Forward Force Research Articles

Effect of robotic-assisted gait rehabilitation on dynamic equilibrium control in the gait of children with cerebral palsy

Due to the intensity and repetition of movement, roboticassisted gait training therapy could have a beneficial effect on the recovery and improvement of postural and locomotor functions of the patient. This study sought to highlight the effects of robotic-assisted gait rehabilitation in gait of children with Cerebral Palsy (CP). We analyzed the different strategies before and after this rehabilitation which was used in order to generate forward motion while maintaining balance. Data were collected by a motion analysis system (Vicon® - Oxford Metrics, Oxford, UK). The children were divided into two groups in such a way as to obtain a randomized controlled population: i) a group of fourteen children (Treated Group) underwent 20 sessions of roboticassisted gait training therapy using the driven gait orthosis Lokomat®Pediatric (Hocoma AG, Volketswil, Switzerland) compared to ii) a group of sixteen children without sessions of Lokomat®Pediatric (Control Group). Significant differences are observed for the TG between the preand post-test values of the locomotor parameters and of the kinetic data of the propulsive forces of the Center of Mass (COM) and of the Center of Pressure (COP) dynamic trajectory. This first study, although performed on a limited number of patients, shows the usefulness of this robotic gait rehabilitation mainly in the balance control in gait. Indeed after this rehabilitation, these children improve their gait that is especially characterized by a more appropriate time lag between the time instant of COM-COP trajectory divergence and the time instant when the forward propulsive forces became apparent.

A Miniature Flexible-Link Magnetic Swimming Robot With Two Vibration Modes: Design, Modeling and Characterization

In this letter, we report a miniature swimming robot that consists of a nonmagnetic V-shaped head, an I-shaped tail attached with a magnet and a flexible link for interconnection of the rigid head and tail. The use of a flexible link enables the robot to exhibit two different vibration modes by tuning the input frequencies of the applied oscillating magnetic field with uniform field strength. When the input frequency is below 15 Hz, the head and tail show similar and large vibration amplitudes, and the net centrifugal force mainly contributes to the forward propulsion of the robot in fluid. While with high input frequencies (i.e., larger than 30 Hz), the flexible link can filter away high-frequency signals to efficiently avoid the passive vibration of the nonmagnetic head. Simultaneously, the magnetic tail vibrates with relatively large amplitude and generates forward propulsion force for the robot. To understand the whole-body-vibration and tail-vibration behaviors, an analytical model has been developed. Moreover, swimming performances of this robot, i.e., the propulsion force and swimming velocity, are characterized on the substrate-water interface. Finally, we demonstrate two-dimensional manipulation of tiny objects by utilizing the two vibration modes of the robot.

English

The presence of forward forces in foreign soil is not a modern notion, but is thought-provoking when a small state projects its military might in multiple locations of a similar strategic importance. The United Arab Emirates’ (UAE) base lease in Berbera is a case in point which attracted a reproach from the public, and politicians. The joint parliament sitting to approve the draft agreement further complicated the reproach, resulting in many stakeholders to argue that the approval process suffered insufficient consultation, citing ambiguity, and suspicion. Berbera basing politics is critical to Somaliland’s national security, but gained little scholarly attention that can explain the rationale, and the underlying assumptions. This paper will, therefore, provide a qualitative assessment on impact of UAE’s overseas defense posture on Somaliland’s political direction. Specifically, it tends to analyze the structural architect of the basing politics including actors, interests, risks (animosities), and prophesy on scenarios for use. This paper uses secondary and primary sources to sketch out the key issues; it also employs relevant international relations theories: security dilemma, deterrence, defensive, proxy war, geopolitics, pre-emption, beggar-thy-neighbour, and safe-haven concepts to make sense on this matter. Key words: National security, basing politics, interests, actors, animosity, deterrence, collective security, collective defense.

ONTOLOGICAL APPROACHES ARE TO FORMING OF WORLD VIEW CONCEPTIONS OF TRANSNATIONALIZATION

Ontological approaches are considered to forming of world view conceptions of transnationalization. The modern theories of transnationalization are analysed, found out advantages and failings. Perspective directions are formulated in research globalizations of world economy, which are conditioned the processes of transnationalization. It is discovered – the theories of ransnationalization have empiric character which stipulates the certain degree of abstract of their ground. The phenomena, resources and level of efficiency of their using, have the generalized character. Influence is as a result leveled on development of processes of ransnationalization such important factor, as of a particular branch specialization. It is analysed, authors, examining the integration processes of theories of ransnationalization, avoid the question of regional of a particular branch diversification of PFI, doing an accent on the political, economic and social and legal aspects of development of world economy.Conclusions are done, that the modern processes of globalization are conditioned motion of direct foreign investments. Multinational corporations come forward basic motive force of PFI. In the process of analysis of conduct and basic tendencies of functioning of TNC, understanding of «rules of game» on a world arena and possibility of prognostication of perspective progress trends appears.

Greater gait with gravity

Neurorehabilitation Often taken for granted, gravity—the force that keeps you on the ground—becomes a notable challenge during rehabilitation from injury. Mignardot et al. “harnessed” gravity, using a robotic body weight–supportive device to supply upward and forward forces to the torso to assist with locomotion. Patients recovering from stroke or spinal cord injury demonstrated improved gait performance with the robotic harness. An algorithm was developed to adjust the forces provided by the robotic harness according to the patient's needs. Nonambulatory patients were able to walk naturally with the harness, and ambulatory patients showed improved balance, limb coordination, foot placement, and steering. A clinical trial using this robot-assistive rehabilitation approach for patients with spinal cord injury is now under way. Sci. Transl. Med. 9 , eaah3621 (2017).

Robot motion synthesis using ground reaction forces pattern

Gait generation in its realization stage in majority of bipeds involves inverse dynamics model with the need of pre-determined joint trajectories and the zero moment point method for final postural stability adjustments. This requires generation of such joint trajectories, where the zero moment point criterion is fulfilled and the human-like posture is kept. Such task is complex and still misses the universal solution. Preserving natural (human-like) and stable body posture under acting disturbances is an issue too. High computational costs, problem with disturbances rejection and controller complexity are the major disadvantages associated with such approaches. This article presents a method for motion control with forward dynamics model and ground reaction forces as the reference values. The ground reaction forces measured during real human walking are utilized here. A MATLAB/Simulink framework is used for testing the proposed synthesis of bipedal locomotion. The ground reaction forces recorded during the walk with different footwear are applied as the references. The obtained motion patterns and postures are compared with those of the human. Obtained results were satisfactory and justified the proposed approach.

Firefighter Nozzle Reaction

Nozzle reaction and hose tension are analyzed using conservation of fluid momentum and assuming steady, inviscid flow and a flexible hose in frictionless contact with the ground. An expression that is independent of the bend angle is derived for the hose tension. If this tension is exceeded owing to anchor forces, the hose becomes straight. The nozzle reaction is found to equal the jet momentum flow rate, and it does not change when an elbow connects the hose to the nozzle. A forward force must be exerted by a firefighter or another anchor that matches the forward force that the jet would exert on a perpendicular wall. Three reaction expressions are derived, allowing it to be determined in terms of hose diameter, jet diameter, flow rate, and static pressure upstream of the nozzle. The nozzle reaction predictions used by the fire service are 56% to 90% of those obtained here for typical firefighting hand lines. Sharing these findings with the fire protection community can improve the safety of firefighters.

Fast Computation of Global Sensitivity Kernel Database Based on Spectral-Element Simulations

Finite-frequency sensitivity kernels, a theoretical improvement from simple infinitely thin ray paths, have been used extensively in recent global and regional tomographic inversions. These sensitivity kernels provide more consistent and accurate interpretation of a growing number of broadband measurements, and are critical in mapping 3D heterogeneous structures of the mantle. Based on Born approximation, the calculation of sensitivity kernels requires the interaction of the forward wavefield and an adjoint wavefield generated by placing adjoint sources at stations. Both fields can be obtained accurately through numerical simulations of seismic wave propagation, particularly important for kernels of phases that cannot be sufficiently described by ray theory (such as core-diffracted waves). However, the total number of forward and adjoint numerical simulations required to build kernels for individual source–receiver pairs and to form the design matrix for classical tomography is computationally unaffordable. In this paper, we take advantage of the symmetry of 1D reference models, perform moment tensor forward and point force adjoint spectral-element simulations, and save six-component strain fields only on the equatorial plane based on the open-source spectral-element simulation package, SPECFEM3D_GLOBE. Sensitivity kernels for seismic phases at any epicentral distance can be efficiently computed by combining forward and adjoint strain wavefields from the saved strain field database, which significantly reduces both the number of simulations and the amount of storage required for global tomographic problems. Based on this technique, we compute traveltime, amplitude and/or boundary kernels of isotropic and radially anisotropic elastic parameters for various ( $$P$$ , $$S$$ , $$P_{\mathrm{diff}}$$ , $$S_{\mathrm{diff}}$$ , depth, surface-reflected, surface wave, S 660 S boundary, etc.) phases for 1D ak135 model, in preparation for future global tomographic inversions.

Coupled Unsteady Aero-Flight Dynamics of Hovering Insects/Flapping Micro Air Vehicles

The main objective of this paper is to provide a rigorous coupling between body flight dynamics and flow dynamics (unsteady aerodynamics) in hovering of insects and flapping-wing micro air vehicles. A reduced-order unsteady aerodynamic model that takes into account the leading-edge vortex and rotational effects is integrated with a dynamic model to construct a flight dynamic model for flapping-wing micro air vehicles and insects near hover. Then, the averaging theorem is used to study the dynamic stability of such a nonlinear time-periodic system. Effects of unsteady aerodynamics on the trim/balance problem and stability of such an equilibrium are assessed. It is found that the flow dynamics induces asymmetric forward force and pitching moment, even though the flapping motion is symmetric. As such, balance of insects and flapping-wing micro air vehicles at hover cannot be achieved by purely symmetric flapping. Although unsteady aerodynamics considerably affects the balance/trim problem, its effect on stability is minor.

Design and mechanical analysis of a new automatic vertical drilling tool used in a slim borehole

A new kind of electronic-controlled automatic vertical drilling tool is developed to satisfy the requirements of slim-hole, which has a unique push-actuator to push-the-bit. This paper introduced the mechanical structure and working process of the automatic tool, and analyzed in detail one of the most critical component - the push-actuator. The analysis reveals that, with the pitch-row of studdle increasing form 20mm to 24mm, the ratio of push-out force to forward force gradually decreases from 2.04 to 0.78, and the completion time of push-out process reduces from 75.8s to 42.8. This result indicates that, using studdles with shorter pitch-rows, larger straightening force could be obtained. On the contrary, studdles with longer pitch-rows could realize more quickly sensitive response of deviation control. These unique characters make the vertical drilling being able to be adapted to different geological conditions and technological requirements, the applicability and feasibility of the drilling tool remarkably improved. Thus this vertical drilling tool owns a great promotional value for oil & gas exploration.

Influence Of Proprioceptive Intervention On Joint Configuration During Sprint Starts In Elite Collegiate Sprinters

PURPOSE: An effective block clearance (BC) is crucial to the success of competitive sprinters. To have success a sprinter must exert an impulse to change his/her momentum while also staying low to the ground, in order to maximize the amount of forward force. The purpose of this experiment was to investigate the influence of proprioceptive priming on the kinetics and kinematics of the sprint start. METHODS: Three female (age: 20 yrs±1.73, height: 1.64 m±.07, weight: 58.78 kg±9.11) and three male collegiate sprinters (age: 23yrs±3.464, height: 1.84 m±.08, weight: 75.3 kg±4.46) participated in the study. Participants performed two baseline (BL) trials and two proprioceptive (PR) trials involving a resistance band. Participants were fitted with a full body 55-marker set, 3D kinematics were recorded with a 12-camera motion capture system sampling at 250Hz. Kinetic analysis included assessments of Impulse, Angle of GRF (Sagittal plane), and Average Force. Kinematic analysis included stride rate (SR) and stride length (SL), ground time (GT) and air time (AT), peak toe height during swing phase of sprinting gait, and segment angles. Segment angles were measured for the rear lower leg (RLL) at ankle cross along with the RLL at take-off during the first two steps (S1AC, S1TO, S2AC, S2TO). RESULTS: There were no significant changes in impulse or average force between interventions. There was, however, a significant difference between the force angle produced during proprioceptive (51.7° ±3.6) and combination (46.6° ±8.6) interventions (p<0.05). Kinematic data were reported for BL and PR, respectively. As for S1, average peak toe height was 0.262 m±.114, and 0.241 m±.054. During S2, average peak toe height was 0.239±.054 m, and .232 m ±.057. There was a significant decrease in peak toe height post-intervention for BC (p<0.05). The RLL angle at S1AC were 63.88°±15.61 and 70°±16.81 along with 67.48°±10.29 and 77.78°±13.28 at S2AC. The angles for S1TO were 158.30°±4.30 and 153.94°±4.61 RLL. CONCLUSION: Proprioceptive training resulted in an improvement in ground time values during the sprint start and reduced peak toe height for all phases, but showed mixed results for air time. These results suggest that proprioceptive priming has the potential to improve sprint start mechanics and performance.

Robot-assisted gait training improves the walking ability of hemiplegic patients

Objective To evaluate the effect of robot-assisted gait training on the walking ability of hemiplegic patients. Methods Sixty hemiplegic patients were randomly divided into a control group and a treatment group, each of 30. Both groups were given traditional rehabilitation and drug therapy. The control group was additionally provided with the traditional gait training, while the treatment group additionally received robot-assisted gait training. The gait training lasted 30 minutes a day, 5 days per week. Before and after 8 weeks of training, the time parameters, phase parameters, the joint angles of the lower limbs, and the peak ground reaction forces of both groups were evaluated using a three-dimensional gait analysis system. Results After the intervention, the walking velocity, stride frequency and stride length had increased in the treatment group, while stride width had decreased. Significant improvement was observed in the treatment group in terms of the percentage of swing phase on the paretic side, the percentage of stance phase on the paretic side, the single support time ratio, the percentage of double support phase, the range of motion of the hip and knee joints, and the peak vertical and forward ground reaction force as a percentage of body weight. The improvements were significantly greater than those observed in the control group. Conclusions Compared with traditional walking training, robot-assisted gait training can be more effective in improving the walking ability of hemiplegic patients. Key words: Robots; Gait training; Walking ability; Gait analysis

New method for harvesting energy from fluid flow based on undulatory motion

ABSTRACTIn nature, fish have gained wonderful swimming ability over the thousands of years of evolution. As the fish swims, its body, namely, it’s dorsal or tail fin undulates and then alternating waves are sent down the body towards the tip of the tail. These waves generate a jet in the wake and hence a forward force, namely thrust. Scientific studies have already shown that undulatory swimming is a highly effective means of continuous locomotion and has been successfully adopted in many kinds of robotic fishes currently being developed. However, our latest research found that if wave velocity that defines the undulatory motion of the body or the ‘fin’ is less than a specific value, the fishlike body with undulatory motion also has the capability to harvest kinetic energy from flowing fluid. This finding proposes a new energy-harvesting concept which could offer a new and promising solution to support the long-distance voyage of a biomimetic robotic fish.

Comparison of crossover and jab step start techniques for base stealing in baseball

Base stealing is an important tactic for increasing the chance of scoring in baseball. This study aimed to compare the crossover step (CS) and jab step (JS) starts for base stealing start performance and to clarify the differences between CS and JS starts in terms of three-dimensional lower extremity joint kinetics. Twelve male baseball players performed CS and JS starts, during which their motion and the force they applied to the ground were simultaneously recorded using a motion-capture system and two force platforms. The results showed that the normalised average forward external power, the average forward–backward force exerted by the left leg, and the forward velocities of the whole body centre of gravity generated by both legs and the left leg were significantly higher for the JS start than for the CS start. Moreover, the positive work done by hip extension during the left leg push-off was two-times greater for the JS start than the CS start. In conclusion, this study has demonstrated that the jab step start may be the better technique for a base stealing start and that greater positive work produced by left hip extension is probably responsible for producing its larger forward ground reaction force.

Motion generation of Multi-body systems considering dynamic posture stabilization using forward dynamic model and virtual external force

Motion generation of Multi-body systems considering dynamic posture stabilization using forward dynamic model and virtual external force

Washington's perceptions and misperceptions of Beijing's anti-access area-denial (A2-AD) ‘strategy’: implications for military escalation control and strategic stability

ABSTRACTWashington has become increasingly concerned that Beijing's anti-access area-denial (A2-AD) capabilities will put at risk US military assets and forward forces operating in the Western Pacific region, enabling China to deter, delay and deny US intervention in future regional conflict and crisis. US defence analysts in their assessments have frequently, and often erroneously, conflated a Chinese operational capability with an underlying strategic intention that conceptualises the United States as its primary (if not sole) target. The central argument this article proffers is that US perceptions of A2-AD have been framed by specific analytical baselines that have overlooked the evolution of Chinese operational and doctrinal preferences, and over-reliant upon military material-based assessments to determine Beijing's strategic intentions, and formulate US military countervails. The article concludes that the strategic ambiguities and opacity associated with Chinese A2-AD capabilities and its ‘active defence’ concept reinforced Washington's reliance upon capacity-based assessments that in turn, exacerbated misperceptions confounded by cognitive bias of Chinese strategic intentions. The critical framing assumptions of this article draw heavily upon the ideas and rationale associated with the international relations ‘Security Dilemma’ concept.

Directional Control for Precise Deployment of Endovascular Aneurysm Repair and Thoracic Endovascular Aortic Repair in Angulated Anatomy

Endovascular stent graft repair of aortic aneurysms has become the standard in most centers. Several anatomic constraints still prevent or compromise the use of this technology. Angulated infrarenal aortic necks or steep aortic arches may result in erratic stent graft deployment with inadvertent branch vessel coverage, inadequate lesion coverage, or bird beaking. We have developed a technique using off-the-shelf equipment to precisely control the deployment of stent grafts in challenging landing zones. Two patients with challenging proximal landing zones were treated by this technique. The first patient, a 72-year-old man, was treated with a Gore Excluder device (W. L. Gore & Associates, Flagstaff, Ariz) for a 5.6-cm infrarenal aortic aneurysm with an angulated neck. A standard J wire was passed through the device, captured with an endosnare, and removed through a Destino sheath (Oscor, Palm Harbor, Fla) in the contralateral groin. The through-and-through wire and sheath allowed the precise deflection of the device along the angulated neck. The device was deployed while deflected. The remainder of the case was unremarkable. The second patient was an 84-year-old man who developed a descending thoracic aortic intramural hematoma with acute enlargement and pseudoaneurysm in the setting of type III aortic arch. In the operating room, two GORE CTAG thoracic stent grafts were built up from the celiac into the proximal descending thoracic aorta. A final proximal stent graft was advanced into approximate position. Left brachial access was established, and a J wire was brought through and through from the stent graft into a 5F MPA catheter in the left brachial sheath. Through a combination of wire traction and forward force on the MPA catheter, the device was precisely positioned onto the lesser curve. The graft was deployed orthogonally at the level of the left carotid. A left subclavian snorkel was planned preoperatively and was placed. In both cases, technical success was attained. Follow-up imaging at 6 weeks in each case demonstrated continuous wall apposition and no endoleak. Anatomic constraints have limited or complicated the use of endovascular stent grafts for some aortic disease. The use of a through-and-through flexible wire and a stiff catheter or sheath allows precise placement in these challenging landing zones.

Modeling of equal channel forward extrusion force using response surface approach

Equal channel forward extrusion is a new severe plastic deformation method that has been developed in recent years. This study investigates the effect of significant parameters on the equal channel forward extrusion pressing force. First, the process was modeled by finite element method and has been validated using experimental results. Next, response surface method and analysis of variance were applied to investigate the influences of equal channel forward extrusion parameters such as friction coefficient magnitude, length-to-width ratio and main deformation zone height on the pressing force. Finally, a new formula is presented for prediction of equal channel forward extrusion pressing force using statistical modeling.

Macroscopic and microscopic study of integuments on ostrich (Struthio camelus) foot

Abstract Introduction: Ostrich characteristics include fast running, of which the probable enablers have been studied. Yet little research has taken place on one anatomical feature. It is mainly the special integuments on the ostrich foot which facilitate fast running on sand, because as point of direct sand contact they bear the whole weight and provide all the forward force. This study elucidates aspects of the integuments. Material and Methods: A stereo microscope, scanning electron microscope (SEM), and confocal scanning laser microscope were used to observe these integuments. Their surface structure was shown accurately in photographs. An SEM equipped with energy dispersive spectroscopy was used to check element contents of the upper and bottom areas and those on the lateral area of the 3rd toe. Results: The content of some chemical elements on the upper area (Mg 2.04%, Si 0.18%, P 1.97%, Ca 0.59%, and S 0.69%) was higher than that of the bottom area (Mg 0.14%, Si 0.09%, P 0.10%, Ca 0.28%, and S 0.90%). Zinc was the particular element on the upper area, while sodium, chlorine, and potassium were the specific elements on the bottom area. The parts which must withstand different frictions contained different chemical compounds. Conclusion: The microscopic plane with layer-like structure and stripes may contribute to the wear-resistance of the papillae. The polygonal and prism structures are helpful to fix papillae in a firmer way.

A NEW DYNAMICAL MODELING OF XENOPUS LAEVIS DURING FAST SWIMMING BASED ON REAL KINEMATICAL AND GEOMETRICAL DATA

The dynamic study of frog’s swimming style contributes to the modeling of the nature-inspired robots. To study the torque matrix produced in the joints during continuous modeling, the dynamic model of the Xenopus laevis swimming is reproduced in the coronal plane. The necessary kinematic data for the modeling is extracted from the frog movement graphs and diagrams during swimming. In the dynamic model, legs are considered as a group of rigid links. In order to verify this method, the generated forward force in half a cycle is studied. Unlike the previous studies, the role of geometry, dimensions and mechanical properties of the legs’ fundamental links in generating thrust force is modeled in this study, leading to finding the most proper form for this mechanism design.