Time Delay Response Research Articles

Multi-objective optimization for connected and automated truck platoon control with improved CACC model

Connected and Automated Truck Platoon (CATP) refers to a group of trucks traveling closely together with minimal spacing to improve fuel economy and safety. However, challenges arise from instability due to internal platoon factors and external traffic disturbances. This research presents an improved Cooperative Adaptive Cruise Control (CACC) model tailored for CATP to address these challenges. The model is designed to enhance safety, fuel efficiency, and traffic efficacy. The improvements of the proposed model are in two aspects: the optimizing of the time headway strategy and the dynamic parameter adjustments of controller based on multi-objectives. The Dynamic Safety Requirement Time Headway (DSRTH) strategy facilitates the timely detection of the accelerations of the leading vehicles within the platoon, enabling quick driving responses. Additionally, Model Predictive Control (MPC) enables dynamic calibration of Proportional-Derivative (PD) control parameters and issuance of velocity commands. Meanwhile, the integration of a second-order time-delay response model has been implemented to adapt to dynamic changes in commands. A transfer function has been established, and stability has been proven. To evaluate the model performance, simulation analysis was performed using real vehicle trajectories as the CATP following vehicles. The results indicate that the DSRTH strategy outperforms both the Constant Time Headway (CTH) and Variable Time Headway (VTH) strategies, allowing rear vehicles to reach the speed trough earlier, with response speeds improved by 3.1 % and 1.5 %, respectively. Compared to the Intelligent Driver Model (IDM) and CACC models, the improved CACC model achieves a steady state of constant acceleration sooner, with recovery times reduced by 17.7 % and 3.2 %. Additionally, compared to the IDM model, the improved CACC model can save 3.23 % in fuel consumption. Furthermore, sensitivity analysis indicates that as the CATP proportion and platoon size increase, there is a positive impact on traffic flow. However, when the platoon size exceeds 5 vehicles, it shows a negative impact on the stability of other vehicles in the traffic flow besides those in the CATP.

No Combined Effect of Caffeinated Chewing Gum and Priming Exercise on Oxygen Uptake and Muscle Near-Infrared Spectroscopy-Derived Kinetics: A Double-Blind Randomized Crossover Placebo-Controlled Trial in Cyclists.

This study aimed to investigate the effects of caffeine ingestion by chewing gum (GUMCAF) combined with priming exercise on pulmonary oxygen uptake (V˙O2) and near-infrared spectroscopy-derived muscle oxygen extraction (HHb + Mb) kinetics during cycling performed in a severe-intensity domain. Fifteen trained cyclists completed four visits: two under a placebo gum (GUMPLA) and two under GUMCAF ingestion. Each visit consisted of two square-wave cycling bouts at Δ70 intensity (70% of difference between the V˙O2 at first ventilatory threshold and V˙O2max) with duration of 6min each and 5min of passive rest between the bouts. The GUMPLA or GUMCAF (400mg) was chewed for 5min, 12min before the first Δ70 bout in a randomized double-blind procedure. The fundamental phase and slow component of HHb + Mb and V˙O2 kinetics were evaluated. For HHb + Mb kinetics, regardless of ingested gum, priming exercise effects occurred on the time constant (GUMCAF 16.0 ± 4.0 vs. 13.9 ± 2.9s; GUMPLA 15.7 ± 6.1 vs. 13.2 ± 2.5s), amplitude, slow component, time delay, and mean response time parameters (p ≤ .032). For V˙O2 kinetics, there were significant effects of bouts on the amplitude, slow component, end V˙O2, and the gain kinetics parameters (p < .017). Baseline V˙O2 was higher during GUMCAF than GUMPLA (p = .020). No significant effects occurred for the interaction between gum and bout in any parameter of V˙O2 or HHb + Mb kinetics. Therefore, unlike the priming exercise in severe-intensity exercise, GUMCAF is not an effective strategy for improving V˙O2 or HHb + Mb kinetics acceleration.

A portable AFO solution for pneumatic actuator with cable tendon mechanism to assist ankle dorsiflexion

The limited portability of pneumatic pumps presents a challenge for ankle-foot orthosis actuated by pneumatic actuators. The high-pressure requirements and time delay responses of pneumatic actuators necessitate a powerful and large pump, which renders the entire device heavy and inconvenient to carry. In this paper, we propose and validate a concept that enhances portability by employing a slack cable tendon mechanism. By managing slack tension properly, the time delay response problem of pneumatic actuators is eliminated through early triggering, and the system can be effectively controlled to generate the desired force for dorsiflexion assistance. The current portable integration of the system weighs approximately 1.6 kg, with distribution of 0.5 kg actuation part on the shank and 1.1 kg power system on the waist, excluding the battery. A mathematical model is developed to determine the proper triggering time and volumetric flow rate requirements for pump selection. To evaluate the performance of this actuation system and mathematical model, the artificial muscle’s response time and real volumetric flow rate were preliminarily tested with different portable pumps on a healthy participant during treadmill walking at various speeds ranging from 0.5 m/s to 1.75 m/s. Two small pumps, specifically VN-C1 (5.36 L/min, 300 g) and VN-C4 (9.71L/min, 550 g), meet our design criteria, and then tested on three healthy subjects walking at normal speeds of 1 m/s and 1.5 m/s. The kinematic and electromyographic results demonstrate that the device can facilitate ankle dorsiflexion with a portable pump (300–500 g), generating sufficient force to lift up the foot segment, and reducing muscle activity responsible for ankle dorsiflexion during the swing phase by 8% and 10% at normal speeds of 1 m/s and 1.5 m/s respectively. This portable ankle robot, equipped with a compact pump weighing approximately 1.6 kg, holds significant potential for assisting individuals with lower limb weakness in walking, both within their homes and in clinical settings.

Adaptive Sliding Mode Feedback Control Algorithm for a Nonlinear Knee Extension Model

Functional electrical stimulation (FES) has been widely used to treat spinal cord injury (SCI) patients. Many research studies employ a closed-loop FES system to monitor the stimulated muscle response and provide a precise amount of charge to the muscle. However, most closed-loop FES devices perform poorly and sometimes fail when muscle nonlinearity effects such as fatigue, time delay response, stiffness, spasticity, and subject change happen. The poor performance of the closed-loop FES device is mainly due to discrepancies in the feedback control algorithms. Most of the existing feedback control algorithms were not designed to adapt to new changes in patients with different nonlinearity effects, resulting in early muscle fatigue. Therefore, this research proposes an adaptive sliding mode (SM) feedback control algorithm that could adapt and fine-tune internal control settings in real-time according to the current subject’s nonlinear and time-varying muscle response during the rehabilitation (knee extension) exercise. The adaptive SM feedback controller consists mainly of system identification, direct torque control, and tunable feedback control settings. Employing the system identification unit in the feedback control algorithm enables real-time self-tuning and adjusting of the SM internal control settings according to the current patient’s condition. Initially, the patient’s knee trajectory response was identified by extracting meaningful information, which included time delay, rise time, overshoot, and steady-state error. The extracted information was used to fine-tune and update the internal SM control settings. Finally, the performance of the proposed adaptive SM feedback control algorithm in terms of system response time, stability, and rehabilitation time was analysed using a nonlinear knee model. The findings from the simulation results indicate that the adaptive SM feedback controller demonstrated the best control performance in accurately tracking the desired knee angle movement by having faster response times, smaller overshoots, and lower steady-state errors when compared with the conventional SM across four reference angle settings (20°, 30°, 40°, and 76°). The adaptive feedback SM controller was also observed to compensate for muscle nonlinearities, including fatigue, stiffness, spasticity, time delay, and other disturbances.

Cerebral blood flow dynamics: Is there more to the story at exercise onset?

A monoexponential model characterizing cerebral blood velocity dynamics at the onset of exercise may mask dynamic responses by the cerebrovasculature countering large fluctuations of middle cerebral artery blood velocity (MCAv) and cerebral perfusion pressure (CPP) oscillations. Therefore, the purpose of this study was to determine whether the use of a monoexponential model attributes initial fluctuations of MCAv at the start of exercise as a time delay (TD). Twenty-three adults (10 women, 23.9 ± 3.3 yrs; 23.7 ± 2.4 kg/m2 ) completed 2 min of rest followed by 3 mins of recumbent cycling at 50 W. MCAv, CPP, and Cerebrovascular Conductance index (CVCi), calculated as CVCi = MCAv/MAP × 100 mmHg, were collected, a lowpass filter (0.2 Hz) was applied, and averaged into 3-second bins. MCAv data were then fit to a monoexponential model [ΔMCAv(t) = Amp(1 - e-(t-TD)/τ )]. TD, tau (τ), and mean response time (MRT = TD + τ) were obtained from the model. Subjects exhibited a TD of 20.2 ± 18.1 s. TD was directly correlated with MCAv nadir (MCAvN ), r = -0.560, p = 0.007, which occurred at similar times (16.5 ± 15.3 vs. 20.2 ± 18.1 s, p = 0.967). Regressions indicated CPP as the strongest predictor of MCAvN ( = 0.36). Fluctuations in MCAv were masked using a monoexponential model. To adequately understand cerebrovascular mechanisms during the transition from rest to exercise, CPP and CVCi must also be analyzed. A concurrent drop in cerebral perfusion pressure and middle cerebral artery blood velocity at the start of exercise forces the cerebrovasculature to respond to maintain cerebral blood flow. The use of a monoexponential model characterizes this initial phase as a time delay and masks this large important response.

Robust Optimal Control for Wastewater Treatment Process With Uncertain Time Delays

To achieve the excellent operational performance of the wastewater treatment process, optimal control has been considered a reliable method. However, there is a time-delay response of the operation performances to the process variables, leading to uncertainties of operational optimal objectives. It is difficult to obtain the optimal set-points due to the uncertain operational optimal objectives. Therefore, a kernel-density-estimation-based robust optimal control (KDE-ROC) method is proposed. First, a data-driven prediction strategy is developed to construct the uncertain operational optimal objectives. Based on the time-delay intervals, the uncertainties between process variables and operational optimal objectives are expressed. Second, a kernel-density-estimation-based robust optimization algorithm is designed to solve the uncertain operational optimal objectives. Then, the optimal set-points of process variables are obtained depending on the robustness index to reduce the influence of uncertainties. Third, an adaptive neural network controller is developed to track the optimal set-points of process variables. Finally, the proposed KDE-ROC is applied in benchmark simulation model No.1. In the experimental results, the optimal control performance of KDE-ROC is compared with some effective optimal control strategies to demonstrate its effectiveness.

Controller Design and StabilityAnalysis of Intensification Process using Analytical Exact Gain-Phase Margin approach.

The controllable intensified process has received immense attention from researchers in order to deliver the benefit of process intensification to be operated in a desired way to provide a more sustainable process toward reduction of environmental impact and improvement of intrinsic safety and process efficiency. Despite numerous studies on gain and phase margin approach on conventional process systems, it is yet to be tested on intensified systems as evidenced by the lack of available literature, to improve the controller performance and robustness. Thus, this paper proposed the exact gain and phase margin (EGPM) through analytical method to develop suitable controller design for intensified system using Proportional-Integral-Derivative (PID) controller formulation, and it was compared to conventional Direct Synthesis methods (DS), Internal Model Control (IMC), and Industrial IMC method in terms of the performance and stability analysis. Simulation results showed that EGPM method provides good setpoint tracking and disturbance rejection as compared to DS, IMC, and Industrial IMC while retaining overall performance stability as time delay increases. The Bode Stability Criterion was used to determine the stability of the open-loop transfer function of each method and the result demonstrated decrease in stability as time delay increases for controllers designed using DS, IMC, and Industrial IMC, and hence control performance degrades. However, the proposed EGPM controller maintains the overall robustness and control performance throughout the increase of time delay and outperform other controller design methods at higher time delay with [Formula: see text] uncertainty test. Additionally, the proposed EGPM controller design method provides overall superior control performance with lower overshoot and shorter rise time compared to other controllers when process time constant is smaller in magnitude ([Formula: see text]) than the instrumentation element, which is one of the major concerns during the design of intensified controllers, resulting overall system with a higher order. The desired selection of gain margin and phase margin were suggested at 2.5 to 4 and 60 °-70[Formula: see text],respectively, for a wide range of control conditions for intensified processes where higher instrumentation dynamic would be possible to achieve robust control as well. The proposed EGPM method controller is thought to be a more reliable design strategy for maintaining the overall robustness and performance of higher order and complex systems that are highly affected by time delay and high dynamic response of intensified processes.

Dry and Wet Changes and Vegetation Time-Delay Responses in Western China

Due to global warming and other climate changes, it is increasingly important to study the response of regional environmental changes and dynamic changes in vegetation to climate change. Based on meteorological data from the last 60 years, this paper calculates the humidity index of western China under a wide range of long time series in different regions and explores the cross-correlation effect between series by offering a comparison with NDVI data, to analyze the cross-correlation between wet and dry changes and changes in vegetation in western China on a spatial scale. The results show that the spatial distribution of the interdecadal humidity index is different between different regions in western China. For example, the semi-arid and the semi-humid zones of the Weihe River region exhibit significant changes, while the Xinjiang and Qinghai–Tibet regions show a trend of constant wetness, on the whole, and the Sichuan and Yunnan–Guizhou regions are relatively humid and the distribution of wetness and dryness is relatively stable. The distribution of high and low values of the humidity index is very obvious and consistent with that of the distribution of desert bare land and precipitation in western China. In common with the distribution in the humidity index, the maximum correlation number between the NDVI and the humidity index in the whole western region is also significantly different in spatial distribution. There is a positive correlation between the NDVI and the humidity index in 99% of the study area. However, the delay in response time of the NDVI to changes in the humidity index in each region is inconsistent. For example, changes in the NDVI lag changes in the humidity index in the Menggan region by generally either 2 months or 5 months, while in the Sichuan region the delay in response time is generally 3 months. The variation and trend in dry and wet areas are closely related to the geographical location, climate zone, and topographic terrain, which may be the reason for the differences in the distribution of vegetation types and the response time to dry and wet changes. There is significant interaction between the humidity index and the vegetation type or precipitation distribution in western China. The positive correlation between the NDVI and the humidity index means that the positive effect is more sensitive, and the response of grassland is the most sensitive in the ecosystem.

Spectral Features of Forbush Decreases during Geomagnetic Storms

Geomagnetic storms and Forbush decreases (FD) on Earth are primarily caused by interplanetary coronal mass ejections (ICMEs) and stream/corotating interaction regions (SIRs/CIRs) originating in the Sun, which are propagated as a low-energy plasma disturbance through the interplanetary magnetic field (IMF). In this paper, we study the variations of the solar-wind parameters (solar wind velocity, plasma density, and IMF-Bz component) and the Earth's disturbance storm-time index (Dst) in relation to cosmic ray flux measurements from 8 neutron monitor stations distributed over Canada, Russia, Finland, and Greenland, during 3 intense geomagnetic storms occurred during the 24th solar cycle (March 16–18, 2015, June 21–23, 2015, and September 7–9, 2017). The wavelet analysis of the cosmic ray intensity reveals the clear evolution of the classical two-step FD with a peak period of approximately 2.1 h. The correlation-delay analysis shows a very strong correlation (∼0.9) between the relative count rate changes in cosmic ray intensity and the indices of solar wind speed and Dst. We obtain similar time-delay responses to the solar wind speed for all the cases (∼4 h), but large discrepancies are seen for the Dst index between the storms. We, therefore, recommend not using the Dst index for predicting Forbush decreases. Finally, we employ the resulting delay times to parameterise the Forbush decreases in terms of the solar wind, and we obtain a predictive model with R2 parameter of an approximate value of 0.8. Moreover, we observe a possible dependence on solar wind proton density which modulates the magnitude of Forbush decreases under similar solar wind speed conditions. Our results verify the suitability of using solar wind parameters to predict Forbush decreases in the cosmic ray flux.

A comparison of dissolving microneedles and transdermal film with solid microneedles for iloperidone in vivo: a proof of concept.

Iloperidone (ILO) is a poorly soluble and bioavailable WHO-approved schizophrenia drug. Microneedles are a revolutionary delivery technology that overcomes many of the issues associated with traditional drug administration. The current research aimed to compare the antipsychotic activity and pharmacokinetics of ILO-loaded dissolving microneedles (DMNs) and transdermal film with a solid microneedle (STF). The DMNs were fabricated using the micromolding process, while the transdermal film was created using the solvent casting approach. Furthermore, an in vivo pharmacokinetic, pharmacodynamic, and skin irritation study was performed on Wistar rats. Studies were compared with transdermal film (TF) on untreated skin as a passive control. STF and DMNs had considerably greater AUC and Cmax (p ≤ 0.001) than transdermal film. In pharmacodynamic tests, STF and DMNs demonstrated significant (p ≤ 0.001) forelimb retraction time (FRT) and hindlimb retraction time (HRT) delay responses as compared to control and TF. In the skin irritation test, no adverse effects such as erythema or edema were observed at the end of the 48h. Thus, antipsychotic activity (paw test) and pharmacokinetics studies revealed sustained action of DMN and STF. This research revealed that improved efficacy of DMN and STF for antipsychotic drug delivery may be an alternative to the existing dosage form.

Evaluation of the Response to Pulpal Sensibility Tests (Cold, EPT) in Anemic and Healthy Women.

Introduction The prevalence of anemia has been reported high in the female population in Iran. Anemia can be asymptomatic or can present in a variety of symptoms, especially when serum Hb values decrease. The present study would assess dental pulp response to cold and EPT sensibility tests in anemic and healthy women. Materials and Methods One hundred twenty maxillary central incisors belonging to participants aged 18–58 years were included in this survey. 60 patients had anemia (Hb ≤ 12.5) with/without medication (30 in each group) and 60 women as controls had no anemia (Hb > 12.5) with/without medication (30 in each group). Electric and cold pulpal sensibility tests were performed for all teeth. Statistical analysis was performed with t-student, Chi-square test, and two-way ANOVA. The significance level was set as p < 0.05. Results According to the results of this study, the mean value of hemoglobin in anemic and healthy women was 11.5 and 14.08 g/dl, respectively. The mean value of response to EPT in anemic women with and without medication was 3.21 and 3.14, respectively. The mean value of response to EPT in healthy women with and without medication was 3.81 and 3.58 g/dl, respectively. The mean value of time delay response to cold test was 3.03 and 2.82 s in anemic patients with/without medication. Also, the mean value of time delay response to cold test was 2.80 and 2.93 s in healthy women with/without medication. The pulpal responses to EPT tests had significant differences between anemic and healthy women (p=0.043). There were no significant differences between anemic and healthy women considering time delay response to the cold test (p=0.077). Conclusion Based on the results of the present study, tooth response to the EPT sensibility test may alter in anemic patients despite medication. The evidence from this preliminary study suggests that peripheral neuropathy in anemic patients could affect pulpal sensibility tests.

Stability analysis of a predator-prey model with stage structure

Many scholars have explored the population dynamics system, functional response, time-delay response, and so on. Based on the existing research, this paper studies a class of predator-prey models with stage structure, time delay, and Holling type-II functional response function. The stability of that model at the positive equilibrium point, the sufficient condition for stability, and the existence of Hopf bifurcation are discus. The model was numerically simulated by taking appropriate parameters and different time delay values, variation diagram of each component, and solution curves were given near the critical value. The results show that the stability of the system will change with the variation of the bifurcation parameter value, and Hopf bifurcation will occur.

Cerebrovascular Dynamics During Light Exercise

Cerebral blood flow (CBF) dynamic response to moderate‐intensity exercise has a time delay (TD) of ~ 40s. This is dramatically longer compared to other physiological responses to exercise (e.g. skeletal muscle blood flow &lt;10 s) and CBF response to other stimuli (e.g. hypercapnia, thigh cuff occlusion, ~ 10‐20 s). A possible explanation is that a rest‐to‐exercise transition induces a brief hypotensive response due to intensity dependent rapid vasodilation of the periphery (exercise‐onset hypotension, EoH).PurposeTo determine if the magnitude and timing of EoH, effectively reduces CBF at exercise onset causing the longer observed TD. To test this, we modelled CBF kinetic response to light‐intensity exercise to mitigate the magnitude of EoH and determine if components of the CBF response were quickened in young healthy adults.Methods26 young healthy adults (13 Women, 23.8 ± 4 yrs; 23.9 ± 2.9 kg/m2) completed a rest (2min seated quietly, BL) to exercise (3 minutes at 50W, EX) transition on a recumbent cycle ergometer. Middle cerebral artery velocity (MCAv; transcranial doppler) and mean arterial pressure (MAP; finger photoplethysmography) were measured on a heartbeat‐by‐heartbeat basis. End‐tidal CO2 (EtCO2) was measured using breath‐by‐breath capnography. Cerebral vascular conductance index (CVCi) was calculated as (CVCi = MCAv/MAP *100 mmHg). Change in MCAv data (ΔMCAv = MCAvEX‐MCAvBL) were averaged into 2 s bins and fit to a monoexponential model (ΔMCAv(t)= Amp(1‐e‐(t‐TD)/ τ)). Time delay (TD), tau (τ), and mean response time (MRT = TD + τ) were obtained from the model. Several subjects (N=11) exhibited little to no TD (TD &lt; 1 s), these subjects (FAST) were separated out and compared to individuals with longer TDs (TD ≥ 3 s; SLOW). Comparisons were made using an independent t‐test.ResultsAll data is mean±SD. In total, subjects exhibited a TD of 15.4 ± 18.2 s, τ of 79.8 ± 139.7, and MRT of 95.3 ± 134.9 s. This coincided with a ΔMAPNADIR (‐14.5 ± 8.2 mmHg), ΔMCAvNADIR (‐5.7 ± 5.8 cm/s) which occurred at similar times (14.0 ± 17.2 vs. 18.6 ± 14.4 s; p=0.30 MAPNADIR vs. MCAvNADIR), and ΔCVCiMAX (25.3 ± 34.0 cm/s/100mmHg). When data were split, the FAST group experienced a faster TD compared to SLOW (0.01 ± 0.01 vs. 26.8 ± 16.4 s; p&lt;0.001). ΔMCAvNADIR although different (‐1.0 ± 4.0 vs. ‐9.1 ± 4.2 cm/s; p&lt;0.001, FAST vs. SLOW), occurred at similar times (20.5 ± 17.3 vs. 17.3 ± 12.5 s; p=0.59, FAST vs. SLOW). ΔMAPNADIR (‐14.4 ± 10.4 vs. ‐14.6 ± 6.5 mmHg; p=0.97) and CVCiMAX (22.1 ± 25.4 vs. 27.6 ± 39.9 cm/s/100mmHg; p=0.56 FAST vs. SLOW) were not different between groups. There were no other differences between groups regrading demographic, EtCO2, or other kinetic variables.DiscussionOur data indicates EoH is related to the initial drop in CBF and TD during light‐exercise is faster (15.9 s) when compared to previous research during moderate‐intensity exercise (~40 s). However, our data identifies fast responders who have minimal TD and MCAvNADIR responses without differing EoH at the same absolute exercise intensity. Therefore, these data reveal monoexponential CBF models ignore initial perturbances to CBF and disregard potentially important cerebrovascular mechanisms occurring prior to model predicted blood flow increases.

Novel application of a force sensor during sit-to-stands to measure dynamic cerebral autoregulation onset.

Current sit‐to‐stand methods measuring dynamic cerebral autoregulation (dCA) do not capture the precise onset of the time delay (TD) response. Reduced sit‐to‐stand reactions in older adults and individuals post‐stroke could inadvertently introduce variability, error, and imprecise timing. We applied a force sensor during a sit‐to‐stand task to more accurately determine how TD before the onset of dCA may be altered. Middle cerebral artery blood velocity (MCAv) and mean arterial pressure (MAP) were measured during two sit‐to‐stands separated by 15 min. Recordings started with participants sitting on a force‐sensitive resistor for 60 s, then asked to stand for 2 min. Upon standing, the force sensor voltage immediately dropped and marked the exact moment of arise‐and‐off (AO). Time from AO until an increase in cerebrovascular conductance (CVC = MCAv/MAP) was calculated as TD. We tested the sensor in four healthy young adults, two older adults, and two individuals post‐stroke. Healthy young adults stood quickly and the force sensor detected a small change in TD compared to classically estimated AO, from verbal command to stand. When compared to the estimated AO, older adults had a delayed measured AO and TD decreased up to ~53% while individuals post‐stroke had an early AO and TD increased up to ~14%. The stance time during the sit‐to‐stand has the potential to influence the TD before the onset of dCA metric. As observed in the older adults and participants with stroke, this response may drastically vary and influence TD.

A Novel Efficacious PID Controller for Processes With Inverse Response and Time Delay

Design of controller for the inverse response processes has been a challenge for researchers. Water level control in a steam boiler is one of the best examples, where the time delay and inverse response are inherent. Proportional Integral Derivative(PID) controller is the extensively employed regulator in industries. The present work introduces a new form of PID for the processes which are having time delay and inverse response simultaneously. The proposed PID is associated with a higher order filter. The controller and filter parameters are computed by using polynomial approach. Maximum sensitivity of the control loop is used to determine the tuning parameter. A set-point filter is utilized to diminish the settling time and overshoot in servo response. The suggested method is evaluated by considering several performance indices and bench marking examples. The proposed method is evaluated against the existing methods and tested in real-time scenario also.

A novel modified Lévy flight distribution algorithm to tune proportional, integral, derivative and acceleration controller on buck converter system

In this paper, an optimal proportional, integral, derivative and acceleration (PIDA) controller design based on Bode’s ideal reference model and a novel modified Lévy flight distribution (mLFD) algorithm is proposed for buck converter system. The modification of the original Lévy flight distribution (LFD) algorithm was achieved by improving exploration and exploitation capabilities of the algorithm through incorporation of opposition-based learning mechanism and hybridizing with simulated annealing algorithm, respectively. The modified algorithm was used to tune the gains of the PIDA controller in order to operate a buck converter system that is mimicking the response of the Bode’s ideal reference model. Both the proposed novel algorithm and its PIDA controller design implementation for buck converter were confirmed through various tests and extensive analyses of statistical and non-parametric tests, convergence profile, transient and frequency responses, disturbance rejection, robustness, and time delay response. The comparative results with the state-of-the-art algorithms of manta ray foraging optimization, arithmetic optimization algorithm and the original LFD algorithm have shown that the proposed mLFD algorithm performs better than the compared ones in all assessments even when different well-known performance indices are used. The proposed Bode’s ideal reference model-based optimal PIDA control design with novel mLFD algorithm was also compared with other design approaches using the same buck converter system available in the literature. The proposed mLFD algorithm-based design approach has also shown greater effectiveness compared to other available methods, as well.

Chirped fiber grating and specialty fiber based multiwavelength optical beamforming network for 1X8 phased array antenna in S-band

In this paper, theoretical and experimental analysis has been done for the beam transmission of 2.2 GHz RF signal by 1X8 linear phased array antenna fabricated in S-band. The proposed architecture is based on true time delay optical beam forming network which gives squint free beam steering of RF signal. The optical beam forming network is based on chirp fiber Bragg grating (CFBG) and multiple lengths of highly dispersive specialty fiber element. Here, double sideband modulation technique of multiple wavelengths are adopted which explore the reflection property of CFBG with various chirp bandwidth. We measured the reflectivity and time delay response of CFBG, and dispersive fiber elements with theoretical analysis which is verified by experimental results. Theoretical and experimental measurements for the relative time delay was used to investigate the beam radiation pattern of 1X8 phased array antenna through simulation results. Wide range of beam steering ranges 3.5° to 18° have been achieved when specialty fiber of −100 ps/nm km dispersion coefficient was introduced.

Dynamics in a diffusive plankton system with time delay and Tissiet functional response

Dynamics in a diffusive plankton system with time delay and Tissiet functional response

A Generic Methodology for Calculating Rescheduling Time for Multiple Unexpected Events in the Era of Zero Defect Manufacturing

Nowadays, the manufacturing industry is constantly changing. Production systems must operate in a highly dynamic environment where unexpected events could occur and create disruption, making rescheduling inevitable for manufacturing companies. Rescheduling models are fundamental to the robustness of production processes. This paper proposes a model to address rescheduling caused by unexpected events, aiming to achieve the zero-defect manufacturing (ZDM) concept. The goal of the model is to incorporate traditional and ZDM–oriented events into one methodology to calculate when the next rescheduling will be performed to effectively react to unexpected events. The methodology relies on the definition of two key time parameters for each event type: event response time (RT) and event delay response time (DRT). Based on these parameters, an event management algorithm is designed to identify the optimal rescheduling solution. The DRT parameter is calculated based on a multi-parametric dynamic formula to capture the dynamics of production. Moreover, ANOM, and ANOVA methods are used to analyse the behaviour of the developed method and to assess the level of robustness of the proposed approach. Finally, a case study based on real production scenarios is conducted, a series of simulation experiments are performed, and comparisons with other rescheduling policies are presented. The results demonstrate the effectiveness of the proposed event management algorithm for managing rescheduling.

Effect of PEMF on Muscle Oxygenation during Cycling: A Single-Blind Controlled Pilot Study

Pulsed electromagnetic fields (PEMFs) are used as non-invasive tools to enhance microcirculation and tissue oxygenation, with a modulatory influence on the microvasculature. This study aimed to measure the acute effect of PEMF on muscle oxygenation and its influence on pulmonary oxygen kinetics during exercise. Eighteen male cyclists performed, on different days, a constant-load exercise in both active (ON) and inactive (OFF) PEMF stimulations while deoxyhemoglobin and pulmonary oxygen kinetics, total oxygenation index, and blood lactate were collected. PEMF enhanced muscle oxygenation, with higher values of deoxyhemoglobin both at the primary component and at the steady-state level. Moreover, PEMF accelerated deoxyhemoglobin on-transition kinetic, with a shorter time delay, time constant, and mean response time than the OFF condition. Lactate concentration was higher during stimulation. No differences were found for total oxygenation index and pulmonary oxygen kinetics. Local application of a precise PEMF stimulation can increase the rate of the muscle O2 extraction and utilization. These changes were not accompanied by faster oxygen kinetics, reduced oxygen slow component, or reduced blood lactate level. It seems that oxygen consumption is more influenced by exercise involving large muscle mass like cycling, whereas PEMF might only act at the local level.