bands

Abstract In enhanced Loran (eLoran) receiving systems, reliable signal acquisition is a prerequisite for subsequent tracking, timing, and positioning, and significantly affects receiver sensitivity and the effective acquisition range for weak and distant transmitter signals. This paper proposes a high-sensitivity, interference-resilient acquisition method based on Band-Summed Short-Time Fourier Transform (BS-STFT). The method combines the time-domain pulse structure and frequency-domain energy concentration of eLoran signals to perform time-frequency energy accumulation within selected bands, thereby significantly enhancing the prominence and stability of acquisition peaks in weak signal and interference dominated environments. Simulations show that BS-STFT maintains over 80\% acquisition probability at an SNR of -24\,dB and achieves a mean probability of 43\% in the SNR range from -30\,dB to -25\,dB. It also shows robustness to in-band continuous wave interference (CWI) with an SIR as low as -15\,dB at an SNR of -20\,dB, and maintains stable acquisition performance under sky-ground wave coexistence. Field experiments using real eLoran signals from inland and offshore test sites validate the proposed method. BS-STFT successfully acquired all eLoran transmitters deployed in China at both test sites, where the minimum SNR and electric field strength were -22.46\,dB and 26.38\,dB\textmu V/m, respectively, and the signal dynamic range between the two sites reached 65.93\,dB. These results indicate that the BS-STFT significantly improves acquisition sensitivity and interference resistance, providing strong support for eLoran systems operating in complex environments.

matched text: “bands”

Cycloidal (RV-type) reducers are widely used in industrial robot joints due to their high torque density and low backlash, yet their multi-mesh transmission path produces structured, operating-point-dependent vibration components at the disc-mesh order and associated harmonics and sidebands. This paper presents a real-time, accelerometer-in-the-loop vibration suppression framework that reduces these components online while maintaining tracking performance within the bounds observed in our experiments and operating within predefined safety limits. A tri-axial accelerometer mounted on the reducer housing provides high-bandwidth vibration measurements from which order-synchronous, band-limited metrics are computed in streaming form. These metrics define both the optimization objective and vibration exposure constraints. The control architecture retains the vendor servo loops and adds a vibration-targeted layer combining a low-dimensional anti-resonance parameterization (adaptive notch shaping and narrowband feedforward cancellation aligned with the estimated mesh-order family) with a safety-certified contextual Bayesian optimization module that adapts the parameters as a function of operating context (speed, load proxy, and temperature proxy). A barrier-function-based safety filter runs at the servo rate to enforce constraint handling during operation; its effect is evaluated empirically through logged interventions and constraint statistics. Experimental evaluation on a cycloidal joint testbed across multiple speeds and load levels shows attenuation of the dominant mesh-order vibration component and its harmonics. Tracking accuracy and safety-related signals remained within preset limits during the tested operating conditions. The proposed approach provides a deployable pathway for online vibration minimization in cycloidal robot joints without requiring high-fidelity internal contact models, and its logged parameter trajectories and order-tracked metrics also offer a foundation for condition-aware adaptation over long-term operation.

matched text: “band”