In the process of accurately tracking the welding path with the end effector of an industrial robot arm, challenges such as joint friction (disturbance) and communication time delay arise. To address these issues, this study investigates the performance output tracking problem for a one-dimensional unstable heat equation, with unknown external disturbances and input end time delay. Based on the properties of the first-order transport equation, the control system can be modeled as a cascaded system consisting of a heat equation and a transport equation, where the transport equation represents the actuator dynamics. The system features a non-collocated structure, where the difficulties arising from this structure are resolved by constructing an appropriate auxiliary system. The control problem of the cascaded system is solved via the actuator dynamics compensation method. An error-based observer is constructed to simultaneously estimate external disturbances and system states, and a full-state feedback law is successfully designed to achieve the performance output tracking of the system. It is proven that the designed observer is well-posed and the closed-loop system achieves exponential stability.

For a new type of multi-segment pontoon bridge with alternately supported floats in the span range, a theoretical model of the dynamic response is established which can simultaneously consider the roles of connection hinge stiffness and float support stiffness.In the model, the pontoon segments are regarded as Euler-Bernoulli beams with hinges at both ends, while the action of the floating body and the hydrostatic water is equivalent to the elastic support distributed along the length of the beams. The adjacent segments are connected by hinges with rotational stiffness.The relationship between the structural self-resonance characteristics and the moving vehicle load response with the above two stiffness parameters is investigated.The results show that the proposed method can effectively obtain the response sensitivity interval of the floating body support stiffness and the rotational stiffness of the connection hinges. As the rotational stiffness increases, the segment connection transitions from articulation to rigidity, and the relative angle of the two ends of the hinged joint in the modal state is changed from the “sharp angle” mutation form to the smooth form. When the rotational stiffness is smaller, there is the vertical direction of the connection.When the rotational stiffness is small, significant vertical displacement extremes and corner mutations occurs on the connection；however once the stiffness reaches a certain value, the structural displacement and internal force envelope tends to be stable.

Structural dynamics modeling is a crucial technological task in the development of launch vehicles, load design, mechanical environment prediction, control system design, and POGO vibration suppression. Based on the evolutionary process of launch vehicles technologies, this paper reviews the development and application of structural dynamics analysis from four modelling approaches: the beam model, beam-shell hybrid model, the 3D model based on direct modeling and the 3D model based on model assembly. Additionally, this paper also covers the evolution of structural dynamic modeling technique and modal test in launch vehicle areas. Building on advances in numerical computation and the iterative refinement of launch vehicle methodologies, this paper further examines several emerging trends in the field several aspects, including efficient liquid-solid coupling computational technology, multidisciplinary dynamics analysis technology, dynamics analysis twin technology, and launch vehicle dynamics analysis technology based on artificial intelligence.

The inverse kinematics of redundant manipulators must avoid joint limits to ensure solutions comply with the actual physical constraints. Conventional based on differential kinematicsbased methods typically consider only local instantaneous states and cannot guarantee that the joints remain within the physical limits throughout continuous motion. To address this issue, this paper proposes an inverse kinematics method for redundant manipulators based on model predictive control. By combining the null space parameterization of the Jacobian matrix, the proposed method effectively accounts for the future evolution of the system’s kinematic states and constraints. The constraints and optimization objective functions are designed to handle joint limits. The inverse kinematics problem is transformed into a constrained optimization problem, where redundancy is fully exploited to avoid joint limits. Furthermore, to ensure the feasibility of the optimization problem, a task scaling method is introduced to handle violations of constraints by the end-effector velocity. Simulation results on a 7-DOF redundant manipulator demonstrate that, compared with benchmark methods, the proposed method can predict and avoid potential joint limit violations while accurately tracking the target trajectory of the end-effector.

This study presents a reinforcement learning-based intelligent method for optimizing the actuation of configuration multi-segment earthworm-like robots. A dynamic model of the multi-segment robotic system is first established, and the actuator arrangement problem is formulated as a Markov decision process. By designing a multi-discrete action space, computational costs are significantly reduced. A reward function integrating locomotion speed and energy consumption constraints is proposed to effectively balance exploration and exploitation. For actuator-limited conditions, an action masking mechanism enables efficient policy search under hard constraints. Key findings include: (1) Midline-symmetric actuation yields optimal performance under full-drive conditions；(2) A “posterior-priority, centripetal-clustering” distribution pattern emerges under constrained actuation.

Blade tip clearance is one of the most critical factors affecting the flight safety of coaxial rigid rotor helicopters. To accurately predict the blade tip clearance during forward flight, this study establishes a rotor/body coupling aeroelastic model based on 15-degree-of-freedom (15-DOF) medium-deformable beam and free wake model. Validation against the rotor natural frequency of XH-59A demonstrates a computational error that less than 5%, demonstrating the accuracy of the forward-flight blade tip clearance prediction method. The proposed method is then applied to analyzing the influence of lateral differential control, pitch angle, and sideslip angle on blade tip clearance during forward flight. The results indicate that lateral differential control can effectively control rotor rolling moment, and lateral differential control serve as a reliable means to ensure safe blade tip clearance during forward flight. Additionally, reduction in fuselage pitch angle during forward flight leads to more critical blade tip clearance conditions. An increase in sideslip angle affects the rotor lift offset and reduce blade tip clearance.

With the advancement of intelligent driving technology, high-precision vehicle status information has become important urgent. Road gradient is a crucial parameter for vehicle operation, having a significant impact on the vehicle’s dynamics control. High-precision and low-latency road gradient estimation is a prerequisite for precise control, which can effectively enhance the intelligence level of the vehicle. Adaptive Extended Kalman Filter (AEKF) is widely used for road gradient estimation, but exhibits limitations in complex operating conditions with different noise levels. This paper proposes an improved adaptive Kalman filter algorithm that enhances the estimation accuracy by introducing dynamic noise scaling factors. The effectiveness of the proposed method is validated through simulation tests under double lane change conditions and steady-state circular motion conditions. The results show that the proposed method achieving a road gradient estimation accuracy with a Root Mean Square Error (RMSE) of less than 2°.

Based on the Shanxi Linyi Yellow River Bridge, an experimental study was conducted on the wind-induced vibrations and control of an ultra-long steel launching nose during the incremental launching construction of a steel-concrete composite girder bridge. First, the dynamic characteristics of the bridge structure were analyzed using the finite element method. Then, aeroelastic models of the bridge with the launching nose were designed and fabricated. Wind tunnel tests under turbulent flow conditions were carried out to examine the buffeting responses of the launching nose under different yaw angles. Finally, considering the actual characteristics of the bridge, an inclined stay cable system anchored at the center of the pier was proposed to suppress the wind-induced vibrations of the launching nose. The results show that under the design reference wind speed, the standard deviations of vertical and lateral displacements at the cantilever tip of the launching nose are 0.10 m and 0.04 m, respectively. Within a yaw angle of 30°, the vibration responses remain relatively constant, while a significant reduction is observed when the yaw angle exceeds 30°. The proposed inclined wind-resistance cables can reduce the vertical vibration magnitude at the cantilever tip by approximately 50%.

To investigate the influence of geometric nonlinearity on human-induced vibrations of flexible suspension bridges. A nonlinear finite-element model of a flexible pedestrian suspension bridge is established based on an engineering background, and validated using measured data. On this basis, nonlinear transient vibration analysis of the suspension bridge, considering geometric nonlinearity, is conducted. The analysis reveals that the structural displacement response time histories and time-frequency characteristics under different main cable sag-to-span ratios and excitation amplitudes, as well as the response-excitation amplitude curves. The results further show that single-frequency excitation at low-order vertical modes can induce high-order frequency vibrations at 1：2 and 1：3 ratios. When the ratio of vertical to horizontal natural frequencies is close to 2：1, a certain level of vertical excitation on the main girder can cause lateral sway of the structure. Increasing the main cable sag-to-span ratio can effectively suppress vertical and lateral coupling vibrations. As the vertical excitation level increases, the sway amplitude exhibits a sudden jump and significant increase at a critical excitation level. Under pedestrian-induced excitation, the flexible suspension bridge exhibits significant geometric nonlinear vibration characteristics.

Fluid-conveying pipes hold significant engineering value. In practical applications, pipes are often subjected to vibrations due to various factors. Excessive vibration amplitudes may lend to damage to the pipe itself and its supporting structures, while even small-amplitude vibrations can cause cumulative fatigue over time. Therefore, mitigating pipe vibrations has become a critical issue that needs to be addressed.In this study, a fluid-conveying pipe model is established based on the Timoshenko beam theory. The nonlinear energy sink (NES) cell, as a novel vibration suppression concept, is applied to reduce pipe vibrations. The governing equations of the system are derived using the generalized Hamilton’s principle, and the system’s natural frequencies are obtained through the complex modal method. The system’s response is solved using the harmonic balance method and numerical simulations. Furthermore, the effects of different NES cell quantities and installation configurations on vibration-suppression performance are investigated. The results indicate that when the external excitation is near specific frequencies, a single-point concentrated distribution exhibits superior vibration reduction performance, whereas multi-point concentrated and uniform distributions provide superior suppression performance under broadband excitation.