Model-Free Output Feedback Path Following Control for Autonomous Vehicle With Prescribed Performance Independent of Initial Conditions

Time-delay control (TDC) is widely recognized as a robust and straightforward model-free control approach for complex systems. However, the transient performance and settling time are often given less consideration in most TDC-based controllers. In this article, we propose an integrated control protocol that combines fixed-time prescribed performance control with time-delay estimation techniques for autonomous ground vehicles. The proposed control paradigm offers the advantages of being model-free while ensuring that the preview error converges to a neighborhood of zero within a fixed time, adhering to predefined constraint functions. To overcome the limitations of commonly used exponential decay boundaries, a prescribed performance function that remains independent of the initial conditions is employed. Furthermore, a high-order model-free fixed-time differentiator is constructed to observe the high-order dynamics of the preview error, which are essential for estimating unknown model dynamics. Finally, the simulations and practical experiments have been conducted to demonstrate the superiority of our proposed control protocol

Adaptive Sliding Mode Fault Tolerant Control for Autonomous Vehicle With Unknown Actuator Parameters and Saturated Tire Force Based on the Center of Percussion

With consideration of tire force saturation in vehicle motions, a novel path-following controller is developed for autonomous vehicles with unknown-bound disturbances and unknown actuator parameters. An adaptive sliding-mode fault-tolerant control (ASM-FTC) strategy is designed to stabilize the path-following errors without any information of disturbance boundaries, actuator fault boundaries and steering ratio from the steering wheel to the front wheels. By selecting the distance from the center of gravity to the center of percussion as the preview length, the effects of the lateral rear-tire force are decoupled and cancelled out, and then the preview error, which represents the path-following performance, can be only commanded by the front-tire force. To further address the issue of unknown tire-road friction limits, a modified ASM-FTC strategy is presented to improve the path-following performance as the lateral tire force is saturated. Simulation results show that the modified ASM-FTC controller demonstrates superior tracking performance over the normal ASM-FTC while the autonomous vehicle follows desired paths

Distributed Fixed-Time Control for Leader-Steered Rigid Shape Formation with Prescribed Performance

Resorting to the principle of rigid body kinematics, a novel framework for a multi-robot network is proposed to form and maintain an invariant rigid geometric shape. Unlike consensus-based formation, this approach can perform both translational and rotational movements of the formation geometry, ensuring that the entire formation motion remains consistent with the leader. To achieve the target formation shape and motion, a distributed control protocol for multiple Euler-Lagrange robotic vehicles subject to nonholonomic constraints is developed. The proposed protocol includes a novel prescribed performance control (PPC) algorithm that addresses the second-order dynamics of the robotic vehicles by employing a combination of nonsingular sliding manifold and adaptive law. Finally, the effectiveness of the proposed formation framework and control protocol is demonstrated through the numerical simulations and practical experiments with a team of four robotic vehicles

A digital twin to quantitatively understand aging mechanisms coupled effects of NMC battery using dynamic aging profiles

Traditional lithium-ion battery modeling does not provide sufficient information to accurately verify battery performance under real-time dynamic operating conditions, particularly when considering various aging modes and mechanisms. To improve the current methods, this paper proposes a lithium-ion battery digital twin that can capture real-time data and integrate the strong coupling between SEI layer growth, anode crack propagation, and lithium plating. It can be utilized to estimate aging behavior from macroscopic full-cell level to microscopic particle level, including voltage-current profiles in dynamic aging conditions, predict the degradation behavior of Nickel-Manganese-Cobalt-Oxide (NMC) based lithium-ion batteries, and assist in electrochemical analysis. This model can improve the root cause analysis of cell aging, enabling a quantitative understanding of aging mechanism coupled effects. Three charging protocols with dynamic discharging profiles are developed to simulate real vehicle operation scenarios and used to validate the digital twin, combining operando impedance measurements, post-mortem analysis, and SEM to further prove the conclusions. The digital twin can accurately predict battery capacity fade within 0.4% MAE. The results indicate that SEI layer growth is the primary contributor to capacity degradation and resistance increase. Based on the analysis of the model, it is concluded that one of the proposed multi-step charging protocols, in comparison to a standard continuous charging protocol, can reduce the degradation of NMC-based lithium-ion batteries. This paper represents a firm physical foundation for future physics-informed machine learning development

Metabolizable energy requirement for maintenance estimated by regression analysis of body weight gain or metabolizable energy intake in growing pigs

Objective: Feed energy required for pigs is first prioritized to meet maintenance costs. Additional energy intake in excess of the energy requirement for maintenance is retained as protein and fat in the body, leading to weight gain. The objective of this study was to estimate the metabolizable energy requirements for maintenance (MEm) by regressing body weight (BW) gain against metabolizable energy intake (MEI) in growing pigs.Methods: Thirty-six growing pigs (26.3 +/- 1.7 kg) were allotted to 1 of 6 treatments with 6 replicates per treatment in a randomized complete block design. Treatments were 6 feeding levels which were calculated as 50%, 60%, 70%, 80%, 90%, or 100% of the estimated ad libitum MEI (2,400 kJ/kg BW0.60 d). All pigs were individually housed in metabolism crates for 30 d and weighed every 5 d. Moreover, each pig from each treatment was placed in the open-circuit respiration chambers to measure heat production (HP) and energy retained as protein (REp) and fat (REf) every 5 d. Serum biochemical parameters of pigs were analyzed at the end of the experiment.Results: The average daily gain (ADG) and HP as well as the REp and REf linearly increased with increasing feed intake (p< 0.010). beta-hydroxybutyrate concentration of serum tended to increase with increasing feed intake (p = 0.080). The regression equations of MEI on ADG were MEI, kJ/kg BW0.60 d = 1.88xADG, g/d+782 (R-2 = 0.86) and MEm was estimated at 782 kJ/kg BW0.60 d. Protein retention of growing pigs would be positive while REf would be negative at this feeding level via regression equations of REp and REf on MEI.Conclusion: The MEm was estimated at 782 kJ/kg BW0.60 d in current experiment. Furthermore, growing pigs will deposit protein and oxidize fat if provided feed at the estimated maintenance level

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

A wet process for oxidation-absorption of nitric oxide by persulfate/calcium peroxide

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.cej.2018.05.145 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/This study develops and evaluates a novel wet method for NO removal using a Na2S2O8/CaO2 solution. The effects of these two components both and alone in solution, Na2S2O8 concentration, CaO2 concentration, initial pH, reaction temperature, and the concentrations of NO and O2 on NO removal efficiency were evaluated using a bubbling reactor. The combination of Na2S2O8 and CaO2 had a synergistic effect on NO removal efficiency. NO removal was effected by CaO2 concentration, reaction temperature and the initial solution pH, while Na2S2O8 concentration and O2 concentration had little effect. The NO removal efficiency decreased linearly from 94.5 % to 75.1 % when the NO concentration increased from 139 to 559 ppm. The products were characterized using XRD, XPS and IC, and CaSO4·2H2O, NO3− and SO42− were found to be the main products. The EPR analysis showed that free radicals of O2−, SO4− and OH were the key species involved in the NO removal process. Finally, the corresponding reaction mechanisms were proposed.International S&T Cooperation Program of China [Grant No. 2015DFG61910

On the validity of the local Fourier analysis

Local Fourier analysis (LFA) is a useful tool in predicting the convergence factors of geometric multigrid methods (GMG). As is well known, on rectangular domains with periodic boundary conditions this analysis gives the exact convergence factors of such methods. In this work, using the Fourier method, we extend these results by proving that such analysis yields the exact convergence factors for a wider class of problems

Effect of sequential treatment with syndrome differentiation on acute exacerbation of chronic obstructive pulmonary disease and "AECOPD Risk-Window": study protocol for a randomized placebo-controlled trial

BACKGROUND: Frequent chronic obstructive pulmonary disease (COPD) exacerbation is a major cause of hospital admission and mortality. It has been reported that Traditional Chinese Medicine (TCM) may relieve COPD symptoms and reduce the incidence of COPD exacerbations, thus improving life quality of COPD patients. The acute exacerbation of COPD risk-window (AECOPD-RW) is the period after an exacerbation and before the patient returns to baseline. In the AECOPD-RW, patients are usually at increased risk of a second exacerbation, which may lead to hospital admission and high mortality. It may be beneficial for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients to receive interventions during AECOPD-RW. During exacerbations the treatment principle is to eliminate exogenous pathogens, whereas the AECOPD-RW treatment principle focuses on enhancing body resistance. METHODS/DESIGN: A prospective, multi-center, single-blinded, double-dummy and randomized controlled clinical trial is being conducted to test the therapeutic effects of a sequential two stage treatment, which includes eliminating pathogen and strengthening vital qi with syndrome differentiation. A total of 364 patients will be enrolled in this study with 182 in each treatment group (TCM and control). Patients received medication (or control) according to their assigned group. TCM for AECOPD were administered twice daily to patients with AECOPD over 7 to 21 days, followed by TCM for AECOPD-RW over 28 days. All patients were followed for six months. The clinical symptoms, the modified medical research council dyspnea (MMRC) scale and exacerbations were used as the primary outcome measures. Pulmonary function, quality of life and mortality rate were used as secondary outcome measures. DISCUSSION: It is hypothesized that sequentially eliminating pathogens and strengthening vital qi treatments with syndrome differentiation will have beneficial effects on reducing the frequency and duration of acute exacerbation, relieving symptoms and improving quality of life for COPD patients. TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov, ChiCTR-TRC-11001460

Analysis of Reservoir Architecture of Shallow-water Delta Front Based on Process—A Case of S2L410 in Southern 79 Block in Wennan Oilfield

The sand body distribution is relatively limited in this block, the lens-shaped sandbodies are more developed, the change of intergranular sandbody is fast and the internal architecture of the sand body is complex, which results in the difficulties of the arrangement of horizontal wells in the study area and the tapping of remaining oil in high water reservoirs. In this paper, taking an example of S2L410 sandbodies in Wen 79 Southern Block, rich drilling data, core data, logging data and geological research results accumulated over many years in Wennan Oilfield were applied to discuss the anatomical method of the reservoir architecture unit in the underwater distributary channel in the shallow delta front, the hierarchy of the internal architecture of the reservoir and the anatomy of the single sand body. On the basis of this, the sequence of the underwater distributary channel in the composite channel is determined by the cross section and the source profile. Under the guidance of the sedimentology principle, the formation process of the underwater distributary channel is restored and the evolution process of underwater distributary channel is recovered