Time Delay Compensation Research Articles

Seismic Response Mitigation of Extra-Large LNG Storage Tanks

The paper investigates the effectiveness of a smart base-isolation system for seismic response mitigation of extra-large liquified natural gas (LNG) storage tanks. The mathematical model of the base-isolated LNG tank with smart dampers, the magneto-rheological (MR) dampers, is presented. The governing equations of motion of the smart system are derived and solved by the classical transition matrix method in the time domain. The linear quadratic regulator (LQR) control scheme is employed to command MR dampers. The LNG tank system is analyzed under six artificial accelerograms, compatible with operational basis earthquake (OBE) and safe shutdown earthquake (SSE) response spectrum, generated using a method of a random set of phase angles with amplitudes obtained from power spectral density function. A time-delay compensation procedure based on the Taylor series expansion is applied to reduce the deterioration of control performance due to time delay. To investigate the effectiveness of smart base-isolation, the responses are compared with the fixed-base tank, base-isolated tank, and tank with passive MR damper. The results show that the smart base-isolation is effective in reducing the seismic response of extra-large LNG tanks, especially the displacement at the isolation level without much altering other responses. The passive MR damper is also found effective and showed fail-safe behavior even under the failure of the control algorithm. Moreover, the application of time-delay compensation using the Taylor series increased the performance and overall efficiency of the LNG tank system.

A receptance-based vibration control with dead-zone compensation for systems with input delay

This paper presents a novel compensation approach for receptance-based second-order systems with long input delay and unknown dead-zone input nonlinearity. The approach is based on a filtered Smith predictor for systems with long input delay based on the receptance model. An innovative discrete-time adaptive strategy approach for dealing with unknown input dead-zone is also based on a receptance model realization. The receptance-based second-order model is used on several fundamental applications, including active control vibration of mechanical vibrating systems. In the proposed approach, a filtered prediction error that considers the effects of time delay can be applied to pursue state feedback design for active vibration control purposes. The dead-zone compensation is treated by a discrete-time state observer, which is based on displacement, velocity, and control effort signals to estimate the unknown parameters to be used on an adaptive algorithm. The main contribution of this work is to combine unknown dead-zone adaptive mechanism and a receptance-based time delay compensation in a unified design. Some numerical examples illustrate the effectiveness of the innovative proposed approach.

Real-Time Distributed Cooperative Adaptive Cruise Control Model Considering Time Delays and Actuator Lag

Real-time control of a fleet of Connected and Automated Vehicles (CAV) for Cooperative Adaptive Cruise Control (CACC) is a challenging problem concerning time delays (from sensing, communication, and computation) and actuator lag. This paper proposes a real-time predictive distributed CACC control framework that addresses time delays and actuator lag issues in the real-time networked control systems. We first formulate a Kalman Filter-based real-time current driving state prediction model to provide more accurate initial conditions for the distributed CACC controller by compensating time delays using sensing data from multi-rate onboard sensors (e.g., Radar, GPS, wheel speed, and accelerometer), and status-sharing and intent-sharing data in BSM via V2V communication. We solve the prediction model using a sequential Kalman Filter update process for multi-rate sensing data to improve computational efficiency. We propose a real-time distributed MPC-based CACC controller with actuator lag and intent-sharing information for each CAV with the delay-compensated predicted current driving states as initial conditions. We implement the real-time predictive distributed CACC control algorithms and conduct numerical analyses to demonstrate the benefits of intent-sharing-based distributed computing, delay compensation, and actuator lag consideration on string stability under various traffic dynamics.

Experimental investigations on the semi-active control of a valve-driven secondary lateral damper for a high-speed rail vehicle

Passive suspensions cannot sufficiently reduce vehicle vibrations on tracks with poor irregularities or when the vehicle was operated at higher speeds. This study proposes three semi-active control algorithms for a secondary lateral damper to enable the vehicle to be operated on high-speed dedicated railways at 350 km/h and conventional low-speed railways at 160 km/h. A high-speed rail vehicle dynamics model with controllable dampers is built to study the feasibility of those algorithms through numerical investigations. Then, both field tests on track and lab tests on a full-scale roller rig were performed to examine the functionality of the controller hardware system and the valve-driven semi-active damper. Furtherly, a time-delay compensation based on the signal amplitude is developed and verified. Results from the on-track and roller rig tests state that the proposed semi-active control algorithms and the designed control system can effectively improve the ride quality of the vehicle when it is put into operation in different track conditions and at various speeds.

A continuous underwater bubble localization method using passive acoustic array beamforming

The bubble is an effective carrier of underwater gas leakage detection, and its rapid localization is of great significance. In this paper, a continuous underwater bubble localization method using passive acoustic array beamforming is proposed. A specific array of hydrophones was constructed to capture the bubble acoustic signal. The signal of finite length is obtained by introducing the time window. Then, the time delay compensation is carried out according to the positions of the hydrophones in the array to estimate the direction of arrival. The influence of shape, number, and aperture of the hydrophone array on the algorithm performance is studied by simulation. Moreover, the experiment was carried out in a cuboid transparent tempered glass water tank in the laboratory, and a field programmable gate array is used as the core control unit of the data processing system to complete the signal acquisition and the algorithm execution. The localization results show that the passive acoustic cross array beamforming algorithm can accurately and stably estimate the leakage direction at different positions.

EXTREMUM SEEKING BASED COMPOSED RECURSIVE MODEL FREE CONTROL OF TWO-STAGE ANAEROBIC DIGESTION PROCESS

In this paper, a new structure of extremum seeking algorithm is applied to the two-stage anaerobic digestion process to maximize the outflow rate of both hydrogen and methane. The model of the two-stage AD process is presented, which provides the characteristics of the total gas production rate. Based on the original Extremum Seeking Control (ESC), a novel Composed Recursive Model Free Controller (CRMFC) is added for maximum tracking for the gas production in the bioreactors. The proposed controller comprises a recursive model free stabilization term and a recursive time delay compensation term. Standard ESC, Newton-based ESC and Kalman filter (KF) based ESC are respectively combined with the new model-free controller to verify the proposed structure. Numerical simulations illustrate the performance of the proposed controller.

고 해상도 버퍼 설계를 통한 전달 정렬의 측정치 시간 지연 보상 기법

In this paper, we propose a time delay compensation method for transfer alignment using a high-resolution buffer design. Time delay degrades the performance of transfer alignment, resulting in subsequent mission failure. The value of such a time delay may not be constant and varies indefinitely depending on the system configuration or operating environment, which reduces the time delay estimation performance using general Kalman filtering. Using a state buffer is one of the methods to solve this problem. This paper presents a new time delay estimation method using a time delay candidate buffer. The proposed scheme can finely set the interval of time delay candidates and does not require a separate memory. In addition, a method for designing an appropriate time delay candidate buffer interval according to the activation of a vehicle and the performance of the MINS is presented. Simulations verified that the proposed technique could reduce the memory requirement and improve the transfer alignment performance for finely changing the time delay.

Broadband Time-Delay and Chirp Compensator for X-ray Pulses

A new type of aberration-corrected time-delay compensating monochromator (TDCM) for soft X-rays is presented. Composed of two identical reflection zone plates (RZPs) on spherical substrates and an intermediate flat mirror for band-pass selection, the TDCM can operate in a wide energy range of about ±20% around the design energy of 410eV. Assuming a source size of 50μm and an angular acceptance of 1 mrad, the spectral resolving power may reach 6×102, at a pulse length as short as 4.3femtoseconds(fs). In the case of μm-sized sources, the resolution can be better than 0.1eV and the sub-fs regime could become accessible. The overall transmission efficiency varies within (4.2–6.0)% across the energy range (310–510) eV. In the complementary mode, chirped-pulse compression works as well. Depending on the properties of the source, simulations predict an up to 9-fold reduction in pulse duration, whereas ≤50% of the peak intensity is maintained.

Analysis of LoRa Transmission Delay on Dynamic Performance of Standalone DC Microgrids

One important aspect toward proper and stable functioning of a communication-based controlled microgrid is data transmission. Consequently, an analysis of the effect of data transmission delay is of significance for any chosen communication protocol. This paper focuses on the effect of employing LoRa for data transfer at the secondary control level of a standalone DC microgrid. It analyses the effect of LoRa transmission delay on the dynamic performance of DC microgrids. This paper simulates a community DC microgrid that operates in three modes: PV mode, battery mode and generator mode. This microgrid operates as a centralized communication-based controlled microgrid, with the secondary control level operating as an event-driven level. The system incorporates a hierarchical system where data is transferred between the various distributed energy resources (DERs) local controllers and the microgrid central controller (MGCC). Simulations for three scenarios are presented. In the first scenario, the microgrid is designed and simulated without a communication delay to observe the system behavior. Then LoRa transmission delay is calculated for the various signals transferred between the MGCC and the local controllers. This delay is introduced into the simulation as transport delays and the system exhibits a level of stability degradation. Subsequently, a time delay compensation system is incorporated into the system for more robust operation. The delay compensation is applied in two simulation scenarios. In the first scenario, the system inductor (L) and capacitor (C) components are re-calculated, and the system is re-simulated to get a stable system even with the applied communication delay. In the second scenario, the proportional integrator (PI) controller in the microgrid central controller is re-designed to a more robust form to compensate for the delay caused by the LoRa transmission. The results obtained from the two modified simulations realize a stable DC microgrid. This system modification allows for system stability again, similar to the simulation when the microgrid operated without any communication delay. This, therefore, demonstrates that with proper system design and implementation, low bandwidth communication systems such as LoRa can be effectively employed for data transfer in event-driven communication-based controlled DC microgrids.

Recursive Predictive Optimal Control Algorithm for Real-Time Hybrid Simulation of Vehicle–Bridge Coupling System

Real-time hybrid simulation (RTHS) is recently applied to study the vibration of the vehicle–bridge coupling system, where bridges and the vehicle are the numerical and experimental substructures respectively. Inevitable time delay of the boundary loading imposed to the experimental substructure will greatly affect the accuracy and stability of RTHS. To minimize the time delay effects, this paper proposes a recursive prediction optimal (RPO) compensator based on optimal control and recursive least squares. The numerical simulation of the RTHS of the vehicle–bridge coupling system is conducted using MATLAB/Simulink. The performance of the RPO method is compared with three traditional time delay compensation methods (i.e. the polynomial extrapolation (NI), the inverse compensation (IC) and the derivative feedforward (DF)) through both open-loop and RTHS simulations. The RPO method shows the best compensation performance in the frequency range up to 20[Formula: see text]Hz.

Nonlinear ESO-based vibration control for an all-clamped piezoelectric plate with disturbances and time delay: Design and hardware implementation

Considering the problems of model uncertainties, higher harmonics, uncertain boundary conditions, external excitations, and system time delay in practical vibration control system, a novel active vibration control method is proposed to suppress the vibration of a thin plate structure with acceleration sensor and piezoelectric bimorph actuator in this paper. First, a nonlinear extended state observer (NESO)-based controller is designed to ensure the anti-disturbance performance of the structural vibration control system. Then, an enhanced differentiator-based time delay compensation method is introduced to improve the vibration suppression performance of the NESO-based controller. A real time hardware-in-the-loop benchmark for an all-clamped piezoelectric thin plate is designed to verify and compare the performance of the developed controller against conventional ESO-based methods (linear ESO with/without time delay compensation, NESO without time compensation). The best vibration suppression and disturbance rejection performance of the proposed NESO-based controller with an enhanced time delay compensator is verified in the comparative experimental results. This work is able to provide practitioners with vital guidance in designing active vibration control system in the presence of disturbances and time delay.

Active Tendon Control of Stay Cable by a Giant Magnetostrictive Actuator Considering Time-Delay

Active control of a stay cable through changing its tension is an effective way to lower the vibration amplitude. In this paper, active tendon control of a stay cable using a giant magnetostrictive actuator (GMA), which can generate axial deformation in a short period (normally less than 10 ms) under magnetic fields, is studied considering the time-delay. The bilinear controlled state equation of the small-sag cable is established by employing the Lagrange formulation. The linearization method for the bilinear controlled state equation is proposed and validated by numerical simulations. A GMA is designed and manufactured to actively control a stay cable model and the relationship between the output force and the input voltage is obtained by experiments. Based on the phase-shifting method, a multi-mode control algorithm with the time-delay compensation is proposed, and the time-delay compensation matrix based on the state feedback control algorithm is obtained. Based on a 1:20 scaled cable model, simulations and experiments are conducted to investigate the control performance of the proposed method under different external loads including the free vibration, harmonic excitation and random excitation. The results show that the tendon control of cable vibration by a GMA may be invalid and even amplify the vibration amplitude when the compensation of time-delay is not considered. Moreover, the excellent control performance can be achieved by using the proposed time-delay compensation method.

Integral Sliding Mode Control Based Deadbeat Predictive Current Control for PMSM Drives With Disturbance Rejection

To promote the control performance of the modern high-precision permanent-magnet synchronous motor (PMSM) system on the existence of the time-delay and parameter mismatch, an improved deadbeat predictive current control (DPCC) method is proposed in this article. First, the conventional DPCC method considering the time-delay compensation is introduced. Along with this method, the negative influence on the control performance when the parameter mismatch occur is analyzed mathematically. Afterward, this article proposes a novel compensation scheme based on the integral sliding mode control (ISMC) theory for disturbance elimination. This proposed method incorporates the disturbance rejection term in the main control loop, which avoids the side effects of the traditional parallel external observer-based compensation method. The convergence of this disturbance rejection design is also proved. Meanwhile, the procedure of the ISMC-based DPCC method in digital implementation is illustrated and the resulting problems are discussed and solved. Furthermore, the chattering problem caused by the signum function is significantly suppressed by introducing the improved super-twisting algorithm combined method. Finally, experimental results confirm the validity of the proposed ISMC-based DPCC controller.

Robust stabilization control for multi-station motion system with network communication constraints

In this article, the robust stabilization control techniques and the time delays compensation method are proposed in a networked multi-station cooperative motion system (MSCMS), where random network-induced communication constraints are presented. First, an uncertain multi-nodes model of MSCMS is established. Moreover, the random network communication delays, station nodes position compensation, two types of topologies of the station nodes, and the mutual position disturbance among the multi-station nodes are considered simultaneously. Second, a discrete-time Markov chain is used to model the random network delays for the MSCMS. A time delay compensation method is applied to compensate the tracking errors among the multi-motor nodes. Moreover, the stability conditions and the robust controller design method for MSCMS are presented by constructing a new Lyapunov functional and combining stability theory and inequality techniques. Finally, the effectiveness of the proposed method for the MSCMS is verified by several comparative experimental results.

Complete decoupling compensation of three‐phase inverter with LCL filter in synchronous reference frame

A decoupling control strategy of three-phase inverter, which can realize complete decoupling of the active and reactive current in the synchronous reference frame (SRF) is proposed here. There are two coupling factors of current loop in SRF, one is time delay caused by digital control, and the other is AC filter. Dynamic time delay compensation is applied to eliminate coupling caused by the first factor. The phase of the bridge leg voltage can be predicted. The difference between it and the phase of reference voltage which takes part in pulse width modulation (PWM) is the dynamic compensation angle, which can compensate the time delay. High-order feedforward compensation is applied to eliminate coupling caused by the second factor. Complex vector model of the LCL filter is derived and the high-order coupling coefficients can be offset by feedforward compensation. The coupling characteristics and compensation principles are analysed in detail. The system stability is discussed. Finally, the simulation and experimental results are given to verify the theoretical analysis.

A Novel Nonlinear Plus Integral Controller With a Real-Time Application on Incubator Temperature Regulation

A gel card incubator is an important clinical interface device that maintains gel cards at body temperature, completing the initial step in determining blood grouping. Achieving a much faster closed-loop response to shorten the warm-up period and maintaining a uniform temperature inside the incubator are crucial requirements for medical incubation devices. To accomplish incubator control requirements and deal with deadtime, this study proposes a novel nonlinear plus integral control (NPI) scheme coupled with a time-delay compensator using an incubator dynamic model. The NPI successfully shaped the control structure by utilizing a few nonlinear parameters. The control strategy, which promises a significant performance combining linear and nonlinear control actions, is easy to realize, simple to tune, and allows a smooth transition between control actions. Experiments were performed in a microprocessor-controlled gel card incubator using a computer interface to demonstrate the superiority of the proposed control technique. The comparative results prove that the proposed control scheme exhibits significantly faster and superior responses for transient and steady states. It also achieves successful disturbance rejection and less energy consumption than the Smith predictor-based PI control.

Reinforcement Learning-Based Optimal Tracking Control for Levitation System of Maglev Vehicle With Input Time Delay

The running environment of a magnetic levitation (maglev) vehicle is complex, with problems such as track irregularity, external disturbance, varying system parameters, and time delays, which bring great challenges to the design of a high-performance levitation controller. In this article, an adaptive neural network controller with input delay compensation and a control parameter optimization scheme is proposed for the electromagnetic levitation system of a maglev vehicle, which can solve the key engineering problems of external disturbance, input time delay, and time-varying mass. Aiming at the problem of input time delay, a sliding-mode surface with time-delay compensation is constructed, and a double-layer neural network and adaptive law are utilized to approximate the uncertain dynamics; thus, a finite time adaptive tracking control law is proposed. Based on the Lyapunov method, the stability of the proposed controller in finite time is analyzed. The proposed method does not only update the input and output weights of the neural network online, but also introduces reinforcement learning (Actor–Critic network) to optimize the key controller parameter in real time and enhance system robustness. Simulation and experimental results show that the proposed controller can effectively suppress the air gap vibration with time delay and uncertain dynamics, and significantly improve the performance of levitation control.

Networked control strategy of dual linear switched reluctance motors based time delay tracking system

To reduce the influence of time delay on the tracking performance of a direct-drive motion control system, this paper concentrates on stability analysis and cooperative position tracking control issues for the dual linear switched reluctance motors (LSRMs) system with network-induced time delays. The closed-loop network control system (NCS) is constructed by modeling random and bounded network-induced time delays existing in forward and feedback channels as a discrete-time Markov chain. Incremental time delay information is introduced in Lyapunov functional analysis to satisfy the high-precision movement of master and secondary motors and improve the system control performance. The time delay compensation method is proposed to compensate for the damage to the networked control system caused by random delay. With Lyapunov stability theory and LMI are applied, stability and stabilization conditions with less computational complexity and low conservatism are obtained based on incremental time delay information insertion. Finally, the numerical simulation and the experimental platform of the motor control system are built. Simulation and experiment results demonstrate that the networked control strategy can compensate the negative impact of delay on the tracking performance of LSRMs based motion control system.

Adaptive WADC scheme for damping inter‐area oscillation based on Jaya optimization algorithm in the presence of variable time latencies from WAMS data

The continual increase in the power network topological structure and long distances between load-generation sources lead to modern powers systems are operated near theirs stability margins. For this issue, reliable and secure operations of electric devices through inter-area oscillations remain an essential issue in the system dynamic stability. In the case of improper actions of controlling devices, the severe inter-area interactions may lead to wide-area instabilities and large blackouts. Using wide-area measurement system (WAMS), remote signals are transferred through communications links with different inherent time latencies. In the case of large time delays, the main controllers cannot work appropriately which leads to improper performance of damping controllers through severe inter-area fault event scenarios. For this issue, this paper presents an adaptive wide-area damping controller (AWADC) for damping inter-area oscillations in large power systems equipped with WAMS technology consisting of various time latencies. In this case, based on the IEEE C37.118.1 protocol, the generator buses are equipped with phasor measurement unit devices. Also, owing to the different communication links, the measured global signals (GSs) are involved within different time latencies. In this case, at each time window, considering time delay compensator (TDC) technology provided through Simevents discrete event tool, the overall time delay is evaluated and compensated. For identifying the best controlling GSs, considering two observability and controllability concepts, the system dynamic signals are evaluated which the best input decisioning signals and corresponding output controlling signals are provided. The proposed AWADC scheme consists of different compensating blocks which are adjusted through simple and well-known Jaya optimization algorithm (JOA) through online evaluations. The structure of the proposed AWADC controlling scheme is carried out on a modified 39-bus New England test system consisting of large synchronous generators whose damping performances are evaluated through severe fault events with the potential of unstable inter-area oscillations. Simulation results indicate the effectiveness of developed TDC and JOA techniques to provide proper controlling signals through the AWADC controller in the presence of different time latencies.

Research on Optimization of Fuzzy Network Control System Based on New Smith Predictive Time Delay Compensation

Aiming at the problem of network delay when the network control system transmits data, this paper adopts a new type of fuzzy control method of Smith predictor to compensate for the delay. In actual application scenarios, it is difficult to accurately match the Smith prediction model with the actual model. At the same time, the quantization factor and scale factor in the fuzzy PID controller are too dependent on experience, which makes the system’s adaptability to actual working conditions very poor. In this paper, genetic algorithm is used to optimizes fuzzy PID. According to the simulation results, when the Smith predictive model does not match the actual model, the steady-state performance and dynamic performance of the system under the fuzzy PID control optimized by the genetic algorithm are improved.