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The fixed stroke fatigue test cannot simulate the real loading conditions of the landing gear, and the variable stroke fatigue test has increasingly become mainstream. A modular test device for fatigue tests for aircraft landing gears was designed, and the automatic control of the buffer stroke was realized with ectopic displacement control technology effectively. The horizontal loading cylinder could follow the wheel axis actively with the displacement active control technology. The follow-up loading along the vertical direction was realized by constructing a polar coordinate system and making the loading line automatic alignment. A split-type dummy wheel was designed to improve the loading accuracy, and a booster cylinder was designed to realize the control loading of high pressure combined with the hydraulic control system. The test results show that the technical scheme meets the design requirements, and the fatigue test was completed successfully. The device for landing gear variable stroke fatigue testing is appropriate for other landing gear static/fatigue tests. [ABSTRACT FROM AUTHOR]

To mitigate the challenges in managing the damage level of reinforced concrete (RC) pier columns subjected to cyclic reverse loading, this study conducted a series of cyclic reverse tests on RC pier columns. By analyzing the outcomes of destructive testing on various specimens and fine-tuning the results with the aid of the IMK (Ibarra Medina Krawinkler) recovery model, the energy dissipation capacity coefficient of the pier columns were able to be determined. Furthermore, utilizing the calibrated damage model parameters, the damage index for each specimen were calculated. Based on the obtained damage levels, three distinct pre-damage conditions were designed for the pier columns: minor damage, moderate damage, and severe damage. The study then predicted the variations in hysteresis curves and damage indices under cyclic loading conditions. The experimental findings reveal that the displacement at the top of the pier columns can serve as a reliable indicator for controlling the damage level of pier columns post-loading. Moreover, the calibrated damage index model exhibits proficiency in accurately predicting the damage level of RC pier columns under cyclic loading. [ABSTRACT FROM AUTHOR]

This paper proposes a variable mechanism structure based on a ball screw design for precise displacement control in axial piston pumps, with the objective of improving actuator position and velocity control within the displacement-controlled (DC) systems. Traditional valve-controlled cylinder variable mechanisms (VCCVM) often suffer from limited control precision over the swash plate due to numerous uncertain parameters within the hydraulic system. To address this issue, a ball screw is utilized to replace the original valve-controlled cylinder for swash plate control, enhancing accuracy and responsiveness. In addition, an in-depth analysis of the Ball Screw Variable Mechanism (BSVM) is conducted, leading to the development of a coupled mechanical–hydraulic dynamic model. Based on this model, a controller is designed to improve system performance. Finally, the effectiveness and high performance of the proposed new structure and control strategy were validated through comparative experiments and simulations. The experimental results confirm the advantages of the proposed design, demonstrating satisfactory improvements in control precision. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the temperature rise, noise and vibration between the rotor and the support bearings under the high-speed rotating state of the PMSMS, the bearingless technology is proposed for avoiding the contact between the rotor and the support bearings and achieving stable compensation of the motorized spindles under high-speed running state. Based on the modeling method of ordinary bearingless motors, mathematical models of the BPMSS and simulation experiments are carried out. At the same time, the variable structure PID is used in the displacement controller to optimize the displacement control of the rotor. The results prove the feasibility of bearingless technology on permanent magnet synchronous motorized spindles. The magnetic levitation system largely avoids the contact between the rotor and the support bearings, which can solve the noise and vibration problems of the rotor when running at high speeds. Variable structure PID has a stronger control effect on rotor displacement control than ordinary PID control strategy. [ABSTRACT FROM AUTHOR]

Standard methods of controlling geotechnical structures are based on testing of individual elements (e.g., piles, anchors, barrettes) or on inventory of their displacements (for instance, current control, i.e., monitoring of retaining structures). It is only the bridgework where, due to uniqueness and importance of structures, the examinations are often run for the whole structures. The main problems are then the following: how to ensure proper repeatability of measurement accuracy (for long-term testing), how to establish optimum criteria of assessing the test results, how to use the results to make possible repair actions and how to interpret the obtained results. Based on an example of test of bridge abutment out of reinforced earth, the paper presents the method of displacement testing, basic criteria of assessing the results, measurement results during static load phase, during dynamic phase and results of long-term measurements. Large number of measurements enables for both evaluation of technical condition of the structure under testing (which was the main goal of the procedures performed) and drawing conclusions referring to the methodology of testing the structure out of reinforced earth as concerns the evaluation criteria adopted.

It is not known in the literature why the behavior of rocks incurs the tunnel excavation and it remains unclear for what has been calculated in the initial studies. That’s why the most important thing to consider in tunnel construction works is to monitor rock mass behavior. The finite element method (FEM) can also analytically represent the static and dynamic behavior of the rock mass. Concretely, this makes it possible to calculate the behavior of very complex objects numerically. The present study embraces a geophysical prospecting which was carried out by the method of surface seismic tomography to reveal the lithology of the different formations and their geometry and the variation in speed of the subsurface formations at the level of the South portal of the Texana tunnel on Jijel province, in Algeria. The paper also consists in making a two-dimensional numerical study of the stability of the tunnel portals with the Phase.2 2D program. On the other hand, the calculation results will be compared with in-situ surveying to strengthen the numerical modeling. It can be concluded that the Anchor Bolts Support System gives good results in terms of displacement of the rock mass and satisfactory stability in terms of collapse analyzis of the tunnel portals.

Displacement control is critical to the design of retaining walls, especially in urban areas, to avoid any potential damage to adjacent structures during excavations. In this study, model tests are first conducted to investigate the stress and deformation mechanisms of an embedded cantilevered retaining (ECR) wall during excavations. The development of the wall top displacement and the active and passive earth pressures acting on the ECR walls during excavations are studied. Upon the experimental observations, a displacement-dependent earth pressure coefficient is proposed to derive an analytical solution to predict both the active and passive earth pressure acting on the ECR wall (pile), where the displacement value and displacement mode of the ECR wall (pile) are taken into account. Comparisons between the model predictions and test results are carried out. A good agreement is observed, which shows the validity of the proposed solution. Based on the proposed solution, a displacement-controlled method for the design of ECR walls (piles) that takes into account the location of the rotation point is proposed. Parametric studies are conducted to demonstrate the impact of deformation control and excavation depth on the design parameters of ECR walls (piles). [ABSTRACT FROM AUTHOR]

This paper aims to implement the controllable deformation of a structure using Shape Memory Alloys (SMA) actuators. A sensorless displacement estimation method is proposed. This method is tested on a prototype composed of a disc, beams, and SMA actuators. By measuring the variation of electrical resistivity in SMA springs, as a feedback signal in the closed-loop position control, the surface displacement is obtained without any external displacement sensor. The proposed method is validated by comparing the displacement values estimated by the electrical resistivity measurement with those measured by a laser sensor. The estimated displacement and the measured displacement follow the reference displacement with steady-state errors, respectively of 1.14% and 0.42%. [ABSTRACT FROM AUTHOR]

This paper discusses the role that structural stiffness plays in the context of designing adaptive structures. The focus is on load-bearing structures with adaptive displacement control. A design methodology is implemented to minimize the control effort by making the structure as stiff as possible against external loads and as flexible as possible against the effect of actuation. This rationale is tested using simple analytical and numerical case studies.

Electro-hydraulic servo systems (EHSSs) are nonlinear and uncertain due to their inappropriate fluid levels, air temperature, friction, and leakage. The finite-time tracking control is difficult with the use of a proportional, integral, and derivative (PID) controller, which no longer provides adequate and achievable control performance over the whole operating range. This has led to the idea of an iterative learning controller (ILC). An intelligent and memory-based learning control approach that attempts to imitate the human way of thinking. The proposed ILC has an additional learning gain, learning filter, and robustness filter to enhance the finite-time tracking performance and stability improvement. This study is focused on the design of the ILC to regulate the servo spool valve of an EHSS, which in turn controls the displacement of a hydraulic cylinder. In simulation and experimentation, vital parameters such as overshoot and settling time in the varieties of tests, the ILC has shown better results when compared to conventional PID controllers. In step input tracking at different operating points over 0-250 mm, the ILC has 40% less overshoot and settles 12-15 s faster than the PID controller. In sinewave tracking and disturbance rejection, the PID controller performs better than the ILC in integral square error and integral absolute error as the error indices are not considered as the objective function in the design of the controller. During a robustness test, the ILC rejects the uncertainty, which evidences the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The next generation of electrified heavy-duty mobile machines (HDMMs) requires more efficient hydraulic systems—to save energy and to compensate for the limited capacities of available mobile electric energy sources. This study is experimentally demonstrating the functionality, dynamic performance, and efficiency of such a more efficient but also cost-effective system. The demonstrator is a conventional nine-tonne telehandler that has been transformed by replacing the diesel engine with an electric machine (EM) and changing the boom function from valve to displacement control. Since the system control and the resulting dynamics are not trivial, key aspects of it are explained in the paper. With the functional system, achievable consumption reductions could be obtained by measuring five different representative work cycles repeatedly and comparing the average consumption values to the consumption of a purely valve-controlled but also electrified reference version. In four of five cycles, an average reduction of 21–31% was achieved, which confirms the simulation results from previous studies and the effectiveness of the concept. However, one cycle—characterized by serial movements and longer breaks of the boom movement—showed a reduction of only 3% and that the effectiveness of the concept can also be lower in certain cases that depend mainly on the operator. [ABSTRACT FROM AUTHOR]

Standard methods of controlling geotechnical structures are based on testing of individual elements (e.g., piles, anchors, barrettes) or on inventory of their displacements (for instance, current control, i.e., monitoring of retaining structures). It is only the bridgework where, due to uniqueness and importance of structures, the examinations are often run for the whole structures. The main problems are then the following: how to ensure proper repeatability of measurement accuracy (for long-term testing), how to establish optimum criteria of assessing the test results, how to use the results to make possible repair actions and how to interpret the obtained results. Based on an example of test of bridge abutment out of reinforced earth, the paper presents the method of displacement testing, basic criteria of assessing the results, measurement results during static load phase, during dynamic phase and results of long-term measurements. Large number of measurements enables for both evaluation of technical condition of the structure under testing (which was the main goal of the procedures performed) and drawing conclusions referring to the methodology of testing the structure out of reinforced earth as concerns the evaluation criteria adopted. [ABSTRACT FROM AUTHOR]

Previous earthquakes have proven that failure of framed structure particularly at joints of beam and column caused disastrous collapse in structures that are built without seismic codal provisions. Most of the traditionally built Reinforced Cement Concrete (RCC) framed structures existing are lacking adequate reinforcement at structural joints and these joints are shear deficient. The main objective of the research studies was to enhance behaviour and performances of exterior structural joints by retrofitting and testing for displacement-controlled reversed cyclic loading. The joints retrofitted exhibits higher levels of ultimate displacements, higher levels of ultimate capacity previous to failure and the joints failed prior to failure of column. The variable novelty in research were size and shape of mesh, woven mesh, mesh orientation and wrapping in all direction around joints, cementitious matrix laminates with aggregate chips less than 5 mm, epoxy resin to increase bond between old and new concreting and chicken wire mesh near to cover and displacement controlled reversed cyclic loading was applied to column. The experimental research work indicated that, retrofitting with woven wire mesh strengthening technique will enhance the displacement ductility, stiffness, energy dissipation and strain. Thus the proposed retrofitted method anticipated in predicting the shear strength of joints. [ABSTRACT FROM AUTHOR]

The ill-condition of stiffness matrix at the unstable region for example at the strain-softening region, the load control method will not be valid to give the solution therefore the displacement control method is essential to use. The stiffness matrix is changed at different steps by used load control and solution is found using any nonlinear solution method of Newton’s family. Therefore, Newton’s method will not give a solution to the unstable region. The iteration method and solution process may also stop when the diagonal element of the stiffness matrix becomes negative or zero if Newton's method is adopted. These difficulties need to be overcome and a non-positive definite stiffness matrix is retained and used for iteration in the arc-length method. A scientific review of literature has been made to pinpoint the difficulties faced in the prediction of complete load-displacement response of structures and techniques available to overcome the same. Displacement control methods have been reviewed with emphases on the arc length methods which can be integrated with the traditional finite element method.

Background: The theoretical advantages of hybrid constructs over multi-level fusion have been illustrated in clinical and biomechanical studies. However, there is no biomechanical data on hybrid constructs using load control analyses. There is also no clear data on whether there is a biomechanical difference if the arthroplasty is below or above a 1- or 2-level fusion. This work investigated the effect on segmental motion of having a cervical total disc arthroplasty implanted above or below a 1- or 2-level fusion. Methods: Segmental motions of 16 C2-T1 cervical spine specimens were measured as the specimens were tested to 1.5Nm in axial rotation and in flexion-extension under compressive preload. Tests were conducted on intact specimens, and then after arthroplasty with a 1-level and 2-level fusion. 8 specimens were in test Group 1, where the hybrid configuration had a total disc arthroplasty above a 1- or 2-level fusion. The arthroplasty was below the 1- and 2-level fusion in Group 2. Load control and displacement control analyses were conducted to determine the effect of the hybrid configurations on segmental motion. Results: In load control, compensatory motion increases were found at all non-instrumented cervical spine segments in flexion-extension and axial rotation. Flexion-extension and axial rotation ranges of motion at the total disc arthroplasty level were less than 1° different than intact.In displacement control, there was no consistent pattern of compensatory motion. Range of motion at the arthroplasty level was within 3.5° of intact. Conclusions: The total disc arthroplasty segmental level in a hybrid construct has similar amounts of motion as intact. This may shield the arthroplasty level and adjacent levels from supra-physiological motion and loading. These results suggest that a hybrid construct may be protective of adjacent segments, whether the total disc arthroplasty is above or below the fusion.

Operators of mobile platforms that employ hydraulic actuation, such as excavators, seek more efficient power transfer from source to load. Pump-controlled architectures achieve greater efficiency than valve-controlled architectures but exhibit poor tracking performance. We present a system-design optimization technique that ensures compliance with design requirements and minimizes peak input power, which correlates inversely with efficiency. We utilize the optimization technique to size a valve-controlled hydraulically actuated stabilized mount on a mobile platform. Our optimization framework accounts for the disturbance spectrum, a stabilization performance measure, the system dynamics, and control system design. Our technique features automated requirement derivation in the form of a parameter estimation, which supports design decisions under constraints. Our results show that one of four inequality constraints is active. This constraint represents a common design rule and results in limiting efficiency. We show that relaxing this constraint is practically feasible and leads to higher efficiency in achieving the required performance. We propose adding an inerter to justify the relaxed constraint and present the resulting open-loop servo transfer function. [ABSTRACT FROM AUTHOR]

A magnetic screw motor integrated by a magnetic screw and a permanent magnet synchronous motor offers high thrust density without friction and loss. However, its internal structure is complicated, resulting in difficulty to control its linear displacement to track the given signal in time and even getting out of control due to interference. In this article, to improve the tracking performance and anti-interference performance of the system, an active disturbance rejection controller (ADRC) is adopted to improve the current loop and makes up for nonlinear regional control in the closed-loop control system. To ensure the stability of the proposed scheme in the entire operation range, the design and the stability analysis are carried out in the continuous-time domain. The novel control algorithm enhances the flexibility of the magnetic screw motor by optimizing the nonlinear function in ADRC. In addition, to highlight the high-performance control of the ADRC for the magnetic screw motor, sliding mode control and PI control are added to compare with it. Finally, the reciprocating motion control is added to show the diversity of the functions of the magnetic screw motor, which verifies the effectiveness and feasibility of the control algorithm. [ABSTRACT FROM AUTHOR]

The electrohydraulic equipment of the coal gangue belt conveyor has been widely studied in recent years, but studies have been limited to the traditional hydraulic system with proportional valve and servo valve as control elements. Because of their own structural characteristics, proportional valves and servo valves have inherent defects such as low reliability, high cost and a long debugging cycle. It is necessary to carry out technological innovation and upgrading. This paper presents a hydraulic system scheme which uses digital valves instead of proportional valves and servo valves to control the belt conveyor propulsion system. Firstly, the system scheme is described in detail. Secondly, the simulation model of the control element digital valve is established, and its dynamic characteristics are analyzed in detail. Finally, the displacement tracking control of the new system is carried out to verify the feasibility of the proposed control scheme. The results show that the new digital hydraulic control system can effectively achieve the displacement control function of the belt conveyor propulsion system. [ABSTRACT FROM AUTHOR]

The next generation of electrified heavy-duty mobile machines (HDMMs) requires more efficient hydraulic systems—to save energy and to compensate for the limited capacities of available mobile electric energy sources. This study is experimentally demonstrating the functionality, dynamic performance, and efficiency of such a more efficient but also cost-effective system. The demonstrator is a conventional nine-tonne telehandler that has been transformed by replacing the diesel engine with an electric machine (EM) and changing the boom function from valve to displacement control. Since the system control and the resulting dynamics are not trivial, key aspects of it are explained in the paper. With the functional system, achievable consumption reductions could be obtained by measuring five different representative work cycles repeatedly and comparing the average consumption values to the consumption of a purely valve-controlled but also electrified reference version. In four of five cycles, an average reduction of 21–31% was achieved, which confirms the simulation results from previous studies and the effectiveness of the concept. However, one cycle—characterized by serial movements and longer breaks of the boom movement—showed a reduction of only 3% and that the effectiveness of the concept can also be lower in certain cases that depend mainly on the operator.

Existing control algorithms for seismic shake table tests (STTs) generally exhibit limitations such as poor acceleration tracking for displacement control, instability that results in table drift for direct acceleration, force, or velocity control, and the lack of a theoretical justification for hybrid control. Therefore, a reliable control algorithm has become key for effective shake table control. This paper presents acceleration‐based sliding mode control (SMC) as a solution to the drawbacks of the traditional force‐based SMC; in this manner, the influence of the force of the tested structure applied on the table as well as unmodeled complex nonlinear forces, such as friction, are counteracted. An acceleration‐based sliding mode hierarchical control (ASMHC) algorithm is proposed, where the acceleration‐based SMC is used as the high‐level controller to generate the corrected acceleration command, and the low‐level controller, that includes feed‐forward and feedback control, tracks the acceleration command in real time. The high‐level controller, having zero asymptotic stability, and the low‐level controller, designed based on the system transfer function, ensure tracking stability in time and frequency domains, respectively. The proposed ASMHC algorithm was first verified by a series of bare STTs, and was then applied to a real STT of a two‐story steel structure. The experimental results show that the proposed ASMHC algorithm can achieve good tracking of displacement, velocity, and acceleration in both time and frequency domains, which ensures accurate reproduction of seismic excitation in STTs. [ABSTRACT FROM AUTHOR]

The ill-condition of stiffness matrix at the unstable region for example at the strain-softening region, the load control method will not be valid to give the solution therefore the displacement control method is essential to use. The stiffness matrix is changed at different steps by used load control and solution is found using any nonlinear solution method of Newton’s family. Therefore, Newton’s method will not give a solution to the unstable region. The iteration method and solution process may also stop when the diagonal element of the stiffness matrix becomes negative or zero if Newton's method is adopted. These difficulties need to be overcome and a non-positive definite stiffness matrix is retained and used for iteration in the arc-length method. A scientific review of literature has been made to pinpoint the difficulties faced in the prediction of complete load-displacement response of structures and techniques available to overcome the same. Displacement control methods have been reviewed with emphases on the arc length methods which can be integrated with the traditional finite element method. [ABSTRACT FROM AUTHOR]

The simplified method of arch bridge suspender replacement scheme based on the measured displacement correction is proposed in order to ensure the safety of the arch bridge suspender replacement process based on the pocket hanging method. Firstly, each group of replacement suspenders is separated from the pocket hanging system regardless of the constraint effect of the bridge deck on the suspenders, and the force analysis is carried out to obtain the displacement of the bridge deck under different cases; Then, the modified coefficient is obtained by using the measured displacement at the lower end of each suspender, and the modified coefficient is used to modify the displacement of the bridge deck, so that the calculation result can be applied to the case where the stiffness of the bridge deck cannot be ignored; Finally, the correctness of the method in this paper is verified by applying it to practical engineering. It can be concluded that the proposed method is simple, easy to operate and has high precision, which can be used in the removal of arch bridge suspenders through the verification results.

Introduction. When operating high-precision measurement setups, the reliability of measurements needs to be guaranteed. The displacement of elements from the measurement path can lead to a distortion of measurement results, especially in measurement setups operating in the microwave range. In order to ensure measurement reliability, the positions of elements in the measurement setup needs to be monitored. The monitoring should be performed during the measurement. The control device, which should be connected to the automatic control system of the measurement setup, should neither mechanically affect the setup elements nor introduce any interference. Currently used control systems for the technical characteristics do not meet the necessary requirements.Objective. To design a control system which allows for the monitoring of displacements of elements in a high precision measuring setup with an accuracy of 1.0 · 10 4 mm and digital signal processing. The control system thus designed should neither mechanically affect the controlled elements nor introduce electrical and electromagnetic interferences.Materials and methods. The system thus designed utilises optical methods for displacement monitoring based on the principles of geometric optics. Mathematical modelling (Mathcad) methods were used to determine the reaction of the system to changes in the beam trajectory and to estimate the sensitivity of the optical control system. Charge-coupled devices (CCD) were used to record the system response to optical path changes.Results. The study presents two designs of a control system for the displacement monitoring of high precision measurement setup elements. The first system design allows for the detection of the occurrence of displacement, while the second system design allows for the identification of the displaced element. The system is capable of registering displacements of elements up to an accuracy of 1.0 · 10 4 mm and monitoring the position of elements while exposed to vibration. The system does not mechanically or electromagnetically affect the controlled elements. All system elements are resistant to microwave radiation and increased background radiation, excluding the CCD which needs to be placed outside the active zone. The monitoring system for movements of elements in the high-precision measuring setup allows for digital signal processing. The study proposes a method to increase system accuracy.Conclusion. The system can be used in setups with increased microwave, x-ray and radiation emission. In comparison with systems based on other physical principles (inductive, capacitive and rheostat), the system thus developed is much easier to implement.

The strengthening and retrofitting of concrete structures are becoming an essential part of the building and its structures. When the building comes of age, there is a need to increase the structural members' strength, life, and resistivity against unfavorable environmental conditions. In the current scenario, ferrocement composites are used for structural strengthening and rehabilitation. Therefore, an experimental investigation is needed to evaluate the effectiveness of the strengthening on the square and circular reinforced concrete columns by ferrocement and micro concrete materials. The experimental results showed that the ferrocement and micro concrete techniques enhanced the stress-strain behavior and displacement limit of the square and circular RC column. The strengthening circular RC column by micro concrete gives a better performance in stress-strain behavior and displacement limit. In addition, the ferrocement and micro concrete strengthening technique is a promising and economical alternative compared to the other strengthening techniques. Also, test results were compared with ACI and CNR-DT representative load-carrying models to verify each model's reliability and accuracy. Furthermore, the TOPSIS method was adopted to find out the best solution for square and circular columns, and cost analysis was carried out. [ABSTRACT FROM AUTHOR]

In this paper, we study the problem of boundary control of string oscillations, which is carried out over a period of time less than the critical time. The control is performed by a displacement of one end of the string, whereas at the other end a uniform boundary condition with oblique derivative is given, and the direction of this derivative does not coincide with characteristics. The classical statement of the problem is considered. Necessary and sufficient conditions for the existence of a unique control are found, and the control itself is obtained in an explicit analytical form. [ABSTRACT FROM AUTHOR]

To reduce the effect of nonlinear factors and improve the tracking accuracy of the control system, a controller based on feedback linearization sliding mode control (FLSMC) method is proposed. This paper takes a variable displacement pump driven by a constant speed motor as the research object to verify the effectiveness of the designed controller. First, a high-order nonlinear model of the variable pump displacement control mechanism is established. Meanwhile, the load characteristic of the control cylinder is obtained by analyzing the swashplate control moment. Then the author uses the feedback linearization method to linearize the system model and designs a sliding mode controller to eliminate the impact of load parameter changes. Finally, the proposed FLSMC controller is used in simulation and experiment, and the PID controller is used as a comparison. Results show that the FLSMC controller can effectively improve the robustness of the pump control system. [ABSTRACT FROM AUTHOR]

Rate‐independent linear damping (RILD), which is also known as structural damping or hysteretic damping, refers to a type of damping having a constant imaginary part in its complex stiffness that generates damping forces independent of the excitation frequency. In contrast, linear viscous damping (LVD) is another type of damping with a frequency‐proportional imaginary part in its complex stiffness, resulting in damping forces proportional to frequency. RILD demonstrates similar performance to that of LVD for the same loss factor when incorporated in a structure to control seismic response displacement. Nevertheless, the damping force generated by the RILD is relatively low in frequency ranges higher than the natural frequency of the primary structure. This leads to efficient displacement control with low damping force when RILD is integrated with low‐frequency structures. However, the noncausality of RILD hinders its practical applications, and thus, causal models are widely studied to mimic the RILD behavior. This paper proposes a causal model of RILD using Maxwell elements whose damping force is generated according to the fractional derivative of displacement. The proposed model, further represented by a fractional‐order damping function, is found to be a unifying model that includes existing causal RILD models from the literature, thereby providing further insights to better understand the nature of RILD. Furthermore, numerical examples using linear as well as nonlinear structural models illustrate the benefit of physical realization of the proposed methods in improving the seismic performance of low‐frequency structures. [ABSTRACT FROM AUTHOR]

The electrohydraulic equipment of the coal gangue belt conveyor has been widely studied in recent years, but studies have been limited to the traditional hydraulic system with proportional valve and servo valve as control elements. Because of their own structural characteristics, proportional valves and servo valves have inherent defects such as low reliability, high cost and a long debugging cycle. It is necessary to carry out technological innovation and upgrading. This paper presents a hydraulic system scheme which uses digital valves instead of proportional valves and servo valves to control the belt conveyor propulsion system. Firstly, the system scheme is described in detail. Secondly, the simulation model of the control element digital valve is established, and its dynamic characteristics are analyzed in detail. Finally, the displacement tracking control of the new system is carried out to verify the feasibility of the proposed control scheme. The results show that the new digital hydraulic control system can effectively achieve the displacement control function of the belt conveyor propulsion system.

When natural disasters occur, real-time disaster relief operations need to be implemented. But if disaster relief transportation is interrupted, these operations will be severely hampered. Emergency relief bridges must be erected so that people, materials and machinery can reach the disaster area smoothly. Therefore, one indispensable tool of disaster relief organizations is the light bridge. The design of such a lightweight bridge is controlled by deformation, not strength, so the span of the bridge is limited. Thus, this study proposes a bridge with multiple NEMs acting as multiple virtual piers of the bridge and an active structural control method was adopted to expand the span of the light bridge. The experimental results showed that, for the maximum vertical displacements at 1/3 and 2/3 distances from the left side of the bridge under uncontrolled and controlled conditions, the displacement reduction rates of the bridge were 96.20% and 98.42% for the outbound trip and 93.32% and 98.47% for the return trip, respectively. For the displacement control at the midpoint of the bridge under uncontrolled and controlled conditions, the displacement reduction rates of the outbound and return trips were 96.77% and 96.62%, respectively. The images from the experiment also showed that the cantilever arm of each NEM could be rotated by the PID controller to the appropriate angle to provide sufficient upward force to balance the vertical displacement changes based on the position of the moving load. Thus, zero-displacement control of a bridge can be achieved, and the control effect is quite significant. [ABSTRACT FROM AUTHOR]

Based on the converse flexoelectric effect, flexoelectric actuator is designed and used to control the dynamic displacement of cantilever beams. First, shell-type stress expression based on double-curvature shell induced by the converse flexoelectric effect is developed, which can be simplified to a flexoelectric-laminated cantilever beam by applying two Lamé parameters and beam radius of curvature. Then, the flexoelectric actuator is designed with a conductive atomic force microscope probe and a flexoelectric layer. An inhomogeneous electric field is generated when the external voltage is applied on the atomic force microscope probe and the flexoelectric layer, which leads to stress in the longitudinal direction of beam and control moment. With the flexoelectric-induced bending moment, displacement induced by the external force and flexoelectric actuator is derived. The displacement is related to many parameters, such as actuation voltage, atomic force microscope probe radius and flexoelectric layer thickness. Cases are studied to optimize the control effect with different parameters. Results show that vibration control effect is enhanced with a higher actuation voltage and a smaller atomic force microscope probe radius for each mode. Besides, the thicker flexoelectric layer enhances the control effect with a larger bending moment arm for each mode. Dynamic vibration is controlled effectively by converse flexoelectric effect. [ABSTRACT FROM AUTHOR]

Snap-through phenomenon widely occurs for elastic systems, where the systems lose stability at critical points. Here snap-through of an elastica under bilateral displacement control at a material point is studied, by regarding the whole elastica as two components, i.e., pinned-clamped elasticas. Specifically, stiffness−curvature curves of two pinned-clamped elasticas are firstly efficiently located based on the second-order mode, which are used to determine the shapes of two components. Similar transformations are used to assemble two components together to form the whole elastica, which reveals four kinds of shapes. One advantage of this way compared with other methods such as the shooting method is that multiple coexisting solutions can be located accurately. On the load−deflection curves, four branches correspond to four kinds of shapes and first two branches are symmetrical to the last two branches relative to the original point. For the bilateral displacement control, the critical points can only appear at saddle-node bifurcations, which is different to that for the unilateral displacement control. Specifically, one critical point is found on the first branch and two critical points are found on the secondary branch. In addition, the snap-through among different branches can be well explained with these critical points. [ABSTRACT FROM AUTHOR]

Quasi-static peeling of a horizontal elastica (the tape) from another horizontal elastica (the beam) supported by a pinned end and a roller end is analyzed. Bending resistance is assumed to dominate the behavior, and large deflections and rotations are allowed. The tape is shorter than the beam and is pulled upward at a constant angle with the horizontal. A transversality (debonding) condition is derived for peeling, based on the common fracture mechanics approach. Displacement control is considered. The associated force exhibits its peak value at the onset of peeling. The vertical deflection of the pulled end of the tape also is of interest, especially when the tape detaches from the beam. Equilibrium curves are determined, and the effects of the following parameters on the peak force and the detachment deflection are investigated: the relative thicknesses and moduli of elasticity of the tape and the beam; the relative lengths of the tape and the beam; the angle of pulling; and the nondimensional work of adhesion. The system may be used as a model of peeling bandages, medical patches, biosensors, and other wearable devices from skin. Other possible thin flexible substrates include fabric, paper, leather, rubber, and plastics. [ABSTRACT FROM AUTHOR]

As wind turbines become larger and move into deeper sea, their operating environment worsen. The torque fluctuation inside the drive chain is aggravated, which leads to the premature failure of the wind turbines. To improve the transmission stability of wind turbines, the mechanical-hydraulic hybrid transmission system (MHHTS) has been applied. However, existing research has issues with structure and hydraulic control. An MHHTS structure was proposed to meet the requirements of structural simplicity and high efficiency, corresponding to the design principles summarized in the article. Based on this structure, we have selected a hydraulic control mode, the constant displacement pump variable displacement motor (CPVM), that satisfies the reasonable utilization of displacement and the stability of control. This mode was chosen by comparing the displacement and pressure variation rules of three hydraulic control modes that meet the maximum power point tracking (MPPT) control principle of the wind turbine. In this study a co-simulation model of a 10 MW MHHTS wind turbine was built using Simulink and AMEsim. The correctness of the structural and control mode ware verified by co-simulation with a uniformly varying wind. Moreover, a method that can suppress fluctuations in output power by controlling the motor displacement was proposed. Different-step winds response analyses were conducted to explore the relationship between the displacement response speed and the output power fluctuations. The non-linear relationship between the displacement and the wind speed can also have an impact on the previous relationship. Finally, the feasibility of the control method was verified through simulation of an actual turbulent wind. These achievements should guarantee the future application of the novel transmission system in wind turbines. [ABSTRACT FROM AUTHOR]

Because of the design and construction requirements, the nuclear structures need to maintain the structural integrity under both design state and extreme earthquake shaking. The base-isolation technology can significantly reduce the damages of structures under extreme earthquake events, and effectively protect the safeties of structures and internal equipment. This study proposes a base-isolation design for the AP1000 nuclear shield building on considering the performance requirements of the seismic isolation systems and devices of shield building. The seismic responses of isolated and nonisolated shield buildings subjected to design basis earthquake (DBE) shaking and beyond-design basis earthquake (BDBE) shaking are analyzed, and three different strategies for controlling the displacements subjected to BDBE shaking are performed. By comparing with nonisolated shield buildings, the floor acceleration spectra of isolated shield buildings, relative displacement, and base shear force are significantly reduced in high-frequency region. The results demonstrate that the base-isolation technology is an effective approach to maintain the structural integrity which subjected to both DBE and BDBE shaking. A displacement control design for isolation layers subjected to BDBE shaking, which adopts fluid dampers for controlling the horizontal displacement of isolation layer is developed. The effectiveness of this simple method is verified through numerical analysis.

Numerical simulation of a progressive collapse of structures using computer has a very actual apprehension for structural engineers due to their interest in structures veracity estimation. This simulation helps engineers to develop methods for increasing or decreasing the progressive failure. Finite Element Method (FEM) is the most computer simulation analysis currently used to perform a structural vulnerability assessment. Unfortunately, FEM is not able to automatically analyze a structure after element separation and collision which has a great effect on a structure’s performance during collapse. For instances, a bombing load can cause damage to a main supporting column in a structure, which will cause debris flying at a very high velocity from the damaged column. This debris can cause another local failure in another column upon impact and lead to the progressive collapse of the whole structure. A new simulation technique, which was developed in 1995 as part of Tagel-Din’s doctoral research, called Applied Element Method (AEM) can simulate the structure’s behaviour from zero loading until collapse, through the elastic phase, opening and propagation of cracks, yielding of reinforcement bars and separation and collision of elements. This method is used in Extreme Loading for Structures software (ELS) by Applied Science International (ASI). In the current paper, a brief description of the AEM is given. Also, numerical modelling based on two experimental studies available in the literature conducted by Ahmadi et al. and Yi et al. are generated using ELS. These models are used to confirm the capability of AEM in simulation the progressive collapse behaviour of structures. Also, the models are utilized to examine and measure the structural resisting mechanisms of reinforced concrete structures against progressive collapse. The obtained numerical results indicated that, ELS can accurately model all structural behaviour stages up to collapse. A better agreement between the experimental and numerical results is observed. Moreover, the results obtained with ELS indicated an enhanced agreement with other software packages such as; OpenSees, Ansys, Abacus, and MSC Marc.

For a structure under service loads, there is a need to induce precise control of a local displacement by additional punch loading. Such problem exists in design of robot grippers or agricultural tools used in mechanical processing. The punch interaction is assumed to be executed by a discrete set of pins or by a continuously distributed contact pressure. The optimal contact force or pressure distribution and contact shape are specified for both discrete and continuous punch action. Several boundary support conditions are discussed, and their effects on punch action are presented. [ABSTRACT FROM AUTHOR]