Transactions of the Canadian Society for Mechanical Engineering
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Volume 37 (2013), Issue 4
Indoor localization of an omni-directional wheeled mobile robot
Sasha Ginzburg, Scott Nokleby
This paper presents a localization system developed for estimating the pose, i.e., position and orientation, of an omni-directional wheeled mobile robot operating in indoor structured environments. The developed system uses a combination of relative and absolute localization methods for pose estimation. Odometry serves as the relative localization method providing pose estimates through the integration of measurements obtained from shaft encoders on the robot’s drive motors. Absolute localization is achieved with a novel GPS-like system that performs localization of active beacons mounted on the mobile robot based on distance measurements to receivers fixed at known positions in the robot’s indoor workspace. A simple data fusion algorithm is used in the localization system to combine the pose estimates from the two localization methods and achieve improved performance. Experimental results demonstrating the performance of the developed system at localizing the omni-directional robot in an indoor environment are presented.
On elliptic self-motions of planar projective Stewart–Gough platforms
It has been previously shown that non-architecturally singular parallel manipulators of Stewart–Gough type, where the planar platform and the planar base are related by a projectivity, have either so-called elliptic self-motions or pure translational self-motions. As the geometry of all manipulators with translational selfmotions is already known, we focus on elliptic self-motions. We show that these necessarily one-parameter self-motions have a second, instantaneously local, degree of freedom in each pose of the self-motion. Moreover, we introduce a geometrically motivated classification of elliptic self-motions and study the so-called orthogonal ones in detail.
Numerical simulation of mixed convection within nanofluid-filled cavities with two adjadent moving walls
Mohammad Hemmat Esfe, Ariyan Zare Ghadi, Mohammad Javad Noroozi
In this study, nanofluid flow and heat transfer in a cavity with two moving lids are investigated. Governing equations are solved by finite volume approach using SIMPLE algorithm over a staggered gird system. The results show that when the moving lids have opposing effect, the streamlines contain two main vortices. By increasing the Richardson number, intensity of the vortex complying with buoyancy force increases, while intensity of the other vortex decreases. When the moving lids have aiding effect, the streamlines contain one the primary dominant vortex in which its strength increases with increase of the buoyancy force. In this case, rate of heat transfer is more than other cases.
Simulation of the static inflation of the passive left ventricle to an end-diastolic state
Matthew G. Doyle, Stavros Tavoularis, Yves Bougault
To initiate our simulations of canine left ventricle (LV) mechanics, we needed to specify an initial geometry and an initial wall stress distribution. Although there are sufficient measurements of LV geometries, there are no assessments of stresses under any conditions. To estimate a physiologically plausible range of stresses at end diastole, we have inflated an unloaded reference geometry using static pressure loads. The LV was modelled as a six-layered truncated prolate ellipsoid. The myocardium was defined as a slightly compressible, transversely isotropic, hyperelastic material. The reference LV was inflated statically by gradually increasing the pressure on its inner surface until an end-diastolic state was reached. The calculated dependence of normalized LV volume changes on the applied pressure was in good agreement with previous experimental results. Our calculated geometry was found to be comparable to previous measurements. The end-diastolic stresses were found to have complex variations, which cannot be determined by adopting an ad hoc stress-free, end-diastolic geometry. The calculated geometry and stress distribution are deemed to be suitable for use as initial states for cardiac cycle simulations.
Proposing a new acoustic emission parameter for bearing condition monitoring in rotating machines
Seyed Ali Niknam, Victor Songmene, Y.H. Joe Au
Bearings are important machine parts and their condition is often critical to success of an operation or process, hence there is a great need for periodic knowledge of their performance. According to reported research works in the past several years, it is believed that the extracted information from acoustic emission (AE) signals can be used for bearing condition monitoring. In this work, a novel parameter based on using the ratio of AE mean (μ) and AE standard deviation (σ), formulated as μ/σ is proposed to distinguish between lubricated and dry bearings. A heavy duty test rig was used in experimental work. Various levels of radial loads and rotational speed (ω) were applied to rotating shaft, which is connected to rolling element bearings. It was found that, except few cases, regardless of various levels of radial loads used, at higher levels of rotational speed, dry and lubricated bearings can be clearly distinguished when using proposed parameter.
Effects of impact location and angle of a flying cross bar on the protection of a long-rod penetrator
Yo-Han Yoo, Seung Hoon Paik, Jong-Bong Kim, Hyunho Shin
Based on a finite element analysis, the performance of a flying cross bar in protecting a long-rod penetrator increases as the impact location moves toward the head of the penetrator. It also increases as the impact angle approaches right angle. The optimal impact location along the span direction of the bar varies depending on the bar diameter.
Hybrid modified Elman NN controller design on permanent magnet synchronous motor driven electric scooter
Chih-Hong Lin, Chih-Peng Lin
The electric scooter driven by permanent magnet synchronous motor (PMSM) has nonlinear and timevarying characteristic. An accurate dynamic model is not easy to establish for electric scooter in the linear controller design. In order to conquer the above problem, a novel hybrid modified Elman neural network (NN) control scheme is proposed to control for electric scooter driven by PMSM. The proposed control system consists of a supervisor control, a modified Elman NN and a compensated control with adaptive law. Finally, the effectiveness of the proposed novel hybrid modified Elman NN control system is demonstrated in comparison with the PI controller from some experimental results.
An analysis of the damage tolerance of light aircraft landing gear
Pu-Woei Chen, Shu-Han Chang, Jyun-Yuan Siao
This study uses the finite element software, FRANC2D, and the life-time analysis software, AFGROW, to perform simulation analyses of the damage tolerance of the landing gear of light aviation vehicles. This study explores the effect that the initial crack positions and different materials have on the life cycle of landing gear under long-term loads. This study also compares the relationship between stress intensity factors and crack growth for four types of aluminum alloys, titanium alloy and alloy steel. The relationship between residual strength and life cycle, in the presence of existing cracks, is also investigated.
Transient thermo-stress field of brake shoe during mine hoist emergency braking
Zhen C. Zhu, Wan Ma, Yu X. Peng, Guo A. Chen, Bin B. Liu
In this paper, the finite element (FE) model of the three-dimensional (3-D) transient thermo-stress field of a brake shoe was established and then the software ANSYS 13.0 was used to get the numerical solutions; an experiment was carried out on the X-DM friction tester to verify the FE model. It was found that both the whole temperature and the equivalent stresses of the brake shoe increased and then decreased during mine hoist emergency braking; region of 1 to 3 mm below the friction surface was suffered to larger temperature gradients and stresses.
Effect of ambient temperature on the performance of a combined cycle power plant
Arvind Kumar Tiwari, Mohd. Muzaffarul Hasan, Mohd. Islam
The aim of the present paper is to examine the effect of ambient temperature on the performance of a combined cycle power plant. For this work, the combined cycle plant chosen is NTPC (National Thermal Power Corporation) Dadri, India where a gas unit of 817 MW is installed. The effect of ambient temperature on combined cycle efficiency, gas turbine cycle efficiency, exergy destruction in different components, exergy loss via exhaust and air fuel ratio at lower and higher turbine inlet temperature are reported. The results show that the net decrease in combined cycle efficiency is 0.04% and the variation in exergy destruction of different plant components is up to 0.35% for every °C rise in ambient temperature.
Hydraulic system fault diagnosis based on EMD and improved PSO-Elman ANN
Zengshou Dong, Xiaoyu Zhang, Jianchao Zeng
The element parameters of engineering machinery hydraulic system are detected, the fault eigenvector is extracted, and the information is applied to neural network fault diagnosis. Experience mode decomposition (EMD) is used to extract fault characteristic vectors in this paper, combined with the pressure, temperature and flow rate of dominant signal as neural network’s inputs. In addition, the paper improves the Elman neural network learning algorithm by the PSO algorithm. It can effectively increase network convergence rate and computing power. The particle swarm is used to optimize Elman neural network weights and the threshold value and then applied in the fault diagnosis system by training the network. The results show that the method increases the neural network convergence rate and reduces diagnoses error.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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