This paper addresses attitude tracking and vibration suppression problems during the flexible spacecraft maneuvers under the influence of system parametric uncertainties, external disturbances, and actuator nonlinear saturation without utilizing intelligent materials or smart vibration suppression actuators. Specifically, we develop a dual observer-based backstepping (DOB-BST) controller that employs a recursive control design to devise observers to estimate and attenuate the effect of perturbations in spacecraft attitude kinematics and dynamics. Moreover, the proposed DOB-BST controller uses an input compensator to mitigate the adverse impacts of saturation nonlinearity in a closed-loop system. The proposed control structure offers finite time convergence of closed-loop system states to a small neighborhood of zero. In addition, we give system state convergence regions and derive explicit tuning conditions to downsize the convergence region using Lyapunov stability analysis. Finally, the simulation experiment results confirm the performance of the proposed control algorithm despite the multiple system constraints.

This paper presents an active fault-tolerant control (FTC) framework for aerial vehicles operating under system uncertainties, external disturbances, and actuator faults or failures. Specifically, we propose a nonlinear integral sliding mode-based fault-tolerant control allocation scheme to address actuator faults and failures in an octocopter system. The goal is to perform trajectory tracking control and ensure system stability under practical operating conditions while preserving nominal closed-loop performance during fault scenarios. A baseline controller is first designed using a backstepping approach and combined with a nonlinear integral sliding mode control law to achieve nominal stability. To manage actuator degradation, a control allocation strategy is developed to redistribute control efforts among healthy redundant actuators based on real-time estimates of actuator effectiveness. Key features of the proposed FTC framework include its ability to handle faults and failures online while maintaining robustness against system perturbations. The simulation results demonstrate the effectiveness of the proposed BT-ISMC-based FTC method in sustaining performance under fault and failure conditions.

Web 3.0 is a grand design with intricate data interchange, implying the requirement of versatile network protocol to ensure its security. Attribute-based signature (ABS) allows a user, who is featured with a set of attributes, to sign messages under a predicate. The validity of the ABS signature demonstrates that this signature is generated by the user whose attributes satisfy the corresponding predicate, and thus flexibly achieves anonymous authentication. Similar to other digital signatures, the security of ABS is broken in case the private key of the user is leaked out. To address the threat brought by the key leakage, this paper proposes a puncturable attribute-based signature scheme that allows the private key generator to revoke the signing right associated with specific tags. This paper firstly elaborates the construction of the proposed ABS scheme with puncturable property, and then proves its security theoretically by reducing the involved security to the computational Diffie–Hellman assumption. This paper then experimentally shows that the suggested puncturable ABS scheme owns a more efficient storage cost and superior performance.

With the rapid development of technology, smart environments utilizing the Internet of Things, artificial intelligence, and big data are improving the quality of life and work efficiency through connected devices. However, these advances present significant security challenges. The data generated by these smart devices contains many private and sensitive information. In data transmission, crime and terrorism may intercept this sensitive information and use it for secret communications and illegal activities. Steganography hides information in media files and prevents information leakage and interception by criminal and terrorist networks in an intelligent environment. It is an important technology to protect data integrity and security. Traditional steganography techniques often cause detectable distortions, whereas Steganography Without Embedding (SWE) avoids direct modification of cover media, thereby minimizing detection risks. This paper introduces an innovative and robust technique called Robust Linked List (RLL)-SWE, which improves resistance to attacks compared to traditional methods. Using multiple median downsampling and gradient calculations, this method extracts stable features. It restructures them into a multi-head unidirectional linked list, ensuring accurate message retrieval and high resistance to adversarial attacks. Comprehensive analysis and simulation experiments confirm the technique’s exceptional effectiveness and steganographic capacity.

This work addresses the critical challenge of integrating drones into human-aerial robot interaction by presenting a novel Soft Flexible Aerial Robotics (SFAR) design. SFAR features an innovative low-pressure inflatable airbag structure that replaces traditional rigid frames, enhancing safety by mitigating collision risks with humans and payloads. To control this unconventional aerial platform, we present a control strategy based on a virtual link dynamics model that exploits the drone’s unique design. Our contributions include the pioneering design of an aerial robot specifically for Human-Aerial Robot Interaction (HARI), a novel control framework that balances flight performance with passive safety, and the validation of SFAR through real-world experiments, demonstrating its ability to perform at par with traditional rigid-body drones while offering enhanced safety features for seamless and safe integration into human environments.

This work proposes a reliable control scheme to attain the precise tracking control of multirotor unmanned aerial vehicle systems used for smart agriculture. The nonlinear mathematical model of a co-axial octorotor system equipped with a spraying mechanism is first established to contain the time-varying inertial coefficients and varying payload effects. Then an adaptive backstepping controller scheme is proposed to attain the desired attitude and position tracking. To ensure robustness against parameter uncertainty and external disturbances, a high-order integral sliding mode controller is integrated with the adaptive backstepping controller. Numerical simulations are carried out in variable payload conditions to demonstrate the effectiveness of the proposed approach.

This paper describes a new fault-tolerant control technique for over-actuated uncertain linear systems that compensates for actuator faults and failures using an output integral sliding mode-based control allocation strategy. An observer-based fault estimation unit is first proposed to estimate the system states and the actuator’s effectiveness level. Based on the estimated state’s information, a nominal virtual control law is created to achieve the desired specification of the perturbed system. A nonlinear output integral sliding manifold is incorporated with the nominal virtual control law that provides resilience to the closed-loop system against the uncertainty caused by the actuator’s faults and failure, states estimation error, and fault estimation error. Finally, depending on anticipated actuator efficacy from the fault estimation unit, the control allocation reroutes the virtual control input signals among the redundant actuators. A small-gain theorem is used to demonstrate the augmented closed-loop system stability. The observer and controller gains are synthesized using the linear matrix inequality technique. Finally, simulations on an aircraft system are performed to verify the efficacy of the suggested FTC technique. Compared with the existing work, the proposed approach is better able to handle actuator redundancy in faulty conditions and cater to the fault estimation error up to a certain level.Note to Practitioners—The aim of this paper is to address the reliability issues of industrial systems that contain sufficient input redundancy and are particularly designed to tolerate the faults and failures issues during the system operation. Existing fault-tolerant control schemes based on control allocations have limitations in terms of effective utilization of actuator redundancy, handling of fault estimation error, and applicability of reconfigurable control law. In this paper, we developed a fault-tolerant control strategy that is capable of addressing all the aforementioned concerns. The output integral sliding mode control-based control allocation scheme, proposed in this paper, is applicable to the class of over-actuated systems. The reconfiguration of fault-tolerant control law based on the estimated states and fault information is capable to cover a wider class of faults and failures while maintaining robustness against the system dynamics and uncertainty. The control reconfiguration is equally applicable to the class of systems that contains both rank-deficient and in-deficient input distribution matrices. The proposed scheme assumed the bounded external disturbance, therefore in future work, the adaptive law will be incorporated with sliding mode controller and results will be extended to a generalized class of affine nonlinear systems.