This paper addresses the problem of guidance and control underwater vehicles. A multi-level strategy is used to determine (1) outer-loop path-following commands (2) inner-loop actuation commands. Specifically, a line-of-sight algorithm guide vehicle along three-dimensional path, an L1 adaptive low-level rudder accomplish path following. The performance bounds these outer- algorithms are present...

The L1 adaptive control scheme has proven its effectiveness and robustness in various fields thanks to its particular architecture where robustness and adaptation are decoupled. It was though noted that whenever the trajectory is varying, an inherent lag is present compared to other adaptive schemes due to the presence of a filter in the control architecture. To achieve a better tracking, we pr...

In this paper, we consider nonlinear affine-incontrol systems and present the L1 adaptive controller for the case when the performance specifications are defined via a nonlinear system of similar structure. The L1 adaptive controller ensures that the nonlinear, affine-in-control, uncertain system follows its ideal model during the transient and steadystate, if the adaptation gain is selected su...

L1 adaptive control architecture introduced in [1]– [4] ensures that the input and the output of an uncertain linear system track the input and output of a desired linear system during the transient phase, in addition to asymptotic tracking. In this paper, we extend the L1 adaptive controller to multi–input multi–output systems in the presence of unmatched time-varying disturbances. Simulation ...

First, this paper introduces a seven-term novel 3-D chaotic system and discusses its qualitative properties. The proposed system is a seven-term novel polynomial chaotic system with three quadratic nonlinearities. The Lyapunov exponents of the novel chaotic system are obtained as L1 = 3.3226, L2 = 0 and L3 = –30.3406. The maximal Lyapunov exponent (MLE) for the novel chaotic system is obtained ...

This paper addresses the important issue of robustness for design of feedback control systems. A well-known fact in robust control is that a high gain in the feedback loop leads to increased control effort and reduced phase margin. In an adaptive control framework, a high adaptive gain, implying fast adaptation, often leads to undesirable high-frequency oscillations in the control signal and se...

Group 2 innate lymphoid cells (ILC2s) are important effector cells driving the initiation of type 2 immune responses leading to adaptive T helper 2 (Th2) immunity. Here we show that ILC2s dynamically express the checkpoint inhibitor molecule PD-L1 during type 2 pulmonary responses. Surprisingly, PD-L1:PD-1 interaction between ILC2s and CD4+ T cells did not inhibit the T cell response, but PD-L1...