Hinged Plate Research Articles

Reinforcement learning vibration control and trajectory planning optimization of translational flexible hinged plate system

In order to suppress the vibration of a translational flexible hinged plate system, a vibration suppression scheme based on trajectory planning and piezoelectric active control is proposed. The dynamic model of the system is established by finite element method (FEM), and the experimental parameters are identified by wavelet analysis and simulated annealing (SA) algorithm. After obtaining the accurate system model, an optimized vibration suppression trajectory is designed based on the artificial bee colony (ABC) optimization algorithm to reduce the vibration excited during and after translation. Aiming at piezoelectric active vibration control, an actor-critic with experience replay (ACER) reinforcement learning (RL) algorithm is designed to train the vibration modal controllers in simulation environment. In the simulation environment and experimental environment, piezoelectric active control is carried out under the conditions of fixed base and trajectory motion, compared with pure trajectory motion. The simulation and experimental results show that ABC optimization algorithm can attenuate vibration excitation better than classical trajectory, and ACER RL modal controllers also show better vibration suppression effect than large-gain proportional-derivative (PD) controllers, especially for small amplitude vibration.

Temporary hemi-epiphysiodesis with tension band plates in skeletally immature patients with genu valgum: Faster correction in patients with more than 2 years of expected time of growth remaining.

Hemi-epiphysiodesis procedures in skeletally immature patients are commonly done to correct genu valgum over time. This study seeks to demonstrate the average rate of deformity correction for genu valgum using hinged tension band plates, while examining different age groups and sex-related differences. A retrospective chart review of patients who underwent hemi-epiphysiodesis with hinged tension band plates for valgus knee deformity from 2012 to 2022 by one pediatric orthopaedic surgeon was performed. Expected time of growth remaining was calculated as the difference between age of skeletal maturity and bone age at time of surgery. The mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, mechanical femoral tibia angle, screw divergence angle, and hinge angle were measured immediately after implant placement and prior to implant removal. 54 skeletally immature patients were treated for pathologic genu valgum. The mean age at time of surgery was 12.5 ± 1.9 years. The radiographic measurement of the valgus deformity between the beginning and end of treatment showed significant correction (p = 0.002). The lower limb axis of the younger cohort corrected significantly faster (7.5 ± 4.6°/year) than the older cohort (5.3 ± 2.8°/year) (p = 0.030). The mechanical lateral distal femoral angle correction rate was also significantly different between the two cohorts (7.0 ± 4.7°/year vs. 4.8 ± 2.8°/year, respectively (p = 0.002)). The group with greater expected time of growth remaining demonstrated a significantly faster rate of correction than the group with less than 2 years of growth remaining (p < 0.001). This study reaffirms the finding that timing is essential when performing temporary hemi-epiphysiodesis for valgus knee deformity in skeletally immature patients.

Experimental study on the flow-induced vibrations of a circular cylinder with a rear flexibly hinged splitter plate

The flow around a circular cylinder is a canonical configuration that may be encountered in many engineering applications, as for instance, civil engineering, architecture, or marine structures. In particular, when bluff bodies are slender and feature low mass-damping characteristics, they may undergo flow-induced vibrations (FIVs), which may result in severe structural fatigue and damage. Here, we present an experimental study on the effect of flexibly hinged splitter plates in the FIV of a flexibly mounted circular cylinder (of diameter D) subject to an uniform cross-flow of velocity u∞. The dynamic response and forcing of the low mass-damping system is characterized for plates of different lengths Lp and different values of the torsional stiffness of the hinge kp. Reductions of the dynamic response of more than 90% can be generally reached at the upper branch, especially when a plate of length l*=Lp/D=2 with intermediate degree of torsional stiffness is attached, which is shown to represent the best solution as it mitigates the oscillations of the system (cylinder and plate) for the whole range investigated of reduced velocity U*=u∞/fnD=[3.9,9.8], where fn is the natural frequency of oscillation. In general, the hinged plates are able to attenuate the vortex-induced vibration system response by increasing shedding frequency, until the ratio f*=f/fn&amp;gt;1 is reached. At high values of U*, a general transition to galloping-like dynamics, characterized by f*&amp;lt;1, occurs. The tested hinged plates modify the transition between regimes, which is associated with shifts in the phase difference between the forcing and response, combining features of the dynamics of both flexible and static rigid plates already reported in the literature. The use of hinged plates has been proven to provide with a significant attenuation of the system response and its associated drag, a feature that can be considered of practical relevance in many engineering applications. In addition, the key aspects for designing these elements as the torsional stiffness and plate length have been analyzed here.

Vibration vision measurement and wavelet neural network control of flexible hinged plate

Vibration vision measurement and wavelet neural network control of flexible hinged plate

Viscoplastic flow between hinged plates

The incompressible motion of viscoplastic fluid between two semi-infinite rigid plates, hinged at their ends and rotating towards one another at constant angular velocity, generates self-similar flow fields because there is no externally imposed length scale in the absence of inertia. The magnitude of the strain rate scales with the angular velocity of the plates and the dimensionless deviatoric stresses are functions only of the polar angle and a dimensionless measure of the yield stress; they are independent of the radial distance from the corner. These flows feature unyielded regions adjacent to the boundaries for sufficiently large angles between the plates. Moreover, when the dimensionless yield stress is large, there are viscoplastic boundary layers that are attached to the boundary or the plug, the asymptotic structures of which are constructed.

Trajectory planning and vibration control of translation flexible hinged plate based on optimization and reinforcement learning algorithm

Aiming at the flexible hinged plate with translational motion,a hybrid control strategy combining motion trajectory optimization and piezoelectric active control is developed. Combining finite element modeling (FEM) and experimental system identification, the piezoelectric driving model and motor acceleration driving model of the flexible hinged plate are obtained. On this basis, the immune optimization algorithm is adopted to obtain the optimal trajectory of vibration suppression. An Auto-Soft-Actor-Critic (Auto-SAC) reinforcement learning (RL) algorithm is designed to train modal active controllers. The experimental setup is constructed. Compared with the classical trajectory, the optimized trajectory shows a good effect in avoiding excitation vibration. For piezoelectric active control, the Auto-SAC RL modal controller is superior to the large-gain PD controller in suppressing vibration, and its nonlinearity effectively overcomes the problem that the traditional linear controller has limited ability to suppress small amplitude vibration. In addition, the hybrid control strategy of trajectory optimization and Auto-SAC RL modal controllers can effectively reduce and suppress the vibration of the flexible hinged plate in translational motion.

Fracture characteristics of basic roof and mechanism of strata behavior in a pillarless working face

Abstract As a research hotspot, pillarless coal mining technology has a high resource recovery rate and low roadway surrounding rock stress. To grasp the three-dimensional fracture characteristics of the basic roof is the basic to reveal the strata behavior mechanism in the pillarless working face. Thus, aiming at pillarless coal mining, the analytical solution of three-dimensional fracture mechanics models of a basic roof was analyzed by elastic thin plate theory; the principal stress distribution of a basic roof being cut by continuous artificial fractures and discontinuous artificial fractures was analyzed; the fracture characteristics of the basic roof was revealed and the strata behavior mechanism was obtained. The following conclusions can be drawn: (i) an ‘O + X’ fracture occurred in the basic roof of a traditional working face, while an opposite-trapezoid-shaped or ≡-shaped fracture was generated in the pillarless working face. (ii) When the basic roof broke, the trapezoidal or rectangular hinged plate traversed the entire pillarless working face, causing the end supports to be pressured, while the trapezoidal hinged plate did not traverse the entire traditional working face and the end supports were not pressured. (iii) The break of a basic roof induced by artificial fractures in pillarless mining reduced or even eliminated the triangular hinged plate area along the goaf edges, making a roadway in the stress relief zone. (iv) Compared with the fractures in traditional roadways and in a discontinuous roof-cutting roadway, continuous fractures could minimize surrounding rock stress and make it easy to maintain a roof-cutting roadway.

Reinforcement learning vibration control for a flexible hinged plate

A reinforcement learning (RL) vibration control method for a flexible hinged plate is developed, including combined bending and torsional vibrations. The experimental setup is constructed. Two laser displacement sensors are used as detection sensors, and two-channel piezoelectric actuators are used to suppress both bending and torsional vibrations simultaneously. A method combining finite element modeling (FEM) and experimental identification is applied to obtain an accurate model of the system. The obtained model is constructed as an RL environment, and a deep deterministic policy gradient (DDPG) RL algorithm based on the priority experience replay (PER) is designed to train modal controllers. The RL modal controllers were transferred to the real experimental system by using the parameter transfer method, and the vibration control experiments were conducted by combining the bending and torsional vibration control method. Simulation and experimental results demonstrate that the controller trained by the proposed deep RL algorithm has better control effects compared with PD control, especially for small amplitude vibration.

A shape reconstruction and visualization method for a flexible hinged plate using binocular vision

A binocular vision-based shape deformation reconstruction and visualization method for a flexible hinged plate is proposed. The deformation of the flexible hinged plate in bending mode and torsional mode is investigated. In order to measure the deformation, a binocular vision system is used as the detector. Image processing functions are called to obtain offsets of the mark points pasted on the plate surface. Several types of surface fitting methods are implemented to fit the mark point array into a curved surface. The shape reconstruction graphics of the flexible hinged plate can be obtained. Moreover, the influence of deformation amplitude and stiffness of two flexible hinges on visualization results is studied. The simulation work for curve fitting is conducted by using the measured signals by the binocular stereo vision. The experiments on visual measurement, shape reconstruction and visualization are conducted, using the constructed experimental system and investigated methods. The experimental results show that the quadratic fitting method can be a better curved surface fit for the flexible hinged plate both in bending mode and in torsional mode, and visualization can be realized in real time.

Fuzzy neural network vibration control on a piezoelectric flexible hinged plate using stereo vision detection

Vibration control on a two-connected piezoelectric flexible hinged plate is investigated, using a fuzzy neural network algorithm based on binocular vision measurement. As for vision sensing, a method to acquire vibration signals of the low frequency bending and torsional mode is investigated. To damp out the residual vibration quickly, the fuzzy neural network is applied to ensure the stability and control effect adaptively. To verify the stereo vision measurement method and the applied controller, an experimental setup of the piezoelectric flexible hinged plate with a binocular stereo vision is constructed. Experiments are conducted by using the binocular stereo vision measurement system and the adopted controller. The experimental results demonstrate the feasibility of the visual measurement method. Furthermore, the designed fuzzy neural network can attenuate the bending and torsional vibrations quickly, in comparison with proportional and derivative control, particularly for the small-level residual vibration.

A novel vibration measurement and active control method for a hinged flexible two-connected piezoelectric plate

Abstract A novel non-contact vibration measurement method using binocular vision sensors is proposed for piezoelectric flexible hinged plate. Decoupling methods of the bending and torsional low frequency vibration on measurement and driving control are investigated, using binocular vision sensors and piezoelectric actuators. A radial basis function neural network controller (RBFNNC) is designed to suppress both the larger and the smaller amplitude vibrations. To verify the non-contact measurement method and the designed controller, an experimental setup of the flexible hinged plate with binocular vision is constructed. Experiments on vibration measurement and control are conducted by using binocular vision sensors and the designed RBFNNC controllers, compared with the classical proportional and derivative (PD) control algorithm. The experimental measurement results demonstrate that the binocular vision sensors can detect the low-frequency bending and torsional vibration effectively. Furthermore, the designed RBF can suppress the bending vibration more quickly than the designed PD controller owing to the adjustment of the RBF control, especially for the small amplitude residual vibrations.

Antipodal Vivaldi antennas with foldable hinged plates for adaptive polarization and gain adjustments

AbstractThis letter proposes a novel approach to adaptive polarization and gain adjustments for antipodal Vivaldi antennas using foldable hinged plates. The proposed antenna consists of upper and lower flared wings, and the wings are electrically extended using two rectangular plates. Metal hinges are then adopted to fold and unfold the plates, which allows the antenna to adjust the polarization in the entire range of the axial ratio and to further enhance the gain in the end‐fire direction. Measured antenna characteristics demonstrate that the polarization and the gains are adaptively adjusted by varying the tilt angles of the hinged plates without a distortion of the broadband properties.

Extremal principal eigenvalue of the bi-Laplacian operator

In this paper we propose two numerical algorithms to derive the extremal principal eigenvalue of the bi-Laplacian operator under Navier boundary conditions or Dirichlet boundary conditions. Consider a non-homogeneous hinged or clamped plate Ω, the algorithms converge to the density functions on Ω which yield the maximum or minimum basic frequency of the plate.

Influence of the inhomogeneity of the principal stress state on the critical loads of a plate with a crack

A plane problem of the stability of a hinged (integral boundary condition) plate with a central crack is formulated and solved using an exact approach. The plate is compressed along the crack by a constant surface load in inhomogeneous subcritical state. The mechanical effects due to the inhomogeneity of the principal stress state are revealed

The Study on Designing of Hinged Plates Model Test

Abstract The paper will research on the cracking mechanism of hinged plates, it designed on the condition of different cracking length the extension of cracks and cracking mechanism in the longitudinal side panel and middle panel and put forward the corresponding reinforcement scheme and test plan.

Fabrication of Hinged Mirrors Using a Strain-Driven Self-Assembly Method on a GaAs Substrate

Hinged mirror arrays are widely utilized for display applications and optical communication. They can be fabricated by an self-assembly technique using the strain in lattice-mismatched epitaxial layers. A multilayer structure including a strain-compensated layer, a digital alloy sacrificial layer and a strain bilayer, is grown by molecular-beam epitaxy. Self-assembly hinged mirrors on a GaAs substrate have been successfully fabricated by photolithography and selective etching. The hinge fabrication method with a strain bilayer is simple and flexible. Structures formed by multiple hinged plates will enable the self-assembly of more complex three-dimensional microstructures.

Approximate analytical solutions of stability problems for skew plates under combined loading

The known analytical solutions of the linearized stability problems for rectangular hinged plates under the combined loading are generalized to the similar problems for skew plates, the deformation mechanics of which is described by the equations of the classical theory formed in the oblique Cartesian coordinates.

Numerical Analysis of Reasonable Hinge Joints Size of Reinforced Concrete Hinged Plates

In order to study the stress distribution in hinge joints of different depth and the effects of hinged plate by hinge joints depth, 5 group ANSYS finite element models of concrete simply supported hinged plates were built, hinge joints stress of models have been compared under the center load and side load, analysis has been made on the hinge joints of maximal stress. The analysis results indicated that with the increase of the depth of hinge joints, the transverse tensile stress, vertical shear stress and longitudinal tension stress were all showed regular distributions, and with the increase of the depth of hinge joints from 10cm to 26cm, the maximum reduction value of transverse tensile stress in hinge joints was 3.25MPa, the reduction range was 51.9%; the maximum reduction value of vertical shear stress was 1.06MPa, the reduction range was 77.9%; longitudinal compressive stress decreased gradually, and longitudinal tensile stress increased; the maximum reduction value of hinged plates deflection difference was 0.16mm, the reduction range was 36.4%; the transverse tensile stress of hinged plates’ bottom increased. Therefore, increasing the depth of hinge joints was the most effective way to increase the transverse stiffness of slab girder and to prevent hinge joints damage. At the same time, the tensile reinforcements setting in transverse and longitudinal at the bottom of hinge joints and the tensile reinforcements setting in transverse at the bottom of slab girder should be strengthened.

Experimental Study of Ultimate Bearing Capacity of Hinged Plates with Different Configuration Hinge Joints

To study the role of vertical shear stress on the ultimate bearing capacity of hinge plates under fatigue loading, and different configurations of hinge joints on ultimate bearing capacity of hinged plates, three groups of hinged plate experiments were studied. Two groups of hinge plates with shallow hinge joint configurations were tested with static loading and fatigue loading respective, a group of hinge plates with deep hinge joint configurations were tested with fatigue loading directly. The ultimate bearing capacity analysis of hinge plates was carried out through mid-span deflection differences of hinged plates on both sides of hinge joints and transverse strains on top and bottom of hinge joints. Shown from the experimental results, for the hinge plates with shallow hinge joints, the ultimate bearing capacity under static load was 342.9kN, and under fatigue load was 340kN, but the ultimate bearing capacity under fatigue load of hinge plate with deep hinge joints was 610kN. Therefore, the vertical shear stress is not the main factor which cause the hinge joints destruction of hinge plates; hinge joints configurations, especially the depth of the hinge joints have great impact of ultimate bearing capacity of hinge plates; in the strengthen checking of hinge joints while hinge plates design, checking the vertical shear strength only is not comprehensive, various factors should be taken into account.

On the Positivity Preserving Property of Hinged Plates

In this work we show that the Kirchhoff–Love model for a hinged plate $\Delta^2 v = f \text{ in }E,\; v = \Delta v - (1 - \sigma) \kappa v_n = 0 \text{ on }\partial E$ admits, for $f \in L^2(E)$ and $-1 < \sigma < 1$, a unique weak solution in $W^{2,2}(E) \cap W^{1,2}_0(E)$ which satisfies the positivity preserving property when $E \subset \mathbb{R}^2$ is a bounded, convex domain with $\mathcal{C}^{2,1}$ boundary.