Control Signal Delay Research Articles

Design ultrasonic power generators for welding machines using piezoelectric ceramic materials for welding on non-woven fabrics

This paper presents the design and manufacture of ultrasonic emitters for welding machines using piezoelectric ceramic materials for welding on non-woven fabrics. The ultrasonic vibrating membrane (UVB) used for the transducer is investigated to ensure that there are no cracks in the material structure. These parameters serve as the basis for evaluating the quality of the ultrasonic vibrating membrane in the fabrication of an oscillator for ultrasonic transducer welding (USTW). The ultrasonic power generator (USPG) is made of high-frequency components and power components to supply electrical oscillations to the UVB. This vibrating source must be compatible with the USTW to operate at maximum efficiency. Due to the influence of the manufacturing process and USTW usage environment, after operating for a long time, the resonant frequency (fr) will be changed. Therefore, the USPG needs to monitor the frequency of the USTW automatically. Matching the impedance of USTW and USPG is very important to get the most out of USPG power. The fabrication results show that the use of high-resolution timer to generate the control frequency for USPG achieves high accuracy, with the largest error of 0.006% at 18401.12 Hz when surveyed in the range of 18 to 22 kHz. The parameters of control signal delay between two phases and pulse width also give very good results. Impedance-matching (IM) networks also show good exploitation of USPG when compared to USPG without IM.

Further experimental results on modelling and algebraic control of a delayed looped heating-cooling process under uncertainties

The aim of this research is to revise and substantially extend experimental modelling and control of a looped heating-cooling laboratory process with long input-output and internal delays under uncertainties. This research follows and extends the authors' recent results. As several significant improvements regarding robust modelling and control have been reached, the obtained results are provided with a link and comparison to the previous findings. First, an infinite-dimensional model based on mathematical-physical heat and mass transfer principles is developed. All important heat-fluid transport and control-signal delays are considered when assembling the model structure and relations of quantities. Model parameter values optimization based on the measurement data follows. When determining static model parameter values, all variations in steady-state measured data are taken into account simultaneously, which enhances previously obtained models. Values of dynamic model parameters and delays are further obtained by least mean square optimization. This innovative model is compared to two recently developed process models and to the best-fit model that ignores the measured variations. Controller structures are designed using algebraic tools for all four models. The designed controllers are robust in the sense of robust stability and performance. Both concepts are rigorously assessed, and the obtained conditions serve for controller parameter tuning. Two different control systems are assumed: the standard closed-loop feedback loop and the two-feedback-controllers control system. Numerous experimental measurements for nominal conditions and selected perturbations are performed. Obtained results are further analyzed via several criteria on manipulated input and controlled temperature. The designed controllers are compared to the Smith predictor structure that is well-established for time-delay systems control. An essential drawback of the predictor regarding disturbance rejection is highlighted.

TFODn‐FOPI multi‐stage controller design to maintain an islanded microgrid load‐frequency balance considering responsive loads support

AbstractModern electrical power system design will increase renewable energy sources (RES) dominance. Rotating masses, the main source of inertia in power systems, have been greatly decreased in renewable energy producing systems. Thus, load–frequency equilibrium is an important indicator of these systems' performance and safety. This work introduces a fractional‐order (FO) operator‐based cascade control structure for islanded microgrid (μG) load‐frequency control (LFC). The structure utilizes a tilt–FO derivative with filter (TFODn) in the first level to reduce noise. The second level implements the proportional integral (PI) controller's FO form (FOPI), making it a tilt–FO derivative with a filter cascaded to the FOPI controller (TOFDn‐FOPI). The optimal controller parameters for quick dynamic responses with low frequency fluctuation are determined using a unique cost function and prairie dog optimization (PDO) algorithm. The LFC control loops have frequency deviation‐based responsive loads (RL). Control signal delays, RES output changes, parameter uncertainties, and cyber vandalism are examined. Laboratory‐scale tests also assessed the controller's practicality. The proposed controller outperforms standard and FO type proportional integral derivative (PID) and PD‐PI controllers. The TFODn‐FOPI controller is suitable for complicated closed‐loop systems like islanded μGs due to its faster error clearing, reduced RL capacity, and superior time and frequency domain indicators.

Полиномиальный матричный метод синтеза регуляторов для объектов с запаздыванием управляющего сигнала

In this paper, we consider the synthesis of control systems for objects with a control signal delay by a polynomial matrix method, which is used to locate the poles and, if possible, zeros in the required position. The controller is calculated from the output, i.e. only from the measured values in the plant, which is an advantage over other modal direction synthesis methods where a state vector must be used. It is proposed to approximate the delay link with a Padé series with a limited number of terms, thus obtaining transfer functions of the first and second orders. The desired characteristic polynomial of the closed system is chosen so that it contains the denominators of the approximation transfer functions, which will keep their poles in the closed system. The polynomial synthesis method makes it possible to calculate multichannel controllers both for objects with multiple inputs and multiple outputs (multi input - multi output, MIMO) and for objects with one input and several outputs (single input - multi output, SIMO). The latter include a DC motor with independent excitation, where the armature current and rotor speed are outputs, and the control signal applied to the semiconductor converter is the input. In this work, the control signal is formed with a delay exceeding the time of the transient process of the engine, which significantly affects its dynamics. By applying the proposed approach, it was possible to synthesize a rotor speed control system that is resistant to changes in the delay time in a fairly wide range.

A Novel Exploration-Exploitation-Based Adaptive Law for Intelligent Model-Free Control Approaches.

Model-free control approaches require advanced exploration-exploitation policies to achieve practical tasks such as learning to bipedal robot walk in unstructured environments. In this article, we first construct a comprehensive exploration-exploitation policy that carries quality knowledge about the long-term predictor and the control policy, and the control signal of the model-free algorithms. Therefore, the developed model-free algorithm continues exploration by adjusting its unknown parameters until the desired learning and control are accomplished. Second, we provide an utterly model-free adaptive law enriched with the exploration-exploitation policy and derived step-by-step using the exact analogy of the model-based solution. The obtained adaptive control law considers the control signal saturation and the control signal (input) delay. Performed Lyapunov stability analysis ensures the convergence of the adaptive law that can also be used for intelligent control approaches. Third, we implement the adaptive algorithm in real time on a challenging benchmark system: a fourth-order, coupled dynamics, input saturated, and time-delayed underactuated manipulator. The results show that the proposed adaptive algorithm explores larger state-action spaces and treats the vanishing gradient problem in both learning and control. Also, we notice from the results that the learning and control properties of the adaptive algorithm are optimized as required.

Adaptive Control of Two-Pendulum Suspension of Overhead Crane

When constructing the bridge crane control law, a two-pendulum model with a hook suspension, on which the transported load is suspended, and a load suspension is considered. This model more accurately describes the dynamics of cargo movement, which is especially critical in a number of crane operating modes, including cases when the mass-inertial parameters of the cargo are close to the hook. A mathematical model of the two-pendulum mechanical system of the crane suspension along one axis of its movement is described, taking into account the effect of friction forces when moving the crane trolley and wind disturbance acting on the transported cargo. Also, there is presented linearized model of hook movement with control action in the form of preset speed of crane trolley movement. The latter corresponds to the use of a servo motor or stepper motor to control the trolley. On the basis of the obtained linearized model, an adaptive control law is constructed using a scheme including an algorithm for current parametric identification, an implicit reference model, "simplified" adaptability conditions with direct tracking of hook movement (through it — cargo movement) by the properties of the assigned reference model. This control law allows you to build crane control under the current parametric uncertainty of the properties of the crane, the transported cargo and external disturbances (only approximate information about some parameters is assumed). It is shown that in the case when the natural frequency of the assigned reference model is less than that for the hook suspension, the proposed control law generates asymptotic movement of the hook (load) to the assigned point and damping of angular oscillations of the hook suspension and load suspension. For more efficient damping of angular oscillations in case of large values of load moment of inertia, it is proposed to supplement preset value of hook movement with damping movements based on angular movement of load suspension. Model examples supporting theoretical conclusions are given. It is shown that the proposed solution makes it possible to build a bridge crane control under the action of measurement noise and control signal delays.

Adaptive robust control for triple avoidance - striking - arrival performance of uncertain tank mechanical systems

This paper puts forward an unprecedented avoidance-striking-arrival problem aiming to address the need for tank's uncertain mechanical systems on the intelligent battlefield. The associated system uncertainties (possibly rapid) are time-varying but bounded (possibly unknown). The goal is to design a controller that enables the tank to aim at and attack the enemy tank while keeping itself (out of the enemy fire zone). The tank maintains this condition until reaching the predefined region. In this paper, an approximate constraint following control method is adopted to solve this problem, and the original constraints are creatively divided into two categories: the avoidance - tracking constraint and the striking - arrival constraint. An adaptive robust control method is proposed and consequently verified through simulation experiments. It is proved that the system fully obeys the avoidance - tracking - constraint and strictly obeys the striking - arrival constraint under the control input τ. Besides, the control of the tank vehicle running system and tank gun bidirectional stabilization system are unified to deal with the control signal delay caused by complex uncertainties on the battlefield. Overall, this paper reduced the delay of signal transmission in the system while solved the avoidance - striking - arrival problem.

Disturbance-observer-based control for semi-Markovian jump systems with time-varying delay and generally uncertain transition rate

The analysis result of disturbance-observer-based control (DOBC) for semi-Markovian jump systems (S-MJSs) with time-varying delay and generally uncertain transition rate (TR) is given in this paper. At present, there are still some urgent problems needed to be solved for S-MJSs such that conservative of stability, difficult of obtaining of TR in practical system, and the unexpected transient performance is always inevitable, such as larger overshoots and longer settling time. Unlike the existing methods, the proposed method considers the external disturbance, limitation on domain of control signal, uncertain parameters and time-varying delay in the S-MJSs. The piecewise analysis method for time-varying delay systems is extended to DOBC for S-MJSs. First of all, the sufficient condition of stochastic stability based on S-MJSs with more general TR is derived by piecewise Lyapunov-Krasovskii functional. Then, the disturbance observer is designed for estimating the actual disturbance, and the anti-disturbance controller is designed to deal with the control problem of S-MJSs. Furthermore, the problem of actuator saturation is addressed. Finally, two practical example is employed to testify the correctness of the proposed methods.

Simultaneous Optimization of Vehicle Arrival Time and Signal Timings within a Connected Vehicle Environment.

Most existing signal timing plans are optimized given vehicles’ arrival time (i.e., the time for the upcoming vehicles to arrive at the stop line) as exogenous input. In this paper, based on the connected vehicle (CV) technique, vehicles can be regarded as moving sensors, and their arrival time can be dynamically adjusted by speed guidance according to the current signal status and traffic conditions. Therefore, an integrated traffic control model is proposed in this study to optimize vehicle arrival time (or travel speed) and signal timing simultaneously. “Speed guidance model at a red light” and “speed guidance model at a green light” are presented to model the influences between travel speed and signal timing. Then, the methods to model the vehicle arrival time, vehicle delay, and number of stops are proposed. The total delay, which includes the control delay, queuing delay, and signal delay, is used as the objective of the proposed model. The decision variables consist of vehicle arrival time, starting time of green, and duration of green for each phase. The sliding time window is adopted to dynamically tackle the problems. Compared with the results optimized by the classical actuated signal control method and the fixed-time-based speed guidance model, the proposed model can significantly decrease travel delays as well as improve the flexibility and mobility of traffic control. The sensitivity analysis with the communication distance, the market penetration of connected vehicles, and the compliance rate of speed guidance further demonstrates the potential of the proposed model to be applied in various traffic conditions.

Analysis of the interaction of robots in decentralized multi-robot system for transport tasks during start of the movement

The article presents the analysis of the influence of control signal time delays on the start of movement of a distributed group of robots and on the implementation of their programmed trajectory. Static analysis was carried out in a distributed group of robots, which were imposed by constraint resulting from connecting the robots with a transport pallet. Then, dynamic analysis of loads occurring as a result of control signal delays in MSC Adams View software was performer.

Hysteretic Control Embedded Boost Converter Operating at 25-MHz Switching

A newly designed hysteretic control is proposed for a 25-MHz switching boost converter. The control part comprises the following three components: the serial connection of a resistor ( ${R} _{\mathrm {r}}$ ) and a capacitor to generate ripple signal, a comparator to adjust the output voltage ( ${V} _{\mathrm{out}}$ ), and an additional resistor ( ${R} _{\mathrm{com}}$ ) inserted between the output and the inverting input of the comparator. In order to avoid signal delays and to allow boost converter topology, the appropriate relationship between ${R} _{\mathrm{r}}$ and ${R} _{\mathrm{com}}$ is presented. The GaN transistor used has an input capacitance of 43 pF and a feedback capacitance of 11 pF at zero drain–source voltage. Owing to these low parasitic capacitances, the comparator can drive the transistor, and this multi-functional comparator configuration also reduces control signal delays. These effects enable the boost converter to operate at a switching frequency of 25 MHz, allowing ${V} _{\mathrm{out}}$ to conform to the envelope of a long term evolution signal with a 4-MHz bandwidth. This capability is quantitatively verified by means of a 3.9% normalized mean square error.

Design of a completely model free adaptive control in the presence of parametric, non-parametric uncertainties and random control signal delay

In this paper, an adaptive controller is developed for discrete time linear systems that takes into account parametric uncertainty, internal-external non-parametric random uncertainties, and time varying control signal delay. Additionally, the proposed adaptive control is designed in such a way that it is utterly model free. Even though these properties are studied separately in the literature, they are not taken into account all together in adaptive control literature. The Q-function is used to estimate long-term performance of the proposed adaptive controller. Control policy is generated based on the long-term predicted value, and this policy searches an optimal stabilizing control signal for uncertain and unstable systems. The derived control law does not require an initial stabilizing control assumption as in the ones in the recent literature. Learning error, control signal convergence, minimized Q-function, and instantaneous reward are analyzed to demonstrate the stability and effectiveness of the proposed adaptive controller in a simulation environment. Finally, key insights on parameters convergence of the learning and control signals are provided.

Influence of eigenvectors on trajectories of discrete systems with control signal delay

Subjectof Study.We present research results of the free motion of discrete linear systems in case of the control signal transmissionto continuous plantwith a delay not exceeding the discreteness interval duration. It was foundthat if the output control signal delay does not exceed the discreteness interval durationthen the dimension of the discrete representation of the continuous plant is increased by one. We consider a class of discrete systems with simple structure state matrix and with the eigenvectors structure such that condition number of their matrix is much greater than one.Method. The problem is solved with the use of vector-matrix formalism of state space method;for that reason the system is presented in vector-matrix form. Analytical assessments of processes in the system arefigured on the norm of state vectorfree motion with the calculation of the condition number of the state matrix eigenvectors matrix. Main Results. It has been found that the ill-conditioned eigenvectors structure of the state matrix may cause significant deviations of free motion trajectories from a monotone decreasing curve. Practical Relevance. These properties of the free motion of discrete systems trajectories are recommended for being kept under supervision, both in the design and the operational phases of systems.

The Assignment of Generalized Time Constant for A Non-All-Pole System

This paper discusses the assignment of generalized time constant for a non-all-pole system. The generalized time constant is found to be important because it simultaneously influences the speed of response, damping (i.e., overshoot), and robustness. For the ease of explanation, a general two-mass system is introduced as a case study, which has one pair of $j\omega$ -axis zeroes. Under an ideal two-parameter control configuration, the exact lower bound of the generalized time constant is determined that results in monotonic step responses, while a moderate generalized time constant is shown to be desirable for robustness purposes. A modified-Integral–Proportional–Derivative control configuration is then adopted for the implementation of the ideal two-parameter controller. It is found that, in real applications, a specific control configuration and signal delay may also impose limits on the assignment of the generalized time constant and characteristic ratios. Due to the clear physical meaning of the polynomial method, the tradeoff relationship among the speed of response, damping, and robustness can be explicitly represented. This unique advantage leads to a straightforward controller design procedure. Finally, the theoretical analysis is validated by experimental results.

Cooperative synchronization control for agents with control delays: A synchronizing region approach

This paper investigates multi-agent system synchronization in the presence of control signal delays. Agents are assumed to be identical linear time-invariant systems, interacting on a directed graph topology, all having the same control delay. Distributed control of multi-agent systems is complicated by the fact that the communication graph topology interplays with single-agent dynamics. Here a design method based on a synchronizing region is given that decouples the design of local feedback gains from the detailed properties of graph topology. Such extension of the synchronizing region concept to agents with delays is rigorously justified. Delay-dependent synchronizing region is defined and methods are given guaranteeing its estimates. Qualitative properties of delay-dependent synchronizing regions and implications for control design are discussed. It is found that these regions are inherently bounded which restricts the graphs that allow for synchronization under delayed communication. Stronger property of exponential stability with a prescribed convergence rate is presented as a special case.

Perturbation Analysis and Optimization of Stochastic Hybrid Systems

We present a general framework for carrying out perturbation analysis in Stochastic Hybrid Systems (SHS) of arbitrary structure. In particular, Infinitesimal Perturbation Analysis (IPA) is used to provide unbiased gradient estimates of performance metrics with respect to various controllable parameters. These can be combined with standard gradient-based algorithms for optimization purposes and implemented on line with little or no distributional information regarding the stochastic processes involved. We generalize an earlier concept of “induced events” for this framework to include system features such as delays in control signals or modeling multiple user classes sharing a resource. We apply this generalized IPA to two SHS with different characteristics. First, we develop a gradient estimator for the performance of a linear switched system with control signal delays and a safety constraint and show that it is independent of the random delay's distributional characteristics. Second, we derive closed-form unbiased IPA estimators for a Stochastic Flow Model (SFM) of systems executing tasks subject to either hard or soft real-time constraints. These estimators are incorporated in a gradient-based algorithm to optimize performance by controlling a task admission threshold parameter. Simulation results are included to illustrate this optimization approach.

High Quality Power Supply Method for Islanding Microgrid by use of Several Types of DG Systems including Rotating Machines

When a microgrid is operated in the islanding mode, the operator must satisfy the power quality demand by compensating the active and reactive power using several types of distributed power generation (DG) systems. In this paper, a method to stabilize the system frequency fluctuations and voltage fluctuations of the islanding microgrid is suggested. Extending the suggested “combined cascade control method” which can realize the power compensation without interferences between several types of DGs, “hybrid control” strucuture is proposed and negative effects of control and measurement signal delays on a control are reduced. Moreover, a control of the state of charge (SoC) of energy storage devices is added. For the stabilization of the system voltage, the energy storage is driven by “STATCOM model control”. Experiments have been carried out to confirm the effects of these methods by use of the model microgrid system, and satisfying results were received.

Analysis of common‐channel signaling network congestion in the presence of considering various kinds of delay

AbstractCommon channel signaling networks play an important role in providing advanced switching services. With the increase in the degree of the reliability of such switching services on common channel signaling networks, the common channel signaling networks are easily congested, and controlling congestion on these networks has become increasingly important. On the other hand, the network scale has been increasing with the development of the information society. With the increase in the network scale, signal transmission delay and control signal delay have increased, giving adverse effects on congestion control. In this article, the congestion control on common channel signaling networks recommended by CCITT has been analyzed considering the above‐said transmission delay and control signal delay. As a result of this analysis, the above‐said adverse effects could be evaluated quantitatively. A rigorous solution of this model could not be obtained. Thus, a method of analysis by fluid approximation is proposed. In addition, this approximating analytical method is shown to have sufficient practical accuracy in comparison with simulation results. By this analytical method, the rates of blocking of congested resources (signal links, circuits), mean delays, etc., can be easily obtained. As a result of the analysis, it is shown that these delays greatly influence the efficiency of congestion control. Especially, it is shown that the call loss rate shows a great effect; and control parameters must be determined considering these delays in order to satisfy certain standard values by congestion control.

The solution of finite‐time optimal control problems with control time delays

AbstractThe design of deterministic LQP optimal control systems is considered for plants with control delays and a finite optimization interval. First, a solution is obtained to the fixed end‐point optimal control problem. An expression for the open‐loop optimal control is derived in the s‐domain. The closed‐loop optimal time‐varying gain matrix is then calculated from the s‐domain results. The open‐loop and closed‐loop solutions to the free end‐point optimal control problem are also given. The constant gain, infinite‐time, feedback control law is obtained as a limiting case of these results.The receding‐horizon optimal control problem for plants with control signal delays is also considered. The solution to this problem yields a constant feedback gain matrix which has obvious advantages for implementation. This gain matrix is not the same as the constant solution to the infinite‐time problem. The receding‐horizon control laws are derived for both the fixed and free end‐point problems, and these are shown to produce asymptotically stable closed‐loop systems.