Steady-state Performance Of System Research Articles

Fixed-time second-order sliding mode output feedback trajectory tracking control for an autonomous surface vehicle with model uncertainties and prescribed performance

This paper investigates the fixed-time trajectory tracking control problem of autonomous surface vehicle system with asymmetric performance constraints. The external disturbances, model uncertainties and the difficulty of velocity measurement are all taken into account in the controller design. Asymmetric performance constraints are firstly studied to improve the transient and steady-state performance of the tracking error system. Next, a fixed-time extended state observer is developed to estimate the unknown velocity and external disturbances. Both the fixed-time first-order and the second-order PID-type sliding surfaces are designed. Further, two continuous output feedback controllers are built to achieve high control accuracy and low energy consumption and to achieve fixed-time stability of the closed-loop system. Finally, abundant simulations for CyberShip II demonstrate the effectiveness of the proposed algorithms.

Prescribed Performance Control for Teleoperation System of Nonholonomic Constrained Mobile Manipulator Without Any Approximation Function

The teleoperation system of mobile manipulator has been widely applied for space exploration, medical assistance, and other fields. To improve operational efficiency, this paper presents a novel prescribed performance synchronization control scheme without applying any approximation functions for a class of teleoperation system of the mobile manipulator with time-varying delays and nonholonomic constraints. Compared with the general manipulator system, the mobile manipulator has a larger workspace and stronger operability. Yet, the heterogeneity of master-slave robots and the nonholonomic constraint of slave robot bring many difficulties to the control of the system. Firstly, a prescribed performance function (PPF) is designed to guarantee that the position synchronization errors are remained within the predetermined boundary and converge to a small preset area within a preset time. Then, the direct force feedback information is introduced into the controller to improve the transparency of the teleoperation. In addition, there are no approximation functions applied in the proposed controller, which can significantly reduce the complexity and computation of the system. Finally, simulation and experimental results are made to illustrate the availability of this method for practical application. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The motivation of this paper is to develop an algorithm to improve the steady-state and transient-state performance of mobile manipulator teleoperation system without increasing the complexity of the controller. Compared with the existing works, in this paper, the control algorithm without any approximators is proposed and a time-varying prescribed performance function is introduced, which promotes the steady-state and transient-state performance of the system essentially. At the same time, the introduction of force feedback information improves the transparency of the teleoperation system. The feasibility and effectiveness of the algorithm are verified on UR5e-Husky experimental platform. In the future, we will strive to further improve the transparency of the mobile manipulator teleoperation system in order to achieve the immersive effect of operator.

Performance Evaluation of Distribution System Interconnected with Solar PV Plants Using DIgSILENT

Many African countries, such as Botswana, receive high insolation that can be used to generate electricity. However, they still rely on thermal power generation and imports from neighbouring countries through various African power pools. Thermal generation methods result in an increase in carbon footprint. Therefore, in pursuance of the global climate change goals, the Government of Botswana has subscribed to allow all end users with the capacity to install solar rooftops and sell extra electricity to the power utility. These interconnections of solar PV plants to the grid are bound to bring challenges to the steady state system performance. This research, therefore, evaluates the performance of the integrated system focusing on the greater Gaborone distribution system (GGDS), where five government projects are being piloted. The study has adopted two scenarios by providing a performance comparative analysis between the system baselines to a solar integrated system using DIgSILENT Power Factory software. The system studies conducted include power flow, effects on voltage and line loading. This research found out that integrating PV plants to GGDS distribution network improves voltage profiles and a decrease in overall percentage loading of the feeders and interconnectors. However, some notes could only permit a limited loading. In conclusion, the implications of the effects of solar PV on the distribution system differ from one circuit to another; therefore, it calls for utilities to conduct an intensive network assessment for each particular feeder before interconnecting with solar.

Transient response feedback control for horizontal vibration of high-speed elevator car with prescribed performance

The high-speed elevator car is subject to violent horizontal vibration due to the wind pressure generated by the ventilation hole of the elevator rapid operation, improper adjustment of the gap and steps at the joint of the elevator car guide rail, pitting corrosion or wear on the guide surface of the guide shoe, inadequate installation and adjustment of the guide shoe or guide rail and so on. Aiming at the problems of poor transient convergence and real-time performance, low control accuracy and stability of the existing active control algorithm for the horizontal vibration control variables of the elevator car system, a transient response feedback control strategy with specified performance is proposed in this paper. Firstly, a six degree of freedom elevator car system model is established, and the state space equation is constructed based on the linear fractional transformation algorithm; Secondly, a class of preset transient performance function is introduced to construct the convergence boundary in advance to ensure that the system control variables are strictly constrained within this boundary, and the stability of the transformed variables is ensured by equivalent transformation; Finally, four different control methods including passive control, H2/H∞ control, PID control and transient response feedback control proposed in this paper are compared and analyzed by using MATLAB under two typical guideway excitation. The simulation results show that the proposed transient response feedback control strategy reduces the root mean square value and maximum value of the horizontal displacement acceleration of the elevator car system by more than 81%, effectively suppresses the horizontal vibration of the elevator car, and ensures the transient and steady-state performance of the elevator car system.

Artificial Intelligent Maximum Power Point Controller based Hybrid Photovoltaic/Battery System

Photovoltaic (PV) cells have non-linear properties influenced by environmental factors, including irradiation and temperature. As a result, a method known as maximum power point tracking (MPPT) was implemented to boost the PV cells' efficiency and make the most of the energy they could provide. The traditional perturb and observe (P&amp;amp;O) approach for determining the maximum power point tracking (MPPT) has various drawbacks, including poor steady-state performance, increased oscillation around the MPP point, and delayed reaction. As a result, this work aims to present a hybrid fuzzy logic (FL) and P&amp;amp;O MPPT approach to improve the PV system's performance coupled to the lithium battery storage system. Matlab/Simulink is used to bring the suggested technique to life, after which its efficacy is evaluated in the context of rapid changes in the irradiance level. According to the findings of the simulations, the suggested strategy has the potential to enhance the steady-state performance of PV systems in terms of oscillation and time response. Finally, the proposed results are compared with that obtained by the conventional P&amp;amp;O technique, and the stress of PV power is limited to ∆P=1kW and the overshoot power is limited to 5%.

Enhanced Dual–Vector Model Predictive Control for PMSM Drives Using the Optimal Vector Selection Principle

The Dual–Vector model predictive control (DV–MPC) method can improve the steady–state control performance of motor drives compared to using the single–vector method in one switching cycle. However, this performance enhancement generally increases the computational burden due to the exponential increase in the number of vector selections, lowering the system’s dynamic response. Alternatively, limiting the vector combinations will sacrifice system steady–state performance. To address this issue, this paper proposes an enhanced DV–MPC method that can determine the optimal vector combinations along with their duration time within minimized calculation times. Compared to the existing DV–MPC methods, the proposed enhanced technique can achieve excellent steady–state performance while maintaining a low computational burden. These benefits have been demonstrated in the results from a 2.5k rpm permanent magnet synchronous motor drive.

Saturation-tolerant prescribed function-based adaptive fault-tolerant tracking control for ACV with uncertainty and faults

This paper presents an adaptive fault-tolerant control system for Trajectory tracking of air-cushioned vehicles (ACVs) in the presence of actuator saturation, internal and external system perturbations. The proposed approach utilizes a state observer to estimate and compensate for the disturbances and saturation fault information present in the tracking system of the ACV. To achieve the desired performance, a new prescribed performance function (PPF) is introduced that is both global and saturated-tolerant. The PPF ensures that the error converges to a predetermined function in fixed time for any initial value, although it weakens the limits on the amount of overshoot. The combination of the observer and PPF with a backstepping fault-tolerant controller leads to improved transient and steady-state performance of the tracking control system for ACV. Simulation results demonstrate the effectiveness of the proposed approach.

Planning ride-pooling services with detour restrictions for spatially heterogeneous demand: A multi-zone queuing network approach

This study presents a multi-zone queuing network model for steady-state ride-pooling operations that serve heterogeneous demand, and then builds upon this model to optimize the design of ride-pooling services. Spatial heterogeneity is addressed by partitioning the study region into a set of relatively homogeneous zones, and a set of criteria are imposed to avoid significant detours among matched passengers. A generalized multi-zone queuing network model is then developed to describe how vehicles’ states transition within each zone and across neighboring zones, and how passengers are served by idle or partially occupied vehicles. A large system of equations is constructed based on the queuing network model to analytically evaluate steady-state system performance. Then, we formulate a constrained nonlinear program to optimize the design of ride-pooling services, such as zone-level vehicle deployment, vehicle routing paths, and vehicle rebalancing operations. A customized solution approach is also proposed to decompose and solve the optimization problem. The proposed model and solution approach are applied to a hypothetical case and a real-world Chicago case study, so as to demonstrate their applicability and to draw insights. Agent-based simulations are also used to corroborate results from the proposed analytical model. These numerical examples not only reveal interesting insights on how ride-pooling services serve heterogeneous demand, but also highlight the importance of addressing demand heterogeneity when designing ride-pooling services.

A Comprehensive Review and Analytical Comparison of Non-Isolated DC-DC Converters for Fuel Cell Applications

The use of renewable energy sources such as solar photovoltaic, wind, and fuel cells is becoming increasingly prevalent due to a combination of environmental concerns and technological advancements, as well as decreasing production costs. Power electronics DC-DC converters play a key role in various applications, including hybrid energy systems, hybrid vehicles, aerospace, satellite systems, and portable electronic devices. These converters are used to convert power from renewable sources to meet the demands of the load, improving the dynamic and steady-state performance of green generation systems. This study presents a comparison of the most commonly used non-isolated DC-DC converters for fuel cell applications. The important factors considered in the comparison include voltage gain ratio, voltage switch stress, voltage ripple, efficiency, cost, and ease of implementation. Based on the comparison results, the converters have been grouped according to voltage level applications, with low voltage applications being best served by converters such as DBC, DuBC, TLBC, 2-IBC, 1st M-IBC, PSOL, SEPIC, and 1st M-SEPIC owing to their lower cost, smaller size, and reduced switch stress. Medium voltage applications are best suited to converters such as TBC, 1st M-TLBC, 2nd M-TLBC, 4-IBC, 1st M-IBC, 2nd M-IBC, 1st M-PSOL, 2nd M-PSOL, 1st M-SEPIC, and 2nd M-SEPIC, which offer higher efficiency. Finally, high voltage applications are best served by converters such as TBC, 1st M-TBC, 2nd M-IBC, 3rd M-IBC, 3rd M-PSOL, 4th M-PSOL, 2nd M-SEPIC, 3rd M-SEPIC, and 4th M-SEPIC.

Short-circuit analysis of grid-connected PV power plants considering inverter limits

This paper presents a short-circuit analysis of grid-connected photovoltaic (PV) power plants, which contain several Voltage Source Converters (VSCs) that regulate and convert the power from DC to AC networks. A different methodology has been adopted in this paper for short-circuit calculation. In particular, an element-based formulation is adopted to model the studied system including the grid-support control and various current-saturation states of PV inverters during the fault. An iterative approach is presented to identify the short-circuit equilibrium point that satisfies all converters’ operation limits efficiently. Case studies have been carried out on PV power plants with different numbers of inverters. The influence of the inverter grid-support operation, the main grid strength and the MV collection grid topology on system steady-state performance during the fault has been analyzed. The obtained short-circuit equilibrium points have been validated through dynamic simulations.

Modeling and Analysis of Stochastic Perishable Inventory System with Impatient Customers at Service Facility

In this paper, we consider a two‐commodity stochastic (s, S) perishable inventory system of the multiqueue Jackson network at a service facility with reneging and jockeying of the customers. The waiting room capacity of the first queue is M/M/1/∞ and the second queue is M/M/1/C2, where C2 &lt; ∞. In this network, different queues have different service rates. Service times are exponentially distributed. Customers join the system at a rate of λi; (i = 1,2) using a Poisson process. We assumed that some customers maybe impatient due to the long waiting time in the queue and can leave the system without service or may switch from the longest queue to the shortest queue to reduce the waiting time. If the inventory levels of the items from the warehouse i at any time reaches below or reorder level si, an order Qi = ((Si − si) &gt; 0; i = 1,2) units is placed to bring the inventory level up to Si. The joint probability distribution of the number of customers in the system and also the stock level of the warehouse is determined in the equilibrium case. Several important measures of steady‐state system performance are derived. Several examples are presented to demonstrate the reneging and jockeying behavior of the customers for this system. A sensitivity analysis is performed to investigate the effect of changing the parameters on the total expected cost of the system.

Optimized control strategy for single-phase multilevel cascaded converter in a distributed PV-BESS system

The paper focuses on the energy management of a single-phase PV-BESS hybrid distributed system sized for residential applications, using a CHB converter topology as grid interface. The CHB is driven with a hierarchical energy management architecture, with a single centralized controller for the upper layer, and with multiple decentralized controllers for the lower layer. The upper layer generates the reference signals to be tracked. In ideal conditions, the CHB should work with all PV modules at their MPP and with unitary power factor. This is not always possible because of some functional constraints (e.g., voltage/current constraints, partial shadowing, SoC mismatches). Therefore, a weighted sum optimization method is proposed to explicitly considers these effects and to compute a set of reference variables to be tracked, in a way to optimize the steady-state system performances while, at the same time, guaranteeing the respect of the aforementioned constraints. In this framework, different functional requirements have been included in the optimization algorithm with higher or lower priority according to different operating conditions. The optimal references are then tracked by a decentralized control layer, using standard feedback control techniques. Numerical analysis and experimental results are carried out in order to validate the optimal algorithm in typical operating conditions and to assess the effectiveness of proposed CHB configuration with the whole control strategy.

Two-commodity perishable inventory system with partial backlog demands.

This article examines a two-commodity continuous review perishable inventory system. The demands are arrived at for each product by independent Markovian arrival processes (MAP). Lifetimes follow an exponential distribution. The commodities are assumed to be substitutable. If both commodities have reached zero, demand is backlogged up to predetermined levels. This article’s novelty has been a local purchase, which is made to clear the backlog instantaneously when demand reaches a predetermined level. In the steady-state, the joint probability distribution of inventory levels of both commodities is obtained. Several metrics of system performance in steady-state are derived and also provided as numerical examples to explain the optimum values of the system’s parameters.

Finite-Time Control of High-Speed Train With Guaranteed Steady-State and Transient Performance

With considering the inevitable factors of input nonlinearity, aerodynamic resistance, in-train force, external disturbance and unknown actuator failures, this paper investigates the position/velocity finite-time tracking control problem of high-speed train (HST) to improve the steady-state (tracking accuracy) and transient performance (overshoot and settling time) of the traction/braking control system. Since the traction/braking control system of HST requires rapid reaction speed to ensure the safe and reliable operation, an integer-order finite-time controller (IO-FTC) is developed firstly by utilizing finite-time control theory to improve the system transient performance. On the basis of ensuring the system transient performance, a fractional-order finite-time controller (FO-FTC) is designed by using the fractional stability principle and fractional integral to further improve the system steady-state performance and its robustness and anti-jamming capability. It should be noted that both IO-FTC and FO-FTC are essentially independent of the system model and can produce proper traction/braking force with only the actual and desired position/velocity of the leading vehicle. And the settling time of the system can be adjusted through the selection of different control parameters. The feasibility and effectiveness of the designed controllers are verified by theoretical analysis and simulation studies. And the developed methods are compared with the PID controller. Simulation results make it clear that the proposed methods are superior to PID.

Adaptive Control Method of Sensorless Permanent Magnet Synchronous Motor Based on Super-Twisting Sliding Mode Algorithm

To solve the problem of the sensorless control method of a permanent magnet synchronous motor, based on the study of a mathematical model for a permanent magnet synchronous motor and model adaptation theory, a reference model equation and adjustable model equation are derived according to the stator current equation. The correctness of the selected linear compensator matrix is strictly proved. Then, Popov’s super-stability theory is used to derive the speed adaptive law and prove its asymptotic stability. Based on the voltage closed-loop feedback MTPA weak magnetic control strategy, a simulation model of a MRAS control system based on stator current is built and combined with the principle of MRAS. Aiming to investigate the problem that the PI adaptive law in the traditional MRAS algorithm is not robust, super-twisting sliding mode control is introduced to replace the PI adaptive law. The observer based on STSM−MRAS is designed. The simulation model of the MRAS control system based on the super-twisting sliding mode is established. Under certain working conditions, the STSM−MRAS algorithm and the traditional MRAS algorithm are simulated and compared. The results show that the STSM−MRAS algorithm can improve the steady-state performance and robustness of a sensorless control system.

Online Control of Smart Inverter for Photovoltaic Power Generation Systems in a Smart Grid

The main purpose of this study is to engage in research on a grid-connected photovoltaic (PV) power generation system smart inverter. The research content includes a smart maximum power point tracking (MPPT) controller and an inverter with power regulation. First, use the PSIM software package to establish the simulation environment of the grid-connected photovoltaic power generation system and use the Sanyo HIP-186BA19 photovoltaic module to form a 744 W system for simulation. In order to enable the photovoltaic module array (PVMA) to output the maximum power under different solar insolation and ambient temperature, the architecture is based on the extension theory-based smart MPPT method to improve the dynamic response and steady-state performance of photovoltaic power generation systems compared to perturb and observed (P&amp;amp;O) MPPT. When the sunshine is 1,000 W/m2, the photovoltaic power generation system adopts the extension theory-based maximum power tracking method. The time required to track the maximum power point is only 0.32 s, and the steady-state ripple is only 4.127 W. However, using the traditional P&amp;amp;O method requires 0.741 s to track the maximum power point, and the steady-state ripple reaches 18.131 W. Thus, the dynamic response speed of the maximum power tracking method proposed is 50% faster than that of the P&amp;amp;O method. The steady-state performance is also better compared to the P&amp;amp;O method. At the same time, a simple proportional-integral (PI) controller is used to regulate the DC-link voltage, output voltage, and current of the inverter to make the voltage of the grid-connected point stable at an effective value of 220 V. Then, the voltage-power control technology is added to the photovoltaic grid-connected inverter, and a simple proportional-integral controller is used to regulate the output of the smart inverter reactive power to improve the power quality of grid voltage. Finally, simulation and experimental results are used to verify the effectiveness of the regulation performance of the developed smart inverter.

Numerical study of a heat-driven thermoacoustic refrigerator based on a time-domain lumped acoustic–electrical analogy model

Thermoacoustic technology is a promising clean energy solution for the recovery of low-grade heat from renewable energy sources and waste heat. Existing methods for simulating thermoacoustic systems are inconsistent or time-consuming. In this study, a time-saving and reliable time-domain lumped acoustic–electrical analogy model is proposed to investigate the performance of thermoacoustic systems. In the proposed model, each component of a thermoacoustic system is simplified as a lumped acoustic–electrical analogy model. The nonlinear effects of both regenerator and liquid acoustic resistances in gas–liquid resonators are considered to obtain nonlinear dynamic evolution equations. Case studies were performed on a looped heat-driven thermoacoustic refrigerator for low-grade heat recovery to investigate its onset and steady characteristics. The evolutions of the oscillating pressure and volume flow rate were explored, which initially increase rapidly until reaching the saturation state. The minimum onset temperature was 32.5 K at a pressure of 2.5 MPa with hydrogen as the working gas. In addition, the influences of the mean pressure, heating temperature, and cooling temperature on the steady-state system performance with various working fluids were investigated. The results indicated that the cooling power increased significantly with increasing mean pressure, heating temperature, and cooling temperature. A higher working liquid density resulted in a lower onset temperature, lower working frequency, and larger pressure ratio. With the use of helium or hydrogen, the refrigerator performed better in terms of a lower onset temperature and a larger pressure ratio, cooling power, and coefficient of performance. The proposed model provides a new perspective and an effective approach to characterise the onset and steady characteristics of thermoacoustic systems.

Non-fragile Fuzzy Control for Fractional-order Unified Chaotic Systems

The fuzzy control of fractal-order chaotic systems are studied. Firstly, according to the T-S fuzzy modeling theory, the fractional order unified chaotic system is reconstructed by T-S fuzzy modeling. Secondly, the steady-state performance of Fractional-order unified chaotic systems is discussed by using Lyapunov stability theory. Then, a Fractional-order Non-fragile fuzzy controller is designed according to the linear matrix inequality (LMI) method. Finally, a simulation example is given to verify the effectiveness of the controller.

Sampled-data extremum-seeking framework for constrained optimization of nonlinear dynamical systems

Most extremum-seeking control (ESC) approaches focus solely on the problem of finding the extremum of some unknown, steady-state input–output map, providing parameter settings that lead to optimal steady-state system performance. However, many industrial applications also have to deal with constraints on operating conditions due to, e.g., actuator limitations, limitations on tunable system parameters, or constraints on measurable variables. In particular, constraints on measurable variables are typically unknown in terms of their relationship with the tunable system parameters. In addition, the constraints on system inputs as a result of the constraints on measurable variables may conflict with the otherwise optimal operational condition, and hence should be taken into account in the data-based optimization approach. In this work, we propose a sampled-data extremum-seeking framework for the constrained optimization of a class of nonlinear dynamical systems with measurable constrained variables. In this framework, barrier function methods are employed, exploiting both the objective function and constraint functions which are available through output measurement only. We show, under the assumption that the parametric initialization yield operating conditions that do not violate the constraints, that (1) the resulting closed-loop dynamics is stable, (2) constraint satisfaction of the inputs is guaranteed for all iterations of the optimization process, and (3) constrained optimization is achieved. We illustrate the working principle of the proposed framework by means of an industrial case study of the constrained optimization of extreme ultraviolet light generation in a laser-produced plasma source within a state-of-the-art lithography system.

High-Order Fast Nonsingular Terminal Sliding Mode Control of Permanent Magnet Linear Motor Based on Double Disturbance Observer

In order to realize the high-speed and high-precision movement of the direct drive system, it is important to study the strong robust control strategy of permanent magnet linear synchronous motor (PMLSM) servo system. This article proposes a high-order fast nonsingular terminal sliding mode control strategy for PMLSM based on double disturbance observer. The double disturbance observer is used to observe the mismatched/matched disturbances to reduce the conservativeness of the system to multiple disturbances. In addition, a high-order fast nonsingular terminal sliding mode controller is designed to enhance the robustness of the system. By adding feedback current into the controller, the overall control of current, speed, and position is realized. In addition, the steady-state performance and dynamic performance of position tracking system are improved. The stability and convergence of the closed loop system are proved by the Lyapunov stability theory. Experimental results show that the proposed strategy can effectively improve position tracking accuracy of the system and robustness to uncertain disturbances.