Periodic Noise Rejection of Checkweigher Based on Digital Multiple Notch Filter

Conveyor belt-type checkweigher is a widely used industrial system, whose periodic disturbances generated by the mechanical vibration parts (such as the operating motors, the gears, and the rollers) deteriorate the measurement accuracy of the weighing signal. The conventional way of suppressing these disturbances is using low-pass filters, which cannot meet the requirement if the conveyor belt is operating at a high speed (usually higher than 1.0 m/s). In this paper, the digital multiple IIR notch filter-based on a novel design method is proposed to remove these periodical noises. And the conventional low-pass filters and the wavelet signal denoising method are compared with the method proposed in this paper, the results show that the new method can achieve greater performance. Finally, an experimental platform of checkweigher is built and the mean errors and the standard deviations of the error about the tests in-field can meet the requirements of category XIII(1) in OIML R 51 with the conveyor belt running speed up to 2.0 m/s.