Keywords: Sampled-Data Control, Sampled-Data and Delays, Delay Compensation
Abstract: The paper provides a new class of passivity-based controllers (PBCs) for stabilizing sampled-data input-delayed dynamics at a desired equilibrium via energy-balancing (EB) and reduction. Given a nonlinear dynamics under piecewise constant and retarded input, we first exhibit a new dynamics (the reduced dynamics) that is free of delays and equivalent to the original one. Accordingly, we design the digital controller assigning a suitable energetic behaviour to the reduced delay-free model with a stable target equilibrium. Then, it is proved that such a controller solves the EB-PBC problem on the original retarded system. The results are illustrated over a simple mechanical system.

Keywords: Hybrid Systems and Delays, Sampled-Data and Delays, Stabilization
Abstract: This paper studies sampled-data control of a class of nonlinear systems with input delay by memoryless feedback. A sampled-data nonsmooth feedback controller is first

developed based on the emulation method and the adding a power integrator (AAPI) technique Lin and Qian [2000], Qian and Lin [2001]. With the aid of Lyapunov-Krasovskii functional theorem, together with robust control, we then prove that the proposed memoryless sampled-data controller renders the hybrid closed-loop systems with delay globally asymptotically stable, if the input delay and sampling period are limited. The family of uncertain systems under consideration goes beyond the global Lipschitz or linear growth condition and is genuinely nonlinear in the sense that it contains uncontrollable unstable linearization and is not smoothly stabilizable, even locally. Application of the nonsmooth sampled-data control scheme is illustrated by a simplified under-actuate mechanical system with input delay.

Keywords: Control Design, Sampled-Data Control, Sampled-Data and Delays
Abstract: In this paper, the quantized sampled-data leaderless consensus tracking problem of nonlinear time--delay multi--agent systems (MASs) is studied. In particular, a new methodology for the design of quantized sampled--data event--triggered controllers achieving the leaderless consensus tracking of nonlinear MASs affected by state--delays is proposed. Firstly, the notion of steepest descent consensus feedback (SDCF), induced by a general class of Lyapunov--Krasovskii functionals, is introduced. Then, it is proved that there exist a suitably accurate quantization of the input channels and a suitably small maximum inter--sampling time such that: the digital implementation of SDCFs (continuous or not), with an event-triggered mechanism to update the control law only when necessary, achieves the leaderless consensus tracking in a semi--global practical sense of the related closed--loop MAS. The stabilization in the sample-and-hold sense theory is used as a tool for proving the results. The possible non--uniform quantization of the input channels is considered. Moreover, the case of time--varying sampling intervals as well as the stability analysis of the inter--sampling system behaviour is included in the theory here developed. An example is studied in order to validate the results.

Keywords: Observation and Observer Design, Modeling and Identification
Abstract: We provide a new class of finite-time observers for continuous-time nonlinear systems that are affine in the unmeasured state variable and that also contain unknown constant parameters. Our method provides exact values of the state variables and of the constant parameters, in a fixed finite time that is independent of the initial values. We also provide analogs where there is a known delay in the measurements, and for discrete-time systems. Our approach does not rely on an adaptive controller, and is suitable for computing exact values of constant weights in artificial neural network representations of additive uncertainties in the dynamics. Our example illustrates the ease with which our assumptions can be verified in practice.

Keywords: Sampled-Data and Delays, Stabilization, Control Design
Abstract: In this paper, the practical prescribed-time sampled-data control problem of a class of triangular nonlinear systems satisfying a linear growth condition is studied. With the help of some properties of a class of parametric Lyapunov equations (PLEs) and by constructing a time-varying Lyapunov-like function, a linear time-varying feedback controller is designed to make the states of the closed-loop system converge to an arbitrarily small neighbourhood of the origin in any prescribed time, while the control siginals are guaranteed to be bounded. A numerical example validates the effectiveness of the proposed method.

Keywords: Delay Compensation, Traffic Flow and Transportation Systems, Predictor-based Control
Abstract: Feedback information and actuation delays in Connected and Automated Vehicle (CAV) systems are detrimental to the string stability of CAV platoons. A generic approach is proposed to design platooning controllers that explicitly compensate for delays in communication, sensors and vehicle actuators and can be applied to platoons with different communication topology and different spacing policies. The main mechanism behind the delay-compensating design is to facilitate the host vehicle's future status (thus compensating for actuation delay) to track the preceding vehicles' history status (thus compensating for communication and sensing delays). This is realized by reformulating the desired spacing policies. Controller analysis shows the string stability of the proposed framework is guaranteed under delays from heterogeneous sources. Simulation is carried out to compare the string-stability performance of the designed systems with the baseline controllers without delay compensation. Simulation results verify that our approach generates controllers that require smaller time gap/spacing to keep the string stability of the systems than baseline controllers.

Keywords: Frequency-domain Methods, Networks and Networked Systems, Traffic Flow and Transportation Systems
Abstract: This work shows that, under a particular connectivity policy, a traffic network system which may be stable with few vehicles, may become unstable in large scale and this fragility can be remedied by considering a policy that introduces additional links among the vehicles.

Keywords: Traffic Flow and Transportation Systems, Stabilization, Control Design
Abstract: A hierarchical lane-keeping controller of passenger cars is analyzed, with the consideration of feedback delay in the control loop. The higher-level controller generates the desired steering angle based on the delayed feedback of the lateral position and yaw angle of the vehicle. The feedback delay of the lateral position and the yaw angle are treated separately in the model, therefore more general sensor setups and estimation algorithms can be handled. A lower-level proportional-integral-derivative power steering controller ensures that the desired steering angle signal is followed properly. The linear stability analysis of the resulting closed-loop system is performed, with a focus on the controller parameters and the delay values. The optimal control gains, leading to the fastest decay of the solution are also investigated in detail. The results are showcased with the help of stability charts and numerical simulations.

Keywords: Traffic Flow and Transportation Systems, Control Design, Modeling and Identification
Abstract: This paper extends the framework for conflict resolution to multiple vehicles with different automation levels, while considering time delays in vehicle dynamics and in vehicle-to-everything (V2X) communication. Using reachability analysis, we interpret the V2X-based vehicle status information to enable real-time decision making and control of a connected automated vehicle interacting with multiple connected vehicles. We reveal the effects of time delays in such mixed-autonomy environment, and demonstrate the effectiveness of the proposed conflict resolution strategies using simulations with real highway traffic data.

Keywords: Traffic Flow and Transportation Systems, Control Design, Predictor-based Control
Abstract: Safe longitudinal control is discussed for a connected automated truck traveling behind a preceding connected vehicle. A controller is proposed based on control barrier function theory and predictor feedback for provably safe, collision-free behavior by taking into account the significant response time of the truck as input delay and the uncertainty of its dynamical model as input disturbance. The benefits of the proposed controller compared to control designs that neglect the delay or treat the delay as disturbance are shown by numerical simulations.

Keywords: Predictor-based Control, Traffic Flow and Transportation Systems, Frequency-domain Methods
Abstract: The stabilization problem of a platoon of Adaptive Cruise Control (ACC) equipped vehicles in the presence of input-delay is studied. We apply a dynamic predictor that guarantees a safe implementation in compensating input-delays. A proportional-integral controller is embedded in the prediction scheme to guarantee that the platoon meets the speed of the leading vehicle while ensuring a secure inter-vehicle space without steady-state errors.

Keywords: Infinite-dimensional Systems and PDEs Models, Feedback Control, Robust Analysis and Control
Abstract: The paper presents a dynamic event-triggering mechanism for the constant and the localized damped linear Schrödinger equation. The following results are tackled: the existence of solution to the closed-loop event-triggered control system; the avoidance of the Zeno behavior due to the absence of any accumulation point of the sequence of time instants and the exponential stability based on energy estimate through the observability inequality. A simulation example based on the one-dimensional Schrödinger equation is presented to validate the theoretical results.

Keywords: Transportation Systems, Robust Analysis and Control, Regulation
Abstract: This paper proposes a cascaded train speed regulator that is robust to actuator limitations and feedback loop delays. In order to limit in-train forces, we first impose a jerk limitation on the speed reference trajectories, which are constructed from predefined waypoints using a first-integral and quadratic spline interpolation. The speed of the train is then regulated around the constructed reference using a cascaded control law, based on an optimized acceleration profile that respects the imposed jerk constraints. The nonlinear sections of this profile mimic the minimal-time synthesis and manage the motor locomotive torque limitations, while its linear section is tuned in order to ensure the required robustness, with respect to actuator delays and measurement filtering. The performance of the control law is assessed via simulations on a train model, using references that drive the system toward its nonlinear domain.

Keywords: Robust Analysis and Control, Feedback Control
Abstract: This paper presents a parameterization and robustness analysis of state-feedback controllers that quadratically stabilize a discrete-time linear system with single control input corrupted by amplitude bounded disturbances. Stabilizing controllers are parameterized by a positive definite matrix corresponding to the state weight matrix in cheap control. This parameter determines the region where the state is constrained to lie in a time-average sense. This region is inscribed in the boundary of an invariant set, where the state is always constrained to lie. Also the state can escape from anywhere in a scaled invariant set, which is inscribed in the boundary of this region. These observations enable to reveal the state components robust or sensitive to the input disturbances.

Keywords: Observers, Feedback Control, Robust Analysis and Control
Abstract: The topic of nonfragile observer design for a class of one sided Lipschitz nonlinear systems with quantized inputs is investigated in this study. The one-sided Lipschitz and quadratically innerbounded conditions were used to obtain less conservative synthesis requirements for the observer design. Sufficient conditions, stated in terms of linear matrix inequalities, are supplied using auxiliary variables and a decoupling method to ensure the resilience of the quantized closed-loop. The controller and observer gains may then be found in the same process. An example generated from a nonlinear DC motor model is provided to demonstrate the efficiency of the suggested technique.

Keywords: Robust Analysis and Control, Time-invariant Systems
Abstract: An event-triggered robust distributed model predictive control (MPC) problem for multi-agent systems with bounded disturbances is studied in this paper. For each agent, a two-step triggering scheme is designed to decide when to solve its individual optimization problem, leading to reduced usage of computational resources. This scheme synthesizes a two-step event verification with a specified triggering condition and a waiting horizon based on a prediction model and a robust positively invariant set of the corresponding agent. The theoretical conditions for recursive feasibility and closed-loop robust stability are developed. The consensus among all agents is achieved. A simulation example is provided to show the effectiveness of the proposed approach.

Keywords: Uncertain Systems - SSSC, Descriptor Systems, Disturbance Rejection
Abstract: The H∞ filtering problem for continuous-time linear systems with polytopic uncertainty is addressed in this study. First, using several well-known lemmas from the literature, adequate analysis requirements in terms of linear matrix inequalities (LMIs) are developed, ensuring the asymptotic stability of the filtering error systems with the specified H∞ performance level γ. We will then concentrate on the design of filter gains using less restricted LMIs by combining several strategies that utilize slack variables and descriptor representation. Finally, numerical examples are presented to demonstrate the efficacy of the suggested technique in contrast to current works.