Transactions of the Canadian Society for Mechanical Engineering
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Volume 40 (2016), Issue 3
Design and testing of a new water supply device
Cong Cui, Xili Duan, Weiyan Ren, Yulu Hu
When water is supplied from pressurized pipelines, the high pressure often causes waste of water by splashing and unnecessarily high flow rates. In this research, an innovative new water supply device is designed to overcome this problem. In this device water is supplied in the form of overflow by automatically adjusting water pressure at the inlet. This paper presents the mechanical design of the new faucet and explains how it operates in sensor mode and bypass mode. Experimental results show that the new design achieves near-zero outflow pressure and can still provide rapid water supply when required.
A solution for nonlinear stability analysis of qft controllers designed for hydraulically actuated systems
Masoumeh Esfandiarim, Nariman Sepehri
Quantitative feedback theory (QFT) is a well-established technique to design robust and linear controllers. However, the important open problem of extending the small signal stability to nonlinear stability verification has remained an ongoing research in the design of QFT controllers. In this paper, we show that Takagi–Sugeno (T–S) fuzzy modeling approach and its stability theory provide a new opportunity to study the nonlinear stability of QFT controllers in fluid power systems. To validate the approach, two case studies are provided first. The first case study establishes the reliability of the approach by confirming the results for a hydraulic system of which nonlinear stability has already been proven. The second case study establishes that using the proposed approach, we can further study and extend the stability region of previously developed hydraulic controllers to include parametric uncertainty. Followed by the successful validation of the effectiveness of our approach through these two case studies, the stability of a QFT position controller, for which the nonlinear stability was never proven, is investigated.
Improving electro-hydraulic system performance by double-valve actuation
Yanhong Bai, Long Quan
Restricted by narrow bandwidth of the existing high-flow servo valves, dynamic performance of high-flow electro-hydraulic servo systems can only be enhanced to a certain extent by advanced control algorithms. This paper proposes a new hydraulic control circuit, in which two valves are arranged in parallel to control the actuator jointly. Frequency response of the equivalent valve is raised and thereby the performance of high-flow electro-hydraulic servo systems can be improved. A model of the proposed system is built and the principle of improving system dynamic performance using the new circuit is analyzed. Simulation results show that double-valve actuation schemes can quicken system response and increase system bandwidth regardless to if the two valves have the same or different behaviors.
Synchronization of dual homodromy rotors with eccentric masses in a nonlinear vibrating system
Xueliang Zhang, Jinlin Xu, Chunyu Zhao, Bangchun Wen
The motion equations of a nonlinear vibrating system are given firstly. The nonlinear stiffness of springs is equivalently linearized as a function of the response of system by the asymptotic method. The synchronization criterion of dual homodromy rotors with eccentric masses is derived theoretically, as well as the stability criterion. It is shown that the phase difference is close to zero during a sub-resonant state, otherwise it approaches π. The nonlinear characteristics of system are discussed numerically. By the comparisons among theory, numeric and simulation, the validity of the theory method used is examined.
Investigation of inlet effects on backward-facing step flow prediction
Mustafa Kemal Isman
The turbulent flow over backward-facing step (BFS) is numerically investigated by using FLUENT® code. Both uniform and non-uniform velocity profiles are used as inlet boundary condition. Five different Reynolds averaged Navier–Stokes (RANS) turbulence models are employed. The Std. k–ω model shows the best agreement with the experimental data among the models used under the conditions considered in this study. The results show that using a uniform velocity profile has a negative effect on predictions if the domain is not sufficiently extended upstream from the inlet. To eliminate this effect, the domain should be extended upstream by about 10Dh from the inlet. However, results show that this extension causes absorption effects of inlet parameters such as inlet turbulence intensity.
Characterization of ZrB2-SiC composites with an analytical study on material removal rate and tool wear rate during electrical discharge machining
S. Sivasankar, R. Jeyapaul
This research work concentrates on Electrical Discharge Machining (EDM) performance evaluation of ZrB2-SiC ceramic matrix composites with different tool materials at various machining parameters. Monolithic ZrB2 possesses lower relative density (98.72%) than composites. ZrB2 with 20 Vol.% of SiC possesses 99.74% of the relative density with improved hardness values. Bend strength and Young's modulus increase with SiC addition until it reaches 20 Vol% and then decreasing. EDM performance on tool materials of tungsten, niobium, tantalum, graphite and titanium at various levels of pulse on time and pulse off time are analyzed. Graphite produces the best Material removal rate (MRR) for all the workpieces. Tool wear rate decreases with melting point and thermal conductivity of the tool material.
Dry sliding wear behavior optimization of stir cast LM6/ZrO2 composites by response surface methodology analysis
G. Karthikeyan, G.R. Jinu
LM6 was reinforced with various percentages of ZrO2 particles by using stir casting method. The prepared samples were subjected to tensile and wear test at variable loads by using a pin-on-disc wear tester. The curve fitting technique was used to develop the respective linear, logarithmic, polynomial, power law equations. The wear worn surface and surface roughness of the specimen were studied. Response Surface Methodology (RSM) was used to minimize the number of experimental conditions and develop the mathematical model between the key process parameters namely weight percentage of ZrO2, load and sliding distance. Analysis of Variance technique was applied to check the validity of the developed model. The mathematical model developed for the specific wear rate was predicted at 99% confidence level and some useful conclusions were made.
Identification of major lean waste and its contributing factors using fuzzy analytical hierarchy process
P. Arunagiri, A. Gnanavelbabu
Lean refers to the reduction of non-value added activities in industries. It focuses on seven types of lean waste. The significant challenge is to identify and reduce the major lean waste. With this objective, a survey was conducted in an international exhibition in India using a questionnaire. The collected data were analyzed using Analytic Hierarchy Process (AHP) software template to check consistency. Finding consistent results obtained in AHP satisfactory, ranking was carried out to find the major lean waste using fuzzy AHP. After the identification of the major lean waste, the major contributing factors for the waste were ranked using the Binary Logistic Regression (BLR). These contributing factors were further investigated for the waste elimination in the automobile component manufacturing industries.
Optimal motion planning of a planar parallel manipulator with kinematically redundant degrees of freedom
Bahman Nouri Rahmat Abadi, Sajjad Taghvaei, Ramin Vatankhah
In this paper, an optimal motion planning algorithm and dynamic modeling of a planar kinematically redundant manipulator are considered. Kinematics of the manipulator is studied, Jacobian matrix is obtained and the dynamic equations are derived using D'Alembert's principle. Also, a novel actuation method is introduced and applied to the 3-PRPR planar redundant manipulator. In this approach, the velocity of actuators is determined in such a way to minimize the 2-norm of the velocity vector, subjected to the derived kinematic relations as constraints. Having the optimal motion planning, the motion is controlled via a feedback linearization controller. The motion of the manipulator is simulated and the effectiveness of the proposed actuation strategy and the designed controller is investigated.
Optimization of modified Watt's linkage for an approximately long straight path within limited dimensions
Jun Wu, Shaowei Fan, Minghe Jin, Hong Liu
This paper presents an optimal method of aiming for an approximately straight path of the Modified Watt's Linkage (MWL) within limited dimension. A modification to the Watt's linkage and the corresponding condition are introduced, followed by the kinematic synthesis. The path generation based on the modification considering constraints from practical application is provided. Genetic algorithm is utilized to perform the constrained optimization. The centrosymmetric property of the MWL is considered in the synthesis process. Ideal parameters of the mechanism are achieved to demonstrate the effectiveness of the proposed method.
A synthesis approach for reconfigurable redundant parallel-kinematic mechanisms
Hay Azulay, James K. Mills, Beno Benhabib
The design of a variety of novel Parallel Kinematic Mechanisms (PKMs) in the past three decades, and research into redundancy and reconfigurability have presented researchers with an opportunity to develop reconfigurable PKMs. In this paper, a novel synthesis approach for Reconfigurable Redundant PKMs (RRPKMs) is presented. The approach, motivated by the required reconfigurability, can help synthesize RRPKMs that reconfigure into lower mobility sub-configurations, assembly/working modes, and sub-PKMs, without the disassembly of the structure. Implementing the proposed approach for the design of a 5-dof machine tool, has led to the synthesis of a novel 3×RRPRS based RR-PKM that can reconfigure into four PKMs.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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