Control Structure Design Research Articles

Adaptive variable structure controller design of uncertain nonlinear systems based on state estimation: a new scheme

Adaptive variable structure controller design of uncertain nonlinear systems based on state estimation: a new scheme

전방향 가변 지지 메커니즘의 기구학 및 모의 해석 검증

In recent years, with increasing levels of e-commerce, the use of mobile robots in logistics has increased significantly. The most common driving mechanism for mobile robots is the differential type, but the omnidirectional type mechanism, too, is widely used due to its high maneuverability in crowded environments. Meanwhile, studies on a variable footprint mechanism (VFM) have been conducted to improve the maneuverability and driving stability of mobile robots. The extant VFMs offer some advantages, but they also have some limitations such as limited motion range due to structural singularity and complex controller design due to highly coupled parameters in kinematics. In this paper, an omnidirectional variable footprint mechanism (OVFM) is proposed to overcome these limitations. The proposed OVFM is designed with a diamond-shaped link structure that maximizes the motion range without singularity and a synchronized drive chain to achieve variable motion. The kinematic model of the proposed OVFM is mathematically derived, and it is demonstrated that the parameters related to VFM are only coupled to the rotation of the mobile robot, which could simplify controller design. The kinematic model is verified using the dynamics simulation tool RecurDyn in two different scenarios (one for variable motion under the static condition and the other for variable motion under the dynamic condition). The results indicate that the proposed kinematic model can be used to predict the motion of OVFM with acceptable errors that originate from the inherent nature of slip and vibration of Mecanum wheels.

An accurate numerical method for inversion of Laplace transforms with applications in process dynamics and control

AbstractLaplace transforms are frequently used in the design of control structures for chemical engineering processes. In this paper, we have developed a novel numerical method to invert Laplace transforms, which involves a particular system of linear algebraic equations. We have proven that the error of our method is bounded, and the proposed formula asymptotically converges to the exact intended Laplace inverse function. A set of numerical simulations have been carried out to demonstrate the efficiency and reliability of our method. As a salient advantage, in addition to its high accuracy, our method requires the Laplace transform function to be defined only on the real axis.

Structured controller design for closed‐loop D ‐stability in convex/non‐convex regions: Mixed integer‐linear programming approach

Structured controller design for closed‐loop <i>D</i> ‐stability in convex/non‐convex regions: Mixed integer‐linear programming approach

Study of submountain river flow patterns constrained by a combined dam

Great attention around the world is paid to the design and construction of riverbank protection and channel control structures on submountain section of rivers. High slopes (i=0,001÷0,004 and higher), flow kinetics and ability to transport large amount of sediments are the features of submountain section of rivers.Most of the research in this sphere has been conducted on the study of patterns of flow constrained by transverse structures in valley parts of rivers.The main goal of this work is to establish the physical picture of flow around a combined dam in submountian river, the through-flow part of which is made of tetrahedrons, as well as to develop a design method for flow velocity field. Formations of two regimes have been established experimentally, i.e. “calm” at ia<icr and “critical” at ia≥icr. These regimes are mainly affected by flow contraction degree na, and Froude number Fr.The presence of the following zones was established: core, intensive turbulent mixing and backflow zones, as well as the affinity of velocity fields in the zone of mixing by Shlihting-Abramovich. Prandtl has realized the task for “calm” regime with the use of integral relationship expressing law of conservation of momentum in the flow, equation for conservation of discharge and differential equation for nonuniform motion of transit flow with the account of tangential turbulent stresses on lateral surfaces. As opposed to the existing solutions, we accounted for the presence of two regions of spreading with different slopes of water surface, horizontal component of fluid weight, nonuniform distribution of velocities in head section, high roughness and the case when sections of target and vertical contraction do not match. Satisfactory results were obtained by comparing theoretical solution and experimental data.

Optimized Design of CCD Temperature Control Structure of the Primary Focus Telescope

The primary focus telescope has the advantages of a large field of view and less loss of light energy, and plays an important role in the field of time-domain survey. The 1-meter large field-of-view telescope of Nanjing University uses the primary focus optical system. The 6k × 6k CCD is located at the primary focal point in the optical path. The CCD will have a large amount of heat during the working process, which will affect the telescope's imaging quality. According to the requirements of the imaging quality of the NTU 1-meter telescope optical system, the difference between the temperature of the CCD housing and the ambient temperature needs to be controlled within 1 ℃. Therefore, the paper proposes a temperature control scheme for thermal insulation materials, and optimizes the performance of the temperature control scheme. The temperature control accuracy of this solution is within 0.6 ℃.

Seamless Transition in Grid-connected Microgrid System using Proportional Resonant Controller

In this paper, the design of an inverter control structure based on the Proportional Resonant (PR) controller is dealt with in detail for attaining smooth transitions between the operating modes of a grid- connected microgrid system. The control strategy applied for the inverter is cascaded three-loop control viz., the grid current, voltage across the load, and the inverter output current loops. The inverter control is mainly focused to retain the voltage magnitude within the prescribed set limits and to have a good quality of the voltage across the load under all the modes of operation. A proportional resonant controller is designed by considering the transients and stability criteria into account under varying modes of operation. The design procedure of the Proportional resonant controller is given in detail. The three-phase grid-connected microgrid system considered under study is simulated in MATLAB/Simulink environment to operate under islanding condition as well as grid-connected condition and also changing modes from islanding to grid connected and vice versa. The simulation results are presented under various modes of operation to validate the controller design for a smooth transition between the modes of operation.

Coupled rigid-flexible modelling and dynamic characteristic analysis of electromechanical brake (EMB) units on trains

The electromechanical braking is a novel braking mode, which is the development direction of the electrification and intelligent train braking system. In this paper, a coupled-rigid-flexible model of the EMB unit is developed, and dynamic characteristics of the EMB unit are analysed based on the model. Firstly, assumed mode method is used to describe the axial and torsional vibration of the screw in nut-screw assembly, and lumped mass method is used to describe motions of other components in the EMB unit. Secondly, the EMB unit model is established and simulated in Matlab/Simulink software based on electro-mechanical and rigid-flexible coupling characteristics. Then the model parameters are calibrated by experiment. Finally, the simulated model is studied to analyse the influence of various factors on the dynamic characteristics of the EMB unit. The results indicate that an increment in viscous damping flats the fluctuation of the pushout force. The maximal pushout force decreases and the changing trend of force is different along with the rotational structure damping increases. The flexible vibration of the screw results in higher pushout force, meanwhile the fluctuation of the force is greater with higher braking instruction current value. When the ratio of the screw length to the screw cross-sectional diameter is 30, the pushout force varies along with the friction pairs wear under vibration. The study can provide references for structure design, control design and fault diagnosis of EMB units.

Analysis of rainfall extremes in the Ngong River Basin of Kenya: Towards integrated urban flood risk management

Extreme rainfall events are a major cause of highly disruptive flooding in small urban watersheds with limited flood risk management systems. In the Ngong River Basin of Kenya, such floods affect more than 0.5 Million residents within the Kibera informal settlements of Nairobi. However, there is paucity of information about the characteristics of the extreme rainfalls to support flood risk management. This study investigated the best-fit probability distribution models for the extreme rainfalls of the Ngong Basin using Block Maxima approach as a basis for anticipatory flood risk management. Daily rainfall data for the period between 1968 and 2017 were acquired from the existing two rainfall stations to support the analysis at monthly, seasonal and annual timescales. The Gamma, Pearson Type III, Gumbel and Generalized Extreme Value distributions were selected and applied to each timescale. Parameters of the distributions were determined using the Maximum-Likelihood estimator. The validity of the fitted probability models was tested using the Kolomogorov- Smirnov, Anderson-Darling and Cramer von Misses measures for Goodness of Fit. The best-fit probability distributions were subsequently used to establish the rainfall frequencies and return levels at annual timescales. The results show that Pearson Type III provided the best fit at monthly timescales during the dry spell months, while the Generalized Extreme Value distribution provided best results during the wet periods. At seasonal timescales, the Gamma distribution was noted to be the best-fit model. The return levels developed could essentially support the design of urban flood control structures for appropriate flood risk management.

Sediment Transport Modeling at Jelitik Estuary, Sungailiat - Bangka Regency for the Design of Sediment Control Structures

Since 2014 sedimentation at the estuary of Jelitik river, Sungailiat, Bangka has continued to increase. At this estuary, the ship traffic is very busy and there is National Fisheries Port Sungailiat. When the tide is low, the river mouth closes thus disrupting ship traffic. The Bangka Belitung Provincial Government is currently planning to build a sediment control infrastructure to reduce the sedimentation rate. To plan and determine the effectiveness of the jetties requires knowledge of sedimentation patterns around Jelitik estuary. Therefore this study was conducted to determine the pattern of sedimentation (distribution and rate) at the existing and ultimate conditions. The methods are field survey, analysis of field data, and computational modeling of sediment transport. Modeling of sediment transport was done using the Sand Transport Module of MIKE 21. Two scenarios were simulated for the existing and ultimate conditions. Based on this modeling, the sedimentation rate at Jelitik estuary is found uneven. In the existing condition, a large rate of sedimentation occurs on the southern side of the Jelitik River estuary, which reaches a maximum value of 2.75 m/year, with an average of 4.44 cm/year. Whereas in the ultimate condition, the sedimentation rate decreases to 0.0377 m/year.

Non-spillovercontroldesignof tall buildingsin modalspace

In this paper, a new algorithm for active control design of structures is proposed and investigated. The algorithm preserves the decoupling property of the modal vibration equation and eliminates the spillover problem, which is the main shortcoming in the independent modal space control (IMSC) algorithm. With linear quadratic regulator(LQR) control law, the analytical solution of algebraic Riccati equation and the optimal actuator control force are obtained, and the control design procedure is significantly simplified . A numerical example for the control design of a tall building subjected to wind loads demonstrates the effectiveness of the proposed algorithm in reducing the acceleration and displacement responses of tall buildings under wind actions.

Control structure design of a solid oxide fuel cell and molten carbonate fuel cell integrated system: Bottom-up analysis

A solid oxide fuel cell and molten carbonate fuel cell integrated system is a power generation system with enhanced fuel and carbon dioxide utilization. Due to its complex structure, designing a control system is important for its smooth and efficient operation. This study is a continuation from the previous study focusing on a top-down, steady-state economic analysis for synthesizing the control structure of the solid oxide fuel cell and molten carbonate fuel cell integrated system to maximize power generation and carbon dioxide utilization. In this study, a bottom-up analysis is performed to design a control layer and validate the proposed control structure via dynamic simulation. The control configuration uses a decentralized approach with proportional-integral-derivative control to maintain the fuel cell system at its optimum target. The control performance with the proposed control structure and configurations are evaluated and analyzed. Four control loops involving gas concentrations are considered, based on different time scales between the regulatory control and supervisory layers. The results of the proposed control system confirm that the integrated fuel cell system is controllable despite the deviation of the fuel cell voltages from their nominal values.

Research on the Motion Control Trajectory and Structure Design of a Lower Limb Standing Rehabilitation Training Device

Aiming at the problem of standing rehabilitation of lower limb motor dysfunction patient. Firstly, the standing movement process of human body is analyzed. Secondly, the exercise trajectory test and pressure distribution measurement test of healthy human body are studied. Thirdly, the structure of the lower limb standing rehabilitation training device is designed according to the collected joint trajectory. Finally, the movement control trajectory simulation of the lower limb standing rehabilitation training device is carried out according to the collected regional pressure. The simulation results of virtual prototype coincide with the test trajectory, which shows that the structure of the designed lower limb standing rehabilitation training device is reasonable, and the hybrid control method of force and position can realize the standing rehabilitation training for lower limb motor dysfunction patient in the light of the set exercise trajectory.

Integrated sliding mode and direct torque controls for improving transient traction in high-speed trains

Wheel slip control in high-speed trains is used to reduce the acceleration time and produce the maximum traction motor power. For controlling slip in a complete model of a train consisting of the traction motors, it is needed to keep the adhesion coefficient as much as possible by controlling the input voltage. In this article, integrated sliding mode and direct torque controls are used to control the transient traction in a full model of a high-speed railcar consisting of a wagon, two bogies, four wheelsets, and four traction motors. Cosimulations in SIMPACK with MATLAB/Simulink are carried out to evaluate the performance of the designed control structure. By comparing the results of the open-loop and closed-loop simulations, it is shown the acceleration time of the high-speed railcar is decreased 26% and the production of the traction motor power is increased 32% for both dry and wet surface conditions. It is also shown that the designed control structure is stable and robust in the presence of uncertainties.

Recent advances in the design of cardiovascular materials for biomedical applications.

Biomaterials dominate the field of cardiovascular therapeutics, a multitude of which have been used to repair and replace injured heart tissue. This field has evolved beyond the simple selection of compatible materials and now focuses on the rational design of controlled structures that integrate with the cardiovascular system. However, the compatibility of these materials with the blood presents a major limitation to their clinical application. In this context, surface modification strategies can enhance blood compatibility and several recent advances in this area have emerged. This review summarizes the recent applications of biomaterials in cardiovascular therapies, the improvements in their biocompatibility and the surface modification technologies that have the potential to improve clinical outcomes.

Control of a process with no reflux rate in heterogeneous extractive distillation (HED)

In this work, a process with no reflux rate (R) of distillate product in heterogeneous extractive distillation (HED) for the separation of close boiling compounds is proposed. The effects of pressure in HED and flowrate of solvent on controllability and economic performance are investigated. Close loop sensitivity tests show that an increase in flowrate of solvent can enhance the controllability but increases the annual total cost (TAC). Simulation shows that higher pressure in HED leads to lower flowrate ratio of solvent (EG) to feed. A lower pressure is preferred for economic index, but has worse controllability. There is trade-off between controllability and economic performance.The interaction between units is analyzed theoretically based on mass balance principle. The analysis can help further design of control structure. A basic control structure (CS1) based on modified alternative process with increased solvent flowrate is proposed first. Then an improved control structure (CS2) based on CS1 is proposed to reject the flowrate disturbance and address the interaction between units. Dual temperatures are applied in the recovery column (C2). The temperatures of two stages are controlled by the ratio of reflux rate to feed (R/F) and reboiler duty in C2, respectively. Pressure-compensated temperature control is applied to compensate temperature in the presence of flowrate disturbance. Dynamic responses show the improved control structure can handle ± 10% feed flowrate and ± 20% composition disturbances.

Emulation of Wind Turbine System Using Vector Controlled Induction Motor Drive

Depleting fossil fuels and concerns about global warming have forced a paradigm shift toward renewable energy resources in meeting our energy requirements. Wind energy utilization has been growing at a rapid rate fuelling research and development in high power wind turbines (WTs). To advance research and education in wind energy conversion systems, a controlled test bed is necessary that does not depend on wind availability. Majority of the existing WT emulation schemes employ a torque compensation loop to account for the inertia difference between the WT and motor used for emulation. However, the loop suffers from noise and instability issues. Also, the torque compensation term is sensitive to parameter estimates. This article proposes one degree of freedom (1-DOF) and 2-DOF control structures for WT emulation. It first illustrates the design and performance of 1-DOF control structure. It further proposes two controllers along with their prefilters in 2-DOF structure, which has superior performance than 1-DOF structure. The design of the controllers and prefilters is explained with the help of root locus. The performance of the WT emulator with the proposed control structures is demonstrated through simulations and experiments on a 7.5 kW doubly fed induction generator driven by a 5.5 kW squirrel cage induction motor, where the dynamics and steady-state operation of a WT–generator system are emulated.

A Preliminary Design of a Hybrid Machine for Additive and Subtractive Manufacturing

&lt;p&gt;Additive manufacturing (AM) or commonly called 3D printing (3DP) and rapid prototyping (RP) is a technique of blending materials by either fusion, binding, or solidifying materials. Despite many advantages of AM, there is a drawback of AM such as the surface quality may not be as good as subtractive machining (SM) process, therefore it will be better to have the initial shape forming process with AM and then finishing the required surface with SM process within a single setup. This paper presents the preliminary design of hybrid AM-SM machine to process a resin based material. The design includes structural design and control design of the machine using the material and firmware widely available in the market.&lt;/p&gt;&lt;p align="center"&gt;&lt;strong&gt; &lt;/strong&gt;&lt;/p&gt;&lt;strong&gt;Keyword: &lt;/strong&gt;Additive, Subtractive, Manufacturing, Hybrid Machine

Design of Traffic Coordination Control Structure Based on Multi-Agent

Urban transport, one of the city’s important infrastructures, which plays an important role in the normal functioning of the city, has become the focus of attention and discussion in the whole society. Restricting to the sustainable development of urban economy, the traditional solution to the urban traffic problems can no longer meet the development requirements of existing urban traffic. Given the complexity of urban transport, the limitations of traditional traffic control methods and the popularization and application of mature artificial intelligence technology, this paper discusses the collaborative framework of traffic control and induction on the base of multi-Agent technology and make researches on the structural design of urban traffic coordination control, thus builds a simulation model for the single intersection. The simulation experiment was carried out by using the Q learning algorithm.

Optimal Multivariable MMC Energy-Based Control for DC Voltage Regulation in HVDC Applications

The penetration of renewable energy resources is changing the way the power system is understood and operated. With an increasing number of power electronics devices integrated into the power system, the modular multilevel converter (MMC) is arising as one of the key technologies for HVDC applications. While several control strategies for MMCs have been proposed in the last years, designing controls for MMCs remains a challenging and non-trivial problem due to its large number of degrees of freedom. In this paper, a general multivariable control structure is proposed that generalizes and improves upon previously reported approaches. Moreover, to fully exploit the degrees of freedom offered by this control, a model-based tuning methodology is presented that extends results from optimal $\mathcal {H}_2$ structured control design to MMC applications. A case study using an HVDC link is used to illustrate and analyze the performance of the MMC using the proposed approach in different scenarios.