On the possible divergence of the projection algorithm

By means of an example, the authors show that the sequence of estimates generated by the projection algorithm does not always converge. The authors' construction shows that convergence is not automatically among the properties that can be derived without additional assumptions on the input sequenc

Adaptive tracking control of nonholonomic systems: an example

We study an example of an adaptive (state) tracking control problem for a four-wheel mobile robot, as it is an illustrative example of the general adaptive state-feedback tracking control problem. It turns out that formulating the adaptive state-feedback tracking control problem is not straightforward, since specifying the reference state-trajectory can be in conflict with not knowing certain parameters. Our example illustrates this difficulty and we propose a problem formulation for the adaptive state-feedback tracking problem that meets the natural prerequisite that it reduces to the state-feedback tracking problem if the parameters are known. A general methodology for solving the problem is derive

A Stochastic Model Predictive Control Approach for Driver-Aided Intersection Crossing With Uncertain Driver Time Delay

We investigate the problem of coordinating human-driven vehicles in road intersections without any traffic lights or signs by issuing speed advices. The vehicles in the intersection are assumed to move along an a priori known path and to be connected via vehicle-to-vehicle communication. The challenge arises with the uncertain driver reaction to a speed advice, especially in terms of the driver reaction time delay, as it might lead to unstable system dynamics. For this control problem, a distributed stochastic model predictive control concept is designed which accounts for driver uncertainties. By optimizing over scenarios, which are sequences of independent and identically distributed samples of the uncertainty over the prediction horizon, we can give probabilistic guarantees on constraint satisfaction. Simulation results demonstrate that the scenario-based approach is able to avoid collisions in spite of uncertainty while the non-stochastic baseline controller is not.Comment: Submitted to European Control Conference 2019 (ECC19

Linear controllers for tracking chained-form systems

In this paper we study the tracking problem for the class of nonholonomic systems in chained-form. In particular, with the first and the last state component of the chained-form as measurable output signals, we suggest a solution for the tracking problem using output feedback by combining a time-varying state feedback controller with an observer for the chained-form system. For the stability analysis of the "certainty equivalence type" of controller we use a cascaded systems approach. The resulting closed loop system is globally K-exponentially stable

Impact Sensitivity Analysis of Cooperative Adaptive Cruise Control Against Resource-Limited Adversaries

Cooperative Adaptive Cruise Control (CACC) is a promising technology that allows groups of vehicles to form in automated tightly-coupled platoons. CACC schemes exploit Vehicle-to-Vehicle (V2V) wireless communications to exchange kinematic information among adjacent vehicles. However, the use of communication networks brings security concerns as cyberattacks could access the vehicles' internal networks and computers to disrupt their operation and even cause crashes. In this manuscript, we present a sensitivity analysis of standard CACC schemes against a class of resource-limited attacks. We present a modelling framework that allows us to systematically compute outer ellipsoidal approximations of reachable sets induced by attacks. We use the size of these sets as a security metric to quantify the potential damage of attacks entering the dynamics at different points and study how two key system parameters (sampling and headway constant) change these metrics. We carry out the latter sensitivity analysis for two different controller implementations (as given the available sensors there is an infinite number of realizations of the same controller) and show how different implementations can significantly affect the impact of attacks. We present extensive simulation experiments to illustrate our ideas

Saturated stabilization and tracking of a nonholonomic mobile robot

Abstract This paper presents a framework to deal with the problem of global stabilization and global tracking control for the kinematic model of a wheeled mobile robot in the presence of input saturations. A model-based control design strategy is developed via a simple application of passivity and normalization. Saturated, Lipschitz continuous, time-varying feedback laws are obtained and illustrated in a number of compelling simulations

Output feedback tracking of ships

Abstract-In this brief, we consider output feedback tracking of ships with position and orientation measurements only. Ship dynamics are highly nonlinear, and for tracking control, as opposed to dynamic positioning, these nonlinearities have to be taken into account in the control design. We propose an observer-controller scheme which takes into account the complete ship dynamics, including Coriolis and centripetal forces and nonlinear damping, and results in a semi-globally uniformly stable closed-loop system. Furthermore, a gain tuning procedure for the observer-controller scheme is developed. Experimental results are presented where the observer-controller scheme is implemented onboard a Froude scaled 1:70 model supply ship. The experimentally obtained results are compared with simulation results under ideal conditions and both support the theoretical results on semi-global exponential stability of the closed-loop system

Nonlinear models for control of manufacturing systems

Current literature on modeling and control of manufacturing systems can roughly be divided into three groups: flow/fluid models, queueing theory, and discrete event models. Most fluid models describe linear time-invariant controllable systems without any dynamics. These models mainly focus on throughput and are not concerned with cycle time. Queuing theory deals with relationships between throughput and cycle time, but is mainly concerned with steady-state analysis. In addition, queueing models are not suitable for control theory. Discrete event models suffer from ``state-explosion''. Simple models of manufacturing systems can be studied and analyzed, but for larger problems the dimension of the state grows exponentially. In addition, most control problems studied are supervisory control problems: the avoidance of undesired states. An important class of interesting manufacturing control problems asks for proper balancing of both throughput and cycle time for a large nonlinear dynamical system that never is in steady state. None of the mentioned models is able to deal with these kind of control problems. In this paper, models are presented with are suitable for addressing this important class of interesting manufacturing control problems

An example of a bounded tracking controller

A prototype example for designing a globally bounded tracking controller is presented. The solution is obtained by using composite or switching controllers. First, the system is steered `close' to the desired trajectory, after which a local tracking controller is applied. For the considered system, both controllers are bounded and therefore boundedness of the composite controller follows. A simulation illustrates the idea