Uniform Control Research Articles

Uniformly semidiscretized approximation for exact observability and controllability of one-dimensional Euler–Bernoulli beam

In this paper, a spacial semidiscretized finite difference scheme developed in our previous work (Liu and Guo, 2019) is used to approximate exact observability and controllability for Euler–Bernoulli beam control system. The uniform observability inequality is proved by discrete energy multiplier technique. The uniform controllability and uniform boundedness of the discrete controls are also developed. Compared with the existing literature, the proposed approach has achieved potentially the following advantages: (a) It removes the introduction of the numerical viscosity term to achieve uniformity; (b) It can deal with any type of boundary conditions without help of the spectral analysis which is limited only for some special boundary conditions; (c) The proofs of the uniform observability and controllability are simplified significantly with the similar techniques in dealing with the continuous counterpart.

Force uniformity control for large-area roll-to-roll process.

Demand for high throughput manufacturing has recently increased in various fields, such as electronics, photonics, optical devices, and energy. Moreover, flexible electronic devices are indispensable in applications such as touch screens, transparent conductive electrodes, transparent film heaters, organic photovoltaics, organic light-emitting diodes, and battery. For these applications, a large-area roll-to-roll (R2R) process is a promising method for producing with high throughput. However, bending deformation of rollers is unavoidable in a large-scale R2R system, which produces non-uniformity in force distribution during processing and reduces the sample quality. In this study, we propose a new R2R imprinting module to mitigate the deformation by using an additional backup roller to achieve uniform force distribution. From numerical simulations, we found that there exists an optimal imprinting force for each backup roller length to obtain the best uniformity. Experimental results using a large-area pressure sensor verified the effectiveness of the proposed method. Finally, the R2R nanoimprintlithography process showed that the proposed method produces patterns of 100nm width with uniform residual layer thickness, which are distributed across the substrate of 1.2m width.

Micro-range uniformity control of the etching profile in the OLED display mass production referring to the PI-VM model

The high-value process strategy in the organic light emitting diode display manufacturing requires strict etching profile control to obtain the normal performance of the display pixels because of the correlation between the etched structure of the processed pattern and the current–voltage characteristics of the pixels. The critical dimension, etch depth, and sidewall angle area are important management points of the etching profile. Because of two-dimensional continuous characteristics of the display as the numerous arrays of the thin film transistors, the etching profiles should be controlled in the analog way rather than only the fact of spec-in or -out. Therefore, the sheath properties which govern the ion flux-driven etching effect and the polymer passivation characteristics of the sidewall of the etching hole are needed to be tailored spatially even in the micro-range. The embossing structured electrode surface applied for the large area display manufacturing dry etching process causes micro-scale non-uniformity of the sheath and passivation properties, and introduces the process faults. To control this micro-range non-uniformity of the etching profiles, a PI-VM (Plasma Information based Virtual Metrology) model was developed by applying the PI parameters. PI parameters include the information on the sheath potential for electronegative plasmas and the heat transfer properties in the chamber. PI parameterization utilized a big data pool of the optical emission spectroscopy and equipment engineering system data accumulated during the mass production. The developed PI-VM model could predict the fault with 80% accuracy, and analysis of the highly contributing PI parameters to the events could give the way to control the manufacturing.

Interaction between cement clinker constituents and clay minerals and their influence on the strength of cement-based stabilized soft clay

The strength of cement-based stabilized clay is less than that of concrete and mortar and shows a distinct variability owing to the existence of various clay minerals. To better understand the cement–clay reactions and the strength generation, two artificial clays with the unique clay mineral and major strength-producing constituents of cement clinker were investigated via mechanical, compositional, and microstructural analyses. Results show that C3A-stabilized clay gains strength rapidly in the first 3 days, but this favourable tendency vanishes over time. After 90 days of curing, the strength of C3S-stabilized clay is about four times that of the corresponding C3A-stabilized clay, indicating the remarkable long-term stabilization efficiency of C3S. Furthermore, clay minerals primarily draw into strength evolution in the reaction process. Despite that bentonite is more reactive than kaolin as long as the highly alkaline conditions persist, it has a higher probability to flocculate into large aggregates during the mixing process, which may impair the reaction efficiency and even brings adverse stabilization effects, suggesting the importance of uniformity control.

Observer-Based H ∞ Fuzzy Synchronization and Output Tracking Control of Time-Varying Delayed Chaotic Systems

Tracking control for the output using an observer-based H ∞ fuzzy synchronization of time-varying delayed discrete- and continuous-time chaotic systems is proposed in this paper. First, from a practical point of view, the chaotic systems here consider the influence of time-varying delays, disturbances, and immeasurable states. Then, to facilitate a uniform control design approach for both discrete- and continuous-time chaotic systems, the dynamic models along with time-varying delays and disturbances are reformulated using the T-S (Takagi–Sugeno) fuzzy representation. For control design considering immeasurable states, a fuzzy observer achieves master-slave synchronization. Third, combining both a fuzzy observer for state estimation and a controller (solved from generalized kinematic constraints) output tracking can be achieved. To make the design more practical, we also consider differences of antecedent variables between the plant, observer, and controller. Finally, using Lyapunov’s stability approach, the results are sufficient conditions represented as LMIs (linear matrix inequalities). The contributions of the method proposed are threefold: (i) systemic and unified problem formulation of master-slave synchronization and tracking control for both discrete and continuous chaotic systems; (ii) practical consideration of time-varying delay, immeasurable state, different antecedent variables (of plant, observer, and controller), and disturbance in the control problem; and (iii) sufficient conditions from Lyapunov’s stability analysis represented as LMIs which are numerically solvable observer and controller gains from LMIs. We carry out numerical simulations on a chaotic three-dimensional discrete-time system and continuous-time Chua’s circuit. Satisfactory numerical results further show the validity of the theoretical derivations.

Experimental study on active disturbance rejection temperature control of a mechanically pumped two-phase loop

High-heat-flux heat removal is critical for the long-term safety of the high-power electronic device. However, the precise and uniform temperature control of the device is challenging due to various nonlinearities, couplings and disturbances. To this end, active disturbance rejection controller (ADRC), hybrid with an auxiliary feed-forward flow rate controller and an auxiliary subcooling degree controller, is introduced in this paper for the wall temperature control of a microchannel mechanically pumped two-phase cooling loop. First, the optimal flow rate in terms of the heating power is identified to minimize the temperature level and variance. The relative curves between the flow rate and heating power are like character ‘v’ which are used as a feed-forward law for the flow rate regulation. Second, the reference of the sub-cooling degree is determined based on the closed-loop control of the preheater to get a uniform temperature field with least variance. Finally, ADRC is used in the primary loop to control the average wall temperature. The experimental results indicate the efficiency of thermal control for two-phase cooling loop via combination of primary and auxiliary loop. In addition, ADRC performs better in both temperature tracking and disturbance rejection when compared with the conventional PI controller, with superiority in terms of faster tracking and stronger robustness to disturbances and couplings.

Abstract Rotations for Uniform Adaptive Control and Soft Modeling of Mechanical Devices

The model-based controllers generally suffer from the lack of precise dynamic models. Making reliable analytical models can be evaded by soft modeling techniques, while the consequences of modeling imprecisions are tackled by either robust or adaptive techniques. In robotics, the prevailing adaptive techniques are based on Lyapunov’s “direct method” that normally uses special error metrics and adaptation rules containing fragments of the Lyapunov function. The soft models and controllers need massive parallelism and suffer from the curse of dimensionality. A different adaptive approach based on Banach’s fixed point theorem and using special abstract rotations was recently suggested. Similar rotations were suggested to develop particular neural network-like soft models, too. Presently, via integrating these approaches, a uniform adaptive controlling and modeling methodology is suggested with especial emphasis on the effects of the measurement noises. Its applicability is investigated via simulations for a two degree of freedom mechanical system in which one of the generalized coordinates is under control, while the other one belongs to a coupled parasite dynamical system. The results are promising for allowing the development of relatively coarse soft models and a simple adaptive rule that can be implemented in embedded systems.

Co-generation ability investigation of the novel structured PVT heat pump system and its effect on the “Carbon neutral” strategy of Shanghai

A novel structured PVT (photovoltaic-thermal) module was proposed, manufactured, and adopted to form a solar assisted PVT heat pump system to realize high-efficiency co-generation in building sectors. The experiment apparatuses were set and tested to evaluate the thermal, electrical, hydraulic behavior of the proposed PVT module. Moreover, the temperature uniformity control ability of the novel structured PVT module was conducted in comparison with the single PV module. For instance, the operating temperature difference of the PVT module could be controlled within 0.7 °C while it is 0.9 °C of the single PV module. The average experimental electrical and thermal efficiencies are 17.93% and 109.4%, respectively, which show a significant improvement in comprehensive solar energy utilization efficiency compared with other conventional PVT technologies, and this technology would have a positive effect on the “Carbon neutral” strategy of Shanghai. The overall annual CO2 emission for electricity and domestic hot water supplement of the proposed solar assisted PVT heat pump system is 565.8 kgCO2, which is only 11.41% of the traditional supply technology (grid power + electrical water heater). Moreover, a 1 m2 PVT system could fix 3111.6 kgCO2 which is 53.2% higher than that of the PV system after 20 years.

Uniform boundary controllability and homogenization of wave equations

We obtain sharp convergence rates, using Dirichlet correctors, for solutions of wave equations in a bounded domain with rapidly oscillating periodic coefficients. The results are used to prove the exact boundary controllability that is uniform in \varepsilon (the scale of the microstructure) for the projection of solutions to the subspace generated by the eigenfunctions with eigenvalues less than C\varepsilon^{-2/3} .

Performance evaluation of water-repellent combat uniforms using a static manikin and human subjects under a rainfall tower system

The purpose of the present study was to evaluate the water-repellent properties of newly-developed combat uniforms using a rainfall tower system. Two types of water-repellent- combat uniforms with an identical level of water repellency through textile tests (WR_M and WR_T) were compared with an untreated-combat uniform (Control). A static manikin was used to evaluate water-repellent properties in a standing position and eight male subjects participated to test walking effects under artificial rainfall. The results showed that it took to saturate the upper body was longer for WR_T than WR_M and Control in the standing position for both normal and heavy rain conditions (P < 0.05). The lower body in WR_T was rarely wet in the standing position after 60 min, whereas the lower body was partially wet while walking within 30 min. Changes in clothing weight after the rainfall test were 729 ± 21, 256 ± 36 and 137 ± 25 g per trial for Control, WR_M, and WR_T, respectively (P < 0.001). Subjects expressed better tactile, less colder, less heavier, and less humid sensations and less uncomfortable feeling for WR_T than Control or WR_M (P < 0.05), while WR_M was better only for tactile sensation and heaviness than Control (P < 0.05). Ten-time-washes had not impaired the water-repellent properties of WR_M or WR_T. These results indicated that the rainfall tower test is valid to verify water-repellent property of clothing ensemble and suggest a possibility of classifying the water repellency of clothing ensemble into sub-levels of an excellent and a fair class. Further studies on wider range of experimental conditions to validate the current results are required.

Risk-Sensitive Rear-Wheel Steering Control Method Based on the Risk Potential Field

Various driving assistance systems have been developed to reduce the number of automobile accidents. However, the control laws of these assistance systems differ based on each situation, and the discontinuous control command value may be input instantaneously. Therefore, a seamless and unified control law for driving assistance systems that can be used in multiple situations is necessary to realize more versatile autonomous driving. Although studies have been conducted on four-wheel steering that steers the rear wheels, these studies considered the role of the rear wheels only to improve vehicle dynamics and not to contribute to autonomous driving. Therefore, in this study, we define the risk potential field as a uniform control law and propose a rear-wheel steering control system that actively steers the rear wheels to contribute to autonomous driving, depending on the level of the perceived risk in the driving situation. The effectiveness of the proposed method is verified by a double lane change test, which is performed assuming emergency avoidance in simulations, and subject experiments using a driving simulator. The results indicate that actively steering the rear wheels ensures a safer and smoother drive while simultaneously improving the emergency avoidance performance.

Fast reconfiguration of robot swarms with uniform control signals

Fast reconfiguration of robot swarms with uniform control signals

Stationary BGK Models for Chemically Reacting Gas in a Slab

We study the boundary value problem of two stationary BGK-type models - the BGK model for fast chemical reaction and the BGK model for slow chemical reaction - and provide a unified argument to establish the existence and uniqueness of stationary flows of reactive BGK models in a slab. For both models, the main difficulty arises in the uniform control of the reactive parameters from above and below, since, unlike the BGK models for non-reactive gases, the reactive parameters for the reactive BGK models are defined through highly nonlinear relations. To overcome this difficulty, we introduce several nonlinear functionals that capture essential structures of such nonlinear relations such as the monotonicity in specific variables, that enable one to derive necessary estimates for the reactive equilibrium coefficients.

Managing Animal Welfare in Food Governance in Norway and Sweden: Challenges in Implementation and Coordination.

Simple SummaryAnimal welfare is an important issue in society, and having a strong animal welfare legislation is per se important. However, in addition to a strong legislation, it is necessary to create a system that can enforce the legislation and to have a public administration in place in order to achieve a coordinated implementation. Both Norway and Sweden have received some criticism for their coordination of animal welfare control efforts. However, they have reacted to this criticism in different ways. Norway has centralised the coordination, making the Norwegian Food Safety Authority (NFSA) solely responsible for animal welfare control. Sweden, on the other hand, has instead focused on developing better guidelines to be used by the 21 regional County Administration Boards in order to improve uniformity. In this study, we have compared the Norwegian and Swedish ways of coordinating animal welfare control and identified challenges and relevant organisational preconditions for achieving uniform and consistent compliance. The results show that Sweden’s organisation may need more coordination between multiple organisational units, while Norway has better preconditions for achieving uniformity in animal welfare administration. However, in Norway, the safeguards for the rule of law might be an issue, due to NFSA acting as de facto “inspector”, “prosecutor” and “judge”.A key issue in food governance and public administration is achieving coordinated implementation of policies. This study addressed this issue by systematically comparing the governance of animal welfare in Norway and Sweden, using published papers, reports, and legal and other public information, combined with survey and interview data generated in a larger research project (ANIWEL). Governing animal welfare includes a number of issues that are relevant across different sectors and policy areas, such as ethical aspects, choice of legal tools, compliance mechanisms and achieving uniform control. Based on the challenges identified in coordinating animal welfare in Norway and Sweden, relevant organisational preconditions for achieving uniform and consistent compliance were assessed. The results showed that Sweden’s organisation may need more horizontal coordination, since its animal welfare management is divided between multiple organisational units (Swedish Board of Agriculture, National Food Agency and 21 regional County Administration Boards). Coordination in Norway is managed solely by the governmental agency Norwegian Food Safety Authority (NFSA), which has the full responsibility for inspection and control of food safety, animal health, plant health, as well as animal welfare. Thus, Norway has better preconditions than Sweden for achieving uniformity in animal welfare administration. However, in Norway, the safeguards for the rule of law might be an issue, due to NFSA acting as de facto “inspector”, “prosecutor” and “judge”.

Properties of the 90° cylindrical energy analyzer with internal deceleration of the beam in real conditions of operation

To measure plasma potential in toroidal magnetically confined fusion plasma, the Heavy Ion Beam Diagnostic (HIBD) employs of the electrostatic energy analyzer. The 90° cylindrical energy analyzer (CEA) developed for the HIBD on the ISTTOK tokamak due to compactness and multislit operation capability, is characterized by large angular aberrations, if operated in conventional mode. A new operation regime was proposed based on numerical investigations, which demonstrated the efficiency of the 90°CEA operation in reducing angular aberrations via the deceleration of the ion beam inside analyzer, resulting also on an improved energy resolution. In this paper, the properties of the 90 ° CEA featuring with guard rings (GR) to shield the analyzer from the surrounding structures are investigated in the internal deceleration mode (ID-mode) for “centric” and “paracentric” injection geometries. The numerical simulations are conducted using SIMION code. Special attention is paid to uniformity of the beam image on detector plate, which is of importance in ion beam energy measurements by split-plate detector technique. The results confirm coupling of analyzer angle aberration properties with beam deceleration inside analyzer. For both “centric” and “paracentric” entrances the existence of the first-order focus in ID-mode is obtained. However, the first order focus ID-mode of 90°CEA with GR is characterized by heterogeneity of the image for the initially uniform beam, determined by modification of electric field inside analyzer. It is revealed that the energy dispersion of the initially monoenergetic ions due to chromatic-like aberration introduced by analyzer plays a contributive role in the beam image non-uniformity. From the beam energy measurements point of view, it is shown that the energy variation due to this chromatic aberration is of the second order of the analyzer intrinsic resolution. The results show that “centric” entrance in ID-mode is preferable as the image non-uniformity is less pronounced and can be effectively restored by manipulation of entrance slit dimensions and potentials on GR. It is concluded that besides detail preparatory numerical optimization, the beam image shape and uniformity control is essential, which can be realized with the dedicated multiple cell detection.

UNIFORM SMARTPHONE CONTROLLER FOR WEB-BASED VIRTUAL REALITY PURPOSES

This work introduces a uniform smartphone controller interface integrated into LIRKIS G-CVE web-based global collaborative virtual environments. In general, VR controllers provide various kinds of interaction techniques to manipulate virtual objects. Mostly, those aim focus on controlling the virtual context and the interaction with 3D GUI integrated in the virtual environment. With respect to web-based virtual reality, the progress in development of uniform interfaces is raising thanks to emerging web technologies and frameworks with cross-platform support. Although there are many manufacturers of VR controllers, their usage is often limited only for specified display device. Our intention is to cover multiple devices through only one simple controller interface, that is capable to provide a variety of interactions for web-based VR. In this study we proposed Enhanced Smart Client Interface designed for providing fully immersive interaction through smartphones. We performed several experiments focused on user experience and usability under two cloud platforms. Results obtained from experiments performed in our study confirm that utilization of our interface is mostly affected by the server response time. Based on the results this solution is suitable for further development and improvements.

Using P(Pressure)-T(Temperature) Path to Control the Foaming Cell Sizes in Microcellular Injection Molding Process.

Microcellular injection molding technology (MuCell) using supercritical fluid (SCF) as a foaming agent is one of the important green molding solutions for reducing the part weight, saving cycle time, and molding energy, and improving dimensional stability. In view of the environmental issues, the successful application of MuCell is becoming increasingly important. However, the molding process encounters difficulties including the sliver flow marks on the surface and unstable mechanical properties that are caused by the uneven foaming cell sizes within the part. In our previous studies, gas counter-pressure combined with dynamic molding temperature control was observed to be an effective and promising way of improving product quality. In this study, we extend this concept by incorporating additional parameters, such as gas pressure holding time and release time, and taking the mold cooling speed into account to form a P(pressure)-T(temperature) path in the SCF PT diagram. This study demonstrates the successful control of foaming cell size and uniformity in size distribution in microcellular injection molding of polystyrene (PS). A preliminary study in the molding of elastomer thermoplastic polyurethanes (TPU) using the P-T path also shows promising results.

Radial control of plasma uniformity and electron temperature by external plate biasing in a back diffused partially magnetized plasma

The possibility of achieving uniform and controllable plasma distribution remain a fundamental challenge in low pressure plasma discharges, which has numerous applications in plasma technologies. An external object when introduced in a magnetized plasma can significantly alter the spatial plasma distribution. In this paper, the effect of external plate biasing on both axial as well as radial characteristics of an expanding, partially magnetized plasma column, created by hot cathode filament inside a linear plasma device is presented. It is found that by applying a positive potential to a conducting external electrode, placed at a remote location away from the primary discharge region; the back diffused plasma tends to become uniform. The plate biasing also results in an overall increase in electron temperature of the expanding plasma; however, it does not appear to alter the radial plasma characteristics inside the source and the biasing region. A possible mechanism behind observing this effect has been provided.

Cell-Free Massive MIMO: Joint Maximum-Ratio and Zero-Forcing Precoder With Power Control

Cell-free massive multiple-input multiple-output (MIMO) system is a promising architecture for next generation wireless systems by deploying a very large number of distributed access points (APs), which simultaneously serve a smaller number of user equipments (UEs) over the same time-frequency resources. It guarantees uniformly good service at high spectral efficiency with simple linear precoding techniques and max-min power control. In this article, we propose a new joint maximum-ratio and zero-forcing (JMRZF) precoding scheme, where part of APs are combined to perform centralized zero-forcing (ZF), while other APs apply simple maximum-ratio transmission (MRT). Our proposed precoder offers an adaptable trade-off between the spectral efficiency and front-haul signalling overhead. A corresponding AP subset selection scheme is also proposed which is based on large-scale fading coefficients. A closed-form expression for the achievable spectral efficiency of our proposed scheme is derived, which represents a generalized result including both fully distributed MRT and fully centralized ZF cases. Based on this closed-form expression, max-min power control is formulated and solved via the second order cone and first order methods. The former can obtain the global optimal solution, but its computational complexity is very high. On the other hand, the latter technique is sub-optimal, yet, it has very low computational complexity. Hence, it is suitable for large-scale cell-free massive MIMO systems with hundreds or thousands of APs and users. Numerical results show that our proposed JMRZF scheme can substantially outperform the local precoding schemes, even when a small part of APs are combined to deploy ZF and is implementable even when each AP has very few antennas. In addition, it is shown that our max-min power controls improves the spectral efficiency significantly, compared to the uniform power control scheme.

On a Parabolic Sine-Gordon Model

We consider a parabolic sine-Gordon model with periodic boundary conditions. We prove a fundamental maximum principle which gives a priori uniform control of the solution. In the one-dimensional case we classify all bounded steady states and exhibit some explicit solutions. For the numerical discretization we employ first order IMEX, and second order BDF2 discretization without any additional stabilization term. We rigorously prove the energy stability of the numerical schemes under nearly sharp and quite mild time step constraints. We demonstrate the striking similarity of the parabolic sine-Gordon model with the standard Allen-Cahn equations with double well potentials.