Semi-active Devices Research Articles

Physical modeling and experimental verification of magneto-rheological damper under medium and high frequency excitation

As a promising semi-active device, magneto-rheological damper has been widely used in low-frequency vibration isolation fields (within 20 Hz) such as bridge damping and building seismic resistance. Recently, the application of magneto-rheological damper has extended to medium and high frequency fields such as satellite and power engine vibration control, accompanied with an urgent need of detailed understanding of its output characteristics. In this paper, a comprehensive physical model is established to analyze dynamic performance of the magneto-rheological damper. The model, derived from both Poiseuille and Couette flow, aims to describe the relationship between the flow rate and pressure difference. The compressibility of the magneto-rheological fluid, the inertia of both the fluid and piston assembly, and the friction are involved to capture the medium and high frequency dynamics of the damping force. Theoretical calculation and simulation verification of magnetic circuit are conducted. Then the experiment based on a self-made prototype is carried out. The results show that the damping force calculated by proposed physical model matches well with the experimental results across the predefined range of frequency and coil current levels.

A controllable mechanical motion rectifier-based semi-active magnetorheological inerter for vibration control

The conventional semi-active variable damping (VD) device can only dissipate the vibration energy, which inherently limits its performance in vibration control. This paper proposes a novel semi-active inerter concept and develops a prototype with magnetorheological (MR) dampers, which can store the vibration energy in a flywheel and then release it to suppress vibration. The new idea is inspired by a variable inertance (VI) device, which has a VD device and a passive inerter in serial, and a passive mechanical motion rectifier (MMR), which can convert the reciprocating input into a unidirectional output. The controllable MMR (CMMR) applies two VD devices to replace the two one-way roller clutches in the MMR. By equipping the CMMR, the semi-active inerter gets more controllability than the original VI device because it can switch the torque and motion transmitting routes between the device terminals and the flywheel in it. The frequency-domain analysis validates the versatile of the semi-active inerter, which can work in VD and VI modes. The test results of the semi-active MR inerter prototype are used to identify the device parameters, which are applied for the control simulation. The semi-active MR inerter in CMMR mode has the best torque tracking performance with a given test condition, and it has a 20.13% improvement than in the VD mode. Then, a seat suspension with the semi-active MR inerter is applied to validate the effectiveness of the device in vibration control. The results show that the vibration reduction of the seat suspension in the CMMR mode is 39.3% higher than in the VD mode, which indicates a significant improvement of ride comfort. The new concept of the semi-active device has excellent potential in vibration control and is promising in practical applications.

Automated synthesis of controlled cable-stayed footbridges with S-shaped deck

Curved cable-stayed bridges (CSB) have been increasingly used in the past years. There are currently 42 operational CSB registered in the Structurae database, 37 of which have been built in the last two decades. The minimum cost design of curved S-Shaped pedestrian CSB with external pylons satisfying the static and dynamic code requirements (Eurocodes and Setra guidelines in this work) are found by using an optimization algorithm with polynomial convergence time. Dampers cannot be located at the pylon-deck connection because it does not exists, the structure being controlled by passive and semi-active tuned mass dampers. The sensitivity analysis considers the non-linear dynamic behaviour of the semi-active device. Two optimal solutions are sought using semi-active (S1) and passive (S2) dampers. The results show that both solutions have different geometries and cross sections. The pylon height is markedly higher for structure S2 because this improves the dynamic behaviour of the bridge. The results reveal that the pylon acts like a dynamic leverage arm magnifying the vertical response of the deck. Better results are obtained from performing structural-optimization and determination of control procedure simultaneously rather than separately.

Semi-Active Magnetorheological Damper Device for Chatter Mitigation during Milling of Thin-Floor Components

The productivity during the machining of thin-floor components is limited due to unstable vibrations, which lead to poor surface quality and part rejection at the last stage of the manufacturing process. In this article, a semi-active magnetorheological damper device is designed in order to suppress chatter conditions during the milling operations of thin-floor components. To validate the performance of the magnetorheological (MR) damper device, a 1 degree of freedom experimental setup was designed to mimic the machining of thin-floor components and then, the stability boundaries were computed using the Enhance Multistage Homotopy Perturbation Method (EMHPM) together with a novel cutting force model in which the bull-nose end mill is discretized in disks. It was found that the predicted EMHPM stability lobes of the cantilever beam closely follow experimental data. The end of the paper shows that the usage of the MR damper device modifies the stability boundaries with a productivity increase by a factor of at least 3.

NHERI Lehigh Experimental Facility With Large-Scale Multi-Directional Hybrid Simulation Testing Capabilities

The NHERI Lehigh Experimental Facility, as part of the NSF funded Natural Hazards Engineering Research Infrastructure (NHERI) site, was established in 2016 as an open-access facility. This facility enables researchers to conduct state-of-art research on natural hazard mitigation in civil infrastructure systems, including high performance numerical and physical testing to improve the resilience and sustainability of the civil infrastructure against natural hazards. The facility has the unique ability to conduct real-time multi-directional hybrid simulation (RTHS) on large-scale structural systems using 3D nonlinear numerical models combined with large-scale physical models of structural and non-structural components. The Lehigh Experimental Facility processes testbeds that include a testbed for testing lateral load resisting system characterization testbed, a non-structural component multi-directional dynamic loading simulator, full-scale and reduced-scale damper testbeds, a tsunami and storm surge debris impact force testbed, and a soil-foundation structure interaction testbed. This paper describes the infrastructure and capabilities of the NHERI Lehigh Experimental Facility. Developments by the facility in advancing large-scale RTHS are given. Examples of research projects performed by users of the facility are then provided, including large-scale RTHS of steel frame buildings with magneto-rheological (MR) dampers and nonlinear viscous dampers subject to strong earthquake ground motions; 3D multi-hazard large-scale RTHS of tall steel buildings subject to multi-directional wind and earthquake ground motions; characterization of a novel semi-active friction device based on band brake technology; and testing of cross-laminated timber self-centering coupled wall-floor diaphragm-gravity systems involving multi-directional loading.

Internal magnetic field tests and magnetic field coupling model of a three-coil magnetorheological damper

Magnetorheological damper is a typical semi-active control device. Its output damping force varies with the internal magnetic field, which is a key factor affecting the dynamic performance of the magnetorheological dampers. Existing studies about the magnetic field of magnetorheological dampers are limited to theoretical analysis; thus, this study aims to experimentally explore the complicated magnetic field distribution inside the magnetorheological dampers with multiple coils. First, the magnetic circuit of a three-coil magnetorheological damper was theoretically analyzed and designed, and the finite element model of the three-coil magnetorheological damper was set up to calculate the magnetic induction intensities of the damping gaps in different currents and numbers of coil turns. A three-coil magnetorheological damper embedded with a Hall sensor was then manufactured based on the theoretical and finite element analysis, and internal magnetic field tests under different conditions were carried out to obtain the actual magnetic induction intensities. At last, the magnetic field coupling model of the three-coil magnetorheological damper was proposed by introducing a coupling coefficient to describe the complex magnetic field distribution due to the strong coupling effect of the three coils, and the results calculated by the proposed model agreed well with the finite element analysis and magnetic field test data. The proposed model lays a foundation for the optimal design of the magnetic circuit and the mathematical model of multi-coil magnetorheological dampers.

Iterative learning from suppressing vibrations in construction machinery using magnetorheological dampers

The aim of the paper is to propose algorithms for suppressing vibrations of massive components of machinery, e.g., operators' cabins in bucket wheel excavators (BWEs). Repetitive perturbations provide the opportunity to learn a control system to suppress or reduce their influence by applying a repetitive control scheme. A new version of the iterative learning control approach, called iterative learning of optimal control (ILOC), is derived. This approach is able to learn a control signal that approximately minimizes the squared acceleration of a system, e.g., the cabin. The resulting algorithms can be used alone or in parallel with a hybrid version of the classic proportional-derivative (PD) controller. The simulations indicate that the ILOC algorithm provides a large improvement in suppressing quasi-periodic disturbances in comparison to the cases of no control and PD control, while the hybrid version provides even slightly better results.The proposed algorithms are intended to be used with magneto-rheological (MR) dampers as semi-active control devices. Subtle properties of MR dampers, such as their hysteresis, are omitted here.

Development of Seismic Response Simulation Model for Building Structures with Semi-Active Control Devices Using Recurrent Neural Network

A structural analysis model to represent the dynamic behavior of building structure is required to develop a semi-active seismic response control system. Although the finite element method (FEM) is the most widely used method for seismic response analysis, when the FEM is applied to the dynamic analysis of building structures with nonlinear semi-active control devices, the computational effort required for the simulation for optimal design of the semi-active control system can be considerable. To solve this problem, this paper used recurrent neural network (RNN) to make a time history response simulation model for building structures with a semi-active control system. Example structures were selected of an 11-story building structure with a semi-active tuned mass damper (TMD), and a 27-story building having a semi-active mid-story isolation system. A magnetorheological damper was used as the semi-active control device. Five historical earthquakes and five artificial ground motions were used as ground excitations to train the RNN model. Two artificial ground motions and one historical earthquake, which were not used for training, were used to verify the developed the RNN model. Compared to the FEM model, the developed RNN model could effectively provide very accurate seismic responses, with significantly reduced computational cost.

Estimation of Knee Angles Based on Thigh Motion: A Functional Approach and Implications for High-Level Controlling of Active Prosthetic Knees

Human locomotion is the result of complex neuromusculoskeletal cooperation between different joints and limbs of the lower extremities. This collaboration (also called synergy [1]) results in an energyefficient gait. Unfortunately, for an above-knee amputee, this cooperation is lost since current prosthetic devices do not emulate the missing functionality in a manner similar to their biological counterparts. Transfemoral amputees can select between passive (Mauch knee [2]), semi-active (Ottobock's C-leg [3] and Ossur's rheo knee [4]), and active prosthetic devices (Ossur's power knee [5]). What distinguishes the active ones from the other two is the injection of positive power for activities such as ascending stairs and standing up from a chair.

An Electromagnetic Variable Stiffness Device for Semiactive Seat Suspension Vibration Control

This article introduces a rotary semiactive variable stiffness (VS) device, including its system design and model validation. A variable damping (VD) device and springs can form mechanical networks with specific topologies, and the VD device can control the equivalent stiffness of the network by varying its damping. The proposed rotary electromagnetic VS device consists of an electromagnetic VD device and a torsion spring, which are in series, while a planetary gear reducer is used to amplify the torque output of the VS device. The models of the electromagnetic VD and VS devices are both built and validated with tests. Then, a seat suspension applies the VS device by installing the device in the center of its scissors structure. Bump and random vibration experiments are implemented to validate the effectiveness of the proposed VS system for seat suspension vibration control. The new system has merits in controllability and energy efficiency. It is easier to design the controller than the conventional one with magnetorheological damper due to the linear damping of the electromagnetic VD device. Besides, the system energy consumption is low and has energy harvesting capability. The proposed semiactive electromagnetic VS device also has potential in other practical applicationss.

An innovative adaptive tuned vibration absorber with variable mass moment of inertia for mitigation of transient response of systems

An innovative semiactive device, named the spindle adaptive tuned vibration absorber (SATVA), is proposed herein, having the potential of attenuating unfavorable vibrations of the host systems. The proposed device includes a preferably spindle-shaped body of mass, whose mass moment of inertia can be altered simply by moving a pair of rotating supports. Therefore, the natural frequency of the device can be altered with a fairly low power consumption. A comprehensive analytical approach is employed in order to derive the governing equations of motion of the device, considering physical and practical issues. Through a numerical case study, it is demonstrated that the device is capable of reducing unfavorable vibrations of a rotating machinery during start-up, while requiring considerably less amount of physical mass, compared with conventional absorbers. In addition, the spindle adaptive tuned vibration absorber has a quite rapid adaptation mechanism in comparison with other adaptive-mass tuned vibration absorbers. Provided that its absolute acceleration during operation can be kept within reasonable limits to prevent slipping, this device is capable of finding different applications in various engineering disciplines.

Surrogate models for high performance control systems in wind-excited tall buildings

High-performance control systems (HPCSs), including active, semi-active, and hybrid systems, have been demonstrated as promising methods to mitigate a variety of excitations. However, their deployment in the field is still very limited, attributable to reliability concerns in the closed loop configuration. A solution to promote their applicability is the development of an uncertainty-based design procedure, but such solution comes at a high computational cost due to the large number of possible scenarios to consider on both the closed-loop configuration and external load sides. To alleviate the computational demand of such analysis, this paper investigates the use of data-driven surrogate assisted techniques for uncertainty quantification of HPCSs deployed in wind-excited tall buildings. Both a Kriging surrogate and an adaptive wavelet network (AWN) are investigated and compared to map the unknown relationship between structural inputs and responses. The Kriging model exploits an offline batch learning process while the AWN uses an online sequential process. The surrogate models are applied to a 39-story building equipped with semi-active friction devices exposed to wind load and are compared in terms of accuracy and computational time. Two applications of the surrogate models for uncertainty analysis of the case study building are presented. One is for uncertainty quantification and the other for identification of the most influential uncertain variables. Results show that Kriging provides a more accurate representation to map uncertainties to the system response and to quantify the uncertain performance of HPCSs, but that the AWN provides a significantly faster computational alternative. In particular, for a case containing 17 uncertain variables, Kriging found a representation in 3h20, while the AWN converged in 37 min. Under 41 uncertain variables, these metrics increased to 16h20 and 3h22 for Kriging and the AWN, respectively. These representations were leveraged to identify and remove the uncertainties from three key variables yielding high variance in structural response. Results showed that variables identified under Kriging yielded a 34.9% decrease in variance under 17 uncertain inputs and a 22.9% decrease in variance under 41 uncertain inputs, while AWN yielded a 29.0% and 19.8% decrease, respectively.

Semi-active vibration control of structural systems based on linear approximation of switched linear system

For vibration control of structural system, semi-active control is expected to show better performance than other control methods in terms of energy efficiency. However, because of the energy dissipation characteristics of the semi-active control devices, the mathematical model of the semi-active control system becomes a hybrid model. Optimal control of hybrid models can be solved by mixed integer quadratic programming. However, this method is computationally expensive because the optimization problem must be solved for every sampling instant. One such computationally inexpensive method is clipped-optimal control, but its performance is not guaranteed because it does not consider the constraints of energy dissipation of the semi-active device. The clipped-optimal control can be expressed as a switching system of three systems under the influence of energy dissipation constraints. In a 1-DOF (degree of freedom) system, the switching conditions of the three systems can be expressed as angles on a phase plane. The 1-DOF vibration system draws an ellipse in the forced vibration and a spiral in an initial response on the phase plane. In the case of a vibration system that draws a circle-like trajectory on the phase plane, unlike other switching systems, the selection of these three systems is performed at a substantially constant rate. In this study, we propose a semi-active control method using a single linear system composed of the above three systems. The linear systems are referred to as the averaged systems in the study. We propose a method to systematically design the clipped-optimal control, which has been conventionally designed by trial and error, with the averaged system. Simulation studies show the effectiveness of the proposed semi-active control approach.

Robotic-Assisted Pedicle Screw Placement During Spine Surgery.

The robotic guidance system consists of a bed-mounted surgical arm and a workstation. We used the Mazor X Stealth Edition Robotic Guidance System by Medtronic for spine surgery, which has been previously described2-5. Unlike other systems that are navigation-based and require an optical tracking mechanism, this system relies on the preoperative plan to be referenced using the intraoperative registration. The workstation runs an interface software that facilitates preoperative planning, intraoperative image acquisition and registration, kinematic calculations, and real-time robot motion control. The robotic arm is mounted onto the bed as well as rigidly attached to the patient's spine. It can move in 6 degrees of freedom to provide the preplanned screw trajectory and entry point thereby allowing the surgeon to manually perform the drilling and screw insertion through either an open or percutaneous procedure by first seating a drill tube and then drilling and tapping the hole as needed. Other robotic systems include the ROSA robot by Medtech, the ExcelsiusGPS robot by Globus Medical, and the SurgiBot and ALF-X Surgical Robotic systems (both from TransEnterix). The Da Vinci Surgical System (Intuitive Surgical) has been utilized for laparoscopic anterior lumbar interbody fusion (ALIF), but it has not been approved by the U.S. Food and Drug Administration for actual spinal instrumentation. Alternative surgical techniques for pedicle screw placement include the freehand fluoroscopy-guided technique and intraoperative image-assisted computer navigation techniques, including isocentric C-arm (Iso-C) 3D (3-dimensional) navigation (Siemens), computed tomography (CT) navigation, O-arm navigation (Medtronic), CT-magnetic resonance imaging co-registration technology, and a 3D-visual guidance technique6-8. The robotic-guided pedicle screw placement offers the following benefits over conventional dorsal instrumentation techniques: improved accuracy and safety in pedicle screw insertion2-4,9-13; precision in screw size selection and planned screw positioning2; a reduction in exposure to radiation for the surgeon, the patient, and the operating-room staff9,11,12,14-19; simplicity and user-friendliness with a moderate learning curve10,11,20,21; ease of registration and reduction of operating time2; significant enhancement of the surgeon's ergonomics and dexterity for repetitive tasks in pedicle screw placement15,22-24; and a wider coverage in function to include utilization during minimally invasive surgery where applicable11,25. Accuracy rates between 94.5% and 99%, comparable with those in our study10, have been reported with the robotic-guided pedicle screw insertion technique, even in studies involving complex deformities and revision surgeries for congenital malformations, degenerative disorders, destructive tumors, and trauma2-4,9-13. The safety of this technique, in terms of reduced complications and intraoperative radiation exposure, has also been documented as higher than that for freehand fluoroscopic guidance or other navigation techniques9,11,12,14-19. The feasibility of this procedure has been further extended to minimally invasive procedures and to use in the cervical region, with replication of its advantages. It is associated with a reasonable learning curve, with consistent successful results after 25 to 30 patients. The principles of robotic-guided pedicle screw placement are similar irrespective of the system used.Although initially utilized mainly for thoracolumbar pedicle screw insertion, the latest robots and software have been adapted for use in the cervical spine with equivalent efficiency and accuracy.Robotic guidance can be employed in non-pedicle-screw-insertion procedures.Challenges include radiation exposure, trajectory failure, equipment and software failure, failed registration, logistics, time, and high cost.

Application of the resettable semi-active damper device for macro modelling of confined semi-interlocking masonry walls

In previous research by the authors, the semi-interlocking masonry (SIM) was investigated as infill panels for framed structures and its favourable seismic performance was established through laboratory tests. Confined semi-interlocking masonry (CSIM) is a new application of SIM that aims to enhance earthquake performance of confined masonry buildings. Numerical simulations are performed to estimate the structural capacity of CSIM buildings. Micro and macro-modelling strategies are two major approaches for numerical simulation of masonry buildings. This paper proposes a macro-model for CSIM buildings by using a resettable semi-active damper model to simulate the behaviour of the SIM panel. The hysteretic performance of CSIM walls using the proposed macro-model was compared with the load-displacement pushover curve resulting from the FEA micro-modelling approach. The acceptable match between the responses of CSIM walls obtained from the micro and the macro-model confirmed the capability of the proposed model to capture the capacity of CSIM walls.

The variable resonance magnetorheological pendulum tuned mass damper: Mathematical modelling and seismic experimental studies

Tuned mass damper technologies are progressively advancing through innovative application of smart materials, facilitating more versatile infrastructure protection. During seismic events, primarily encountered surrounding fault lines, high-rise buildings and other civil structures can suffer catastrophic failures if not adequately protected. Where traditional passive structural protection may mitigate such damage, adaptive systems which provide controllable vibration attenuation across a wide range of excitation frequencies have seen growth in use, overcoming the challenges resulting from unpredictable seismic spectrums. As a robust solution to this problem, this article presents and analyses a variable resonance magnetorheological-fluid-based pendulum tuned mass damper which employs a rotary magnetorheological damper in a controllable differential transmission to add stiffness to a swinging pendulum mass. The device is mathematically modelled based on magnetic field analysis, the Bingham plastic shear-stress model for magnetorheological fluids, and planetary gearbox kinematic and torque relationships, with the model then being validated against experimental data. The passive and semi-active-controlled performance of the device in seismic vibration suppression is then experimentally investigated using a scale five-storey building. In tests conducted with the 1985 Mexico City record, the semi-active device outperformed the (optimal) passive-on tuning, at best reducing peak displacement by 15.47% and acceleration by 28.28%, with similar improvement seen against the passive-off case for the 1940 El Centro record.

Further steps towards the tuning of inertial controllers for broadband‐frequency‐varying structures

There is a large number of slender structures which are prone to vibrate due to pedestrian loads. The well-known Tuned Mass Damper (TMD) is increasingly used in practice, but this device may detune under several circumstances drastically reducing its expected performance. A Semi-active TMD (STMD) provides more robustness under structure uncertainties than the passive one and may be recommended for use when several vibration modes are in the excitation range and/or when the mode to cancel has uncertainty or varies over time. The tuning of the semi-active device for these cases cannot be the same as the passive one. This paper presents a methodology for the tuning of an STMD under broad frequency-band uncertainties using an ON/OFF phase control law. This control law is experimentally implemented considering interesting practical aspects, such as the estimation of the inertial mass velocity from the measured acceleration, or a low-pass filter to avoid unnecessary control actions, among others. An optimization process using a proposed performance index is carried out. Thus, it has been demonstrated that the optimal STMD is achieved for much lower damping and higher tuned frequency than the passive one. Finally, the proposed methodology is validated with experimental results.

STUDY ON SEDIMENTATION STABILITY OF MAHUA AND SIMAROUBA OIL BASED MAGNETORHEOLOGICAL FLUIDS

Magnetorheological fluids (MRFs) are peculiar of smart fluids whose rheological properties can be efficiently controlled by varying applied magnetic field. Owing to this peculiar property, it can be utilized in industrial applications in semi-active devices such as dampers, actuators, etc. In this work, an effort has been attempted to produce MRFs using natural oils as carrier fluids and tested for potential replacement of conventional carrier fluids such as silicone oil. The MR fluids are prepared using silicone oil and two natural oil namely Mahua oil and Simarouba oil. Carbonyl iron (CI) and Electrolytic iron (EI) are used as suspended particles with lithium grease as an additive. The MRF using two natural based oil are known as Green magneto rheological fluids (GMRF). The characterization of suspended particles and carrier liquids was performed, followed by tests on sedimentation stability of prepared samples. To compare the sedimentation stability, the graphs of sedimentation ratio versus time are plotted for all MR fluids samples. It is found that the sedimentation stability of natural oils based MRFs are relatively better than silicone oil based MRFs for the same concentration of magnetic particles. There is potential of these natural oils based MRFs to replace the conventional MRFs However, other rheological properties like yield strength, flow characteristics etc. needs further investigation.

Design of a magnetically sensitive monotube damper for leg prostheses applying magnetic materials

In this article, application of smart fluids in the design of a magnetorheological damper is presented, which consists of a semi-active suspension device whose operation is through a magnetorheological fluid to allow infinitely variable damping force control in real time over a wide range and low power requirements. The damper design presented in this investigation operates in valve and sheave modes. In addition, the properties of the materials were considered giving emphasis to the magnetic permeability. By means of the magnetic method of finite elements (FEMM), simulations were performed for the magnetic field analysis that occurs in the three coils. For the construction of the MR buffer, it was done in accordance with the results of the finite element simulation (FEA). It was implemented in a prototype of transfemoral prosthesis.

Asymmetric Dynamic Model of Temperature-Dependent Magnetorheological Damper and Application for Semi-active System

As semi-active hydraulic device, magnetorheological (MR) damper’s damping characteristics will be influenced by temperature. In addition, the MR damper with gas accumulator usually shows asymmetric loop characteristics. To capture the hysteretic characteristics of MR dampers accurately, a developed model considering the temperature effects and asymmetric characteristics is proposed and analyzed. A typical mono-tube MR damper with gas accumulator is designed and tested under different sinusoidal excitations, currents and temperatures for obtaining the temperature-dependent and asymmetric damping characteristics. Based on experimental results, the proposed asymmetric model and conventional symmetric model are compared. The accurately asymmetric model is identified to calculated coefficients about current and temperature. The MR systems with symmetric model considering temperature effects, asymmetric model independent with temperature and asymmetric model considering temperature effects are simulated and compared under H∞ control strategy. Results show that the proposed model is the best in accuracy and can be used for semi-active control system.