Common Control Strategies Research Articles

LSTM-Based Wastewater Treatment Plants Operation Strategies for Effluent Quality Improvement

Wastewater Treatment Plants (WWTPs) are facilities devoted to managing and reducing the pollutant concentrations present in the urban residual waters. Some of them consist in nitrogen and phosphorus derived products which are harmful for the environment. Consequently, certain constraints are applied to pollutant concentrations in order to make sure that treated waters comply with the established regulations. In that sense, efforts have been applied to the development of control strategies that help in the pollutant reduction tasks. Furthermore, the appearance of Artificial Neural Networks (ANNs) has encouraged the adoption of predictive control strategies. In such a fashion, this work is mainly focused on the adoption and development of them to actuate over the pollutant concentrations only when predictions of effluents determine that violations will be produced. In that manner, the overall WWTP's operational costs can be reduced. Predictions are generated by means of an ANN-based Soft-Sensor which adopts Long-Short Term Memory cells to predict effluent pollutant levels. These are the ammonium (S NH,e ) and the total nitrogen (S Ntot,e ) which are predicted considering influent parameters such as the ammonium concentration at the entrance of the WWTP reactor tanks (S NH,po ), the reactors' input flow rate (Q po ), the WWTP recirculation rate (Q a ) and the environmental temperature (T as ). Moreover, this work presents a new multi-objective control scenario which consists in a unique control structure performing the reduction of S NH,e and S Ntot,e concentrations simultaneously. Performance of this new control approach is contrasted with other strategies to determine the improvement provided by the ANN-based Soft-Sensor as well as by the fact of being controlling two pollutants at the same time. Results show that some brief and small violations are still produced. Nevertheless, an improvement in the WWTPs performance w.r.t. the most common control strategies around 96.58% and 98.31% is achieved for S NH,e and S Ntot,e , respectively.

Topologies and Control Schemes of Bidirectional DC–DC Power Converters: An Overview

Bidirectional DC-DC power converters are increasingly employed in diverse applications whereby power flow in both forward and reverse directions are required. These include but not limited to energy storage systems, uninterruptable power supplies, electric vehicles, and renewable energy systems, to name a few. This paper aims to review these converters from the point of view of topology as well as control schemes. From the point of view of topology, these converters are divided into two main categories, namely non-isolated and isolated configurations. Each category is divided into eight groups along with their respective schematics and a table of summary. Furthermore, the common control schemes and switching strategies for these converters are also reviewed. Some of the control schemes are typically applied to all DC-DC power converters such as PID, sliding mode, fuzzy, model predictive, digital control, etc. In this context, it should be noted that some switching strategies were designed specifically for isolated bidirectional DC-DC converters in order to improve their performance such as single phase shift, dual phase shift, triple phase shift, etc. The features of each topology and control scheme along with their typical applications are discussed, in order to provide a ground of comparison for realizing new configurations or finding the appropriate converter for the specific application.

Recent advances of light-driven micro/nanomotors: toward powerful thrust and precise control

Abstract In the past two decades, micro/nanomotor is emerging as a critical domain of nanoscale research. Light-driven micro/nanomotors have gained a wealth of attention from the academics because of their potential applications in various fields such as environment remediation, biomedical field and cargo delivery at microscale. In order to perform some more challenging and complex tasks, higher actuation force and more precise control are both indispensable for light-driven micro/nanomotors. In this review, we discussed about three major factors: actuation mechanism, structure of micro/nanomotors and the wavelength of light irradiation, to find out how to gain a higher actuation force and propel the motor in a relatively high speed under light irradiation. Besides, some common control strategies of light-driven micro/nanomotors are presented in details with the advantages and disadvantages of each control mechanism, which will help lead to a convenient and precise control. Finally, the future development approaches toward powerful thrust and precise control are discussed for light-driven micro/nanomotors.

Global fixed-time stabilization for a class of switched nonlinear systems with general powers and its application

This paper investigates the problem of global fixed-time stabilization for a class of uncertain switched nonlinear systems with the general powers, namely, the powers of the considered systems can be different odd rational numbers, even rational numbers or both odd and even rational numbers. By skillfully using the common Lyapunov function method and the adding a power integrator technique, a common state feedback control strategy is developed. It is proved that the proposed controller can guarantee that the state of the resulting closed-loop system converges to zero for any given fixed time under arbitrary switchings. Simulation results of the liquid-level system are provided to show the effectiveness of the proposed method.

Investigation of characteristics of residents in RCHEs associated with MRSA colonization after implementation of infection control training program

Background: Residential care homes for the elderly (RCHEs) are considered potential reservoirs for transmission of Methicillin-resistant Staphylococcus aureus (MRSA). Infection control strategies have been introduced in RCHEs to curb the spread of MRSA. However, the effectiveness of these strategies in reducing MRSA is questionable. MRSA has remained prevalent in economically well-developed regions such as UK and the US despite the implementation of multiple intervention programs. We aim to investigate the characteristics of residents associated with MRSA colonization after implementation of common infection control strategies. Methods & Materials: Residents from selected RCHEs in Kwai Tsing and Tsuen Wan district in New Territories West, Hong Kong were recruited from March 2011 to April 2012. They were interviewed about their health condition and nasal specimens for MRSA screening twice in the study period, with 2-13 months apart. Additional wound specimens were also collected if wounds were identified. Infection control intervention was represented by healthcare staff training and education in the study RCHEs between two screening tests. We defined subjects as being colonized with MRSA if either nasal or wound specimen was tested positive. A multivariable random-effect regression model on follow-up MRSA colonization status was applied. Results: A total of 1832 residents from 32 RCHEs were recruited. The overall point prevalence of MRSA colonisation during the follow-up (after implementation of the training program) was 14.5%(265/1832). Upon adjusting for age, the model which best describes the association between follow-up MRSA colonization and health condition of residents includes the following characteristics: Low mobility indicated by Barthel Index 50 or below (adjusted OR = 1.79;1.23,2.60), presence of skin conditions (adjusted OR = 7.72;4.15,14.36), use of medical device (adjusted OR = 2.25;1.55, 3.24) and presence of MRSA at baseline (OR = 5.23;3.81,7.19). Conclusion: We identified a strong association between health conditions of residents and MRSA colonization. MRSA colonization among residents with low mobility suggested that the service setting and environmental contamination may possibly be sources of MRSA transmission. Device care should be a crucial component in the strategic plan, as shown by the association of colonisation with the use of the medical device. Our findings highlighted the importance of the evaluation of intervention strategies for informing infection control policies.

Techno-economic assessment of surrogate-based real-time control and monitoring of secondary effluent ozonation at pilot scale

During secondary effluent ozonation, real-time control of the ozone dose based on the water quality is essential to minimize operational costs and by-product formation (i.e. two of the main hurdles hindering a fast implementation of the technology). In this pilot-scale study, the ozone dose was controlled via online UV absorbance (UVA254) measurements. Only one sensor was used although a ΔUVA254-based control strategy was applied. The practical implications of online spectral sensors and the effect of effluent dynamics in terms of load (i.e. Dissolved Organic Carbon or DOC concentration) and composition (i.e. reactivity) was studied in relation to the applied control strategies. The one sensor approach – presented for the first time to the best of the authors’ knowledge – reduced the negative impact of sensor fouling. The use of manual and ultrasonic cleaning is recommended as it results in significantly less fouling (i.e. a factor of 6 difference). Additionally, the variable effluent reactivity showed to be more influential than the effluent load in determining the ozone dose. The use of ΔUVA254 ensured the supply of the required ozone doses during varying water quality and weather conditions, and at lower operational costs than more common control strategies (up to 22% of savings). Flow or load proportional strategies were not able to cope with the dynamic ozone demand of the effluent. However, the required additional response time of the ΔUVA254-strategy might be a disadvantage and could be tackled using hybrid control approaches including load-based dosing (i.e. O3:DOC ratio based) and the use of a combined feedback-feedforward system.

Research on Regenerative Braking Combined Control Method for ESP of Pure Electric Vehicles

Through the analysis of the regenerative braking system of pure electric vehicles, a series type of regenerative braking control strategy based on a full decoupling braking system is proposed from the perspective of vehicle braking dynamics. The main factors influencing the regenerative braking control of pure electric vehicles are analyzed. Based on this, several common braking control strategies of regenerative systems are elaborated and analyzed according to the main influencing factors. Through the comparative analysis of the braking control strategies of the regenerative system, it is found that the parallel linkage brake control strategy can better meet the safe operation of pure electric vehicles. Compared with the original control strategy, the regenerative braking combined control strategy can improve the energy recovery rate when the vehicle is braking at high braking intensity and it can also improve the failure safety of the electronic control system when the vehicle is braking at high speed or at medium and high intensity.

A simple movement based control approach to ease the control of a myoelectric elbow prosthetics in transhumeral amputees

Common myoelectric control strategy remains complex to use and produce unnatural gestures since it does not allow simultaneous movements of several joints. This is especially an issue for the transhumeral amputees who can use an active elbow in addition to active prosthetic wrist and hand. Since most transhumeral amputees have a mobile residual limb, an interesting approach aims at utilizing this mobility to control the elbow. We thus developed a simple electronic device relying on an inertial measurement unit, that can be interfaced with existing commercial myoelectric elbows and which convert chosen displacements of the residual limb into control signals, offering an intuitive way of controlling an active elbow prosthesis whilst allowing a simultaneous myoelectric control of the wrist and hand. We performed an experiment with one transhumeral amputee wearing his myoelectric prosthetic (active elbow, wrist and hand) who was asked to grasp and transfer different objects several times while being recorded with a motion capture system. Theses task were performed twice: with a conventional full myoelectric control and with the proposed movement based control. Several metrics (position error, time, smoothness, along with body compensatory strategies) were used to quantify the performances obtained with these two modes. Analyses showed that the participant was able to perform the tasks in both condition, but that the movement based control approach allowed a reduction in task time and in exhibited body compensatory strategies, by offering an easier access to adjustments of the elbow posture compared to the full myoelectric control approach. This work illustrates the potential of using residual limb mobility in the control of prosthetics, to make it more natural and intuitive, and how this can have an indirect but positive impact on the whole body compensatory strategies exhibited by amputated subjects.

Exciting Chaotic and Quasi-Periodic Oscillations in a Multicircuit Oscillator with a Common Control Scheme

We propose a multicircuit oscillator with a common control scheme driving self-sustained oscillations in each circuit, which can exhibit quasi-periodic and chaotic oscillations. The proposed oscillator was investigated by experimental and numerical methods that confirmed the possibility of exciting multifrequency quasi-periodic, chaotic, and hyperchaotic oscillations with several positive Lyapunov exponents.

Finite time control of switched stochastic nonlinear systems

This manuscript studies a finite-time tracking problem of switched stochastic nonlinear uncertain systems. By utilizing a comparison theorem and a mean value theorem of integrals, a significant finite-time stability criterion for stochastic nonlinear systems is first set up. Then, combining a common Lyapunov function method and an adaptive fuzzy control approach, a novel common control scheme is formed. Under the proposed adaptive mechanism, the system performance is achieved in finite-time. By using the universal approximation ability, the nonlinear functions and their bounding functions may be completely unknown to the designer, which is more in line with reality than the existing finite-time researches for stochastic nonlinear systems.

Effects of Entomopathogenic fungi and Bacillus thuringiensis‐based biopesticides on Spoladea recurvalis (Lepidoptera: Crambidae)

AbstractSpoladea recurvalis (Fabricius) is one of the most devastating pests of amaranths causing severe yield losses of 60%–100% to the crop. Unfortunately use of chemical pesticides is the most common control strategy that vegetable farmers rely on to control the pest. However, it is not effective and harmful to environmental and human health. Aiming to provide more environmentally friendly alternatives, this study evaluated the effects of various entomopathogenic fungal isolates and commercial based Bacillus thuringiensis Subsp. kurstaki product Halt®, on the pest. Twenty‐four entomopathogenic fungal (EPF) isolates from three genera (14 Metarhizium anisopliae, 9 Beauveria bassiana and 1 lsaria fumosorosea) were screened in the laboratory to assess their pathogenicity against second instar larvae of S. recurvalis. Only M. anisopliae ICIPE 30 reached a moderate threshold, causing 58.3% larval mortality. All the 11 isolates (8 M. anisopliae, 2 B. bassiana and 1 l. fumosorosea) tested against adult S. recurvalis were pathogenic, with M. anisopliae ICIPE 30 and B. bassiana ICIPE 725 causing the highest mortality of 92% and 83%, respectively. Metarhizium anisopliae ICIPE 30 had the shortest LT50 value of 4.8 days. Bacillus thuringiensis Subsp. kurstaki product Halt® caused <50% mortality on S. recurvalis larvae. A consecutive application of M. anisopliae ICIPE 30 and Bt did not cause a significant increase in larval mortality compared to separate applications of both products. Results of this study suggest that M. anisopliae ICIPE 30 was the most potent candidate and could be used in an autodissemination approach for management of adult S. recurvalis.

West African Cattle Farmers' Perception of Tick-Borne Diseases.

Worldwide, cattle production is struggling to face the negative impacts caused by ticks and Rhipicephalus (Boophilus) microplus is one of the most harmful ticks for livestock. Most of the people in West Africa depend on cattle farming and subsistence agriculture. The presence of ticks on cattle is a major problem faced by smallholder farmers who fight for their livelihood. National and regional tick control programs could assist these rural communities in protecting their livelihoods against ticks and tick-borne diseases, but only if they take into account the targeted herders and their perception on cattle management and tick control. This paper aims to provide a better insight in the socio-economic characteristics of Beninese cattle farmers, and their perception on tick burden, as well as to document common tick control strategies. Different tick species and their seasonality are well understood by cattle herders. For tick control, many still use manual tick removal, especially in the north of the country. The high cost of acaricides, the lack of financial means of African farmers, and of the local stockbreeders in particular, limits the use of acaricides in livestock breeding in Benin. While aiming to increase the meat or milk production of their animals, stockbreeders who can afford it sometimes turn to an abusive use of acaricides, which might in time lead to an increase in tick resistance. This study remains one of the rare studies to report extensively on the perceptions of West African cattle herders.

Using genomic data to study insecticide resistance in the house fly, Musca domestica

The house fly, Musca domestica, is a major pest at livestock facilities throughout the world. Insecticides have been the most common control strategy for flies, but many populations have evolved resistance. The speed by which we are able to identify the mutations responsible for resistance has been a major challenge for the development of high throughput resistance monitoring assays as new insecticides are introduced for control. This is particularly true for mutations that cause trans regulation of a gene, which then results in resistance. In this paper we take advantage of the conserved homology of dipteran chromosomes to assign 3069 genes to chromosomes. Of these, 234 were of toxicological interest (CYPs, esterases/hydrolases, glutathione S-transferases (GSTs) and target sites). The chromosomal location of genes known from linkage analysis studies matched the location predicted by homology mapping in ten out of ten cases, indicating a high reliability of our approach. The CYPs, esterases/hydrolases and GSTs were not randomly distributed throughout the genome. They clustered on chromosomes, but the pattern was different between the CYPs, esterases/hydrolases and GSTs. Examples are provided for how the availability of the house fly genome, combined with an ability to assign genes to chromosomes, will help to accelerate research in house flies.

Hybrid Force and Position Control Strategy of Robonaut Performing Object Transfer Task

This paper proposes a coordinated hybrid force/position control strategy of robonaut performing object transfer operation. Firstly, the constraint relationships between robonaut and object are presented. Base on them, the unified dynamic model of the robonaut and object is established to design the hybrid force/position control method. The movement, the internal force and the external constraint force of the object are considered as the control targets of the control system. Finally, a MATLAB simulation of the robonaut performing object transfer task verifies the correctness and effectiveness of the proposed method. The results show that all the targets can be control accurately by using the method proposed in this paper. The presented control method can control both internal and external forces while maintaining control accuracy, which is a common control strategy.

Advances in Powered Ankle-Foot Prostheses.

We present a review of recent developments in powered ankle-foot prostheses (PAFPs), with emphasis on actuation, high- and low-level control strategies, and pneumatic, hydraulic, and electromechanical actuators. A high-level control strategy based on finite-state machines, combined with low-level control that drives the ankle torque, is the most common control strategy. On the other hand, brushless direct-current motors along with an energy storage and release mechanism are commonly used to reduce the overall size of the actuators and increase PAFP autonomy. Most designs have been evaluated experimentally, showing acceptable results in walking velocity and gait symmetry. Future research must focus on reducing weight, increasing energy efficiency, improving gait phase classification and/or intent of motion-prediction algorithms, updating low-level control of torque and position, and developing the ability of the patient to walk on sloped surfaces and negotiate stairs.

Возбуждение хаотических и квазипериодических колебаний в многоконтурном генераторе с общей схемой управления

AbstractWe propose a multicircuit oscillator with a common control scheme driving self-sustained oscillations in each circuit, which can exhibit quasi-periodic and chaotic oscillations. The proposed oscillator was investigated by experimental and numerical methods that confirmed the possibility of exciting multifrequency quasi-periodic, chaotic, and hyperchaotic oscillations with several positive Lyapunov exponents.

Analgesic Effect of Nebulized Versus Intravenous Fentanyl for Pain Relief of Limb Fracture: A Double-Blind Clinical Trial

Background:More than half of the patients attending emergency centers need analgesics. Injectable analgesics are currently the most common pain control strategy, but entail complications. Fentanyl is one of the most commonly used pain-relief opiates available in various forms.Objective:The present study aims to compare analgesic effects of nebulized against intravenous fentanyl for controlling pain due to limb fracture.Method:The present double-blind clinical trial recruited 213 patients presenting with fractured limbs to emergency departments. The first group of patients received 1 micg/kg of intravenous fentanyl citrate from a solution of 50 micg/ml and 5 ml of normal saline in nebulized form (group A), and the second group intravenously received 5 ml of normal saline and 4 micg/kg of 50 micg/ml solution of fentanyl citrate in nebulized form, whose volume reached 5 ml with the addition of normal saline (group B). Then, pain level was frequently measured and compared in the two groups for 20 minutes.Results:The results obtained showed reduced pain level in both the groups. However, point-by-point comparison of pain in the two groups revealed significantly greater pain reduction in intravenous fentanyl group (P<0.001). The need for adjuvant pain relief medication was 8.3% in intravenous fentanyl group and 24% in nebulized fentanyl group, with a significant difference between the two groups (P=0.002).Conclusion:According to the results, although nebulized fentanyl is effective in controlling pain due to limb fracture, it was less effective than intravenous type, and unable to control pain in many cases.

HYGROTHERMAL PERFORMANCE ASSESSMENT OF ICF WALLS WITH DIFFERENT MOISTURE CONTROL STRATEGIES AND WALL DESIGNS

The initial high moisture content of concrete and the low vapor permeability of insulation layers on both sides of the concrete complicate the drying process of Insulated Concrete Forms (ICF). In order to facilitate the moisture transport and enhance the drying process, different moisture control strategies and wall designs can be implemented. The application of an air and vapor barrier is one of the most common moisture control strategies. In this paper, the impact of vapor permeance of an air and vapor barriers on the hygrothermal performance of an ICF wall in three different cold and wet climates is examined using a validated Heat-Air-Moisture transfer model. The hygrothermal performance of an ICF wall assembly with different types of barriers and locations in the wall system for several wall designs is investigated. Results indicate that a smaller thickness of insulation on the outside facilitates removing the moisture towards the outside and installing low permeance air/vapor barrier systems on the outside prohibits drying and drives the moisture to the inside. Our findings also show that with the proper selection of insulation thickness and vapor control strategy moisture-related problems can be avoided.

SEMG-based impedance control for lower-limb rehabilitation robot

Recently, various rehabilitation robots have been developed for therapeutic exercises. Additionally, several control methods have been proposed to control the rehabilitation robots based on user’s motion intention. One of the common control methods used is torque-based impedance control. This paper presents an electromyogram-based robust impedance control for a lower-limb rehabilitation robot using a voltage-based strategy. The proposed control strategy uses surface electromyogram (sEMG) signals in place of force sensors to estimate the exerted force. In addition, the control is based on the voltage control strategy, which differs from the common torque control strategies. For example, unlike the torque-based impedance control, the controller is not dependent on the dynamical models of the patient and the robot. This is particularly important as the dynamic of the patient is both difficult to model precisely and changes during the rehabilitation period. These simplifications results in a significant reduction in calculation time. To illustrate the effectiveness of the control approach, a 1-DOF lower-limb rehabilitation robot is designed. Experimental sEMG-force data are collected and used to train an artificial neural network. Simulation results show that compared with a torque-based control approach, the voltage-based is simpler, less computational and more efficient while it considers the presence of actuators. Finally, we design an adaptive fuzzy system to estimate and compensate the uncertainty in performing the impedance rule. The adaptive fuzzy system has an advantage that does not need new feedback to estimate the uncertainty. The control approach is further verified by stability analysis. Simulation results show the efficiency of the control approach in performing some therapeutic exercises.

Adaptive output feedback tracking control for switched non‐strict‐feedback non‐linear systems with unknown control direction and asymmetric saturation actuators

The problem of adaptive tracking control is studied for a class of switched non-strict-feedback non-linear systems with unknown control direction and asymmetric saturation actuators under arbitrary switchings. The main technical difficulty comes from developing a common adaptive control scheme in the presence of unknown control direction and unknown asymmetric saturation non-linearities. A linear state transformation is exploited to deal with the unknown control coefficients and a Gaussian error function-based smooth model is used to approximate the asymmetric saturation non-linearity. Based on an input-driven observer, a common adaptive output-feedback control strategy containing only one adaptive parameter is developed for such systems via a novel combination of common Lyapunov function method, backstepping technique, variable separation approach and neural network approximation. Under the proposed control scheme, the tracking error converges to an adjustable neighbourhood of the origin. Finally, two illustrative examples are included to verify the effectiveness of the proposed control design.