Deployment Velocity Research Articles

Computer Modelling Study of Volume Kinetics in Intraocular Segments Following Airbag Impact Using Finite Element Analysis.

We have previously studied the physiological and mechanical responses of the eye to blunt trauma in various situations using finite element analysis (FEA). In this study, we evaluated the volume kinetics of an airbag impact on the eye using FEA to sequentially determine the volume change rates of intraocular segments at various airbag deployment velocities. The human eye model we created was used in simulations with the FEA program PAM-GENERISTM (Nihon ESI, Tokyo, Japan). Different airbag deployment velocities, 30, 40, 50, 60 and 70 m/s, were applied in the forward direction. The volume of the deformed eye impacted by the airbag was calculated as the integrated value of all meshes in each segment, and the decrease rate was calculated as the ratio of the decreased volume of each segment at particular timepoints to the value before the airbag impact. The minimum volume of the anterior chamber was 63%, 69% and 50% at 50, 60 and 70 m/s airbag impact velocity, respectively, showing a curve with a sharp decline followed by gradual recovery. In contrast to the anterior chamber, the volume of the lens recovered promptly, reaching 80-90% at the end of observation, except for the case of 60 m/s. Following the decrease, the volume increased to more than that of baseline at 60 m/s. The rate of volume change of the vitreous was distributed in a narrow range, 99.2-100.4%. In this study, we found a large, prolonged decrease of volume in the anterior chamber, a similar large decrease followed by prompt recovery of volume in the lens, and a time-lag in the volume decrease between these tissues. These novel findings may provide an important insight into the pathophysiological mechanism of airbag ocular injuries through this further evaluation, employing a refined FEA model representing cuboidal deformation, to develop a more safe airbag system.

Simulation of Changes in Tensile Strain by Airbag Impact on Eyes After Trabeculectomy by Using Finite Element Analysis.

We studied the kinetic phenomenon of an airbag impact on eyes after trabeculectomy using finite element analysis (FEA), a computerized method for predicting how an object reacts to real-world physical effects and showing whether an object will break, to sequentially determine the responses at various airbag deployment velocities. A human eye model was used in the simulations using the FEA program PAM-GENERISTM (Nihon ESI, Tokyo, Japan). A half-thickness incised scleral flap was created on the limbus and the strength of its adhesion to the outer sclera was set at 30%, 50%, and 100%. The airbag was set to hit the surface of the post-trabeculectomy eye at various velocities in two directions: perpendicular to the corneal center or perpendicular to the scleral flap (30° gaze-down position), at initial velocities of 20, 30, 40, 50, and 60 m/s. When the airbag impacted at 20 m/s or 30 m/s, the strain on the cornea and sclera did not reach the mechanical threshold and globe rupture was not observed. Scleral flap lacerations were observed at 40 m/s or more in any eye position, and scleral rupture extending posteriorly from the scleral flap edge and rupture of the scleral flap resulting from extension of the corneal laceration through limbal damage were observed. Even in the case of 100% scleral flap adhesion strength, scleral flap rupture occurred at 50 m/s impact velocity in the 30° gaze-down position, whereas in eyes with 30% or 50% scleral flap adhesion strength, scleral rupture was observed at an impact velocity of 40 m/s or more in both eye positions. An airbag impact of ≥40 m/s might induce scleral flap rupture, indicating that current airbags may induce globe rupture in the eyes after trabeculectomy. The considerable damage caused by an airbag on the eyes of short-stature patients with glaucoma who have undergone trabeculectomy might indicate the necessity of ocular protection to avoid permanent eye damage.

A Review of 3D Printing Batteries

To stabilize the Earth’s climate, large-scale transition is needed to non-carbon-emitting renewable energy technologies like wind and solar energy. Although these renewable energy sources are now lower-cost than fossil fuels, their inherent intermittency makes them unable to supply a constant load without storage. To address these challenges, rechargeable electric batteries are currently the most promising option; however, their high capital costs limit current deployment velocities. To both reduce the cost as well as improve performance, 3D printing technology has emerged as a promising solution. This literature review provides state-of-the-art enhancements of battery properties with 3D printing, including efficiency, mechanical stability, energy and power density, customizability and sizing, production process efficiency, material conservation, and environmental sustainability as well as the progress in solid-state batteries. The principles, advantages, limitations, and recent advancements associated with the most common types of 3D printing are reviewed focusing on their contributions to the battery field. 3D printing battery components as well as full batteries offer design flexibility, geometric freedom, and material flexibility, reduce pack weight, minimize material waste, increase the range of applications, and have the potential to reduce costs. As 3D printing technologies become more accessible, the prospect of cost-effective production for customized batteries is extremely promising.

Finite Element Analysis of Changes in Deformation of Intraocular Segments by Airbag Impact in Eyes of Various Axial Lengths.

We studied the kinetic phenomenon of an airbag impact on eyes with different axial lengths using finite element analysis (FEA) to sequentially determine the physical and mechanical responses of intraocular segments at various airbag deployment velocities. The human eye model we created was used in simulations with the FEA program PAM-GENERISTM. The airbag was set to impact eyes with axial lengths of 21.85 mm (hyperopia), 23.85 mm (emmetropia) and 25.85 mm (myopia), at initial velocities of 20, 30, 40, 50 and 60 m/s. The deformation rate was calculated as the ratio of the length of three segments, anterior chamber, lens and vitreous, to that at the baseline from 0.2 ms to 2.0 ms after the airbag impact. Deformation rate of the anterior chamber was greater than that of other segments, especially in the early phase, 0.2-0.4 ms after the impact (P < 0.001), and it reached its peak, 80%, at 0.8 ms. A higher deformation rate in the anterior chamber was found in hyperopia compared with other axial length eyes in the first half period, 0.2-0.8 ms, followed by the rate in emmetropia (P < 0.001). The lens deformation rate was low, its peak ranging from 40% to 75%, and exceeded that of the anterior chamber at 1.4 ms and 1.6 ms after the impact (P < 0.01). The vitreous deformation rate was lower throughout the simulation period than that of the other segments and ranged from a negative value (elongation) in the later phase. Airbag impact on the eyeball causes evident deformation, especially in the anterior chamber. The results obtained in this study, such as the time lag of the peak deformation between the anterior chamber and lens, suggest a clue to the pathophysiological mechanism of airbag ocular injury.

The effects of deployment friction on the dynamics of nonconductive space tethers

At present, the neglect of deployment friction could lead to a significant deviation in the numerical results from the real deployment dynamic characteristics of the nonconductive space tether. To solve this problem, a dedicated experimental setup for tether deployment was firstly employed to measure the deployment friction of nonconductive space tether, the dependences of the deployment friction on the tether diameter, deployment velocity and deployment angle (which is the angle between the deployment direction and the normal direction of the tether exit) were determined. The effect of deployment parameters on the dynamics in both the uncontrolled tether deployment and the station-keeping stages were evaluated based on the “dumbbell” and “extended dumbbell” models, the measured deployment frictions was applied to the models. The numerical results show that the uncontrolled nonconductive tether deployment is great limited by the deployment friction; the tether deployment capability and dynamic stability could be enhanced by increasing the initial deployment velocity (≤2 m/s) and satellite effective mass, as well as decreasing the orbital altitude. To guarantee maximum tether deployment capability and dynamic stability, an optimal matching relationship between the tether full length and satellite total mass is given, which is of substantial importance for the uncontrolled deployment process of the nonconductive space tether system at the design stage.

Mechanical and Economic Analysis of Conventional Aluminum Photovoltaic Module Frames, Frames With Side Holes, and Open-Source Downward-Fastened Frames for Non-Traditional Racking

Abstract Using bolts through the back of a solar photovoltaic (PV) module frames to attach them to racking is time consuming and awkward, so commercial PV installations use clamping technologies on the front. Conventional and proprietary clamps are costly and demand access to supply chains for uncommon mechanical components that limit deployment velocity. To overcome these challenges, this study presents new open-source downward-fastened and side-fastened aluminum (Al) framing designs, which are easy to install and compatible with metal and wood racks. The proposed parametric open-source designs are analyzed through finite element method (FEM) simulations and economic analysis is performed to compare to conventional PV frame at both the module and system levels. The FEM results showed all the frames have acceptable mechanical reliability and stability to pass IEC 61215 standards. The results show the new frame (with a bottom width of 29 mm and thickness of 1.5 mm) has about a 2% land use efficiency penalty, but has better mechanical stability (lower stress and deflections), is easier to install, and has reduced material economic costs compared to conventional frames. The results are promising for the use of the new PV frame designs for distributed manufacturing targeted at specific applications.

Roll-Out Deployment Process Analysis of a Fiber Reinforced Polymer (FRP) Composite Tape-Spring Boom.

Deployable extendable booms are widely used in aerospace technology due to many advantages they have, such as high folded-ratio, lightweight and self-deployable properties. A bistable FRP composite boom can not only extend its tip outwards with a corresponding rotation speed on the hub, but can also drive the hub rolling outwards with a fixed boom tip, which is commonly called roll-out deployment. In a bistable boom's roll-out deployment process, the second stability can keep the coiled section from chaos without introducing a controlling mechanism. Because of this, the boom's roll-out deployment velocity is not under control, and a high moving speed at the end will give the structure a big impact. Therefore, predicting the velocity in this whole deployment process is necessary to be researched. This paper aims to analyze the roll-out deployment process of a bistable FRP composite tape-spring boom. First, based on the Classical Laminate Theory, a dynamic analytical model of a bistable boom is established through the energy method. Afterwards, an experiment is introduced to produce some practical verification for comparison with the analytical results. According to the comparison with the experiment, the analytical model is verified for predicting the deployment velocity when the boom is relatively short, which can cover most booms using CubeSats. Finally, a parametric study reveals the relationship between the boom properties and the deployment behaviors. The research of this paper will give some guidance to the design of a composite roll-out deployable boom.

A mathematical model for estimating the Gurney velocity of chemical high explosives

The Gurney velocity is an important performance parameter that characterizes the metal pushing capability of conventional chemical explosives. Herein, this study proposes a mathematical model that aims to provide a simple and effective means by which the Gurney velocity of pure and mixed CHNO-based explosives can be accurately determined using as input information the volumetric heat of detonation, the parameter psi (Ψ) and an adjustable parameter (λ) that accounts for the type of the explosive being studied. The new model proved adequate for evaluating the Gurney velocity of sensitive and insensitive explosives of military interest, including melt-castable and plastic-bonded explosives (PBXs) and showed superior predicting performance compared to benchmark models. It is believed that the Gurney velocity obtained by the new method along with the Gurney-type equations would be very helpful for ordnance engineers for calculating the peak fragment deployment velocity from various warhead geometries, including omnidirectional and directed energy warheads for use in various weapons systems.

Optimal inverter and wire selection for solar photovoltaic fencing applications

Despite the benefits and the economic advantages of agrivoltaics, capital costs limit deployment velocity. One recent potential solution to this challenge is to radically reduce the cost of racking materials by using existing farm fencing as vertical photovoltaic (PV) racking. This type of fenced-based PV system is inherently electrically challenging because of the relatively long distances between individual modules that are not present in more densely packed conventional solar PV farms. This study provides practical insights for inverter selection and wire sizing optimization for fence-based agrivoltaic systems. Numerical simulation sensitivities on the levelized cost of electricity (LCOE) were performed for 1) distance from the fence to the AC electrical panel, 2) inverter costs, and 3) geographic locations. The results showed that microinverters had better performance when the cross-over fence length was under 30 m or when the system was designed with less than seven solar PV modules, whereas string inverters were a better selection for longer fences. The cross-over number of modules depends significantly on the cost of the inverters, which is a parameter that influences the system's design. The capital costs for a fence retrofit are far less than for any form of conventional PV racking. In addition, the LCOE of the vertical fencing solar agrivoltaic system can be competitive with conventional ground-mounted solar PV for the niche of farmers. Especially, when they are located between the latitudes of 10° and 50° in either the northern or southern hemisphere, and coupled with their ancillary benefits they represent a great alternative for conventional PV systems.

Design and analysis of a novel hinged boom based on cable drive

Hinged booms are widely used in astrophysics missions; however, the trajectory and deployment velocity are difficult to control because they are usually driven by springs, which limits their application in narrow spaces. Thus, a novel hinged boom is highly required to achieve motion controllability. Through an equivalent substitution between the cable drive loop and the binary link in topology, a type synthesis method for the cable-driven single-degree-of-freedom chain is proposed based on the single-open-chain (SOC) adding method. According to the configuration design, a novel cable-driven hinged boom is proposed, aiming to achieve boom synchronism. Then, to preload easily, a method that preload is applied and measured at the cable ends is adopted and the relationship between the initial preload and the target preload is deduced. By analyzing the distribution of cable tension, a new stiffness model is proposed thus a stiffness equation is obtained. Finally, the dynamic simulation analysis and zero-gravity deployment experiment of the hinged boom is carried out to verify its reliability. This research provides a new way for the type synthesis of cable-driven single-degree-of-freedom chain and a new model for analyzing cable-driven stiffness. Moreover, the novel cable-driven hinged boom obtained in this study can be well-applied in the field of aerospace.

Dynamics and rebound behavior analysis of flexible tethered satellite system in deployment and station-keeping phases

The tether deployment of a tethered satellite system involves the consideration of complex dynamic properties of the tether, such as large deformation, slack, and even rebound, and therefore, the dynamic modelling of the tether is necessary for performing a dynamic analysis of the system. For a variable-length tether element, the absolute nodal coordinate formulation (ANCF) in the framework of the arbitrary Lagrange-Euler (ALE) description was used to develop a precise dynamic model of a tethered satellite. The model considered the gravitational gradient force and Coriolis force in the orbital coordinate frame, and it was validated through numerical simulation. In the presence of dynamic constraints, a deployment velocity of the tether was obtained by an optimal procedure. In the simulation, rebound behavior of the tethered satellite system was observed when the ANCF-ALE model was employed. Notably, the rebound behavior cannot be predicted by the traditional dumbbell model. Furthermore, an improved optimal deployment velocity was developed. Simulation results indicated that the rebound phenomenon was eliminated, and smooth deployment as well as a stable state of the station-keeping process were achieved. Additionally, the swing amplitude in the station-keeping phase decreased when a deployment strategy based on the improved optimal deployment velocity was used.

Deployment mechanism for a L-band helix antenna in 1-Unit Cubesat

Recently, there is a renewed interest in Earth Observation (EO) of the cryosphere as a proxy of global warming, soil moisture for agriculture and desertification studies, and biomass for carbon storage. Global Navigation Satellite System-Reflectometry (GNSS-R) and L-band microwave Radiometry have been used to perform these measurements. However, it is expected that the combination of both can largely improve current observations.3Cat-4 mission aims at addressing this technology challenge by integrating a combined GNSS-R and Microwave Radiometer payload into a 1-Unit CubeSat. One of the greatest challenges is the design of an antenna that respects the envelope and stowage requirements of 1-Unit CubeSat, being able to work in the different frequency bands: Global Positioning System (GPS) L1-band (1575 MHz), GPS L2-band (1227 MHz), and microwave radiometry at 1400–1427 MHz. After a trade-off analysis, a helix antenna was found to be the most suitable option. This antenna has 11 turns equally distributed with 68.1 mm of diameter. This design generates an antenna with 506 mm of axial length, providing the maximum radiation gain in the endfire direction. Additionally, a counterweight is added at the tip of the antenna to enhance the directivity, and it is used as gravity gradient technique. The deployment of this antenna in vacuum and extreme temperature conditions is the greatest mechanical challenge that needs to be addressed for the success of the mission.This work presents a mechanical solution that enables to deploy the helix antenna from 25.5 mm (stowed configuration) to the final 506 mm (deployed configuration). By sequentially deploying different parts of the antenna, the final configuration is reached without impacting the attitude pointing of the CubeSat. This is accomplished using dyneema lines that are melted sequentially by commands. In addition, the deployment velocity, acceleration, and waving are presented as part of its characterization. The current test results in a Thermal Vacuum Chamber indicate also that the deployment can be achieved in −35 °C. The 3Cat-4 CubeSat, with the L-band helix antenna, will be launched in Q4 2020 as part of the “Fly Your Satellite!” program of the European Space Agency (ESA).

Identification of chaotic phenomena in a flexible deployable solar panel with multiple clearances

Deployable solar panels are widely used in spacecraft, and the dynamic characteristics of the deployment process directly affect the accuracy, stability, and reliability of the deployment. The flexibility and hinge clearance of a solar panel are important factors affecting the dynamic characteristics of the deployment system. The finite element method (FEM) was used to deal with the deformations of the solar panel. A dynamic model of the deployment process of a flexible solar panel with multiple clearances was established by combining the Lagrange equation with the FEM. The dynamic characteristics of solar panel deployment with multiple clearances and flexibility coupling were analyzed through a numerical solution, and the chaotic phenomena caused by clearances were identified. The results show that reasonably matching the clearance and flexibility of the system structure could quickly stabilize the collision force, improve the system life, and effectively improve the stability of the solar panel deployment process. Chaotic phenomena could be induced by the deployment velocity in a certain range, and the boundary value of the range changed with different clearance radii. The velocity variation law inducing chaotic phenomena also varied with the radius of clearance. This research provides important guidance for the optimum design and manufacturing of deployable solar panel mechanisms.

Deployment control of tethered space systems with explicit velocity constraint and invariance principle

This paper develops control laws for the deployment of tethered spacecraft systems with an explicit non-negative velocity constraint using invariance principle of control systems. It addresses a class of space tether deployment control problems where the tether is deployed out only. This implies the tether deployment velocity must be always positive and approaches to zero at the end of deployment. This non-negative velocity constraint is explicitly satisfied in the proposed tension control laws by transforming it into an invariance property of control system. Two control laws with nonlinear feedback are derived with two complementary manifolds. The Lyapunov stability of the control laws is proved and the controllability of the tethered spacecraft system with tension input is analyzed. Finally, the effectiveness of control laws is demonstrated by numerical simulation.

Towards a process management life-cycle model for graduation projects in computer engineering.

Graduation projects play an important role in computer engineering careers in which students are expected to draw upon their knowledge and skills that were acquired since admission. To manage the activities of graduation projects, an iterative and incremental approach which aims continuous improvement is proposed as an alternative to a controversial delivery model. However, such integration brings up a set of challenges to be taken into account: e.g. multiple project deliveries, more labor-intensive effort from instructors, and ultimately continuous learning for all participants. One promising way to achieve such an integrated and continuous deployment velocity is to eliminate potential bottlenecks by giving student teams to receive early and continuous feedback. To this end, we propose a continuous feedback and delivery mechanism for managing the life-cycle of a graduation project through draft proposal, literature review, requirements gathering, design, implementation and testing which should produce intermediate outputs at predefined intervals. Most importantly, our approach makes it possible to quantify most of the activities involved in life-cycle process with various rubrics (i.e. measurement scales) that have been purposefully developed. The proposed model promotes the fact that all improvements should be monitored, evaluated and documented. The results of this study indicate that students who were managed using this approach produced better project deliverables and ultimately have delivered better and successful projects.

Transformable reflector structure with V-folding rods

A new design of space deployable reflector is presented. In particular, we consider closed-chain system (with central network), which as a result of transformation reaches the conical shape. In conformity with the technical specifications, individual parts of the system perform the simultaneous motion in the radial and axial directions. The main motion of the system produced by geometric constraints is studied, i.e., we consider the degree of structural motion. Parametric degrees of freedom caused by technological errors, modes of motion, types of load or deployment velocity are not taken into consideration at this stage. A peculiar feature of the deployable structure presented in the paper is that, as compared with analogous structures, for connecting the sections with one another there is no need of using synchronization devices in both—upper and lower kinematic chains simultaneously. This structural mechanism is a differential lever mechanism, the driving elements of which enable us to obtain the desired law of motion of every characteristic link. The kinematic model represents the whole system. Therefore, we can construct the function of position of the lever mechanism and also the kinematic functions of transmission. For the preliminary investigation of the structure and making possible changes in it, two mathematical models have been constructed by means of the ANSYS software using the Ansys Parametric Design Language. The degrees of freedom of the hinges are simulated in local coordinate systems and are as much as possible approximated to the real model. Calculations are performed for various kinds of loads and appropriate results are obtained.

Modeling orbital tether system deployment with limitations on the deployment speed

The problem of modeling the operation of special equipment intended for modeling orbital tether system deployment is studied. During the deployment of an orbital tether system the tether tension force control program is used that takes into account limitations on the deployment velocity. A parametric boundary problem is solved for the program of controlling the deployment of an orbital tether system. A kinematic scheme of the equipment, consisting of an engine that simulates the Earths gravitation and a tether deployment mechanism, is created. Based on the kinematic scheme, a dynamic scheme with control path feedback on tether deployment velocity and tether tension is created. The deviation control principle is implemented: control is realized on the deviation of the real value of the parameter under consideration from its program value. The magnification ratio of the controlled value deviation from the program values is used as the controlled value in transient optimization. The numerical simulation of the test bench operation performed in the MapleSim 7 environment shows acceptable quality of transient tether deployment velocity and tether tension.

Simulation Analysis of Designing a New Technique KER Warhead

The major technique of an air-defense warhead is to improve the damage after effect. Therefore, a new Kinetic Energy Rod (KER) warhead named profiled rod warhead is proposed in this paper. The detonation process is simulated by ANSYS/LS-DYNA, and the deployment velocity and initial flight attitude of rod are achieved. Rigid body dynamics equations of rod, which accounts for the influence of air resistance, are set up to predict the flight trajectory of long-distance. The results show that profiled rods are conducted to determine a higher penetrability compared with traditional cylindrical rods, and the profiled rods may provide a better penetration angle that still maintains a significant penetrability against projectiles when the rods move off long-distance range.

Damage Radius Study of Gimbaled Forward-Firing Warhead to Tactical Ballistic Missile

Gimbaled forward-firing warhead (GFFW) is one of the most efficient types for killing enhancement that exist today. This is because almost all the fragments of the warhead are deployed to the targets direction. Static explosion experiment was performed to investigate the spatial distribution of the spray pattern as well as its deployment velocity. The cone angle (θs) of fragments bundle at static conditions is 15°, and fragments in the mesial area is dense than that in the marginal area. The average velocity of the fragment in mesial area is 1712m/s, and that in marginal area is 1408m/s. In conjunction with deployment experiments, damage radius study is conducted with the basic criterion that one fragment must hit target payload at least. Damage radius at the dynamic conditions is 150m~165m, which is more farther than conventional uniform warhead.

Study on a Rope Deployment Cascade Mechanism

Aimed at a rope deployment mechanism, under the hypothesis that the rope can not extend, the kinematic relationship between the rods and the multi-rigidbody geostatic model of the mechanism are established. Through the simulation and the mechanical analysis of the deployment process, the prototype deployment experiment had been done with controlling of the trace of the deployment velocity. The consequence shows the displacement, power consumption and disturbance of the mechanism accord with the expectation value of the theoretic model. It more shows our model could reflect the characteristic of this kind of mechanism, and also provides the gist for the deployment mechanism design。