alireza toloei

The purpose of this article is to implement different methods of meta-heuristic algorithms to solve five engineering problems. these engineering problems have been optimized using five meta-heuristic algorithms of firefly, colonial competition, frog, ants and gray wolf with the aim of reducing the costs of engineering problems. in each of the algorithms, a dynamic adaptive factor is introduced to balance the convergence rate and absolute optimal search ability by adjusting the search speed during the search process. Investigations show that in each of the algorithms techniques are used to leave the local optimum, which makes the answers converge to the absolute optimum. To evaluate the quality and accuracy of the algorithms, the sensitivity test and the comparison of the convergence numbers for the results of the implementation of each algorithm on the data have been used. The results show that the firefly algorithm in spring tension problem, frog algorithm in three-bar truss problem, the colonial competition algorithm in the speed reducer and gear design problems, and the gray wolf algorithm in the pressure tank problem provided more accurate performance in finding the absolute optimum. . In fact, these algorithms make it easy to achieve the optimal solution by generating a random population, creating a neighborhood and choosing the best neighbor, provided that the constraints of the variables of the problem are satisfied. As a result, this paper shows that any meta-heuristic algorithm can perform better in a specific engineering problem, depending on the type of problem and environmental conditions.

Ensuring the high level of operational characteristics of aerospace structures is one of the most important problems of modern production. This is especially true in the space industry, as spacecraft are complex and expensive equipment that must be used for a long time. At present, satellites have a fifteen-year life cycle, the production of their components requires a great deal of effort in the choice of materials and manufacturing technology. The solution to this problem is not possible without the use of the latest composite materials and advanced technologies. In the present paper, the fiber rotational texture technology is proposed for the production of aerospace composite structures with high strength and temperature stability. An algorithm for obtaining the reinforcement angle and the type of fibers and adhesives, an algorithm for obtaining the technology parameters of the rotating tissue machine and an algorithm for correcting the reinforcement angle and the axial speed of the mold within the machine are proposed. A sample structure has been constructed and tested. Software and experimental studies have been performed to validate the algorithms.

In this article, the optimal design of a flying object is discussed with the help of designing the required speed. In this design method, the input information includes the type of fuel composition, payload mass, and maximum flight range, and the purpose of the design is to determine the initial mass and main dimensions of the aircraft. At the beginning of the design, the configuration of the bird is selected, and then with the determination of the fuel composition, the main characteristics of the fuel are determined as the main design inputs in the first step. By going through the design stages and by performing weight and geometric calculations, the initial mass of the flying object, the initial mass of the stages, the amount of fuel and oxidizer of the stages and the amount of thrust of the engines are determined. Then, to ensure the design method, similar flying objects in terms of fuel type, number of stages and also the final range have been used for validation. After performing the classical design, optimizing the mass function is considered, for optimization, the parameters λ_νi (relative initial thrust of the stages), P_ci (internal combustion pressure of the engines) and P_ei (exit pressure of the nozzle of the engines) with three GA methods (genetic evolutionary algorithm), ABC (bee colony evolutionary algorithm) and CA (cultural evolutionary algorithm) have been optimized and the results have been compared with each other. After analysis of the results, it is clear that the minimum mass (objective function) and the most optimal value is related to the cultural optimization method (CA), which reduces the initial mass by bringing the flying object to the final range.

The dynamics of many mobile devices in water are interactive and none linear. In particular, due to the assignment of incomplete and insufficient actuators, complex dynamics can be seen clearly in the Hovercraft. In this device, the dynamics changes greatly in each maneuver (different speeds). By turning the rudder for lateral movement, the longitudinal channel is affected and also by changing the longitudinal speed, the dynamics of the lateral channel is completely transformed. In this research, by identifying the dynamics of the system, a non-interference linear model is first extracted. For the obtained transfer function, with certain requirements, the controller is designed for the longitudinal, lateral velocity channel and angular velocity channel. As stated, this controller is designed for a specific situation and does not necessarily behave optimally for all maneuvers or uncertainties in the Hovercraft's system specifications. Inevitably, with the reinforcement learning method and specifically with the Monte-Carlo learning algorithm, the primary controller gains are adjusted offline for all possible situations (maneuvers and uncertainties). It should be mentioned that all the calculation load is done off-line, the result is applied to the primary control system as correction gains and is used on-line for the control process. The research results show that by adjusting the controller with the help of machine learning, at least %25 improvement in the tracking error is prosecuted.

The intended aircraft in this issue is an UAV type, capable of performing multiple missions. In this paper, after the linearization of the pitch channel, the transfer function for important points is extracted. After that, a robust classic compensator and an angular velocity damper are designed. According to the range of uncertainties, the compensator is adjusted by article bee colony algorithm. Also, the optimal value of the wing sweep back angle is obtained indirectly from the optimal value of the center of aerodynamic pressure. The optimization approach in this pepper is to make pitch channel robust to uncertainties. The results show that with the innovation in the design of the classic controller and its combination with Mont Carlo simulation and Optimization algorithm, the behavior of the pitch channel in the presence of uncertainties has been improved.

This article aims to control the group flight of unmanned helicopters. After presenting the dynamic equations using the Newton-Euler method, the dynamic inversion control has been applied to control the position and attitude of helicopters. generalized predictive control was also used to control the position and attitude of the helicopter. And the results of the simulation of these two controllers were compared, which showed the better performance of the predictive control. Therefore, in the design of the formation control, the independent control of the helicopters was done using the predictive control method. To control the formation, the method based on the leader-follower model has been used, An integral sliding mode controller is also used to control the dynamics of the formation error. The results of the simulation showed the success of the tracking by increasing the number of helicopters and the linear and spiral paths in the control commands.

In this paper, formation tracking control by maintaining a triangular shape for three quadrotors is discussed. Because of the nonlinear dynamic of the quadrotor and the presence of the external disturbance in the quadrotor dynamic model, a sliding mode controller was used for independent control of the quadrotor .To Formation Control of Quadrotors, a leader-follower decentralized formation control was applied. In such a way that the leader, follows a reference path and the followers use a formation controller to maintain a constant distance and an angle to the leader. First, the dynamic of the formation error is considered and then by using the integral slide mode controller, the formation error is reduced to zero. The simulation results obtained from the design of the sliding mode controller showed the occurrence of the Chatting phenomenon in the control commands, which was removed using the approximation of continuous functions. And the simulations obtained from this method showed the elimination of chattering in the control commands and the smooth tracking without oscillation of the desired path in the control commands. Also, the simulation results of formation control in the three missions with different paths, different formation geometry, and the number of different quadrotors indicate that the followers follow the leader and the success of formation control.

One of the best attitude sensors for space applications is the star sensor. This sensor determines the attitude using stars in the field of view. One of the main advantages of this sensor is attitude initialization using lost-in-space star identification algorithms. This paper presents a new lost-in-space star identification algorithm based on Hausdorff distance. Using Hausdorff distance, two different identification algorithms have been proposed, and their results have been compared. The first approach is designed based on using the pivot star, and the second approach uses the segmentation of the celestial sphere. The performance of these two approaches has been investigated using the simulation of 200 random directions of the star sensor in different magnitudes. The results show the approach of using the pivot star has better performance, and its identification rate is 93.5% at the magnitude of 6. Also, the identification time of the Hausdorff algorithm has been compared with the pyramid algorithm and some geometric algorithms. The results show that the Hausdorff identification algorithm has the lowest identification time which makes it suitable for real-time applications.

A numerical dynamic-aerodynamic interface for simulating the separation dynamics of constrained strap-on boosters jettisoned in the atmosphere is presented. Two commercial solvers: a 6DOF multi-body dynamic solver and a numerical time-dependent flow solver are integrated together with an interface code to constitute a package that presents real-time dynamic/aerodynamic coupled analysis. Dynamic unstructured mesh approach is employed using local remeshing methods in respect of bodies motion with a second-order upwind accurate 3D Euler solver. This interface can simulate multi body separation dynamics interaction with aerodynamic effects to complete separation mechanisms like springs, thrusters, joints and so on. The flow solver is validated by the Titan IV launch vehicle experimental data. The separation integration is used for a typical launch vehicle with two strap-on boosters using spring ejector mechanism and spherical constraint joints acting in the dense atmosphere. Hence, the aim of the presented interface is to facilitate the integration of complicated separation mechanisms with a full numerical CFD aerodynamic solver.

The main challenge of the star sensor as a real-time sensor is the execution time of attitude determination. Attitude determination using the star sensor includes five main steps: star catalog and identification algorithm selection, database construction, image processing, star identification and finally, attitude determination. Star identification consists of the implementation of the selected identification algorithm on the field of view stars and database searching. in the process of attitude determination using the star sensor, database searching is the most time-consuming part. This paper deals with three methods for database searching and surveys the search time for each of the presented algorithms also the consideration of using them as the database search methods for the star sensor. The methods are the ternary search technique, Fibonacci search technique, and interpolation search technique. The presented algorithms have not been used so far in the star sensor database searching. To survey the influence of the database dimensions on the identification time, each of the presented methods was studied using seven databases with different dimensions. The results show the superiority of the interpolation search method.

Considering uncertainty is an Inseparable part of industrial design and close to real issues. Ignoring these uncertainties in design can reduce system performance and even worse lead to failing the mission completely in some cases. In the present study, one of the design methods under uncertainty, namely the worst-case optimization for the design of a hydrogen peroxide monopropellant propulsion system, has been implemented. The proposed method in this study includes two types of epistemic and aleatory uncertainty. This method searches for the optimal point using the genetic algorithm by separating design parameters and variables for all three types of sparse points, single-interval, and multi-interval uncertainty representations. The designer is ineffective in choosing the type of distribution and the type of distribution is determined depending on the available data. In other words, even uncertainty in the type of distribution and its parameters has been considered. Also, the method of maximum likelihood-based is used to estimate the distribution parameters.

A numerical dynamic-aerodynamic interface code for the separation dynamics simulation of constra­in­ed strap-on boosters jettisoned in the atmosphere is presented. This code includes a main environme­nt which connects both dynamic and aerodynamic subsystems together at one time. The first part، consists of a 6-DOF multi body dynamic solver and the second part، contains a numeric­al aerodynamic flow solver، which is automatically used the dynamic mesh updating algorithm for adaption of the body motion in the discrete computa­tion­al field. The relationship between dynamic and aero­dyn­a­m­i­c solver is such that the resultant separation software، can simulates mult­­i body separation with complete mechanisms such as springs separation، Thrusters، joints، etc، in the presence of the aero­dyna­mic effects. The flow solver is validated by the Titan-IV launch vehicle experimental data. After all، this method is used in simulation of strap-on booster separation for a typical launch vehicle with use of spring separation system and constraint joints in presence of aerodynamic effects and without them. Hence the aim of presented interface is to facilitate integration of complicated separation mechanisms simulation with a full numerical CFD aerody­n­a­m­ic solver.

Falcaria vulgaris has different properties and it used as dietary and medicinal herb in the west of Iran. Previously, we showed that this plant has protective and repairing effect on gastric ulcer were demonstrated. The aim of present work was to investigate the effects of F. vulgaris extract on female rat's fertility. In this Exprimental study Virgin female NMRI rats (160-190 gr) were used in three experiments. In each experiment, animal divided into two subgroups (n=8): control which received Distilled Water (DW) (2cc/kg) and case which received herb extract (150mg/kg) interaperitonealy. In first experiment, animals received single dose of extract or DW. In second experiment، female rat received extract or DW in perimplantation period (day 1 to 5 of pregnancy) and in third experiment (day 5 to 7 of pergnancy). In both experiments implantation sites and neonates were counted in three experiments. Data were analyzed by T-Test test and p<0. 05 were considered significant. All three experiments showed significant differences between control and case groups in implantation sites and neonates number. This differences were more prominence in first and third experiment.