Inversion Motion Research Articles

Effect of Tangential Loading History on Static Friction Force of Elastic Slider with Split Contact Surface: Model Calculation

This study provides a novel insight into the study of static friction force. From numerical simulations with a simplified sliding model in which the friction force between an elastic slider with a split contact interface and a rigid base block with a smooth surface was analyzed, it was found that the existence of the stop–restart motion works to increase static friction force, while the stop–inversion motion reduces static friction force. Thus, the numerical simulations in this study demonstrated that the magnitude of static friction force varies with different types of tangential loading sequences. Furthermore, it was found from an analytical discussion that the magnitude of this tangential loading history effect is characterized by the dispersion level of the threshold lengths for the onset of slip motion at each contact point and also by the ratio of kinetic friction coefficient to static friction coefficient at the contact interface. Through the previously mentioned analytical approaches, this study emphasizes that the sequence of tangential loading is an important factor for characterizing the magnitude of static friction force.

5 節球面パラレル機構の逆運動学と運動伝達性の解析

5 節球面パラレル機構の逆運動学と運動伝達性の解析

How to Deploy a Wire with a Robotic Platform: Learning from Human Visual Demonstrations

In this paper, we address the problem of deploying a wire along a specific path selected by an unskilled user. The robot has to learn the selected path and pass a wire through the peg table by using the same tool. The main contribution regards the hybrid use of Cartesian positions provided by a learning procedure and joint positions obtained by inverse kinematics and motion planning. Some constraints are introduced to deal with non-rigid material without breaks or knots. We took into account a series of metrics to evaluate the robot learning capabilities, all of them over performed the targets.

The Steiner Formula and the Polar Moment of Inertia for the Closed Planar Motions in Complex Plane

In this paper, the Steiner area formula and the polar moments of inertia were expressed during one-parameter closed planar motions in complex plane. The Steiner points or Steiner normal concepts were described according to whe-ther rotation number was different from zero or equal to zero. The moving pole point was given with its components and its relation to the Steiner point or Steiner normal which was specified. The Steiner formula and the polar moments of inertia were expressed for the inverse motion. The fixed pole point was calculated for the inverse motion. The sagittal motion of a tele-scopic crane was considered as an example. This motion was described by a double hinge consisting of the fixed control panel of the telescopic crane and its moving arm. The results obtained in the first section of this study were applied to this motion.

On the Kinematics for the Closed Planar Homothetic Inverse Motions in Complex Plane

In this paper, the Steiner area formula and the polar moment of inertia were expressed during one-parameter closed planar homothetic inverse motions in complex plane. The Steiner point was defined when the rotation number was different zero and it was called the Steiner normal when the rotation number was equal to zero. The fixed pole point was given with its components and its relation between Steiner point or Steiner normal was explained. The sagittal motion of a telescopic crane was considered as an example. This motion was described by a double hinge consisting of the fixed control panel of the telescopic crane and the moving arm of the telescopic crane. The theoretical concepts and results were applied for this motion.

Toe-in Landing Increases the Ankle Inversion Angle and Moment During Single-Leg Landing: Implications in the Prevention of Lateral Ankle Sprains.

Identifying the foot positions that are vulnerable to lateral ankle sprains is important for injury prevention. The effects of foot position in the transverse plane on ankle biomechanics during landing are unknown. To examine the effects of toe-in or toe-out positioning on ankle inversion motion and moment during single-leg landing. Repeated measures. Motion analysis laboratory. 18 healthy participants (9 men and 9 women). Participants performed single-leg landing trials from a 30-cm high box under 3 conditions: natural landing, foot internally rotated (toe-in), and foot externally rotated (toe-out). 4 toe-in or toe-out angles were calculated against 4 reference coordinates (laboratory, pelvis, thigh, and shank) in the transverse plane. Ankle inversion angle, angular velocity, and external moment in the 200 ms after initial foot-to-ground contact were compared between the 3 landing conditions. All toe-in or toe-out angles other than those calculated against the shank were significantly different between each of the 3 landing conditions (P < .001). Ankle inversion angle, angular velocity, and moment were highest during toe-in landings (P < .01), while eversion angle and moment were highest during toe-out landings (P < .001). The effect sizes of these differences were large. Vertical ground reaction forces were not different between the 3 landing conditions (P = .290). Toe-in or toe-out positioning during single-leg landings impacts on ankle inversion and eversion motion and moment. Athletes could train not to land with the toe-in positioning to prevent lateral ankle sprains.

Effect of Direct Ligament Repair and Tenodesis Reconstruction on Simulated Subtalar Joint Instability.

Subtalar instability is associated with up to 80% of patients presenting with chronic ankle instability but is often not considered in the diagnosis or treatment. Operative procedures to repair ankle instability have shown good clinical results, but the effects of these reconstruction procedures on isolated subtalar instability are not well understood. The goal of this study was to investigate the effect of the Gould modification of the Broström procedure and a new tenodesis reconstruction procedure on ankle and subtalar joint kinematics after simulating a subtalar injury. Kinematic data were collected on 7 cadaveric ankles during inversion through the range of ankle flexion and during internal rotation. Testing was performed on the intact foot; after sectioning the calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament; after the Gould modification of the Broström procedure was performed; and after tenodesis was performed and sutures from the Gould modification removed. The Gould modification of the Broström procedure significantly decreased subtalar and ankle inversion motion and subtalar internal rotation compared to the unstable condition. The tenodesis method restricted internal rotation at the subtalar joint and ankle inversion compared to the intact state. Both operative procedures improved stability of the ankle complex, but tenodesis was unable to restore subtalar inversion and restricted ankle inversion in maximum plantarflexion. The Gould modification of Broström ligament repair may be a favorable operative procedure for the restoration of subtalar and ankle joint kinematics.

Kinematics-based approach for robot programming via human arm motion

Programming by demonstration approach is becoming an interesting option for programming industrial robots due to the costs involved in the conventional methods for development and maintenance of robot programs. In this approach, the implicit knowledge of human operator is demonstrated through examples that allow robot to learn the skill without being explicitly programmed for every detail. In this paper, a novel approach based on fusion of human arm kinematics with the Kinect-based motion sensing system is proposed for control of robot motion by demonstrating human arm motion. The demonstrated configurations from human workspace are mapped to robot workspace blending concepts of incremental inverse kinematics and Kinect motion sensing system. The proposed approach is implemented for real-time motion control of an industrial robot SCORBOT ER-4u. The performance of the devised strategy is assessed in terms extent of human hand path imitation by the robot end effector in real time. Further, reproducibility and repeatability in path imitation are estimated to ensure the effectiveness of the developed method. The developed kinematic model is validated by comparing its performance with a priori approach. The experimental results indicate that the proposed method is reliable, quick and efficient to teach robot from task demonstrations.

Variation in the preferred movement path while walking barefoot and with minimal shoes on a cross-sloped surface

Document reliability and normative data for a novel device measuring weight-bearing ankle range of motion after ankle injury.Cross-sectional Cohort, two occasions one day apart.Sports medicine hospital.87 ankle-injured male athletes at a late stage of their rehabilitation and 25 uninjured subjects. The injured athletes had met all criteria to return to functional, on-field rehabilitation.Reliability (Intra-Class correlation Coefficient (ICC), and Minimum Detectable Change as a percent of the grand mean), weight-bearing range of motion (degrees) of dorsiflexion, plantarflexion, inversion, and eversion.Good (dorsiflexion = 0.82[0.76–0.87] and inversion = 0.81[0.75–0.86]) and excellent (plantarflexion = 0.93[0.90–0.95]) reliability was documented, however reliability for the eversion measure showed only fair reliability (0.61[0.49–0.70]). Reduced range of motion in the injured leg was seen in all 4 directions, however with different magnitudes: Large differences were plantarflexion (−8.5°, ES = 0.80), medium for dorsiflexion (−5.2°, 0.57), small for inversion (−4.8°, 0.36), and trivial for eversion (−1.7°, 0.15).The device demonstrated clinically useful reliability for measuring these ranges of motion in a functional, weight-bearing position. PF ROM showed the greatest reduction in range in these athletes at a late stage of their rehabilitation.

Corannulene-Helicene Hybrids: Chiral π-Systems Comprising Both Bowl and Helical Motifs.

Two distinct structural elements that render π-systems nonplanar, i.e., geodesic curvature and helical motifs, have been combined into new polyarenes that contain both features. The resultant corannulene-[n]helicenes (n = 5, 6) show unique molecular dynamics in their enantiomerization processes, including inversion motions of both the bowl and the helix. Optical resolution of a corannulene-based skeletally chiral molecule was also achieved for the first time, and the influence of the bowl-motif annulation on the chiroptical properties was investigated.

Reducing the high-temperature loss of steel in furnaces

Assessment of the loss of steel in industrial furnaces may be based on the scale thickness. Means of reducing the oxidation of steel are evaluated. Special attention is paid to the difficulty of reducing the steel loss on account of decrease in the oxidant consumption n. Nonoxidative heating of steel in industrial furnaces is shown to be feasible at present. The requirements here are practically molecular mixing of the components in primary combustion (for natural gas with air excess n = 0.48–0.5); synchronous burner operation and constraints on the oxidation n with regulation of the primary fuel combustion (Δn ≤ 0.01); and effective choking of the primary gas flux so as to rule out inverse circulatory motion of the products of incomplete primary combustion from their combustion zone into the metal-heating zone. Design approaches and operating conditions for forging and rolling furnaces are proposed, so as to reduce or suppress steel losses. Particular attention is paid to the internal high-temperature oxidation of silicon in transformer steel and the decarburizing heating of ball-bearing steel.

Analysis of the similar epicenter earthquakes on 22 January 2013 and 01 June 2013, Central Gulf of Suez, Egypt

On 22 January 2013 an earthquake with local magnitude ML 4.1 occurred in the central part of the Gulf of Suez. Six months later on 1 June 2013 another earthquake with local magnitude ML 5.1 took place at the same epicenter and different depths. These two perceptible events were recorded and localized by the Egyptian National Seismological Network (ENSN) and additional networks in the region.The purpose of this study is to determine focal mechanisms and source parameters of both earthquakes to analyze their tectonic relation. We determine the focal mechanisms by applying moment tensor inversion and first motion analysis of P- and S-waves. Both sources reveal oblique focal mechanisms with normal faulting and strike-slip components on differently oriented faults. The source mechanism of the larger event on 1 June in combination with the location of aftershock sequence indicates a left-lateral slip on N-S striking fault structure in 21 km depth that is in conformity with the NE-SW extensional Shmin (orientation of minimum horizontal compressional stress) and the local fault pattern. On the other hand, the smaller earthquake on 22 January with a shallower hypocenter in 16 km depth seems to have happened on a NE-SW striking fault plane sub-parallel to Shmin. Thus, here an energy release on a transfer fault connecting dominant rift-parallel structures might have resulted in a stress transfer, triggering the later ML 5.1 earthquake.Following Brune’s model and using displacement spectra, we calculate the dynamic source parameters for the two events. The estimated source parameters for the 22 January 2013 and 1 June 2013 earthquakes are fault length (470 and 830 m), stress drop (1.40 and 2.13 MPa), and seismic moment (5.47E+21 and 6.30E+22 dyn cm) corresponding to moment magnitudes of MW 3.8 and 4.6, respectively.

Placement of Composed LED Light Sources for an Inverse Triangulation Motion Capture System with Reflexive Spherical Markers

This paper investigates the problem of composed LED light sources placement for a particular case of motion capture with reflexive spherical markers in Gait Analysis in a controlled lighted environment. After the addressed problem is introduced the way the rays are propagated from the individual LEDs to the pixel array of video camera is computed. Based on this calculus the number of ray hits on distinct pixels is computed for a marker placed in the workspace. Next by varying some scene parameters we obtain the total number of hits on the overall set of makers placed in the scene and based on this number we obtain finally the best placement for the composed LED light sources using an iterative approach.

Decreased Ankle Strength Is Associated With Impaired Postural Balance In Firefighters

One of the leading causes for firefighter injuries reported in the United States is slips, trips and falls suggesting that maintaining postural balance is an important issue in firefighter safety and health. Little information is available about how ankle mobility and strength are affected by strenuous firefighter activity and its consequent influence on postural balance. PURPOSE: To assess changes in functional ankle mobility and strength and a consequent effect on postural balance following firefighter activities. METHODS: Eight healthy men completed a battery of firefighter activity simulations, consisting of uphill walking, weight carrying, crawling, stepping, and dummy dragging, lasting approximately 40 minutes to completion while wearing a full standard firefighter ensemble. Immediately before and after the simulation, subjects were assessed for ankle range of motion (ROM) and isometric peak power (IPP) of plantarflexion, dorsiflexion, inversion, and eversion using an isokinetic dynamometer, and for postural balance to determine overall stability index (OSI) under a dynamic perturbation condition using a Biodex balance system. RESULTS: Ankle ROM did not change significantly, but ankle IPP except dorsiflexion was significantly reduced in POST measurements. There was a significant difference between PRE and POST OSI (0.96±0.52, 1.22±0.80, respectively) (p=0.041). CONCLUSIONS: Decrement in functional ankle ROM was minimal; however, ankle IPP was significantly reduced to which postural stability in a dynamic perturbation condition was impaired. This implicates that ankle fatigue developed due to strenuous firefighter activity is likely an important determinant for impaired postural balance in firefighters.Table: No title available.

Umbrella motion of the methyl cation, radical, and anion molecules

The main purpose of the present work is to characterize the umbrella inversion motion of the CH- 3 , CH3 and CH- 3 molecules as a function of the environmental conditions. In particular, for the three investigated species we have studied how temperature affects times for umbrella inversion modes and their propagation velocity. These data are used to predict the statistical behavior of the reactions involving the AB3 like molecules and to relate the umbrella potential with the rate constants. The second aspect of this study concerns the molecular distribution charges as a function of the umbrella opening angle and of the total charge. The results have been used to calculate the induced electric field on a probe charge located at a given position perpendicular to the plane of the hydrogen atoms which is the most relevant for the reaction. Obtained values are presented as a function of the umbrella opening angle.

Umbrella motion of the methyl cation, radical, and anion molecules

The main purpose of the present work is to characterize the umbrella inversion motion of the CH- 3, CH3 and CH- 3 molecules as a function of the environmental conditions. In particular, for the three investigated species we have studied how temperature affects times for umbrella inversion modes and their propagation velocity. These data are used to predict the statistical behavior of the reactions involving the AB3 like molecules and to relate the umbrella potential with the rate constants. The second aspect of this study concerns the molecular distribution charges as a function of the umbrella opening angle and of the total charge. The results have been used to calculate the induced electric field on a probe charge located at a given position perpendicular to the plane of the hydrogen atoms which is the most relevant for the reaction. Obtained values are presented as a function of the umbrella opening angle.

A MEMS XY-stage integrating compliant mechanism for nanopositioning at sub-nanometer resolution

This paper reports a microelectromechanical systems (MEMS) based XY-stage integrating compliant motion amplification mechanism for nanopositioning at sub nanometer resolution. The MEMS stage is driven by bidirectional Z-beam electrothermal actuators that generate large output forces to actuate the motion amplification mechanism. The motion amplification mechanisms are used in their inverse (motion reduction) mode to convert micrometer input displacements (from the Z-beam actuators) into nanometer output displacements at a constant motion reduction ratio with good linearity. This unique design significantly enhances the positioning resolution of the XY-stage. An analytical model is developed to predict output displacements of the XY-stage as a function of the input voltages applied to the Z-beam actuators, and the predicted results agree with the experimental results. Capacitive displacement sensors are arranged along both X- and Y-axes for measuring the input displacements of the amplification mechanisms, enabling closed-loop nanopositioning control of the XY-stage. The device calibration results show that, within an actuation voltage of ±15 V, the MEMS stage offers a motion range close to ±1 μm and a displacement resolution better than 0.3 nm −1.

Redox-Triggered Helicity Inversion in Chiral Cobalt Complexes in Combination with H(+) and NO3(-) Stimuli.

Three chiral ligands with variable denticity, H2L2-H2L4, conjugated by N,N'-ethylenebis[N-methyl-(S)-alanine] and an ortho-heterosubstituted aromatic amine, were newly synthesized as analogues of previously reported H2L1. Four contracted-Λoxo cobalt(III) complexes [Co(L)](+) with left-handed helical structure of Λ4Δ2 configuration were prepared by one-electron oxidation of the corresponding contracted-Λred cobalt(II) complexes [Co(L)], which were generated from chiral ligands and Co(ClO4)2·6H2O or Co(CF3SO3)2·5.2H2O in the presence of an organic base. Although the prepared cobalt(III) complexes were very inert and kinetically stable against protonation and NO3(-) complexation, cobalt(III) reduction in the presence of CF3SO3H and/or Bu4NNO3 allowed immediate changing of their three-dimensional structures from the contracted-Λoxo form to the extended-Λ [Co(H2L)Y2](n+) (Y = solvent and/or anion, n = 0-2) form with left-handed helicity or to the extended-Δ [Co(H2L)(NO3)](+) form with right-handed helicity via N- to O-amide coordination switching. Both extended forms were contracted to the original Λoxo form by oxidation of the cobalt(II) center in the presence of an organic base. Thus, redox reactions triggered dynamic helicity inversion of the chiral cobalt complexes, via multiple molecular motions consisting of relaxation/compression, extension/contraction, and helicity inversion motions in combination with deprotonation/protonation of amide linkages and NO3(-) anion complexation.

Integration-Enhanced Zhang Neural Network for Real-Time-Varying Matrix Inversion in the Presence of Various Kinds of Noises.

Matrix inversion often arises in the fields of science and engineering. Many models for matrix inversion usually assume that the solving process is free of noises or that the denoising has been conducted before the computation. However, time is precious for the real-time-varying matrix inversion in practice, and any preprocessing for noise reduction may consume extra time, possibly violating the requirement of real-time computation. Therefore, a new model for time-varying matrix inversion that is able to handle simultaneously the noises is urgently needed. In this paper, an integration-enhanced Zhang neural network (IEZNN) model is first proposed and investigated for real-time-varying matrix inversion. Then, the conventional ZNN model and the gradient neural network model are presented and employed for comparison. In addition, theoretical analyses show that the proposed IEZNN model has the global exponential convergence property. Moreover, in the presence of various kinds of noises, the proposed IEZNN model is proven to have an improved performance. That is, the proposed IEZNN model converges to the theoretical solution of the time-varying matrix inversion problem no matter how large the matrix-form constant noise is, and the residual errors of the proposed IEZNN model can be arbitrarily small for time-varying noises and random noises. Finally, three illustrative simulation examples, including an application to the inverse kinematic motion planning of a robot manipulator, are provided and analyzed to substantiate the efficacy and superiority of the proposed IEZNN model for real-time-varying matrix inversion.

The Mechanical Functionality of the EXO-L Ankle Brace

Background: A new type of ankle brace (EXO-L) has recently been introduced. It is designed to limit the motion of most sprains without limiting other motions and to overcome problems such as skin irritation associated with taping or poor fit in the sports shoe. Purpose: To evaluate the claimed functionality of the new ankle brace in limiting only the motion of combined inversion and plantar flexion. Study Design: Controlled laboratory study. Methods: In 12 patients who received and used the new ankle brace, the mobility of the joints was measured with a highly accurate and objective in vivo 3-dimensional computed tomography (3D CT) stress test. Primary outcomes were the ranges of motion as expressed by helical axis rotations without and with the ankle brace between the following extreme positions: dorsiflexion to plantar flexion, and combined eversion and dorsiflexion to combined inversion and plantar flexion. Rotations were acquired for both talocrural and subtalar joints. A paired Student t test was performed to test the significance of the differences between the 2 conditions (P ≤ .05). Results: The use of the ankle brace significantly restricted the rotation of motion from combined eversion and dorsiflexion to combined inversion and plantar flexion in both the talocrural (P = .004) and subtalar joints (P < .001). No significant differences were found in both joints for the motion from dorsiflexion to plantar flexion. Conclusion: The 3D CT stress test confirmed that under static and passive testing conditions, the new ankle brace limits the inversion–plantar flexion motion that is responsible for most ankle sprains without limiting plantar flexion or dorsiflexion. Clinical Relevance: This test demonstrated its use in the objective evaluation of braces.