Delay Compensation Schemes Research Articles

Periodic Event-Triggered Robust Distributed Model Predictive Control for Multiagent Systems With Input and Communication Delays

This paper investigates the problem of event-triggered distributed model predictive control (DMPC) for continuous-time nonlinear multi-agent systems (MASs) subject to bounded disturbances, input and communication delays simultaneously. The compensation schemes for input and communication delays are proposed, respectively. A new optimal control problem (OCP) to achieve consensus among all agents is formulated under the proposed delay compensation schemes. To alleviate the communication burden and sensing cost, a novel input delay-related periodic event-triggering condition is proposed based on the state error to determine when to calculate the new control input. Sufficient condition guaranteeing the feasibility of the OCP is achieved with the proposed event-triggered control scheme. In stability analysis, a novel time-varying Lyapunov function is constructed, and the input-to-state practical stability (ISpS) of the MASs is derived by using the quasi-Lipschitz continuous property of the Lyapunov function. Numerical results related to vehicle platooning demonstrate the effectiveness of the proposed event-triggered DMPC.

Overview of Predictive Control Technology for Permanent Magnet Synchronous Motor Systems

Permanent magnet synchronous motors (PMSMs) are commonly used in the automation industry. With the speedy development of digital system processors, predictive control as a modern control scheme has been applied to improve the dynamic performance and work efficiency of PMSMs. This paper provides an overview of the research status of PMSM-based predictive control strategies. The deficiencies of the three most popular predictive schemes, deadbeat predictive control, finite-control-set model predictive control, and continuous-control-set model predictive control, and existing improvement strategies such as delay compensation schemes, robust control schemes, and multi-vector control schemes, are summarized. Finally, current technological trends are discussed, emphasizing future research directions for predictive control in PMSM drive systems.

Discrete Domain Design Scheme of Complex-Vector Current Controller for Induction Motor at Low Switching Frequency

The synchronous coordinates complex-vector proportional–integral (PI) controller is a high-performance current controller for vector-controlled ac motors, which is designed based on the continuous domain motor models. However, the application of digital signal processors in motor control necessitates the conversion of continuous domain models to discrete domain models. Moreover, the digital control itself has delay effects. Therefore, the original performance of continuous-domain-designed current controllers may be degraded. In order to improve the deteriorative performance, this article proposes corresponding delay compensation schemes for the forward Euler, backward Euler, and trapezoidal method discretized complex-vector PI controllers, respectively, which are analyzed based on discrete domain models. The root locus, frequency characteristics, and bandwidth are utilized to evaluate the performance of these three discretized controllers at the low switching frequency. Finally, the simulation and experimental results validate the analysis and the delay compensation methods proposed in this article.

Real-Time Aeroelastic Hybrid Simulation of a Base-Pivoting Building Model in a Wind Tunnel

The wind tunnel test is one of the most reliable methods for evaluating the dynamic response of high-rise buildings in regards to wind-structure interaction. In conventional aeroelastic wind tunnel tests the calibration of stiffnesses, masses and the damping properties of a scaled specimen is required. This takes extensive time and effort, especially when the tests need to be repeated with various geometric designs during design iterations. This study introduces a new testing method that combines a numerical simulation and the conventional aeroelastic wind tunnel test through the real-time hybrid simulation method. The stiffness, damping and partial mass of a scaled building model are represented numerically, while the rest of the mass, the wind-induced pressure around the model and the wind-structure interaction are represented physically in a wind tunnel. The building model in the wind tunnel rests on a base-pivoting system, which is controlled with a linear motor. The base moment induced by wind pressure and the inertial force from the mass of the physical specimen are measured; those measurements are then fed back into a numerical integration scheme. A delay-compensation scheme is implemented to minimize the effects of actuator delay on the dynamic response of the system. Several tests are carried out to validate and calibrate the developed test apparatus and control scheme including 1) tests for the identification of actuator delay, 2) free vibration tests for characterization of the dynamic properties of the hardware and the control system and 3) wind tunnel tests for system validation through aeroelastic real-time hybrid simulation. This paper presents the overall design of the experimental apparatus, the adopted delay compensation and numerical integration schemes, and a summary of the test results. Test results confirmed that the developed experimental technique can replace the conventional aeroelastic wind tunnel tests of a building model, thus improving the efficiency of the aeroelastic wind tunnel testing.

The performance of delay compensation in real-time dynamic substructuring

Real-time dynamic substructuring (RTDS) is a state-of-the-art experimental technique for evaluating the dynamic performance of a structural system subjected to time-varying loads in civil engineering. The accuracy and stability of RTDS is affected by the natural dynamics of the constituent transfer system. Of various control strategies, and due to the merits of simple implementation and low computational cost, delay-compensation methods have become most pervasive. In this paper, the performance of delay compensation based methods for RTDS is assessed in terms of accuracy and stability. Three commonly-used delay compensation schemes are considered, two of which are time variant and one time invariant. Stability is assessed analytically, numerically, and experimentally. Accuracy is assessed numerically and experimentally. To provide a suitable test for the delay compensation control schemes, a shaking table is adopted as the RTDS transfer system. It is demonstrated numerically, analytically, and experimentally that when applied to transfer systems such as these, delay compensation can work to the detriment of test accuracy and test stability. Adequate performance of delay compensated, shaking-table based RTDS is confined to a narrow low frequency bandwidth, which severely restricts the range of potential application.

Delay compensation using Smith predictor for wireless network control system

Wireless Sensor Network (WSN) is widely used in the industrial Network Control System (NCS). It relies on the IEEE 802.15.4 MAC protocol to transfer data at low rate. Experimental and theoretical studies proved that the wireless channel produces a time delay. In the NCS, this delay may cause system instability and performance degradation. Delay compensation schemes are used to reduce the delay effects.In this paper, a delay compensation scheme using classical and adaptive Smith predictor is applied to wireless NCS. The Markov model is proposed to compute the estimated network delay used in the classical predictor. In the adaptive predictor, the channel delay statistics using shift register is proposed to update the estimated delay. To evaluate the proposed schemes, a DC-motor controller system based on IEEE 802.15.4 is built using True Time Matlab software. The system performance with and without the proposed delay compensation scheme is studied. It is also compared to other delay compensation schemes. The results show that the proposed scheme improves the NCS performance significantly and reduces the effect of the delay on the system.

Using time delay compensation scheme in dynamic output feedback controller for networked control systems

This paper proposes a new method to design the dynamic output feedback controller for networked control systems (NCS) with communication delay in both forward and feedback channels. In order to remove the effects of the communication delay according to one's will, two different network delay compensation schemes are provided in two cases: the controlled plant whose state vectors can be measured and the one whose state vectors cannot be measured. Furthermore, another key part of this paper is to analyse the stability of the closed-loop networked control system. Finally, numerical simulation results show the effectiveness of the proposed method.

Identification and control of delayed unstable and integrative LTI MIMO systems using pattern search methods

In this paper, we develop a multi-model adaptive control strategy to be applied on delay compensation schemes for stable/unstable LTI MIMO systems. The only requirement is that the delay should be bounded and decoupled from the control strategy. The delay identification problem is formulated as an optimization one, and it is framed on the abstract definition of the Generalized Pattern Search Method (GPSM). Taking advantage of the global convergence analysis presented by GPSM, we make a stability analysis of the proposed approach and delay identification capabilities. Simulation examples show the usefulness of the proposed strategy proving that the scheme is capable of identifying the delay and stabilizing the system even with a larger delay. The capabilities of the approach are tested on a second-order delayed unstable process, a MIMO unstable systems and an irrigation channel model. Additionally, simulation examples on an irrigation channel with time-varying delay are presented.

High-Performance Digital Resonant Controllers Implemented With Two Integrators

Resonant controllers are one of the highest performance alternatives for ac current/voltage control. The implementations based on two integrators are widely employed to achieve frequency adaptation without substantial computational burden. However, the discretization of these schemes causes a significant error both in the resonant frequency and in the phase lead provided by the delay compensation. Therefore, perfect tracking is not assured, and stability may be compromised. This paper proposes solutions for both problems without adding a significant resource consumption by correction of the roots placement. A simple expression to calculate the target leading angle, in delay compensation schemes, is also proposed to improve stability margins by means of a better accuracy than previous approaches. Experimental results obtained with a laboratory prototype corroborate the theoretical analysis and the improvement achieved by the proposed discrete-time implementations.

Performance of a real‐time pseudodynamic test system considering nonlinear structural response

AbstractThis paper presents the implementation details of a real‐time pseudodynamic test system that adopts an implicit time integration scheme. The basic configuration of the system is presented. Physical tests were conducted to evaluate the performance of the system and validate a theoretical system model that incorporates the dynamics and nonlinearity of a test structure and servo‐hydraulic actuators, control algorithm, actuator delay compensation methods, and the flexibility of an actuator reaction system. The robustness and accuracy of the computational scheme under displacement control errors and severe structural softening are examined with numerical simulations using the model. Different delay compensation schemes have been implemented and compared. One of the schemes also compensates for the deformation of an actuator reaction system. It has been shown that the test method is able to attain a good performance in terms of numerical stability and accuracy. However, it has been shown that test results obtained with this method can underestimate the inelastic displacement drift when severe strain softening develops in a test structure. This can be attributed to the fact that the numerical damping effect introduced by convergence errors becomes more significant as a structure softens. In a real‐time test, a significant portion of the convergence errors is caused by the time delay in actuator response. Hence, a softening structure demands higher precision in displacement control. Copyright © 2007 John Wiley & Sons, Ltd.

Real‐time hybrid experiments with Newmark integration, MCSmd outer‐loop control and multi‐tasking strategies

AbstractReal‐time hybrid testing is a promising technique for experimental structural dynamics, in which the structure under consideration is split into a physical test of key components and a numerical model of the remainder. The physical test and numerical analysis proceed in parallel, in real time, enabling testing of critical elements at large scale and at the correct loading rate. To date most real‐time hybrid tests have been restricted to simple configurations and have used approximate delay compensation schemes. This paper describes a real‐time hybrid testing approach in which non‐linearity is permitted in both the physical and numerical models, and in which multiple interfaces between physical and numerical substructures can be accommodated, even when this results in very stiff coupling between actuators. This is achieved using a Newmark explicit numerical solver, an advanced adaptive controller known as MCSmd and a multi‐tasking strategy. The approach is evaluated through a series of experiments on discrete mass–spring systems. Copyright © 2006 John Wiley & Sons, Ltd.

Long-term propagation delay characteristics of telecommunication lines

The variations in outgoing path delay and incoming delay of a paired transmission path have been measured simultaneously and independently for over one year. The characteristics will allow the performance of delay compensation schemes for precise time synchronization of digital telecommunication networks to be evaluated. The annual delay variation is caused by temperature changes, and its magnitude is about 3 mu s for the 2400-km line investigated. It is shown that the variation of annual delay can be estimated by measuring air temperature above the cable. The delay variations, which vary slowly with a period of over 10/sup 3/ s, such as annual and daily variations, are clearly correlated for the outgoing and incoming paths. Asymmetry of slow delay variation is below 1 ns (indicated noise deviation). The cause of the delay variation that has a period of 10/sup 0/< tau <102 s is the noise generated by the multiplexing and demultiplexing equipment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>