Force Generation Capability Research Articles

Design and evaluation of a continuum robot with extendable balloons

Abstract. This article presents the design and preliminary evaluation of a novel continuum robot actuated by two extendable balloons. Extendable balloons are utilized as the actuation mechanism of the robot, and they are attached to the tip from their slack sections. These balloons can extend very much in length without having a significant change in diameter. Employing two balloons in an axially extendable, radially rigid flexible shaft, radial strain becomes constricted, allowing high elongation. As inflated, the balloons apply a force on the wall of the tip, pushing it forward. This force enables the robot to move forward. The air is supplied to the balloons by an air compressor and its flow rate to each balloon can be independently controlled. Changing the air volumes differently in each balloon, when they are radially constricted, orients the robot, allowing navigation. Elongation and force generation capabilities and pressure data are measured for different balloons during inflation and deflation. Afterward, the robot is subjected to open field and maze-like environment navigation tests. The contribution of this study is the introduction of a novel actuation mechanism for soft robots to have extreme elongation (2000 %) in order to be navigated in substantially long and narrow environments.

The Efficacy of Wrestling-Style Compression Suits to Improve Maximum Isometric Force and Movement Velocity in Well-Trained Male Rugby Athletes.

Purpose: The prevalence of compression garment (CG) use is increasing with athletes striving to take advantage of the purported benefits to recovery and performance. Here, we investigated the effect of CG on muscle force and movement velocity performance in athletes.Methods: Ten well-trained male rugby athletes wore a wrestling-style CG suit applying 13–31 mmHg of compressive pressure during a training circuit in a repeated-measures crossover design. Force and velocity data were collected during a 5-s isometric mid-thigh pull (IMTP) and repeated countermovement jump (CMJ), respectively; and time to complete a 5-m horizontal loaded sled push was also measured.Results: IMTP peak force was enhanced in the CG condition by 139 ± 142 N (effect size [ES] = 0.36). Differences in CMJ peak velocity (ES = 0.08) and loaded sled-push sprint time between the conditions were trivial (ES = −0.01). A qualitative assessment of the effects of CG wear suggested that the likelihood of harm was unlikely in the CMJ and sled push, while a beneficial effect in the CMJ was possible, but not likely. Half of the athletes perceived a functional benefit in the IMTP and CMJ exercises.Conclusion: Consistent with other literature, there was no substantial effect of wearing a CG suit on CMJ and sprint performance. The improvement in peak force generation capability in an IMTP may be of benefit to rugby athletes involved in scrummaging or lineout lifting. The mechanism behind the improved force transmission is unclear, but may involve alterations in neuromuscular recruitment and proprioceptive feedback.

Increased cross-bridge recruitment contributes to transient increase in force generation beyond maximal capacity in human myocardium

Cross-bridge attachment allows force generation to occur, and rate of tension redevelopment (ktr) is a commonly used index of cross-bridge cycling rate. Tension overshoots have been observed briefly after a slack-restretch ktr maneuver in various species of animal models and humans. In this study, we set out to determine the properties of these overshoots and their possible underlying mechanism. Utilizing human cardiac trabeculae, we have found that tension overshoots are temperature-dependent and that they do not occur at resting states. In addition, we have found that myosin cross-bridge cycle is vital to these overshoots as inhibition of the cycle results in the blunting of the overshoots and the magnitude of the overshoots are dependent on the level of myofilament activation. Lastly, we show that the number of cross-bridges transiently increase during tension overshoots. These findings lead us to conclude that tension overshoots are likely due to a transient enhancement of the recruitment of myosin heads into the cross-bridge cycling, regulated by the myocardium, and with potential physiological significance in determining cardiac output. News and noteworthyWe show that isolated human myocardium is capable of transiently increasing its maximal force generation capability by increasing cross-bridge recruitment following slack-restretch maneuver. This process can potentially have important implications and significance in cardiac contraction in vivo.

The Effect of Short-term Muscle Vibration on Knee Joint Torque and Muscle Firing Patterns during a Maximal Voluntary Isometric Contraction

Objective: To investigate the effect of short-term vibration frequencies on muscle force generation capabilities. Method: Six healthy participants were recruited for this study and only their dominant leg was tested. The subjects were tested under five conditions of vibration frequencies with constant amplitude: 0 Hz (no vibration), 30 Hz, 60 Hz, and 90 Hz, and the vibration amplitude was 10 mm for all frequency conditions. The vibration was applied to the rectus femoris (RF). The subjects were then instructed to maintain a steadystate isometric knee joint torque (100 Nm) for the first 6 s. After the steady-state torque production, the subjects were required to produce isometric knee joint torque by leg extension as hard as possible with a start signal within the next 3 s. The vibration was applied for ~4 s starting from 1 s before initiation of the change in the steady-state knee joint torque. Results: The results showed that the maximum voluntary torque (MVT) of the knee joint increased with the vibration frequencies. On average, the MVTs were 756.47 Nm for 0 Hz (no vibration) and 809.61 Nm for 90 Hz. There was a significant positive correlation (r = 0.71) between the MVTs and integrated electromyograms (iEMGs). Further, the co-contraction indices (CCIs) were computed, which represent the ratio of the iEMGs of the antagonist muscle to the iEMGs of all involved muscles. There was a significant negative correlation (r = 0.62) between the CCIs and MVTs, which was accompanied by a significant positive correlation (r = 0.69) between the iEMGs of the vibrated muscle (RF). There was no significant correlation between the MVTs and iEMGs of the antagonist muscle. Conclusion: The results of this study suggest that the short-term vibration on the muscle increases the level of muscle activation possibly owing to the increased Ia afferent activities, which enhances the muscle force generation capability.

Evaluation of the integration of the Wind-Induced Flutter Energy Harvester (WIFEH) into the built environment: Experimental and numerical analysis

With the ubiquity of low-powered technologies and devices in the urban environment operating in every area of human activity, the development and integration of a low-energy harvester suitable for smart cities applications is indispensable. The multitude of low-energy applications extend from wireless sensors, data loggers, transmitters and other small-scale electronics. These devices function in the microWatt-milliWatt power range and will play a significant role in the future of smart cities providing power for extended operation with little or no battery dependence. This study thus aims to investigate the potential built environment integration and energy harvesting capabilities of the Wind-Induced Flutter Energy Harvester (WIFEH) – a microgenerator aimed to provide energy for low-powered applications. Low-energy harvesters such as the WIFEH are suitable for integration with wireless sensors and other small-scale electronic devices; however, there is a lack in study on this type of technology’s building integration capabilities. Hence, there is a need for investigating its potential and optimal installation conditions.This work presents the experimental investigation of the WIFEH inside a wind tunnel and a case study using Computational Fluid Dynamics (CFD) modelling of a building integrated with a WIFEH system. The experiments tested the WIFEH under various wind tunnel airflow speeds ranging from 2.3 to 10m/s to evaluate the induced electromotive force generation capability of the device. The simulation used a gable-roof type building model with a 27° pitch obtained from the literature. The atmospheric boundary layer (ABL) flow was used for the simulation of the approach wind. The work investigates the effect of various wind speeds and WIFEH locations on the performance of the device giving insight on the potential for integration of the harvester into the built environment. The WIFEH was able to generate an RMS voltage of 3V, peak-to-peak voltage of 8.72V and short-circuit current of 1mA when subjected to airflow of 2.3m/s. With an increase of wind velocity to 5m/s and subsequent membrane retensioning, the RMS and peak-to-peak voltages and short-circuit current also increase to 4.88V, 18.2V, and 3.75mA, respectively. For the CFD modelling integrating the WIFEH into a building, the apex of the roof of the building yielded the highest power output for the device due to flow speed-up maximisation in this region. This location produced the largest power output under the 45° angle of approach, generating an estimated 62.4mW of power under accelerated wind in device position of up to 6.2m/s. For wind velocity (UH) of 10m/s, wind in this position accelerated up to approximately 14.4m/s which is a 37.5% speed-up at the particular height. This occurred for an oncoming wind 30° relative to the building facade. For UH equal to 4.7m/s under 0° wind direction, airflows in facade edges were the fastest at 5.4m/s indicating a 15% speed-up along the edges of the building.

A Pole Pair Segment of a 2-MW High-Temperature Superconducting Wind Turbine Generator

A 2-MW high-temperature superconducting (HTS) generator with 24 pole pairs has been designed for the wind turbine application. In order to identify potential challenges and obtain practical knowledge prior to production, a full-size stationary experimental setup, which is one pole pair segment of the full generator, has been built and tested. The experimental setup comprises a consequent-pole HTS rotor and a conventional three-phase copper stator. This paper first presents the electromagnetic designs of the full generator and the setup, then it goes to compare the performance of the full generator and the setup in terms of the flux density, the operating condition of the HTS winding, and the force-generation capability. Finite element (FE) software MagNet is used to carry out numerical simulations. The findings show that the HTS winding in the setup is a good surrogate for these that would be used in the full generator. The FE simulations also tell that the maximum tangential force generated in the setup is 3.77% lower than that in the full generator. Good agreement between the values of interest in the setup and those projected in the full generator has revealed a cost-effective prototyping methodology for developing HTS machines.

Actively Controlled Hexapole Electromagnetic Actuating System Enabling 3-D Force Manipulation in Aqueous Solutions

This paper presents the design, modeling, and calibration of an overactuated and actively controlled hexapole electromagnetic actuating system, which is implemented to stabilize and propel a microscopic magnetic particle in aqueous solutions. Compared to the 2-D quadruple magnetic tweezers in the paper by Zhang et al. ( IEEE/ASME Trans. Mechatronics , 2010) and the 3-D magnetic actuator in the paper by Zhang and Menq ( IEEE/ASME Trans. Mechatronics , 2011), the new electromagnetic actuating system achieves significantly greater force generation capability and much improved controllability of 3-D force in the workspace. These improvements are accomplished through enhanced design and synthesis of the six electromagnetic poles and improved current allocation of the overactuated system. A lumped parameter hexapole force model of the system is derived and validated through experimental calibration. It is then used to devise inverse modeling, which is implemented to realize real-time current allocation to enable the most effective manipulation of the 3-D magnetic force exerting on the particle at the center of the workspace. The system is designed for use with live cell experiments.

Electromechanical performance of chitosan-based composite electroactive actuators

A novel chitosan-based electroactive actuator was fabricated by using chitosan, N, N′-methylenebisacrylamide (MBA), poly (diallyldimethylammonium chloride), and gold metal. The constructive effect of crosslinker to the actuator performance was investigated by using various amounts of MBA. The chitosan-based film samples were characterized using Fourier transform infrared analyses, X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy analysis, and tensile test. The viscoelastic properties of films were determined by dynamic mechanical analysis. The motion and force generation capabilities and the repeatability of the actuators were also investigated under electrical stimuli up to 21 V. The suitability of the prepared chitosan-based films to be used as actuator for soft robotic applications is verified experimentally.

Constant-Strain Thermal Cycling of a Ni50.3Ti29.7Hf20 High-Temperature Shape Memory Alloy

The effect of various pre-straining routines on the recovery stresses of a Ni-rich Ni50.3Ti29.7Hf20 high-temperature shape memory alloy was investigated in tension and compression. The recovery stresses, obtained by means of constant-strain thermal cycling, were evaluated after isothermal (up to ±2 % applied strain at room temperature) or after isobaric thermal cycling at stress levels between ±100 and 400 MPa. The material exhibited high force generation capability with recovery stresses of nearly 1.5 GPa on the first cycle under particular pre-strain conditions. The recovery stresses are shown to decay during subsequent cycles using an upper cycle temperature of 300 °C with a saturated stress level nearing 1.1 GPa in compression.

Design and characterization of a microelectromechanical system electro-thermal linear motor with interlock mechanism for micro manipulators.

The design, fabrication, and testing of a novel electro-thermal linear motor for micro manipulators is presented in this paper. The V-shape electro-thermal actuator arrays, micro lever, micro spring, and slider are introduced. In moving operation, the linear motor can move nearly 1 mm displacement with 100 μm each step while keeping the applied voltage as low as 17 V. In holding operation, the motor can stay in one particular position without consuming energy and no creep deformation is found. Actuation force of 12.7 mN indicates the high force generation capability of the device. Experiments of lifetime show that the device can wear over two million cycles of operation. A silicon-on-insulator wafer is introduced to fabricate a high aspect ratio structure and the chip size is 8.5 mm × 8.5 mm × 0.5 mm.

Sex difference in age-related changes in knee extensor strength and power production during a 10-times-repeated sit-to-stand task in Japanese elderly.

BackgroundFor middle-aged and elderly women, age-related decline in an index representing power production during STS task (STS-PI), calculated by using an equation reported previously, has been shown to be greater than that in the force generation capability of lower extremity. Whether this is specific to women remains unclear. This study examined how the age-related changes in knee extensor strength and power production during STS differ between Japanese men and women aged 65 years or older.MethodsThe time taken for a 10-times-repeated STS test (STS time) and force developed during maximal voluntary isometric knee extension (KE-F) were determined in Japanese younger-old (262 men and 285 women) aged 65–74 years and older-old (96 men and 89 women) aged 75–90 years. STS-PI was calculated using the following equation: STS-PI = (body height − 0.4) × body mass × 10/STS time.ResultsKE-F and STS-PI were significantly greater in the younger-old than in the older-old group (p < 0.0001) and in men than in women (p < 0.0001). STS-PI and KE-F, expressed as the percentages of the mean value of the corresponding variable for the younger-old group (%STS-PI and %KE-F, respectively), were negatively correlated to chronological age in both men (r = −0.386 and r = −0.269, respectively, p < 0.0001) and women (r = −0.504 and r = −0.294, respectively, p < 0.0001). Regression slopes in the relationship between age and %KE-F were not significantly different between men (−1.521) and women (−1.618). However, regression slope in the relationship between age and %STS-PI was significantly steeper in women (−3.108) than in men (−2.170) (p < 0.05). In OOG, %KE-F had no significant effect of sex, but %STS-PI was significantly lower in women than in men (p < 0.001).ConclusionsIn Japanese men and women aged 65 years or over, age-related loss in power production during STS is steeper in women than in men, with greater magnitude than that in knee extensor strength. This suggests a higher priority of improving power generation capability during whole-body movement such as STS in older women than in older men.

Formation of helical membrane tubes around microtubules by single-headed kinesin KIF1A

The kinesin-3 motor KIF1A is in charge of vesicular transport in neuronal axons. Its single-headed form is known to be very inefficient due to the presence of a diffusive state in the mechanochemical cycle. However, recent theoretical studies have suggested that these motors could largely enhance force generation by working in teams. Here we test this prediction by challenging single-headed KIF1A to extract membrane tubes from giant vesicles along microtubule filaments in a minimal in vitro system. Remarkably, not only KIF1A motors are able to extract tubes but they feature a novel phenomenon: tubes are wound around microtubules forming tubular helices. This finding reveals an unforeseen combination of cooperative force generation and self-organized manoeuvreing capability, suggesting that the diffusive state may be a key ingredient for collective motor performance under demanding traffic conditions. Hence, we conclude that KIF1A is a genuinely cooperative motor, possibly explaining its specificity to axonal trafficking.

Muscle architecture of the forelimb of the Golden Pheasant (Chrysolophus pictus) (Aves: Phasianidae) and its implications for functional capacity in flight

BackgroundFlight is the central avian adaptation in evolution. Wing muscles form an important anatomical basis for avian flight, affecting wing performance and determine modes of flight. However, the roles of distal muscles in adjusting the wing, as well as their functional specializations, remain largely unknown. The importance of muscle fiber architecture has long been recognized. In this study, we provide quantitative anatomical data on the muscle architecture of the forelimb of the Golden Pheasant (Chrysolophus pictus), with an emphasis on brachial, antebrachial and manual segments.MethodsThe forelimbs of five Golden Pheasants were dissected and detailed measurements of all muscles were made, including muscle mass, muscle belly length, fascicle length. From these values, muscle volume, physiological cross-sectional area (PCSA) and maximum isometric force were derived.ResultsGeneral trends such as the distribution of muscle mass, fascicle length and the ratio of tendon length/belly length are revealed. Comparing PCSAs between antebrachial depressors and elevators and between intrinsics of the alular digit and major digit yielded significant differences (p < 0.05). Pronounced development of the antebrachial depressors suggests that ventral rotation of the distal half of the wing is a pivotal factor in shape change and orientation modulation. Large PCSAs in tandem with the force generation capability of the major digit intrinsics may help stabilize the digits while enhancing support of the primary feathers. The architectural properties of the alular digit confirm that alular adjustment is essential to rapid adduction and abduction.ConclusionsThese observations illustrate the underlying structural basis for the functional capacities of the distal forelimb muscles and may provide additional information useful in further biomechanical and in vivo investigations.

Impact of familial hypertrophic cardiomyopathy-linked mutations in the NH2 terminus of the RLC on β-myosin cross-bridge mechanics.

Familial hypertrophic cardiomyopathy (HCM) is associated with mutations in sarcomeric proteins, including the myosin regulatory light chain (RLC). Here we studied the impact of three HCM mutations located in the NH2 terminus of the RLC on the molecular mechanism of β-myosin heavy chain (MHC) cross-bridge mechanics using the in vitro motility assay. To generate mutant β-myosin, native RLC was depleted from porcine cardiac MHC and reconstituted with mutant (A13T, F18L, and E22K) or wild-type (WT) human cardiac RLC. We characterized the mutant myosin force and motion generation capability in the presence of a frictional load. Compared with WT, all three mutants exhibited reductions in maximal actin filament velocity when tested under low or no frictional load. The actin-activated ATPase showed no significant difference between WT and HCM-mutant-reconstituted myosins. The decrease in velocity has been attributed to a significantly increased duty cycle, as was measured by the dependence of actin sliding velocity on myosin surface density, for all three mutant myosins. These results demonstrate a mutation-induced alteration in acto-myosin interactions that may contribute to the pathogenesis of HCM.

Convergent field elastography

An ultrasound-based system for non-invasive estimation of soft tissue shear modulus will be presented. The system uses a nested pair of transducers to provide force generation and motion measurement capabilities. The outer annular element produces a ring-like ultrasonic pressure field distribution. This in turn produces a ring-like force distribution in soft tissue, whose response is primarily observable as a shear wave field. A second ultrasonic transducer nested inside the annular element monitors the portion of the shear field that converges to the center of the force distribution pattern. Propagation speed is estimated from shear displacement phase changes resulting from dilation of the forcing radius. Forcing beams are modulated in order to establish shear speed frequency dependence. Prototype system data will be presented for depths of 10–14 cm in a tissue phantom, using drive parameters within diagnostic ultrasound safety limits. [Work supported by ONR and the Neely Chair in Mechanical Engineering, Georgia Institute of Technology.]

Age-related change in sit-to-stand power in Japanese women aged 50 years or older.

BackgroundThis study examined whether the age-related change in power, calculated from the score of a sit-to-stand (STS) test, corresponds to those in knee extension torque and leg lean tissue mass in Japanese women aged 50 years or older.FindingsTime for a 10-times-repeated STS test and knee extension torque were determined in 556 Japanese women aged 50 to 94 years. STS power was calculated using an equation reported previously. In addition, leg lean tissue mass was estimated using muscle thicknesses determined at thigh and lower leg. STS power, knee extension torque, and lean tissue mass were negatively correlated to age. STS power and knee extension torque, expressed as the percentages of the mean value of the corresponding variable for the subjects aged 50 to 54 years were lower than that of lean tissue mass in the subjects aged 60 years or over, and were similar in those aged under 75 years. However, the relative value of STS power was lower than that of knee extension torque in the subjects aged over 75 years.ConclusionsIn Japanese women aged 50 to 74 years, STS power can be a convenient measure for assessing the age-related decline in knee extension torque, but not for leg lean tissue mass. At over 75 years old, the magnitude of the age-related decline in STS power does not parallel to that in the force generation capability of knee extensor muscles.

Invited Commentary

Invited Commentary

Impact of Familial Hypertrophic Cardiomyopathy-Linked Mutations in the N-Terminus of the RLC on β-Myosin Cross-Bridge Mechanics

Familial Hypertrophic Cardiomyopathy (FHC) is associated with mutations in sarcomeric proteins of which myosin regulatory light chain (RLC) is included. Here we studied the impact of the N-terminal FHC mutations on the molecular mechanism of β-Myosin heavy chain cross-bridge mechanics using the in vitro motility assay. To generate mutant β-Myosin, native pig RLC was depleted from porcine cardiac myosin heavy chain and reconstituted with mutant (A13T, F18L & E22K) or wild-type human RLC. We characterized the mutant myosin force and motion generation capability in the presence of a frictional load and thin filament regulatory proteins. All three mutants exhibited reductions in maximal filament velocity when tested with both calcium-regulated (40.5% ± 1.07, 28.9% ± 1.11, & 24.5% ± 1.14 A13T, F18L & E22K resp.) and unregulated filament (34.4% ± 0.8, 19.1% ± 0.9 & 5.6% ± 0.9 resp.) compared to wild-type. Furthermore, all three mutants displayed reductions in calcium sensitivity (pCa 50) (∼5.13%, ∼6.52% & ∼4.50% resp.) as well as cooperative activation (∼22%, ∼42% & ∼34% resp.) of regulated velocity. These results suggest that the known FHC mutants on the N-terminus of the RLC affect formation of strong binding cross-bridges thereby reducing maximal force production. This work is supported by grants to the following people HL077280 (JM) HL071778 (D S-C).

Cardiac Myosin Binding-Protein C (cMyBP-C) Phosphorylation affect Cross-Bridge Function

To understand the functional significance of phosphorylation that takes place in the M domain of cMyBP-C, chemically skinned papillary muscle fibers of transgenic mice were studied by sinusoidal length alterations and concomitant tension transients. Muscle fibers were maximally activated at pCa 4.55 in the solution that mimic physiological conditions (5 mM MgATP, 8 mM Pi, 200 mM total ionic strength with K-acetate) in myocytes. WT mice possess phosphorylation sites S273, S282, and S302. SAS is a single mutant S282A, and ADA and DAD are triple mutants S273A/S282D/S302A and S273D/S282A/S302D, respectively. D models for phosphorylation (phosphomimetic), and A models for non-phosphorylation (phosphor-ablation). Isometric tension and stiffness of DAD were respectively ∼0.5x of those of WT, but tension and stiffness of t/t (cMyBP-C null), ADA, and SAS were respectively similar to WT. The fast rate constant 2πc of DAD and t/t was ∼0.6x of WT, but that of ADA and SAS was similar to WT. The intermediate rate constant 2πb of DAD and SAS was ∼1.3x of WT, but that of ADA and t/t was similar to WT. These results demonstrate that cMyBP-C M domain phosphorylation affects the cross-bridge kinetics at ATP binding and phosphate release steps, indicating that phosphorylation affects myosin structure and its interaction with actin. However, pCa-tension and pCa-stiffness studies demonstrated that pCa50 (Ca2+ sensitivity) and nH (cooperativity) were respectively not different among mutants and WT groups, indicating that phosphorylation of cMyBP-C has a minimal effect on the regulatory system. The decreased amount of isometric tension only in DAD indicates that phosphorylation of S273 and S302 are most significant and they diminish the force generation capability, presumably owing to the extra electrostatic interaction of the M domain of cMyBP-C with actin thin filament, which may serve as a break.

Electrothermal Microactuators With Peg Drive Improve Performance for Brain Implant Applications

This paper presents a new actuation scheme for in-plane bidirectional translation of polysilicon microelectrodes. The new Chevron-peg actuation scheme uses microelectromechanical systems (MEMS) based electrothermal microactuators to move microelectrodes for brain implant applications. The design changes were motivated by specific needs identified by the in vivo testing of an earlier generation of MEMS microelectrodes that were actuated by the Chevron-latch type of mechanism. The microelectrodes actuated by the Chevron-peg mechanism discussed here show improved performance in the following key areas: higher force generation capability (111 μN per heat strip compared to 50 μN), reduced power consumption (91 mW compared to 360 mW), and reliable performance with consistent forward and backward movements of microelectrodes. Failure analysis of the Chevron-latch and the Chevron-peg type of actuation schemes showed that the latter is more robust to wear over four million cycles of operation. The parameters for the activation waveforms for Chevron-peg actuators were optimized using statistical analysis. Waveforms with a 1-ms time period and a 1-Hz frequency of operation showed minimal error between the expected and the actual movement of the microelectrodes. The new generation of Chevron-peg actuators and microelectrodes are therefore expected to enhance the longevity and performance of implanted microelectrodes in the brain. [2011-0341].