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• Snap-through phenomenon is shallow spherical shells made of FGM is investigated. • An active control strategy using sensor/actuator layers is proposed. • Critical buckling pressure of the spherical shell may be delayed using appropriate gain factors. • Budiansky criterion is used to distinguish the buckling pressure of the shell. The mechanical snap-through phenomenon represents one of the buckling modes inherent in shallow shells, exemplifying the shell's reaction to external loads, which can potentially have detrimental effects on structural performance. This article delves into the study of this phenomenon within the context of spherical shells. Leveraging functionally graded material (FGM) in the main layer of this structure proves instrumental in enhancing the shell's performance against rapid mechanical loads. Furthermore, the strategic placement of piezoelectric layers, both symmetrically and asymmetrically, coupled with the implementation of a proportional and derivative control system, facilitates the control of the shell's response. The formulation of displacement field and electric potential is grounded in the first-order shear deformation theory (FSDT) and second-order distribution, respectively. The strong form of nonlinear dynamic and electrostatic equations is derived using Hamilton's principle. Solving these equations is achieved through the implementation of the generalized differential quadrature (GDQ) method in the spatial domain and Newmark in the time domain. Additionally, the Newton-Raphson method is employed to tackle the inherent nonlinearity of the problem. The Budiansky's criterion is employed for the assessment of the load necessary for the buckling of the shell. Following the validation of results against numerical, analytical, and laboratory outcomes, a set of parametric results is presented. These results underscore the remarkable impact of the control system in mitigating shell deformation under time-dependent mechanical loads, as well as in postponing the occurrence of the snap-through phenomenon and damping the vibrations. [ABSTRACT FROM AUTHOR]

In order to improve the tracking accuracy of a hydraulic system, an improved ant colony optimization algorithm (IACO) is proposed to optimize the values of proportional–integral–derivative (PID) controller. In addition, this paper presents an experimental study on the parameters identification to deduce accurate numerical values of the hydraulic system, which also determines the relationship between control signal and output displacement. Firstly, the basic principle of the hydraulic system and the mathematical model of the electro-hydraulic proportional control system are analyzed. Based on the theoretical models, the transfer function of the control system is obtained by recursive least square identification method (RLS). Then, the key parameters of the control system model are obtained. Some improvements are proposed to avoid premature convergence and slow convergence rate of ACO: the transition probability is revised based adjacent search mechanism, dynamic pheromone evaporation coefficient adjustment strategy is adopted, pheromone update rule and parameters optimization range are also improved. Then the proposed IACO tuning based PID controller and the identification parameters are modeled and simulated using MATLAB/Simulink and AMESim co-simulation platform. Comparisons of IACO, standard ACO and Ziegler–Nichols (Z–N)PID controllers are carried out with different references as step signal and sinusoidal wave using the co-simulation platform. The simulation results of the bucket system using the proposed controller demonstrates improved settling time, rise time and the convergence speed with a new objective function J. Finally, experiments with leveling operations are performed on a 23 ton robotic excavator. The experimental results show that the proposed controller improves the trajectory accuracy of the leveling operation by 28% in comparison to the standard ACO-PID controller. • The mathematical models of electro-hydraulic proportional system are described. • The key control system parameters are identified and then validated against experiments. • An improved ant colony optimization algorithm is proposed for achieving excellent control performances. • Co-simulation platform is carried out to estimate the performance of controller. • Effectiveness of the improved ant colony optimization algorithm is validated by experiment. [ABSTRACT FROM AUTHOR]

Abstract A new model called games on convex geometries with a coalition structure is introduced, where all players and the coalition structure form a convex geometry, respectively. An explicit form of the proportional coalition solidarity value is given, which endows each union with the solidarity value in quotient games, and then allocates this value to players in a union following the proportions of their solidarity values in original games on convex geometries (i.e., without unions). Meanwhile, an axiomatization of this value is offered. Furthermore, the proportional coalition Shapley value is introduced. Its explicit form is offered, and an axiomatic system is studied. [ABSTRACT FROM AUTHOR]

Highlights • The proposed process uses the Fuzzy Extended AHP enhanced by the quantitative PRAT. • This framework can be used for prioritization of risks during budget constraints. • It benefits from the expert decision maker and from the real historical data. • It can lead to better investments for health and safety measures with the less cost. Abstract In this paper, we propose a safety risk assessment process using the Fuzzy Extended Analytic Hierarchy Process (FEAHP) for prioritizing the risks in worksites. Also, the FEAHP which responds the decision maker's opinion is enhanced by the Proportional Risk Assessment Technique (PRAT), which is a quantitative risk analysis and assessment process applied by using real accidents data. A real-life project example has been used in order to illustrate the functionality and adequability of the process. For validating the effectivity of the proposed framework, we compared the results of the process with the results of treating the example with using only the typical Analytical Hierarchy Process. The proposed framework could be a useful tool for decision makers to estimate the emergency of investing constrained budget in actions preventing specific kind of accidents for achieving the maximum health and safety protection with the minimum cost. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the position and yaw angle trajectory tracking control problem is studied for unmanned helicopters subject to both matched and mismatched disturbances. To achieve the trajectory tracking goal, a feedforward-feedback composite control scheme is proposed based on the combination of the generalized proportional integral observer and the block backstepping control techniques. The controller design process mainly consists of two stages. In the first stage, some generalized proportional integral observers are developed for the helicopter system to estimate the mismatched, matched disturbances and their (higher-order) derivatives. In the second stage, the composite controller is designed by integrating the block backstepping control method and the disturbance estimates together. The proposed composite scheme guarantees asymptotic tracking performances for the position and yaw angle of the helicopter to the desired trajectories even in the presence of fast time-varying disturbances. Numerical simulations demonstrate the effectiveness of the proposed composite control scheme. [ABSTRACT FROM AUTHOR]

Abstract A three-dimensional (3D) multiphase Eulerian computational fluid dynamics (CFD) model was developed to investigate the effect of a simultaneous three-angular motion (roll, yaw and pitch) on the performance of an air-water-oil separator. The dynamic mesh method with a 3D rotational matrix was used to simulate the three-phase separator under simultaneous three-angular motion. The pressures at water and oil outlets were adjusted by a user-defined function based on a proportional control algorithm. The CFD model was validated against experimental free oscillations of an immiscible two-fluid system under a pitching motion. The simultaneous three-angular motion with an amplitude 2° and a period of 8 s showed an oil purity of 98% and an oil recovery of 99%, which were comparable to those of the onshore separator. However, the 4° simultaneous three-angular motion deteriorated the oil recovery to 92% and the water purity to 75%. As the separation performance of the pitching motion was similar to that of the simultaneous three-angular motion, the performance of the three-phase separator can be tested simply by the pitching motion. Graphical abstract Image Highlights • A three-phase Eulerian CFD model was developed for an air-water-oil separator. • The CFD model was validated with experimental free oscillations of two liquids. • Purity and oil recovery remained high at a 2° simultaneous three-angular motion. • A 4° simultaneous three-angular motion decreased the oil recovery from 99 to 92%. [ABSTRACT FROM AUTHOR]

Highlights • The long-term performance of solar water heating systems is simulated. • A criterion to compare systems with on-off and proportional control is developed. • The proportional control performance may be 50 % higher than the on-off control. • The performance of proportional control systems increases with storage volume. • The on-off control performance is not significantly affected by storage volume. Abstract Two simplified solar water heating models were used to simulate the yearly solar fraction of systems using two strategies to control collector fluid flow: on-off and proportional control. Since the on-off control depends on the flow rate of the collector fluid, while the proportional control depends on the temperature of the fluid exiting the collector, a genetic algorithm was used to optimize the parameters that control fluid flow, i.e. the values of collector flow rate and collector fluid temperature that maximize the solar fraction using both on-off and proportional control schemes, respectively. Simulated results showed that for very low collector areas, the on-off control scheme is more effective, but for medium to high areas (comprising the range of usable collector areas), the proportional control scheme is more effective. It was found that the solar fraction of systems using proportional control may exceed the solar fraction of systems using on-off control by more than 50 %. Moreover, it was also found that for the proportional control scheme, the solar fraction always increases with increasing storage volume, but for the on-off scheme, especially for medium to high collector areas, the solar fraction generally remains constant or even decreases slightly with increasing storage volume. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the proportional–integral (PI) boundary feedback control for the linear hyperbolic systems of balance laws which control and output measures are located at the boundaries. We address the issue of feedback stabilization by means of PI boundary controllers. By constructing a new weighted Lyapunov function, the sufficient conditions in terms of matrix inequalities are developed for the exponential stability of closed-loop systems. These results are illustrated by the linearized Aw–Rascle–Zhang (ARZ) traffic flow model. We design a PI boundary controller to stabilize the oscillations of the traffic parameters of a freeway segment and evaluate the performance with numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the global dissipativity problem is investigated for the quaternion-valued memristor-based neural networks (QVMNNs) with proportional delay. Firstly, the mathematical model of QVMNNs is proposed, which is a challenging model due to the unbounded delay and the quaternion field. Secondly, based on matrix measure method and Lyapunov theorem, combing with modulus inequality technique and generalized Halanay inequality technique, some sufficient conditions guaranteeing global dissipativity of QVMNNs with proportional delay are derived. Moreover, the global attractive set of QVMNNs can also be obtained. Finally, three numerical examples are presented to demonstrate the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

Abstract This paper accords the level control of single-input-single-output (SISO) level control system based on the fusion of sliding mode control (SMC) and evolutionary techniques or bio-inspired techniques. The non-dominated sorting genetic algorithm II (NSGA-II) and multi-objective particle swarm optimization (MOPSO) are considered as two evolutionary techniques. Here, a comparative analysis of performances of an optimal proportional–integral (PI) controller, proportional–integral–derivative (PID) controller, conventional SMC, NSGA-II based tuned SMC and SMC parameter tuning using MOPSO algorithm has been carried out through MATLAB/SIMULINK. The objective functions, integral absolute error (IAE), integral squared error (ISE) and an integration of weighted objective function aggregated approach of the error performance indices, IAE and ISE are considered. Realistic conditions are used in a plant for testing the robustness of controller. The stability of the controller is successfully obtained which satisfies the Lyapunov stability criteria. Reduction in long settling time with tiny magnitude variations about an equilibrium point is achieved using bio-inspired techniques. The simulation as well as experimental results reveal that SMC parameter tuning based on NSGA-II algorithm gives a better performance as compared to the other design strategies. Graphical abstract Highlights • A novel evolutionary based FOSMC strategy has been proposed for level control system. • A performance comparison of conventional controllers like PI, PID, SMC have been carried out with NSGA-II tuned SMC and MOPSO based tuned SMC through MATLAB Simulink and real-time experimentation. • Proposed strategy shows superior tracking performance and better robustness against external disturbances and uncertainties. [ABSTRACT FROM AUTHOR]

Highlights • Road, weather, and geometric characteristics have a similar effect on crash injury severity of at-fault and not at-fault drivers. • Driver age, gender, and physical condition influence crash injury severity of not at-fault drivers. • Vehicle type, and, the number and type of traffic rule violations influence crash injury severity of not at-fault drivers. • Motorcyclists and drivers 70 years or older are observed to be the most vulnerable road users. Abstract This paper examines and compares the effect of selected variables on driver injury severity of, both, at-fault and not at-fault drivers. Data from the Highway Safety Information System (HSIS) for the state of North Carolina was used for analysis and modeling. A partial proportional odds model was developed to examine the effect of each variable on injury severity of at-fault driver and not at-fault driver, and, to examine how each variable affects these two drivers’ injury severity differently. Road characteristics, weather condition, and geometric characteristics were observed to have a similar effect on injury severity in a crash to at-fault and not at-fault drivers. Age of the driver, physical condition, gender, vehicle type, and, the number and type of traffic rule violations were observed to play a significant role in the injury severity of not at-fault drivers when compared to at-fault drivers in the crash. Moreover, motorcyclists and drivers 70 years or older are observed to be the most vulnerable road users. [ABSTRACT FROM AUTHOR]

Abstract This paper presents iterative learning control of the phase-shift full-bridge series-resonant inverter (PSFB-SRI). It has the merits of high conversion efficiency, medium-to-high power capacity, compact size, and low current–voltage stress on components, but the demerits of highly nonlinear dynamics that varies in a wide range depending on the operating points. The PSFB-SRI also suffers from a grid-voltage disturbance when it operates in grid-connected environment. To overcome these control problems, an iterative learning controller (ILC) supplemented with a proportional controller is developed and applied to the PSFB-SRI. Conventional proportional controller is used to improve the output current tracking performance. The ILC makes use of both previous-cycle and current-cycle learning terms which help the system output to converge to the reference trajectory. It is also simple in structure and easy to implement in practical applications. First-harmonic approximation of the PSFB-SRI model has been conducted and the resulting nonlinear large-signal model was used to construct the developed ILC. A detailed design guideline of the control parameters is provided. Numerical simulations validate the proposed control scheme, and experiments using a 500-W prototype demonstrate its feasibility. Graphical abstract Highlights • The iterative learning control scheme is first designed for highly nonlinear grid-connected PSFB-SRI. • ILC with current learning term can guarantees the global tracking error convergence and achieve the desirable steady-state response. • The nonlinear large-signal model of the PSFB-SRI is considered and used to construct the developed ILC. • It is computationally simple and easy to implement in practical applications. [ABSTRACT FROM AUTHOR]

In this paper, the distributed bearing-based formation control problem for networked robotic systems with parametric uncertainties is investigated. Firstly, under the consideration that the task-space velocity is measurable, a reference control input is designed to achieve a bearing constrained target formation. For the unmeasurable task-space velocity case, an observer-based reference velocity scheme is proposed and only the local relative task-space position measurement is needed to achieve globally bearing-based formation stabilization. By designing a velocity feedback in proportional-integral reference velocity control scheme, at least two leaders can handle the leader–follower formation tracking problem, in which the followers do not need any global information. Finally, some simulation results are provided to demonstrate the effectiveness of the proposed control laws. [ABSTRACT FROM AUTHOR]

Abstract In the classic cake-cutting problem (Steinhaus, 1948), a heterogeneous resource has to be divided among n agents with different valuations in a proportional way —giving each agent a piece with a value of at least 1 ∕ n of the total. In many applications, such as dividing a land-estate or a time-interval, it is also important that the pieces are connected. We propose two additional requirements: resource-monotonicity (RM) and population-monotonicity (PM). When either the cake or the set of agents grows or shrinks and the cake is re-divided using the same rule, the utility of all remaining agents must change in the same direction. Classic cake-cutting protocols are neither RM nor PM. Moreover, we prove that no Pareto-optimal proportional division rule can be either RM or PM. Motivated by this negative result, we search for division rules that are weakly-Pareto-optimal — no other division is strictly better for all agents. We present two such rules. The relative-equitable rule, which assigns the maximum possible relative value equal for all agents, is proportional and PM. The so-called rightmost mark rule, which is an improved version of the Cut and Choose protocol, is proportional and RM for two agents. [ABSTRACT FROM AUTHOR]

Two large area position sensitive Multi Wire Proportional Counters (MWPCs) have been developed for the detection of Fission Fragments (FFs). The detectors were characterized using FFs from 252 Cf source to obtain position information by employing delay-line read out method and the resolution is about 1 mm in both X and Y directions. Velocity distribution of the FFs produced from spontaneous fission of 252 Cf has been measured employing a time-of-flight (TOF) technique, using a barium fluoride (Ba F 2 ) detector and a MWPC. The most probable velocities obtained for the heavy and light fragment groups are 1.035 ± 0.003 and 1.378 ± 0.004 cm/ns, respectively. The energy dependence of fragment velocity distribution was also studied after degrading the energy of the fragments by using Mylar foils. It is observed that the width of the distribution for the heavy fission fragments decreases with the reduction in the energies, but for light fragments it does not show any significant dependence on the energy. [ABSTRACT FROM AUTHOR]

We discuss the physics design of the next-generation spallation neutron target-moderator-reflector-shield (TMRS) assembly for the Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) at the Los Alamos Neutron Science Center (LANSCE). We developed this TMRS to improve the neutronic performance of the Lujan Center in the intermediate energy range (keV–MeV) enabling a variety of new nuclear physics experiments, as well as increasing the quality of the ongoing experiments. The results of our Monte Carlo optimization study indicate that the new TMRS will generate keV–MeV neutrons with higher intensity and improved time resolution. At the same time, the new design largely maintains its current performance in the cold and thermal ranges supporting materials research. In this article we show that the new TMRS has the potential to enhance the Lujan Center’s experimental capability in a wider interval of energies – cold to intermediate – after its scheduled installation in 2020. [ABSTRACT FROM AUTHOR]

A hydraulic top drive is a high-power gyrator used in oil or scientific drilling rigs, whose shaft is connected to drill pipe when it drives drilling tools to excavate well. The output speed of top drive determines the speed of drill bit directly. Load acting on the top drive shaft fluctuates randomly, which will cause top drive output speed hard to be in consistent with the setting value. This paper presents a main transmission system of a hydraulic top drive designed for deep continental scientific drilling, which was built with a multi-stage mechanical structure and a closed circuit hydraulic system with variable displacement pumps and motors. Electro-hydraulic proportional control was applied to vary the speed of the hydraulic top drive. A theoretical model is detailed for the hydraulic top drive main transmission system. Among the new techniques proposed in this paper is a simulation model for studying the performance of hydraulic top drive and capturing speed characteristics under fluctuant load. A drilling experiment of the hydraulic top drive was performed on the CRUST-I drilling rig in CCSD-SK-II well site. This paper concludes by comparing the results of the simulation model with theoretical results and drilling experimental data gathered in the hydraulic top drive possessing the same architecture, components, and control methods used within the simulation model. The drilling experiment and the analysis result showed that the hydraulic top drive could meet the requirements of deep continental scientific drilling and that the speed could be output according to the setting speed with very small oscillation. The simulation model can be used for several applications such as hydraulic top drive design and performance analysis of various drilling conditions. [ABSTRACT FROM AUTHOR]

Leaf wax n -alkanes provide a valuable palaeoecological proxy, but their interpretation requires an understanding of the scale of temporal and spatial integration in soils. Leaf wax n -alkanes are continually deposited into soils directly from local plants as well as from more distant plants via wind or water transport. In addition, n -alkanes can persist in soils for thousands of years, and tend to decrease in age with shallower depth. To explore whether the uppermost soils reflect recent leaf fall inputs we compared surface soils and modern vegetation from 20 sites along a transect across Australia. At each site, the three most dominant plant species and a soil sample from the top 3 cm were analysed for n- alkane concentration, average chain length (ACL), proportional abundance of C 33 and C 29 (Norm33) and carbon preference index (CPI). Chain length distributions differ between trees and grasses, with a higher proportion of C 29 in trees and C 33 in grasses. Norm33 in soils correlates with proportional grass to tree cover across the transect. To model n -alkane inputs for each site, we calculated a predicted ACL, Norm33 and CPI using the dominant plants at that site, weighted by proportional species cover and n -alkane concentration. Predicted ACL, Norm33 and CPI inputs were generally higher than the soils, demonstrating that recent and local inputs do not dominate soil n- alkanes at our study sites. Thus, n -alkane distributions in surface soils do not correlate with local, current vegetation, but do correlate with proportional grass and tree cover, suggesting they provide a faithful record of large scale ecosystem structure. [ABSTRACT FROM AUTHOR]

Trajectory control plays an essential part in development of entry guidance systems for unpowered gliding entry. From an engineering standpoint, a trajectory control law in a simple structure as well as capable of high adaptability and flexibility is very appealing. To this end, a linear near-equilibrium glide model (LNEGM) is developed using an empirical near-equilibrium glide condition (NEGC). Unlike the prior work on linear approaches, the LNEGM is a flexible model in that it can represent the majority of the linear dynamics of the unpowered gliding entry trajectories. Based on the LNEGM, a linear trajectory control law is naturally obtained, which is composed of a feed-forward part and a proportional-derivative (PD) feedback part. The unique feature of the proposed linear trajectory control law is that the feedback gains are analytical equations associated with desired profiles and transient guidance performance requirements. A state-of-the-art application is given in which the proposed linear trajectory control law satisfactorily solves a common trajectory shaping problem for a class of numerical predictor-corrector guidance. [ABSTRACT FROM AUTHOR]

In this paper, based on actual road networks, a model of the non-homogeneous double-weighted fractal networks is introduced depending on the number of copies s and two kinds of weight factors w i , r i ( i = 1 , 2 , … , s ) . The double-weights represent the capacity-flowing weights and the cost-traveling weights, respectively. Denote by w i j F the capacity-flowing weight connecting the nodes i and j , and denote by w i j C the cost-traveling weight connecting the nodes i and j . Let w i j F be related to the weight factors w 1 , w 2 , … , w s , and let w i j C be related to the weight factors r 1 , r 2 , … , r s . Assuming that the walker, at each step, starting from its current node, moves to any of its neighbors with probability proportional to the capacity-flowing weight of edge linking them. The weighted time for two adjacency nodes is the cost-traveling weight connecting the two nodes. The average weighted receiving time (AWRT) is defined on the non-homogeneous double-weighted fractal networks. AWRT depends on the relationships of the number of copies s and two kinds of weight factors w i , r i ( i = 1 , 2 , … , s ) . The obtained remarkable results display that in the large network, the AWRT grows as a power-law function of the network size N g with the exponent, represented by θ = log s ( w 1 r 1 + w 2 r 2 + ⋯ + w s r s ) < 1 when w 1 r 1 + w 2 r 2 + ⋯ + w s r s ≠ 1 , which means that the smaller the value of w 1 r 1 + w 2 r 2 + ⋯ + w s r s is, the more efficient the process of receiving information is. Especially when w 1 r 1 + w 2 r 2 + ⋯ + w s r s = 1 , AWRT grows with increasing order N g as log N g or ( log N g ) 2 . In the classic fractal networks, the average receiving time (ART) grows with linearly with the network size N g . Thus, the non-homogeneous double-weighted fractal networks are more efficient than classic fractal networks in term of receiving information. [ABSTRACT FROM AUTHOR]

This paper employs a multivariable PI (proportional-integral) controller for inner-loop control and SISO (single-input single-output) PI controllers for outer-loop control for a VSC-HVDC (voltage source converter-based high voltage direct current) transmission system. To design the control system, first, a state-space model of VSC-HVDC transmission link is obtained in dq -coordinate frame. Then, using linearization technique the small-signal model is obtained. Next, a multivariable optimal PI controller is designed for the (inner-loop) linearized model using LQR (linear quadratic regulator) approach. Finally, the outer-loop SISO PI controller parameters are obtained using sequential design method (i.e., assuming that the inner-loop is must faster than the outer-loop). The advantage of using the MIMO (multi-input multi-output) PI controller over the conventional decouple-based PI controller for inner-loop control is studied through different performance and robustness measures, and also verified through simulations in presence of several disturbances and parameter variations. [ABSTRACT FROM AUTHOR]

This paper proposes an improved multi-loop control scheme for the single-phase uninterruptible power supply (UPS) inverter by using a plug-in odd-harmonic repetitive controller to regulate the output voltage. In the suggested control method, the output voltage and the filter capacitor current are used as the outer and inner loop feedback signals, respectively and the instantaneous value of the reference voltage feedforwarded to the output of the controller. Instead of conventional linear (proportional-integral/-resonant) and conventional repetitive controllers, a plug-in odd-harmonic repetitive controller is employed in the outer loop to regulate the output voltage, which occupies less memory space and offers faster tracking performance compared to the conventional one. Also, a simple proportional controller is used in the inner loop for active damping of possible resonances and improving the transient performance. The feedforward of the converter reference voltage enhances the robust performance of the system and simplifies the system modelling and the controller design. A step-by-step design procedure is presented for the proposed controller, which guarantees stability of the system under worst-case scenarios. Simulation and experimental results validate the excellent steady-state and transient performance of the proposed control scheme and provide the exact comparison of the proposed method with the conventional multi-loop control method. [ABSTRACT FROM AUTHOR]

To improve the efficiency of constructing a tunnel lining, an effective high-speed segment erection system is desired. Due to the excessive positioning errors and large joint forces caused by high speed and large inertia loads, a conventional segment erector is unable to achieve a high-speed erection process. To reduce the steady-state positioning error of a segment erector under high-speed working conditions, this work presents a speed and position compound control system (SPCS) based on the electro-hydraulic proportional control technology. A combined motion law with a smooth and continuous changing speed is adopted for the erecting motion to reduce joint force. Experiments are carried out on a Φ2.2 m segment erector test rig to evaluate the performances of the designed control system. Experimental results show that the SPCS is superior to the position feedback control system (PFCS) in terms of accuracy and joint force under high-speed working conditions. The maximum rotation speed of the erector with the SPCS can reach up to thrice that of the conventional segment erection system without decreasing the positioning precision and increasing the joint force. To further increase the segment erecting efficiency, a parallel speed and position compound control system (PSPCS) with multi-axis simultaneous movements is proposed. The coupling effects of the three positioning motions are analyzed. According to the experimental results, the time consumed by the erection system with PSPCS on the segment positioning process is further reduced to approximate one third of that by the erection system with SPCS. [ABSTRACT FROM AUTHOR]

The four-way proportional directional control valve has been widely used as the main stage spring constant for the two-stage proportional control valve (PDV). Since a tradeoff should be made between manufacturing costs and static performance, two symmetry dead-zones are introduced in the main stage spring constant: the center dead-zone caused by the center floating position and the intermediate dead-zone caused by the intermediate position. Though the intermediate dead-zone is much smaller than the center dead-zone, it has significant effect on the dynamic position tracking performance. In this paper, the cascade dead-zones problem in a typical two-stage PDV is analyzed and a cascade dead-zones model is proposed for the main stage spring constant. Then, a cascade dead-zones inverse method is improved with gain estimation and dead-zone detection to compensate the dead-zone nonlinearity. Finally, a digital controller is designed for verification. The comparative experimental results indicate that it is effective to reduce the large position tracking error when the proposed method is applied. [ABSTRACT FROM AUTHOR]

This paper investigates the output feedback control problem of a class of nonlinear systems with sensor noise and actuator degradation. Firstly, by using the descriptor observer approach, the origin system is transformed into a descriptor system. On the basis of the descriptor system, a novel Proportional Derivative (PD) observer is developed to asymptotically estimate sensor noise and system state simultaneously. Then, by designing an adaptive law to estimate the effectiveness of actuator, an adaptive observer-based controller is constructed to ensure that system state can be regulated to the origin asymptotically. Finally, the design scheme is applied to address a flexible joint robot link problem. [ABSTRACT FROM AUTHOR]

Mobile data offloading has been proposed as a solution for the network congestion problem that is continuously aggravating due to the increase in mobile data demand. However, the majority of the state-of-the-art is focused on the downlink offloading, while the change of mobile user habits, like mobile content creation and uploading, makes uplink offloading a rising issue. In this work we focus on the uplink offloading using IP Flow Mobility (IFOM). IFOM allows a LTE mobile User Equipment (UE) to maintain two concurrent data streams, one through LTE and the other through WiFi access technology, that presents uplink limitations due to the inherent fairness design of IEEE 802.11 DCF by employing the CSMA/CA scheme with a binary exponential backoff algorithm. In this paper, we propose a weighted proportionally fair bandwidth allocation algorithm for the data volume that is being offloaded through WiFi, in conjunction with a pricing-based rate allocation for the rest of the data volume needs of the UEs that are transmitted through the LTE uplink. We aim to improve the energy efficiency of the UEs and to increase the offloaded data volume under the concurrent use of access technologies that IFOM allows. In the weighted proportionally fair WiFi bandwidth allocation, we consider both the different upload data needs of the UEs, along with their LTE spectrum efficiency and propose an access mechanism that improves the use of WiFi access in uplink offloading. In the LTE part, we propose a two-stage pricing-based rate allocation under both linear and exponential pricing approaches, aiming to satisfy all offloading UEs regarding their LTE uplink access. We theoretically analyse the proposed algorithms and evaluate their performance through simulations. We compare their performance with the 802.11 DCF access scheme and with a state-of-the-art access algorithm under different number of offloading UEs and for both linear and exponential pricing-based rate allocation for the LTE uplink. Through the evaluation of energy efficiency, offloading capabilities and throughput performance, we provide an improved uplink access scheme for UEs that operate with IFOM for uplink offloading. [ABSTRACT FROM AUTHOR]

This paper describes an electro-hydraulic servo-actuator using dual-mode controllers in the control loop. The aim is a null stationary error and the shortest possible time response. The mathematical model of the servo-actuator is constructed taking into account the functional model of the open-centre servo-valve. This model is used for the numerical simulation of the system functioning. The model uses mass flow ratios in order to obtain a more stable and realistic numerical simulation. The dynamic simulation studies the behavior of the servo-actuator with different controllers in the control loop. The model tests the proportional controller and types of programmable logic controllers. The controllers are implemented in MATLAB/SIMULINK. The controllers are tested by numerical simulation. One may assume the technical superiority of programmable logic controllers. [ABSTRACT FROM AUTHOR]

A tuning method of the fractional order proportional integral speed controller for a permanent magnet synchronous motor is proposed in this paper. Taking the combination of the integral of time and absolute error and the phase margin as the optimization index, the robustness specification as the constraint condition, the differential evolution algorithm is applied to search the optimal controller parameters. The dynamic response performance and robustness of the obtained optimal controller are verified by motor speed-tracking experiments on the motor speed control platform. Experimental results show that the proposed tuning method can enable the obtained control system to achieve both the optimal dynamic response performance and the robustness to gain variations. [ABSTRACT FROM AUTHOR]

In this paper, a class of recurrent neural networks with multi-proportional delays is studied. The nonlinear transformation transforms a class of recurrent neural networks with multi-proportional delays into a class of recurrent neural networks with constant delays and time-varying coefficients. By constructing Lyapunov functional and establishing the delay differential inequality, several delay-dependent and delay-independent sufficient conditions are derived to ensure global exponential periodicity and stability of the system. And several examples and their simulations are given to illustrate the effectiveness of obtained results. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of hydraulic drive with proportional control are investigated by experimental and modeling approaches. The article presents research on linear motion drive based on hydraulic cylinder with electrical position feedback. The mathematical drive model is developed taking into account the characteristics of pump station, hydraulic cylinder, inertial load, dynamic characteristic of proportional valve, and electrical position feedback. The proportional valve characteristic is determined based on experimental static flow characteristics and transfer function of spool displacement on input current. Bode diagram for displacement of cylinder is obtained experimentally and by modeling for frequencies of 0.05 to 5 Hz. It is shown that for frequencies of up to 3 Hz, the proposed model provides a 3% accuracy. [ABSTRACT FROM AUTHOR]

We analyze political selection in a closed list proportional system where parties have strong gate-keeping power, which they use as an instrument to pursue votes. Parties face a trade-off between selecting loyal candidates or experts, who are highly valued by the voters and thus increase the probability of winning the election. Voters can be rational or behavioral. The former cares about the quality mix of the elected candidates in the winning party, and hence about the ordering on the party list. The latter only concentrate on the quality type of the candidates in the top positions of the party list. Our theoretical model shows that, to persuade rational voters, parties optimally allocate loyalists to safe seats and experts to uncertain positions. Persuading behavioral voters instead requires to position the experts visibly on top of the electoral list. Our empirical analysis, which uses data from the 2013 National election in Italy—held under closed list proportional representation—and from independent pre-electoral polls, is overall supportive of voters' rational behavior. Loyalists (i.e., party officers or former members of Parliament who mostly voted along party lines) are overrepresented in safe positions, and, within both safe and uncertain positions, they are ranked higher in the list. [ABSTRACT FROM AUTHOR]

In order to improve the control effectiveness of some nonlinear processes, we propose a novel nonlinear guided intelligent controller (NGIC) inspired by the bi-cooperative regulation mechanism and the regulation characteristics of glucose in human body. The NGIC comprises a cooperative control unit (CCU), an enhanced control unit (ECU), an inhibited control unit (ICU) and an auxiliary control unit (ACU). To shorten the rise time of the process variable, the ECU first takes effect with a rapid step action when the set-point changes or a large error appears. After a prescribed time, the ICU takes effect with an opposite step action to reduce the system overshoot or to avoid oscillation. When the control system achieves a prescribed steady state or the control time exceeds a pre-defined limitation, the ACU becomes effective to improve the control precision of the NGIC by applying a central proportional law with a guided final control output. As a super managing unit, the CCU coordinates all the work of the ECU, the ICU and the ACU to make the NGIC eliminate the control error with short rise time, small overshoot and short settling time. To testify the control performance of the NGIC, we apply the NGIC to a bio-reactor process with large time variation. The simulation results indicate that the NGIC has better control performance than the conventional PID, internal model controller (IMC) and artificial neural network (ANN) controller. Hence, the NGIC is significant to improve the control effect for some complex practical processes. [ABSTRACT FROM AUTHOR]

In a hydraulic control system (herein, termed a major control loop), a proportional directional control (PDC) valve with spool position feedback may work in a minor (or inner) control loop. In this study the authors propose control designs to improve the performance of the PDC valve control loop (a minor control loop). At first, the mathematical model for the PDC valve is developed through an experimental identification process. Then, a dead-zone compensator that facilitates jumping of the overlap zone in spool/sleeve combination is devised and applied. A reference input following controller (including PI-D and feed-forward controller) that enables robust control of the PDC valve under disturbances is devised using the pole placement method and the zero placement method. Subsequently, an input shaping filter is incorporated into the devised control system to improve the reference following characteristic in high frequency range. Finally, the effectiveness of the proposed control design is verified experimentally. [ABSTRACT FROM AUTHOR]

This paper studies small-signal modelling and control design for a photovoltaic (PV) based water pumping system without energy storage. First, the small-signal model is obtained and then, using this model, two proportional–integral (PI) controllers, where one controller is used to control the dc-link voltage and the other one to control the speed of induction motor, are designed to meet control goals such as settling time and peak overshoot of the closed loop responses. The loop robustness of the design is also studied. For a given set of system parameters, simulations are carried out to validate the modelling and the control design. [ABSTRACT FROM AUTHOR]

For a physical or biological model whose dynamics is described by a higher order difference equation u n + 1 = f ( u n , u n − 1 , … , u n − k + 1 ) , we propose a version of a target oriented control u n + 1 = c T + ( 1 − c ) f ( u n , u n − 1 , … , u n − k + 1 ) , with T ≥ 0 , c ∈ [ 0 , 1 ) . In ecological systems, the method incorporates harvesting and recruitment and for a wide class of f , allows to stabilize (locally or globally) a fixed point of f . If a point which is not a fixed point of f has to be stabilized, the target oriented control is an appropriate method for achieving this goal. As a particular case, we consider pest control applied to pest populations with delayed density-dependence. This corresponds to a proportional feedback method, which includes harvesting only, for higher order equations. [ABSTRACT FROM AUTHOR]

This article deals with Automatic Generation Control (AGC) of a multi area interconnected hydro thermal system in different modes using intelligent integral and proportional-integral controllers and provides the comparative analysis of electrical and mechanical governors. Appropriate Generation Rate Constraints (GRC) has been considered for the hydro and thermal generation plants. These cumulated thermal areas are considered with reheat turbines. Performances of reheat turbine mechanical governor and hydro turbine electrical governor with its dynamic responses have been investigated. Further, selection of suitable integral and proportional-integral controllers has been investigated with a Minority Charge carrier Inspired Algorithm (MCI). Cumulative system performance is examined considering with different load perturbation in both cumulative thermal areas. Further, system is investigated with different frequency bias values and results are explored. [ABSTRACT FROM AUTHOR]

This paper details the fabrication and performance evaluation of an inline Mach–Zehnder interferometer (MZI) consisting of a perfluorinated graded-index plastic optical fiber fabricated via a heat-and-pull tapering technique. This MZI exhibits interference fringes that are sufficiently sharp for usage as refractive-index (RI) and strain sensors. These interference fringes shift linearly with the RI of the surrounding medium, with a proportionality constant of 3.44 nm/RI unit. The measured strain sensitivity of 0.2 pm/μɛ suggests that the MZI may be viable for strain-sensing applications. [ABSTRACT FROM AUTHOR]

Designing a proportional derivative (PD) controller has as main problem, to obtain the derivative of the output error signal when it is contaminated with high frequency noises. To overcome this disadvantage, the supertwisting algorithm (STA) is applied in closed-loop with a PD structure for multi-input multi-output (MIMO) second order nonlinear systems. The stability conditions were analyzed in terms of a strict non-smooth Lyapunov function and the solution of Riccati equations. A set of numerical test was designed to show the advantages of implementing PD controllers that used STA as a robust exact differentiator. The first numerical example showed the stabilization of an inverted pendulum. The second example was designed to solve the tracking problem of a two-link robot manipulator. [ABSTRACT FROM AUTHOR]

Highlights: [•] The 2-phase composite approach of Estrin et al. is critically analyzed and refined. [•] The refined model ensures non-negative dislocation densities and consistent fluxes. [•] The refined micro model is coupled with a macroscopic model of Shutov and Kreissig. [•] The evolution of dislocation densities depends significantly on the load path. [•] A drop of the dislocation density is predicted shortly after the load path change. [ABSTRACT FROM AUTHOR]

Abstract: We develop a novel adaptive tuning method for classical proportional–integral–derivative (PID) controller to control nonlinear processes to adjust PID gains, a problem which is very difficult to overcome in the classical PID controllers. By incorporating classical PID control, which is well-known in industry, to the control of nonlinear processes, we introduce a method which can readily be used by the industry. In this method, controller design does not require a first principal model of the process which is usually very difficult to obtain. Instead, it depends on a fuzzy process model which is constructed from the measured input–output data of the process. A soft limiter is used to impose industrial limits on the control input. The performance of the system is successfully tested on the bioreactor, a highly nonlinear process involving instabilities. Several tests showed the method's success in tracking, robustness to noise, and adaptation properties. We as well compared our system's performance to those of a plant with altered parameters with measurement noise, and obtained less ringing and better tracking. To conclude, we present a novel adaptive control method that is built upon the well-known PID architecture that successfully controls highly nonlinear industrial processes, even under conditions such as strong parameter variations, noise, and instabilities. [Copyright &y& Elsevier]

Abstract: Proportional delay is a kind of unbounded time-varying delay, which is different from unbounded distributed delays. In this paper, asymptotic stability of the equilibrium point of cellular neural networks with multiple proportional delays is presented. Sufficient conditions for delay-dependent global asymptotic stability and delay-independent uniform asymptotic stability of the system are obtained by employing matrix theory and constructing Lyapunov functional. Two examples are given to illustrate the effectiveness of the obtained results and less conservative than previously existing results. [Copyright &y& Elsevier]

Abstract: Giant persistent currents that occur in quasiperiodic Thue–Morse array of mesoscopic rings are proposed. As the order of the system increases, the maximum persistent current increases exponentially. The giant persistent current in a system with higher order is greater than that in traditional structures. It is found that the maximum persistent current occurs in the ring near the middle position of the array. The persistent current is also proportional to the sharpness of the transport resonance, which is dependent on the width of the allowed band in the bandstructure. A rule to determine the occurrence energy of the giant persistent currents for a system with arbitrary order is also proposed. [Copyright &y& Elsevier]

Abstract: In this paper a control and optimization procedure for bone remodeling simulations was adopted to study the effect of the osteocyte influence range on the predicted density distribution. In order to reach this goal, the osteocyte network regulating bone remodeling process in a 2-D bone sample was numerically simulated. The assumed proportional-integral-derivative (PID) bone remodeling rule was related to the error signal between the strain energy density and a selected target. Furthermore the control parameters and the target were optimally determined minimizing a suitable cost index: the goal was to minimize the final mass and the energy thus maximizing the stiffness. The continuum model results show that the developed and adapted trabecular structure was consistent with the applied loads and only depended on the external forces, the value of the cost index, the maximum attainable elastic modulus value (hence, the maximum density value) and the value of the energy target. The remodeling phenomenon determined the number and thickness of the trabeculae which are formed from a uniform distribution of mass density in the considered domain; this number and these thicknesses are controlled by the values assigned to the parameters of the model. In particular, the osteocyte decay distance (D) of the influence range affected the trabecular patterns formation, showing an important effect in the adaptive capacity of the optimization numerical model. [Copyright &y& Elsevier]

Abstract: In this work, we aim to solve the following multi-class inference problem: for given groups of unlabeled samples, a reliable multi-class classifier is expected to deterministically predict the label of each sample under the condition that only the class proportion information of each group is provided. Actually many modern applications can be abstracted to such a problem, e.g., large-scale images annotation, spam filtering, and improper content detection, where the class proportions of samples can be cheaply obtained while sample-wise labeling is prohibitive or quite hard. However, this problem has not been thoroughly investigated in previous works yet though it is much important in practice. The main challenging essentially lies on the severely under-determining itself. In this paper, we propose to utilize the natural sparsity of labels to alleviate this issue, and then formulate the classifier learning as a sparsity pursuit problem over a standard simplex. Moreover, due to the inapplicability of the popular method for this case, we propose an optimization method to directly tackle the hard sparsity constraint, i.e., , based on the Augmented Lagrangian Multiplier (ALM) which can nicely provide a global convergence guarantee. It is noteworthy that our overall solution can not only directly predict the labels of the training and new samples, but also gracefully utilize the test samples to further boost the classification performance in a manner of semi-supervised learning. The experimental results on two benchmark datasets well validate the effectiveness of the proposed method. [Copyright &y& Elsevier]

Highlights: [•] ITER remote handling maintenance can be controlled safely over a large distance. [•] Bilateral teleoperation experiments were performed in a local network. [•] Wave variables make the controller robust against constant communication delays. [•] Master and slave position synchronization guaranteed by proportional action. [Copyright &y& Elsevier]

Abstract: This paper introduces a new design method of fractional-order proportional–derivative (FOPD) and fractional-order proportional–integral–derivative (FOPID) controllers. A biquadratic approximation of a fractional-order differential operator is used to introduce a new structure of finite-order FOPID controllers. Using the new FOPD controllers, the controlled systems can achieve the desired phase margins without migrating the gain crossover frequency of the uncontrolled system. This may not be guaranteed when using FOPID controllers. The proposed FOPID controller has a smaller number of parameters to tune than its existing counterparts. A systematic design procedure is identified in terms of the desired phase and the gain margins of the controlled systems. The viability of the design methods is verified using a simple numerical example. [Copyright &y& Elsevier]

Abstract: This paper presents an implementation of a hybrid system consisting of a low-cost quadrotor and a small pushcart. The quadrotor is controlled with classical Proportional⿿Integral⿿Derivative (PID) controller for autonomous visual tracking and landing on the moving carrier. The vision-based tracking and landing approach utilizes enhancement of red, green and blue (RGB) color information rather than grayscale information of the helipad on the carrier, which shows fast and robust performance in different lighting conditions. This work is characteristic with utilizing the off-the-shelf affordable quadrotor and accomplishing the complex task using only the relative pixel position in image plane without communication between the quadrotor and carrier. The quadrotor's relative position to helipad is estimated with a frequency up to 30Hz from the video stream, which enables the quadrotor to fly autonomously while performing real-time visual tracking and landing on the carrier. Series of experiments show that our system is easy to deploy and tune, simple and robust, also low-cost. [Copyright &y& Elsevier]

Abstract: This work deals with the fault diagnosis problem, some new properties are found using the left invertibility condition through the concept of differential output rank. Two schemes of nonlinear observers are used to estimate the fault signals for comparison purposes, one of these is a proportional reduced order observer and the other is a sliding mode observer. The methodology is tested in a real time implementation of a three-tank system. [Copyright &y& Elsevier]