Abdul-Wahid A. Saif

Strong stabilization of MIMO systems via H ∞ optimization

In this paper, the strong stabilization problem of multivariable linear time-invariant systems is considered. The problem is reduced to a 2-block or 1-block H∞-optimization problem. The solution of this optimization problem, if satisfying an upper bound constraint which depends on an initial choice of a unimodular transfer function in RH∞, would be a stable stabilizing controller to the original system.

Simultaneous stabilization of MIMO systems via robustly stabilizing a central plant

In this note, a new formulation and solution to the simultaneous stabilization problem (SSP) is given. The new method is based on finding a central plant from a set of plants to be simultaneously stabilized. The theory of robust stabilization can then be applied to the central plant with a bounded perturbation, which encapsulates the plants to be stabilized, in order to solve the SSP.

Dissipativity analysis and design for uncertain Markovian jump systems with time-varying delays

This paper deals with the problems of dissipativity analysis and dissipativity-based controller design for Markovian jump systems with both time-varying delays and norm-bounded parametric uncertainties. Improved delay-dependent conditions for the system concerned to be strictly dissipative are established by using a mode-dependent Lyapunov-Krasovskii functional and introducing some slack variables. These conditions are expressed by means of linear matrix inequalities (LMIs) which are easy to check. It is also shown that these conditions are less conservative than those obtained by using the existing methods. The dissipativity synthesis problem is considered and on the basis of the obtained dissipativity conditions, both the state-feedback and dynamic output-feedback controllers are designed to guarantee the strict dissipativity of the closed-loop systems. Numerical examples are provided to demonstrate the utility of the developed methods.

Robust Quantized Approach to Fuzzy Networked Control Systems

This paper investigates the problem of robust H∞ control for uncertain discrete-time Takagi-Sugeno (T-S) fuzzy networked control systems (NCSs) with state quantization. A new model of network-based control with simultaneous consideration of network induced delays and packet dropouts is proposed. Using fuzzy Lyapunov-Krasovskii functional, we derive a less conservative delay-dependent stability condition for the closed NCSs. Robust H∞ fuzzy controller is developed for the asymptotic stabilization of the NCSs and expressed in linear matrix inequality-based conditions. Numerical simulation examples show the feasibility applications of the developed technique.

Strong stabilization of MIMO systems via unimodular interpolation in H

In this paper, the strong stabilization problem of multivariable linear timeinvariant systems is considered. The problem is categorized into minimum and non-minimum phase systems. When the given system is minimum phase, the solution requires a stable inverse of a particular stable transfer function matrix; while for a non-minimum phase system, the solution requires an inner-outer factorization, whose outer part is unimodular in RH, and an interpolation in RH. The formulation of the two cases will be modified so that the conditions for the existence of stable inverse or unimodularity of the outer part are satisfied. When the system is strictly proper it is shown that the problem is more technically involved.

Modified backstepping control of Quadrotor

In this paper, a modified backstepping approach will be developed and applied to control unmanned areial vehicles (UAVs), Quadrotor. In this modified backstepping approach, the number of control parameters is reduced by half compared with the classical back stepping approach used in the literature. Simulation is used to test the stability of the overall nonlinear Quadrotor system and compared with the classical one.

Quadrotor helicopter with tilting rotors: Modeling and simulation

Quadrotors have recently become a focus of research in Unmanned Aerial Vehicle (UAV) and flying robots applications. However, controlling the quadrotor dynamics is noticeably complex as the conventional quadrotor is underactuated. Some of the quadrotor motions are coupled with others which makes it impossible to achieve all the desired maneuvers. In this paper, a novel quadrotor design is proposed. The design increases the number of inputs from four in conventional quadrotors to twelve by allowing each rotor to tilt in two directions about its fixed frames. This addition aims to separate the quadrotor motions and give it more maneuverability and robustness. The model of the new design is introduced and several flights are simulated to show the superiority over conventional design.

Quadrotor with tiltable rotors for manned applications

Quadrotors have a great potential for transportation, commercial and military applications. In this paper, a quadrotor design is proposed for manned application. The design decouples all motions by allowing each rotor to tilt in two directions about its fixed frames. This modification improves the stability and safety of the quadrotor and gives it more maneuverability and robustness. The model is presented along with a proposed operator control panel. Several flight scenarios are also simulated to illustrate the superiority over conventional manned air vehicles.

Strong stabilization of MIMO systems: An LMI approach

In this paper, the strong stabilization problem of proper and non-minimum phase linear time-invariant multi-variable systems is considered. The formulation of the problem resulted in a sufficient condition in a form of linear matrix inequality (LMI) which will be solved using MATLAB LMI Toolbox. A necessary and sufficient condition is given in a form of quadratic matrix inequality, (QMI). It is proved that the solution of the linear part of the QMI satisfies the QMI.

Performance evaluation of DDS-Based middleware over wireless channel for reconfigurable manufacturing systems

Reconfigurable manufacturing systems (RMS) are rapidly becoming choice of production and manufacturing industry due to their quick adaptability to the ever-changing market demands while maintaining the quality and cost of the products. Such systems are usually decentralized in their monitoring and control and consist of heterogeneous components. Therefore, need arises for an interface that can mask the heterogeneity and provide smooth communication among these dissimilar components. Data Distribution Service (DDS) is a data-centric middleware standard based on Real-Time Publish/Subscribe (RTPS) protocol that fulfills the job of such interface in distributed systems. In this work, we present the idea of using DDS-based middleware over commonly used wireless channels like Bluetooth and Industrial WiFi to facilitate data communication in distributed control systems. A simulation model is developed to quantify various performance measures like latency, jitter, and throughput and to examine the suitability of aforementioned wireless channels in distributed monitoring and control environments. The model explores various communication scenarios based upon a practical case study. Obtained results serve as an empirical proof of concept that DDS can ensure reliable and timely data communication in firm real-time distributed control systems using common wireless channels and offer extensive control over various aspects of data transmission through its rich set of QoS policies.