Explore the vast range of titles available.

The limitations associated with traditional screw-based and cable-based deployment mechanisms for space deployable structures, such as deployment stiffness, accuracy, and distance, are effectively overcome by introducing the concept of a variable diameter internal drive device. To enhance stability during the discontinuous surface transition phase inside the tubular structure, a thin-walled flexible beam structure is adopted for the driving deployment unit. The analysis employs the spatial absolute nodal coordinate formulation, integrating the pose states of each node into the global coordinate system. The three-dimensional displacement field and rotational angle changes at different time intervals are obtained using the unit shape function matrix and Kirchhoff theory. Subsequently, a dynamic model of the corresponding spatial nodes is established using the virtual work principle. This significant improvement enhances the dynamic characteristics of the coupled rigid-flexible deformation of the driving deployment unit under radial and axial external forces, surpassing the previously used flexible beam structure. The dynamic simulation analysis is performed using the finite element method and validated through experimental tests. The experimental results confirm the driving deployment unit’s stability and successful achievement of the desired functionalities, as demonstrated by the endpoint displacement, three-dimensional centroid displacement, and trajectory rotation angle.

The exponential and Cayley maps on SE(3) are the prevailing coordinate maps used in Lie group integration schemes for rigid body and flexible body systems. Such geometric integrators are the Munthe–Kaas and generalized- α schemes, which involve the differential and its directional derivative of the respective coordinate map. Relevant closed form expressions, which were reported over the last two decades, are scattered in the literature, and some are reported without proof. This paper provides a reference summarizing all relevant closed-form relations along with the relevant proofs, including the right-trivialized differential of the exponential and Cayley map and their directional derivatives (resembling the Hessian). The latter gives rise to an implicit generalized- α scheme for rigid/flexible multibody systems in terms of the Cayley map with improved computational efficiency.

A finger seal is a flexible sealing device widely used in high-temperature and high-pressure environments such as gas turbines. Its force analysis is the key to the design and optimization of finger seal performance. At present, most of the research on force analysis of finger seals is focused on the whole seal ring, but each finger beam has a different contact performance with the shaft. In this paper, a new force analysis method for contacting finger seals is proposed, as well as the model of finger seals with or without eccentricity is established to analyze the force of a single finger beam. The curved flexible finger beam is transformed into a straight one loaded with a certain moment at the end of it. The force acting on the finger beam is studied and compared with the existing reference to demonstrate the feasibility of the analysis method. By changing each parameter of the finger seal, the relationship between seal force and structural parameter is investigated. It shows that this method is meaningful to the calculation results of seal force for single finger beam and can promote the development of finger seal and make it further in engineering application.

In order to improve the vibration suppression effect of the flexible beam system, active control based on soft piezoelectric macro-fiber composites (MFCs) consisting of polyimide (PI) sheet and lead zirconate titanate (PZT) is used to reduce the vibration. The vibration control system is composed of a flexible beam, a sensing piezoelectric MFC plate, and an actuated piezoelectric MFC plate. The dynamic coupling model of the flexible beam system is established according to the theory of structural mechanics and the piezoelectric stress equation. A linear quadratic optimal controller (LQR) is designed based on the optimal control theory. An optimization method, designed based on a differential evolution algorithm, is utilized for the selection of weighted matrix Q. Additionally, according to theoretical research, an experimental platform is built, and vibration active control experiments are carried out on piezoelectric flexible beams under conditions of instantaneous disturbance and continuous disturbance. The results show that the vibration of flexible beams is effectively suppressed under different disturbances. The amplitudes of the piezoelectric flexible beams are reduced by 94.4% and 65.4% under the conditions of instantaneous and continuous disturbances with LQR control.

Flexible beams are usually modeled under the assumption of large displacement, finite rotation, but with small strains. Such hypothesis allows the equation of motion to be built using co-rotational finite elements. The co-rotational formulation decomposes the total motion of a structural element into two parts: a rigid body and an elastic (small) deformation. This way, a geometric nonlinearity caused by the large displacements and rotations of the beam’s cross sections can be efficiently modeled. The novelty of this paper consists in incorporating this modeling technique inside a standard method to compute nonlinear normal modes (NNMs). The resulting method becomes a dedicated one to the analysis of complex flexible beams, including those with nonuniform cross sections and with pre-deformations. Those cases are not easily incorporated by other methods in the literature. The harmonic balance method (HBM) is used here to approximate the periodic solutions of the system. The arc-length parametrization is used to perform the continuation with respect to the energy level. The alternating frequency-time (AFT) method is used to compute the Fourier coefficients of the nonlinear elastic forces computed from the co-rotational finite elements. Two examples are used to illustrate the performance of the proposed method: bi-clamped flexible beams with nonuniform cross sections and a flexible riser (offshore oil pipes) in catenary configuration.

Purpose In engineering, flexible slender beams often encounter strong nonlinear large deformation problems, which will greatly hinder the precise control and lightweight optimization of flexible components. Therefore, a method that can accurately analyze the large deformation problem of flexible slender beams is needed. Methods In this paper, an Absolute Nodal Coordinate Formulation (ANCF) based on the Moving Least Squares (MLS), denoted as MANCF, is developed to deal with the large deformation problem of plane flexible slender beams accurately and efficiently. The MLS in the meshfree method does not need to divide the mesh, which can avoid the problems such as mesh distortion caused by mesh division. MLS can ensure the high-order continuity of its shape function through the basis function and the weight function, and ensure the continuity and accuracy of the beam curvature through the highly overlapping support domain. Results In this paper, through three static cases and two dynamic cases, it is demonstrated that MANCF (Absolute Nodal Coordinate Formulation based on moving least square method) can obtain higher calculation accuracy and ensure the continuity of beam curvature compared with traditional ANCF in dealing with large deformation analysis of flexible beams. In addition, in dynamic problems, the results of MANCF are always better than those of traditional ANCF, and it also has good applicability to complex multi-body dynamic systems. Conclusion MANCF can effectively solve the drawbacks caused by meshing in traditional ANCF, and achieve higher accuracy while ensuring the continuity of beam curvature, which shows that MANCF has great potential in engineering problems.

This research addresses the phenomena of thermoelastic damping (TED) and frequency shift (FS) of a thin flexible piezoelectro-magneto-thermoelastic (PEMT) composite beam. Its motion is constrained by two linear flexible springs attached to both ends. The novelty behind the proposed study is to mimic the uncertainties during the fabrication of the beam. Therefore, the equation of motion was derived utilizing the linear Euler–Bernoulli theory accounting for the flexible boundary conditions. The beam’s eigenvalues, mode shapes, and the effects of the thermal relaxation time (t1), the dimensions of the beam, the linear spring coefficients (KL0 and KLL), and the critical thickness (CT) on both TED and FS of the PEMT beam were investigated numerically employing the Newton–Raphson method. The results show that the peak value of thermoelastic damping (Qpeak−1) and the frequency shift (Ω) of the beam increase as t1 escalates. Another observation was made for the primary fundamental mode, where an increase in the spring coefficient KLL leads to a further increase in Ω. On the other hand, the opposite trend is noted for the higher modes. Indeed, the results show the possibility of using the proposed design in a variety of applications that involve damping dissipation.

A three-dimensional T-shaped flexible beam deformation was investigated using model experiments and numerical simulations. In the experiment, a beam was placed in a recirculating water channel with a steady uniform flow in the inlet. A high-speed camera system (HSC) was utilized to record the T-shaped flexible beam deformation in the cross-flow direction. In addition, a two-way fluid-structure interaction (FSI) numerical method was employed to simulate the deformation of the T-shaped flexible beam. A system coupling was used for conjoining the fluid and solid domain. The dynamic mesh method was used for recreating the mesh. After the validation of the three-dimensional numerical T-shaped flexible solid beam with the HSC results, deformation and stress were calculated for different Reynolds numbers. This study exhibited that the deformation of the T-shaped flexible beam increases by nearly 90% when the velocity is changed from 0.25 to 0.35 m/s, whereas deformation of the T-shaped flexible beam decreases by nearly 63% when the velocity is varied from 0.25 to 0.15 m/s.

PurposeIndustrial robots are extensively used in the robotic assembly of rigid objects, whereas the assembly of flexible objects using the same robot becomes cumbersome and challenging due to transient disturbance. The transient disturbance causes vibration in the flexible object during robotic manipulation and assembly. This is an important problem as the quick suppression of undesired vibrations reduces the cycle time and increases the efficiency of the assembly process. Thus, this study aims to propose a contactless robot vision-based real-time active vibration suppression approach to handle such a scenario.Design/methodology/approachA robot-assisted camera calibration method is developed to determine the extrinsic camera parameters with respect to the robot position. Thereafter, an innovative robot vision method is proposed to identify a flexible beam grasped by the robot gripper using a virtual marker and obtain the dimension, tip deflection as well as velocity of the same. To model the dynamic behaviour of the flexible beam, finite element method (FEM) is used. The measured dimensions, tip deflection and velocity of a flexible beam are fed to the FEM model to predict the maximum deflection. The difference between the maximum deflection and static deflection of the beam is used to compute the maximum error. Subsequently, the maximum error is used in the proposed predictive maximum error-based second-stage controller to send the control signal for vibration suppression. The control signal in form of trajectory is communicated to the industrial robot controller that accommodates various types of delays present in the system.FindingsThe effectiveness and robustness of the proposed controller have been validated using simulation and experimental implementation on an Asea Brown Boveri make IRB 1410 industrial robot with a standard low frame rate camera sensor. In this experiment, two metallic flexible beams of different dimensions with the same material properties have been considered. The robot vision method measures the dimension within an acceptable error limit i.e. ±3%. The controller can suppress vibration amplitude up to approximately 97% in an average time of 4.2 s and reduces the stability time up to approximately 93% while comparing with control and without control suppression time. The vibration suppression performance is also compared with the results of classical control method and some recent results available in literature.Originality/valueThe important contributions of the current work are the following: an innovative robot-assisted camera calibration method is proposed to determine the extrinsic camera parameters that eliminate the need for any reference such as a checkerboard, robotic assembly, vibration suppression, second-stage controller, camera calibration, flexible beam and robot vision; an approach for robot vision method is developed to identify the object using a virtual marker and measure its dimension grasped by the robot gripper accommodating perspective view; the developed robot vision-based controller works along with FEM model of the flexible beam to predict the tip position and helps in handling different dimensions and material types; an approach has been proposed to handle different types of delays that are part of implementation for effective suppression of vibration; proposed method uses a low frame rate and low-cost camera for the second-stage controller and the controller does not interfere with the internal controller of the industrial robot.

Boundary supporting stiffness is an important structural parameter for status monitoring and defect detection. In this paper, a novel Fourier series-Neural network hybrid approach is proposed to identify the boundary-supporting stiffness of a flexible beam. The transverse displacements of the flexible beam under arbitrary boundary conditions are described using the admissible function constructed by the Fourier series with supplementary terms. The modal characteristics corresponding to the different boundary-supporting stiffness are solved by the energy principle and Rayleigh-Ritz procedures. The effect of the boundary supporting stiffness on the natural frequencies is analyzed. On this basis, the PSO-BP (particle swarm optimization backpropagation) neural network is established to describe the relationship between boundary supporting stiffness and the natural frequencies. The results show that the neural network built by the proposed method has a good effect on stiffness identification and performs better than the common network. By further comparing the results output from the proposed model with those obtained by the finite element method and the experiment, the effectiveness and feasibility of the proposed model in practical application are demonstrated.