Undesired Motion Research Articles

Seismic Response Control of High-Rise Mass Varied Structures Using Linear Fluid Viscous Damper

Abstract: Seismic event induces undesirable motion in buildings, energy dissipation systems in civil engineering are indeed needed. There is a mix of structures with passive energy dissipation supplied by Fluid Viscous Dampers systems (FVD). This technology is increasingly being utilized to improve seismic protection for both existing and new structures. The findings of the FVD systems are investigated in order to compare the structural response with and without this device of energy dissipation compared for low and high rise structures, the damper installed at different storey and varying the coefficient of damping (Cd) has been focused in this paper which provides an insight when the variation of Cd and its locations,. The findings of the FVD's impressive ability to increase the structure's dissipative capabilities without increasing its stiffness. In the case of high rise FVD performance has been evaluated through the top storey displacements which will allow for a conclusion. Keywords: Coefficient of Damping, Fluid Viscous Damper, High Rise Buildings, Seismic Response, Tall Structure

Stability analysis of multi-serial-link mechanism driven by antagonistic multiarticular artificial muscles

Artificial multiarticular musculoskeletal systems consisting of serially connected links driven by monoarticular and multiarticular muscles, which are often inspired by vertebrates, enable robots to elicit dynamic, elegant, and flexible movements. However, serial links driven by multiarticular muscles can cause unstable motion (e.g., buckling). The stability of musculoskeletal mechanisms driven by antagonistic multiarticular muscles depends on the muscle configuration, origin/insertion of muscles, spring constants of muscles, contracting force of muscles, and other factors. We analyze the stability of a multi-serial-link mechanism driven by antagonistic multiarticular muscles aiming to avoid buckling and other undesired motions. We theoretically derive the potential energy of the system and the stable condition at the target point, and validate the results through dynamic simulations and experiments. This paper presents the static stability criteria of serially linked robots, which are redundantly driven by monoarticular and multiarticular muscles, resulting in the design and control guidelines for those robots.

A Compact Mirror-Symmetrical XY Compliant Parallel Manipulator for Minimizing Parasitic Rotations

Abstract The design of XY compliant parallel manipulators (CPMs) remains challenging considering the tradeoff between mirror-symmetry for better constrained undesired rotations and a small footprint, although a significant number of XY CPMs have been reported in extensive applications. This paper presents a new XY CPM using mirror-symmetry without increasing its footprint, mainly aiming to reduce the undesired parasitic rotations of input and output motion stages. The concept of mirror-symmetry is deployed to tackle the parasitic rotations, with the help of using a multilayer compact XY CPM design method. A nonlinear and analytical model of the proposed XY CPM is derived using free body diagrams and the beam constraint model (BCM) to accurately analyze its performance characteristics over a large range of motion. The designed XY CPM is then verified by the nonlinear finite element analysis (FEA) method. Finally, the proposed multilayer design is fabricated using two pieces of aluminum plate and it is mounted in a measurement system to experimentally validate several performance characteristics. The analytical, FEA, and/or experimental results show that the proposed design can sufficiently constrain undesired motions including parasitic rotation of input and output stages, cross-axis coupling error, and actuator isolation index. Compared with exiting designs, the proposed design also shows its merits in large motion range and out-of-plane stiffness.

Self-tuning anti-sway control for shipboard cranes providing combined world and deck-frame compensation

This paper presents a novel self-tuning anti-sway control system for shipboard cranes that provides full, six degree-of-freedom (DOF) motion compensation with respect to both the world (ocean) coordinate frame and the ship deck coordinate frame. The system can either manually or automatically switch between compensation modes during operation, and is capable of providing anti-sway action while tracking a time-varying operator input. Rather than requiring the operator to provide individual joint control, the entire system can track a simple three-axes Cartesian input from the operator, while simultaneously providing full anti-sway compensation in either coordinate frame.High-fidelity simulation case studies were performed with a nine-DOF shipboard knuckle boom crane, which included double pendulum dynamics between the hook and payload, in the presence of full six-DOF ship motion at sea-state six. The self-tuning anti-sway system showed at least a 92.70% reduction in payload tracking error when the corresponding compensation mode (either deck or world-frame) was activated, a significant reduction in undesired payload motion. Wind disturbances were added to the simulation using the Dryden wind model, where the system showed a maximum decrease in performance of only 0.73%; additional tests were run with self-tuning disabled, which resulted in a decrease in performance of up to 101%, indicating self-tuning is highly effective at minimizing the effect of wind disturbances.

Impact and clutch nonlinearities in the seismic response of inerto-rocking systems

Rocking bodies can be found at all structural scales, from small museum exhibits to uplifting buildings. These structures, whose dynamic stability springs from the difficulty of mobilizing their rotational inertia, are ideal candidates for benefiting from the supplemental inertia provided by inerters. This benefit can be limited, however, if the inerter drives the structural response towards potentially undesirable motions by transferring back the kinetic energy accumulated within it at inconvenient times. To control this phenomenon, a clutching system can be employed to direct the interaction between the interter and the structure improving further its dynamic behaviour. To date, however, most of the studies dealing with clutching inerto-elastic or inerto-rocking systems under seismic excitation have adopted a rather simplistic idealisation of the clutch engagement-disengagement response. In this paper, we re-visit the impact effects on inerto-rocking structures and propose an improved mechanistic model of the clutching system. First, the effects of the inerter on the transition upon impact and the impact effects on the acceleration response of rocking blocks are analysed. Then, a set of original analytical expressions for rigid and flexible rocking structures equipped with a pair of clutched inerters are derived. The newly proposed models are used to examine the evolution of the energy dissipation in the device and the influence of key parameters like the clutch stiffness, gears play, viscous damping and dry friction on its response. We conclude by evaluating the behaviour of the detailed rocking model with clutched inerters to a set of realistic earthquake ground motions. Although important differences are observed in the evolution of energy dissipation and engagement response depending on the type and characteristics of the clutch model, largely comparable peak values of displacement are obtained. On the other hand, a more accurate representation of the clutch behaviour leads to potentially larger acceleration demands. Our analyses also show that, in general, the inclusion of the inerter results in higher coefficients of restitution, indicating lower energy dissipation during impact and that the infinite acceleration spikes predicted by Housner’s model can be ignored if impact forces are sufficiently distributed over time as to cause continuous velocity transitions, but sharp enough not to appreciably affect the rotation response.

Influence of source electrode metal work function on polar gate prompted source hole plasma in arsenide/antimonide tunneling interfaced junctionless TFET

Numerous studies have explored the impact of control gate and polar gate (PG) on the retention of hole and electron charge plasma to induce the source and channel region polarity in junctionless tunnel field effect transistor (JLTFET). However, PG is not the only one responsible for the retention of hole plasma in the p+ prompted source but the hole plasma near the interface of source electrode metal (SEM) and p+ prompted source (SEM/S) is influenced by the choice of SEM work function too. This paper features a comprehensive investigation of the mutual significance of PG and SEM work function on p+ prompted source to study key analog characteristics of arsenide/antimonide tunneling interfaced hetero-material JLTFET (HJLTFET), which is unexplored in the literature otherwise. We have considered three metals—W (4.55 eV), Mo (4.65 eV), and Pd (5.3 eV) as the source electrodes in HJLTFET. For SEM work function lesser than p+ prompted source (W and Mo), the Schottky contact is formed by the depletion of hole plasma near SEM and p+ prompted source interface. This results in the immediate current inhibition at source to channel interface caused by an undesired movement of electrons en route to the Schottky interface. The Schottky tunneling phenomenon is considered by implementing the universal Schottky tunneling (UST) model to study the underestimated drain current of HJLTFET. However, the UST model becomes inconsequential for SEM work function higher than p+ prompted source (Pd) as hole plasma is preserved by the ohmic contact formation.

Evaluating the diagnosis and intervention of a sleepwalking disorder associated with violence: A case study

This study aimed to investigate a case of sleep problems associated with violence (non-REM parasomnias) and obstructive sleep apnea (OSA) besides related therapeutic approaches. The studied case in the present study was a 60-year-old man with a family history of this sleep disorder. The treatment plan in the present study was as follows: Execution of the principles of sleep hygiene by the patient, use of the continuous positive airway pressure machine (CPAP), and eight sessions of weekly biofeedback therapy. Before the intervention, the subject suffered from anxiety, minor depression, moderate quality of life, some degree of PTSD, obstructive sleep apnea, and periodic limb undesirable movements. After the intervention, there was a relative improvement in all indicators, especially obstructive sleep apnea and limb movements. Practical Implications. Given the prevalence and complexity of non-REM parasomnias, insufficient knowledge of the involved causes and mechanisms, and the failure of many pharmacological therapies, the present study can help discover the possible causes and alternative treatments based on physical and psychological factors.

Experimental analysis of tip vibrations at higher eigenmodes of QPlus sensors for atomic force microscopy

QPlus sensors are non-contact atomic force microscope probes constructed from a quartz tuning fork and a tungsten wire with an electrochemically etched tip. These probes are self-sensing and offer an atomic-scale spatial resolution. Therefore, qPlus sensors are routinely used to visualize the chemical structure of adsorbed organic molecules via the so-called bond imaging technique. This is achieved by functionalizing the AFM tip with a single CO molecule and exciting the sensor at the first vertical cantilever resonance mode. Recent work using higher-order resonance modes has also resolved the chemical structure of single organic molecules. However, in these experiments, the image contrast can differ significantly from the conventional bond imaging contrast, which was suspected to be caused by unknown vibrations of the tip. This work investigates the source of these artefacts by using a combination of mechanical simulation and laser vibrometry to characterize a range of sensors with different tip wire geometries. The results show that increased tip mass and length cause increased torsional rotation of the tuning fork beam due to the off-center mounting of the tip wire, and increased flexural vibration of the tip. These undesirable motions cause lateral deflection of the probe tip as it approaches the sample, which is rationalized to be the cause of the different image contrast. The results also provide a guide for future probe development to reduce these issues.

Hybrid Model Predictive Control of Floating Offshore Wind Turbines With Artificial Muscle Actuated Mooring Lines

Abstract Floating offshore wind turbines (FOWTs) are subject to undesirable platform motion and a significant increases in fatigue loads compared to their onshore counterparts. We have recently proposed using the fishing line artificial muscle (FLAM) actuators to realize active mooring line force control (AMLFC) for platform stabilization and thus load reduction, which features a compact design and no need for turbine redesign. However, as for the thermally activated FLAM actuators, a major control challenge lies in the asymmetric dynamics for the heating and the cooling half cycle of operation. In this paper, for a tension-leg platform (TLP) based FOWT with FLAM actuator based AMLFC, a hybrid dynamic model is obtained with platform pitch and roll degrees-of-freedom included. Then a hybrid model predictive control (HMPC) strategy is proposed for platform motion stabilization, with preview information on incoming wind and wave. A move blocking scheme is used to achieve reasonable computational efficiency. Fatigue, aerodynamics, structures, and turbulence (FAST) based simulation study is performed using the National Renewable Energy Laboratory (NREL) 5 MW wind turbine model. Under different combinations of wind speed, wave height and wind directions, simulation results show that the proposed control strategy can significantly reduce the platform roll and tower-base side-to-side bending moment, with a mild level of actuator power consumption.

A Large Animal Model for Orthopedic Foot and Ankle Research.

Trauma to the soft tissues of the ankle joint distal syndesmosis often leads to syndesmotic instability, resulting in undesired movement of the talus, abnormal pressure distributions, and ultimately arthritis if deterioration progresses without treatment. Historically, syndesmotic injuries have been repaired by placing a screw across the distal syndesmosis to provide rigid fixation to facilitate ligament repair. While rigid syndesmotic screw fixation immobilizes the ligamentous injury between the tibia and fibula to promote healing, the same screws inhibit normal physiologic movement and dorsiflexion. It has been shown that intact screw removal can be beneficial for long-term patient success; however, the exact timing remains an unanswered question that necessitates further investigation, perhaps using animal models. Because of the sparsity of relevant preclinical models, the purpose of this study was to develop a new, more translatable, large animal model that can be used for the investigation of clinical foot and ankle implants. Eight (8) skeletally mature sheep underwent stabilization of the left and right distal carpal bones following transection of the dorsal and interosseous ligaments while the remaining two animals served as un-instrumented controls. Four of the surgically stabilized animals were sacrificed 6 weeks after surgery while the remaining four animals were sacrificed 10 weeks after surgery. Ligamentous healing was evaluated using radiography, histology, histomorphometry, and histopathology. Overall, animals demonstrated a high tolerance to the surgical procedure with minimal complications. Animals sacrificed at 10 weeks post-surgery had a slight trend toward mildly decreased inflammation, decreased necrotic debris, and a slight increase in the healing of the transected ligaments. The overall degree of soft tissue fibrosis/fibrous expansion, including along the dorsal periosteal surfaces/joint capsule of the carpal bones was very similar between both timepoints and often exhibited signs of healing. The findings of this study indicate that the carpometacarpal joint may serve as a viable location for the investigation of human foot and ankle orthopedic devices. Future work may include the investigation of orthopedic foot and ankle medical devices, biologic treatments, and repair techniques in a large animal model capable of providing translational results for human treatment.

Image space trajectory tracking of 6-DOF robot manipulator in assisting visual servoing

As vision is a versatile sensor, vision-based control of robot is becoming more important in industrial applications. The control signal generated using the traditional control algorithms leads to undesirable movement of the end-effector during the positioning task. This movement may sometimes cause task failure due to visibility loss. In this paper, a sliding mode controller (SMC) is designed to track 2D image features in an image-based visual servoing task. The feature trajectory tracking helps to keep the image features always in the camera field of view and thereby ensures the shortest trajectory of the end-effector. SMC is the right choice to handle the depth uncertainties associated with translational motion. Stability of the closed-loop system with the proposed controller is proved by the Lyapunov method. Three feature trajectories are generated to test the efficacy of the proposed method. Simulation tests are conducted and the superiority of the proposed method over a Proportional Derivative – Sliding Mode Controller (PD-SMC) in terms of settling time and distance travelled by the end-effector is established in the presence and absence of depth uncertainties. The proposed controller is also tested in real-time by integrating the visual servoing system with a 6-DOF industrial robot manipulator, ABB IRB 1200.

Direct Yaw-Moment Control Integrated With Wheel Slip Regulation for Heavy Commercial Road Vehicles

When a road vehicle is subjected to combined cornering and emergency braking, it potentially has a greater risk of wheel lock followed by loss of steerability and/or undesired yaw motion. While an Anti-lock Braking System (ABS) is mandatory in many countries to avoid wheel lock, more attention is required to its combined cornering and braking performance. This paper aims to design a Direct Yaw-Moment Controller (DYC) integrated with ABS to achieve vehicle directional stability for Heavy Commercial Road Vehicles (HCRVs). This study implements a robust reaching law-based sliding mode controller for DYC and ABS. The developed algorithm was evaluated in a Hardware-in-Loop (HiL) setup. The experimental results are compared for the integrated algorithm and standalone ABS algorithms. The proposed algorithm improved the Directional Performance Index (DPI) in the range of 29% to 84% over the open-loop behavior while maintaining vehicle stability. Moreover, it also improved the DPI in the range of 5% to 53% over standalone ABS in various emergency test cases.

Effect of material variability on the seismic response of reinforced concrete box-girder bridges for different pier heights

RC bridges situated in regions prone to seismic activity are susceptible to undesirable pier column movements and deck displacements. The component-level nonlinear response evaluation can give a better picture of the seismic safety of the existing bridge structures. Many times, the material strength variability also affects the inelastic response of the structures significantly. The present study looks into the effects of column heights and material strength variability on the seismic performance of reinforced concrete bridge models adopted from past investigations, subjected to bi-directional loading. Chosen suite of 40 far-field ground excitations are employed to simulate the seismic response of chosen models in OpenSees and their non-linear response is evaluated. The seismic response of the structure is evaluated as curvature ductility of piers (primary component), and deck displacements (secondary component). Fragility curves so obtained across the damage states considered depict the difference in seismic performance of the model considering only record variability and considering record and material strength uncertainties. The results showed that for the primary component, damage probability for different states is found to be increased under material variability irrespective of the column pier height, while secondary components showed an increase in the damage state due to material strength variability for the shorter pier.

Analysis and control of a Stewart platform as base motion compensators - Part I: Kinematics using moving frames

Kinematics and its control application are presented for a Stewart platform whose base plate is installed on a floor in a moving ship or a vehicle. With a manipulator or a sensitive equipment mounted on the top plate, a Stewart platform is utilized to mitigate the undesirable motion of its base plate by controlling actuated translational joints on six legs. To reveal closed loops, a directed graph is utilized to express the joint connections. Then, kinematics begins by attaching an orthonormal coordinate system to each body at its center of mass and to each joint to define moving coordinate frames. Using the moving frames, each body in the configuration space is represented by an inertial position vector of its center of mass in the three-dimensional vector space ℝ3, and a rotation matrix of the body-attached coordinate axes. The set of differentiable rotation matrices forms a Lie group: the special orthogonal group, SO(3). The connections of body-attached moving frames are mathematically expressed by using frame connection matrices, which belong to another Lie group: the special Euclidean group, SE(3). The employment of SO(3) and SE(3) facilitates effective matrix computations of velocities of body-attached coordinate frames. Loop closure constrains are expressed in matrix form and solved analytically for inverse kinematics. Finally, experimental results of an inverse kinematics control are presented for a scale model of a base-moving Stewart platform. Dynamics and a control application of inverse dynamics are presented in the part II-paper.

Software compensation of undesirable racking motion of H-frame 3D printers using filtered B-splines

The H-frame (also known as H-Bot) architecture is a simple and elegant two-axis parallel positioning system used to construct the XY stage of 3D printers. It holds potential for high speed and excellent dynamic performance due to the use of frame-mounted motors that reduce the moving mass of the printer while allowing for the use of (heavy) higher torque motors. However, the H-frame's dynamic accuracy is limited during high-acceleration and high-speed motion due to racking -- i.e., parasitic torsional motions of the printer's gantry due to a force couple. Mechanical solutions to the racking problem are either costly or detract from the simplicity of the H-frame. In this paper, we introduce a feedforward software compensation algorithm, based on the filtered B-splines (FBS) method, that rectifies errors due to racking. The FBS approach expresses the motion command to the machine as a linear combination of B-splines. The B-splines are filtered through an identified model of the machine dynamics and the control points of the B-spline based motion command are optimized such that the tracking error is minimized. To compensate racking using the FBS algorithm, an accurate frequency response function of the racking motion is obtained and coupled to the H-frame's x- and y-axis dynamics with a kinematic model. The result is a coupled linear parameter varying model of the H-frame that is utilized in the FBS framework to compensate racking. An approximation of the proposed racking compensation algorithm, that decouples the x- and y-axis compensation, is developed to significantly improve its computational efficiency with almost no loss of compensation accuracy. Experiments on an H-frame 3D printer demonstrate a 43 percent improvement in the shape accuracy of a printed part using the proposed algorithm compared to the standard FBS approach without racking compensation.

Assessment of Reflux From Needleless Connectors: Blinded Comparison of Category Designation to Benchtop Function Using a Venous Simulator.

Needleless connectors (NCs) for vascular access have limited needlestick injuries, but complications including occlusion, thrombosis, and infections have increased despite reduced needlestick injuries. These complications relate to the ability of an NC design to limit volume fluctuations that can lead to fluid reflux with potential for microbial contamination. Different NC designs requiring specific usage protocols and training, a lack of clarity in NC function relative to manufacturer-designated categories, and confounding results from a limited number of studies comparing different NCs have resulted in confusion, ultimately leading to complications from undesirable fluid movement within the vascular access. The authors therefore quantified the magnitude of reflux with current commercially available NCs using a venous stimulator. Thirteen blinded NC designs spanning the categories of negative and positive displacement, neutral, and antireflux were tested to quantify fluid movement upon disconnection and reconnection from a representative intravenous pressure (3 NCs per design; 10 trials per NC). Trials for each NC tested followed consistent displacement trends leading to tight error bars. Blinded NCs were then characterized according to their function and compared with their category designation after unblinding. All positive and negative NCs functioned in a manner consistent with their respective category designations. Conversely, all NCs categorized as neutral actually functioned with negative displacement (ie, reflux upon disconnection; 4/5 NCs) or positive displacement (1/5 NCs). Only NCs classified as antireflux functioned as neutral, which was confirmed in a blinded bidirectional flow test. These results suggest that the neutral NC-marketed category may be confusing to users unless the particular NC design has an integrated antireflux component.

Design and Implementation of Composed Position/Force Controllers for Object Manipulation

In the design of a controller for grasping objects through a robotic manipulator, there are two key problems: to find the position of the object to be grasped accurately, and to apply the appropriate force to each finger to handle the object properly without causing undesirable movement of it during its manipulation. A proportional-integral-derivative (PID) controller is widely used to grasp objects in robotics; however, its main shortcomings are its sensitivity to controller gains, sluggish response, and high starting overshooting. This research presents three coupled (position/force) controllers for object manipulation using an assembled robotic manipulator (i.e., a gripper attached to a robotic arm mounted on a mobile robot). Specifically, an angular gripper was employed in this study, which was composed of two independent fingers with a piezoelectric force sensor attached to each fingertip. The main contributions of this study are the designs and implementations of three controllers: a classic PID controller, a type-I controller, and a type-II fuzzy controller. These three controllers were used to find an object to be grasped properly (position) and apply an equivalent force to each finger (force).

In-situ measurement of machining part deflection with Digital Image Correlation

In the context of the aeronautics industry, aluminum alloy structural parts are manufactured in several stages, from forming processes and heat treatments to final machining. Some process steps may generate residual stresses. Thus, material removal during machining releases these residual stresses, which induces part deformation. Such deformations can lead to geometric nonconformity of the machined part. It is therefore essential to control this phenomenon. Due to the variability in residual stress distribution in each raw part, the modeling approaches must to be coupled with experimental measurements. This article thus aims to define a reliable experimental technique for measuring in-plane deformation of large aeronautical parts during their machining. The backbone of the technique relies on Digital Image Correlation (DIC), which enables the contactless measurement of part deformation during machining. Moreover, DIC provides a full-field measurement and a direct evaluation of part deformations. This work discusses more specifically problems related to the use of DIC during machining, the latter corresponding to a particularly harsh environment. Indeed, optical systems undergo undesirable movement and metal chips hide areas of the observed part. These unwanted events corrupt the results. In order to control these problems and consistently apply DIC part deformation measurement during machining, specific methods are proposed in this paper. Finally, DIC measurements are performed during the same machining sequence of two parts. The excellent agreement of the two measurements confirms the reliability of the technique. Finally, measurements are discussed, emphasizing the contribution they provide to the machining community.

Formulation and Validation of an Intuitive Quality Measure for Antipodal Grasp Pose Evaluation

This letter describes a novel grasp quality measure that we developed for evaluating antipodal grasp poses in real-time. To quantify the grasp quality, we compute a set of object movement features from analyzing the interaction between the gripper and the object's projections in the image space. The normalization and weights of the features are tuned to make practical and intuitive grasp quality predictions. To evaluate our grasp quality measure, we conducted a real robot grasping experiment with 1000 robot grasp trials on 10 household objects to examine the relationship between our grasp scores and the actual robot grasping results. The results show that the average grasp success rate increases, and the average amount of undesired object movement decreases as the calculated grasp score increases. We achieved a 100% grasp success rate from 100 grasps of the 10 objects when using our grasp quality measure in planning top quality grasps. In addition, we compared our quality measure with the Q measure and deep learning-based quality measures.

Error Analysis of the Combined-Scan High-Speed Atomic Force Microscopy

A combined tip-sample scanning architecture can improve the imaging speed of atomic force microscopy (AFM). However, the nonorthogonality between the three scanners and the nonideal response of each scanner cause measurement errors. In this article, the authors systematically analyze the influence of the installation and response errors of the combined scanning architecture. The experimental results show that when the probe in the homemade high-speed AFM moves with the Z-scanner, the spot position on the four-quadrant detector changes, thus introducing measurement error. Comparing the experimental results with the numerical and theoretical results shows that the undesired motion of the Z-scanner introduces a large error. The authors believe that this significant error occurs because the piezoelectric actuator not only stretches along the polarization direction but also swings under nonuniform multifield coupling. This article proposes a direction for further optimizing the instrument and provides design ideas for similar high-speed atomic force microscopes.