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1. Global sampled‐data stabilization via static output feedback for a class of nonlinear uncertain systems

   https://doi.org/10.1002/rnc.6542  

   Cao, Kecai; Qian, Chunjiang; Gu, Juping (March 2023, International Journal of Robust and Nonlinear Control)

   Summary This paper proposes some novel compensating strategies in output feedback controller design for a class of nonlinear uncertain system. With Euler approximation introduced for unmeasured state and coordinate transformation constructed for continuous system, sampled‐data stabilization under arbitrary sampling period is firstly realized for linear system using compensation between sampling period and scaling gain. Then global sampled‐data stabilization for a class of nonlinear system is studied using linear feedback domination of Lyapunov functions. Extension of obtained results to three‐dimensional system or systems under general assumptions are also presented. With the compensation schemes proposed in controller design, the sufficiently small sampling period or approximating step previously imposed is not required any more. The proposed controllers can be easily implemented using output measurements sampled at the current step and delayed output measurements sampled at the previous step without constructing state observers which has been illustrated by the numerical studies. 

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2. Asynchronous Quasi-Consensus of Heterogeneous Multiagent Systems With Nonuniform Input Delays

   https://doi.org/10.1109/TSMC.2018.2834823  

   Wang, Zhengxin; He, Haibo (October 2018, IEEE Transactions on Systems, Man, and Cybernetics: Systems)

   This paper analyzes the consensus problem in heterogenous nonlinear multiagent systems. The multiagent systems not only have nonidentical nonlinear dynamics for all agents, but also have different network topologies for position and velocity interactions. An asynchronous sampled-data control without any input delays is first proposed, the information of each agent is only sampled at its own sampling instants and need not be sampled at other sampling instants. Then, quasi-consensus in heterogenous multiagent systems is proved by Lyapunov stability theory. When asynchronous sampled-data control has nonuniform input delays, sufficient conditions for quasi-consensus in heterogenous multiagent systems are further obtained. The upper bound of quasi-consensus errors is estimated. Finally, numerical simulations are provided to verify the effectiveness of theoretical results. 

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3. Constrained Control of Input Delayed Systems With Partially Compensated Input Delays

   https://doi.org/10.1115/DSCC2020-3271  

   Abel, Imoleayo; Janković, Mrdjan; Krstić, Miroslav (October 2020, ASME 2020 Dynamic Systems and Control Conference)

   null (Ed.)

   Abstract Control Barrier Functions (CBFs) have become popular for enforcing — via barrier constraints — the safe operation of nonlinear systems within an admissible set. For systems with input delay(s) of the same length, constrained control has been achieved by combining a CBF for the delay free system with a state predictor that compensates the single input delay. Recently, this approach was extended to multi input systems with input delays of different lengths. One limitation of this extension is that barrier constraint adherence can only be guaranteed after the longest input delay has been compensated and all input channels become available for control. In this paper, we consider the problem of enforcing constraint adherence when only a subset of input delays have been compensated. In particular, we propose a new barrier constraint formulation that ensures that when possible, a subset of input channels with shorter delays will be utilized for keeping the system in the admissible set even before longer input delays have been compensated. We include a numerical example to demonstrate the effectiveness of the proposed approach. 

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4. Ensuring Both Positivity and Stability Using Sector-Bounded Nonlinearity for Systems With Neural Network Controllers

   https://doi.org/10.1109/LCSYS.2024.3416237  

   Montazeri_Hedesh, Hamidreza; Siami, Milad (January 2024, IEEE Control Systems Letters)

   This letter introduces a novel method for the stability analysis of positive feedback systems with a class of fully connected feedforward neural networks (FFNN) controllers. By establishing sector bounds for fully connected FFNNs without biases, we present a stability theorem that demonstrates the global exponential stability of linear systems under fully connected FFNN control. Utilizing principles from positive Lur’e systems and the positive Aizerman conjecture, our approach effectively addresses the challenge of ensuring stability in highly nonlinear systems. The crux of our method lies in maintaining sector bounds that preserve the positivity and Hurwitz property of the overall Lur’e system. We showcase the practical applicability of our methodology through its implementation in a linear system managed by a FFNN trained on output feedback controller data, highlighting its potential for enhancing stability in dynamic systems. 

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5. Discrete Finite-time Stable Position Tracking Control of Unmanned Vehicles

   https://doi.org/10.1109/CDC40024.2019.9029700  

   Hamrah, Reza; Sanyal, Amit K.; Prabhakaran Viswanathan, Sasi (December 2019, 2019 IEEE 58th Conference on Decision and Control (CDC))

   This paper presents a finite-time stable (FTS) position tracking control scheme in discrete time for an unmanned vehicle. The control scheme guarantees discrete-time stability of the feedback system in finite time. This scheme is developed in discrete time as it is more convenient for onboard computer implementation and guarantees stability irrespective of sampling period. Finite-time stability analysis of the discrete-time tracking control is carried out using discrete Lyapunov analysis. This tracking control scheme ensures stable convergence of position tracking errors to the desired trajectory in finite time. The advantages of finite-time stabilization in discrete time over finite-time stabilization of a sampled continuous tracking control system is addressed in this paper by a numerical comparison. This comparison is performed using numerical simulations on continuous and discrete FTS tracking control schemes applied to an unmanned vehicle model. 

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