فهرست مطالب

  • Volume:12 Issue:2, 2019
  • تاریخ انتشار: 1398/04/23
  • تعداد عناوین: 11
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  • Hami Tourajizadeh, Samira Afshari* Pages 1-16
    In this paper a new model of the mobile robot is designed and modelled equipped by a manipulator which can perform an operational task. Also an adaptive force controller is designed and implemented on the robot to provide the capability of the operational task of the robot. Kinematic and kinetic modelling of the robot is developed and a new force control method is proposed for controlling the manipulator of the mobile robot by which the external disturbances caused by its operational performance can be controlled. Therefore, in this paper, a new mobile robot is designed which is suitable for operational tasks like firing and its related modelling is presented. Afterwards, an adaptive force controller is designed and implemented in order to neutralize the destructive effect of the mentioned backlash disturbance. By conducting some analytic and comparative simulation scenarios, the correctness of modelling and efficiency of the designed force controller is verified and it is shown that the proposed closed loop mobile manipulator can successfully accomplish a firing operation in a large workspace of a mobile robot with good accuracy.
    Keywords: Adaptive Force Control, Backlash Disturbances, Mobile Manipulator, Modelling of Firing Manipulator
  • Vahid Pourmostaghimi, Mohammad Zadshakoyan, Morteza Homayon Sadeghi Pages 17-26
    Demanding high dimensional accuracy of finished work pieces and reducing the scrap and production cost, call for devising reliable tool condition monitoring system in machining processes. In this paper, a tool wear monitoring system for tool state evaluation during hard turning of AISI D2 is proposed. The method is based on the use of wavelet packet transform for extracting features from vibration signals, followed by neural network for associating the root mean square values of extracted features with tool flank wear values of the cutting tool. From the result of performed experiments, coefficient of determination and root mean square error for the proposed tool wear monitoring system were found to be 99% and 0.0104 respectively. The experimental results show that wavelet packet transform of vibration signals obtained from the cutting tool has high accuracy in tool wear monitoring. Furthermore, the proposed neural network has the acceptable ability in generalizing the system characteristics by predicting values close to the actual measured ones even for the cutting conditions not encountered in the training stage.
    Keywords: Hard Turning, neural networks, Tool Wear Monitoring, Vibration Signals, Wavelet Packet Transform
  • Reham Mohammed Pages 27-37
    Controlling of the quadrotor has been noted for its trouble as the consequence of exceeds nonlinear system, strong coupled multivariable and external disturbances. Quadrotor position and attitude is controlled by several methodologies using feedback linearization, but when quadrotor works with unstructured inputs (e.g. wind disturbance), some limitations of this technique appear which influence flight work. Design control system with fast response, disturbance rejection, small error, and stability is the main objective of this work. So in this paper we can make use of new methods of control to design a controller of nonlinear robust with a reasonable performance to test the impact of wind disturbance in quadrotor control such as Fuzzy-PID controller and compared its results with the others four controllers which are PID tuned using GA, FOPID tuned using GA, ANN and ANFIS then discus which controller give the best results in the presence and absence of wind disturbance. The main objective of this paper is that performance of the designed control structure is computed by the fast response without overshoot and minim error of the position and attitude. Simulation results, shows that position and attitude control using FOPID has fast response and better steady state error and RMS error than Fuzzy-PID, ANFIS, ANN and PID tuned using GA without impact of wind disturbance but after impact of wind disturbance it was observed using Fuzzy-PID has fast response with minimum overshoot and better steady state error and RMS error than the other four controllers used in the paper and compared with most of literature reviews which didn't give the adequate results contrasted with the required position and attitude. The all controllers are tested by simulation under the same conditions using SIMULINK under MATLAB2015a.
    Keywords: Adaptive Neuro Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN), Fuzzy-PID, Fractional Order PID (FOPID), Genetic Algorithm (GA), Proportional Integral Derivative (PID) Controller, Quadrotor
  • Sushil Patil Pages 39-44
    The electrical grass trimmers are widely used for cutting grass along the highways, roadside & general agricultural work. Grass trimming involves the use of motorized cutter spinning at high speed, resulting in hand-arm vibration syndrome among the machine operators. The purpose of this work is to reduce the handle vibration of grass trimmer using tuned vibration absorber (TVA). The variable stiffness dual mass vibration absorber is designed using Dunkerleys Equation and fabricated for testing. The experimental modal analysis of absorber is conducted to find resonance frequencies of the absorber and to validate the results obtained from equations. The experimental tests are carried on grass trimmer with absorber attached at different location for two cutter head positions to find the absorber attachment location to reduce handle vibrations to minimum level. The results indicated that the vibration attenuation is affected by the location of absorber and cutter head position of grass trimmer.
    Keywords: Grass Trimmer, Handle Vibration, Modal Analysis, Vibration Absorber, Vibration Control
  • Mahdi Karami Khorramabadi Pages 45-51
    This paper deals with free vibration of epoxy/clay nanocomposite beams for functionally graded and uniformly distributed of Nanoclay with simply supported conditions at both ends. The specimens were prepared for uniformly distributed of Nanoclay with different Nanoparticles weight percent (pure, 3 wt%, 5 wt% and 7 wt%) and functionally graded distribution. To apply the model of theoretical predictions for the Young modulus, the genetic algorithm procedure was employed for functionally graded and uniformly distributed epoxy/clay nanocomposites and then were compared with the experimental tensile results. The formulation for Young modulus includes the effect of nanoparticles weight fractions and it is modified for functionally graded distribution to take into account the Young modulus as a function of the thickness coordinate. The displacement field of the beam is assumed based on the first order shear deformation beam theory. Applying the Hamilton principle, the governing equations are derived. The influence of nanoparticles on the free vibration frequencies of a beam is presented. To investigate the accuracy of the present analysis, a compression study is carried out with the experimental free vibration results. The results have shown that there is high accuracy for the genetic algorithm procedure for theoretical predictions of the Young modulus and the free vibration frequencies for uniform distribution are generally lower than the corresponding value of the functionally graded distribution.
    Keywords: First Order Shear Deformation Theory, Free Vibration, Functionally Graded Nanocomposite, Genetic Algorithm Theory
  • Mohammad Amin Saeedi Pages 53-61
    In this paper for handling improvement and lateral stability increment of a four-wheeled vehicle a new robust active control system is proposed. First, to establish an accurate model of the vehicle, a fourteen-degrees-of-freedom nonlinear dynamic model is developed. model of the vehicle, a fourteen-degrees-of-freedom nonlinear dynamic model is developed. Then, the nonlinear dynamic model is validated using CarSim software in a standard maneuver. Next, a new active steering control system was designed based on a simplified two-degrees-of-freedom dynamic mode to control the lateral motion of the vehicle. Two state variables, namely the vehicle’s yaw rate and the vehicle’s lateral velocity, are controlled using the control system. Also, the sliding mode control method is used to eliminate the error between the actual response and the desired response. Moreover, a complete stability analysis is presented based on the Lyapunov theory to guarantee closed-loop stability. Simulation results show that the controller is able to increase the vehicle’s maneuverability, especially during severe double lane change maneuver in which intense instability occurs. More investigations demonstrate that the proposed control system can considerably improve the vehicle’s path tracking under uncertainties.
    Keywords: Handling, Path Tracking, Sliding Mode Control, Uncertainty
  • Mahmood Adami, Ali Zamani Gharaghoushi, Behrooz Shahriari* Pages 63-73
    In this research for reducing the effect of losses and increasing the efficiency, the bowing in the rotor and stator blades is used. In one mode rotor blades are curved and in other one, stator blades are curved. The amount of rotor loss, due to changes in the thickness of the trailing edge and operating rotational speed, have been investigated. To confirm the accuracy of the results, a turbine stage whose experimental results are available is modeled and numerical results have been compared with experimental results that indicate acceptable compliance. The turbulence model k-w-SST is used to solve turbulent flow. The positive bowing, creates a pressure gradient from the two ends of the blade towards the center of the blade, which leads to the directing of the secondary flows toward the center of the blade. This reduces the losses in the two ends of the blade and increases the loss in the middle part of the blade. Increasing the thickness of the trailing edge, as well as increasing the turbine’s operating rotational speed, will increase the loss. The curved rotor increases the efficiency and mass flow and power by 0.4% and 0.5% and 0.8% respectively and the curved nozzle reduces the efficiency and power by 0.3% and 4.9% but increases the mass flow by 0.2%. It also increases the thickness of the trailing edge of the first rotor from 0.2mm to 0.9mm at 24000 rotational speed and increases the total loss by about 35%.
    Keywords: Aerodynamic Blade Changes, Axial Turbine, Blade Bowing, CFD
  • Abbas Pak Pages 75-81
    Ultrasonic transducers have found new applications such as ultrasonic assisted micromachining, micro forming, surface treatment, welding, etc. Apart from the transducer’s shape and size, the resonant frequencies and amplitude are seriously affected by materials properties used for transducer components. A further problem with the material is that their properties may vary from batch to batch and may also depend on the size of the raw stock. In this work using modal analysis, the material properties are calculated based on the frequency response method, which is more accurate than the nominal one. The finite element modelling was employed for both 2D and 3D FEM analysis to observe the behaviour of the cylindrical test rods and two sandwich-type piezoelectric transducers with the nominal frequency of 20 kHz and 30 kHz to find the validity of these properties. The obtained results showed that the modal analysis method could accurately determine the bar speed, Poisson's ratio and elastic modulus of the ultrasonic transducer components. The accuracy of this method increases by considering more vibration mode. Based on the results, obtained errors for FEM modelling of two ultrasonic transducers with the frequency of 20 kHz and 30 kHz are 0.15% and 0.33%, respectively.
    Keywords: FEM Modeling, Modal Analysis, Ultrasonic Transducer, Young’s Modulus
  • Mohammadmahdi Amiri Pages 83-90
    In this paper, a circumferential external surface flaw in a metallic round pipe under cyclic bending loading is considered. Because of very rapid changes in the geometrical parameters around the crack front region, the mesh generation of this region must be done with great care. The analysis of the fatigue crack growth is done in accordance with Paris law. The spread lane of the exterior defect is achieved from the graph of “α” vs. “relative crack depth”. The growth of fatigue crack is also analyzed (the comparative crack depth against loading runs diagram) with various initial crack “α” beneath periodic loading. Fatigue shape growth of primarily semi-elliptical peripheral surface flaws is shown. The weight of the Paris exponent (material constant) on fatigue crack propagation is presented as well. Furthermore, the “fatigue crack growth” progression of several specimens is evaluated experimentally by employing a manually-constructed experimental setup. Conclusively, the experimental results achieved by periodic bending loading tests are compared with the numerical results. Fatigue shape development of initially semi-elliptical external surface defects is illustrated. The effect of the Paris exponent (material constant) on fatigue crack propagation is shown as well. Moreover, the fatigue crack growth of several specimens is assessed experimentally using a manually-constructed experimental set up. Finally, the experimental results obtained by cyclic bending loading tests are compared.
    Keywords: Fatigue Crack Growth, K (Stress Intensity Factor), Semi-Elliptical Crack, Thin-Wall Pipes
  • Shayan Fathi, Arman Adamian, Mohamad Eftekhari Yazdi* Pages 91-101
    Neural networks can be used in various subjects, such as the discovery of relationships, identification, system modelling, optimization and nonlinear pattern recognition. One of the interesting applications of this algorithm is heat transfer estimation between contacting surfaces. In the current investigation, a comparison study is done for temperature transfer function estimation between contacting surfaces using Group Method of Data Handling (GMDH) neural networks and ANFIS (Adaptive Neuro Fuzzy Inference System) algorithm. Different algorithms are trained and tested by means of input–output data set taken from the experimental study and the inverse solution using the Conjugate Gradient Method (CGM) with the adjoint problem. Eventually, the optimal model has been chosen based on the common error criteria of root mean square error. According to the obtained results among different models, ANFIS with gaussmf membership function has the best algorithm for identification of TCC between two contacting surfaces with 0.1283 error. Also, the inverse method has the lowest error for thermal contact conductance estimation between fixed contacting surfaces with root mean square error of 0.211.
    Keywords: ANFIS, Electronic Chipset, neural networks, Thermal Contact Conductance (TCC)
  • Y. Tahmasebipour, Ali Vafaie, Mohammad Tahmasebipour* Pages 103-109
    Metal-based microelectromechanical systems are widely used in applications such as micro-energy harvesters, micro-heat exchangers and micro-electromagnetic that require high strength and flexibility. In the fabrication of such systems, micro wire electrical discharge machining (MicroWEDM) is majorly used. This paper studies the effect of the MicroWEDM process parameters on the dimensional deviation of machined MEMS structures including microcantilevers and micro-beams using the Taguchi method. Using optimal levels of the parameters including pulse duration (0.8 µs), cutting speed (8.4 mm/min), voltage (17 V) and wire tension (0.5 kg), the dimensional deviation is reduced about 8.65 times compared with the average of experiments results. The order of effect importance of the process parameters on the dimensional deviation of microstructures obtained by the ANOVA analysis of S/N ratios is as follows: pulse duration, wire tension, process voltage and cutting speed. Dimensional deviation of the micro-features was reduced to 1 μm using the optimal levels of the process parameters.
    Keywords: MEMS, Microbeam, Microcantilever, Micromachining, Micro Wire Electrical Discharge Machining, Micro-WEDM