Ragia I. Badr

Stability and performance robustness for multivariable linear systems

Abstract This paper deals with both aspects of stability and performance robustness of linear systems in the time domain. A linear time-invariant feedback control law which yields the largest set of parameter variations is first determined. It is then used as an initial guess for designing a robust control law which produces satisfactory performance for each of several operating points of the system given a priori. The stability robustness properties of the resulting control law is also studied. The proposed approach is applied to an example yielding larger stability bounds including satisfactory performance in comparison with recently reported results.

Robust decentralized regulator design for multivariable large-scale system

The authors present a design methodology of robust decentralized regulators for discrete-time large-scale systems with dynamic interconnections and structural variations. System uncertainties are accounted for through the consideration of the various modes of possible configurations of the actuators. The method is based on the minimization of a discrete linear regulator performance, with variable configuration changes that are governed by a Markov chain. This methodology yields a classification of the subsystem into those which are inherently robust and those which are not.<<ETX>>

Dynamic inertia weight artificial bee colony versus GA and PSO for optimal tuning of PID controller

Artificial bee colony (ABC) algorithm is one of the most recently used optimisation algorithms. ABC algorithm has been extracted from the intelligent behaviour of honeybees swarm. Artificial bee colony has limitations due to its stochastic searching characteristic and complex computation that result in slow convergence to the global optimum solution. Inertia weight-based ABC method is introduced to improve the performance of the standard ABC algorithm by controlling the effect of the initial population in the new expected solution which leads improvement in the convergence rate of ABC. This work compares the performance of inertia weight ABC algorithm with the standard ABC, PSO, and GA algorithms in tuning the proportional-integral-derivative (PID) controllers for the ball and hoop system which represents a system of complex industrial processes, known to be nonlinear and time variant. Simulation results show that inertia weight ABC algorithm is highly competitive, often outperforming PSO and GA algorithms and achieving convergence rate better than the standard ABC.

Adaptive PID Controller Using RLS for SISO Stable and Unstable Systems

The proportional-integral-derivative (PID) is still the most common controller and stabilizer used in industry due to its simplicity and ease of implementation. In most of the real applications, the controlled system has parameters which slowly vary or are uncertain. Thus, PID gains must be adapted to cope with such changes. In this paper, adaptive PID (APID) controller is proposed using the recursive least square (RLS) algorithm. RLS algorithm is used to update the PID gains in real time (as system operates) to force the actual system to behave like a desired reference model. Computer simulations are given to demonstrate the effectiveness of the proposed APID controller on SISO stable and unstable systems considering the presence of changes in the systems parameters.

A new on-line observer-based controller for leader-follower formation of multiple nonholonomic mobile robots

Abstract In this paper, a novel on-line observer-based trajectory tracking strategy for leader-follower formation of multiple nonholonomic mobile robots is developed. In the proposed strategy, a leader robot follows a certain trajectory whereas a number of followers track the leader as specified by a formation protocol. Unlike other techniques in the literature, a predefined trajectory is not required, and it can be changed on-line. Moreover, this strategy aims to have a fast transient response without showing undesired overshoots. To achieve this feature, a new observer is introduced. Based on the output of that observer, a control strategy with two components is derived. The first control component is responsible for tracking the desired trajectory, whereas the second control component is used to regulate the robot to its desired steady state position. The stability of the closed loop control system is investigated. Applications of the proposed observer-based controller to different case studies are presented to illustrate the effectiveness, robustness and applicability of the developed technique. To show the superiority of proposed controller, its performance in a trajectory tracking application is compared to that of a Lyapunov-based controller.

Alternative Approach to Use RLS Algorithm in Multivariable Online Adaptive PID Controllers for MIMO Systems

ABSTRACT The proportional-integral-derivative (PID) is widely used in industrial control systems due to its simplicity. For multi-input multi-output (MIMO) systems, choosing the PID gain values is a difficult task especially that in most applications system parameter variations and changes in operating conditions occur. Thus, there is necessity to find parameters adjustment method in which PID gains should be adapted to handle such changes. This paper is concerned with the design of a multivariable adaptive PID (APID) controller in which recursive least square (RLS) algorithm is used as an adaptation mechanism. The RLS algorithm, on the contrary of its usual application as an identification method, is used in the proposed controller to update the PID gains online forcing the system to behave like a desired reference model. Unlike other techniques, the proposed multivariable APID controller has the advantage that it does not impose restrictions on the system structure such as being stable, square, minimum phase, nor almost restrict positive real. Since stability is a vital issue in the evaluation of control systems, therefore stability analysis of the proposed approach is developed using Lyapunov stability theory. Comparative simulation results demonstrate the superiority of the proposed multivariable APID controller over another two different controllers when applied to MIMO systems especially for unstable systems when the controlled systems suffer from parameter variations or uncertainties.

Interference Mitigation and Capacity Enhancement Using Constraint Field of View ADR in Downlink VLC channel

The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio-frequency wireless connections with high-speed ones. Visible light communication (VLC) is a promising license free indoor wireless technology that could offer high-speed connections. However, both co-channel interference (CCI) from more neighbour transmitters and inter-symbol interferences (ISI) from multipath reflections limit the performance of VLC downlink channel. In this study, a constraint field of view angular diversity receiver (CFOV-ADR) is proposed to mitigate these limitations. By optimising the photodetectors (PD) field of view (FOV) angle, the line of sight CCI could be totally eliminated and the ISI could be significantly reduced. The optimal range for FOV angle is calculated in a typical indoor scenario. Furthermore, the zero-forcing (ZF) algorithm is applied to the conventional ADR (ADR-ZF) which can significantly eliminate the ISI components. The received optical signal-to-interference-plus-noise ratio (SINR) is tested at various room positions. The simulation results show that the proposed CFOV-ADR can achieve higher SINR performance than single receiver, conventional ADR, and ADR-ZF at all positions and orientations.

A Novel Variable Population Size Artificial Bee Colony Algorithm with Convergence Analysis for Optimal Parameter Tuning

This paper introduces a novel algorithm called variable population size artificial bee colony (VPS-ABC) optimization algorithm. VPS-ABC is proposed to overcome the impact of the effect of initial population and improve the convergence rate of classical ABC. The main idea is based on reducing the number of food sources gradually and moving the bees towards the global best food source in each re-initialization process. Moreover, an analysis for convergence of the ABC algorithm is proofed in details. The convergence analysis is based on the relation between ABC variants and the general solution of the food source regeneration equation. To show the fitness of the proposed algorithm, a comparison is made between VPS-ABC versus classical ABC, PSO, and GA algorithms in tuning the proportional-integral-derivative (PID) controllers. Simulation results show that VPS-ABC algorithm is highly competitive, often outperforming PSO and GA algorithms.

Novel PID Tracking Controller for 2DOF Robotic Manipulator System Based on Artificial Bee Colony Algorithm

Abstract This study presents a well-developed optimization methodology based on the dynamic inertia weight Artificial Bee Colony algorithm (ABC) to design an optimal PID controller for a robotic arm manipulator. The dynamical analysis of robotic arm manipulators investigates a coupling relation between the joint torques applied by the actuators and the position and acceleration of the robot arm. An optimal PID control law is obtained from the proposed (ABC) algorithm and applied to the robotic system. The designed controller optimizes the trajectory of the robot’s end effector for a time-variant input and makes the robot robust in the presence of external disturbance.

Robust observer-based controllers for systems with non-homogeneous uncertainties

The author presents a unified approach to the stabilization problem for uncertain systems using a reduced order observer based on state feedback. A well-developed algorithm is presented that not only yields an optimum Lyapunov matrix in a systematic technique, but also expands the allowable set of tolerable uncertainty through introducing the concept of a nonhomogeneous polyhedron of large parameter variations. A comparative example involving the AFIT/F16 flying at 3000 ft and Mach 0.6 is used to demonstrate the proposed technique while displaying its efficiency. The proposed technique yields wider ranges of parameter variations than those reported in the literature.<<ETX>>