Transactions of the Canadian Society for Mechanical Engineering
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Volume 38 (2014), Issue 3
Disturbance compensation techniques for controlling pneumatic actuator systems
Yu-Sheng Lu, Chang-Yong Syu, Chao-Shu Liu
In this paper, three disturbance compensation algorithms are experimentally evaluated considering the control problem of a rodless pneumatic cylinder. Despite its highly nonlinear dynamics, the pneumatic cylinder is modeled as a linear system including an unknown lumped disturbance. Three disturbance estimation algorithms are then employed to compensate for this lumped disturbance: the traditional linear disturbance observer (TDOB), the integral sliding-mode disturbance observer (I-SDOB) and the IMP-based SDOB (IMP-SDOB). Experimental results are presented to compare these three algorithms in terms of positioning accuracy.
Determination of the elements of production cycle time in serial production: The Serbian case
Dragan Cockalo, Sanja Stanisavljev, Dejan Dordevic, Milivoj Klarin, Aleksandar D. Brkic
A model for the stochastic determination of the elements of production cycle time is proposed and experimentally verified in this survey. The originality of the model as reflected in the idea of using a work sampling model to monitor the production cycle is one of the most significant indicators of production effectiveness and efficiency, instead of applying classical methods. It has been experimentally proved that for a corresponding representative set the elements of working time range according to normal distribution law and that, dynamically viewed, it is possible to use mean value calculations to establish control limits on three standard deviations for the individual elements of working time and thus to master the process. Based on our experimental investigations, it has been proved that in the practice of small and medium-sized enterprises with serial production it is possible to design and apply a very simple but accurate enough stochastic model to determine the elements of working cycle time and in this way optimize the duration of production cycle time.
Optimal design of hexapod walking robot leg structure based on energy consumption and workspace
Ya-guang Zhu, Bo Jin, Wei Li, Shi-tong Li
In order to achieve the optimal design of the hexapod walking robot leg structure, a combined index of energy consumption and workspace is raised. By deriving the energy consumption functions and analyzing the target workspace, a mathematical model of nonlinear programming with inequality constraints is established. The genetic algorithm coupled with inverse kinematics and trajectory planning in a gait period is utilized to solve the optimization problem. The analysis verifies that the requirements of turning and obstacle overcoming can be satisfied, and the total energy consumption can be reduced. The results show that the optimal parameters not only satisfy the requirement of the target workspace, but also achieve the minimum energy consumption and lower joint torques.
An experimental study on friction drilling of ST12 steel
Mehmet Tuncay Kaya, Alaattin Aktas, Bertan Beylergil, Hamza K. Akyildiz
The aim of this study is to investigate the effects of drilling parameters such as friction angle, friction contact area ratio (FCAR), feed rate and spindle speed on workpiece surface temperature, thrust force and torque in friction drilling of ST12 material. The tool material is tungsten carbide coated with TiN treatment. Experimental results reveal that the thrust force and torque increases gradually with increasing friction angle, feed rate and FCAR. On the other hand, the thrust force and torque decreases with increasing drilling speed. It is found that drilling speed has an important effect on the workpiece surface temperature. As the drilling speed increases, the workpiece surface temperature increases. Increasing or decreasing the friction angle and FCAR has no significant effect on the workpiece surface temperature.
Investigation on electromagnetic forces and experimental vibration characteristics of stator end windings in generator
Shuting Wan, Changgeng Zhan, Xiaofang Yao, Yanmin Deng, Guowei Zhou
This paper investigates the electromagnetic forces acting on the stator end windings, by using the stator end windings structure of a 600 MW large-capacity turbo-generator as the analysis object. Firstly, based on the method of images, the Biot–Savart Law and superposition theorem, the calculation model of the stator end windings is proposed. Then, the average electromagnetic forces acted on the end windings and the relationship between radial and tangential electromagnetic force densities are analyzed. The result shows that the tangential electromagnetic force should be treated as radial one and should not be ignored. Finally, the radial and tangential vibrations are measured to verify the theoretical analysis. The investigation results will be beneficial to the binding and fault diagnosis of stator end windings.
Relative importance of fuel properties on GDI fuel spray tip penetration
Simon Bruyère-Bergeron, Patrice Seers
Experiments were conducted to propose correlations of fuel spray tip penetration of a direct-injection injector fed with ethanol, butanol, isooctane, gasoline, and associated blends at different injection and ambient pressures. Correlations are proposed that enable predicting spray tip penetration as a function of fuel properties. The main findings are that alcohols offer less penetration than isooctane and gasoline, which have similar behaviour at 295 K. Ambient density played a major role in spray tip penetration, while the boiling temperature and enthalpy of vaporization were important fuel properties under warmer conditions.
An intermittent motion mechanism incorporating a Geneva wheel and a gear train
David B. Dooner, Antonio Palermo, Domenico Mundo
This paper presents a kinematic study of a mechanism incorporating a Geneva wheel and a gear train to achieve intermittent motion. The goal of this mechanism is to eliminate the acceleration jump at the beginning and end of the Geneva wheel motion. An epitrochoidal path replaces the circular path for the driving pin in a classical Geneva wheel drive. The epitrochoidal path is generated using a gear train and results in zero velocity, acceleration, and jerk at the beginning and end of the Geneva wheel motion. Presented is a comparison of the position, velocity, acceleration, and jerk between the classical Geneva wheel mechanism and the proposed mechanism. Subsequently, the motion of the Geneva wheel is modified by introducing a non-circular gear pair to adjust the timing of the epitrochoidal path. The motion of the non-circular gear pair is determined by reducing the extreme jerk of the Geneva wheel.
Transient heat conduction from spheroids
Rajai Alassar, Mohammed Abushosha, Mohammed El-Gebeily
We study the unsteady heat conduction from a spheroid (prolate or oblate) initially heated and then left to cool in an unbounded medium of constant temperature. We present two solutions of the problem. The first makes use of the spheroidal wave functions as basis. The second, which is numerical, is obtained by expanding the dimensionless temperature in terms of Legendre functions and then solving the resulting set of differential equations in the radial direction using an implicit finite difference scheme. The two solutions are further verified by comparing them to the limiting case of a sphere. We study the effect of the axis ratio on the time development of temperature inside the spheroid and the heat flux across the surface.
Influence of some geometrical parameters on the characteristics of prefilming twin-fluid atomization
Jiafeng Yao, Shinji Furusawa, Akimaro Kawahara, Michio Sadatomi
Geometries are considered to have a great influence on the spray characteristics of atomizers. In the present study, we studied a prefilming twin-fluid atomizer patented by Sadatomi and Kawahara (2012), in which liquid atomization is implemented by supplying compressed air alone into an internal mixing chamber, and water is automatically sucked by the negative pressure induced by an orifice. In the experiments, we studied spray characteristics influenced by the geometrical parameters, such as orifices in different opening area ratios and different shapes, porous rings with different porous diameters, and different atomizer sizes. Higher spray performance can be obtained by a small sized atomizer with a circular orifice in opening area ratio of 0.429 and a porous fiber ring with porosity of 25 μm. The present results provide a significant guidance for practical applications with different requirements of spray characteristics.
Experiments on hydrodynamic performance of Weis–Fogh-type water turbine
This study examines the hydrodynamic characteristics of the Weis–Fogh-type water turbine by measuring the forces in the U and V directions on the wing (NACA0010 airfoil). The distance from the trailing edge of the wing to the wing shaft (rp), water channel width (h), and maximum opening angle (α) are important design factors that were selected as the experimental parameters. The maximum average efficiency and average power coefficient of this water turbine for a single wing were 40% and 0.6, respectively, at α = 40°, h = 1.5C, and U/V = 2.0.
Full journal title: Transactions of the Canadian Society for Mechanical Engineering
Abreviated journal title: Trans. Can. Soc. Mech. Eng.
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