جستجوی مقالات مرتبط با کلیدواژه "شبیه سازی دینامیکی" در نشریات گروه "مکانیک"

In the present research, an autonomous wheeled seven-degree-of-freedom robot with an adaptation mechanism to a passive diameter pipe was designed with the help of Adams software, and after checking the correctness of its movement, by designing a fuzzy controller in the Simulink section of the software, the dynamic simulation of its movement in various geometric conditions such as straight and vertical pipes, elbows, pipes with reducers, deposits and corrosion were investigated. A fuzzy controller was designed to guide this robot inside the tube, and its control system was implemented using direct current motors for each of the robot's wheels. The ability of the fuzzy controller of the robot to follow the desired input speed and its response characteristics in the steady state were investigated, and the presented results showed that the fuzzy controller performs better in following high speeds and has a better transient response at these speeds. Using the optimal torque distribution system, the robot control system is improved and the output signal of the fuzzy controller can be sent to the robot wheels in a targeted way. Therefore, the application of this method caused a significant reduction in the power consumption of the robot and optimization of its energy consumption. This designed robot has a high potential for making an accurate sample, commercialization and responding to the current needs of the country's oil and gas industry due to its less expensive mechanism compared to similar ones.

In this research, the stability of Khorasan Petrochemical Feed Gas Compressor (C-2102) in surge avoidance control conditions with the aim of reducing energy consumption has been studied. Surge avoidance is one of the common methods to deal with the surge phenomenon, which prevents the onset of surge condition by preventing the flow drop in the suction side of compressor. In the present paper, by examining the operating conditions and performance curves of the compressor, three types of surge avoidance systems have been designed that maintain the compressor operating point at a safe distance to the surge line by measuring the operating speed, volume flow and suction pressure to the compressor. According to the results, in case the suction flow drops to 10% as a step function, the anti-surge control system prevents approaching the surge conditions, and in case the flow drop enters as a ramp function, the control system performs better and maintains the compressor operating point in the stable zone in the event of a 40% flow drop. According to the results, if the surge avoidance control system is activated, it will be possible to increase the suction pressure of the compressor, which will reduce the compressor power consumption by 20 percent.

In this paper, the dynamic modeling of a D-type boiler was performed during a step increase in loading. The D-type boilers are used in industry to produce process saturated steam. In these types of boilers, heat absorption occurs in two sections of the furnace and the convection section. The pipes of the convection section are indirectly exposed to heat, causes the flow direction to change from the upper drum to lower drum and vice versa. One of the special features of this boiler is that the drum circulation loop is natural and as a result, the hydraulic balance equations of the system must be considered. In the present modeling, the equations of water-side were considered in one-dimensional and the equations of flue gas-side were considered in three-dimensional space using the zonal method. The transient continuity and energy equations of the water-side form a system of nonlinear ordinary differential equations which were solved using the Runge–Kutta method. To solve the water and gas-side equations in two-way coupling method, a Fortran computer program has been developed. Investigation of the boiler operating parameters during start-up can help to improve the existing control system. The comparison of the present results with the test data of the desired boiler showed that maximum modelling errors are equal to 4.8, 1, and 6.8 percent for steam pressure, drum water temperature, and outlet steam of boiler during start-up, respectively. Also, the boiler response to a step increase in consumer steam demand is less than 20 seconds.
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This paper concerned with the examination of on-axis and off-axis dynamic responses of helicopters using a dynamic induced velocity model for a main rotor. The model consisted a canonical Legendry polynomial and a trigonometric function with a time dependent coefficients and arbitrary harmonics. The main reason for this, was the compatibility of the Legendry polynomial with the potential acceleration function presented by Laplace PDE for a main rotor at incompressible flow condition in elliptical coordinate system. The Laplace equation was previously solved through the separation of variables with discontinuity of pressure over the rotor disc and cylindrical skewed wake below the rotor. The novel of the present research is the inflow dynamics with finite state wake that was efficiently adopted with the dynamic equations of single main rotor helicopters (rigid fuselage, elastic main rotor, horizontal and vertical tail) in the time domain. Therefore, the discretization of the wake inflow was avoided by the definition of finite inflow states. Furthermore, the possibility of air load computations is achieved through the state formulation and quasi steady aerodynamic implementation. Moreover, the singularity problem associated with the traditional inflow dynamics was avoided through the current inflow state. The obtained results showed that using dynamic inflow model with 28-state and 4- harmonics significantly improves the off-axis dynamic responses of single main rotor helicopters. Comparison of the obtained results with the flight-test data and with the other dynamic inflow models showed that both the off-axis and on-axis response of helicopters experience a fairy good improvements.

A numerical-analytical modeling technique was presented for predicting instantaneous energy absorption with axial tidal turbines in unsteady water flow. The goal of present paper is introducing a fast and stable integral solution approach with unique solution. This technique employs steady-state CFD data to approximate transient performance of axial tidal turbine in unsteady external flows. This solution technique was designed for modeling axial tidal turbine with convergent-divergent duct in water flow with unsteady boundary conditions. The governing equations for fluid flow were derived in the form of integral equations. The equation of one-degree of freedom motion for rotor was solved with fourth-order Runge-Kutta method and variation of parameters approach. CFD data for rotor and duct of axial tidal turbine were inserted as boundary values in integral equations of fluid flow. Two transient analytical equations were employed for approximating rotor torque and back pressure coefficient of tidal turbine. The results of integral solution approach were compared with transient CFD data in ANSYS-Fluent software. Many numerical simulations were performed to determine duct dimensions for maximum power enhancement in an axial tidal turbine.

Pogo phenomenon is one of the low frequency instabilities in heavy liquid propellant launch vehicles at the system level of design. This instability produced from frequency interaction between structure and propulsion systems. In order to suppression or prevention of occurrence of this phenomenon in vehicles, designers use a device, to separate or remove the effects of frequency interaction of these systems. This element is famed to Pogo oscillation damper or Accumulator in penumahydraulic maps of liquid propellant engines. In this paper by using of dynamic modeling of engine elements (propellant tank, main feed line, accumulator, discharge line, pump assembly and thrust chamber) considering of connection between engine and structure in tank and pump assembly points, discussed about the effects of accumulator on the natural frequency of propulsion system and it’s considerations of location and performance for being in the main feed line of propulsion system is explained. Also sensitive analysis of accumulator's parameters on the natural frequency of propulsion system evaluated and results show that installing an accumulator in suction line and close to the pump assembly can decrease natural frequency of propulsion system, which can improve the stability of vehicle system. The influence of accumulator on the natural frequency becomes more significant due to increases of accumulator’s compliance and inertance. According to the matching the sensitive analysis’s results with experimental data in presence and absence of accumulator, it can be said that presentation of primary model for determination of position and size of accumulator is one the research achievements.

I‌n t‌h‌i‌s a‌r‌t‌i‌c‌l‌e, d‌e‌t‌a‌i‌l‌e‌d d‌e‌s‌i‌g‌n o‌f a n‌o‌v‌e‌l p‌o‌w‌e‌r l‌i‌n‌e i‌n‌s‌p‌e‌c‌t‌i‌o‌n r‌o‌b‌o‌t w‌a‌s s‌t‌u‌d‌i‌e‌d. T‌h‌i‌s r‌o‌b‌o‌t m‌a‌y b‌e u‌s‌e‌d t‌o m‌o‌v‌e o‌n g‌r‌o‌u‌n‌d c‌a‌b‌l‌e‌s f‌o‌r s‌p‌e‌c‌i‌a‌l p‌u‌r‌p‌o‌s‌e‌s s‌u‌c‌h a‌s t‌h‌e i‌n‌s‌p‌e‌c‌t‌i‌o‌n a‌n‌d f‌a‌u‌l‌t d‌e‌t‌e‌c‌t‌i‌o‌n o‌f e‌l‌e‌c‌t‌r‌i‌c p‌o‌w‌e‌r l‌i‌n‌e‌s. D‌e‌s‌i‌g‌n‌e‌d a‌c‌t‌i‌v‌e a‌n‌d p‌a‌s‌s‌i‌v‌e m‌e‌c‌h‌a‌n‌i‌s‌m‌s i‌n t‌h‌e p‌r‌o‌p‌o‌s‌e‌d r‌o‌b‌o‌t e‌n‌a‌b‌l‌e i‌t t‌o m‌o‌v‌e o‌v‌e‌r v‌a‌r‌i‌o‌u‌s o‌b‌s‌t‌a‌c‌l‌e‌s o‌n g‌r‌o‌u‌n‌d c‌a‌b‌l‌e‌s, s‌u‌c‌h a‌s c‌l‌a‌m‌p‌s, w‌a‌r‌n‌i‌n‌g b‌a‌l‌l‌s a‌n‌d m‌a‌s‌t t‌i‌p‌s. I‌n‌d‌e‌e‌d, t‌h‌i‌s r‌o‌b‌o‌t i‌s t‌h‌e f‌i‌r‌s‌t d‌e‌s‌i‌g‌n‌e‌d r‌o‌b‌o‌t w‌i‌t‌h t‌h‌e c‌a‌p‌a‌b‌i‌l‌i‌t‌y o‌f m‌o‌v‌i‌n‌g o‌v‌e‌r a‌l‌l g‌r‌o‌u‌n‌d c‌a‌b‌l‌e o‌b‌s‌t‌a‌c‌l‌e‌s. T‌h‌e a‌c‌t‌i‌v‌e m‌e‌c‌h‌a‌n‌i‌s‌m‌s c‌o‌n‌t‌a‌i‌n‌e‌d s‌e‌v‌e‌n r‌u‌b‌b‌e‌r-c‌o‌a‌t‌e‌d r‌o‌l‌l‌e‌r‌s (i.e. f‌o‌u‌r v‌e‌r‌t‌i‌c‌a‌l r‌o‌l‌l‌e‌r‌s a‌n‌d t‌h‌r‌e‌e h‌o‌r‌i‌z‌o‌n‌t‌a‌l r‌o‌l‌l‌e‌r‌s), a‌s w‌e‌l‌l a‌s t‌h‌r‌e‌e m‌e‌c‌h‌a‌n‌i‌s‌m‌s, i‌n o‌r‌d‌e‌r t‌o m‌a‌k‌e t‌h‌e h‌o‌r‌i‌z‌o‌n‌t‌a‌l r‌o‌l‌l‌e‌r‌s m‌o‌v‌e v‌e‌r‌t‌i‌c‌a‌l‌l‌y. T‌h‌e p‌a‌s‌s‌i‌v‌e m‌e‌c‌h‌a‌n‌i‌s‌m‌s i‌n‌c‌l‌u‌d‌e‌d a s‌e‌t o‌f s‌p‌r‌i‌n‌g-d‌a‌m‌p‌e‌r‌s i‌n‌s‌t‌a‌l‌l‌e‌d i‌n e‌a‌c‌h j‌o‌i‌n‌t o‌f t‌h‌e r‌o‌b‌o‌t a‌r‌m‌s. S‌i‌m‌u‌l‌a‌t‌i‌o‌n r‌e‌s‌u‌l‌t‌s i‌n A‌D‌A‌M‌S s‌o‌f‌t‌w‌a‌r‌e r‌e‌v‌e‌a‌l a d‌e‌s‌i‌r‌a‌b‌l‌e s‌t‌a‌b‌i‌l‌i‌t‌y o‌f p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e w‌h‌e‌n m‌o‌v‌i‌n‌g o‌n g‌r‌o‌u‌n‌d c‌a‌b‌l‌e‌s w‌i‌t‌h a m‌a‌x‌i‌m‌u‌m s‌l‌o‌p‌e o‌f 30-d‌e‌g‌r‌e‌e‌s. A‌l‌s‌o, t‌h‌e r‌o‌b‌o‌t s‌h‌o‌w‌e‌d a s‌u‌i‌t‌a‌b‌l‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e w‌h‌e‌n p‌a‌s‌s‌i‌n‌g o‌v‌e‌r t‌h‌e w‌a‌r‌n‌i‌n‌g b‌a‌l‌l‌s (w‌i‌t‌h a m‌a‌x‌i‌m‌u‌m d‌i‌a‌m‌e‌t‌e‌r o‌f 700m‌m), r‌e‌c‌t‌a‌n‌g‌u‌l‌a‌r m‌a‌s‌t t‌i‌p‌s (170*170 m‌m) a‌n‌d m‌a‌s‌t t‌i‌p‌s w‌i‌t‌h a 30-d‌e‌g‌r‌e‌e t‌w‌i‌s‌t i‌n t‌h‌e h‌o‌r‌i‌z‌o‌n‌t‌a‌l p‌l‌a‌n‌e. T‌h‌e f‌e‌a‌s‌i‌b‌i‌l‌i‌t‌y o‌f t‌h‌e‌s‌e m‌a‌n‌e‌u‌v‌e‌r‌s w‌a‌s p‌r‌o‌v‌e‌n w‌i‌t‌h a p‌r‌o‌t‌o‌t‌y‌p‌e i‌m‌p‌l‌e‌m‌e‌n‌t‌a‌t‌i‌o‌n a‌n‌d s‌u‌c‌c‌e‌s‌s‌f‌u‌l t‌e‌s‌t r‌e‌s‌u‌l‌t‌s. T‌h‌e r‌o‌b‌o‌t w‌a‌s a‌p‌p‌r‌o‌x‌i‌m‌a‌t‌e‌l‌y 60k‌g i‌n w‌e‌i‌g‌h‌t a‌n‌d m‌a‌y m‌o‌v‌e i‌n g‌r‌o‌u‌n‌d c‌a‌b‌l‌e‌s w‌i‌t‌h a m‌a‌x‌i‌m‌u‌m s‌p‌e‌e‌d o‌f 20m/m‌i‌n.

The first step in this paper is to simulate the dynamics of a projectile، carrying a gun-launched UAV، from launching to the time that the wings open. The changes that the UAV undergo such as coming out of the shell، opening the parachute and then the wings، all have been accounted in the simulation process. The second step in this study involves defining a multidisciplinary optimization problem. In the end، in order to maximize the range of the projectile، the optimization problem is analyzed. Through this analysis، considering stability constraints، optimal values for parameters such as the geometry of the projectile، diameter of the parachute، launch angle and separation altitude are achieved and regarding each one، some arguments are raised.

In this study, a six-degree-of-freedom dynamic model for the national engine on mounts is presented and is validated by experimental tests. Dynamic equations of the motion were derived using Lagrange’s and Newton-Euler equations. In addition, a thirteen-degree-of-freedom dynamic model for the engine and the vehicle was employed to consider dynamics of the vehicle body, tires and suspension systems in the vibration behaviour of the engine. Simulations were performed using data related to the national engine and the Samand vehicle. Experimental tests were performed on the Samand vehicle with the national engine using the chassis dynamometer. Finally, the validity of the presented mathematical model and the consideration of dynamics of the vehicle body, tires and suspension systems on the vibration behaviour of the engine were investigated.

In end milling operation, cutting forces induce vibration on tool, workpiece and clamping devices which affects surface integrity and quality of the product. In this process, to select the optimum end mill and machine tool, the prediction of exact cutting forces is of prime importance. In the present work, modeling and simulation of cutting forces in end milling operation are performed. Instantaneous chip geometry is predicted using a 3D simulation software, the effect of cutting depth and feed rate are calculated and cutting conditions are predicted before any machining operation.

The main reason for the slow response of stirling engine with respect to power requirement supply is that the system energy supply is provided from wall to the working gas inside the cylinder. On contrary to most control systems, in stirling engines, actuator has the highest lag time, since energy transfer from the wall is taking place very slowly. In this article, increasing the reaction speed of stirling engine with respect to the required power is considered. Also, besides the temperatare and pressure control inputs, a piston speed is also taken into accunt. As a result, control system is considered as a constant pressure and based on needed demand, the required parameters are calculated first from power-speed tables. At first, this speed is provided by an auxilary eletrical DC motor. Then, by comparing the output signal with the required output, the controlling commads are specified for pressure and gas temperature adjustments. In striling engine modeling, the isothermal assumption is eliminated in order to have a real behavior. The simulation of closed loop system and the designed controller show the effective increase in engine response speed. In this article, it is also shown that the control system is resistant, subjected to internal as wellas external disturabnes. These disturbances are in the form of changes in heat sink and system parameters. Since, torque is considered constant in a large speed interval, the engine efficiency will not be much affected.