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The liquid cooling system (LCS) of the proton exchange membrane (PEM) fuel cell suffers from large time delay, coupling, uncertainties, and various disturbances, making it susceptible to temperature regulation overshoot and control oscillation. This article focuses on a composite control scheme for the LCS that has effectively addressed the aforementioned issues. We first propose a two-layer control approach for the pump to minimize coupling, and an average delay model (ADM) for radiator whose parameter uncertainties are removed by equilibrium optimizer (EO). To overcome disturbances, an adaptive sliding mode control (ASMC) based on extended state observer (ESO) is presented, and its finite-time convergence is demonstrated. Additionally, the indirect regulation for the stack temperature is designed to considerably reduce the time delay in the fan control loop. Co-simulation results indicate that the proposed ASMC significantly suppresses the chattering phenomenon compared with regular sliding mode control (SMC). In contrast to incremental fuzzy control, the proposed scheme possesses superiorities in response speed, tracking accuracy, anti-disturbance, as well as suppression of overshoot and oscillation. • A two-layer control approach is developed for the coolant pump. • An average delay model is presented for the radiator. • An adaptive sliding mode control is proposed for the cooling fan. • An indirect regulation method significantly reduces the time delay in the fan control loop. [ABSTRACT FROM AUTHOR]

This communique proposes a novel second-order sliding mode (SOSM) control method to handle sliding mode dynamics with mismatched term, so as to reduce the terms in the control channel. Meanwhile, it is shown that the proposed control approach can be used to design SOSM controllers under disturbances bounded by positive functions rather than conventional constant upper bounds. The finite-time stability of the sliding variables has been shown by using finite-time Lyapunov theory. The validity of the proposed approach is verified by controlling a Buck converter. [ABSTRACT FROM AUTHOR]

High-order sliding mode (HOSM) control is known to provide for finite-time-exact output regulation of uncertain systems with known relative degrees. Yet the corresponding universal HOSM controllers are typically constructed by special recursive procedures and have complicated form. We propose two new families of homogeneous HOSM controllers of a very simple form. Lyapunov functions are provided for a significant part of the first-family controllers. The second family consists of quasi-continuous controllers, which can be done arbitrarily smooth everywhere outside of the HOSM manifold. A regularization procedure ensures high-accuracy output regulation by means of control with required smoothness level. Output-feedback controllers are constructed. Controllers of the orders 3–5 are demonstrated. [ABSTRACT FROM AUTHOR]

The output constraints widely exist in the physical systems and severely affect the performance of the closed-loop system. This paper considers the second-order sliding mode controller design subject to an output constraint. By constructing a new barrier Lyapunov function and applying the technique of adding a power integrator, a novel second-order sliding mode control algorithm, which can be used to deal with the output constraint problem, has been developed. The proposed sliding mode algorithm enables the output variable not to violate the boundary of the constraint region. Meanwhile, it has been shown that under the output constraint the sliding variable can still be stabilized to zero in a finite time. Finally, an academic example is given to verify the feasibility of the proposed second-order sliding mode algorithm. [ABSTRACT FROM AUTHOR]

Efficient path tracking control for autonomous agricultural vehicles (AAVs) is the key technology for realizing agriculture 4.0 and precision agriculture, which makes smart farms more sustainable, profitable, and eco-friendly. It is well recognized that model nonlinearity, unknown disturbances, and wheel slipping are common problems in practical AAV systems in operation. To tackle these issues and improve the path tracking performance, a novel fixed-time generalized super-twisting control scheme is proposed for AAVs in this paper. First, a fixed-time integral sliding mode surface is designed for the considered vehicle by fusing the lateral offset and heading offset together. Then, an innovative auxiliary system dynamics is constructed to collaborate with the foregoing sliding mode surface, compensating for the adverse effects of wheel slipping effectively. Subsequently, based on the kinematic offset model of AAVs, a new type of generalized super-twisting controller is designed to achieve superior path tracking with robustness. Unlike existing super-twisting controllers, the generalized super-twisting continuous controller can fully eliminate chattering by replacing the previous discontinuous terms with a nonsmooth term. Further, rigorous theoretical analysis is conducted by raising a fresh Lyapunov function to verify the closed-loop control system stability. Finally, extensive field experiments have been carried out to show that the proposed control scheme significantly outperforms typical comparative control schemes. • A new generalized super-twisting controller is proposed for vehicle path tracking. • A fixed-time sliding mode surface is designed to overcome the singularity problem. • To handle the issue of wheel slipping, an auxiliary dynamic system is constructed. • Field experiments are conducted to demonstrate the path tracking performances. [ABSTRACT FROM AUTHOR]

The mean-square exponential stabilization problem of stochastic Markovian jump system subject to time-varying delays and uncertainties has been investigated by using integral sliding mode control technique. Firstly, in order that the system trajectories can be kept on the integral sliding surface almost surely since the initial time, an integral sliding surface is constructed by properly choosing some matrices. On this basis, a novel sliding mode controller is designed to guarantee that the states will be kept on the sliding surface. Then, the sufficient condition in terms of linear matrix inequalities is presented to ensure that the mean-square exponential stability of the states can be guaranteed. Finally, a numerical example is provided to illustrate the effectiveness of the proposed design method. [ABSTRACT FROM AUTHOR]