Closed-loop Scenarios Research Articles

Process innovations and circular strategies for closing the water loop in a process industry

By implementing advanced wastewater treatment technologies coupled with digital tools, high-quality water is produced to be reused within the industry, enhancing process efficiency and closing loops. This paper investigates the impact of three innovation tools (process, circular and digital) in a Solvay chemical plant. Four technologies of the wastewater treatment plant “WAPEREUSE” were deployed, predicting their performance by process modelling and simulation in the PSM Tool. The environmental impact was assessed using Life Cycle Assessment and compared to the impact of the current industrial effluent discharge. The circularity level was assessed through three alternative closed-loop scenarios: (1) conventional treatment and discharge to sea (baseline), (2) conventional and advanced treatment by WAPEREUSE and discharge to sea, (3) conventional and advanced treatment by WAPEREUSE and industrial water reuse through cross-sectorial symbiotic network, where effluents are exchanged among the process industry, municipality and a water utility. Scenario 1 has the lowest pollutants’ removal efficiency with environmental footprint of 0.93 mPt/m3. WAPEREUSE technologies decreased COD by 98.3%, TOC by 91.4% and nitrates by 94.5%. Scenario 2 had environmental footprint of 1.12 mPt/m3. The cross-sectorial symbiotic network on the industrial value chain resulted in higher industrial circularity and sustainability level, avoiding effluents discharge. Scenario 3 is selected as the best option with 0.72 mPt per m3, reducing the environmental footprint by 21% and 36% compared to Scenarios 1 and 2, respectively.

Generisch-Net: A Generic Deep Model for Analyzing Human Motion with Wearable Sensors in the Internet of Health Things.

The Internet of Health Things (IoHT) is a broader version of the Internet of Things. The main goal is to intervene autonomously from geographically diverse regions and provide low-cost preventative or active healthcare treatments. Smart wearable IMUs for human motion analysis have proven to provide valuable insights into a person's psychological state, activities of daily living, identification/re-identification through gait signatures, etc. The existing literature, however, focuses on specificity i.e., problem-specific deep models. This work presents a generic BiGRU-CNN deep model that can predict the emotional state of a person, classify the activities of daily living, and re-identify a person in a closed-loop scenario. For training and validation, we have employed publicly available and closed-access datasets. The data were collected with wearable inertial measurement units mounted non-invasively on the bodies of the subjects. Our findings demonstrate that the generic model achieves an impressive accuracy of 96.97% in classifying activities of daily living. Additionally, it re-identifies individuals in closed-loop scenarios with an accuracy of 93.71% and estimates emotional states with an accuracy of 78.20%. This study represents a significant effort towards developing a versatile deep-learning model for human motion analysis using wearable IMUs, demonstrating promising results across multiple applications.

Combining dynamic material flow analysis and life cycle assessment to evaluate environmental benefits of recycling – A case study for direct and hydrometallurgical closed-loop recycling of electric vehicle battery systems

We conduct a life cycle assessment (LCA) for two recycling processes, a hydrometallurgical and a direct recycling route. Both show ecological benefits compared to production with virgin material (between 2.76–4.55 kg CO2e/ kg battery for NMC111 and NMC811 less greenhouse gas emissions). In contrast to previous works, we combine the LCA results with a dynamic material flow model. This allows the evaluation of the influence on ecological benefits of admixture limits for directly recycled cathode material in a closed-loop recycling system over a time in which the newly produced battery systems and the amount of end-of-life traction batteries grows. We show that for such a closed-loop recycling system, the choice of different allocation methods, namely cut-off or avoided burden approach, may lead to significantly varying results of up to 85% in ecological benefits. We further conclude that combining production with both recycling routes can achieve the lowest greenhouse gas emissions for our closed-loop scenarios.

LCA and LCC of a chemical recycling process of waste CF-thermoset composites for the production of novel CF-thermoplastic composites. Open loop and closed loop scenarios

The case study presented in this paper is a follow up of a topic already examined in previous studies relating the life cycle assessment (LCA) of a chemical treatment process used to recycle a specific type of carbon fiber (CF) reinforced thermoset composite. In the present study the LCA is coupled with the life cycle cost (LCC) analysis for the economic assessment. Furthermore, the research sought to specify the best available technology for the reuse of the materials recovered through the chemical recycling process. The new LCA results are more reliable and more current than the scenario presented in the previous LCA studies. In the previous scenario the possibility to recover long carbon fibers “ready to use” was considered. This scenario, even if under investigation by the recycling company, is still not possible for technological limitations as the fibers recovered after the chemical process require further treatments before being used in thermoset composite. Consequently, a more feasible technology was investigated and, according to our laboratory research results, one practical way to recycle the CF-thermoset composites is to shred them before the chemical treatment in order to recover shredded CFs and epoxy thermoplastic from cleavable thermosets. These materials can be easily compounded together to manufacture a CF-thermoplastic composite through injection moulding as we demonstrated herein through some laboratory experiments. The LCA and LCC were accounted for the recycling process via solvolysis up to the recovery phase of the epoxy-thermoplastic resin and the short carbon fibers. The paper presents laboratory test results of the remanufacture of the two reclaimed materials for the production of a thermoplastic CF-composite.

Closed-Loop Deep Learning: Generating Forward Models With Backpropagation.

A reflex is a simple closed-loop control approach that tries to minimize an error but fails to do so because it will always react too late. An adaptive algorithm can use this error to learn a forward model with the help of predictive cues. For example, a driver learns to improve steering by looking ahead to avoid steering in the last minute. In order to process complex cues such as the road ahead, deep learning is a natural choice. However, this is usually achieved only indirectly by employing deep reinforcement learning having a discrete state space. Here, we show how this can be directly achieved by embedding deep learning into a closed-loop system and preserving its continuous processing. We show in z-space specifically how error backpropagation can be achieved and in general how gradient-based approaches can be analyzed in such closed-loop scenarios. The performance of this learning paradigm is demonstrated using a line follower in simulation and on a real robot that shows very fast and continuous learning.

Bilinear Control for Three-Phase Microgrids: A Proportional-Integral Passivity-Based Design

A bilinear PI control based on passivity theory for the adequate integration of distributed energy resources (DERs) in ac microgrids is presented in this paper. DERs are integrated into the grid by voltage source converters (VSC), the most common and suitable technology for this type of application. The proposed control guarantees asymptotically stable operation for the dynamical system under closed-loop operating scenarios via Hamiltonian and Lyapunov formulations. ZP load models and π-model of the transmission lines are considered in the stability analysis of the microgrid. Conventional PI control is also implemented for comparative purposes. Simulation results in Matlab/Simulink demonstrate the effectiveness and stability of the proposed control’s performance in a radial microgrid composed of a photovoltaic generator, a supercapacitor energy storage (SCES) system and unbalanced loads.

Method to generate a large cohort in-silico for type 1 diabetes

Background and objective: In the last decade, several technological solutions have been proposed as artificial pancreas systems able to treat type 1 diabetes; most often they are built based on a control algorithm that needs to be validated before it is used with real patients. Control algorithms are usually tested with simulation tools that integrate mathematical models related mainly to the glucose-insulin dynamics, but other variables can be considered as well. In general, the simulators have a limited set of subjects. The main goal of this paper is to propose a new computational method to increase the number of virtual subjects, with physiological characteristics, included in the original mathematical models. Methods: A subject is defined by a set of parameters given by a mathematical model. From the available reduced number of subjects in the model, the covariance of each parameter of every subject is obtained to establish a mathematical relationship. Then, new sets of parameters are calculated using linear regression methods; this generates larger cohorts, which allows for testing insulin therapies in open-loop or closed-loop scenarios. The new method proposed here increases the number of subjects in a virtual cohort using two versions of Hovorka’s mathematical model. Results:Two covariant cohorts are obtained with linear regression. Both cohorts are clustered to avoid overlapping in the glucose-insulin dynamics and are compared in terms of their qualitative and quantitative behaviours in the normoglycemic range. As a result, there have been generated two larger cohorts (256 subjects) than the original population, which contributes to improving the variability in in-silico tests. In addition, for analysing the characteristics of the covariant generation method, two random cohorts have been generated, where the parameters are obtained individually and independently from each other, exhibiting only distribution limitations so that these cohorts do not have physiological subjects. Conclusions: The proposed methodology has enabled the generation of a large cohort of 256 subjects, with different characteristics that are plausible in the T1DM population, significantly increasing the number of available subjects in existing mathematical models. The proposed methodology does not limit the number of subjects that can be generated and thus, it can be used to increase the number of cohorts provided by other mathematical models in diabetes, or even other scientific problems.

Aeration control in membrane bioreactor for sustainable environmental footprint

In this study different scenarios were scrutinized to minimize the energy consumption of a membrane bioreactor system for wastewater treatment. Open-loop and closed-loop scenarios were investigated by two-step cascade control strategies based on dissolved oxygen, ammonia and nitrite concentrations. An integrated MBR model which includes also the greenhouse gas formation/emission processes was applied. A substantial energy consumption reduction was obtained for the closed-loop scenarios (32% for Scenario 1 and 82% for Scenario 2). The air flow control based on both ammonia and nitrite concentrations within the aerobic reactor (Scenario 2) provided excellent results in terms of reduction of operating cost reduction (64%), direct (10%) and indirect (81%) emissions.

Optical Spatial Modulation for FSO IM/DD Communications With Photon-Counting Receivers: Performance Analysis, Transmit Diversity Order and Aperture Selection

This paper investigates two pulse-based Optical Spatial Modulation (OSM) schemes as cost-efficient solutions for multi-aperture Free-Space Optical (FSO) communications with Intensity-Modulation and Direct-Detection (IM/DD). Namely, we consider Optical Space Shift Keying (OSSK) where information is encoded in the index of the pulsed optical source and Spatial Pulse Position Modulation (SPPM) where additional bits determine the position of the transmitted optical pulse resulting in higher transmission rates. A performance analysis is carried out over gamma-gamma channels with the exact Poisson photon-counting detection model. Exact Symbol Error Probability (SEP) expressions, simple upper bounds and the achievable transmit diversity orders are derived for both the open-loop and closed-loop scenarios. Based on the presented performance analysis, a transmit aperture selection scheme capable of maximizing the transmit diversity order is proposed for OSSK and SPPM in the closed-loop case. Results show that for open-loop OSSK, open-loop SPPM and closed-loop OSSK, the transmit diversity order does not depend on the severity of scintillation unlike the closed-loop SPPM case.

Transmit Signal Designs for Spatial Modulation With Analog Phase Shifters

In this paper, we study transmit codebook designs for spatial modulation with analog phase shifters. The proposed spatial modulation with analog phase shifters can send more spatial symbols than conventional spatial modulation, while reserving the low complexity of single RF-chain MIMO structure. The main idea is to transmit $N_{t}$ different phase-shifted copies of a digitally modulated signal through $N_{t}$ transmit antennas. In each time slot, the transmitted information bits are divided into two groups. The first group of the bits is mapped to the digitally modulated signal symbol. The second group of the bits is mapped to the spatial symbol, which determines the phase shift of each antenna. The transmit signal designs are carried out in open loop and closed loop scenarios, respectively. In open loop scenario, the transmit codebook is designed in two steps, i.e., generate the optimal spatial codebook according to Grassmannian line packing criterion, and find the optimal tradeoff between the cardinality of spatial codebook and the modulation order of signal symbol. In the closed loop scenario, the transmit codebook is designed according to the structure of Huffman tree. Extensive simulation results are given to validate the effectiveness of the proposed scheme in open loop scenario and close loop scenario, respectively.

Time-based disassembly method: how to assess the best disassembly sequence and time of target components in complex products

Circular economy (CE) is a new business model that is pressing manufacturing companies to think about closed loop scenarios for materials and products. Design for End-of-Life (DfEoL) and Design for Disassembly (DfD) are key enabling methods for the effective application of this model. The paper presents a time-based method for the calculation of disassembly sequences, adopting basic theories and techniques in this topic and integrating new concepts for the assessment of the disassembly time. The method consists of five steps and starts from the documentations (e.g., CAD model) generally available early in the product development process. The first three steps encompass the product analysis by including (i) the definition of target components from the general assembly, (ii) the analyses of the virtual model, and (iii) the assessment of the so-called level matrix, which is based on the concept of disassembly levels and liaisons characterization among components. The last two steps allow for the assessment of the time-based disassembly sequence by including (iv) the analysis of feasible sequences and (v) the generation of the best disassembly sequence for target components. The method mainly overcomes two issues highlighted in the literature regarding the reliability of the disassemblability analysis using a time-based approach and the quality of results accounting for the real condition of the product at the time of disassembly. The calculation of the effective disassembly time is grounded on a specific repository developed to gather knowledge about the disassembly tasks and related disassembly time. This is the main contribution and novelty of the proposed approach. By using the proposed method, different target components of a washing machine are analysed with the aim of demonstrating the robustness of the method and its consistency in the estimation of disassembly time. A maximum deviation of 10% between the estimated and measured disassembly times is noticed.

Continuous Glucose Monitoring Enables the Detection of Losses in Infusion Set Actuation (LISAs).

Reliable continuous glucose monitoring (CGM) enables a variety of advanced technology for the treatment of type 1 diabetes. In addition to artificial pancreas algorithms that use CGM to automate continuous subcutaneous insulin infusion (CSII), CGM can also inform fault detection algorithms that alert patients to problems in CGM or CSII. Losses in infusion set actuation (LISAs) can adversely affect clinical outcomes, resulting in hyperglycemia due to impaired insulin delivery. Prolonged hyperglycemia may lead to diabetic ketoacidosis—a serious metabolic complication in type 1 diabetes. Therefore, an algorithm for the detection of LISAs based on CGM and CSII signals was developed to improve patient safety. The LISA detection algorithm is trained retrospectively on data from 62 infusion set insertions from 20 patients. The algorithm collects glucose and insulin data, and computes relevant fault metrics over two different sliding windows; an alarm sounds when these fault metrics are exceeded. With the chosen algorithm parameters, the LISA detection strategy achieved a sensitivity of 71.8% and issued 0.28 false positives per day on the training data. Validation on two independent data sets confirmed that similar performance is seen on data that was not used for training. The developed algorithm is able to effectively alert patients to possible infusion set failures in open-loop scenarios, with limited evidence of its extension to closed-loop scenarios.

A design for EoL approach and metrics to favour closed-loop scenarios for products

Recently, environmentally conscious design and extended producer responsibility have become key aspects for companies that need to develop products that are sustainable along their whole life cycle. Design for End of Life (EoL) is a strategy that aims to reduce landfill waste through the implementation of closed-loop product life cycles. It is important to consider disassembly and EoL scenario management as early as the design phase. For these reasons, this paper presents an approach to help designers in the evaluation and subsequent improvement in product EoL performance. The method is based on four innovative EoL indices that compare different EoL scenarios for each product component. In this way, the designer can modify the product structure or the liaisons to maximise the reuse and remanufacture of components as well as material recycling. The presented case studies confirm the validity of the approach in helping designers during the redesign phase of goods and products to reduce the quantity of materials and industrial wastes sent to landfill.

Hardware-in-the-loop environment for verification of a small satellite's on-board software

Hardware-in-the-loop test beds are applied in industrial satellite development to verify on-board software and to simulate operational scenarios. Spacecraft attitude sensors are simulated by models, which eliminate the need to stimulate them for closed loop scenarios. Similarly, attitude actuators are simulated including actuation interaction with spacecraft dynamics behavior. This approach leads to an enormous reduction in a spacecraft's verification time. Small satellites developed by organizations like AMSAT or by universities are even more limited with respect to available staff and thus even more constrained. As a consequence, there is a need to implement a comparable approach for a hardware-in-the-loop simulation environment at lower cost than in industrial development. The University of Stuttgart has developed and verified a hardware-in-the-loop system test bed for a small satellite's on-board computer while maintaining compliance to industrial standards. Further cost reduction was achieved by applying an industrial system simulation kernel, additional open-source software, the voluntary participation of students, and cooperation with the industry. The system simulation environment connected to the on-board computer was verified by comparing its results with dedicated simulation tools of several disciplines. The latency of signal transfers between the on-board software and the simulator in closed loop operation was determined and analyzed with respect to compliance to control loops and simulation step sizes. All results have been proven to be satisfactory for application in university satellite development and are presented in this publication. This setup is now used in the frame of the on-board software verification for the Flying Laptop satellite.

Coherent Video Simulation of PD Seeker Combat with Towed Decoy Interference under Triangular Situation

Triangle situation is a prerequisite for the effective implementation of the towed decoy interference when combat aircraft faced with missile, which described the relative positional relationship between combat aircraft, towed decoy, and missile. However, it has been a lack of mathematical modeling, signal-level closed-loop simulation and typical scenarios that combine the use of tactics and interference effects assessment. From the perspective of how to maximize the defensive side of the performance of air defense weapon system is also an urgent need to solve the problem. On the basis of the establishment of PD seeker coherent video simulation model, by studying towed decoy signals, tactical choice, constructed loop simulation analysis to complete the process of analysis of the confrontation between the triangular situation, the relevant factors effect are quantitative assessment and gives several useful suggestions.

An Approach to Analytically Evaluate the Product Disassemblability during the Design Process

In order to favor the implementation of closed-loop scenarios at the product End of Life (EoL), it is essential to consider the disassembly phase during the design process. In this context, the paper presents a design for disassembly approach to quantitatively estimate the product disassemblability. The methodology is based on a knowledge database about liaisons, which have been classified and characterized with different properties, in order to take into account the liaison specificity and real conditions in the moment of the disassembly. Starting from the product structure and liaisons between components, the methodology allows to analytically calculate the disassembly time and cost of components/sub-assemblies. The case study (combination oven) demonstrates the usefulness of the proposed approach in identifying the product criticalities which is necessary to consider during the redesign phase in order to improve the product disassemblability performances.

Bit error rate minimising pilot symbol arrangement in closed-loop orthogonal frequency division multiplexing systems

The use of a feedback link in wireless orthogonal frequency division multiplexing (OFDM) systems is analysed. Although open-loop scenarios have been rigorously investigated in the literature, closed-loop scenarios, in which there is a feedback link from a strong to a weak user, have not been thoroughly studied. The study mainly focus on the recently proposed dynamic pilot symbol arrangement strategy. It was shown in a recent paper that for coherent OFDM transmission, this strategy is capable of delivering substantial gains in the performance. Pilot symbols are used to sample channel behaviour so that data symbols can be decoded correctly. However, these pilots do not need to be arranged so as to estimate the channel in the best possible way. In this work, the authors propose a pilot symbol arrangement strategy that minimises the bit error rate, we analyse the solution in detail and propose a low complexity search that maintains most of the quality of an exhaustive search. This low complexity search makes the pilot symbol method viable for medium to large-scale OFDM systems. The authors also analyse the use of a Wiener filter for channel estimation combined with the dynamic pilot symbol strategy and show that it delivers good gains in comparison to a simple maximum likelihood channel estimate.

Multi-Fractal Characteristics of Mobile Node’s Traffic in Wireless Mesh Network with AODV and DSDV Routing Protocols

The analysis of traffic characteristics can be used for performance evaluation, design and implementation of routing protocols in WMNs (Wireless Mesh Networks). Higher bursty traffic will cause larger queue size, which means more dropping packets, and thus affects other metrics. Because burstiness can be modeled by multi-fractal characteristics effectively, multi-fractal characteristics of mobile node's traffic in WMNs are analyzed with typical proactive and reactive routing protocols, which are DSDV (Destination Sequenced Distance Vector) and AODV (Ad hoc On-demand Distance Vector), respectively. Three types of traffic models are used to generate traffic at application level, which corresponding to open-loop and closed-loop scenarios. With different configurations, the probability distribution of inter-arrival time and multi-fractal characteristics of traffic at mobile node and gateway are analyzed with DSDV and AODV protocols. Results show that inter-arrival time with AODV and DSDV protocols possesses heavy-tailed property. And traffic with DSDV protocol exhibits more multi-fractal characteristics than that with AODV protocol, which can explain the higher routing performance of AODV.

Tire Dynamic Deflection and Its Impact on Vehicle Longitudinal Dynamics and Control

Vehicle longitudinal dynamics are shaped by tire characteristics. A number of empirical tire models have been proposed to explain longitudinal tire behaviors. These models typically explain the static tire behaviors and overlook the behaviors during transients. As a result, they often do not reflect the dynamic interactions between the tire and the vehicle under operational environments, most noticeably, the longitudinal overshoots and oscillations that occur immediately after a vehicle is stopped with hard braking. This paper proposes a dynamic-deflection tire (DDT) model that not only specifies the known longitudinal tire characteristics but also captures the dominant tire transient properties. When incorporating this DDT model into a conventional vehicle longitudinal model, these often-ignored tire-vehicle structure modes can be predicted accurately. The resultant model shows that the tire transient characteristics do impact ride comfort and affect longitudinal control designs at low vehicle speeds. A passenger car was tested under both open-loop and closed-loop scenarios, and the experimental results verified the model predictions.

Environmental improvements in the metal finishing industry in Australasia

Metal finishing, as an industry, has had a vexed history with the environment and regulatory authorities over many decades throughout the world. Over the past 20 years, this situation has been vastly improved in some developed countries. This paper will examine the industry's recent progress in Australasia and highlight specific issues including new technologies adopted, research projects undertaken, responses to Government legislation and education. Many toxic chemicals have been replaced, recycled in closed loop scenarios and prevented from entering the environment via the atmosphere, water ways or landfilling. This paper is written as a qualitative industry summary rather than an academic study. It is meant to highlight the major changes that have occurred and the reasons why, rather than present documented and detailed evidence. The author has drawn on his 35 years experience in the industry as well as many experienced colleagues from around the world. Although the geographic scope is Australasia, many comments emanate from the state of Victoria because it is still the manufacturing base, especially in relation to the auto industry that has affected the changes to a large degree.