Actuators play a central role in industrial automation systems. They are costly, and therefore studying their dependability needs all attention. Usually, an actuator is inserted in a feedback control ...system, and its mission is to implement a control action delivered by a controller. In this paper, a monotonic actuator deterioration is considered and it is assumed that a relationship exists between the control action and the physical actuator׳s deterioration. A modeling framework is proposed including a non-decreasing stochastic degradation process driving the inability for an actuator to fully implement its role. The prognosis of the actuator׳s residual useful lifetime is derived and used to update the controller׳s setting. The controller reconfiguration completes the maintenance corrective and preventive actions. This new action is suggested as an alternative for maintenance strategy.
•A degrading control system model is proposed focusing on actuator deterioration.•It is assumed a relationship between this degradation and its loss of efficiency.•The actuator RUL is quantified as a quantile of its conditional survival function.•RUL prognosis is used to reconfigure the control input law.•This new action is suggested as an alternative for maintenance strategy.
The evolution in impedance at the electrode-skin interface of Beckman and Red Dot electrodes was assessed during long-term recordings. Impedance was measured between each pair of electrodes, arranged ...in a bipolar configuration on tibialis anterior (
n=13). A waveform constructed of sinusoids of known frequencies, evenly distributed on a log scale from 1–16,384 Hz, was applied through the electrodes, and the result recorded by a DAQ system. SEMG signals were recorded at 1000 Hz during isometric dorsiflexion contractions of 30 s, performed every 15 min for 2 h. Impedance data were acquired at 65,536 Hz immediately before and after SEMG recordings. Large individual differences in impedance levels were observed at low frequencies. At high frequencies, impedance values depended only on the electrode type. Impedance decreased steadily with time for Beckman electrodes (
p < 0.05), but did not decrease significantly for Red Dot electrodes. The magnitude of the reduction over time varied widely between individuals, and was related to the initial impedance values. The impedance-bandwidth product remained constant for each electrode type (95% confidence intervals 146.2–148.2 and 126.1–127.8 for Beckman and Red Dot electrodes respectively). When skin impedance is electrically modelled with a simple network containing a resistor and a capacitor, the capacitance varies with the properties of the electrode used, whereas resistance is dependent on the subject. Furthermore, the EMG spectrum is unaffected by impedance provided skin preparation is sufficient to reduce the impedance below 55 kΩ.
Degradation-based prognostics is crucial for the health management of technological systems. In this work, we are interested in the degradation index construction and remaining useful life ...prognostics for stochastically deteriorating feedback control systems. The main challenges reside in the lack of knowledge about the system structure and the latent internal damage, as well as in the fault tolerance nature of feedback control systems. Our solution is to consider the whole system as a black-box, and use its easy-to-observe reference input/time response output to estimate the system transfer function. The associated H∞ norm, also called maximum energy gain, is defined as a system degradation index. Since the system fault tolerance does not allow to efficiently model the index evolution by common stochastic processes, traditional prognostics based on degradation processes are no longer applicable. To remedy, we propose to fit the system remaining useful life population to the versatile Birnbaum–Saunders distribution, and adopt a segmenting piecewise polynomials algorithm to learn the mapping between the distribution parameters and degradation index from degradation and failure data of similar systems. By this way, the remaining useful life distribution of deteriorating feedback control systems can be predicted in real-time given the system input/output at an inspection time. We numerically experiment our method on a stabilization loop control device driven by proportional–integral–differential controller in an inertial platform. Numerous sensitivity results under various configurations of system characteristics and training data corroborate the outperformance of proposed degradation index and the learning-based prognostics method.
•Degradation-based prognostics for stochastically deteriorating feedback control systems.•Maximum energy gain constructed from the system input–output as degradation index.•Development of a learning-based method for remaining useful life prognosis.•Numerical experiments on a deteriorating stabilization loop control device.
This paper describes the use of kernel methods to classify tissue samples using near-infrared spectra in order to discriminate between samples, either with or without elastane. The aim of this ...real-world study is to identify an alternative method to classify textile products using near-infrared (NIR) spectroscopy in order to improve quality control, and to aid in the detection of counterfeit garments.
The principles behind support vector machines (SVMs), of which the main idea is to linearly separate data, are recalled progressively in order to demonstrate that the decision function obtained is a global optimal solution of a quadratic programming problem. Generally, this solution is found after embedding data in another space
F with a higher dimension by the means of a specific non-linear function, the kernel.
For a selected kernel, one of the most important and difficult subjects concerning SVM is the determination of tuning parameters. Generally, different combinations of these parameters are tested in order to obtain a machine with adequate classification ability. With the kernel alignment method used in this paper, the most appropriate kernel parameters are identified rapidly. Since in many cases, data are embedded in
F, a linear principal component (PC) analysis (PCA) can be considered and studied. The main properties and the algorithm of
k-PCA are described here. This paper compares the results obtained in prediction for a linear classifier built in the initial space with the PCs from a PCA and those obtained in
F with non-linear PCs from a
k-PCA.
In the present study, even if there are potentially discriminating wavelengths seen on the NIR spectra, linear discriminant analysis and soft independent modelling of class analogy results show that these wavelengths are not sufficient to build a machine with correct generalisation ability. The use of a non-linear method, such as SVM and its corollary methods, kernel alignment and
k-PCA, is then justified.
The evolution of indices of fatigue, discomfort, and performance of subjects seated for long duration (150
min) in car seats were studied (
n=11). Four experimental configurations were used: with and ...without vibration for two seats (U, uncomfortable; C, comfortable). Surface electromyography (SEMG) data were recorded bilaterally from cervical erector spinae and external oblique muscles. Discomfort increased significantly during the trial, regardless of the experimental condition (
p<0.05). Performance was significantly worse for seat U with vibration (
p<0.05). The median frequency of SEMG signals did not change between experimental conditions or across time. It would appear that, either the level of discomfort experienced was insufficient to change either performance or SEMG measures, or that the large parameter estimation variance of the SEMG signals might have masked any underlying spectral change. Further refinement of the SEMG signal processing methodology may be necessary to be able to detect fatigue of postural muscles.
With the fast-paced development of the Internet of Things and its applications within the emerging field of Industry 4.0 - decentralizing decisions by remotely monitoring data and automata - the ...issues of security and reliability of the whole communication pipeline between the connected devices taking part in this smart industry become crucial. In such context of embedded systems, microcontrollers are widely preferred over microprocessors as they are cheaper, smaller and less energy consuming. Unfortunately, the implementation of security features on microcontrollers, such as signing and ciphering functions, can largely reduce the availability of embedded systems because these functions are energy consuming and computationally complex. Thus, a trade-off has to be found between the prescribed level of availability and security. It is important to note that such a trade-off greatly depends on how the embedded systems will be used, how they are supposed to communicate between each other and if a central node with high computing resources is available. For instance, a common architecture typically consist of several embedded systems communicating up and down with a unique server. Indeed, this architecture is used in several areas where a monitor must supervise and treat data, which is the reason why this setup is chosen. The present paper aims at proposing a method to reach the right trade-off between security and availability, depending on the available resources. However, this problem is difficult to address because of the complexity to measure the security or the availability of a system. Solutions featuring those characteristics and a generic approach are presented to find the most suitable trade-off, in the use case of Industry 4.0.
This chapter aims at proposing a method to reach the right trade-off between security and availability, depending on the available resources. However, this problem is difficult to address because of the complexity to measure the security or the availability of a system. Authentication, integrity and confidentiality are based on mathematically complex functions. Moreover, security influences autonomy because these functions use computational power, hence energy, and reduce the autonomy of an embedded system. A balance must be found between security and energy consumption, reliability and real time constraints. The embedded system is an important variable on this problem. A modest micro-controller has been chosen to amplify the workload of both the receiver and emitter. Totally different encryption/decryption and signing/verifying algorithms can be used and compared on this embedded system. This comparison tool can be used to compare embedded systems instead of algorithms.
The aim of this paper is to combine the deterministic behavior of a feedback control system with an inner stochastic degradation process. For that, a modeling framework is proposed with an intrinsic ...deterioration caused by the control input law and its variations. As a consequence, when degrading the actuator has a loss of effectiveness to carry out this command. Two system missions are studied - slow and fast missions - with a Markov chain allowing to parameterize the sojourn times in the different system states. Finally, a basic PID controler commonly used in industrial automation is assessed regarding performances and lifetime aided with Monte Carlo simulations.
Aims: A multinational, randomized, double-blind, two-way crossover trial to compare the pharmacokinetic and pharmacodynamic properties of bolus, subcutaneously administered insulin glulisine ...(glulisine) and insulin aspart (aspart) in insulin-naÏve, obese subjects with type 2 diabetes. Methods: Thirty subjects 9/21 females/males; mean ± SD age: 60.7 ± 7.7 years; body mass index (BMI): 33.5 ± 3.3 kg/m²; duration of diabetes: 6.8 ± 4.6 years; HbA1c: 7.1 ± 0.8% were included in the analysis. They fasted overnight and then received a 0.2 U/kg subcutaneous dose of glulisine or aspart 2 min before starting a standardized test meal, 7 days apart, according to a randomization schedule. Blood samples were taken every 15 min, starting 20 min before the meal and ending 6 h postprandially. Results: The area under the absolute glucose concentration-time curve between 0 and 1 h after insulin injection and maximal glucose concentration was significantly lower with glulisine than with aspart (p = 0.0455 and 0.0337, respectively). However, for the total study period, plasma glucose concentration was similar for glulisine and aspart. Peak insulin concentration was significantly higher for glulisine than for insulin aspart (p < 0.0001). Hypoglycaemic events (≤ 70 mg/dl with or without symptoms) occurred in 13 and 16 subjects treated with glulisine and aspart, respectively, but there were no cases of severe hypoglycaemia requiring intervention. Conclusions: Glulisine was associated with lower glucose levels during the first hour after a standard meal; the remaining glucose profiles were otherwise equivalent, with higher insulin levels observed throughout the study period.
Abstract Aims Out-of-hospital cardiac arrest (OHCA) without return of spontaneous circulation (ROSC) despite conventional resuscitation is common and has poor outcomes. Adding extracorporeal membrane ...oxygenation (ECMO) to cardiopulmonary resuscitation (extracorporeal-CPR) is increasingly used in an attempt to improve outcomes. Methods and results We analysed a prospective registry of 13 191 OHCAs in the Paris region from May 2011 to January 2018. We compared survival at hospital discharge with and without extracorporeal-CPR and identified factors associated with survival in patients given extracorporeal-CPR. Survival was 8% in 525 patients given extracorporeal-CPR and 9% in 12 666 patients given conventional-CPR (P = 0.91). By adjusted multivariate analysis, extracorporeal-CPR was not associated with hospital survival odds ratio (OR), 1.3; 95% confidence interval (95% CI), 0.8–2.1; P = 0.24. By conditional logistic regression with matching on a propensity score (including age, sex, occurrence at home, bystander CPR, initial rhythm, collapse-to-CPR time, duration of resuscitation, and ROSC), similar results were found (OR, 0.8; 95% CI, 0.5–1.3; P = 0.41). In the extracorporeal-CPR group, factors associated with hospital survival were initial shockable rhythm (OR, 3.9; 95% CI, 1.5–10.3; P = 0.005), transient ROSC before ECMO (OR, 2.3; 95% CI, 1.1–4.7; P = 0.03), and prehospital ECMO implantation (OR, 2.9; 95% CI, 1.5–5.9; P = 0.002). Conclusions In a population-based registry, 4% of OHCAs were treated with extracorporeal-CPR, which was not associated with increased hospital survival. Early ECMO implantation may improve outcomes. The initial rhythm and ROSC may help select patients for extracorporeal-CPR.
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