Output Delay Research Articles

Output feedback control of linear systems with input, state and output delays by chains of predictors

In this paper, we consider the control problem of linear systems with state time-delays when the control signal is affected by a possibly time-varying delay. The problem is solved by a chain of predictors under the assumption that a stabilizing control exists for the case of no input delay. This solution is then extended to the case of partial information when only delayed output is available. Both the input and the output delays may have arbitrary bounds. With respect to previous approaches to the same problem appeared recently in the literature the method proposed here has a simpler structure and in particular it does not need the computation of distributed terms. As a by-product we show that it is possible to derive an observer for a system with state and output delays from an observer for the same system without output delays.

An advanced technique using an electronic taste-sensing system to evaluate the bitterness of orally disintegrating films and the evaluation of model films

Taste detection systems using electronic sensors are needed in the field of pharmaceutical design. The aim of this study was to propose an advanced technique using a taste-sensing system to evaluate the bitterness of an orally disintegrating film (ODF) samples. In this system, a solid film sample is kept in the test medium with stirring, and the sensor output is recorded. Model films were prepared using a solution-casting method with a water-soluble polymer such as pullulan, HPMC, HPC or PVP as film formers, and donepezil hydrochloride and quinine hydrochloride as model bitter-tasting active pharmaceutical ingredients (APIs). The results showed that this advanced techniques could detect the emergence of bitterness along the time course. Increasing the amount of donepezil hydrochloride increased the sensor output. The sensor output was suppressed at the very early stage of the test, and then increased. Both the film thickness and the use of additives markedly affected the delay of the sensor output. The profile of the sensor output was accurately related to the release of APIs. It was concluded that this advanced technique could detect the onset of bitterness during the initial stage of ODF administration.

Performance Analysis Comparison of 4-2 Compressors in 180nm CMOS Technology

In this paper, different 4-2 compressors are designed by using various logic styles and their performances are compared. Different 4-2 compressors are designed and simulated by using the Cadence Virtuoso tool in 180nm CMOS technology and the performance parameters of these are studied in terms of maximum output delay, average power consumption and power-delay-product (PDP) with a variation of supply voltage ranging from 1.2V to 3.0V. Simulation results depict that the performance of a compressor depends on the performance of Exclusive-OR-Exclusive-NOR (XOR-XNOR) module and Multiplexer (MUX), and performance varies as per the logic styles used to implement these blocks.

Design of an Energy Efficient 4-2 Compressor

In this paper an energy efficient 4-2 compressor is designed by utilizing only 36 transistors. The architecture of this new compressor consists of 8 transistors (8T) Exclusive-OR-Exclusive-NOR (XOR-XNOR) module and multiplexer based on transmission gate logic. The 8T XOR-XNOR module not only offers high speed, full voltage swing at outputs but also consumes less power. Simulations are done by using Cadence Virtuoso Tool in 180nm CMOS technology. The performance parameters, viz. maximum output delay, average power dissipation and power-delay-product (PDP) are varied from 920.1ps to 211.4ps, 11.85µW to 123.4µW and 10.90fJ to 26.09fJ respectively with a variation of supply voltage from 1V to 3V. Further a comparison of the performance parameters of the proposed compressor is performed with a number of the existing 4-2 compressors at 1.8V supply. Simulation results depict that the proposed compressor attains improvement in terms of speed, power and PDP.

Modelling and analysis of crosstalk induced noise effects in bundle SWCNT interconnects and its impact on signal stability

In order to analyse crosstalk delay and stability in single wall carbon nanotube bundle (SWCNT) interconnects, the time and frequency domain response are investigated in this paper. Based on the transmission line model and by using matrix formulation, we perform the Nyquist stability analysis to survey the dependence of the degree of relative stability for coupled SWCNT bundle interconnects. We present an exact transfer function formula for a SWCNT bundle and two coupled SWCNT bundle interconnects. The proposed model can be extended to coupled n bundled SWCNT interconnects. In order to demonstrate the crosstalk effects, we seek to compare the coupled SWCNT bundle interconnects with the SWCNT bundle interconnect. The results show that due to the capacitive and mutual inductive couplings between two SWCNT bundles, the stability of near-end output increases and the created undesirable voltage on the far-end output may reduce the stability and degrade logic. Also, it is observed that stability and switching delay of near-end output increases with increasing the interconnect length and diameter. Furthermore, maximum overshoot and switching delay of far-end output increases with length and diameter of interconnect. Also, as the parasitic coupling capacitance increases and the mutual inductance decreases, stability of near-end output increases whereas the stability of the far-end output decreases. Finally, compared to Advanced Design System results, the model exhibits an excellent accuracy.

Stabilization of MISO fractional systems with delays

We consider multi-input single-output (MISO) fractional systems of commensurate fractional orders with different input or output delays. We derive explicit expressions of left and right coprime factorizations over H∞ and of the associated Bézout factors of the transfer matrix of the systems. These factors allow the construction of the Youla–Kučera parametrization of the set of stabilizing controllers which guarantee the internal stability of the closed-loop systems.

LPV Model Order Selection from Noise-corrupted Output and Scheduling Signal Measurements

In parametric identification of Linear Parameter-Varying (LPV) systems, it is important to achieve a low variance of the model estimate by limiting the number of parameters to be identified. This is the well known “model order selection” problem, which consists of selecting the number of input and output delays and the basis functions characterizing the dependence of the LPV model parameters on the scheduling signal. Ignoring the effect of noise on the observations of the scheduling signals may lead to a bias in the final estimate and, as a consequence, also to an incorrect selection of the model order. In this paper, we introduce a “bias-corrected cost function” for the identification of LPV systems from noise-corrupted observations of the output and scheduling variable. The introduced cost function provides a bias-free parameter estimation along with model order selection. The proposed identification approach has two main advantages: (i) the problem of model order selection can be handled by adding a LASSO-like penalty term to the bias-corrected cost function; (ii) it provides a bias-free cost as a criterion to tune some hyper-parameters influencing the final parameter estimate.

Generalized filtering of one-sided Lipschitz nonlinear systems under measurement delays

This paper addresses the filtering problem for the one-sided Lipschitz nonlinear systems under measurement delays and disturbances using a generalized observer. A generalized architecture for filtering of the one-sided Lipschitz nonlinear systems with output delays is explored, which exhibits diverging manifolds, namely, the conventional static-gain filter and the dynamical filter, and can be employed to render robust stability of the filtering error dynamics. A matrix inequality based framework is obtained by employing a Lyapunov−Krasovskii (LK) functional, whose derivative is exploited through Jensen's inequality, one-sided Lipschitz condition, quadratic inner-boundedness inequality and range of the measurement delay, resulting into L2 stability for the filtering error system. Generalized filter design for the Lipschitz nonlinear systems with delayed outputs and specific results for the delay-dependent and delay-rate-independent filtering schemes for the one-sided Lipschitz nonlinear systems are deduced from the proposed approach. Convex optimization techniques are employed to achieve a solution for the nonlinear constraints through linear matrix inequalities by employing cone complementary linearization approach. Illustrative numerical examples to demonstrate the effectiveness of proposed method are provided.

Stabilization of Switched Linear Systems With Quantized Output and Switching Delays

This paper addresses the problem of designing time-varying quantizers for the stabilization of switched linear systems with quantized output and switching delays. The detection delays of switches are assumed to be time-varying but bounded, and the dwell time of the switching signal is assumed to be larger than the maximum delay. Given a switching controller, we analyze reachable sets of the closed-loop state by using a common Lyapunov function and then construct a quantizer that guarantees asymptotic stability. A sufficient condition for the existence of such a quantizer is characterized by the maximum switching delay and the dwell time.

Prediction-based control for LTI systems with uncertain time-varying delays and partial state knowledge

ABSTRACTThe stability of a prediction-based controller for linear time-invariant (LTI) systems is studied in the presence of time-varying input and output delays. The uncertain delay case is treated as well as the partial state knowledge case. The reduction method is used in order to prove the convergence of the closed-loop system including the state observer, the predictor and the plant. Explicit conditions that guarantee the closed-loop stability are given, thanks to a Lyapunov-Razumikhin analysis. Simulations illustrate the theoretical results.

A low-power rail-to-rail input-range linear delay element circuit

Delay elements are one of the key components in many time-domain circuits such as time-based analog-to-digital converters. In this paper, a new rail-to-rail current-starved delay element is proposed which not only presents good linearity for the voltage-delay curve over the input range of ground to supply voltage, but also it consumes a dynamic power only during the transition times without consuming any static power. The proposed delay element is designed and simulated in a 0.13-µm CMOS technology with a supply voltage of 1.2V. Post-layout simulation results demonstrate that the proposed circuit has a linear voltage-delay transfer function with a voltage-to-time gain of −1.33ps/mV. Moreover, when samples of a full-scale sin-wave input signal are applied to the proposed circuit with a clock frequency of 100MHz, the power consumption is 30µW, and signal-to-noise-and-distortion ratio (SNDR) of the output delay times is 30.4dB, making it suitable for use in a time-based analog-to-digital converter with up to 5-bit resolution.

A Model for the Metastability Delay of Sequential Elements

It is well known that every sequential element may become metastable when provided with marginal inputs, such as input transitions occurring too close or input voltage not reaching a defined HI or LO level. In this case the sequential element requires extra time to decide which digital output level to finally present, which is perceived as an output delay. The amount of this delay depends on how close the element’s state is to the balance point, at which the delay may, theoretically, become infinite. While metastability can be safely avoided within a closed timing domain, it cannot be completely ruled out at timing domain boundaries. Therefore it is important to quantify its effect. Traditionally this is done by means of a “mean time between upsets” (MTBU) which gives the expected interval between two metastable upsets. The latter is defined as the event of latching the still undecided output of one sequential element by a subsequent one. However, such a definition only makes sense in a time-safe environment like a synchronous design. In this paper we will extend the scope to so-called value-safe environments, in which a sequential element can safely finalize its decision, since the subsequent one waits for completion before capturing its output. Here metastability is not a matter of “failure” but a performance issue, and hence characterization by MTBU is not intuitive. Therefore we will put the focus on the delay aspect and derive a suitable model. This model extends existing approaches by also including the area of very weak metastability and thus providing complete coverage. We will show its validity through comparison with transistor-level simulation results for the most popular sequential elements in different implementations, point out its relation to the traditional MTBU model parameters, namely [Formula: see text] and [Formula: see text], and show how to use it for calculating the performance penalty in a value-safe environment.

Extremum Seeking for Static Maps With Delays

In this paper, we address the design and analysis of multi-variable extremum seeking for static maps subject to arbitrarily long time delays. Both Gradient and Newton-based methods are considered. Multi-input systems with different time delays in each individual input channel as well as output delays are dealt with. The phase compensation of the dither signals and the inclusion of predictor feedback with a perturbation-based (averaging-based) estimate of the Hessian allow to obtain local exponential convergence results to a small neighborhood of the optimal point, even in the presence of delays. The stability analysis is carried out using backstepping transformation and averaging in infinite dimensions, capturing the infinite-dimensional state due the time delay. In particular, a new backstepping-like transformation is introduced to design the predictor for the Gradient-based extremum seeking scheme with multiple and distinct input delays. The proposed Newton-based extremum seeking approach removes the dependence of the convergence rate on the unknown Hessian of the nonlinear map to be optimized, being user-assignable as in the literature free of delays. A source seeking example illustrates the performance of the proposed delay-compensated extremum seeking schemes.

Conic Bounds for Systems Subject to Delays

Linear matrix inequality conditions implying conic bounds are developed for stable linear time-invariant systems with input, output, and/or state delays. Combined with the Conic Sector Theorem, this enables the design of output-feedback controllers ensuring closed-loop input-output stability that is robust to certain maximum delays. These contributions are used in a numerical example to design a nearly-optimal controller with guaranteed input-output-stability for a range of delays and improved performance relative to an $\mathcal{H}_{2}$ -optimal controller designed for the nominally undelayed system.

Output transformations and separation results for feedback linearisable delay systems

ABSTRACTThe class of strict-feedback systems enjoys special properties that make it similar to linear systems. This paper proves that such a class is equivalent, under a change of coordinates, to the wider class of feedback linearisable systems with multiplicative input, when the multiplicative terms are functions of the measured variables only. We apply this result to the control problem of feedback linearisable nonlinear MIMO systems with input and/or output delays. In this way, we provide sufficient conditions under which a separation result holds for output feedback control and moreover a predictor-based controller exists. When these conditions are satisfied, we obtain that the existence of stabilising controllers for arbitrarily large delays in the input and/or the output can be proved for a wider class of systems than previously known.

A Wide-Area Damping Controller Considering Network Input and Output Delays and Packet Drop

This paper presents the development of a novel synchrophasor measurement-based wide-area centralized damping controller to improve the stability of a power system in presence of time-varying delay and packet dropout in the communication network. Two different strategies have been adopted to deal with the input and the output delays. In the first strategy, the system output delay has been compensated by predicting the dynamics of the signals. In the second strategy, a wide-area controller, based on delay-range-dependent stability criteria, has been designed for the time-varying delays in the input signals. The network induced delays and the maximum amount of the consecutive packet dropout are assumed to be bounded. The controller parameters are optimally obtained using a trace minimization of certain matrix variables by formulating Linear Matrix Inequalities problem. The system has been identified by applying Prediction-Error-Minimization methodology, and proposing a new type of probing test input-signal. A new methodology has been proposed to obtain the feedback channel latency in real time. The proposed methodology has been simulated on New England 39-bus test system and also validated on a hardware testbed consisting of physical Phasor Measurement Units connected, in feedback loop, to a Real-Time Digital Simulator.

Proportional Retarded Controller to Stabilize Underactuated Systems with Measurement Delays: Furuta Pendulum Case Study

The design and tuning of a simple feedback strategy with delay to stabilize a class of underactuated mechanical systems with dead time are presented. A linear time-invariant (LTI) model with time delay of fourth order and a Proportional Retarded (PR) controller are considered. The PR controller is shown as an appealing alternative to the application of observer-based controllers. This paper gives a step forward to obtain a better understanding of the effect of output delays and related phenomena in mechatronic systems, making it possible to design resilient control laws under the presence of uncertain time delays in measurements and obtain an acceptable performance without using a derivative action. The Furuta pendulum is a standard two-degrees-of-freedom benchmark example from the class of underactuated mechanical systems. The configuration under study includes an inherent output delay due to wireless communication used to transmit measurements of the pendulum’s angular position. Our approach offers a constructive design and a procedure based on a combination of root loci and Mikhailov methods for the analysis of stability. Experiments over a laboratory platform are reported and a comparison with a standard linear state feedback control law shows the advantages of the proposed scheme.

Эксперименты по построению параллельной композиции временных автоматов

In this paper, we continue our work that is devoted to the parallel composition of Timed Finite State Machines (TFSMs). We consider the composition of TFSMs with timeouts and output delays. We held experiments in order to estimate how often parallel composition of nondeterministic TFSMs (with and without timeouts) has infinite sets of output delays. To conduct these experiments we have created two tools: the first one for converting TFSMs into automata (this tool is integrated into BALM-II), the second one for converting the global automaton of the composition into TFSM. As it was suggested in earlier works, we describe the infinite sets of output delays by linear functions, and it is important to know how often these sets of linear functions appear to justify the importance of future investigations of the TFSM parallel compositions (especially for deriving cascade composition). Results of the experiments show significant amount (around 50 %) of TFSMs with infinite number of output delays. We also estimate the size of the global automaton and the composed TFSM. In the experiments, we do not consider global automata with the huge number of states (more then 10000).

On the Output Controllability of Positive Discrete Linear Delay Systems

Necessary and sufficient conditions for output reachability and null output controllability of positive linear discrete systems with delays in state, input, and output are established. It is also shown that output reachability and null output controllability together imply output controllability.

Iterative learning fault diagnosis algorithm for non-uniform sampling hybrid system

For a class of non-uniform output sampling hybrid system with actuator faults and bounded disturbances, an iterative learning fault diagnosis algorithm is proposed. Firstly, in order to measure the impact of fault on system between every consecutive output sampling instants, the actual fault function is transformed to obtain an equivalent fault model by using the integral mean value theorem, then the non-uniform sampling hybrid system is converted to continuous systems with timevarying delay based on the output delay method. Afterwards, an observer-based fault diagnosis filter with virtual fault is designed to estimate the equivalent fault, and the iterative learning regulation algorithm is chosen to update the virtual fault repeatedly to make it approximate the actual equivalent fault after some iterative learning trials, so the algorithm can detect and estimate the system faults adaptively. Simulation results of an electro-mechanical control system model with different types of faults illustrate the feasibility and effectiveness of this algorithm.