Modares Mechanical Engineering
Year:2018 | Volume:18 | Issue:9 |Papers Count:28

In this study, a microgenerator is designed to supply the energy needed for electrical circuits of a MAV using piezoelectric materials. For this purpose, a composite airplane wing including all structural elements such as the ribs, spars and skins was designed in COMSOL multiphysics software. On the spar of this wing, a piezoelectric piece is modeled. The wing is modeled as a cantilever beam that its end is excited in an oscillatory manner with given frequencies and amplitudes. During the oscillation, the stress and strain of the wing elements are obtained using the finite element method and the amount of the generated voltage is calculated by coupling the piezoelectric governing equations with the strains. Next, an experimental model is created with the same characteristics of the numerical model and tested. The results of the numerical solution are compared with the results of the experimental tests for the verification. Afterwards, the effects of parameters such as the aspect ratio, the size of piezoelectric materials and the spar thickness on the generated voltage are studied. Finally, the results have been discussed.

Optimal Manned Space Launch System Conceptual Design with Modular Design and Sensitivity Analysis Approach The purpose of this article is to optimal manned space launch system conceptual design methodology with combination of modular design (by using clustering the existing motors to provide the thrust force) and sensitivity analysis (by varying the affected parameters to achieve the capability) approach. This methodology is implemented according to the human departure to space program and higher strategy document (country’ s aerospace development comprehensive document). To this end, in the methodology is utilized both of the statistical and parametric (the space launch system optimized main parameters) methodologies, is determined the optimum thrust level based on the three fundamental requirements (number of stages, number of engines in clustering and maximum axial acceleration). These fundamental requirements are affected on risk and manned space launch system axial acceleration. In the paper, the purpose of sensitivity analysis is to determine of value of effective of main design parameters on space launch system capabilities. The method for optimizing and design space searching is utilized from Genetic Algorithm (GA). Finally, the suggested methodology and mass – energy capabilities will be verified by comparing the results of two methodology (statistical and optimal) to achieve the specific mission.

Turbomachinery, specially gas turbines and axial compressors, play an important and vital role in energy producing and transmission industries. Thus, probable defects must be detected and measured in a timely manner, in order to prevent expensive costs of repair and maintenance. In this paper, a gas turbine blade-disc connection model, that is one of the most important and sensitive gas turbine parts, has been inspected using phased array ultrasonic non-destructive testing method. In manufactured mockup specimen, a crack with 4 and 8 millimeters length, has been created in two steps, followed by the length effect study on inspection results. Comparison of acquired signals in different angles for each crack length with acquired signals got from the healthy model in the same angles, has been employed for crack sizing purposes. The increase in the amplitude of crack reflected signals and the decrease in the amplitude of signals related to the wall behind the crack versus increase in the inspection angle, in ultrasonic phased array testing, has been utilized for extracting a novel feature for crack length estimation. Experimental results show that it is possible to evaluate the crack length in the complicated fir-tree geometry of the disc connection area to the blade, with the amount of error less than 10%, using the extracted feature.

In this study, the effect of delamination interface fiber angle orientation on the initiation and propagation fracture toughness of plain woven composites with stacking sequences of [012//012], [011/30//0/011] and [011/45//0/011] under mode I loading were investigated. These stacking sequences are chosen in order to eliminate the effect of the remote ply orientation on the delamination behavior of the double cantilever beam (DCB) specimens. Samples were manufactured by the wet hand lay-up method and fracture tests were conducted on specimens using the universal testing machine (SANTAM STM-150) according to ASTM standard. The experimental results showed that the interface ply orientation had a negligible effect on magnitudes of the initiation and propagation fracture toughness of plain woven composites due to delamination propagation in the resin-fiber interface of delamination interface. Experimental investigations of the fracture surface have shown the effect of different mechanisms on the delamination propagation, which crack propagation in the resin-fiber interface is one of the main mechanisms for increasing the fracture toughness in these specimens. In addition, the experimental evidence revealed that the fiber bridging was not the main mechanism of increasing fracture toughness during the delamination propagation, unlike the unidirectional DCB specimens.

Vibration waves with frequencies greater than 20 kHz, known as ultrasonic vibrations, are used in many manufacturing and engineering processes. This paper studies the occurrence of acoustic softening in steel specimens with three different microstructures. For this purpose, specimens with bainite and martensitic microstructures were created by Austempering and Quench heat treatments. The final dimensions of these specimens were obtained with Modal finite element analysis using ANSYS software so that the resonance frequency of the specimen is equal to the resonance frequency of transducer. Given that ultrasonic vibration induces a tension called vibrational stress to the crystal, this stress causes movement of dislocations and reduces the yield strength of specimens. In this paper 55 w / cm2 ultrasonic vibration, 18%, 12% and 8% yield strengths of specimens are reduced with ferrite-perlite, bainite and martensitic microstructure. Due to the absorption of vibrational energy by dislocation, the metal forming of these materials takes place with less energy. Also, in this paper, a numerical model for acoustic softening was investigated and it was found that there is a good correlation between numerical modeling and experimental e results.

The main purpose of this paper is to reveal the volume effect of ultrasonic vibrations on the plastic behavior of S355J2 steel specimens with different grain sizes and investigate the decrease in the Yield strength and ultimate strength of these steel specimens. For this study, samples of grain size of 10, 35 and 60 microns were created by performing various cycles of normalization and annealing heat treatments. An experimental setup was designed and developed for the tensile test with ultrasonic vibration. The tensile test was carried out at a room temperature and constant speed of 1 mm /min and it was found that by applying 390 watts of vibrations, the yield strength reduction of steel specimens with a grain size of 10, 35 and 60 microns was 8%, 18% and 27%, respectively. . The grain boundary length in fine-grain specimens is greater than the largest-grain specimens, therefore, the sound energy is distributed over the boundary. Therefore, the effect of applying ultrasonic vibrations on fine-grain specimens is less than that of largest grains and the yield strength and ultimate strength of fine-grain specimens showed a lower reduction.

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) has been widely used in recent decades due to operating at low temperature with high energy density. Water management is one of the main challenges for the development and commercialization of PEMFCs, which has a significant impact on their performance. The behavior of liquid water in the PEMFCs is very important. In this study a pore scale model is used to investigate liquid water transport in the gas diffusion layer (GDL) of PEMFCs. The GDL layer generated by randomly placing circular solid particles. The pseudo-potential lattice Boltzmann (LB) proposed by shan and chen is used to simulate two phase flow. The code was validated in three modes and is verified correctly then, the effect of three pore size particles, porosity coefficient and hydrophobicity of the GDL on the water transfer has been investigated. The results show that, over time, the amount of saturation in the GDL increases and ultimately reaches a constant value. In addition to by reducing the diameter of the particles, the amount of saturation and the number of breakthrough sites decreased, which increases the oxygen penetration. Also, the amount of local water saturation in the catalyst layer (CL) interface and the GDL tends toward one, indicating that oxygen molecules in these regions should be dissolved in water and then fed to the CL. In addition to, the amount of liquid water inside the porous layer decreases with increasing hydrophobicity.

Robotic arms are widely used for 2D desktop applications. In this paper, a new mechanism for a planar robotic arm is presented. In addition to having the benefits of both series of parallel robots, the proposed mechanism also eliminates the disadvantages of both categories. The arm made on the same side as the parallel arms has rigidity, strength and precision, and other positive features of the parallel arms, and on the other hand, like the serial arms, due to the lack of singular points inside the workspace, has a large, symmetrical and also be able to move continuously in the entire workspace. The kinematics relations for the arm are derived, and a controller based on AVR microcontroller & computer for the arm are introduced. The results indicate an improvement in arm performance and the removal of singular points from within the workspace.

Study of vibrational behavior and stability of fluid conveying pipes is important due to their large applications in industry. Several methods are used to solve the equation governing the vibration behavior of the fluid conveying pipes, e. g., the classical finite element method and the spectral finite element method. In the present study, the vibration behavior of the viscous fluid conveying pipe embedded in a visco-elastic foundation is investigated using the wavelet-based spectral finite element method. For this purpose, after deriving the equation governing the vibrations of the fluid conveying pipe, the vibration response is obtained using the mentioned method and the effects of the system parameters, such as the elastic foundation constant, fluid density, axial force, as well as the effect of the scale of the utilized scaling function on the system response, have been studied. The results indicate that by increasing the elastic foundation stiffness and/or, reducing the axial compressive force and the fluid density, the critical speed increases. Besides, the results show that increasing in scale of Daubchies scaling functions, increases the response accuracy. Also, to illustrate the advantages of the wavelet based spectral finite element method, for the case in which the analytical solution exists, the system time responses are compared with those obtained by the analytical method and the classical finite element method.

Pedaling is recognized as one of the most widely used therapies in rehabilitation. Which is influenced by various factors. Studying the effect of saddle position and saddle height (horizontal and vertical distance of saddle from pedal, respectively) changes in the pedaling feasible places range (saddle height range: 49-80% of leg length) on the leg joints range of motion and muscles contraction velocity are the purposes of this study. The pedaling conditions with ergometer are obtained in the model (crank arm length and pedaling rate are 17. 5 cm and 80 rpm, respectively). Results indicate that ankle, knee and hip joints range of motion are 11. 08-37. 54 (SD: 0. 03-1. 86), 69. 61-80. 58 (SD: 4. 02-9. 76) and 42. 89-46. 13 (SD: 0. 07-2. 89), respectively. The effect of saddle height changes on ankle>knee>hip and the effect of saddle position changes on knee>hip>ankle range of motion. By increasing the saddle height, ankle and knee joints range of motion increase significantly. The positive correlation between ankle-knee, ankle-hip and knee-hip joints, show the coordination and the cooperation of joints during cycling. The saddle place changes affect the contraction velocity of lower limb muscles. In particular, by changing the saddle place in the feasible places, the contraction velocity of ankle, knee and biarticular muscle groups change in a wide range.

In this research, control of vibration in multilayered cylindrical panel with piezoelectric patch, under dynamic load is investigated, for the first time. The finite element method is used to solve the dynamic equations of the structure, which is based on first-order shear deformation theory, and equivalent single layer models with different rotations for the substrate and the piezoelectric patch is developed. The governing equations are obtained by using the Hamilton’ s principle of virtual work, are discretized over the mid-plane, by using eight node shell element, leading into the matrix system of equations. The maximum controllability criterion is used for finding the optimal size and location of piezo-patch. According to the used control law, the applied voltage on the piezo-patch is proportional to the radial velocity component at the point, where the sensor is installed. In order to evaluate the performance of the formulation and finite element model, the natural frequencies obtained for the substrate laminated panel are compared with those in the literature. Then, having the dynamics of the optimal system, the frequency response for open and closed loop controls are studied. Finally, the effects of controller gain values and dimensions of panel and patch on the time response and damping rate of vibrations are illustrated.

In this paper, a viscous all-speed flow solver has been developed based on Roe upwind scheme in unstructured database. In the presented method, stiffness of the compressible governing equations in low-speed region reduces using the preconditioning form. In calculating the artificial viscosity of a Roe upwind scheme, multiple matrices multiplication are needed. Frink reduced these costly operations by simplification of the matrices multiplication to some flux components which are related to distinct eigenvalues. In this research similar to Frink work, the equations of artificial viscosity in preconditioning Roe upwind scheme obtained and presented in the flux components form. This is a generalized form that can be easily switched to the preconditioned or non-preconditioned form. This is useful in converting any original Roe upwind scheme to the preconditioning form and also has application in adjoint optimization method. Results of the computer code were compared with experimental data of single and two-element airfoils in both preconditioning and non-preconditioning form. The results show that the non-preconditioning compressible solver hardly converged in low-speed regions while the preconditioned form converged more rapidly.

Aerodynamic and optimal design of a blade of a horizontal axis wind turbine (HAWT) has been performed in order to extract maximum power output with considering the strength of the blade structure resulted from different loads and moments. A design procedure is developed based on the Blade Element Momentum (BEM) theory and suitable correction factors are implemented to include three-dimensionality effects on the turbine performance. The design process has been modified to achieve the maximum power by searching an optimal chord distribution along the blade. Based on the aerodynamic design, the blade loads have been extracted and the blade mechanical strength has been investigated by analyzing the thickness of the blade surface and the blade material. The developed numerical model can be considered as a suitable tool for aerodynamically and mechanically design of a turbine blade. The results for a 500 W turbine show that the turbine performance improves by 5% approximately, by modifying chord radial distribution. Yield stress analysis shows the effect of introduced chord distribution on the blade strength, in different blade thicknesses and different blade materials. In addition, optimum tip speed ratio for having favorable mechanical safety factor is derived. Three different airfoil are examined for this investigation and comparing their mechanical safety factor.

In the present paper, free axial vibration behavior of functionally graded nanorods is studied using the surface elasticity theory. For modelling of free axial vibration of nanorods, the Simple theory of rods is implemented. Besides using the Simple theory of rods, the surface elasticity theory is used for considering the surface energy parameters in the governing equations and boundary conditions. The surface energy parameters are the surface elasticity, the surface density, and the surface residual stress. The surface and bulk material properties of nanorod are considered to vary in the length direction according to the power law distribution. Then, the governing equation of motion and boundary conditions of nanorod are derived using the Hamilton’ s principle. Due to considering the surface energy parameters, the obtained governing equation of motion becomes non-homogeneous. But in none of the previous researches, for example investigation of free transverse vibration of nanobeams and free torsional vibration of nanorods in presence of the surface energy, the surface energy parameters do not cause the non-homogeneity of the governing equation or the boundary conditions. To extract the natural frequencies of the nanorod, firstly the non-homogeneous governing equation is converted to a homogeneous one using an appropriate change of variable, and then for clamped-clamped and clamped-free boundary conditions the governing equation is solved using Galerkin method. In order to have a comprehensive research, effects of various parameters like the length and radius of nanorod on axial frequencies of functionally graded nanorod is investigated.

Microwave-induced thermo-acoustic imaging (TAI) is an imaging technique with a great potential in detecting breast cancer at early stages. This technique combines the advantages of both microwave and ultrasound imaging. In this technique, image construction is based on the acoustic waves which are produced in the tissue due to irradiation of microwave pulses on it. Due to multi-physics nature of this phenomenon, the capability and feasibility of a numerical simulation method which can solve this problem consistently, investigated with performing a two dimensional simulation of TAI. In this simulation, a biological tissue including a tumor is considered in a rectangular duct (waveguide) under irradiation of pulsed 2. 45 GHz microwave source. The generated heat in the biological tissue due to electromagnetic waves irradiation and the corresponding pressure gradient in the tissue due to the temperature variations are evaluated. It is then studied for different power levels of microwave sources for identifying required power level for producing thermo-acoustic signals. Simulation results show a minuscule rise in temperature as a result of the absorption of pulsed microwave energy, for example, 0. 004743° C temperature increment in the center of the tumor, due to excitation pulse of 1000 W, 200 μ s. This small temperature variation in tumor, produce several kPa of pressure variations, 0. 02759 kPa pressure difference at the interface of tumor and breast tissue. This pressure variation will produce acoustic signals, which can be detected with array of transducers and used for construction of image.

In this study, the analysis of heat transfer in porous fin considering thermal radiation and natural convection is investigated. In order to model radiation, discrete ordinates method is used. Also, Darcy– Brinkman– Forchheimer model is applied for simulating porous media. A Least square method and numerical simulation (computational fluid dynamics) are applied to obtain the solution of governing equations. In addition, accuracy of LSM results is compared with the numerical simulation results. Moreover, the effects of homogeneous and non-homogeneous porosity along the porous media, Rayleigh number, Darcy number, porosity, surface emissivity, on temperature distribution along the length of porous fin and Nusselt number are investigated. Results show that the numerical simulation and LSM results are in good agreement with each other (With average error of 3. 39%). Also neglecting thermal radiation effect in heat transfer analysis of porous fin leads to 10-20% error in the Nusselt number value. Moreover, by applying nonlinear variable porosity along the porous media, the Nusselt number will increase up to 23% with respect to the homogeneous porosity. So in order to enhance heat transfer rate, porosity profile should be applied appropriately along the porous media.

Particle image velocimetry (PIV) is an optical flow measurement technique, which is capable of measuring instantaneous flow velocity. In this method, visualized flow patterns by small tracer particles, which follow the fluid flow and reflect an incident light, is recorded by a camera successively, and an analysis of particle movements in the recorded images results in the velocity of flow field. Correlation analysis is commonly used for the analysis of particle shift images, in which the images are divided into smaller windows called interrogation windows. The common displacement vector of particles in each interrogation window is determined by correlation analysis, which in turn results in the displacement vectors for the entire image. The accuracy of this method is dependent on the estimation of the location of the maximum value of correlation with subpixel accuracy. The objective of this research is the evaluation of function fit methods to estimate of the correlation peak location with subpixel accuracy. For this purpose, parabolic curve and second order surface fitting are investigated theoretically and experimentally. To achieve definite displacements, deformation of a solid part under uniform loading is investigated instead of fluid flow and the displacement of point patterns painted on the solid surface are analyzed. The results show that both function fit methods are capable of resolving subpixel movements with the accuracy of 0. 035 pixel or one micrometer in this research.

In this paper, considering the increasing need for high strength and thin pipes in the oil and gas industries, the effects of material strength and the initial thickness of the pipe and the friction between the pipe and the roller, on the distribution of the thickness and ovality of the cross-section of pipe in the process of sizing have been numerically and experimentally investigated. The simulation is performed using the commercial software MSC Marc Mentat. Results of the simulation show that by increasing strength material and reduction of thickness, the ovality of the cross-section of pipe decrease. It has been shown that with a 2. 77-fold increase in the yield strength of a pipe with thickness of 2. 8 mm, the ovality decreased by 27%. By decreasing the thickness of the St37 pipe from 2. 8 to 1. 8 mm, the ovality decreased to 2%. These changes increase with increasing yield strength, so that in the alform700 pipe with a thickness reduction of 2. 8 to 1. 8 mm, the ovality decreased to 45%. Furthermore, the friction condition has very little effect on the ovality of pipe. The validity of the finite element simulation is confirmed by comparison with experimental results.

The unique properties of metal foams, including light weight, energy absorption, low thermal conductivity and recyclability, have led researchers to explore new ways to achieve these materials with a good relationship between properties and production costs. Different production methods are divided into two groups of liquid state and powder method based on the initial state of the metal. The aim of this study is to provide a new method for the production of open cell aluminum foam with Sodium Chloride spacer. Two different types of aluminum alloy with different fluidity were used to produce foam with this method. Pressure tests were performed to show the compressive behavior of aluminum foams. The results showed that the behavior of foams produced by this method is the same as the outcomes of other papers. In different densities, the behavior of the soft foam was the same, but the stress was higher in the same displacement for higher densities. In the same density for the two different alloys, the axial strength of the A332 alloy was higher, but in contrast the soft foam is a good energy absorber. Young's modulus for two types of alloys with identical densities was 1. 45 GPa for the A332 alloy and 1. 11 GPa for the 1067 alloy. The amount of energy efficiency decreased by densifying the foam.

In this article, for the first time, the effect of non-uniformity of microbeam cross section and various boundary conditions on the nonlinear vibration of microbeam is investigated considering the size dependent behavior based on modified couple stress theory. Using the Hamilton’ s principle, the governing equation of Euler– Bernoulli microbeam with von Karman geometric nonlinearity based on the modified couple stress theory is derived. The nonlinear vibration governing equation is then solved using the Generalized Differential Quadrature method (GDQ) and direct iterative method to obtain the nonlinear natural frequencies. In this step, the Galerkin method is used to reduce the nonlinear PDE governing the vibration into a time-dependent ODE of Duffing-type. The time domain is then discretized via spectral differentiation matrix operators which are defined based on the derivatives of a periodic base function. Next, the nonlinear parametric equation is solved using pseudo arc-length method and the frequency– response curves of microbeam nonlinear forced vibration is obtained. Finally, nonlinear natural frequency and frequency response of microbeam with various non-uniformity of cross sections and boundary conditions are obtained. Present results show that, the nonlinear free and forced vibration of microbeam is size dependent. Moreover, this size dependency is more significant for non-uniform microbeam and is deferent for various boundary conditions. The result of present method for simple case including uniform section and simply supported boundary condition is validated with that of exact method and have good agreement.

In this paper, a systematic approach is considered to Design an optimal hypersonic Nozzle of a shock tunnel. After assigning the requirements and accomplishment of conceptual and preliminary design phases, a modern optimization strategy based on genetic algorithm and a CFD solver has been used to fine tune the nozzle convergent divergent contour. In this way, parameterization of the overall nozzle contour was done with a few control points and a Bezier curve. This arrangement showed a good flexibility to generate appropriate curves for nozzle shape. Design objectives were evaluated with a N-S viscous solver with a two equation turbulence model. Three objective functions were scalerized in a term with summation of weighted parameters: minimum total pressure loss, Mach number uniform distribution along test section and minimum axial flow deviation. A number of geometrical and physical constraints such as nozzle length, throat area, inlet and outlet diameters and inlet boundary conditions were also considered and finally, an optimized nozzle contour showed a significant improvement of about 3% in quality of the Mach 6 flow in the test section.

Investigating of boiling process is one of the attractive fields for researchers, because of many applications in industry such as heat exchangers and air condition systems. One of the important and effective factors in pool boiling heat transfer is the heating surface geometry. In present article, pool boiling of dionized water and Fe3O4/water nanofluid at atmospheric pressure have been analyzed on smooth and grooved copper surfaces, experimentally. The effect of rectangular, circular and triangular grooves with the same pitch on boiling heat transfer is the main aim of present article. The results have showed that the boiling heat transfer coefficient of dionized water in circular and rectangular grooved surfaces has enhanced 92% and 48. 9%, respectively, and has reduced 33. 1% in triangular grooved surface toward the smooth surface. Also, the boiling heat transfer coefficient of Fe3O4/water nanofluid in circular grooved surfaces has increased 40. 7% and has decreased 21. 8% and 88. 7% in rectangular and triangular grooved surfaces, respectively, toward the smooth surface. The corners existence in rectangular and triangular geometries causes thermal resistance increasing and heat transfer coefficient decreasing toward circular geometry. Also, the groove area, the mechanism of bubbles creation and nanoparticles deposition content on different surfaces are effective on the boiling heat transfer. For investigation of depth effect, the grooves depth was increased in different geometries. By adding depth, the boiling heat transfer coefficient of water and nanofluid has increased up to 43. 5% and 40. 6%, respectively, because of heat transfer surface and nucleation sites density augmentation.

Recently, a new approach called Transmissibility based Operational Modal Analysis (TOMA) has been presented in order to identify the dynamic characteristics of structural systems that determines the modal parameters of structures using the concept of transmissibility. In the TOMA approach, unlike OMA methods that use the assumption of white noise input, no limiting assumption is considered for the input excitations, and the modal parameters of structural systems are extracted based on the features of transmissibility matrix. The transmissibility methods, like other frequency domain methods, do not present very satisfactory results in identifying the damping values. Therefore, in the present paper, a new combined method called Fourier Spectral Transmissibility-Wavelet Transform (FST-WT) is proposed which, in addition to determining the natural frequencies and mode shapes of the system, also addresses the exact detection of damping values based on the features of wavelet transform. In this research, the capability of the FST-WT method in identifying and extracting the modal parameters of a 5-DOF system under free vibration is investigated using the responses obtained from the MATLAB Simulink model. For this purpose, the frequencies and mode shapes are respectively extracted from the inverse of the second singular value and the first left singular vector of transmissibility matrix, and the damping values are also determined using the single frequency signals (wavelet coefficients) obtained from wavelet transform based on the minimal Shannon entropy criterion. The comparison of the identification results shows a good agreement with the exact values.

Recently, a vast variety of wearable robots with various applications, including rehabilitation, have been produced, but a very challenging part of exoskeleton designing which is its motion control system still requires further investigation to be completed. Due to the nonlinearity in the dynamics of human-exoskeleton, uncertainty in parameters, unmodeled or simplified structures, and external disturbances (such as interaction of exerted human forces and movements), the use of robust control strategies is inevitable. Thus, in this research, a nonlinear disturbance rejection observer was used to estimate all of those as total disturbances. Then, a fractional order backstepping sliding mode (FOBSC) was utilized for enhanced tracking plus a Linear Quadratic Regulator (LQR) method to optimize the convergence to the equilibrium points. The advantage of using LQR is the optimum selection of the control input, and the FOBSC guarantees the robustness of the controller against uncertainties and disturbances. The combination of fractional order theory and control methods causes less chattering in the human-exoskeleton interactions. Moreover, particle swarm algorithm was used in order to select the coefficients of the cost function of LQR. In order to calculate the effect of the exoskeleton on human muscles and bones, the human parameters and knee motions, OpenSim was used. Matlab was used to implement the control strategy through OpenSim. The proposed method was then compared with the normal backstepping, fractional order system and LQR methods. The results show the superiority of this method compared to the classical methods.

In this paper, control position of a pneumatic actuator with the PWM solenoid on/off valves using two different pneumatic circuits performed. After deriving the governing dynamic equations, to investigate the circuit effect on system performance, mentioned two pneumatic circuits are introduced. Then in order to control the position of the pneumatic actuator, for both circuits, sliding mode and proportional-integral-derivative controllers are designed. In proceeding, optimum controller parameters are determined by genetic algorithm to achieve minimum control energy and position error. Finally, by performing simulations in Matlab Simulink, performance of designed controllers with optimal parameters is evaluated and compared in the presence of disturbance. According to the obtained results, by comparing the performance of two circuits, it is observed that the first pneumatic circuit with two solenoid valves can track the high-frequency sine reference input better and more precisely in the presence of a nonlinear sliding mode controller. The position tracking error in low-frequency sine reference input using a classic proportional-integral-derivative controller, for a single-valve pneumatic circuit is considerably less than that of a pneumatic circuit of two valves. This indicates the input-output quasi linear behavior of the pneumatic actuator in a single-valve circuit.