Lightweight Mechanical Structure Research Articles

Study on the Influence of Lightweight Mechanical Structure on UAV Dynamic Response Characteristics and Control Strategy Optimization

Study on the Influence of Lightweight Mechanical Structure on UAV Dynamic Response Characteristics and Control Strategy Optimization

Efficient inverse-designed structural infill for complex engineering structures

Inverse design of high-resolution and fine-detailed 3D lightweight mechanical structures is notoriously expensive due to the need for vast computational resources and the use of very fine-scaled complex meshes. Furthermore, in designing for additive manufacturing, infill is often neglected as a component of the optimized structure. In this paper, both concerns are addressed using a so-called de-homogenization topology optimization procedure on complex engineering structures discretized by 3D unstructured hexahedrals.Using a rectangular-hole microstructure (reminiscent to the stiffness optimal orthogonal rank-3 multi-scale) as a base material for the multi-scale optimization, a coarse-scale optimized geometry can be obtained using homogenization-based topology optimization. Due to the microstructure periodicity, this coarse-scale geometry can be up-sampled to a fine single-scale physical geometry with optimized infill, with only a minor loss in structural performance and at a fraction of the cost of a fine-scale solution. The upsampling on 3D unstructured grids is achieved through stream surface tracing, aligning with the optimized local orientations. The periodicity of the physical geometry can be tuned, such that the material serves as a structural component and also as an efficient infill for additive manufacturing designs.The method is demonstrated through three examples of varying geometrical complexity. It achieves comparable structural performance to “brute force” state-of-the-art methods but stands out for its significant computational time reduction. By allowing multiple active layers, the mapped solution becomes more mechanically stable, leading to an increased critical buckling load factor without additional computational expense. The control of active layers also provides direct control over the internal structure, i.e., infill, ensuring that the infill is incorporated as a structural component and enhancing the manufacturability of the de-homogenization procedure. Furthermore, the proposed approach exhibits promising results, achieving volume fractions and weighted compliance values within 5% of the large-scale SIMP model, while demonstrating a computational efficiency improvement ranging from 10 times to over 250 times.

A novel passive shoulder exoskeleton for assisting overhead work.

Shoulder exoskeletons (SEs) can assist the shoulder joint of workers during overhead work and are usually passive for good portability. However, current passive SEs face the challenge that their torque generators are often attached to the human arm, which adds a significant amount of weight to the user's arms, resulting in additional energy consumption of the user. In this paper, we present a novel passive SE whose torque generator is attached to the user's back and assists the shoulder joint through Bowden cables. Our approach greatly reduces the weight on the user's arms and can accommodate complex shoulder joint movements with simple and lightweight mechanical structure based on Bowden cables. In addition, to match the nonlinear torque requirements of the shoulder joint, a unique spring-cam mechanism is proposed as the torque generator. To verify the effectiveness of the device, we conducted a usability test based on muscle activations of 10 healthy subjects. When assisting overhead work, the SE significantly reduced the mean and maximum electromyography signals of the shoulder-related muscles by up to 25%. The proposed SE contributes to further research on passive SE design to improve usability, especially in terms of reducing weight on human arms.

FAST-Hex—A Morphing Hexarotor: Design, Mechanical Implementation, Control and Experimental Validation

We present FAST-Hex, a micro aerial hexarotor platform that allows to seamlessly transit from an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">underactuated</i> to a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fully actuated</i> configuration with only one additional control input, a motor that synchronously tilts all propellers. The FAST-Hex adapts its configuration between the more efficient but underactuated, collinear multirotors, and the less efficient but full pose tracking, which is attained by noncollinear multirotors. On the basis of prior work on minimal input configurable micro aerial vehicle, we mainly stress three aspects: Mechanical design, motion control, and experimental validation. Specifically, we present the lightweight mechanical structure of the FAST-Hex that allows to only use one additional input to achieve configurability and full actuation in a vast state space. The motion controller receives as input any reference pose in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbb {R}^3\times \mathrm{SO}(3)$</tex-math></inline-formula> (3D position + 3D orientation). Full pose tracking is achieved if the reference pose is feasible with respect to actuator constraints. In case of unfeasibility, a new feasible desired trajectory is generated online giving priority to the position tracking over the orientation tracking. Finally, we present a large set of experimental results shading light on all aspects of the control of the FAST-Hex.

Design and Modeling of AMaSED-2: A High Temperature Superconducting Demonstrator Coil for the Space Spectrometer ARCOS

Magnetic spectrometers detect the rigidity of charged particles by measuring the bending of their trajectories as they pass through a magnetic field. ARCOS is a proposal for a next generation magnetic spectrometer in space with a bending strength of 3 T <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\,$</tex-math></inline-formula> m at an operating temperature of 20 K. ARCOS is based on a 12-coil toroidal HTS magnet. Within the HTS Demonstrator Magnet for Space (HDMS) project, we have designed and built AMaSED-2, a small-scale demonstrator coil for the ARCOS magnet. AMaSED-2 consists of two individually built no-insulation HTS ReBCO pancake coils with racetrack-like shapes. The exclusion of electrical insulation material between adjacent winding turns enables self-protection against quenches. The winding blocks are surrounded by copper bands functioning as current leads and layer jumps. AMaSED-2 is supported by a lightweight mechanical structure made from aluminum alloy. We describe the design of AMaSED-2 and present a simple mathematical circuit model for no-insulation coils.

Ortholeg 2.0 ‑ Design of a Transparent Active Orthosis

In this work we propose a conceptual solution for performance limitation observed in many lower limb active orthosis. The concept is called transparent orthosis, and its objective is to improve the user walking experience to a more natural level, through the design of a lightweight and ergonomic mechanical structure, while using an autonomous and interactive software architecture. The details of transparency are shown through the design and development of a real transparent orthosis, called Ortholeg 2.0. Some aspects of the presented concept were tested in a previous developed device, the Ortholeg orthosis.

軽量機械構造物を対象とした摩擦滑りを有する地震時転倒防止機構（基本設計仕様の検討と性能実証試験）

軽量機械構造物を対象とした摩擦滑りを有する地震時転倒防止機構（基本設計仕様の検討と性能実証試験）

Extra lightweight mechanical support structures with the integrated cooling system for a new generation of vertex detectors

The performance of new extra lightweight mechanical support structures with the integrated liquid cooling system for monolithic silicon pixel detectors has been investigated. These detectors will be used to upgrade the inner tracking system in the ALICE experiment at the CERN Large Hadron Collider. The extra lightweight mechanical support structures, together with the novel pixel detectors, provide a record-breaking total radiation length of 0.3% X0 per layer, which will make it possible to considerably extend the physical program of investigations of the quark-gluon plasma in ultra-relativistic heavy-ion collisions at the Large Hadron Collider. This is particularly important in measuring the yields of heavy-flavor hadrons and low-mass dileptons with low transverse momenta. The experimental results of the thermal tests and the comparative analysis of five samples of extra lightweight mechanical support structures for monolithic silicon pixel detectors are presented. The high efficiency of heat drain using the liquid cooling system for a power density as high as 0.5 W/cm2 is shown.

NREL 5MW 풍력 터빈 타워의 기계적 하중 완화

풍력 터빈의 용량이 대형화될수록, 난류성분에 의한 풍력 터빈 구조물의 하중을 최소화시키는 하중완화 제어가 점차 중요해진다. 한번 설치되면 20 년 이상 작동되어야 하는 풍력 터빈 구조물은 끊임없이 바람에 의한 하중에 노출되는데, 이것이 적절하게 제어되지 않으면 풍력 터빈의 회전 반복운동에 의하여 피로파괴에 이르게 될 가능성이 커진다. 본 논문은 NREL 5MW 풍력 터빈을 대상으로 타워의 하중을 저감시키는 제어시스템을 설계하고, 이의 성능을 평가하는 내용을 담고 있다. 타워의 하중 완화제어시스템을 설계하려면 5MW 풍력 터빈의 동적 특성이 먼저 파악이 되어야 하며, 파워 커브를 추종하는 기본 제어시스템의 설계가 선행되어야 한다.

Recent progress in sensor- and mechanics-R&D for the Belle II Silicon Vertex Detector

The Belle experiment at the KEKB electron/positron collider in Tsukuba (Japan) was successfully running for more than ten years. A major update of the machine to SuperKEKB is now foreseen until 2015, aiming a peak luminosity which is 40 times the peak value of the previous system. This also requires a redesign of the Belle detector (leading to Belle II) and especially its Silicon Vertex Detector (SVD), which surrounds the beam pipe.The future Belle II SVD will consist of four layers of double-sided silicon strip sensors based on 6in. silicon wafers. Three of the four layers will be equipped with trapezoidal sensors in the slanted forward region. Moreover, two inner layers with pixel detectors based on DEPFET technology will complement the SVD as innermost detector. Since the KEKB-factory operates at relatively low energy, material inside the active volume has to be minimized in order to reduce multiple scattering. This can be achieved by arranging the sensors in the so-called “Origami chip-on-sensor concept”, and a very light-weight mechanical support structure made from carbon fiber reinforced Airex foam. Moreover, CO2 cooling for the front-end chips will ensure high efficiency at minimum material budget.In this paper, an overview of the future Belle II SVD design will be given, covering the silicon sensors, the readout electronics and the mechanics. A strong emphasis will be given to our R&D work on double-sided sensors where different p-stop layouts for the n-side of the detectors were compared. Moreover, this paper gives updated numbers for the mechanical dimensions of the ladders and their radii.

The Belle II Silicon Vertex Detector

Abstract The KEKB factory (Tsukuba, Japan) has been shut down in mid-2010 after reaching a total integrated luminosity of 1ab -1 . Recently, the work on an upgrade of the collider (SuperKEKB), aiming at an ultimate luminosity of 8×10 35 cm -2 s -1 , has started. This is 40 times the peak value of the previous system and thus also requires a redesign of the Belle detector (leading to Belle II), especially its Silicon Vertex Detector (SVD), which surrounds the beam pipe. Similar to its predecessor, the future Belle II SVD will again consist of four layers of double-sided silicon strip sensors (DSSD), but at higher radii. Moreover, a double-layer PiXel Detector (PXD) will complement the SVD as the innermost sensing device. All DSSDs will be made from 6” silicon wafers and read out by APV25 chips, which were originally developed for the CMS experiment. That system was proven to meet the requirements for Belle II in matters of occupancy and dead time. Since the KEKB factory operates at relatively low energy, material inside the active volume has to be minimized in order to reduce multiple scattering. This can be achieved by the Origami chip-on-sensor concept, including a very light-weight mechanical support structure made from carbon fiber reinforced Airex foam. Moreover, CO2 cooling for the front-end chips will ensure high efficiency at minimum material budget.

21st Century Kinematics: Synthesis, Compliance, and Tensegrity

As we move into the second decade of the 21st century, we can identify three research trends that we can expect to persist into the future. They are the analysis and synthesis of (i) spatial mechanisms and robotic systems, (ii) compliant linkage systems, and (iii) tensegrity and cable-driven systems. In each case, we find that researchers are formulating and solving polynomial systems of total degrees that dwarf those associated with major kinematics problems of the previous century.

D311 渦電流減衰効果を応用した軽量機械構造物用実機型減衰装置の性能評価(OS5 機械構造物の耐震・免震・振動制御2)

D311 渦電流減衰効果を応用した軽量機械構造物用実機型減衰装置の性能評価(OS5 機械構造物の耐震・免震・振動制御2)

Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1mm thickness and higher) and 3D multi-material objects (for example, 100mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc.

420 渦電流減衰効果を応用した軽量機械構造物用減衰装置に関する研究

A base-isolation and vibration control technique has been applied positively to architectural and civil structures after Kobe earthquake, and now the techniques are adopted as general vibration reduction technique for many structures. In such situation, an application of the vibration attenuation device to the small-scale structure has been carried out actively in recent years. Especially, in the important institution of the cities such as a refuge place, a hospital, a school, an information and a communication institution where function maintenance is needed, it is important to maintain its performance of the machinery and equipment in the facility with an upgrade of structural seismic safety. Moreover, in the future, upgrading of seismic safety of the particular equipments is urgent business. This study has been examined a low cost and compact damping device for base-isolation system of light weight mechanical structures like computer server racks. In this paper, the experimental and analytical results on basic performances of the damping device using damping effect caused by eddy current.

2027 マルエージング鋼の回転曲げ荷重下におけるギガサイクル疲労特性に関する研究(S11-1 高強度鋼・高硬度鋼の超高サイクル疲労,S11 金属材料の超高サイクル疲労特性の解明)

Maraging steel is one of typical high strength steels used for light-weight mechanical structures due to the significant high strength higher than 2000MPa. After solution treatment, an appropriate aging treatment was applied to this steel to provide the designed strength level. From this point of view, a number of specimens in the hourglass type were prepared and half of them were solution-treated, and remaining half were aged after solution treatment. Thus, ultra-long life fatigue properties for both kinds of specimens were examined in rotating bending, and very high cycle fatigue behaviors of both steels were compared with each other.

Force-closure workspace analysis of cable-driven parallel mechanisms

A cable-driven parallel mechanism (CDPM) possesses a number of promising advantages over the conventional rigid-link mechanisms, such as simple and light-weight mechanical structure, high-loading capacity, and large reachable workspace. However, the formulations and results obtained for the rigid-link mechanisms cannot be directly applied to CDPMs due to the unilateral property of cables. This paper focuses on the workspace analysis of fully restrained positioning mechanisms. Because the cable tension is the most essential issue to constrain the moving platform, the force-closure workspace is mainly studied. A general approach is proposed to check the force-closure condition. This condition is expressed in terms of the convex hull which encloses the origin. However, such a condition is formulated and expressed in high dimensions. To simplify the analysis, a recursive dimension reduction algorithm is proposed to check convex hulls in one dimension spaces. This algorithm is verified through simulation results of various CDPMs.

The mirror system of COMPASS RICH-1

The architecture and the properties of the mirror system of the COMPASS RICH-1 detector, composed by 116 spherical VUV reflecting units supported by a lightweight mechanical structure, are described.