Noise is a common problem in wearable electrocardiogram (ECG) monitoring systems because the presence of noise can corrupt the ECG waveform causing inaccurate signal interpretation. By comparison with electromagnetic interference and its minimization, the reduction of motion artifact is more difficult and challenging because its time-frequency characteristics are unpredictable. Based on the characteristics of motion artifacts, this work uses adaptive filtering, a specially designed ECG device, and an Impedance Pneumography (IP) data acquisition system to combat motion artifacts. The newly designed ECG-IP acquisition system maximizes signal correlation by measuring both ECG and IP signals simultaneously using the same pair of electrodes. Signal comparison investigations between ECG and IP signals under five different body motions were carried out, and the Pearson Correlation Coefficient |r| was higher than 0.6 in all cases, indicating a good correlation. To optimize the performance of adaptive motion artifact reduction, the IP signal was filtered to a 5 Hz low-pass filter and then fed into a Recursive Least Squares (RLS) adaptive filter as a reference input signal. The performance of the proposed motion artifact reduction method was evaluated subjectively and objectively, and the results proved that the method could suppress the motion artifacts and achieve minimal distortion to the denoised ECG signal.

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Aimed at solving the prominent issue of spacecraft high-frequency vibration suppression, this paper creatively puts forward a novel method based on the micro-gimbal moment of magnetically suspended flywheel with dynamic feedback and feedforward decoupling control. The dynamic model of the on-orbit magnetically suspended flywheel is established first and the decoupling control law of spacecraft as well as the micro-gimbal steering law of the magnetically suspended flywheel is designed. The disturbance compensator based on dynamic feedback–feedforward current is put forward to cancel the disturbance of spacecraft to the magnetically suspended flywheel. Then the nonlinear on-orbit magnetically suspended flywheel system is converted into a linear system without spacecraft coupling, and the state feedback decoupling controller is used to realize the high-precision micro-gimbal moment control of the magnetically suspended flywheel. The dynamic compensation filter is further developed to reduce the influence of unmodeled dynamics on decoupling performances, improving the rate of convergence of vibration suppression. The above three components constitute together the dynamic feedback and feedforward decoupling controller. The simulation results show the effectiveness and superiority of this method.

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