Transient 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.

Transient acceleration waveform replication of electro-hydraulic systems using convex combined adaptive controller with input shaping technique

Electro-hydraulic systems are extensively utilized to generate desired acceleration waveforms to provide a vibration environment for testing the performance and reliability of objects in various industrial applications. However, as electro-hydraulic systems are often affected by some inevitable drawbacks resulted from hydraulic nonlinearities, unwanted dynamic variations and disturbances, the generated acceleration waveform is generally far behind the expectation. In this paper, a convex combined adaptive controller with input shaping technique is proposed for enhancing the transient acceleration waveform replication accuracy of electro-hydraulic systems. The proposed controller is comprised of a three variable controller at the bottom level, an input shaping technique controller at the middle level, and a convex combined adaptive controller at the upper level. The three variable controller is firstly utilized for the establishment of a fundamental closed-loop acceleration control system, and then the input shaping technique controller is constructed by introducing an offline designed inverse prefilter utilizing the multi-innovation recursive least squares algorithm and the zero magnitude error tracking algorithm. The convex combined adaptive controller at the upper level is comprised of two individual adaptive filters with high and low step sizes, which provides the merits of fast convergence rate and high tracking accuracy, and it is further exploited to address for system’s dynamic variations, model uncertainties and unexpected perturbations. Comparative experiments of the proposed controller with a manually generated random waveform and a recorded earthquake waveform as the testing inputs are conducted on a typical electro-hydraulic test bench, and the corresponding results demonstrate the feasibility and superiority of the proposed controller in improving the transient acceleration waveform replication performance of electro-hydraulic systems.

Double-loop frame-based adaptive neural sliding-mode control of single-input 3-DOF flexible-joint manipulator

Flexible-joint manipulators (FJMs) have been attracting much attention in recent decades. However, position control and vibration suppression of single-input (SI) multi-degrees-of-freedom (multi( ⩾ 3 )-DOF) FJM is still a high mountain to climb due to the characteristic that some states of such FJMs cannot be directly controlled by the SI. This paper aims to carry out this challenging research. We present a double-loop frame-based adaptive neural sliding-mode control method for an uncertain horizontal SI 3-DOF FJM, i.e. a two-link FJM with only one actuator at the first joint. Since only the actuator angle can be directly controlled, in the inner loop, we design a torque controller so that the actuator angle tracks a time-varying reference actuator angle, designed in real-time by the outer loop. In the outer loop, we consider the reference actuator angle as a virtual control signal and design it based on the dynamic coupling relationships, aiming to indirectly control the first link to its target position and suppress the vibration of both links. Furthermore, to enhance the transient system performance, we plan the input signal of the outer loop (i.e. the target angle) as a smooth reference-trajectory signal. The validity and superiority of this method are demonstrated in simulations.

Energy consumption and feasibility study of a hybrid desiccant dehumidification air conditioning system in Beirut

In this work, the transient performance of a hybrid desiccant vapor compression air conditioning system is numerically simulated for the ambient conditions of Beirut. The main feature of this hybrid system is that the regenerative heat needed by the desiccant wheel is partly supplied by the condenser dissipated heat while the rest is supplied by an auxiliary gas heater. The hybrid air conditioning system of the present study replaces a 23 kW vapor compression unit for a typical office in Beirut characterized by a high latent load. The vapor compression subsystem size in the hybrid air conditioning system is reduced to 15 kW at the peak load when the regeneration temperature was fixed at 75 °C. Also the sensible heat ratio of the combined hybrid system increased from 0.47 to 0.73. Based on hour by hour simulation studies for a wide range of recorded ambient conditions of Beirut city, this paper predicts the annual energy consumption of the hybrid system in comparison with the conventional vapor compression system for the entire cooling season. The annual running costs savings for the hybrid system is 418.39 USD for a gas cost price of 0.141 USD/kg. The pay back period of the hybrid system is less than 5 years when the initial cost of the hybrid air conditioning system priced an additional 1712.00 USD. Hence, for a 20-year life cycle, the life cycle savings of the hybrid air conditioning system are 4295.19 USD.

Fault-Tolerant Consensus of Multiagent Systems With Prescribed Performance.

This article studies the fault-tolerant consensus problem with the guaranteed transient performance of multiagent systems (MASs) subject to unknown time-varying actuator faults and disturbances. The general actuator faults, including both multiplicative and additive time-varying faults, are considered in such a problem for the first time. Both single-integrator modeled agents and double-integrator modeled agents are investigated. The transient performance is ensured in the sense that position errors between each pair of neighboring agents are guaranteed within certain user-defined time-varying performance bounds. Adaptive laws are designed to estimate information about faults and disturbances. For MASs with additive faults, the proposed controllers ensure errors asymptotically converge to zero with guaranteed transient performance. For MASs with both multiplicative faults and additive faults, the proposed controllers ensure errors converge to a residual set without asymptotic convergence but still with guaranteed transient performance. Two simulation examples are provided to evaluate the proposed schemes.

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.

Analysis of grounding system transient with consideration of soil ionization and mutual coupling effect

The grounding system of an electrical substation provides safety to both operator and equipment. The lightning current waveform has a major influence on the dynamic performance of ground electrodes. If lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. Many numerical models have been developed to evaluate the transient performance of grounding system, still it is a challenging task to analyze the impulse behavior of grounding system efficiently. In this paper, the transient behavior of grounding systems with consideration of nonlinear and dynamic effects of soil ionization is presented. Grounding systems such as vertical rod, horizontal conductor and grounding grid buried in the homogeneous soil are considered as case study. Proposed model is the combination of circuit theory approach and method of moment with consideration of frequency-dependent impedance and mutual coupling effect between the conductor segments. Self and mutual component of inductance and resistance are considered in the analysis. Initially, transient performance of grounding system is analyzed for single vertical rod, horizontal and square grounding electrodes, further it is extended for vertical rod (more than one), horizontal conductor and grounding grids with different configurations. The analysis of grounding system with the consideration of mutual coupling effect is compared with devoid of mutual coupling, and differences between them are evaluated. For validating the developed method, simulated results are compared with the results reported in the literature, and good agreements are found. Analysis shows that the grounding impulse impedance decreased with increasing the magnitude of injected current. Developed method will help to improve the modeling of simple as well as complex grounding system buried in homogeneous soil.

Improved Transient Performance of a DFIG-Based Wind-Power System Using the Combined Control of Active Crowbars

A significant electromotive force is induced in the rotor circuit of a doubly fed induction generator (DFIG) due to its high vulnerability to grid faults. Therefore, the system performance must be increased with appropriate control actions that can successfully offset such abnormalities in order to provide consistent and stable operations during grid disturbances. In this regard, this paper presents a solution based on a combination of an energy storage-based crowbar and a rotor-side crowbar that makes the effective transient current and voltage suppression for wind-driven DFIG possible. The core of the solution is its ability to restrict the transient rotor and stator overcurrents and DC-link overvoltages within their prescribed limits, thereby protecting the DFIG and power converters and improving the system’s ability to ride through faults. Further, the capacity of an energy storage device for transient suppression is estimated. The results confirmed that the proposed approach not only kept the transient rotor and stator currents within ±50% of their respective rated values in severe system faults but also limited the DC-link voltage variations under ±15% of its rated value, achieving transient control objectives precisely and maintaining a stable grid connection during the faults.

Compensation function observer-based model-compensation backstepping control and application in anti-inference of quadrotor UAV

This study has considered the dynamical equations of a quadrotor unmanned aerial vehicle (UAV) with model uncertainties, time-varying loads and wind disturbances during actual flight. Then, a model-compensated control idea is innovatively proposed for quadrotor UAV attitude and position tracking control, and a compensation function observer-based model-compensated backstepping controller (CFO-based MC-BC) is designed on this basis. The benefits of this approach arc that the proposed controller not only retains the backstepping control strategy in terms of globally asymptotic stability based on Lyapunov criterion. As well as, a compensation function observer (CFO) with high estimation accuracy is used, which can make excellent use of the system state information to accurately estimate the modeling deviations, parameter variations with time, and external unknown disturbances of the system. And it is incorporated into the controller to dynamically offset this negative impact adaptively. This approach effectively addresses the issue of traditional backstepping control performance relying on modeling accuracy. In addition, this paper introduces a high-order differentiator (HOD) that extracts up to the derivatives of the signal with higher accuracy, effectively solving the issue of “differential explosion”. Finally, a large number of simulation results and experimental validation are presented. The results show that the proposed CFO-based MC-BC is superior than the other four schemes in accurate tracking performance, system transient performance, anti-interference ability, anti-time-varying-load, and unknown information estimation ability.

Neural Network Adaptive Damping Control Strategy for High Speed Elevator Car System with Transient Performance

Aiming at the poor transient convergence and real-time performance of the horizontal vibration state variables of the high-speed elevator car system, and the low control accuracy and stability, this paper proposes an adaptive control strategy to ensure the transient response of the elevator car system. First, a prescribed preset transient performance function is introduced into the controller design to control the variation range of the state variables and ensure the steady transient performance of the elevator car; Second, representing the information of observation error/control error through algebraic operations, designing an adaptive law based on e-correction, estimating unknown parameters in the elevator car system, and achieving online parameter updates; Then, using neural networks to learn and compensate for unknown dynamics in the elevator car system, and solving the online estimation problem of neural network weights through adaptive laws, so that the tracking error and weight estimation error converge to a tight set near zero; Finally, using MATLAB/SIMULINK to compare and analyze the four control algorithms of passive control, PID control, adaptive control based on gradient descent method and transient response adaptive control proposed in this paper under two different rail excitations: Random excitation and pulse excitation. The simulation results show that the adaptive control strategy proposed in this paper effectively suppresses the horizontal vibration of the elevator car, makes the state variables have faster convergence speed and smaller convergence error, and ensures the stable and transient performance of the elevator car system.

Reduced-Order Observer-Based Output-Feedback Tracking Control for Nonlinear Time-Delay Systems With Global Prescribed Performance.

In this article, the output-feedback tracking control problem is considered for a class of nonlinear time-delay systems in a strict-feedback form. Based on a state observer with reduced order, a novel output-feedback control scheme is proposed using the backstepping approach, which is able to guarantee the system transient and steady-state performance within a prescribed region. Different from existing works on prescribed performance control (PPC), the present method can relax the restriction that the initial value must be given within a predefined region, say, PPC semiglobally. In the case that the upper bound functions for nonlinear time-delay functions are unknown, based on the approximate capacity of fuzzy-logic systems, an adaptive fuzzy approximation control strategy is proposed. When the upper bound functions are known in prior, or in a product form with unknown parameters and known functions, an output-feedback tracking controller is designed, under which the closed-loop signals are globally ultimately uniformly bounded, and tracking control with global prescribed performance can be achieved. Simulation results are given to substantiate our method.

Transient discharge performance of high-temperature latent storage system integrated with supercritical CO2 Brayton cycle: A combined analytical and numerical study

In this article, a generalized robust analytical model is developed to evaluate the discharge performance of a high-temperature latent heat storage (HT-LHS) system coupled with the supercritical CO2 (sCO2) recompression Brayton cycle. During discharging, the release of thermal energy from metallic phase change medium (PCM) based HT-LHS is the input to the sCO2 cycle. The thermal efficiency of sCO2 recompression cycle is observed to be significantly larger (> 50 %) than the conventional Rankine cycle at higher operating temperature (700–750 °C). The thermal efficiency increases with turbine input temperature for all split ratios and is maximized at a split ratio of 0.75. Turbine inlet pressure and air temperature are identified as the most and least sensitive parameters to affect the cycle efficiency. The average effectiveness of the LHS considering only conduction is compared with combined conduction and convection in PCM during discharging. The combined effect increases the average effectiveness of LHS maximum by 26.8 %. The analytical model is developed by eliminating two traditional assumptions considered so far in deriving analytical model. The derived dimensionless governing equations are solved using a Python routine to obtain the discharge performance (ε = 0.61,Q = 797.48 kW, ro = 138.61 mm) of LHS.

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.

Predictor-Based Neural Dynamic Surface Control for Strict-Feedback Nonlinear Systems With Unknown Control Gains.

Neural dynamic surface control (NDSC) is an effective technique for the tracking control of nonlinear systems. The objective of this article is to improve closed-loop transient performance and reduce the number of learning parameters for a strict-feedback nonlinear system with unknown control gains. For this purpose, a predictor-based NDSC (PNDSC) approach is presented. It introduces Nussbaum functions and predictors into the traditional NDSC for nonlinear systems with unknown control gains. Unlike NDSC that uses surface errors to update the learning parameters of neural networks (NNs), the PNDSC employs prediction errors for the same purpose, leading to improved transient performance of closed-loop control systems. To reduce the number of learning parameters, the PNDSC is further embedded with the technique of the minimal number of learning parameters (MNLPs). This avoids the problem of the ``explosion of learning parameters'' as the order of the system increases. A Lyapunov-based stability analysis shows that all signals are bounded in the closed-loop systems under PNDSC embedded with MNLPs. Simulations are conducted to demonstrate the effectiveness of the PNDSC approach presented in this article.

A new gains-selection method of depth gauge aided vertical channel for underwater vehicles

The third-order vertical channel damping technique is commonly employed to bound the vertical errors, wherein the selection of the gains is critical for system performance. However, the values of conventional gains-selection based on triple pole placement are determined by a complicated trial-and-error process, which is difficult to directly obtain desired system performance. To address this issue, a new gains-selection method based on classical control theory is proposed. In this method, the dominant pole placement technique is adopted to relate the gains to the damping ratio and natural frequency that have a strict correspondence with system transient performance such as settling time and overshoot in typical second-order system. Therefore, the relationship between the gains and the system transient performance is directly established. Then according to the transient response requirements, the values of the gains can be determined conveniently. Finally, the results of simulation and trial demonstrate the feasibility of this method.

Enhancing transient response performance of automatic voltage regulator system by using a novel control design strategy

Enhancing transient response performance of automatic voltage regulator system by using a novel control design strategy

Research and Improvement of Electromechanical Transient Performance of Power System Based on SIMULINK

The research on electromechanical transient stability of power systems is of great significance. Analyzing the parameters of the simulation system and its improved system with typical short-circuit faults, this paper studies the transient stability of power systems and its improvement. Firstly, based on the SIMULINK of MATLAB, a double-loop simulation with the single-machine-infinite-bus system is built. The simulation experiments of the system under the circumstances of three-phase short circuit and single-phase grounding short circuit faults are then carried out to analyze the parameters such as limit cutting time and voltage. Besides, this paper explores how the controllable series capacitor compensation device and reducing mechanical power output by prime mover improve the transient stability of the system. Experiments show that the stability after fault is under conditions where the fault is removed before the critical clearing time, which can increase the threshold to gain more response time for relay protection devices. Thus, the value of researching and improving system transient stability is proved.

Settling Time Optimization in Wire Bonder Systems via Extremum-Seeking Control1

Adequate tuning of control laws is essential for high positioning accuracy, large system throughput, and reliability in high-end mechatronic and robotic systems. However, a population of such systems generally shows slight variations in dynamic responses due to, e.g., manufacturing tolerances, different disturbance situations, or position-dependent dynamics. Given the time-consuming nature of controller design, even by experienced control engineers, typically just one control law is designed for the whole system population based on worst-case bounds on variations in dynamic responses, resulting in a loss of individual system performance. The main contribution of this paper is the development of an automated controller tuning approach, based on extremum-seeking control, for settling time optimization via individual controller tuning. While other automated controller tuning methods exist, the developed approach allows inclusion of closed-loop stability and robustness constraints based solely on non-parametric frequency-response measurements of open-loop plant dynamics, and therewith directly optimizes transient system performance in a purely data-based manner. The proposed approach has been applied in simulation in an industrial case study for settling time optimization in point-to-point motions of a wire bonder system. In this case study, the effectiveness of the approach has been shown by achieving significant performance increases of 39.4% and 40.6% compared to controllers designed by experienced control engineers using manual loop-shaping techniques and a frequency-based auto-tuner, respectively, without needing manual tuning effort.

Development of two transient models for predicting dynamic response characteristics of an automobile thermoelectric generator system

In this work, two transient models, including a transient fluid-thermal-electric multiphysics numerical model and a hybrid transient CFD-analytical model, are proposed to predict the dynamic performance of the automobile thermoelectric generator system in practical applications. The transient models consider the heat source fluctuation, temperature dependence of thermoelectric materials, and the coupling of different physical fields, which can simulate the actual working conditions. According to the model results, the dynamic output power varies smoothly and is mainly related to the exhaust temperature due to thermal inertia, whereas the dynamic conversion efficiency fluctuates sharply and is mainly related to the exhaust mass flow rate. Compared with the transient fluid-thermal-electric multiphysics numerical model, the output performance obtained by the hybrid transient CFD-analytical model is overestimated, especially for conversion efficiency, and the average errors of output power and conversion efficiency between the two models are 2.90% and 13.58% respectively. Besides, the output performance predicted by transient models is lower than that expected in a steady-state analysis, and the transient models are experimentally verified. This work fills the gap of theoretical models for predicting the dynamic response characteristics, and the findings are helpful to understand the transient performance of automobile thermoelectric generator systems.

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.