The fractional-order (FO) nonlinear differential system with state-dependent (SD) delayed impulses (DI) is considered in this brief. The considered impulses are related to the delayed state of the system and the delays are SD. A novel lemma for the monotonicity of the solution of Caputo's FO derivative equation is given. By means of linear matrix inequality (LMI) and several comparative arguments, criteria of uniform stability, uniform asymptotical stability, and Mittag-Leffler stability are obtained. Compared with other works on integer-order (IO) impulsive delayed systems with SD delays or fixed delays, how to impose constraints on parameters and impulses is explored, without imposing the boundedness on the state delays. Two examples are implemented to examine the practicality and sharpness of our theoretical analysis.

This article presents an adaptive integral backstepping sliding mode controller (AIBSC) for a class of microgravity electromagnetic vibration isolation systems (MEVIS) that exhibit nonlinearity and uncertainty. To address the errors caused by the backstepping strategy, a finite-time command filter is applied. Additionally, to overcome acceleration disturbances, a fixed-time observer is used for estimation. Lyapunov theory is employed to prove the global asymptotic stability of the proposed controllers. Finally, simulations demonstrate that this controller ensures system stability while improving the isolation performance.

A fixed-time sliding mode controller is developed for the three-degree-of-freedom air-floating robot (AFR) in the presence of model uncertainties and external disturbances. By dynamics transformation, the complex nonlinear AFR dynamics are transformed into a second-order feedback decoupling model. A neural network enhanced by actor–critic learning structure is designed to handle model uncertainties, and the nonsingular fast terminal sliding mode controller can ensure all signals in the closed-loop system converge to a residual set around the origin within a fixed time. The system stability is proved by Lyapunov theory and the simulation results show the effectiveness of the proposed scheme.

In this article, the finite-time observer-based sliding-mode control (SMC) problem is considered for stochastic Markovian jump systems (MJSs) with a deterministic switching chain (DSC) subject to time-varying delay and packet losses (PLs). First, the stochastic MJSs with DSC are appropriately modeled and the PLs case is characterized by using some Bernoulli random variables. Then, a nonfragile finite-time bounded sliding-mode observer is designed. Our objective is to propose a finite-time observer-based SMC approach such that for the above addressed system, the finite-time boundedness in a certain time interval can be guaranteed by giving sufficient criteria via the stochastic analysis skills and average dwell time (ADT) method. Moreover, a new robust finite-time sliding-mode controller can be designed to ensure reachability of the common sliding surface in the estimation space. Finally, a numerical example is provided to illustrate our theoretical results.

Aiming at the problem of residual moment generated by the motion of spacecraft active loads, an improved method for measuring and calibrating it is proposed, and an on-ground residual moment measurement and calibration system based on the combination of three-dimensional force sensors and a three-axis air bearing testbed is presented for this method. The composition and working principle of the system is studied, the fixed relationship between the three-dimensional force sensors and the three-axis air bearing testbed is given, and the algorithm for measuring the residual moment of active loads is proposed. According to the algorithm, the effects of the installation error, measurement error, and measurement disturbance of the three-dimensional force sensors on the residual moment measurement accuracy are given, and the mapping relationship from different ranges and different installation errors to measurement errors of three-dimensional force sensors is studied. Theoretical and simulation analysis shows that the measurement errors of the residual moment are 0.059%, 0.064%, and 0.054%. The method is less affected by environmental interference and restrictions, with high measurement accuracy and excellent applicability.

This paper proposes a spacecraft dynamics full-physical simulator based on air bearing technology, which can effectively simulate the micro-damping dynamic environment of spacecraft in outer space. This paper gives the kinematics model and dynamic equations of the simulator, and analyzes the similarity of the attitude dynamics between the simulator and the real spacecraft. Referring to the real on-orbit spacecraft, the simulator selects the reaction flywheel and the gas injection system as the actuators, designs a control switching algorithm, and uses data fusion technology to switch the mode of the attitude measurement system. Finally, an attitude control simulation test is carried out. The test results verify the correctness and feasibility of the simulator. Using the full- physical simulator proposed in this paper, we not only can carry out spacecraft dynamics experiments on the ground, but also can verify various algorithms, which has important engineering application value.

This paper investigates the problems of stability and periodicity for the discrete sliding mode (SM) controlled DC-DC buck converters subject to parasitic parameters. The loss resistance of power switch, conduction voltage and conduction resistance of diode, equivalent series resistance of inductor are first considered and modeled for buck converters. After the discretization of SM controlled buck converter system, the stability condition is deduced, proving that there exist a attractive region in phase plane which affected by the sampling time. The sufficient and necessary condition of periodicity is given and the influence of parasitic parameters on dynamic trajectory is analyzed and further it is proved not affect the system periodicity under some restricted conditions. Simulations validate the proposed research.

This work presents a low-frequency artificial magnetic signal positioning method based on aiming at the fact that GNSS signals are susceptible to the influences of weather and location which may even lead to being unable to realize or proceed localization services. The localization method, first proposed by Sheinker. et al. [1], is used for many real-time, low power applications such as indoor robot navigation. On top of that, a low-frequency artificial magnetic signal localization method based on cuckoo search algorithm is proposed. The effectiveness of the localization method is verified by simulation and experiments. Results show that the scheme has the characteristics of strong adaptability and high precision within the range of stable low-frequency magnetic signal.

For a non-singular terminal sliding mode (NTSM) controlled two-link flexible manipulator, this paper investigates the phase trajectories starting from different original states and gives the existence of a critical surface determining whether the system convergences to the equilibrium point in a short path. By using the output redefinition method, the system is first decomposed into a zero dynamic subsystem and an input-output subsystem-the stability of the former is guaranteed by pole placement technique, while a NTSM controller is designed for the latter to realize its finite time convergence and better control performance. Then twelve possible original states and their corresponding phase trajectories are discussed, proving the distribution rule of phase trajectory. Simulations validates the proposed analysis.

This paper focuses on the transient analysis for a two-link flexible manipulator under the control of non-singular terminal sliding mode (NTSM), and proposes a convergence time estimation method with difficulties of non-minimum phase and the uncontrolled reaching motion. To overcome the first problem, the system is decomposed into a zero dynamic subsystem and an input-output subsystem-the stability of the former is guaranteed by pole placement, while a NTSM controller is designed for the latter to realize its finite time convergence and better control performance. The relationship between the initial point and the sliding mode reaching time is explored, and further the convergence time is estimated to overcome the second problem. Simulations validate the proposed method.

This paper investigates the fuzzy H∞filter design issue for nonlinear systems with time-varying delay. In order to obtain less conservative fuzzy H∞filter design method, a novel integral inequality is employed to replace the conventional Lebniz-Newton formula to analyze the stability conditions of the filtering error system. Besides, the information of the membership functions is introduced in the criterion to further relax the derived results. The proposed delay dependent filter design method is presented as LMI-based conditions, and corresponding definite expressions of fuzzy H∞filter are given as well. Finally, a simulation example is provided to prove the effectiveness and superiority of the designed fuzzy H∞filter.

In this paper, a terminal sliding mode (TSM) controller is designed for boost converter with purpose of robustness and better response against circuit nonlinearities and disturbances. Instead of using the commonly used average model or switching model for current-mode controlled (CMC) boost converter, a novel energy storage function (ESF) model is proposed for TSM controller, which contains all of the nonlinear elements of inductor current and capacitor voltage and further converges the both to the zero, unlike the CMC control ignoring the transient control of capacitor voltage. By adopting TSM instead of the traditional linear sliding mode (LSM), the system can track the given output voltage with faster response due to its finite time convergence. Meanwhile, an exponential reaching law is designed for TSM controller to eliminate the unexpected chattering phenomenon. Simulation results with comparison of the traditional CMC LSM control can prove the better control performance of the proposed scheme.

This work focuses on stability analysis and stabilization synthesis problem for a class of Takagi-Sugeno (T-S) polynominal fuzzy-model-based time-delay systems based on the sum-of-squares (SOS) approach. Firstly, a novel stability criterion is proposed based on Lyapunov stability theorey, which is less conservative as the information of the membership functions is included in the stability conditions. Then, a new fuzzy controller with greater design flexibility to stabilize the colsed-loop system is developed. Finally, a simulation example is provided to illustrate the effectiveness of the proposed design methods.

The stability analysis and control design problem of Takagi-Sugeno (T-S) fuzzy time-delay systems under mismached premise membership functions are investigated in this paper. A membership function dependent stability criterion is derived first based on Lyapunov stability analysis method. As the information of the membership functions is included in the derived criterion, it is less conservtive than those of independent ones. Then, a fuzzy controller is derived to stabilize the corresponding closed-loop system. All the conditions in this paper are described in linear matrix inequalities (LMIs) frame that can be handled numerically. Finally, some numerical examples are presented to indicate the effectiveness of our approach.

This paper presents a novel terminal sliding mode (TSM) control scheme with double closed-loop structure of capacitor voltage and inductance current for the stability control of DC-DC buck converter. In order to satisfy the different performance demands of capacitor voltage and inductance current, a TSM controller and a linear sliding mode (LSM) controller is designed separately. For the former, TSM controller can track the given output voltage with fast response speed due to its finite time convergence and then output the reference inductance current; while for the latter, it can track the reference inductance current and then control the `on/off' of the power switch. The stability condition in the case of power switch `on' and `off' can also be deduced. Simulation results with comparison of those of traditional single-loop LSM controller can validate the proposed scheme.

The standard application of nonsingular terminal sliding mode (NTSM) control is strictly limited to n-order (n≥2) systems and suffers from chattering problem. This paper proposes a continuous NTSM control for extended first order systems to obtain the global finite-time convergence and free-chattering simultaneously. Firstly, utilizing the concept of relative degree, a power-fractional NTSM manifold is designed. Then, based on Lyapunov stability theorem, a switching control law is designed to act on the derivative of NTSM variable, so that the real control is smoothed by integral action. Meanwhile, since the integral term is incompatible with input saturation in real systems, anti-windup compensation should be made accordingly. Taking permanent magnet synchronous motor as an example, simulation results are presented to validate the proposed method.

This paper investigates the robust control of two-link flexible manipulator systems subject to parameter perturbations, and a hybrid control scheme consisting of a continuous nonsingular terminal sliding mode (NTSM) controller and an observer-based LQR controller is proposed. In order to solve the non-minimum phase problem of flexible manipulator, singular perturbation method is utilized to decompose the system into a slow and fast subsystem in two-time scale, and joint angles and corrected flexible modes are modeled as the slow and fast variables, respectively. For the slow subsystem, a novel continuous NTSM control based on the concept of relative degree is proposed for robustness, finite-time convergence and free-chattering. For the fast subsystem, a reduced-order observer is designed to estimate corrected flexible modes and then a LQR controller is proposed for its optimal stability. Simulation results are presented to validate the control scheme.