More Like this

1. Vibration-Theoretic Approach to Vulnerability Analysis of Nonlinear Vehicle Platoons

   https://doi.org/10.1109/TITS.2023.3278574  

   Wang, Pengcheng; Wu, Xinkai; He, Xiaozheng (October 2023, IEEE Transactions on Intelligent Transportation Systems)

   This research explores the inherent vulnerability of nonlinear vehicle platoons characterized by the oscillatory behavior triggered by external perturbations. The perturbation exerted on the vehicle platoon is regarded as an external force on an object. Following the mechanical vibration analysis in mechanics, this research proposes a vibration-theoretic approach that advances our understanding of platoon vulnerability from two aspects. First, the proposed approach introduces damping intensity to characterize vehicular platoon vulnerability, which divides platoon oscillations into two types, i.e., underdamped and overdamped. The damping intensity measures the platoon’s recovery strength in responding to perturbations. Second, the proposed approach can obtain the resonance frequency of a nonlinear vehicle platoon, where resonance amplifies platoon oscillation magnitude when the external perturbation frequency equals the platoon’s damping oscillation frequency. The main contribution of this research lies in the analytical derivation of the closed-form formulas of damping intensity and resonance frequency. In particular, the proposed approach formulates platoon dynamics under perturbation as a second-order non-homogeneous ordinary differential equation, enabling rigorous derivations and analyses for platoons with complicated nonlinear car-following behaviors. Through simulations built on real-world data, this paper demonstrates that an overdamped vehicle platoon is more robust against perturbations, and an underdamped platoon can be destabilized easily by exerting a perturbation at the platoon’s resonance frequency. The theoretical derivations and simulation results shed light on the design of reliable platooning control, either for human-driven or automated vehicles, to suppress the adverse effects of oscillations. 

   more » « less
2. TDMR Detection System with Local Area Influence Probabilistic a Priori Detector

   https://doi.org/10.1109/ICC.2019.8761903  

   Shen, Jinlu; Sun, Xueliang; Sivakumar, Krishnamoorthy; Belzer, Benjamin J.; Chan, Kheong Sann; James, Ashish (July 2019, ICC 2019 - 2019 IEEE International Conference on Communications (ICC))

   We propose a three-track detection system for two dimensional magnetic recording (TDMR) in which a local area influence probabilistic (LAIP) detector works with a trellis-based Bahl-Cocke-Jelinek-Raviv (BCJR) detector to remove intersymbol interference (ISI) and intertrack interference (ITI) among coded data bits as well as media noise due to magnetic grain-bit interactions. Two minimum mean-squared error (MMSE) linear equalizers with different response targets are employed before the LAIP and BCJR detectors. The LAIP detector considers local grain-bit interactions and passes coded bit log-likelihood ratios (LLRs) to the channel decoder, whose output LLRs serve as a priori information to the BCJR detector, which is followed by a second channel decoding pass. Simulation results under 1-shot decoding on a grain-flipping-probability (GFP) media model show that the proposed LAIP/BCJR detection system achieves density gains of 10.16% for center-track detection and 3.13% for three-track detection compared to a standard BCJR/1D-PDNP. The proposed system's BCJR detector bit error rates (BERs) are lower than those of a recently proposed two-track BCJR/2D-PDNP system by factors of (0.55, 0.08) for tracks 1 and 2 respectively. 

   more » « less
3. Broadband quantum enhancement of the LIGO detectors with frequency-dependent squeezing

   Ganapathy, D.; Jia, W.; Nakano, M.; Xu, V.; Dwyer, S.E.; Mullavey, A.; McCuller, L. (October 2023, Physical review X)

   Quantum noise imposes a fundamental limitation on the sensitivity of interferometric gravitational-wave detectors like LIGO, manifesting as shot noise and quantum radiation pressure noise. Here we present the first realization of frequency-dependent squeezing in full-scale gravitational-wave detectors, resulting in the reduction of both shot noise and quantum radiation pressure noise, with broadband detector enhancement from tens of Hz to several kHz. In the LIGO Hanford detector, squeezing reduced the detector noise amplitude by a factor of 1.6 (4.0 dB) near 1 kHz, while in the Livingston detector, the noise reduction was a factor of 1.9 (5.8dB). These improvements directly impact LIGO’s scientific output for high-frequency sources (e.g., binary neutron star post-merger physics). The improved low-frequency sensitivity, which boosted the detector range by 15–18 % with respect to no squeezing, corresponds to an increase in astrophysical detection rate of up to 65%. Frequency-dependent squeezing was enabled by the addition of a 300-meter long filter cavity to each detector as part of the LIGO A+ upgrade. 

   more » « less
4. Extraction of Bridge Fundamental Frequencies Utilizing a Smartphone MEMS Accelerometer

   https://doi.org/10.3390/s19143143  

   Elhattab, Ahmed; Uddin, Nasim; OBrien, Eugene (July 2019, Sensors)

   Smartphone MEMS (Micro Electrical Mechanical System) accelerometers have relatively low sensitivity and high output noise density. Therefore, it cannot be directly used to track feeble vibrations such as structural vibrations. This article proposes an effective increase in the sensitivity of the smartphone accelerometer utilizing the stochastic resonance (SR) phenomenon. SR is an approach where, counter-intuitively, feeble signals are amplified rather than overwhelmed by the addition of noise. This study introduces the 2D-frequency independent underdamped pinning stochastic resonance (2D-FI-UPSR) technique, which is a customized SR filter that enables identifying the frequencies of weak signals. To validate the feasibility of the proposed SR filter, an iPhone device is used to collect bridge acceleration data during normal traffic operation and the proposed 2D-FI-UPSR filter is used to process these data. The first four fundamental bridge frequencies are successfully identified from the iPhone data. In parallel to the iPhone, a highly sensitive wireless sensing network consists of 15 accelerometers (Silicon Designs accelerometers SDI-2012) is installed to validate the accuracy of the extracted frequencies. The measurement fidelity of the iPhone device is shown to be consistent with the wireless sensing network data with approximately 1% error in the first three bridge frequencies and 3% error in the fourth frequency. 

   more » « less
5. Turbo-Connected Neural Network Media Noise Cancellation Strategy for Asynchronous Multitrack Detection

   https://doi.org/10.1109/TMRC59626.2023.10264010  

   Banan_Sadeghian, Elnaz (October 2023, 2023 IEEE 34th Magnetic Recording Conference (TMRC))

   Multitrack detection architectures provide throughput and areal density gains over the current industry’s standard of single-track detection architectures. One major challenge of multitrack architectures is the complexity of implementing conventional pattern-dependent media noise prediction (PDNP) strategy within the multitrack symbol detector. In this paper we propose a neural network media noise predictor with manageable complexity that iterates with our rotating target (ROTAR) symbol detector in the turbo equalization fashion to predict and cancel the media noise for multitrack detection of asynchronous tracks. We evaluate the proposed detection strategy on a realistic two-dimensional magnetic-recording channel, and find that the proposed solution can effectively mitigate the media noise and therefore can replace the prohibitively complex PDNP solution for multitrack detection. 

   more » « less