Body Torque Research Articles

Soft Artificial Muscle Based on Pre-Detwinned Shape Memory Alloy Spring Actuator Achieving High Passive Assistive Torque for Wearable Robot.

For designing the assistive wearable rehabilitation robots, it is challenging to design the robot as energy efficient because the actuators have to be capable of overcoming human loads such as gravity of the body and spastic torque continuously during the assistance. To address these challenges, we propose a novel design of soft artificial muscle that utilizes shape memory alloy (SMA) spring actuators with pre-detwinning process. The SMA spring was fabricated through a process called pre-detwinning, which enhances the linearity of the SMA spring in martensite phase and unpowered restoring force, which is called passive force. The fabricated SMA spring can contract >60%. Finally, the soft wearable robot that can assist not only the gravitational torque exerted on the elbow by passive force, but also the elbow movements with active force was designed with a soft artificial muscle. A soft artificial muscle consists of the bundles of pre-detwinned SMA springs integrated with the stretchable coolant vessel. The stiffness of the muscle was measured as 1125 N/m in martensite phase and 1732 N/m in austenite phase. In addition, the muscle showed great actuation frequency performances, the bandwidth of which was measured as 0.5 Hz. The proposed wearable mechanism can fully compensate the gravitational torque for all the angles in passive mode. In addition, the proposed mechanism can produce high torque up to 3.5 Nm and movements in active mode.

A novel analysis method for magnetically actuated soft origami mechanisms

The magnetically actuated soft origami mechanisms (MASOMs), which integrates the advantages of magnetic actuation and origami mechanisms, possesses promising prospective applications on soft untethered machines such as soft robots and compliant actuators. Generally, the deformation behavior of these mechanisms are analyzed through finite element analysis (FEA) considering elusive nonlinear constitutive equations of magnetically actuated elastomer that captures magnetic body torque and force induced by a magnetic field. However, it is time-consuming and troublesome to model and analyze the case with heterogeneous magnetization distribution. We propose an equivalent magnetic bar and hinge model to investigate the folding behavior of planar MASOMs under a uniform magnetic field. Both FEA and experiments are conducted to demonstrate the effectiveness of the proposed model in analyzing MASOMs with different system geometries and magnetization profiles. Two case studies with parallel and serial origami creases and different magnetization profiles are provided to show the practicability. The proposed model provides an effective method to investigate and design MASOMs.

Effect of material type, torque value, and sterilization on linear displacements of a scan body: An in vitro study.

There is limited knowledge on the effect of scan body (SB) material type, torque value, and sterilization on linear displacements of implant SBs. To evaluate the effect of material type, torque value, and sterilization on linear displacements of SBs during screw tightening by using digital image correlation (DIC) analysis. One polyetheretherketone (PEEK, Zfx Intraoral Scan Body) and one titanium SB (Ti, MPS Zimmer Scanbody R1410) were tightened with 5Ncm torque on two implants (Zimmer TSV ⌀4.7 mm) by using a digital torque limiting device. SBs' initial spatial positions relative to the implants were recorded by using 3D DIC technique. Measurements were repeated after initially increasing torque value to 10Ncm and then to 15 Ncm, and these steps were repeated for a total of 10 PEEK and 10 Ti SBs on both implants (n=20). All SBs were then sterilized 25 times by using an autoclave (STATIM 5000 S G4) according to manufacturer's recommendations and all measurements were repeated. Linear displacements on three axes were calculated for each SB with increasing torque values (from 5to 10Ncm and from 10 to 15 Ncm) before and after sterilization. SB displacements within each torque value-sterilization pair were compared by using Mann-Whitney U test, whereas Wilcoxon signed-rank test was used to compare SB displacements within each material-torque value pair between conditions and within each material-sterilization pair between torque values (α=0.05). On x-axis, PEEK SBs had higher displacements than Ti SBs (p < 0.001), whereas sterilization (p ≤ 0.028) and 15 Ncm torque application (p ≤ 0.006) led to higher displacements of PEEK SBs. On y-axis, PEEK SBs had higher displacements than Ti SBs with 15 Ncm torque application (p ≤ 0.033). A total of 15 Ncm torque-applied PEEK SBs and 10Ncm torque-applied Ti SBs had higher displacements after sterilization (p ≤ 0.028). Application of 15 Ncm torque led to higher displacements regardless of the material (p ≤ 0.002). On z-axis, PEEK SBs had higher displacements (p ≤ 0.015), except for 10Ncm torque-applied sterilized SBs (p=0.102). With 10Ncm torque application, sterilization decreased the displacement values of PEEK SBs (p=0.044). Greater displacements were observed with 10Ncm torque-applied Ti SBs before sterilization and 15 Ncm torque-applied PEEK SBs after sterilization (p ≤ 0.033). Axial displacement of SBs was affected by material type, torque value, and sterilization. Ti SBs mostly had lower displacements than PEEK SBs. Application of 15 Ncm torque to tested PEEK SBs should be refrained from and a calibrated tightening tool may enable the application of 10Ncm or lower torque values for lower displacements. Sterilization generally increased PEEK SB displacements.

Anisotropic swimming and reorientation of an undulatory microswimmer in liquid-crystalline polymers

Microorganisms can efficiently navigate in anisotropic complex fluids, but the precise swimming mechanisms remain largely unexplored. Their dynamics is determined by the interplay between multiple effects, including the fluid's orientation order, swimmer's undulatory gait and the finite length. Here, we extend the numerical study of the two-dimensional undulatory motions of a flexible swimmer in lyotropic liquid-crystalline polymers (LCPs) by Lin et al. (J. Fluid Mech., vol. 921, 2021, p. A25) to the scenario of arbitrary swimming directions with respect to the nematic director. The swimmer is modelled as a nearly inextensible yet flexible fibre with imposed travelling-wave-like actuation. We investigate the orientation-dependent swimming behaviours in nematic LCPs for an infinitely long sheet (i.e. Taylor's swimming sheet model) and finite-length swimmers. We demonstrate that the swimmer must be sufficiently stiff to produce undulatory deformations to gain net motions. Moreover, a motile finite-length swimmer can reorient itself to swim parallel with the nematic director, due to a net body torque arising from the asymmetric distribution of the polymer force along the body.

Ergonomics Evaluation for Turning Machinists in Oil and Gas Industry

It was discovered that there were ergonomics risk factors towards machinists during manual handling of large work pieces that may affect the health of the machinists based on the initial ergonomics risk assessment conducted on the CNC turning machine shop in oil and gas manufacturing company. The study aims to determine and improve the ergonomics risk factor that the machinists may be exposed to. In this study, the data were collected and analyzed using Cornell Musculoskeletal Questionnaire, Rapid Entire Body Assessment (REBA) and torque analysis. Survey result from Cornell Musculoskeletal Questionnaire found that most of the turning machinists experienced ache, pain and discomfort on their lower back, right hand shoulder and upper back. REBA analysis indicated that body posture applied during tightening headstock jaws is categorized as very high risk with REBA score of 11 and immediate improvement action is required. The root cause was identified using 5 Why methodology where torque wrench design limitation has been identified as the main contributor to the very high REBA score. The input torque applied by the machinist was reduced, and the location of the tightening torque applied for clamping and adjusting purposes was changed using manual torque multiplier equipment. The input torque applied by machinist reduced from 1200Nm to 44.4Nm, and the pulling force applied was reduced from 128.7kgf to 9.1kgf, significantly lowering the REBA score from 11 (very high risk) to 3 (low risk). The objective of the study has been achieved by significant improvement of REBA score for the very high-risk postures that the machinists are exposed to.

A fully analytical solution of convection in ferrofluids during Couette-Poiseuille flow subjected to an orthogonal magnetic field

We report the transport of thermal energy during a hydrodynamically as well as thermally developed Couette-Poiseuille flow of ferrofluid (FF) through parallel-plate channels subjected to a constant magnetic field, orthogonal to the channel axis. The fluid motion is imparted by a combination of tangential stress, attributable to the motion of one of the plates, and a constant pressure gradient present in the direction of the channel axis. Apart from imparting a body force and torque, the application of an external magnetic field increases both the dynamic viscosity and effective thermal conductivity of the FF. As a result, thermal energy transport is uniquely affected. The complex coupling of magnetics with hydrodynamics results in implicit governing equations, which cannot be solved analytically in their full form. On the basis of logical reasoning, the governing equations are simplified to generate closed-form solutions of temperature profiles and Nusselt numbers. For a comprehensive study, we consider three different sets of thermal boundary conditions amenable to analytical solutions. Till the saturation of magnetization, we observe an increase in the local temperature as the strength of the applied magnetic field increases. The effects of particle loading in FF, Brinkman number, and heat flux ratio on the temperature field are also discussed.

Accurate Tracking of Aggressive Quadrotor Trajectories Using Incremental Nonlinear Dynamic Inversion and Differential Flatness

Autonomous unmanned aerial vehicles (UAVs) that can execute aggressive (i.e., high-speed and high-acceleration) maneuvers have attracted significant attention in the past few years. This article focuses on accurate tracking of aggressive quadcopter trajectories. We propose a novel control law for tracking of position and yaw angle and their derivatives of up to fourth order, specifically velocity, acceleration, jerk, and snap along with yaw rate and yaw acceleration. Jerk and snap are tracked using feedforward inputs for angular rate and angular acceleration based on the differential flatness of the quadcopter dynamics. Snap tracking requires direct control of body torque, which we achieve using closed-loop motor speed control based on measurements from optical encoders attached to the motors. The controller utilizes incremental nonlinear dynamic inversion (INDI) for robust tracking of linear and angular accelerations despite external disturbances, such as aerodynamic drag forces. Hence, prior modeling of aerodynamic effects is not required. We rigorously analyze the proposed control law through response analysis and demonstrate it in experiments. The controller enables a quadcopter UAV to track complex 3-D trajectories, reaching speeds up to 12.9 m/s and accelerations up to 2.1 g, while keeping the root-mean-square tracking error down to 6.6 cm, in a flight volume that is roughly 18 m ×7 m and 3-m tall. We also demonstrate the robustness of the controller by attaching a drag plate to the UAV in flight tests and by pulling on the UAV with a rope during hover.

Hard-magnetic elastica

Recently, ferromagnetic soft continuum robots – a type of slender, thread-like robots that can be steered magnetically – have demonstrated the capability to navigate through the brain's narrow and winding vasculature, offering a range of captivating applications such as robotic endovascular neurosurgery. Composed of soft polymers with embedded hard-magnetic particles as distributed actuation sources, ferromagnetic soft continuum robots produce large-scale elastic deflections through magnetic torques and/or forces generated from the intrinsic magnetic dipoles under the influence of external magnetic fields. This unique actuation mechanism based on distributed intrinsic dipoles yields better steering and navigational capabilities at much smaller scales, which differentiate them from previously developed continuum robots. To account for the presence of intrinsic magnetic polarities, this emerging class of magnetic continuum robots provides a new type of active structure – hard-magnetic elastica – which means a thin, elastic strip or rod with hard-magnetic properties. In this work, we present a nonlinear theory for hard-magnetic elastica, which allows accurate prediction of large deflections induced by the magnetic body torque and force in the presence of an external magnetic field. From our model, explicit analytical solutions can be readily obtained when the applied magnetic field is spatially uniform. Our model is validated by comparing the obtained solutions with both experimental results and finite element simulations. The validated model is then used to calculate required magnetic fields for the robot's end tip to reach a target point in space, which essentially is an inverse problem challenging to solve with a linear theory or finite-element simulation. Providing facile routes to analyze nonlinear behavior of hard-magnetic elastica, the presented theory can be used to guide the design and control of the emerging class of magnetically steerable soft continuum robots.

Numerical study of millimeter-scale magnetorheological elastomer robot for undulatory swimming

Numerical investigations of magnetorheological elastomer millimeter-scale robots capable of undulatory swimming under magnetic body torques are realized for the first time in low Reynolds number conditions. The simulated results agree well with reported experimental results under the same conditions. The countermovement of the robots increases as the enhancement of magnetic field strength and the reduction of the length of the robots. The swimming gaits of the robots are characterized by a proposed theoretical function differing obviously from Taylor’s model. The amplitudes of the points along the neutral layer are inconsistent. These simulations provide rapid and low-cost investigation methods for soft-bodied locomotion actuated by distributed torques.

Physical Realization of Elastic Cloaking with a Polar Material.

An elastic cloak is a coating material that can be applied to an arbitrary inclusion to make it indistinguishable from the background medium. Cloaking against elastic disturbances, in particular, has been demonstrated using several designs and gauges. None, however, tolerate the coexistence of normal and shear stresses due to a shortage of physical realization of transformation-invariant elastic materials. Here, we overcome this limitation to design and fabricate a new class of polar materials with a distribution of body torque that exhibits asymmetric stresses. A static cloak for full two-dimensional elasticity is thus constructed based on the transformation method. The proposed cloak is made of a functionally graded multilayered lattice embedded in an isotropic continuum background. While one layer is tailored to produce a target elastic behavior, the other layers impose a set of kinematic constraints equivalent to a distribution of body torque that breaks the stress symmetry. Experimental testing under static compressive and shear loads demonstrates encouraging cloaking performance in good agreement with our theoretical prediction. The work sets a precedent in the field of transformation elasticity and should find applications in mechanical stress shielding and stealth technologies.

Line-of-sight stabilization of roll-pitch seeker using differentiator-based disturbance compensation control

A new control problem of roll-pitch seeker about the disturbance coupling is investigated in this work. Previous control strategies of roll-pitch seeker rarely considered the effects of the dynamic coupling disturbances from the missile angular motion, and because of the polar coordinate structure, the disturbance rejection strategies of yaw-pitch seeker cannot be utilized directly on roll-pitch seeker. Thus this article presents a new control strategy to improve the disturbance rejection ability of roll-pitch seeker. To analyze the disturbance coupling problem, the roll-pitch seeker model is derived with consideration of the missile body angular motion and torque disturbances. The motion equation of roll-pitch seeker shows that part of the dynamic coupling disturbance can be eliminated by certain choices of inertial parameters. The rest of disturbance is reduced by the stabilization loops using a differentiator-based disturbance compensation controller. Particularly, a missile body angular acceleration estimation method is designed for the compensator based on an adaptive differentiator. In addition, comparisons with other control strategies are carried out via numerical simulations, and the results confirm the effectiveness of the proposed method.

Quantification of the influence of drugs on zebrafish larvae swimming kinematics and energetics.

The use of zebrafish larvae has aroused wide interest in the medical field for its potential role in the development of new therapies. The larvae grow extremely quickly and the embryos are nearly transparent which allows easy examination of its internal structures using fluorescent imaging techniques. Medical treatment of zebrafish larvae can directly influence its swimming behaviours. These behaviour changes are related to functional changes of central nervous system and transformations of the zebrafish body such as muscle mechanical power and force variation, which cannot be measured directly by pure experiment observation. To quantify the influence of drugs on zebrafish larvae swimming behaviours and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. Specifically, by using an in-house MATLAB code to process the recorded live zebrafish swimming video, the kinematic locomotion equation of a 3D zebrafish larvae was obtained, and a customised Computational Fluid Dynamics tool was used to solve the fluid flow around the fish model which was geometrically the same as experimentally tested zebrafish. The developed methodology was firstly verified against experiment, and further applied to quantify the fish internal body force, torque and power consumption associated with a group of normal zebrafish larvae vs. those immersed in acetic acid and two neuroactive drugs. As indicated by our results, zebrafish larvae immersed in 0.01% acetic acid display approximately 30% higher hydrodynamic power and 10% higher cost of transport than control group. In addition, 500 μM diphenylhydantoin significantly decreases the locomotion activity for approximately 50% lower hydrodynamic power, whereas 100 mg/L yohimbine has not caused any significant influences on 5 dpf zebrafish larvae locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behaviour changes and thus support the development of new analgesic and neuroactive drugs.

An asymmetric elastic metamaterial model for elastic wave cloaking

Elastic material with its elastic tensor losing minor symmetry is considered impossible without introducing artificially body torque. Here we demonstrate the feasibility of such material by introducing rotational resonance, the amplified rotational inertia of the microstructure during dynamical loading breaks naturally the shear stress symmetry, without resorting to external body torque or any other active means. This concept is illustrated through a realistic mass-spring model together with analytical homogenization technique and band structure analysis. It is also proven that this metamaterial model can be deliberately tuned to meet the material requirement defined by transformation method for full control of elastic wave, and the relation bridging the microstructure and the desired wave functionality is explicitly given. Application of this asymmetric metamaterial to design elastic wave cloak is demonstrated and validated by numerical simulation. The study paves the way for material design used to construct the transformation media for controlling elastic wave and related devices.

How to Disengage: Suspension, Body Torque, and Repair

ABSTRACTThis article uses conversation analysis to study other-initiated repair in multiactivity situations. The article focuses on two aspects of the repair initiator’s embodied conduct directly connected to the initiator’s involvement in multiactivity: body torque and the suspension of a parallel manual activity. The analysis reveals how the body torque and suspension of manual activity, when co-occurring with other-initiations of repair, display the OIR-speaker’s temporary disengagement from the manual activity and how this embodied conduct communicates downward prioritization of the manual activity and increased involvement in the interaction. This article shows that, to participants in a conversation and simultaneously involved in multiactivity, solving interactional trouble is prioritized over the progression of the parallel manual task and that this hierarchization of activities displays a strong preference toward restoration and maintenance of intersubjectivity. Data are in English and in French with English translation.

Efeito do treinamento com restrição parcial do fluxo sanguíneo em adultos mais velhos e idosos: uma revisão sistemática

Low-intensity training with blood flow restriction (BFR) has been suggested as an alternative to physical training for older adults. The present study aimed to review the literature regarding the effect of training with BFR for older adults. The search strategyconsisted of experimental studies aimed at verifying the effects of training with BFR on any outcome in older adults. An electronic search in PubMed / Medline, Bireme Scielo, Lilacs and Cochrane Library databases, published until December 2015 was conducted. Experimental studies that considered individuals aged 50 years and over published in English or Portuguese, were included. The Downs &amp; Black scale was used to assess the methodological quality of articles. Of the 60 studies, 12 were included in the review. Training with BFR improved body mass, torque and muscle power; functional capacity; bone health; venous compliance; peak oxygen uptake; and blood flow; balance and overall performance. The methodological quality of studies had mean score of 16.2 points (SD = 1.6). The prescription of low-intensity exercises with BFR may be an alternative of training for older adults. However, future studies should address the methodological quality, especially external validity and power, the main gaps in articles reviewed in this study.

Efeito do treinamento com restrição parcial do fluxo sanguíneo em adultos mais velhos e idosos: uma revisão sistemática

Low-intensity training with blood flow restriction (BFR) has been suggested as an alternative to physical training for older adults. The present study aimed to review the literature regarding the effect of training with BFR for older adults. The search strategyconsisted of experimental studies aimed at verifying the effects of training with BFR on any outcome in older adults. An electronic search in PubMed / Medline, Bireme Scielo, Lilacs and Cochrane Library databases, published until December 2015 was conducted. Experimental studies that considered individuals aged 50 years and over published in English or Portuguese, were included. The Downs & Black scale was used to assess the methodological quality of articles. Of the 60 studies, 12 were included in the review. Training with BFR improved body mass, torque and muscle power; functional capacity; bone health; venous compliance; peak oxygen uptake; and blood flow; balance and overall performance. The methodological quality of studies had mean score of 16.2 points (SD = 1.6). The prescription of low-intensity exercises with BFR may be an alternative of training for older adults. However, future studies should address the methodological quality, especially external validity and power, the main gaps in articles reviewed in this study.

Acute Caffeine Ingestion Enhances Upper and Lower Body Torque During Isometric and Isokinetic Muscle Actions

Acute Caffeine Ingestion Enhances Upper and Lower Body Torque During Isometric and Isokinetic Muscle Actions

Three-Degree-of-Freedom Estimation of Agile Space Objects Using Marginalized Particle Filters

Several innovations are introduced for space object attitude estimation using light-curve measurements. A radiometric measurement noise model is developed to define the observation uncertainty in terms of optical, environmental, space object, and sensor parameters and is validated using experimental data. Additionally, a correlated process noise model is introduced to represent the angular acceleration dynamics. This model is used to account for the unknown inertia and body torques of agile space objects. This linear dynamics model enables the implementation of marginalized particle filters, affording computationally tractable three-degree-of-freedom Bayesian estimation. The synthesis of these novel approaches enables the estimation of attitude and angular velocity states of maneuvering space objects without a priori knowledge of initial attitude while maintaining computational tractability. Simulated results are presented for the full three-degree-of-freedom agile space object attitude estimation problem.

バックステッピング法と最適サーボ系の組み合わせによるシングルロータヘリの高速旋回飛行制御系の設計とその実験的検証

Aiming at the realization of agile autonomous flight for the extension of the flying range of single-rotor helicopters in the limited flight time, the flight control system design and the control performance verification for the high-speed turn flight are conducted. To achieve the reference following control for large attitude angles and the rotor thrust, the control system is composed of the main-rotor thrust and body torque centralized controller based on the MIMO (Multiple-Input, Multiple-Output) helicopter model including the blade motion dynamics, rotor speed proportional-integral controller, the attitude controller designed via the backstepping method based on the quaternion attitude model, and the guidance controller based on translational motion model. Simulation results show that the hovering and 10-m/s straight cruise flight followed by over 45-degree bank turn is feasible by using the proposed control system. In addition, flight tests have been conducted using the experimental small unmanned electric helicopter equipped with the flight control computer, and the high speed turn agile autonomous flight was successful in the real environment.

Traction Enhancing Products Affect Maximum Torque at the Shoe-Floor Interface: A Potential Increased Risk of ACL Injury

The knee is one of the most frequently injured joints in the body, between 100 000 and 400 000 Anterior Cruciate Ligament (ACL) injuries occur in the United States each year. This investigation explores the impact of wipe- or spray-on sneaker products used to increase traction between shoes and hardwood courts on the loading of the ACL. Specifically, the maximum torque achieved prior to the sneaker slipping on the court surface is measured using a servo-hydraulic bi-axial load frame. A prosthetic foot fitted into a sneaker was fixed to the load cell and a piece of hardwood court was fixed to the actuator of the load frame. Axial loads were applied to simulate an athlete's body weight and torques were applied to simulate an athlete pivoting on a hardwood surface. The maximum torque achieved prior to the sneaker slipping on the hardwood surface was measured. The investigation finds that the application of the wipe- or spray-on sneaker products increases the maximum torque achieved prior to the sneaker slipping by 164%. This increase in torque exceeds prior published levels of torque that resulted in ACL failure in a cadaveric model.