Link Length Research Articles

기구학 해석을 이용한 바이올린 활 연주 로봇팔의 최소 링크 길이 계산

For a violin playing robot to be successful as an entertainment robot it needs to portray the image of a human arm playing the violin. Hence it is desired that the robotic manipulator has an articulated structure similar to the human arm. Since shorter link lengths result in smaller link weight, smaller actuator size/weight, and thus fast motion capabilities of the manipulator, it is crucial to determine the minimum link lengths of the manipulator. This paper presents a computation method of the minimum link lengths required for the bow motion and the kinematic design of the violin bow playing robot arm. The workspace of the bow playing arm is analyzed using the geometric dimensions of the bow and the violin bridge. The bow frog motion paths are computed for four violin strings. It is shown that a planar RRR mechanism can generate the motion required for violin bow playing robot, and the minimum link lengths of the manipulator are found that result in the robot workspace encompassing the bow frog motion paths and that avoids the singularities in the robot motion path.

Investigation of the Mounting Position of a Wearable Robot Arm

In a wearable robot arm, the minimum joint configuration and link length must be considered to avoid increasing the burden on the user. This work investigated how the joint configuration, length of arm links, and mounting position of a wearable robot arm affect the cooperative and invasive workspaces of the overall workspace. We considered the joint configurations and link lengths of passive and active joints in our proposed wearable robot arm, which is called the Assist Oriented Arm (AOA). In addition, we comprehensively studied the position of the arm on the user. As a result, three locations around the shoulders and two around the waist were chosen as potential mounting sites. Furthermore, we evaluated the weight burden when the user mounted the wearable robot arm at those positions.

Interaction of flange and web slenderness, overstrength factor and proposed stiffener arrangements for long links

This paper is aimed to investigate the interaction of flange and web slenderness ratio, overstrength factor and also to improve the behavior of long links. Pursuant to these goals, 150 numerical models of different long links were developed and exposed to cyclic loading protocol mandated by AISC 341. Link length ratio, flange and web slenderness and stiffener configurations are selected as parameters. The results revealed that the flange slenderness ratio can be relaxed to 0.38(E/Fy)0.5 for long links if the web slenderness ratio is <1.5 (E/Fy)0.5. The shear capacity of long links decreases as the link length ratio increases. The results of shear capacity showed the overstrength factor required by AISC 341 overestimates the shear capacity; therefore, two different equations to predict the overstrength factor for long links are proposed. The stiffener configuration recommended by AISC 341 limits the potential of long links. To mitigate this drawback, different stiffener configurations are proposed to empower the behavior of long links. Using additional one stiffener at each link ends can enhance shear strength, energy dissipation and plastic rotation capacities by 25%, 447% and 322%, respectively. When two additional stiffeners are introduced, these ratios modify to 29%, 479% and 332%. Moreover, rupture index values are utilized to verify proposed stiffener configurations further.

Molecular Dynamics Study on the Crystallization Process of Cubic Cu–Au Alloy

In this study, molecular dynamics simulations have been used to study the influencing factors, such as the time of each heating step, temperature, and annealing time, on the structure and crystallization process of Cu–Au alloy. The results show that when the temperature increased, the crystallization process decreased, and the structure gradually turns to the liquid state, and vice versa. When increasing the time of each heating step and the annealing time, the crystallization process increased, then increased the most at the glass temperature, Tg = 550 K. During the phase transition, link length (r), total energy (Etot), size (l), number of FCC, HCP, and Amor structural units have a significant change. The obtained results of Cu-Au alloy can serve as a basis for future experimental studies.

Gene expression model to estimate the overstrength ratio of short links

Short links are used as fuse members in Eccentric Braced Frames (EBFs), hybrid coupled-wall systems, and self-anchored suspension steel bridges. Compared to the intermediate and long links, short links have superior performance such as high strength and plastic deformation capacity. However, several researchers observed a considerably high overstrength ratio for short links. This study found that the AISC Seismic Provisions underestimate the plastic shear strength of short links, the experimental results of 103 specimens showed that only 8% of the specimens comply with the recommended AISC Seismic Provisions overstrength value of 1.25. The average of all data is 1.67 with COV 17.6% and RMSE 0.732. Therefore, a genetic expression-based model (GEP) was proposed to estimate the plastic shear strength of short links. A 96% of the overstrength ratio calculated by GEP of the 103 specimens comply with the recommended AISC overstrength value of 1.25. The average of the GEP overstrength values is 1.00 with COV 13.6% and RMSE 0.136. The GEP model considers the contribution of six variables such as the flange slenderness ratio (bf/tf), the web slenderness ratio (d/tw), the flange to web area ratio (Af /Aw), the flange force (Af fyflange), the web force (Awfyweb), and the link length ratio e/(M/V). Unlike the AISC overstrength ratio estimates, the GEP predictions are not sensitive to the variables. This is evidence that the GEP model is an inclusive and efficient equation to estimate the overstrength ratio of short links.

Pulse width shortening combinations (PWSC) for ultra-dense WDM systems and calculation of PWSE

Abstract Optical communication systems introduced paradigm shift in the forte of data transmission at higher speeds and over longer distances where, on contrary electrical transmission systems failed due to higher amplitude degradation, interferences and lower bandwidths. However, pulse width increase (PWI) in the optical fiber limits the overall distance reach and also introduces more bit errors which needs to addressed. So far, pulse width shortening fibers (PFs) and fiber Bragg grating (FG) used individually in most of the reported studies, however pulse width shortening (PWS) took either high cost (in PFs) or lower PWS efficiency (PWSE) (in FG). Therefore, in this research manuscript, we made emphasis on the combined PWS effects of diverse techniques such as optical phase conjugation (OC), FG and PFs in ultra-dense wavelength division multiplexing (WDM) system. Total link length of 400 km has been covered in 128 channels ultra dense wavelength division multiplexing (UDWDM) system at 10 Gbps by incorporating diverse combined organized placements of FG, OC and PFs such as FG-PF, OC-PF and FG-PF-OC. Results revealed that economical and maximum PWSE arrangement for proposed system is FG-PF-OC.

Optimization of Link Length Fitting between an Operator and a Robot with Digital Annealer for a Leader-Follower Operation

In recent years, the teleoperation of robots has become widespread in practical use. However, in some current modes of robot operation, such as leader-follower control, the operator must use visual information to recognize the physical deviation between him/herself and the robot, and correct the operation instructions sequentially, which limits movement speed and places a heavy burden on the operator. In this study, we propose a leader-follower control parameter optimization method for the feedforward correction necessitated by deviations in the link length between the robot and the operator. To optimize the parameters, we used the Digital Annealer developed by Fujitsu Ltd., which can solve the combinatorial optimization problem at high speed. The main objective was to minimize the difference between the hand coordinates target and the actual hand position of the robot. In simulations, the proposed method decreased the difference between the hand position of the robot and the target. Moreover, this method enables optimum operation, in part by eliminating the need for the operator to maintain an unreasonable posture, as in some robots the operator’s hand position is unsuitable for achieving the objective.

Routing in spatial networks based on shortest path length

In many complex networks, such as communication networks, power grids, and transportation networks, the main task is load transmission from sources to destinations. Therefore, the transmission throughput is a very important indicator to measure the network performance, and improving the throughput becomes one of the hotspots in the research of these complex networks. Many researchers have proposed different routing algorithms to improve the network throughput. However, few of them considered the spatial location of nodes in the network. Indeed, many real-world networks can be modeled by spatial networks, where the spatial location of nodes plays a vital role in determining the structure and dynamic behaviors of such networks. Specifically, when the locations of nodes are considered, each link has a length. And the shortest path may have different meaning. Traditionally, the shortest path indicates the path which passes the least number of links from source to destination, or the least number of hops. However, when the length of link is taken into account, the least number of links does not mean the least summation of link lengths along the path. The latter can be called the shortest path length. To this end, we proposes an efficient routing strategy for spatial networks based on the shortest path length in this work. In order to test the effectiveness of the algorithm, the network throughput &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}${R}_{\rm c}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211621_M1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211621_M1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; is used, at which the network changes from a free flow state to a congestion state, to measure the performance of the network. Simulations of homogeneous and heterogeneous spatial networks show that compared with the traditional least number of hops routing strategy, the routing algorithm based on the shortest path length proposed in this paper can effectively improve the throughput of the network. The routing algorithm proposed in this paper can be applied to many real-world spatial networks for improving their performances.

Allocating Defense and Recovery Resources for Spatial Networks against Cascading Failures

This paper proposes the models of allocating defense and recovery resources for spatially embedded networks, respectively, both of which consider the length of links as the allocation cost. In the defense model, the amount of defense resources required for each zone depends on the total length of the links they contain. It is found that dispersed allocation performs better and that parameters that allow for a uniform distribution of link lengths produce better results. In the recovery model, a shortest link hierarchical recovery (HSR) strategy is proposed and proved to be more effective. In this strategy, the number of repaired links plays a decisive role in the recovery results, while the total length of the links does not seem to matter when the number is constant. In addition, a number of different parameters are adopted to validate the qualitative conclusions. These models might yield insights into studying and protecting spatial infrastructure systems.

Высокоскоростные одномодовые вертикально-излучающие лазеры спектрального диапазона 1550 нм

The results of complex studies of static and dynamic performance of 1550 nm-range VCSELs, which were created by direct bonding (wafer fusion technique) InAlGaAs/InP optical cavity wafers with AlGaAs/GaAs distributed reflector wafers grown by molecular beam epitaxy, are presented. The VCSELs with a buried tunnel junction diameter less than 7 μm demonstrated a single-mode lasing with a side-mode suppression ratio more than 40 dB; however, at diameters less than 5 μm, a sharp increase in the threshold current is observed. It is associated to the appearance of a saturable absorber due to penetration of optical mode into the non-pumped regions of the active region. The maximum single-mode output optical power and the–3 dB modulation bandwidth reached 4.5 mW and 8 GHz, respectively, at 20°C. The maximum data rate at 20ºC under non-return-to-zero on-off keying modulation was 23 Gb/s for a short-reach link based on single-mode fiber SMF-28. As the length of the optical link increased up to 2000 m, the maximum data rate dropped to 18 Gbit/s. The main factors affecting the high-speed operation and data transmission range are defined and discussed, and the further ways to overcome themit are proposed.

Kinematic Optimization of 6DOF Serial Robot Arms by Bio-Inspired Algorithms

Robotic systems are essential to technological development in the industrial, medical, and aerospace sectors. Nevertheless, their use in different applications requires that the robot have the best possible execution efficiency. For this, a robot with specific optimized characteristics is necessary to impact the performance of the specific task. Different techniques have been used in robot optimization, the most widely used being genetic algorithms (GA) and particle swarm optimization (PSO). However, there are optimization algorithms with high convergence speeds inspired by animal behavior, whose application in robot optimization has not been reported. In this work, bio-inspired algorithms Harris hawks optimization (HHO) and Grey wolf optimizer (GWO) are applied to a six-degree-of-freedom (6DOF) robot arm design through kinematic optimization. The lengths of the main robot links are optimized to improve the workspace volume and obtain a better-conditioned robot using the structural length index (SLI) and global condition index (GCI) as objective functions. A comparison is made between the proposed algorithms and GA and PSO regarding convergence speed, computational load, and optimality. Similar behavior has been found for HHO, GWO, and PSO compared to GA for both indexes. For the GCI problem, an average improvement of 14% was found when optimizing an industrial robot arm. Furthermore, multiple runs experiment is performed to test the robustness of the algorithms. The results show that HHO is the best technique to obtain an optimal robot design because it needs less than ten iterations to provide a better result despite its computational load.

1550 nm range high-speed single-mode vertical-cavity surface-emitting lasers

The results of complex studies of static and dynamic performance of 1550 nm-range VCSELs, which were created by direct bonding (wafer fusion technique) InAlGaAs/InP optical cavity wafers with AlGaAs/GaAs distributed Bragg reflector wafers grown by molecular beam epitaxy, are presented. The VCSELs with a buried tunnel junction diameter less than 7 μm demonstrated a single-mode lasing with a side-mode suppression ratio more than 40 dB; however, at diameters less than 5 μm, a sharp increase in the threshold current is observed. It is associated to the appearance of a saturable absorber due to penetration of optical mode into the non-pumped regions of the active region. The maximum single-mode output optical power and the -3 dB modulation bandwidth reached 4.5 mW and 8 GHz, respectively, at 20oC. The maximum data rate at 20oC under non-return-to-zero on-off keying modulation was 23 Gb/s for a short-reach link based on single-mode fiber SMF-28. As the length of the optical link increased up to 2000 m, the maximum data rate dropped to 18 Gbit/s. The main factors affecting the high-speed operation and data transmission range are defined and discussed, and the further ways to overcome themit are proposed. Keywords: VCSEL, wafer fusion, molecular beam epitaxy, single-mode operation, high-speed performance.

Kinematic Calibration of a 4PPa-2PaR Parallel Mechanism With Subchains on Limbs

The newly developed 4PPa-2PaR parallel mechanism has subchains on its limbs, and the imperfect assembly process causes the kinematic error. The conventional matrix-based method is difficult to set up its kinematic error model, as the kinematic constraints cannot be represented by the homogenous transformation matrix intuitively. In this work, the actual kinematic model is established using a vector-based method, considering the nonideal lengths of links and misalignment of active joints&#x2019; home sensors. Thereby, the kinematic constraints of the mechanism are intuitively incorporated into the model, and the deviations of kinematic parameters are identified by the Levenberg&#x2013;Marquardt algorithm. To achieve error compensation using the inverse of the actual kinematic model, a flange with three collinear reflector holders is designed and mounted on the moving platform, and a three-point measurement method is utilized to capture its pose without using a tracker-machine control sensor (T-MAC). Another flange for reflector holders is designed and mounted on the active joint for setting up the base frame so that all measurement data are transformed from the laser tracker&#x2019;s frame to the base frame to complete the calibration process. Experiments are conducted on the testbed to validate the effectiveness of the proposed calibration method.

Development of a programmable robotics arm using MATLAB

A robotic arm is a manipulator for robots that can be programmed to do tasks that a human arm can perform. As with an articulated robot, the manipulator's linkages are joined by joints that enable either rotational motion or linear displacement. A kinematic chain may be thought of as being formed by the manipulator's linkages. The robot arms may be operated autonomously or manually and are capable of performing a wide range of activities with high precision. Both stationary and wheeled versions of the robotic arm may be used in industrial and domestic settings. This study examines a robotic arm that uses accelerometers as sensors to collect data on natural arm motions to mimic those of a human arm. This method of control allows greater flexibility in controlling the robotic arm rather than using a controller where each actuator is controlled separately. The processing unit takes care of each actuator’s control signal according to the inputs from an accelerometer, to replicate the movements of the human arm. Robotic arms are programmed manipulators that have a striking resemblance to a human arm in terms of design. Joints connect the various parts of the arm. Robotic arm joints, in contrast to the rotating joints seen in human arms, may be capable of varying the link length (prismatic joints). The term

Power and Energy Efficiency of Multilevel Baseband Transmission Systems: Analysis, Optimization and Improvements

Power and energy consumption of communication net-works contribute to the resource demand and hence they impact the sustainability of the society. Transmission links form basic parts ofcommunication networks and thus they add to the overall communica-tio nnetworlks' resourcedemand. Therefore, it is important to optimize transmission links in order to support the energy-efficient design ot communication networks. In transmission systems the constellation size in general is a degnee of freedom when designing or adapting a transmission link. In this article, multilevel baseband transmission via additive white Gaussian noise (AWGN) channels and over copper cables is optimized with respect to minimum power and energy demand, respectively - for the relevant case of given throughput and fixed transmission quality of a transmission link. The results are two-fold: In the AWGN case the minimum power and energy is utilized at the smallest possible constellation size. In case of band- limited base band transmission over twisted-pair copper wires with linear equalization the optimum constellation size increases as the band limitation becomes stronger, ie, as the cable gets longer al fixed bit rate or as the bit rate is increased at fixed link length. The optimization of the constellation size enables significant power and energy savings per link in the range of 25 % to approximately 90 % compared to a conventional two-level baseband system.

Fundamental study of optimum design of physical pendulum type of centrifugal pendulum vibration absorber in automatic transmission for cars

The centrifugal pendulum vibration absorber (CPVA) is developed to suppress the torsional vibration of automatic transmission. However, the natural frequency of the CPVA varies due to the nonlinear when the vibration amplitude of CPVA is large. To overcome this problem, a new physical pendulum type of centrifugal pendulum vibration absorber is developed. Physical pendulum type of centrifugal pendulum vibration absorber is possible to rotate depending on the control angle. In this study, the optimal design for the physical pendulum type of centrifugal pendulum vibration absorber is discussed by changing the parameters such as the link length ratio and the control angle.

Impact of mixed tolerance combination on the geometric position and torques of a four-bar kinematic chain using genetic algorithm

Effect of manipulators individual link’s allocated design tolerance will be able to sense during its output performance only. It is the duty of design engineers to allocate optimum tolerance range for each link to satisfy both the quality and manufacturing cost of the manipulators. In this paper, mixture of Fine (F), Medium (M) and Coarse (C) type tolerances will be considered for the links length of a four-bar kinematic chain. Based on Genetic Algorithm, this paper obtains optimal link combinations and minimizes the functional cost which includes minimal error in the target performance, minimized joint torques and reduced assembly cost while applying the concept of mixed tolerance types. Moreover, the optimal link combinations provide relaxation in manufacturing in terms of comparatively wide tolerance for few of the links in an assembly which leads to save the manufacturing cost and time.

干旱胁迫对不同根型苜蓿根系构型的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱胁迫对不同根型苜蓿根系构型的影响 DOI: 10.5846/stxb202109042504 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（32160327）；甘肃省重点研发计划项目（20YF3FA011） Effects of drought stress on root architecture of different root- type alfalfa Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用盆栽试验，比较播种当年及生长第2年对照、中度、重度干旱胁迫下根茎型、直根型、根蘖型苜蓿根系平面、立体几何构型和分形特征差异，以探究不同根型苜蓿对干旱的适应策略。结果表明：随干旱胁迫增加，各根型苜蓿根系总长度、总表面积、总体积和平均直径均减小；各根型苜蓿的根系拓扑指数较小，根系分支模式为叉状分支结构；各根型苜蓿的根系具有较好的分形特征，其分形维数较小，而分形丰度和平均连接长度均较大，表明其根系分支相对简单，但空间拓展能力强，有利于对营养空间的占有；各根型苜蓿的总分支较小、逐级分支率较大，有助于资源的快速获取和促进主根的向下生长。对根系构型参数进行主成分分析，根系总表面积、分形丰度、根长、根体积、分形维数和比根长6个根系构型参数能较好反映不同根型苜蓿根系构型特征。重度胁迫下，根茎型、根蘖型苜蓿的根系总长度、总表面积、总体积、比根长、比表面积、平均连接长度均大于直根型苜蓿，表明根茎型、根蘖型苜蓿适应干旱环境的能力强于直根型苜蓿。 Abstract:To investigate the ecological adaptation strategies of drought stress on root plane and stereo geometry architecture and fractal characteristics, pot experiment using three root types of alfalfa (rhizomatous rooted Medicago sativa ‘Qingshui’, tap rooted M. sativa ‘Longdong’, creeping rooted M. varia Martin. ‘Gongnong’ No.4) as the experimental materials was conducted to set up the drought treatment experiments. The results showed that the total root length, total surface area, total root volume and root average diameter of different root-type alfalfa decreased with increasing of drought concentration. The root topological indices of different root-type alfalfa were small, and the root branching patterns were herring-bone-like. The roots of different root-type alfalfa had obviously fractal characteristics, and the fractal dimension was small, while the fractal abundance and the average link length were large, which indicated that they had simple root architecture and high ability to expand living space. Smaller branching ratio and larger stepwise branching rate of different root-type alfalfa were helpful to speed resource acquisition and promote taproot growth downward. Root architecture parameters were analyzed by the principal component analysis. The parameters of total surface area, fractal abundance, total root length, total root volume, fractal dimension, and specific root length could well present the root architecture characteristics of different root-type alfalfa. Under severe stress, the total root length, total surface area, total root volume, specific root length, and specific surface area of rhizomatous rooted and creeping rooted alfalfa were higher than tap rooted alfalfa, which showed that the adaptation to drought environment of rhizomatous rooted and creeping rooted alfalfa were stronger than that of tap rooted alfalfa. 参考文献 相似文献 引证文献

Performance analysis of wavelength division multiplexing MDM-PON system using different advanced modulations

Abstract Mode division multiplexing (MDM) is very competent next generation multiplexing technique and is becoming popular among researchers these days. In this research article, an integrated passive optical network (PON) using MDM and wavelength division multiplexing (WDM) is proposed at 25 Gbps over 3 km multimode fiber (MMF) link distance. For MDM, diverse Laguerre–Gaussian (LG) such as LG12, LG15, LG18, LG111 and LG114 are incorporated and also for cost reduction, vertical cavity surface emitting laser (VCSEL) is located in optical line terminal (OLT). Performance of diverse advanced modulations such as compressed spectrum return to zero (CSRZ), duo-binary return to zero (DRZ) and modified duo-binary return to zero (MDRZ) is evaluated and compared with non-return to zero (NRZ) in terms of Bit error rate (BER) at varied MMF link lengths. Results revealed that CSRZ performance stand out and NRZ provide worst performance.

How local street networks contribute to the traffic accident occurrence: Mersin city case

In this study, the issue of the accident frequency/occurrence in local residential streets where vehicle counts are not obtained is discussed. The accident reports received from the Ministry of Interior include fatal and injury accidents. But since the number of deadly accidents is minor, a binomial regression was not employed in the statistical analysis. This study investigates the role of morphological characteristics of the street network where main arterials are excluded in the safety of residential neighborhoods of Mersin, Turkey. Results showed that commercial and industrial uses generate more traffic than residential neighborhoods, therefore, responsible for higher rates of accidents. The number of vehicles, employment, and population increase the accident rate. Empirical model results showed that population density, street length per capita (meters), and number of intersections significantly affect accident occurrence. Number of intersections increases accident frequencies while street length per capita reduces. In contrast, the number of links, street density, link to node ratio, and average link length have no significant effect on accident occurrence. Traffic safety cannot be achieved if the street length is not proportional to the number of vehicles. In addition, street design is also a matter of efficient use of urban space.