Sensor Time Delay Research Articles

Research on a Sound Source Localization Method for UAV Detection Based on Improved Empirical Mode Decomposition.

To address the challenge of accurately locating unmanned aerial vehicles (UAVs) in situations where radar tracking is not feasible and visual observation is difficult, this paper proposes an innovative acoustic source localization method based on improved Empirical Mode Decomposition (EMD) within an adaptive frequency window. In this study, the collected flight signals of UAVs undergo smoothing filtering. Additionally, Robust Empirical Mode Decomposition (REMD) is applied to decompose the signals into Intrinsic Mode Function (IMF) components for spectrum analysis. We introduce a sliding frequency window with adjustable bandwidth, which is automatically determined using a Grey Wolf Optimizer (GWO) with a sliding index. This window is used to lock and extract specific frequencies from the IMFs. Based on predefined criteria, the extracted IMF components are reconstructed, and trigger signal times are analyzed and recorded from these reconstructed IMFs. The time differences between sensor receptions are then calculated. Furthermore, this study introduces the Chan-Taylor localization algorithm based on weighted least squares. This advanced algorithm takes sensor time delay parameters as input and solves a set of nonlinear equations to determine the target's location. Simulations and real-world signal tests are used to validate the robustness and performance of the proposed method. The results indicate that the localization error remains below 5% within a 15 m × 15 m measurement area. This provides an efficient and real-time method for detecting the location of small UAVs.

Thermal behavior of a double cone synchronizer with carbon friction lining – verification and validation of 2D thermo-mechanical simulations by temperature measurements

Synchronizers are important machine elements in gearboxes used in cars and trucks. A continuous demand for higher power density in transmissions increases the load requirements on these components. Modern Carbon friction linings can significantly improve the performance of synchronizers, but the low thermal conductivity of these materials results in high friction surface temperatures that can both damage the friction lining and lubricant. Using double cone synchronizers can further increase the power density, but the thermal loads as well. Understanding the thermal behavior of a synchronizer is important in order to improve its performance. This paper presents a 2D thermo-mechanical FEM model to calculate the temperature distribution in a double cone synchronizer. Extensive temperature measurements verify and validate the model. Practical guidelines for measuring temperatures in synchronizers are provided. The simulated temperatures correlate well with the measurements. Several parameters that influence the maximum temperature are analyzed, such as load parameters, different simulation approaches, position of temperature sensors, sensor time delay, and the influence of material properties. Measurements in combination with simulations demonstrate that cooling during the engagements and the friction of sliding blocks influence the temperature increase during an engagement.

Extending the adaptive time gap car-following model to enhance local and string stability for adaptive cruise control systems

In this paper, we extend the nonlinear adaptive time gap car-following model to enhance the local and string stability for adaptive cruise control systems considering a time-lag in the lower level vehicle dynamics and a sensor time-delay. Both over-damped local and string stability analyses are performed mathematically and examined by simulation. The over-damped string stability criterion fulfills all the Lp stability norms, where Here we consider a time-lag operating in the lower level of the longitudinal control system’s architecture, a sensor time-delay, and heterogeneity in the vehicle dynamics of the platoon. The adaptive time gap model without these attributes is intrinsically stable. However, it turns out that the introduction of a lag, a delay, or heterogeneity in the lower vehicular level reduces the performance in terms of stability, yielding unsafe damped oscillating collective behaviors. Henceforth we extend the model to enhance the stability by transforming the model to a homogeneous structure, without changing the fundamental dynamics. The results show that the extended model satisfies over-damped criteria for both local and string stability, considering actuator time-lag, sensor time-delay, and heterogeneity in the lower level vehicle dynamics. Such features are expected for automated driving systems.

Detector random time delay compensation method for X-ray pulsar observation

For recent few decades, the observation for X-ray emission of pulsar is very popular. Among the multiple experiments, to construct the signal profile of X-ray pulsar is a significant one. During the observation, the X-ray signal photons of pulsars need to be collected by sensors in space. At present, the applied silicon-based X-ray sensors include Silicon Drift Detector (SDD), Swept Charge Device (SCD) and so on. Owing to the X-ray photons reach different places on the sensor at a time, the photon arrival time these detectors record always includes random time delay. This kind of delay will decrease the accuracy of detected signal profile. Therefore, studying how to compensate this delay is very necessary. In this paper, the principle how sensor time delay affects the signal profile is presented. Furthermore, based on the deconvolution calculation, a time delay compensation method is proposed. According to simulation and the hardware-in-loop experiments, it can be proven that the method can eliminate the effects of profile time delay and profile distortion. The method can support astro observation in space and X-ray pulsar-based navigation.

Robust μ-synthesis controllers for suppressing stick-slip induced vibrations in oil well drill strings

Stick-slip friction is a major cause of drill-string failure. This paper addresses the problem of suppressing stick-slip induced oscillations in oil well drill strings using a control design technique known as μ-synthesis. This technique allows for the inclusion of modeling errors in the control design process in terms of uncertainty weights. The dynamic model of the drill string with stick-slip friction is highly nonlinear and has to be linearized around an operating point in order to use μ-synthesis. The difference between the linear and nonlinear models is characterized in terms of uncertainty weights and included in the control design process. The designed controllers are robust to uncertainty in the dynamic model, spillover, actuator uncertainty, and noise. Two controllers were designed using μ-synthesis and the simulation results are presented and discussed here. The first controller assumes no measurement delay; however, the second controller includes a sensor time delay in the measurements. Both controllers are robust and performed well.

Evolving factor analysis-based method for correcting monitoring delay in different batch runs for use with PLS: On-line monitoring of a transesterification reaction by ATR-FTIR

In this work, the base-catalyzed transesterification of soybean oil with ethanol was monitored on-line using mid-infrared spectroscopy (MIRS) and the yield of fatty acid ethyl esters (biodiesel) was obtained by 1H NMR spectroscopy. The MIRS monitoring carried out for 12 min, was performed using a cylindrical internal reflectance cell of PbSe in the range of 3707–814 cm −1 with eight co-added scans. Two different data treatment strategies were used: in the first, the models were built using the raw data and in the other, evolving factor analysis (EFA) was used to overcome the sensor time delay due to the on-line analysis, producing significantly better results. In addition, models based on partial least squares (PLS) using three batches for calibration and another for validation were compared with models with just one batch for calibration and three for validation. The models were compared between each other using root mean square error of prediction (RMSEP) and root mean square prediction difference (RMSPD), obtaining relative errors under 3%.

Distributed Simulation of Differential Algebraic Systems Using Optimal Sliding-Mode Control

In this paper, the optimal solution of differential algebraic equation (DAE) systems over a network of processors is investigated. A sliding-mode control (SMC) approach is used to enforce the algebraic constraints of the DAEs. Time delays associated with network communication give rise to a sliding-control problem with sensor time delays. A new approach is presented that decouples this problem into two independent problems. Using this property, a mixed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">infin</sub> optimization approach is applied to minimize errors. The results are applied to solve the problem of the optimal bandwidth allocation between the processors under the constraint of limited communication bandwidth. Experimental results for a distributed simulation application on a TDMA network demonstrate the validity of the approach

Characterizing the Substrate Control Problem of Ethanol Monitored Fed-Batch Yeast Production

The substrate control problem of fed-batch yeast production is investigated. The control principle is based on the fact that the yeast produces ethanol in case of over-feeding and consumes ethanol in case of under-feeding. A mathematical model is derived for the ethanol dynamics in a fed-batch reactor. The transfer function has one fix and one time-varying part. Several closed-loop identification experiments were done on laboratory scale, to validate the model at different cell concentrations. Interpretation of the data from these experiments are discussed in some detail. Data was fitted to time invariant linear models of different orders. It was possible to follow process variations under a cultivation. A wider experience from many ethanol controlled cultivations are also summarized. The most apparent difference between ethanol-controlled cultivations are deviations in the exponential feed rate profile. This is considered the main reason for control. The sensor time delay and dynamics impose a limitation on the control performance. However, the results from identification promise good possibilities for dead time compensation. Further, the structure of the time-variable, more uncertain part, can be described by a first order system, and this fact might be useful in control design. Differences in process dynamics between cultivations are also reported and the implications for tuning are discussed.