Arben Çela

Optimal integrated control and scheduling of networked control systems with communication constraints: application to a car suspension system

This brief addresses the problem of the optimal control and scheduling of networked control systems over limited bandwidth deterministic networks. Multivariable linear systems subject to communication constraints are modeled in the mixed logical dynamical (MLD) framework. The translation of the MLD model into the mixed integer quadratic programming (MIQP) formulation is described. This formulation allows the solving of the optimal control and scheduling problem using efficient branch and bound algorithms. Advantages and drawbacks of online and offline scheduling algorithms are discussed. Based on this discussion, a computationally efficient online scheduling algorithm, which can be seen as a compromise, is presented and its performance is evaluated. Finally, this algorithm, called optimal pointer placement (OPP) scheduling algorithm, is applied to the control and scheduling of a car suspension system.

Optimal Real-Time Scheduling of Control Tasks With State Feedback Resource Allocation

This paper proposes a new approach for the optimal integrated control and real-time scheduling of control tasks. First, the problem of the optimal integrated control and nonpreemptive off-line scheduling of control tasks in the sense of the H2 performance criterion is addressed. It is shown that this problem may be decomposed into two subproblems. The first subproblem aims at finding the optimal nonpreemptive off-line schedule and may be solved using the branch and bound method. The second subproblem uses the lifting technique to determine the optimal control gains, based on the solution of the first subproblem. Second, an efficient online scheduling algorithm is proposed. This algorithm, called the reactive pointer placement (RPP) scheduling algorithm, uses the plant state information to dispatch the computational resources in a way that improves control performance. Control performance improvements as well as stability guarantees are formally proven. Finally, simulations as well as experimental results are presented in order to illustrate the effectiveness of the proposed approach.

Technical communique: Stability analysis of neutral systems with mixed delays

The stability of neutral systems with mixed delays is studied in this paper. A new discretized Lyapunov functional method is proposed. The method in this paper is less conservative than the existing ones and the results are very close to the analytical results. In addition, this method allows the coefficient matrix of the neutral term to have time-varying uncertainties.

Optimal scheduling of control tasks with state feedback resource allocation

In a large category of embedded systems, computing resources are limited. Consequently, they need to be exploited as efficiently as possible. Many research works have demonstrated that considering jointly the problems of control and scheduling leads to a better control performance, given the same computing resources. In this paper, the problem of the optimal integrated control and non-preemptive off-line scheduling of control tasks in the sense of the H2 performance criterion is addressed. It is shown that this problem can be decomposed into two sub-problems which can be solved separately. The first sub-problem aims at finding the optimal non-preemptive off-line schedule, and is solved using efficient branch and bound algorithms. The second sub-problem uses the lifting technique to determine the optimal control gains, based on the solution of the first sub-problem. Finally, in order to improve the control performance by dynamically allocating the computational resources, an efficient on-line scheduling heuristic is proposed

Event Driven Intelligent PID Controllers with Applications to Motion Control

Abstract A novel type of reduced complexity controller is proposed. It is the combination of model free control and event triggered control. The robustness of model free control, especially for badly known dynamics, is added to the event based scheme. The performances of the proposed method are illustrated in two motion controls, vehicular longitudinal control and quadrotor control. Comparisons with existing control schemes are also proposed.

Analysis of drilling vibrations: A time-delay system approach

The main purpose of this study is the description of the qualitative dynamical response of a rotary drilling system with a drag bit, using a model that takes into consideration the axial and the torsional vibration modes of the bit. The studied model, based on the interface bit-rock, contains a couple of wave equations with boundary conditions consisting of the angular speed and the axial speed at the top additionally to the angular and axial acceleration at the bit whose contain a realistic frictional torque. Our analysis is based on the center manifold Theorem and Normal forms theory whose allow us to simplify the model.

Optimal Integrated Control and Scheduling of Systems with Communication Constraints

This paper addresses the problem of the optimal control and scheduling of Networked Control Systems over limited bandwidth time-slotted networks. Multivariable linear systems subject to communication constraints are modeled in the Mixed Logical Dynamical (MLD) framework. The translation of the MLD model into the Mixed Integer Quadratic Programming (MIQP) formulation is described. This formulation allows the solving of the optimal control and scheduling problem using efficient branch and bound algorithms. Advantages and drawbacks of on-line and off-line scheduling algorithms are discussed. Based on this discussion, an efficient on-line scheduling algorithm, which can be seen as a compromise, is presented and its performance is evaluated.

Some problems in the stability of networked-control systems with periodic scheduling

This article addresses three stability problems related to networked-control systems (NCSs) with periodic scheduling, where control systems may have multiple samplings in a hyperperiod (a hyperperiod is a periodically repeated scheduling sequence for all tasks in an NCS). As expected, the analysis of a system with multiple samplings is much richer than the case with single sampling. For example, a system with two samplings may be stable (unstable) even if it is unstable (stable) when sampled by either sampling. In this context, it is important to understand how network-induced delays and multiple samplings affect the systems stability. In this article, three particular stability problems involving constant and/or time-varying parameters are investigated, and the corresponding stability regions are derived. Numerical examples and various discussions complete the presentation.

Energy Optimal Real-Time Navigation System

The rapid development of Mobile Internet and Smart Devices and advent of a new generation of Intelligent Transportation Systems (ITS) increase information about present driving conditions and make its prediction possible. Real time traffic information systems (TIS) like SYTADIN help in route to destination planning and traffic state prediction. Energy-optimal routing for electric vehicles creates novel algorithmic challenges where the computation complexity and the quality of information on traffic state are the main issues. This complexity is induced by the possible negative values of edge energy as well as the variability of route and vehicle variables which render the standard algorithms unsuitable. In this paper we present an Energy Optimal Real Time Navigation System (EORTNS), implemented on Samsung Galaxy Tab, capable of calculating the route to destination based on information flow obtained from SYTADIN. As an application example we propose a real time energy management for a Hybrid Electrical Vehicle (HEV) composed of batteries and Super-Capacitors (SC). The EORTNS is not only capable of energy optimal route to destination calculation with respect to traffic state but also operates the On-Board power splitting between batteries and Super-Capacitors.

Control of Drilling Vibrations: A Time-Delay System-Based Approach

Abstract The main purpose of this study is the control of both axial and torsional vibrations occurring along a rotary oilwell drilling system. This work completes a previous authors paper (Boussaada et al. [2012a]) which presents the description of the qualitative dynamical response of a rotary drilling system with a drag bit, using a model that takes into consideration the axial and the torsional vibration modes of the bit. The studied model, based on the interface bit-rock, contains a couple of wave equations with boundary conditions consisting of the angular speed and the axial speed at the top additionally to the angular and axial acceleration at the bit whose contain a realistic frictional torque. Our analysis is based on the center manifold theorem and normal forms theory whose allow us to simplify the model. By this way we design two control laws allowing to suppress the undesired vibrations guaranteeing a regular drilling process.