Active Tendon Research Articles

Advanced seismic control strategies for smart base isolation buildings utilizing active tendon and MR dampers

This paper investigates the seismic behaviour of a five-storey shear building that incorporates a base isolation system. Initially, the study considers passive base isolation and employs a multi-objective archived-based whale optimization algorithm called MAWOA to optimize the parameters of base isolation. Subsequently, a novel model is proposed, which incorporates an interval type-2 Takagi-Sugeno fuzzy logic controller (IT2TSFLC) utilizing clustering techniques. The building includes Magneto-rheological (MR) dampers installed at the base isolation level and two active tendons positioned on the first and second storeys of the structure. The semi-active control force of the base isolation with MR dampers is determined by the fuzzy system, while the active control force for the active tendons is computed using the linear quadratic regulator (LQR) algorithm, enabling control force provision during seismic events. The primary objective of this model is to enhance the seismic control of the building. Therefore, it is classified as a proposed model. The structural system is subjected to seismic analyses, considering three different structural configurations: uncontrolled, equipped with passive base isolation, and equipped with semi-active base isolation combining MR dampers and active tendons. The findings of the research demonstrate that by considering the optimization of parameters of the passive base isolation based on the white noise scenario and using these parameters as design parameters, during seismic analysis of the structure in some earthquakes, increased structural responses were observed when compared to uncontrolled structure, highlighting a potential risk. Nevertheless, the proposed system effectively addresses this drawback of passive control systems by markedly reducing structural responses, as compared to both passive base isolation and uncontrolled structure. These results suggest that the proposed system is an effective solution for mitigating seismic risks in structural seismic control.

Comparison Analysis of Bio-Inspired Tendon-Driven Manipulators Based on Their Tension-Feasible Workspace

Abstract Bio-inspiration can be used in the development of novel dextrous and energy-efficient manipulators. This paper focuses on planar manipulators inspired by the bird neck, built upon stacking a series of tensegrity X-joints. The manipulators are actuated with four tendons and have different numbers of modules, with or without offsets. The objective of this work is to study the influence of offsets, number of modules, geometry of the joints, configuration at rest of the manipulators, and actuation scheme on the size of the tension-feasible workspace (TFW). The spring constants of the X-joints are determined so that the configuration at rest features a desired end-effector (EE) pose with minimal stiffness to ensure stability. Our study demonstrates that increasing the number of modules results in a larger TFW, although the number of active tendons is fixed. We find that the TFW can be maximized with appropriate modification of the joint geometry. Additionally, we explore the influence of bio-inspired approaches on the manipulator configuration at rest and actuation scheme in relation to the TFW. In addition, we conduct an analysis of the EE pose stiffness, revealing that offsets decrease this stiffness, while an optimal number of modules exists to achieve maximum stiffness. We observed that increasing the width of the manipulator generally enhances stiffness, while the configuration at rest and the actuation have little effects. Furthermore, experiments were conducted to validate the methodologies.

Active Vibrational Achilles Tendon Sensing for Identifying and Characterizing Inflammatory Symptomatology in Enthesitis Related Arthritis.

This study explores the potential of active vibrational sensing as a digital biomarker to identify and characterize inflammatory symptomatology in the Achilles tendon and its entheses in juvenile idiopathic arthritis (JIA), particularly enthesitis related arthritis (ERA), a subcategory of JIA. Active vibrational data were non-invasively recorded using a miniature coin vibration motor and accelerometer. Twenty active vibration recordings from children diagnosed with JIA were used in the analysis. Machine learning algorithms were leveraged to classify the vibrational signatures according to the corresponding subject groups. Subjects were classified into symptomatic ERA (sxERA), asymptomatic ERA (asxERA), and asymptomatic JIA (non-ERA) (asxNERA) groups based on clinical evaluations and ILAR criteria. Distinct vibrational signatures were observed during tiptoe standing, providing differentiation between subject groups. Feature-based and waveform-based approaches effectively classified the sxERA group against asxNERA and asxERA groups using leave-one-subject-out (LOSO-CV) and 3-fold cross-validation. For the 3-fold crossvalidation, the mean accuracies for distinguishing sxERA from asxNERA were 81% (feature-based) and 81% (waveform-based), while the accuracies for discriminating sxERA against asxERA were 73% (feature-based) and 74% (waveform-based). Active vibrational sensing demonstrates promise as a tool for identifying Achilles tendon inflammation in JIA, potentially aiding in early diagnosis and disease monitoring. Developing active vibrational sensing as a diagnostic modality could address challenges in diagnosing ERA and facilitate timely intervention and personalized care for JIA, potentially enhancing long-term patient outcomes.

A hybrid clustering-based type-2 adaptive neuro-fuzzy forecasting model for smart control systems

The practical applicability of smart control systems suffers from the existence of uncertainty in the physical parameters, sensor measurements and external excitations. Effective methods and its ease of implementation are required in the real-time active control strategies. To this end, in this research, we introduce an overlapping clusters and Multilayer Extreme Learning Machine (ML-ELM)-aided interval type-2 Takagi-Sugeno fuzzy inference system for vibration mitigation of smart structures. The combined Fuzzy C-Means (FCM) and imperialist competitive algorithm (ICA) with respect to degree of fuzzy overlap between clusters was utilized for characterizing the upper and lower membership functions forming the antecedent part. Furthermore, indeterminacy was modeled as footprint of uncertainty (FOU) and automatically formed based on statistical characteristics of soft clusters. The consequent parameters were adjusted by hybridization of ML-ELM and overlapping clusters, then the adaptivity was guaranteed. The predictive accuracy and generalization capability of the proposed method were demonstrated over the estimation of active control effort. Finally, to prove the practicability of the implemented framework, it was applied to four high-rise, mid-rise and low-rise benchmark building structures equipped with active mass damper (AMD), active tendon and active bracing system (ABS). The obtained results demonstrated the higher predictive accuracy and generalization ability of the presented data-driven control scheme compared to the other standard technical machine learning strategies. This practical guideline is easy to implement and automates control engineering tasks in real-time applications, solving one of the most challenging aspects of smart control systems.

Identification of c.1495C > T mutation in SPAST gene in a family of Han Chinese with hereditary spastic paraplegia

BackgroundHereditary spastic paraplegia 4 (SPG4) caused by spastin (SPAST) gene mutations accounts for 40–45% of hereditary spastic paraplegia (HSP) cases. To search for more genetic evidences for the pathogenesis of HSP, the SPAST genotype and clinical phenotype of a Chinese Han SPG4 family were analysed in this study. MethodsThe clinical data of the proband and his family members were collected. Whole genomic DNA was extracted from peripheral blood, and the gene detection and pathogenicity analysis of mutations were conducted using whole-exome sequencing technology. Suspected pathogenic mutations were identified. Verification within this family was conducted by Sanger sequencing. ResultsEight (4 males and 4 females) of 20 members in 4 generations had SPG4. All patients presented with the high feet arches (pes cavus), the abnormal gait, the active tendon reflexes of the upper limbs, the hyperreflexia of the lower limbs, and the positive ankle clonus and Babinski’s signs bilaterally. In the proband, we found a heterozygous mutation c.1495C > T in SPAST gene, which was associated with the autosomal dominant SPG4. Both the daughters and granddaughters of the proband in this family were verified to carry this mutation. The clinical characteristics of the SPG4 patients in this family are in line with the simple type of HSP. Heterozygous c.1495C > T is a pathogenic mutation in this family. ConclusionIn this study, we identified a c.1495C > T mutation in the SPAST gene in a Han Chinese family, enriching the mutation spectrum of SPG4.

Robust Control of Structures with Active Tendon and Fuzzy-LQR Algorithm Considering Uncertainties of Structural Parameters

Robust Control of Structures with Active Tendon and Fuzzy-LQR Algorithm Considering Uncertainties of Structural Parameters

Active Heat Acclimation Does Not Alter Muscle-Tendon Unit Properties.

Heat acclimation (HA) is recommended before competing in hot and humid conditions. HA has also been recently suggested to increase muscle strength, but its effects on human's muscle and tendon mechanical properties are not yet fully understood. This study investigated the effect of active HA on gastrocnemius medialis (GM) muscle-tendon properties. Thirty recreationally active participants performed 13 low-intensity cycling sessions, distributed over a 17-d period in hot (HA = ~38°C, ~58% relative humidity; n = 15) or in temperate environment (CON = ~23°C, ~35% relative humidity; n = 15). Mechanical data and high-frame rate ultrasound images were collected during electrically evoked and voluntary contractions pre- and postintervention. Shear modulus was measured at rest in GM, and vertical jump performance was assessed. Core temperature decreased from the first to the last session in HA (-0.4°C ± 0.3°C; P = 0.015), while sweat rate increased (+0.4 ± 0.3 L·h -1 ; P = 0.010), suggesting effective HA, whereas no changes were observed in CON (both P ≥ 0.877). Heart rate was higher in HA versus CON and decreased throughout intervention in groups (both P ≤ 0.008), without an interaction effect ( P = 0.733). Muscle-tendon unit properties (i.e., maximal and explosive isometric torque production, contractile properties, voluntary activation, joint and fascicular force-velocity relationship, passive muscle, and active tendon stiffness) and vertical jump performance did not show training ( P ≥ 0.067) or group-training interaction ( P ≥ 0.232) effects. Effective active HA does not alter muscle-tendon properties. Preparing hot and humid conditions with active HA can be envisaged in all sporting disciplines without the risk of impairing muscle performance.

A novel active tendon pendulum tuned mass damper and its application in transient vibration control

Enhancing the performance characteristics of Tuned Mass Dampers (TMDs), in particular extending their narrow frequency band of operation, has been the subject of many researches. In the adaptive type of TMDs, the device's properties can be adjusted gradually in response to a slight alteration in the excitation characteristics and physical properties of the main structure. A novel vibration absorbing system, namely Active Tendon Pendulum TMD (AT-PTMD), is proposed in the present study. The device consists of a simple pendulum whose horizontal movement is restricted by a tendon with an adjustable tensile force which is attached to the pendulum’s rod. The device is designed and formulated, and its efficiency is assessed numerically and experimentally. For this purpose, a 3-degree of freedom structure is considered. Scrutinizing the responses of the uncontrolled, passively controlled and actively controlled structure shows the appropriate performance of the AT-PTMD in comparison with the passive TMD system in transient vibration reduction, particularly in reducing the total vibrational energy of the structure's response. Considering the achieved results, the proposed AT-PTMD system is capable of reducing the maximum displacement and acceleration of the main structure up to 43% and 37%, respectively, which substantiates its excellence over the common passive vibration absorbing devices. The case study also proves that the utilized mechanism for adjusting the equivalent stiffness of AT-PTMD increases its operating frequency range by 105% compared to common TMDs. Unlike active structural control systems, the suggested approach will not induce structural instability in any operating mode.

Seismic Response Control of Structures with Stiffness Irregularities through Optimally Placed Active Tendons using Multiobjective Genetic Algorithm

This paper studied the seismic response control of structural building with stiffness irregularities through active tendon system (ATS) using Linear Quadratic Regulator control algorithm. The various responses considered are the floor displacements, story drifts, and base shear. The optimal number and the optimal position of these active tendons are obtained through multiobjective optimization using Genetic Algorithm to reduce the responses and the cost of the control system simultaneously. The conflicting objectives minimized are the base shear of the irregular building and the number of active tendons to be used. The maximum story drift and maximum floor displacement are used as constraints. For numerical results, six combinations of stiffness irregularity in critical storys 1,2,and 10 of a ten story defecient shear building frame subjected to El Centro earthquake is considered. The results show that the optimized control system is capable of keeping the responses of the building frame to an earthquake within permissible limits and stiffness irregularity in the same defecient frame cost only the tendon in atmost one additional story.

A mechanical adhesive gripper inspired by beetle claw for a rock climbing robot

Rock climbing robots have wide application prospects in field operations and planetary exploration. Herein, a spiny gripper inspired by the beetle (Coleoptera) claw is developed, which can accomplish easy attachment, detachment and good compliance on irregular rough surfaces without complex controls. The attachment probabilities of various microspine layouts are simulated to determine the optimal design parameters for the spine tile. By referencing the structure and attachment process of the beetle claw, a spiny gripper with four bioinspired branches is designed to enable adaptive attachment and smooth detachment. The gripper employs a novel drivetrain hybridized with passive torsion springs and active tendons driven by an ingenious winch to achieve light weight, load-sharing, self-adaptation, and strong adhesion on irregular rough surfaces. The grasp sequence, grasp wrench and gripper maximum adhesion are all investigated. Tests on various surfaces verify its excellent performance. With a weight of 0.352 kg, its normal adhesion and tangential adhesion are 39.7 N and 47.5 N, respectively. In addition, the gripper is integrated into the climbing robot RockClimbo to allow it to move on extreme terrain.

Active vibration control of horizontal-axis wind turbine blades using disturbance observer-based boundary control approach

This paper addresses the issue of controlling vibration in horizontal-axis wind turbine (HAWT) blades under unknown boundary and distributed disturbances using an observer-based boundary control approach. In this regard, an actuator configuration, involving four active tendons mounted on the tip of the blade, is proposed to generate the out-of-plane and in-plane boundary control forces. The out-of-plane and in-plane governing equations are given as a set of PDEs and ODEs under parametric and direct excitations using Rayleigh beam theory including rotary inertia. A new disturbance observer is introduced to estimate boundary disturbances and subsequently combined with a new boundary control law for alleviating the HAWT blade vibration in the presence of unknown but bounded distributed disturbances. The uniform boundedness of the closed-loop system under unknown bounded distributed disturbances is confirmed via employing the Lyapunov’s direct method together with LaSalle–Yoshizawa’s theorem. Moreover, it is proved that the closed-loop system is uniformly exponentially stable in the absence of distributed and boundary disturbances. The reference NREL 5 MW HAWT blade is selected as the case study and the blade element momentum theory (BEMT) is employed to compute the aerodynamic load. Then, the open-loop and closed-loop responses of the blade under wind shear inflow and a predefined boundary disturbance are compared to demonstrate the performance of the closed-loop system in operational conditions.

WALANT: A Discussion of Indications, Impact, and Educational Requirements.

Wide-awake, local anesthesia, no tourniquet (WALANT) is a technique that removes the requirement for operations to be performed with a tourniquet, general/regional anesthesia, sedation or an anesthetist. We reviewed the WALANT literature with respect to the diverse indications and impact of WALANT to discuss the importance of future surgical curriculum integration. With appropriate patient selection, WALANT may be used effectively in upper and lower limb surgery; it is also a useful option for patients who are unsuitable for general/regional anesthesia. There is a growing body of evidence supporting the use of WALANT in more complex operations in both upper and lower limb surgery. WALANT is a safe, effective, and simple technique associated with equivalent or superior patient pain scores among other numerous clinical and cost benefits. Cost benefits derive from reduced requirements for theater/anesthetic personnel, space, equipment, time, and inpatient stay. The lack of a requirement for general anesthesia reduces aerosol generating procedures, for example, intubation/high-flow oxygen, hence patients and staff also benefit from the reduced potential for infection transmission. WALANT provides a relatively, but not entirely, bloodless surgical field. Training requirements include the surgical indications, volume calculations, infiltration technique, appropriate perioperative patient/team member communication, and specifics of each operation that need to be considered, for example, checking of active tendon glide versus venting of flexor tendon pulleys. WALANT offers significant clinical, economic, and operative safety advantages when compared with general/regional anesthesia. Key challenges include careful patient selection and the comprehensive training of future surgeons to perform the technique safely.

Faster early rate of force development in warmer muscle: an in vivo exploration of fascicle dynamics and muscle-tendon mechanical properties.

Although heat exposure has been shown to increase the skeletal rate of force development (RFD), the underlying processes remain unknown. This study investigated the effect of heat on gastrocnemius medialis (GM) muscle-tendon properties and interactions. Sixteen subjects performed electrically evoked and voluntary contractions combined with ultrafast ultrasound under thermoneutral [control (CON): 25.8 ± 1.8°C, core temperature 37.0 ± 0.3°C, muscle temperature 34.0 ± 1.1°C] and passive heat exposure [hot (HOT): 47.4 ± 1.8°C, core temperature 38.4 ± 0.3°C, muscle temperature 37.0 ± 0.8°C] conditions. Maximal voluntary force changes did not reach statistical significance (-5.0 ± 11.3%, P = 0.052) whereas voluntary activation significantly decreased (-4.6 ± 8.7%, P = 0.038) in HOT. Heat exposure significantly increased voluntary RFD before 100 ms from contraction onset (+48.2 ± 62.7%; P = 0.013), without further changes after 100 ms. GM fascicle dynamics during electrically evoked and voluntary contractions remained unchanged between conditions. Joint velocity at a given force was higher in HOT (+7.1 ± 6.6%; P = 0.004) but the fascicle force-velocity relationship remained unchanged. Passive muscle stiffness and active tendon stiffness were lower in HOT than CON (P ≤ 0.030). This study showed that heat-induced increases in early voluntary RFD may not be attributed to changes in contractile properties. Late voluntary RFD was unaltered, possibly due to decreased soft tissues' stiffness in heat. Further investigations are required to explore the influence of neural drive and motor unit recruitment in the enhancement of explosive strength elicited by heat exposure.

Experimental modal analysis of a rotating tendon-loaded helicopter blade demonstrator

A novel concept which uses an internal tendon to apply a compressive force on the blades for resonance avoidance of rotorcraft, so-called ‘active tendon concept’, was put forward recently. This research enhances the active tendon concept further toward its basic experimental validation in the rotating operational conditions. To progress in this direction, a new fully dynamically instrumented demonstrator combined with the displacement-based axial load application system is developed and assessed experimentally in non-rotating and rotating conditions for the rotor speeds ranging from 0 rpm to 500 rpm and axial compressive loads ranging from 0 N to 500 N. The identified modal dynamics is used to validate the comprehensive reduced-order model which is subsequently used to support the interpretation of the rotating results where the applied experimental methods lacked in resolution of range.It is observed that the rotating system features anticipated modal dynamics in the form of centrifugal stiffening and compressive softening of the beam-dominated modes, whilst the tendon-dominated modes display rapid stiffening effects with the applied axial loads. As a result of these opposing trends, further interactional phenomena such as modal veering are observed experimentally and in model-predicted results. One consistently observed beam-dominated mode is used to extend the range of the experimental observations beyond those supported by the models toward the damping characterisation throughout the veering interactions and complex strain mode analysis.The results presented in this work confirm the anticipated modal behaviour and suggest that the rotating systems can be influenced through controllable preloads whilst in the state of rotation. Additional vibration and load control opportunities arise from the emergent and tunable interactional dynamics between the primary beam or blade system and the secondary augmented tendon preload application system.

Patients’ experiences of flexor tendon rehabilitation in relation to adherence: a qualitative study

Purpose To explore patients’ experiences of early active motion flexor tendon rehabilitation in relation to adherence to restrictions and outcome of rehabilitation. Method Seventeen patients with a flexor tendon injury in one or several fingers participated in qualitative interviews performed between 74 and 111 days after surgery. Data were analysed using directed content analysis with the Health Belief Model (HBM) as a theoretical framework. Results Perceived severity of hand function and susceptibility to loss of hand function affected the participants’ behaviour. A higher perceived threat increased motivation to exercise and be cautious in activities. During rehabilitation, the perceived benefits or efficacy of doing exercise and following restrictions were compared to the cost of doing so, leading to adherence or non-adherence behaviour. Perceived self-efficacy was affected by previous knowledge and varied through the rehabilitation period. External factors and interaction with therapists influenced the perception of the severity of the injury and the cost and benefits of adhering to rehabilitation. Conclusion Patient’s perception of the injury, the effectiveness of exercises, context and social support to manage daily life affected adherence to restriction, motivation and commitment to rehabilitation. The HBM as a theoretical framework can be beneficial for understanding factors that influence patients’ adherence. Implications for Rehabilitation Information regarding the injury and consequences for the patient should be presented at different time points and in different ways, tailored to the patient. It’ is important to aid patients to perceive the small gradual improvements in hand function to create motivation to adhere to exercise. Strategies to reduce the cost of adherence in terms of managing everyday life should be addressed by individually based strategies. Instructions regarding exercise and restrictions should be less complex and consider the patient’s individual needs.

Seismic Response Prediction of Open- and Closed-Loop Structural Control Systems Using a Multi-State-Dependent Parameter Estimation Approach

In this paper, a new modified multi-state-dependent parameter (MSDP) model estimation method is proposed with the aim of application for seismic response prediction of open- and closed-loop structural control systems. In the first phase, the recursive Kalman filtering is improved and an improved recursive fixed interval-smoothing algorithm is then proposed in the second phase. The numerical studies are conducted on a seismic-excited 3-story benchmark structure in three cases of open-loop structural system, open-loop structural control with tuned mass damper (TMD) as a passive device, and closed-loop structural control with an active tendon system (ATS). Using the proposed MSDP models, the time-histories of acceleration of the floors are predicted during earthquakes and the validation of the proposed models is evaluated with those given by the finite element method (FEM) of OpenSees software. Using three evaluation criteria, the superiority of the modified MSDP over the MSDP is found. The simulation results show that the proposed models are capable of following the seismic responses of the structure well and estimating them with high accuracy in further time steps. With high accuracy and lower computational cost, the surrogate models can be easily utilized in optimal design processes of the passive device for the open-loop structural control and the active control algorithm for the closed-loop structural control and structural health monitoring (SHM) applications.

Active Tendon Control of Stay Cable by a Giant Magnetostrictive Actuator Considering Time-Delay

Active control of a stay cable through changing its tension is an effective way to lower the vibration amplitude. In this paper, active tendon control of a stay cable using a giant magnetostrictive actuator (GMA), which can generate axial deformation in a short period (normally less than 10 ms) under magnetic fields, is studied considering the time-delay. The bilinear controlled state equation of the small-sag cable is established by employing the Lagrange formulation. The linearization method for the bilinear controlled state equation is proposed and validated by numerical simulations. A GMA is designed and manufactured to actively control a stay cable model and the relationship between the output force and the input voltage is obtained by experiments. Based on the phase-shifting method, a multi-mode control algorithm with the time-delay compensation is proposed, and the time-delay compensation matrix based on the state feedback control algorithm is obtained. Based on a 1:20 scaled cable model, simulations and experiments are conducted to investigate the control performance of the proposed method under different external loads including the free vibration, harmonic excitation and random excitation. The results show that the tendon control of cable vibration by a GMA may be invalid and even amplify the vibration amplitude when the compensation of time-delay is not considered. Moreover, the excellent control performance can be achieved by using the proposed time-delay compensation method.

Effect of Stretching of Spastic Elbow Under Intelligent Control in Chronic Stroke Survivors-A Pilot Study.

Objective: To assess the short-term effects of strenuous dynamic stretching of the elbow joint using an intelligent stretching device in chronic spastic stroke survivors.Methods: The intelligent stretching device was utilized to provide a single session of intensive stretching to the spastic elbow joint in the sagittal plane (i.e., elbow flexion and extension). The stretching was provided to the extreme range, safely, with control of the stretching velocity and torque to increase the joint range of motion (ROM) and reduce spasticity and joint stiffness. Eight chronic stroke survivors (age: 52.6 ± 8.2 years, post-stroke duration: 9.5 ± 3.6 years) completed a single 40-min stretching intervention session. Elbow passive and active ROM, strength, passive stiffness (quantifying the non-reflex component of spasticity), and instrumented tendon reflex test of the biceps tendon (quantifying the reflex component of the spasticity) were measured before and after stretching.Results: After stretching, there was a significant increase in passive ROM of elbow flexion (p = 0.021, r = 0.59) and extension (p = 0.026, r = 0.59). Also, elbow active ROM and the spastic elbow flexors showed a trend of increase in their strength.Conclusion: The intelligent stretching had a short-term positive influence on the passive movement ROM. Hence, intelligent stretching can potentially be used to repeatedly and regularly stretch spastic elbow joints, which subsequently helps to reduce upper limb impairments post-stroke.

Optimal fractional-order PID control design for time-delayed multi-input multi-output seismic-excited structural system

The application of the fractional-order PID (FOPID) controller is recently becoming a topic of research interest for vibration control of structures. Some researchers have successfully implemented the FOPID controller in a single-input single-output (SISO) control structural system subjected to earthquake excitations. However, there is a lack of research that focuses on its application in multi-input multi-output (MIMO) control systems to implement it in seismic-excited structures. In this case, the cross-coupling of the process channels in the MIMO control structural system may result in a complex design process of controllers so that each loop is independently designed. From an operational point of view, the time delay and saturation limit of the actuators are other challenges that significantly affect the performance and robustness of the controller so that ignoring them in the design process may lead to unrealistic results. According to the challenges, the present study proposed an optimal fractional-order PID control design approach for structural control systems subjected to earthquake excitation. Gases Brownian motion optimization (GBMO) algorithm is utilized for optimal tuning of the controller parameters. Considering six real earthquakes and seven performance indices, the performance of the proposed controller, implemented on a ten-story building equipped with an active tendon system (ATS), is compared with those provided by the classical PID controller. Simulation results indicate that the proposed FOPID controller is more efficient than the PID in both terms of seismic performance and robustness against time-delay effects. The proposed FOPID controller can maintain suitable seismic performance in small time delays, while a significant performance loss is observed for the PID controller.

Vibration control of a rotating Timoshenko beam-tendon system via internal guiding inerter-dampers

A guided active tendon concept is proposed to modify the dynamics of the main rotor blades to enable the rotorcraft to operate in the wider range of working conditions. Because some blade modes are not sensitive to the applied axial force, in this paper, a new vibration suppression method for a rotating Timoshenko beam axially loaded by a tendon with the inerter-damper guiding elements is proposed and studied. The equations of motion are derived by means of the Lagrange's equation with the use of the energy expressions, and the modal and harmonic analyses are carried out. The analytical model is verified and compared with an independently formulated finite element model. It is found that inerter-dampers introduce non-local modes. To tune the chosen beam-dominated modes using inerter-dampers without introducing the additional resonances, the new optimal tuning strategy is proposed. When one inerter-damper is used, the inertance and damping coefficient for the optimal tuning of the higher modes are lower than those for the lower modes. When the inerter-damper is used to tune a single mode optimally, its function is analogous to a viscous damper for the lower modes, but it is similar to a rigid attachment for the higher modes. The maximum attainable damping ratio tends to decrease with the reduction of the applied axial force and increase of the rotational speed. The optimal performance of the single inerter-damper at different locations varies. For example, it is found that the damping ratio of the second beam-dominated mode reaches the maximum value with the inerter-damper located between 0.5-0.6L from the fixed end, where the required inertance and damping coefficient for the optimal tuning reach the minimum. More inerter-dampers can be used to tune a larger number of the beam-dominated modes optimally and simultaneously. The inerter-dampers are shown to effectively suppress the beam-dominated modes in wide axial force and speed ranges. In addition, inerter-dampers can be used to support the same function as the rigid tendon-guiding attachments of increasing the frequencies of the tendon-dominated modes. However, they cannot alter the critical compressive force. By integrating inerter-dampers into the tendon-loaded blades internally, the modes insensitive to the applied axial force can be suppressed to mitigate resonant vibrations.