Abstract
Automatically dynamic measurement systems to measure object weights are used in logistics and food industry, etc. The systems are composed of belt conveyor and road cell, and is called checkweigher. Checkweighers have a problem that noises of error factor change according to speed of belt conveyor and installation surrounding. As a result, variable filters are better suited for checkweighers to reduce the noises after installation. In this paper, we propose a design method of quasi-equiripple variable linear-phase FIR (Finite Impulse Response) filters using iterative weighted least squares method in the frequency domain. The proposed variable filter has some piecewise high attenuations in the stopband, and can change multi-factor in the stopband characteristics and some notch frequencies using variable parameters. In the proposed variable filter, filter coefficients are approximated by polynomial using polynomial coefficients and variable parameters. The number of the polynomial coefficients increases when variable parameters are the plural number or polynomial orders are high. Therefore, we also propose a reduction method of the polynomial coefficients. The usefulness of the proposed design method is verified through the examples.
