The current position of a work is sequentially updated in a conveyor coordinate system, and the path of a robot to follow the work is formed by transforming the position of the work from the conveyor coordinate system to a robot coordinate system. An elongated second cylinder is positioned on and is rotatable with respect to the first cylinder. The adsorption filter element comprises a granulated charcoal, a composite material having carbon particles combined with binder particles, or an immobilized bed of charcoal granules and EVA-coated fibers. The processing unit coupled to the signal analysis unit receives the analysis parameter, so as to obtain an impedance variation characteristic of the OUT.