A survey on real time electrical capacitance tomography using VLSI architecture

Abstract

This paper presents a fixed-point reconfigurable parallel VLSI hardware architecture for realtime Electrical Capacitance Tomography (ECT). It is modular and consists of a front-end module which performs precise capacitance measurements in a time multiplexed manner using Capacitance to Digital Converter (CDC) technique. Another FPGA module performs the inverse steps of the tomography algorithm. A dual port built-in memory banks store the sensitivity matrix, the actual value of the capacitances, and the actual image. A two dimensional (2D) core multiprocessing elements (PE) engine intercommunicates with these memory banks via parallel buses. A Hardware-software codesign methodology was conducted using commercially available tools in order to concurrently tune the algorithms and hardware parameters. Hence, the hardware was designed down to the bit-level in order to reduce both the hardware cost and power consumption, while satisfying real-time constraint. Quantization errors were assessed against the image quality and bitlevel simulations demonstrate the correctness of the design. Further simulations indicate that the proposed architecture achieves a speed-up of up to three orders of magnitude over the software version when the reconstruction algorithm runs on 2.53 GHZ based Pentium processor or DSP Ti’s Delphino TMS320F32837 processor. More specifically, a throughput of 17.241 Kframes/sec for both the Linear-Back Projection (LBP) and modified Landweber algorithms and 8.475 Kframes/sec for the Landweber algorithm with 200 iterations could be achieved. This performance was achieved using an array of [2×2] × [2×2] processing units. This satisfies the real-time constraint of many industrial applications.