arXiv subjects

Mahdi Sojoodi

Publications and source records attributed to Mahdi Sojoodi.

13 recordsLinked to original sources

arXiv2023

Convex Optimization of Bearing Formation Control of Rigid bodies on Lie Group

In this paper, the problem of reaching formation for a network of rigid agents over a special orthogonal group is investigated by considering bearing-only constraints as the desired formation. Each agent is able to gather the measurements with respect to other agents in its own body frame. So, the agents are coordinated-free concerning a global reference frame. Attracting to the desired formation is founded on solving an optimization problem for minimizing the difference between the instantaneous bearing between agents and their desired bearing. In order to have a unique global solution, the convex optimization method is implemented. Since the rotation matrices are not convex, the method of convex relaxation of rotation matrices space is used to embed the rotation matrices on the convex hull of the Lie group. Then the control law is designed to achieve the desired bearing with minimum energy consumption. Finally, a simulation example is provided to verify the results.

eess.SY↗

arXiv2023

Bearing and Distance Formation Control of Rigid Bodies in SE(3) with Bearing and Distance Constraints

Rigidity of the interaction graph is a fundamental condition for achieving the desired formation which can be defined in terms of distance or bearing constraints between agents. In this paper, for reaching a unique formation with the same scaling and orientation as the target formation, both distance and bearing constraints are considered for defining the desired formation. Besides, both distance and bearing measurements are also available. Each agent is able to gather the measurements with respect to other agents in its own body frame. So, the agents are coordinated-free concerning a global reference frame. On the other hand, the framework is embedded in SE(3). The control signal is designed based on a gradient descent method by introducing a cost function. Firstly, the formation problem is considered for bearing-only constraints in SE(3) configuration. Then, the formation control is expressed for the general case of both bearing and distance constraints. Furthermore, the essential conditions that guarantee reaching the desired formation are discussed. Finally, the validity of the proposed formation control is verified by numerical simulations.

eess.SY↗

arXiv2021

Consensus of a class of nonlinear fractional-order multi-agent systems via dynamic output feedback controller

This paper addresses the consensus of a class of uncertain nonlinear fractional-order multi-agent systems (FOMAS). First a fractional non-fragile dynamic output feedback controller is put forward via the output measurements of neighboring agents, then appropriate state transformation reduced the consensus problem to a stability one. A sufficient condition based on direct Lyapunov approach, for the robust asymptotic stability of the transformed system and subsequently for the consensus of the main system is presented. Additionally, utilizing S-procedure and Schur complement, the systematic stabilization design algorithm is proposed for fractional-order system with and without nonlinear term. The results are formulated as an optimization problem with linear matrix inequality constraints. Simulation results are given to verify the effectiveness of the theoretical results.

math.OC↗

arXiv2021

Dynamic robust stabilization of fractional-order linear systems with nonlinear uncertain parameters: An LMI approach

This paper considers the problem of robust stability and stabilization for linear fractional-order system with nonlinear uncertain parameters, with fractional order 0<a<2. A dynamic output feedback controller, with predetermined order, for asymptotically stabilizing such uncertain fractional-order systems is designed. The derived stabilization conditions are in LMI form. Simulation results of two numerical examples illustrate that the proposed sufficient theoretical results are applicable and effective for tackling robust stabilization problems. Keywords: Fractional-order system, nonlinear uncertain parameters, linear matrix inequality (LMI), robust stabilization, dynamic output feedback.

math.OC↗

arXiv2020

A novel LMI-based Method for Robust Stabilization of Fractional-order Interval Systems with $1\leα<2$

This paper deals with the problem of robust dynamic output feedback stabilization of interval fractional-order linear time invariant (FO-LTI) systems with the fractional order $1\leα<2$. In this study, a new formulation based on the null-space analysis of the system matrices is proposed using linear matrix inequalities (LMIs). The applied uncertain model is the most complete model of linear interval systems, in which all of the systems matrices are interval matrices. A robust dynamic output feedback controller is designed that asymptotically stabilizes the interval FO-LTI system, where no limiting constraint is assumed on the state space matrices of the uncertain system. Eventually, a numerical example with simulations is presented to demonstrate the effectiveness and correctness of the theoretical results.

eess.SY↗

arXiv2019

LMI-based robust stability and stabilization analysis of fractional-order interval systems with time-varying delay

This paper investigates the robust stability and stabilization analysis of interval fractional-order systems with time-varying delay. The stability problem of such systems is solved first, and then using the proposed results a stabilization theorem is also included, where sufficient conditions are obtained for designing a stabilizing controller with a predetermined order, which can be chosen to be as low as possible. Utilizing efficient lemmas, the stability and stabilization theorems are proposed in the form of LMIs, which is more suitable to check due to various existing efficient convex optimization parsers and solvers. Finally, two numerical examples have shown the effectiveness of our results.

eess.SY↗

arXiv2019

A class of non-linear fractional-order system stabilisation via fixed-order dynamic output feedback controller

This paper investigates the robust stabilisation of a class of fractional-order non-linear systems via fixed-order dynamic output feedback controller in terms of linear matrix inequalities (LMIs). The systematic stabilisation algorithm design for low-order controller based on direct Lyapunov approach is proposed. In the presented algorithm the conditions containing the bilinear variables are decoupled into separate conditions without imposing equality constraints or considering an iterative search of the controller parameters. There is no any limiting constraint on the state space matrices and also we assumed the most complete output feedback controller. Simulations results are given to approve the effectiveness and the straightforwardness of the proposed design.

math.OC↗

arXiv2019

Consensus of fractional-order multi-agent systems: Matrix inequality approach

math.OC↗

arXiv2018

Stability and Stabilization of Fractional-order Systems with Different Derivative Orders: An LMI Approach

Stability and stabilization analysis of fractional-order linear time-invariant (FO-LTI) systems with different derivative orders is studied in this paper. First, by using an appropriate linear matrix function, a single-order equivalent system for the given different-order system is introduced by which a new stability condition is obtained that is easier to check in practice than the conditions known up to now. Then the stabilization problem of fractional-order linear systems with different fractional orders via a dynamic output feedback controller with a predetermined order is investigated, utilizing the proposed stability criterion. The linear matrix inequality based procedure of developing stabilizing output feedback control is preserved in spite of the complexity of assuming the most complete linear controller model, with direct feedthrough parameter. The proposed stability and stabilization theorems are applicable to FO-LTI systems with different fractional orders in one or both of and intervals. Eventually, some numerical examples are presented to confirm the obtained analytical results.

eess.SY↗

arXiv2018

Robust Stabilization of Fractional-order Interval Systems via Dynamic Output Feedback: An LMI Approach

This paper addresses the problem of robust dynamic output stabilization of FO-LTI interval systems with the fractional order 0<α<2, in terms of linear matrix inequalities (LMIs). Our purpose is to design a robust dynamic output feedback controller that asymptotically stabilizes interval fractional-order linear time-invariant (FO-LTI) systems. Sufficient conditions are obtained for designing a stabilizing controller with a predetermined order, which can be chosen to be as low as possible. The LMI-based procedures of designing robust stabilizing controllers are preserved in spite of the complexity of assuming the most complete model of linear controller, with direct feedthrough parameter. Finally, some numerical examples with simulations are presented to demonstrate the effectiveness and correctness of the theoretical results. Keywords: Fractional-order system, interval uncertainty, linear matrix inequality (LMI), robust stabilization, dynamic output feedback.

eess.SY↗

arXiv2018

Robust Fixed-order Dynamic Output Feedback Controller Design for Fractional-order Systems

This paper deals with designing a robust fixed-order dynamic output feedback controller for uncertain fractional order linear time invariant (FO-LTI) systems by means of linear matrix inequalities (LMIs). Our purpose is to design a low order controller that stabilizes the fractional-order linear system in the presence of model uncertainties. No limitative constraint on the state space matrices of the uncertain system is assumed in the design procedure. Furthermore, adopting the most complete model of linear controller, with direct feedthrough parameter, does not disturb the LMI-based approach of developing robust stabilizing control. Eventually, the authors illustrate the advantages of the proposed method by some examples and their numerical simulation.

math.OC↗

arXiv2015

H_inf Consensus of nonlinear complex multi-agent systems using dynamic output feedback controller: An LMI approach

This paper investigates a new method for consensus in a group of nonlinear complex multi-agent systems using fixed-order non-fragile dynamic output feedback controller, via an LMI approach. The proposed scheme is decentralized in the sense that each agent relies on the relative output information among the adjacent agents. The consensus based controllers are designed to minimize the effects of nonlinear terms of the agents as well as external disturbances. Converting consensus problem to stabilization of an equivalent augmented system using proper transformations, Lyapunov stability theorem is applied to obtain unknown controller parameters in order to guarantee consensus and simultaneously acquire considered control objectives. Finally, to demonstrate the effectiveness of the proposed algorithm and compare with similar earlier researches, a numerical example on a multi-agent system consisting of single link flexible manipulators is carried out.

math.OC↗

arXiv2014

A New Delay Dependent Robust Fixed-Order Decentralized Output Feedback LFC Design for Interconnected Multi-Area Power Systems

This paper presents a novel load frequency control (LFC) design using integral-based decentralize fixed-order perturbed dynamic output tracking scheme in a delay dependent nonlinear interconnected multi-area power system via LMI approach. The tracking controller is designed such that the effects of the parameter variations of the plant and dynamic output controller as well as load disturbances are minimized. The inputs and outputs of each controller are local, and these independent controllers are designed such that the robust stability of the overall closed-loop system is guaranteed. Simulation results for both two- and three-area power systems are provided to verify the effectiveness of the proposed design scheme. The simulation results show that the decentralized controlled system behaves well even when there are large parameter perturbations and unpredictable disturbances on the power system.

math.OC↗