To estimate the moisture in an entire arbitrarily shaped workpiece, an automatic system should continuously sense moisture at all points of the workpiece. This paper proposes a design method for a microwavebased moisture sensing system for granular materials in arbitrarily shaped containers based on scanning in a moisture sensing box. The size of the moisture sensing box is first determined as the maximum size of any granular material containers based on initial user requirements. The moisture sensing system physically consists of a pair of antennas for microwave transmission and reception and a pair of distance sensors scanning throughout the maximum scanning range of the moisture sensing box to find the attenuation and workpiece thickness at all points of the workpiece, and these sensed microwave attenuations and workpiece thickness measurements are then used to calculate the moisture at all points of the workpiece. The average moisture of all points is finally taken as the estimated moisture of the whole workpiece.To evaluate the performance of the proposed system, experiments have been performed with granular materials in containers of various shapes, and the estimation results show the proposed method of continuous moisture scanning of a workpiece can improve 7.77% approximately compared with the antenna array approach.

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