Suleiman Kurawa

Bio: Suleiman Kurawa is an academic researcher from University of Manchester. The author has contributed to research in topics: Matrix (mathematics) & Loop gain. The author has an hindex of 2, co-authored 2 publications receiving 6 citations.

Negative Imaginary Theory for a Class of Linear Time-Varying Systems

Abstract: This letter introduces the notion of linear time-varying (LTV) negative imaginary systems. LTV negative imaginary systems are defined using a time-domain dissipative supply rate $w$ ( $u,\dot {y}$ ) that depends on input to the system ( $u$ ), time-derivative of the system’s output ( $\dot {y}$ ) and an index $\delta \geq 0$ . For $\delta > 0$ , it gives rise to a strict subclass within the LTV negative imaginary systems, termed as LTV output strictly negative imaginary systems. For characterizing the proposed class of systems, a set of linear differential matrix inequality conditions is derived based on the given state-space realization. Subsequently, LTV negative imaginary theory is specialized to linear parameter-varying (LPV) cases for which, the differential matrix inequality conditions can easily be avoided by considering the rate of variation of the uncertain parameters as independent LMI variables. Finally, a set of sufficient conditions is derived which ensures that the origin is a globally asymptotically stable equilibrium point of an unforced positive feedback interconnection of two uniformly asymptotically stable LTV negative imaginary systems.

Dynamic Output Feedback Controller Synthesis using an LMI-based α- Strictly Negative Imaginary Framework

Abstract: This paper deals with the dynamic output feedback controller synthesis utilizing the α - strictly negative imaginary systems property. The proposed scheme ensures robust stability in closed-loop against the set of all stable, strictly proper negative imaginary uncertainties that satisfies the DC loop gain condition pertaining to negative imaginary stability. In addition to that, a prescribed decay rate in the closed-loop time response is also enforced via α - pole placement. Two illustrative examples have been studied to demonstrate the usefulness of the proposed controller synthesis scheme.

Negative Imaginary Stability Result Allowing Purely Imaginary Poles in Both the Interconnected Systems

Abstract: This letter extends the class of systems to which negative imaginary (NI) stability result can be (directly) applied. The existing closed-loop stability results for NI interconnections require at least one of the systems to satisfy strictly negative imaginary (SNI) properties and hence do not allow purely imaginary poles in both the systems. In contrast to this, a set of necessary and sufficient conditions is derived in this brief for the internal stability of two NI systems in a positive feedback loop with possible poles on the imaginary axis excluding the origin. This proposed result also captures all the existing closed-loop stability results of NI systems, without poles at the origin, as special cases. Illustrative numerical examples are studied to show the usefulness of this development.

A two‐loop group formation tracking control scheme for networked tri‐rotor UAVs using an ARE‐based approach

Abstract: Cooperative control of networked unmanned aerial vehicles (UAVs) has received significant research interest over the last decade due to its potential applications in military security and surveillance, search and rescue, planetary exploration, precision agriculture, and so on. Many of these practical activities can be formulated as a group formation tracking problem with multiple targets to track. This paper aims to address such problems via designing a cooperative control scheme for networked tri‐rotor UAVs connected with directed graph topology. The proposed methodology consists of a two‐loop control scheme—the inner loop applies a robust feedback linearization technique to linearize the coupled, nonlinear dynamics of the tri‐rotor UAVs; while the outer loop facilitates an ARE‐based cooperative group formation tracking scheme. Tri‐rotor UAVs are considered in this paper instead of quad‐rotor UAVs, which are more common in drone applications, to conquer a major limitation of the quad‐rotor UAVs that it cannot alter its attitude independently while hovering at a particular height. A rigorous theoretical proof is given to establish the two‐loop control scheme exploiting the Lyapunov stability approach and algebraic Riccati equation (ARE)‐based optimal control policy. An in‐depth case study on a multitarget surveillance mission has been performed in this paper using a virtual reality software simulation platform to demonstrate the usefulness and efficacy of the proposed scheme.