, the following papers were presented at the international conferences:

1. D. Ioan, M. Rebican, G. Ciuprina, P. Leonard - 3D FEM Model of a FLUXSET Sensor- ENDE'97, Reggio Calabria, Italy, September 14-16, 1997;
2. D. Ioan, Fl. Hãnþilã, M. Rebican, G. Constantin - FLUXSET Sensor Analysis Based on Non-linear Magnetic Wire Model of the Core, ENDE'97, Reggio Calabria, Italy, September 14-16, 1997;
3. D. Ioan, M. Rebican, M. Iordache - Approximate SPICE Models of Non-linear Magnetic Circuits Based on Field Solution, ENDE'97, Reggio Calabria, Italy, September 14-16, 1997;
4. D. Ioan, I. Munteanu, C.G. Constantin - The best Approximation of the Field Effects in Electric Circuit Coupled Problems, COMPUMAG RIO'97, Rio de Janeiro, Brazil, 1997.

The papers are under peer reviewing process in order, to be published in a IOS Press book dedicated "Electromagnetic Nondistructive Evaluation" ed. A. Albanese (the first three) and in IEEE Transaction on Magnetics (the last one).

According to the research plan of the PUB research / CIEAC plan the following objectives and main actions are planned for the next year:

The most relevant scientific results are presented in the four published papers (see annex).

An important document is the final specification for the "Digital circuit attached to the FLUXSET sensor" (October 3, 1997). It is also annexed.

Other information regarding the results obtained in the frame of the MANODET project by PUB/CIEAC can be found in our dedicated Web page:

URL: http://www2.lmn.pub.ro/manodet