حسن محمد خانی

Usually, constrained lateral acceleration would have undesirable effects on the stability and performance of a guidance system. The composite nonlinear feedback (CNF) can be effectively used to improve the transient response of the closed-loop system in the presence of the constrained input. In this way, guidance law consists of an extra nonlinear term besides the conventional linear one. As a result, such a term adjusts the qualitative characteristics of the transient response. Meanwhile, the nonlinear term is a function of the rate of line-of-sight (LOS) angle which is not activated at origin and infinity. Thus it would be effective only in a specified region. In this paper, proportional navigation is employed for the linear term of the CNF-based guidance law. Therefore, a guidance algorithm is developed for tracking problems using the CNF idea. Applying the proposed guidance method, the closed-loop stability is analytically proved via the well-known Lyapunov stability theory. The suggested approach is simulated in a numerical example. Then the results are compared with an existing technique. As expected, guaranteeing closed-loop stability, in contrast to a similar method, the addressing scheme considerably improves the performance and transient response of the guidance system in the presence of lateral acceleration limitations.

In the guidance algorithms based on the line-of-sight (LOS) rate, the lateral acceleration commands are computed in such a way that the LOS rate is nullified. So, keeping constant the LOS angle, the condition in which the vehicle speed is greater than the target speed, the vehicle reaches the target position asymptotically. In this paper, a new guidance algorithm, based on the LOS angle, is presented for a typical guidance system. To this aim, considering the governed guidance equations and using the corresponding trigonometric relations, the proposed guidance law is transformed into an algebraic equation. Although the utilized guidance procedure is independent of the rate of LOS angle, the rate of LOS angle would equal zero instantly via applying the proposed method. Then, to illustrate the effectiveness of the idea, the derived mechanism is evaluated in a two-dimensional guidance problem. The advantages of the approach are shown in comparison with similar methods.

In the present article, the effects of high-power high-frequency acoustic noise on the dynamical response and fidelity of the sensing signal of the MEMS vibratory gyroscopes are investigated. At first, differential equations of motion the system with four degrees of freedom by considering the frame of the gyroscope are derived and rewritten in state-space form. In these equations, the interaction of the acoustic noise with the gyroscope is modeled as a mechanical force. Then, a Simulink model of the MEMS vibratory gyroscope dynamics is established and the effects of harmonic and random high-power high-frequency acoustic noises on the performance of gyroscope are studied. Influences of different parameters such as harmonic noise frequency, sound pressure level and quality factor of the gyroscope are explored. Numerical simulation results show the proximity of the noise frequency to the resonance of the gyroscope as well as pressure level deteriorate the sensing signal while the quality factor of the system rejects noise effects.

The process of computing the true values of the direction cosine matrix (DCM) is one of the important parameters for exact navigation of vehicles. In other words, determination of the directions of the INS vectors in terms of the directions of the reference system (alignment) is one of the important parameters of a navigation system. In order to improve the performance of such systems, this procedure is done according to the inertial measurement unit (IMU) and global positioning system (GPS) data, when the vehicle is in motion. Duo to the stochastic noise and uncertainties in inertial measurement sensors, a data fusion algorithm is used to integrate the outputs of the IMU and GPS sensors. In this paper a novel variant horizon predictive model estimation algorithm is proposed to construct an integrated INS/GPS inertial navigation system. The horizon of the proposed algorithm is calculated based on the vehicle maneuvers. Several vehicular tests have been carried out to assess the long-term performance and accuracy of the proposed navigation algorithm. The results indicate that the proposed algorithm significantly enhances the overall navigation accuracy of low-cost integrated INS/GPS inertial navigation system, in comparison to the conventional Kalman filter algorithm.

The conventional methods for designing autopilots deal conservatively with uncertainties such that the autopilot should be slowed down to the extent in which the system can maintain its desired performance in the presence of a certain uncertainty. However, there will be no guarantee of good performance in the presence of all uncertainties while the capabilities of the system will not be used properly. In the proposed method, using the extended state observer, the lumped uncertainties along with the system’s states will be estimated, and using feedback linearization approach, along with the nonlinear terms will be removed from the control loop. What remains is a simple linear system that is easier to control. In this method, uncertainties is treated without conservatism and consequently performance is improved in different conditions. Finally, for comparing the results of proposed method with linear autopilot a 1000 times Mont Carlo running with specific condition has been used and is shown that the proposed method is better than the conventional method in performance.

The inertial navigation system is a dead reckoning system, thus initial alignment for an inertial navigation system plays an important role in the accuracy of it. In this paper, a novel approach for initial alignment in an inertial navigation system with increased speed and accuracy is proposed. This method has two stages, which integrates the Kalman filter and a high order sliding mode observer. In the inertial navigation system, leveling misalignment angles reach the steady-state faster than the azimuth misalignment angle does, which means the azimuth alignment takes a considerable time for initial alignment. Therefore, in this paper at the first stage estimations of state variables of the system are obtained using the Kalman filter and whenever all variables (except azimuth alignment) reach steady-state, the second stage begins. In the second stage, the estimation which is obtained by the Kalman filter is used as the input to design an equivalent system with unknown inputs for inertial navigation system. A high-order sliding mode observer is then used to estimate the states of a system with an unknown input for estimating the azimuth alignment angle. This method not only increases the speed of estimation but also has comparable accuracy.

Accurate determination of the initial alignment for an inertial navigation system (INS), plays an important role in the accuracy of the navigation system, because inertial navigation is a blind navigation and is highly dependent on the accuracy of the initial estimation conditions. This paper presents a new method to increase accuracy and convergence speed of the initial alignment in an inertial navigation system. This new method includes two steps to estimate the initial alignment. These steps combine the Kalman method and a filter to estimate the states of a system with an uncertain input. In the first step, the estimations of horizontal misalignment angles are obtained by the Kalman filter. In the second step, the estimation which is produced by the Kalman filter, is used as an input to design an equivalent system for the INS. Finally, a filter is used to estimate the states of a system with an unknown input for the estimation of the azimuth alignment angle. Simulations show that this method not only increases the speed of estimation, but it also produces noticeable accuracy.

Control of impact time of missile to target has a great importance in applications such as Cooperative Attack of Multiple Missiles or Anti-Ship Missiles. This paper presents sliding mode control based guidance law against maneuvering targets with impact time constraints. Using nonlinear engagement dynamics, appropriate switching surface has been selected and sliding mode control has been designed using Lyapunov stability theorem. The sliding surface has been selected such that both the line of sight range and the error of the time remaining to target become zero to guarantee impacting the target at the desired time . By considering the non linear dynamic equations of maneuvering target , the proposed method can achieve the desired impact time against maneuvering target . In the proposed method , there is no need to consider small impact angle and non maneuvering target . Using the simulation model, the effectiveness of the proposed method in different scenarios (static and maneuvering) and taking into account different times for the impact time and its efficiency and its superiority as compared to other methods is shown.

In this paper, the problem of intercepting very high-speed non-maneuvering ballistic targets is addressed and a novel guidance law to enhance the probability of ‘hit to kill’ is designed. The most important challenges which arise in the interception of high-speed ballistic targets include high closing velocity resulting in the lack of time for the final reaction, low radar cross section and high noise power resulting in the lack of precise detection of target track until the last moments and considerable time constant in the order of final interception phase time. By ignoring some of these important challenges, existing guidance laws show great degradation in practice. In this paper we propose a twofold technique to overcome the challenges: a staggered missile team to share the target detection information and a feedforward static guidance input. The amplitude of static guidance is deduced through a regression model using a simulator software. Simulation of the proposed guidance law on a high precision model shows the efficiency of the method.

In this paper a new multi-scale method was presented to calculate the elastic modulus of graphene/polymer nano composites. Macro, micro and nano scales were considered within this hierarchical multi-scale method. In macro scale, a nanocomposite was modeled with a cubic representative volume element (RVE) which was constructed by several small cubic elements in micro scale. Each element in micro or nano scale, is made of aligned graphenes which were oriented in three dimensional space via a random algorithm. The stiffness tensor of each element was obtained by Mori-Tanaka micromechanical method and the elastic modulus of the RVE was calculated using a new analytical approach. In fact this method is a development of the laminated analogy, in to a three dimensional version which is in better accordance with the physics of real nanocomposites. It has been shown that the results of the present approach are in good agreement with several experimental works in the literature.

Due to stochastic noises, modeling uncertainties and nonlinearities in low-cost inertial measurement units (IMUs), the positioning error of Strap-down Inertial Navigation Systems (SINS) are increased exponentially. So, SINS is integrated with aiding navigation systems like a Global Navigation Satellite System (GNSS) by using an estimation algorithm to obtain an acceptable positioning accuracy. In urban area the GNSS signal may be obstructed because of tall trees and buildings. Therefore, in the paper a novel constrained adaptive integration algorithm is developed for integration the SINS/GNSS. In this algorithm, the velocities constraints in body frame in addition to altitude constraints based on a barometer data are firstly developed, and then a constrained estimation algorithm is designed based on the proposed constraints. In addition a fuzzy type 2 algorithm is used to calculate the estimator parameters based on vehicle maneuvers. The real vehicular tests are used for implantation and validation of the proposed algorithm. The experimental results indicate that, the proposed adaptive constrained estimation algorithm enhanced the estimation accuracy of the SINS steady states.

Gorgan Gulf is one of the rare ecosystems in the country that has ecological and economic features that have special values in comparison with other water resources of the country. monthly in-situ water sampling and analysis of water quality parameters include of Nitrate, Nitrite, Alkalinity, pH, Do, NH3, Salinity and Temperature, in 19 different points in Gorgan Gulf was performed. Monthly water sampling was performed during April, 2011 to March, 2012. Next, water quality data were interpolated by different interpolation techniques (Kriging, Invers distance, Polynomial regression, Local polynomial and Thin Plate Smooth Splines) using Surfer 9.0. These methods were compared using cross validation technique based on Root Mean Square Error (RMSE) evaluation index. The results showed that the Polynomial regression method is better than the other studied methods.  Hence, monthly maps of spatial distribution of water quality parameters were generated using Surfer 9.0 and MATLAB7.10 by Polynomial regression method and consequently, the average of Nitrate, Nitrite, Alkalinity, pH, Do, NH3, Salinity and Temperature in Gorgan Gulf was determined. According to the results of this study, the maximum values of temperature was 30 ° C, pH 8.88, dissolved oxygen 16.07, salinity 17, alkalinity 400, nitrogen 3.96, nitrite 0.19 and amonia 1.5 were measured. Comparison between average of these parameters in Gulf and the standards of the studied species for these parameters indicated that Gorgan Gulf is a suitable environment for aquaculture of Carp, Salmon, Trout, and Huso huso species.

A smooth second order sliding mode controller that guarantees a desired impact angle with a proper speed and impact time. This method is capable of intercepting high maneuvering targets. The desired impact angle is defined in terms of a time-varying desired line of sight angle for a maneuvering target. To solve the problem of the unknown target acceleration when intercepting maneuvering targets, an extended state observer (ESO) based guidance law is presented, and the target maneuver is compensated using the smooth sliding mode controller. Numerical simulations demonstrate the effectiveness of the proposed guidance law and show that this method has a better performance against high maneuvering targets in comparison with previous methods.

This paper is mainly concentrated on performance improvement and miss-distance reduction in a typical guidance system. These goals would be achieved by adding some attitude control motors (ACM) to the existing guidance algorithm. The ACM system usually contains some disposable thrusters, which are installed on lateral body of a vehicle. An extra force would be applied to the vehicle body through each thruster activation. Hence, it may cause a torque about the center of gravity. Then the induced rotation can be used to the attitude control. For increasing the agility and supplying the lateral acceleration in the end game phase, the lateral thrusters may be added to the guidance system. The yaw and pitch components of the line of sight (LOS) rates would be used to guide the vehicle with multiple actuators. For this purpose, a six degree of freedom vehicle model would be generated, considering the physical information, engineering assumptions, and adaptations images. The vehicle model would be firstly obtained by the DATCOM software. Then, the guidance system is numerically simulated in the MATLAB environment. The effectiveness of the proposed guidance method is shown compared with the existing algorithm.

Flight control system is a unit of the air defense and missile system that takes commands prescribed by the guideline law and operates due to the operators embedded in the system. Missile physical system includes nonlinear aerodynamic coefficients and other physical dependent variables, so accurate identification of them is difficult. This issue makes deference between real and mathematic model of missile equations of motion and causes designed linear controller performance degradation. In this paper, inverse dynamic approach is used for uncertainty identifying and mathematic modeling of missile defense system. Then, this model is used for optimizing and controlling the flight of a missile with nonlinear 6 DOF (Degrees of freedom) equations of motion. Thus, the designed controller is a nonlinear fuzzy-adaptive controller which has high adaption and robustness against the parametric changes during missile’s flight. Using the invers dynamic method for modeling motion equations of missile defense is the innovation of this research.

Nowadays, improving the aerodynamic performance of supersonic flying vehicles in order to reduce drag forces and increase in heat transfer coefficient is an interesting matter for researchers. Many of the supersonic vehicles use blunt nose to reduce heat generations, while these noses cause higher drag forces. Equipping the nose with spikes is a technique to reduce the drag of blunt noses. Spikes also increase their heat transfer rate. The accuracy and the validity of RANS based numerical simulations of turbulent flow over these bodies depend directly on the capabilities of the turbulence models used. This paper presents numerical simulation of supersonic flow over a blunt nose equipped with a spike, using four different turbulence models, namely: one-equation turbulence model of Spalart-Almaras and two-equation turbulence models of k-ε, k-ω and k-ω-SST. We wanted to find the appropriate turbulence model for this type of flows. Air flow Mach number and angle of attack were considered 6 and zero, respectively. The axi-symmetric, compressible and steady RANS equations are solved numerically. In spite of initial expectations, comparison of numerical results with experimental data showed that Spalart-Almamras has more consistency with experiment.

The Guidance commands are mostly generated by determining the line of sight (LOS) angle. Among the existed guidance laws, proportional navigation (PN) is the most widely used algorithm. In this way, the differentiation of LOS angle is needed. Then the LOS rate are usually found by numerical differentiation of the LOS angle. The LOS rate can be directly measured by an embedded internal seeker which it would be a differential free technique. Nowadays, in practical, guidance algorithms equipped with a seeker have been interested. Such a guidance loop includes some subsystems like vehicle dynamics, the type of flight path and also navigation sensors which each subsystems may have some parameters like aerodynamic coefficients. Therefore the guidance system performance would be affected by changing in these parameters. In this paper, in a typical vehicle equipped with a seeker, the guidance system efficiency are numerically investigated in terms of the aerodynamic coefficients change.

This study was carried out to investigate the phytoplankton composition in Gorgan Bay. Water samples were collected from 11 selected sites in Golestan bay, monthly from March to February. Thirty five genus were identified among which Bacillariophyta was the dominate group with 17 genus, while the Euglenophyta had the minimum. Abundance and biomass of phytoplankton showed spatial and temporal variations in the Bay. After Bacillariophyta, Cyanophyta was the most dominant group in spring, summer and autumn, while the Pyrrophyta was the most dominant in winter. Moreover, the highest number were counted for Nitzschia sp and Gyrosigma sp in spring, Gyrosigma sp, Euglena sp and Anabaenopsis sp in summer, Anabaenopsis sp and Prorcentrum sp in autumn, and Cheatoceros sp and Cyclotella sp in winter. Maximum abundance and biomass were calculated for site 8 (near Khozeini Channel) and the minimum were in sites 1 and 3 (central part of the bay) respectively. The average values of Margalef, Simpson and Shannon-Wiener indices were 0.3±0.27, 0.37±0.25 and 1.22±0.75 respectively, indicating low diversity in Gorgan Bay. The maximum Margalef (0.99), Shannon-Wiener (2.77) and the minimum Simpson (0.07) indices were calculated in February. Results of RDA showed that water temperature, water depth, transparency, phosphate, nitrate, pH, total alkalinity and dissolved oxygen had significant, high correlation with abundances of different phytoplankton genus.

Determining aerodynamic coefficients and control and stability derivatives play an important role in the development of flight vehicles. In this paper, roll damping coefficient of BASIC FINNER standard model is determined at different attack angles and with various Mach numbers using numerical Sliding Mesh method. Also, the impact of the effective parameters such as amplitude and frequency of oscillation, time step and number of iteration in each step in numerical solution are investigated to determine the roll damping coefficients. Geometry modeling and grid generation and the flow analysis are done by ANSYS CFX and ANSYS FLUENT software, respectively. In this simulation, Euler’s flow equations, compressible and unsteady flow, finite volume method and density based solver with explicit formulation and first-order accuracy for a numerical solution are used. To evaluate the results of a numerical study, a comparison is made between the experimental data and MD results, indicating that the results have a good accuracy.

Control systems under normal conditions can provide a desirable performance. But when faults occur in the system, maintaining the appropriate operating condition is a difficult and often necessary matter. In fact, lack of timely fault detection in sensitive systems will lead to damage significant amounts of resources and information. As a result, a growing tendency in the field of fault detection in both scientific and industrial communities has been created. However, if the system under consideration is nonlinear, fault detection cannot be possible with linear methods. In this case the main difficulty is in accurately modeling of process which effects on the accuracy of fault detection and troubleshooting. Fuzzy systems theory, is an effective tool to deal with the complicated and uncertain situations. This paper has considered the problem of fault detection based on the modeling for nonlinear systems using interval type-2 fuzzy system. Our proposed method for fault detection is to create a confidence bound using te estimation of upper and lower bounds for the system output which can be done using a type-2 fuzzy system. Here, a residual signal is produced which determines the presence or absence of fault in the system. In this method in case of deviating the output graph of the control system from the estimated upper and lower bounds, the occurrence of fault can be detected. Finally, in order to show the capabilities of proposed method, the method is applied on three-tank and electro-hydraulic nonlinear systems and the results are very satisfying.

One of the mainchallenges existing in the field of missile aerodynamics is how to reduce the aerodynamic drag of aerospace vehicles through different mechanisms. Thus far, many investigations have been performed to determine the performance and influence of various parameters on the effectiveness of these mechanisms. The challenge particularly is more pronounced in missiles with a blunt nose. The aim of this study is to reduce the aerodynamic drag of such missiles using hybrid employment of mounted spike at the stagnation point of the nose in addition to jet injection at different positions on the spike. To this aim, spike and jet injection configurations are extracted from the literature. Jet injection is considered in the sonic regime and perpendicular to the surface of spike. All analyses are performed using Fluent software along with Navier-Stokes equations for compressible and three-dimensional flow in both steady and unsteady states considering free stream at a Mach number of 1.89 and different angles of attach. Since the numerical simulation of these models requires high processing speed and memory, parallel processing system is employed. Additionally, structure grid and κ-ω -SST turbulence models are utilized. Results indicated that a significant drop in the drag is achieved using the hybrid utilization of jet injection and spike.

One of the important issues in aquaculture is the confidence interval between the aquaculture fields under the different pollution loading conditions. one of these conditions is the instantaneous pollution loading. It is necessary to determine a confidence interval between aquaculture fields that the instantaneous pollution in one field doesn’t influence another field. Gorgan Gulf is one of the most important water resources and supplier of fishing in Iran. The goal of this study is the determination of confidence interval between aquaculture fields. In this study، 2-D hydrodynamic and salinity modeling of Gorgan Gulf using MIKE21 is performed. Salinity concentration was measured in 19 different stations during 5 months of 1390 and the hydrodynamic and salinity models were calibrated and verified using these data. The optimum values for manning and dispersion coefficients were determined 0. 025 m/s and 50 m2/s، respectively. Then، 6 different conservative instantaneous pollution point sources were exerted in the gulf and the salinity model was implemented. The peak of pollutant concentration in various distances from point sources was determined and compared with the initial concentration of pollutant in the point sources. The results demonstrated that 99. 9% of pollutants is diluted until to 100m from point sources. Hence، the confidence interval of Gorgan Gulf was determined about 100m.

We collected 100 specimens of Persian sturgeon broodstocks propagated in Shahid Marjani Fish Culture Center to study internal parasites during March, April, and May 2005. The center is located in the southeast of the Caspian Sea. Three different parasite species were recovered from digestive tract (stomach and intestine) of the fish.Cucullanus sphaerocephalus, Skrjabinopsolus semiarmatus showed the highest incidence and highest mean intensity (with prevalence of 80% and 55% respectively) but Leptorhynchoides plagicephalus had the lower prevalene 2 %. The prevalence of S. semiarmatus and C. sphaerocephalus were higher in males than in females whereas the intensity of these parasites was higher in females than in males. Statistical analysis of data showed a significant relationship between the occurrence of S. semiarmatus and the sex of the fish. There was a significant relationship between the occurrence of C. sphaerocephalus and the length of the fish (P £0.05). Forty nine percent of the fish had less than 10 worms. It was also found that the internal parasites of A. persicus in the southeast of the Caspian Sea are the same as those found in the southwest but the diversity of parasites were fewer in the former.

Assessment of length frequency, length-weight relationship, distribution and biomass of the shrimp P. adspersus was done four times in the summer of the year 2002 in the Gorgan, Bay and south east of the Caspian Sea.
Results indicated that the mean carapace length (CL) was 13.55±1.79 mm, and minimum and maximum CL was 8.7 and 18.7mm respectively. We determined the length weight relationship as W=0.0035CL2.3123. In the south east region of the sampling area the mean carapacelength was 12.67±2.23mm and minimum and maximum CL was 5.2 and 17.5mm respectively. For this region, we found the length weight relationship as w=0.0035 CL 2.0956P. adspersus were found in all depths. Parallel with the air temperature increase, the shrimp density showed an increase at the depth of 2-10m. The estimated biomass of this species in the Gorgan Bay was 1999kg and in the south east region was 1160kg.