The primary objective of this paper is to address the visual servo tracking control problem for robot manipulator. Based on the visual servo control system structure, the system is artificially divided into two parts: the outer-loop (visual feedback control loop) and the inner-loop (robot tracking control loop). First, for the outer loop system, a visual servo pixel kinematics model is established based on the perspective projection equation, and a virtual linear velocity controller for the camera is designed. Second, based on the robot’s Jacobian matrix, the virtual linear velocity of the outer-loop is transformed into the robot joint angular velocity signal (the desired signal for the inner-loop). Then, combining the robot’s dynamic characteristics, a finite-time trajectory tracking controller is designed to ensure that the robot can track the desired joint angular velocity signal in a finite time. Additionally, considering the presence of external disturbances in the robot system, a koopman operator-based disturbance observer is designed to enhance the robustness of the inner loop control system. Finally, numerical simulations and experimental results validate the feasibility of the proposed theoretical algorithms.

With the rapid deployment of unmanned bolt-tightening robots on transmission towers, traditional control algorithms face challenges in balancing long-term task logic and real-time adaptability, especially under unstructured environments such as missing bolts and unexpected obstacles. This paper proposes HTP-TV, a framework for hierarchical task planning with temporal logic and visual servoing, which integrates temporal logic-based planning with a vision-based reactive mechanism. HTP-TV decouples semantic goals such as bolt-tightening sequences from geometric path planning, enabling offline pre-planning via LTL-RRT* to generate constraint-compliant trajectories. In the online phase, real-time camera data dynamically updates the environmental model, which triggers adjustments in the incremental Büchi automaton to address missing bolts or obstacles. A semantic ID system encodes the bolt topology, supporting re-planning with axial constraints, while visual servoing techniques correct execution deviations. Through comparisons with the two methods (Offline LTL-RRT* and Online RRT*-based), the simulation results in CoppeliaSim demonstrate the efficiency, high safety compliance, and superiority of HTP-TV.

This paper investigates the stochastic stability of the continuous-discrete maximum correntropy cubature Kalman filter (CD-MCCKF), which is developed by embedding the maximum correntropy criterion as an optimization strategy into the continuous-discrete filtering architecture. By assuming that the relevant functions satisfy certain properties, we first establish the convergence of the employed numerical method and fixed-point iteration technique. Subsequently, combined with the findings on the error covariance boundary, it is proved that the estimation error of CD-MCCKF keeps mean-square bounded under specific conditions. To validate this stability analysis finding and evaluate the filtering performance, we conduct a classical case study. Simulation results confirm that CD-MCCKF not only maintains bounded estimation errors, but also surpasses the conventional continuous-discrete filters in terms of accuracy and convergence.

The increasingly mature visual feedback technology has greatly promoted the development of high-altitude unmanned operations, particularly in bolt-tightening operations for the power transmission tower. Nevertheless, traditional control algorithms relying on visual feedback encounter specific difficulties and challenges during bolt-tightening tasks execution. This paper presents a disturbance observer-based finite-time control algorithm to reject disturbances during bolt-tightening operations and mechanical errors inherent to the robotic system. Through theoretical analysis of this algorithm, based on visual feedback technology and the finite-time control method, the finite-time stability of the overall closed-loop system is ensured. Both the simulation and experimental results are given to validate the feasibility of the proposed control method. Compared with traditional PID, LQR, and MPC controllers, the convergence speed is increased by more than 16%, and the accuracy of steady-state error is also increased by more than 22%, moreover, the success rate is as high as 98%. It is highlighted that the proposed control method has superior disturbance rejection capability, faster convergence speed, and better reliability. Note to Practitioners—This study addresses challenges in visual feedback-dependent bolt-tightening operations for power transmission towers. A novel disturbance observer-based finite-time control algorithm is introduced, ensuring the stability of the closed-loop system. The method excels in rejecting disturbances and minimizing mechanical errors during bolt-tightening tasks. The simulation and experimental results confirm its superiority over conventional controllers in terms of disturbance rejection, convergence rate, and operational precision. Practitioners should consider the algorithm’s potential to enhance the efficiency and reliability of bolt-tightening in high-altitude unmanned operations.

Tackling the challenge of open-switch (OS) fault diagnostics in grid-tied three-level neutral point clamped (NPC) inverters with parameter uncertainty, this paper introduces a fault diagnosis method that integrates a variable forgetting factor bias-compensation recursive least squares (VFFBCRLS) algorithm with a novel discrete disturbance sliding mode observer (DSMO) for three-level inverters. The proposed approach initially employs a VFFBCRlS algorithm to obtain the uncertain parameters of the inverter. Building upon this foundation, a novel discrete DSMO is introduced to obtain the output currents rapidly and accurately. Then, an adaptive fault detection variable is constructed based on the norm of the residual between the measured and the estimated currents, ensuring the accuracy and robustness of the detection algorithm. Finally, a precise identification of OS faults in grid-tied inverters is achieved through the establishment of a localization mechanism. The hardware-in-the-loop (HIL) test results provide validation for the efficacy and robustness of the proposed method.

Force control strategies are crucial for robot manipulators to effectively adapt to diverse tasks. However, employing force sensors to measure force/torque information significantly increases the cost of robotic systems. Hence, it is crucial to delve into sensorless force/torque estimation techniques. Given the low precision of traditional force estimation algorithms, this article presents a novel algorithm to improve the torque estimation precision of robot manipulators' joints. First, based on the dynamic model, a finite-time sliding-mode torque observer is designed for the robot manipulators via a step-by-step method. A new Lyapunov function is constructed to prove the finite-time convergence of the closed-loop system. Second, in the presence of sampling noise, the robustness of the proposed finite-time torque observer is analyzed. Finally, simulation and experimental results validate the effectiveness of the proposed algorithm.

The stability of second-order non-smooth control system under denial-of-service (DoS) attack is studied in this paper. Non-smooth control method can be used to stabilize the system states to the equilibrium point in a finite time if there is no DoS attack. However, under DoS attack, the controller will maintain the latest received data, which may lead to local divergence of the system states. By designing a Lyapunov function, it is proven that under energy-constrained DoS attack, the states of closed-loop system can still converge to the equilibrium point in a finite time. The simulation results further validate the effectiveness of the theory.

Accurate fault detection and localization are essential for single-phase three-level (SPTL) rectifier systems with high reliability requirements. However, power switch faults, grid-side current sensor (CS) faults, and DC-link voltage sensor (VS) faults can all contribute to distorted output in the rectifier system, posing challenges for existing diagnostic methods tailored for single-type faults, as they struggle to distinguish between these various faults. Therefore, this study proposes a comprehensive diagnosis technology for open-circuit (OC) faults, CS faults, and VS faults of SPTL rectifiers on the basis of a reduced-order observer. To achieve this, the method begins by expanding and transforming the state equation of the rectifier with faults, ensuring complete decoupling of the OC fault vector from the initial system states and sensor faults. Subsequently, an assessment of the initial system state, CS faults, and VS faults is achieved via the design of a reduced-order observer. Using these estimation results, fault detection variable and its adaptive thresholds is designed, along with fault-distinguishing variables to differentiate between sensor faults and OC faults. Simultaneously, sensor fault identification method and OC fault location method are introduced. Finally, the validity and resilience of the comprehensive diagnostic approach are confirmed through hardware-in-the-loop (HIL) test results under diverse scenarios.

The consensus problem for second-order multiagent systems based on nonsmooth sampled-data control is considered. First, a continuous-time nonsmooth consensus protocol is proposed, which can realize the consensus of systems in a finite time when the external disturbance is absent. Next, based on the sampled data and the zero-order holder, a new discrete-time nonsmooth protocol is proposed. Considering external disturbances, the explicit relationship between the ultimate boundary of errors of any two agents and the sampling period and external disturbance is given with the Lyapunov method and graph theory, which theoretically shows that the nonsmooth control algorithm has a stronger ability to resist external disturbance than the smooth control algorithm. Finally, a simulation example shows the superiority of the nonsmooth consensus algorithm over a smooth consensus algorithm.

In this article, we studied the parameters identification problem for the single sinusoidal signal based on the finite-time observer technique. After representing the sinusoidal signal with known frequency as a second-order time-invariant system, a finite-time observer-based estimation strategy is designed based on the homogeneous system theory to obtain unknown amplitude and phase angle. When the signal frequency is unknown, the original signal will be constructed into a third-order nonlinear system, which is challenging to design the corresponding state estimator. Based on the Lyapunov analysis method and adding a power integrator technique, a finite-time estimation scheme is developed and analyzed strictly. Finally, for a single-phase grid signal, some experimental results are provided to illustrate the efficacy of the proposed method.

This article investigates the problem of global output feedback stabilization by using aperiodic-sampled-data control, i.e., event-triggered control, for a class of uncertain nonlinear systems under certain assumptions. By employing the technique of output feedback domination, an observer-based event-triggered output feedback control law is explicitly constructed to guarantee the globally asymptotic stabilization. To avoid the Zeno behavior, a combining mechanism with event-triggered and time-triggered is proposed to ensure that the two consecutive updated time for the sampled-data controller is larger than one positive constant. Finally, it is shown that the problem of global output feedback stabilization for a class of uncertain nonlinear systems is solved via the proposed event-triggered control law. Finally, some comparative simulation examples are given to show the efficiency of the introduced method.

This article is concerned with the problem of global finite-time output stabilization for a class of second-order nonlinear systems with both uncertain nonlinear dynamics and unknown external disturbance. Specifically, at the first step, without considering the external disturbance, a global finite-time state feedback controller is proposed to dominate uncertain nonlinear dynamics of the second-order system. To address the more challenging case where only the system output is available, a novel design idea of the nonseparation principle is employed. By treating the unknown external disturbance as a generalized state, a finite-time convergent extended state observer is constructed to estimate the unmeasured state and the unknown external disturbance. Based on this observer, an output-based composite controller with finite-time convergence is developed. The global uniform finite-time stability of the overall closed-loop system is proven based on the Lyapunov method. Simulation results of the inverted pendulum system demonstrate the superiority of the proposed control method in terms of both convergence performance and disturbance rejection performance.

This paper mainly studies the control problem of permanent magnet synchronous motor (PMSM) speed control system. Firstly, by analyzing the error dynamics equation of PMSM, an appropriate integral fixed-time sliding mode surface is selected. Then, an integral fixed-time sliding mode control algorithm is designed through the selected integral sliding mode surface. Finally, comparison results of numerical simulations are provided to verify the effectiveness of the proposed control method.

This paper mainly investigates the attitude control problem for a spacecraft. Not only angular velocity constraint but also external disturbances are considered in the system model. Under the action of proposed controller, the posture can be converged to the desired value, and the angular velocity can be asymptotically converged to the origin.

The main objective of this article is to explore the issue of how to improve the performance of discrete-time sliding mode control (DSMC) law for a class of discrete-time dynamic systems with both matched and mismatched disturbances. By using tools from mismatched disturbance compensation technique, a new kind of discrete-time sliding surface is constructed and subsequently utilized in designing the desirable DSMC laws. Specifically, two different types of DSMC laws, i.e., the equivalent-control-based DSMC law and the reaching-law-based DSMC law, are respectively constructed based upon the developed sliding surface. Rigorous analysis on stability of the corresponding closed-loop system is performed where it is shown that the mismatched disturbances could be successfully attenuated from the output channel in steady state. The effectiveness of the analytic result is supported by the experimental studies as well as numerical simulations.

The problem of distributed formation control for multiple quadrotor aircraft in the form of leader-follower structure is considered in this paper. Based on a nonsmooth backstepping design, a novel consensus formation control algorithm is proposed and utilized. First, for the position control subsystem, based on the linear quadratic regulator optimal design method, a formation control law for multiple quadrotor aircraft is designed such that the positions of all the quadrotor aircraft converge to the desired formation pattern. The designed formation control law for position systems will generate the desired attitude for the attitude control systems. Second, for the attitude control subsystem described by unit quaternion, by employing the technique of finite-time control and switch control, a global bounded finite-time attitude tracking controller is designed such that the desired attitude can be tracked by the multiple quadrotor aircraft in finite time. Finally, numerical example is performed to demonstrate that all quadrotor aircraft converge to the desired formation pattern in the 3-D-space.

The problem of current sharing controller for parallel dc-dc buck converter system is investigated in this paper. Specifically, to achieve the goal of sharing control and improve the systems dynamic performance, a new finite-time current sharing control algorithm is designed and employed. Under the proposed control algorithm, rigorous proofs show that not only the output voltage of the converter system can reach the desired reference voltage in a finite time, but also the objective of current sharing can be achieved within almost the same time. In addition, when the external load is time-varying and unknown, a finite-time load estimator is given to handle the load variation, and an adaptive finite-time current sharing control algorithm is subsequently developed. Experimental results are presented to verify the effectiveness of the proposed method, and to show its advantages over some traditional control algorithms. It is shown that a faster convergence rate and a better load disturbance rejection performance can be yielded by the present algorithm. Finally, it is shown that the main results can be extended to the case of n parallel dc-dc buck converters.

This paper mainly investigates the attitude control problem for a aircraft with quadrotor model. By combining with the physical feature of quadrotor, the attitude trajectory is first planned and divided into different priorities. Then, based on the technique of finite-time control, the finite-time attitude tracking controller is designed such that the attitude decoupled control can be achieved in a finite time. A simulation example is given to demonstrate the efficiency of the proposed method.

The distributed synchronization control problem of multiple quadrotor aircraft in the form of leader-follower structure is considered in this paper. Based on the method of backstepping design, a novel distributed consensus control algorithm is proposed. Firstly, for the position control subsystem, by Proportional-Differential control and the theory of communication topology graph, a consensus control law for multiple quadrotor aircraft is designed such that all the quadrotor aircraft can convergence to a leader and move along the desired trajectory asymptotically. The designed distributed consensus control law for position systems will generate the desired attitude for the attitude control subsystems. Secondly, for the attitude control subsystem described by unit quaternion, by employing switch control, a global attitude tracking control law is designed such that the desired attitude can be tracked. Finally, a example is given to demonstrate the efficiency of proposed method.

Based on the production system of high functional plastic production areas, the authors design an information acquisition system based on OLE for Process Control (OPC) technology. The system achieves the bottom information and uploads to the management layer. It uses a combination of Ethernet and serial communication to connect field equipment. Through hardware manufacturer provides the OPC Server interface to save real time information of the production equipment in real-time database of the industrial configuration software. On the basis of this, the upper application system is flexible to access the field devices through OPC Client, gathering and managing real-time information. The production practice shows that the system is not only safe and reliable communication, rapid data collection and processing, but also constantly update and extend the functionality in the future, to satisfy the business enterprises to the higher requirements of the production.

The consensus problem of multiple nonholonomic mobile robots in the form of high-order chained structure is considered in this paper. Based on the model features and the finite-time control technique, a finite-time cooperative controller is explicitly constructed which guarantees that the states consensus is achieved in a finite time. As an application of the proposed results, finite-time formation control of multiple wheeled mobile robots is studied and a finite-time formation control algorithm is proposed. To show effectiveness of the proposed approach, a simulation example is given.

By employing the finite-time control method, the consensus control algorithm for higher-order multiagent systems is designed in this paper. Under a neighbor-based rule, a higher-order finite-time consensus algorithm is explicitly constructed, which only uses local information. The finite-time consensus control algorithm can guarantee that the state consensus is achieved in a finite time. In addition, for multiagent systems having a leader-following structure, the consensus algorithm is also designed. Finally, two examples are presented to show the effectiveness.

The fixed-time synchronization problem fsor a class of second-order nonlinear multi-agent systems with a leader-follower architecture is investigated in this paper. To achieve the fixed-time tracking, the design procedure is divided into two steps. At the first step, a distributed fixed-time estimator is designed for each agent to estimate the leader's state in a fixed time. Then, at the second step, based on the technique of adding a power integrator, a fixed-time tracking controller for each agent is proposed such that the estimate leader's state can be tracked in a fixed time. Finally, an estimator-based fixed-time controller is developed such that the leader can be tracked by all the followers in a fixed time. Simulations are presented to verify the effectiveness of the proposed approach.