Maximum Allowable Time Delay Research Articles

On computing maximum allowable time delay of Lur’e systems with uncertain time-invariant delays

In this paper, we present an improved delay-dependent absolute stability criterion for Lur’e systems with time delays. The guarantee of absolute stability is provided by Lyapunov-Krasovskii theorem with the Lyapunov functional containing the integral of sector-bounded nonlinearities. The Lyapunov functional terms involving delay are partitioned to be associated with each equidistant fragment on the length of time delay. Employing the Jensen inequality and S-procedure, the sufficient condition is derived from time derivative of the Lyapunov functional. Then, the absolute stability criterion expressed in terms of linear matrix inequalities (LMIs) can be efficiently solved using available LMI solvers. The bisection method is used to determine the maximum allowable time delays to ensure the stability of Lur’e systems in the presence of uncertain time-invariant delays. In addition, the stability criterion is extended to Lur’e systems subject to norm-bounded uncertainties by using the matrix eliminating lemma. Numerical results from two benchmark problems show that the proposed criteria give significant improvement on the maximum allowable time delays.

The Research of the Optimization Model of Flight Scheduling Based on Filtered Beam Search

According to the characteristics of the optimization theory and arrival flights.Established static and dynamic model which take the aircraft delay cost as target. The limit of maximum allowable delay time variable are introduced to reduce the delay cost, take into account fairness of flights landing at the same time. The solution of the model is filtered beam search algorithm (FBS).

A New Coordinated Slave Torque Feedback Control Algorithm for Network-Based Teleoperation Systems

The control design problem is investigated for network-based teleoperation systems under the condition of asymmetric and time-varying delays. The classic teleoperation model is considered for which the position of the master is transmitted to the slave site as the control command and the slave torque is directly transmitted to the master in order for the user to have a feeling of the remote interaction. The slave controller is constructed based on the master-slave position error plus a new nonlinear damping function, while the master controller is composed of the transmitted slave torque and the introduced nonlinear damping function. By employing a new Lyapunov Krasovskii functional, we prove the exponential input-to-state stability of the closed-loop system. The relationship is built among the control design parameters and the maximum allowable time delays, which is in the form of linear matrix inequality. Both the simulations and experiments are performed to show the effectiveness of the proposed method. Compared with existing approaches, transmission delays considered are both time varying and asymmetric, and the passivity conditions on the remote environment and the human operator are removed. In addition, the method is very simple.

Stability of state-proportional integral derivative (PID) feedback control system with time delay

This article proposes a method to compute the maximum allowable delay time for linear-time-invariant-time-delayed-systems (LTI-TDS) with state-PID feedback control. It presents the main theorem with corollary, and computing steps to obtain Stability of a LTI-TDS with state- proportional integral derivative (PID) feedback is ensured if the delay time is less than The proposed approach is compared with the matrix pencil method. Stabilization for the system is also proposed by using a low-pass filter. It was shown by simulation that the system is made more tolerable to delay by judicious selection of the DC gain and the time-constant of the filter. Seven case studies serve to demonstrate the effectiveness of the proposed approaches. Key words: Routh’s criterion, time-delayed, state-PID feedback, stability and stabilization, neutral systems.

Optimizing Rolling Patterns for Chip Seals Using Laboratory Aggregate Loss Performance Tests on Field Fabricated Samples

This paper presents a study to determine the optimal rolling patterns for chip seals based on aggregate retention performance. Chip seal sections composed of single seals of granite 78M and CRS-2 emulsion are constructed using five different rolling patterns with two or three rollers. Both pneumatic tire and combination rollers are used in developing these patterns. Chip seal samples are obtained from the sections for laboratory testing. The aggregate retention performance is evaluated using the flip-over test, Vialit test, and the third-scale model mobile loading simulator. It is found that the time delay between aggregate spreading and rolling is an important parameter for the aggregate retention performance. The laboratory aggregate retention test results are used along with typical roller speeds and the maximum allowable time delay between aggregate spreading and rolling to develop optimal rolling patterns for two and three rollers.

Investigating Time-Delay Effects for Multivehicle Formation Control

Advancesincommunication,navigation,andcomputationalsystemshaveenabledgreater autonomy in multivehicle systems. However, time-delay effects owing to measurement, actuation, communication, or operator delays are introduced as system complexity increases. In this paper, a straightforward method is presented to determine the maximum allowable time delays for a linear, n-dimensional system. Delay differential equations are one method to model systems with delay, and the theory presented here is based upon wellknown stability results for a scalar, first-order delay differential equation. Modal-coordinate transformations are used to diagonalize, and thus, decouple closed-loop equations of motion to which the scalar, first-order delay-differential-equation results are applied in order to find optimal bounds on the time delay. Hence, stability bounds for a given closed-loop control form can be determined by solving an eigenvalue problem, which is a departure from other delay-differential-equation results that require solutions to linear matrix inequalities or a problem-specific Lyapunov function to prove stability. This theoretical development is applied to a formation-control problem with five vehicles. Control laws are developed for the vehicle formation using two different communication structures: leader‐follower and bidirectional. Simulation results are used to demonstrate formation convergence, and robustness of the formations to time-delay effects are discussed.

Optimal performance of discrete-time direct output-feedback structural control with delayed control forces

An optimal discrete-time direct output-feedback control algorithm is developed with the consideration of sampling period and appropriate time delay in its control force action. Optimal-delayed output-feedback gains are derived through a variation process and will be complementarily arranged with respect to the applied delay time by either altering their magnitude or phases to assure the efficacy and stability of the delayed direct digital control system. Parametric studies of single-degree-of-freedom (SDOF) systems with different feedback types demonstrate the relationships of the delayed gains and the modal properties corresponding to the sampling period used and the intentionally delay time added. The maximum allowable delay time defined at the onset of instability of controlled system can be the optimal delay time that reaches the optimal control performance if the delay time is considered in the delayed feedback gains. The inclusion of sampling period and delay time in the optimization process for discrete-time control illustrates the beneficial effect under the same delay time. Numerical simulation results of proposed direct digital control principles on a three-degree-of-freedom (3DOF) shaking table structure model show that the efficacy of the collocated control cases with optimal delay time to reduce the dynamic responses subjected to earthquake excitations is assured. Copyright © 2007 John Wiley & Sons, Ltd.

Time delay H ∞ control of structures under earthquake loading

In this paper, an H ∞ control algorithm is developed to reduce the earthquake response of structures with consideration of control force execution time delay. To achieve optimal control performance and assure control system stability, the strategy to select two control parameters γ and α is extensively investigated. It was found that the decrease of γ or increase of α results in significant reduction of structural responses. To obtain the same control results, a larger α has to be selected for stiff structures than for flexible structures. In addition, in active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay times not only can render the control ineffective, but also may cause system instability. In this paper, explicit formulas for the maximum allowable delay time and critical control parameters are derived for the design of a stable H ∞ control system. Some solutions are also proposed to lengthen the maximum allowable delay time.

Optimal H∞ Output Feedback Control Systems with Time Delay

An H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is developed in this paper to reduce the earthquake response of structures. To achieve optimal control performance and assure control system stability, the strategy to select both control parameters γ and α is extensively investigated considering the control force execution time delay. It is found that a lower bound of γ and an upper bound of α exist. The selection beyond these values will cause the control system instability. For a damped structure, analytical expressions of direct output feedback gains, controlled frequencies and damping ratios are derived. It can be proved that the conventional LQR control is a special case of the developed H∞ control. In real active control, control force execution time delay cannot be avoided. This paper gives explicit formulas of maximum allowable delay time and critical control parameters for the design o...

자동차 네트워크 시스템의 효율적 관리를 위한 CAN의 동적 선행대기 열 기법

Today the automobile has been changed from a mechanical system to an electronic control system fly the development of the electronic technology. In the automobile body, most of these electronic control devices are networked and managed fully by the CAN protocol. But, when a network system is overloaded, unexpected transmission delay for relative low priority objects occurs due to the static priority definition of the CAN protocol. To resolve this problem, this paper proposes a dynamic precedence queue mechanism that creates a queue for the low priority object and its relevant objects to be transmitted, which becomes urgent in an overloaded network system to keep the maximum allowable time delay. For the generated queue, the highest priority is assigned to transmit the queued objects within the shortest time. The mechanism is implemented in the logical link layer of CAN, which does not require any modification of the old CAN hardware. Effectiveness of the proposed mechanism is verified by the real experiments with an automobile network system.

Instability due to time delay and its compensation in active control of structures

AbstractTime delay problem and its compensation in active control of civil engineering structures were studied. It has been shown by stability analysis of a SDOF system with time delayed feedback that the maximum allowable time delay depends not only on the natural period of the structure but also on feedback gains. We have demonstrated by numerical simulation that the performance of the control system degrades significantly when the time delay is close to this value and it even becomes unstable when time delay is greater than or equal to this value. The maximum allowable time delay decreases with decrease in natural period of the structure as well as with increase in active damping. The paper presents a technique for compensation by modelling time delay as transportation lag. This method ensures the stability of the controlled system as well as the desired response reduction.

Interruptible load considerations in spinning reserve assessment of isolated and interconnected generating systems

The authors present a technique which includes interruptible loads in the probabilistic assessment of the operating reserve in isolated and interconnected generating systems. This technique is then used to evaluate the magnitude and corresponding maximum allowable time delay of load interruption required to reduce the unit commitment risk in the absence of other capacity adjustments. They also present a probabilistic technique which can be used to evaluate the inherent interruptible load carrying capability of an isolated and interconnected generating system which exists without having to commit any extra units other than those required to carry the firm load. The study provides an insight into load interruption and its effect on the system risk. The techniques developed are illustrated by numerical examples. These techniques can be used in short and medium term operational planning.

Time-delay image degradation with dental xeroradiography.

Dental xeroradiography produces high-quality images of dental structures under ideal conditions. However, charged-but-not-developed xeroradiographic photoreceptor plates lose some of their charge with time, a phenomenon termed "dark decay." This investigation assesses the maximum allowable time delay between (1) charging and exposing the photoreceptor, (2) exposing and developing the photoreceptor, and (3) a combination of both delays. Measurements of resolution, background density, broad-area contrast, noise, point discharge artifacts, and diagnostic image quality indicate that photoreceptors should be processed within 5 to 10 minutes of charging in order to avoid substantial image degradation.