جستجوی مقالات مرتبط با کلیدواژه « قانون هدایت » در نشریات گروه « مکانیک »

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.

Submarine robots or autonomous underwater vehicles (AUVs) are one of the most important tools for identifying, monitoring and inspecting the marine environment and the oceans. In addition, it is used for applications such as tracking surface targets. In the process of tracking a target by an autonomous underwater vehicle, designing the most efficient guidance law is of particular importance. In order to evaluate the efficiency of the tracking process, various criteria such as ease of implementation, less need for target data and the probability of hitting the target must be considered. Among these factors and other effective factors in evaluating tracking performance, hit probability is the most important and telling variable. in complex situations, the most common way for calculating this parameter is the Monte Carlo method. This method is based on performing multiple simulations of the AUV and target motion for various uncertainties in the problem. The ratio of the number of times that the tracking process is successful provides an estimate of the hit probability. However, in order to achieve good accuracy, it is necessary to select a sufficiently large number of repetitions in the Monte Carlo method and therefore the computational cost of calculating the hit probability will be high. In this paper, first, using machine learning methods and in particular the gradient boosting method, a model for predicting the hit probability is presented with the appropriate accuracy. Then, using this model and by geometric calculations, the tracking parameters in the preset phase are determined in such a way that maximizes the hit probability. The efficiency of this method will be demonstrated through the simulation of different scenarios. In the end, by considering the randomness along the path, the AUV and target dynamic system is modeled as a stochastic process using the Ornstein-Olenbeck process. Then, the Monte Carlo simulation is described and similarly, previous works can be repeated.

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, a three-dimensional robust guidance law for a surface to air missile considering actuator saturation and first order dynamic for autopilot system has been designed in order to enhance the performance of defense systems. To attain this goal, first, modeling of the system in 3D spherical coordination using engagement basics has been derived and after that, appropriate cost function for collision of missile and target considering actuator constraints and in absence of target maneuver information has been formulated. Hamilton-Jacobi-Isaacs (HJI) differential equation inequality should be solved according to robust control literature for achieving guidance law which unfortunately does not have closed form solution in our case study problem. Therefore, to overcome this challenge, using adaptive dynamic programming theory for solving acquired HJI, algorithm for designing robust guidance law has been presented. Simplification solving of differential inequality and also guaranteeing robustness of the controller are the most important feature of the proposed algorithm. Numerous simulations for targets with different maneuvering capabilities and comparison of the proposed method with conventional augmented proportional navigation, show effectiveness of designed 3D robust guidance law.

In this paper, an LMI based guidance algorithm is mainly addressed to design a model predictive guidance law in presence of the input acceleration constraint. For achieving this purpose, firstly, the model predictive guidance problem is mathematically formulated in a two-dimensional problem. In the proposed algorithm, the future behavior of the guidance problem can be predicted by using a dynamical model. At each certain time, the commanded acclamation would be determined while a typical cost function is minimized. In this study, an acceleration command proportional to the line of sight (LOS) rate is considered as the predictive guidance policy with unknown variable gain. Then the model predictive guidance problem would be translated into another minimization problem subject to some linear matrix inequalities (LMI). Hence such an optimization problem can be numerically solved at each known time in the real-time applications. Then the gain of the proposed guidance algorithm can be automatically updated. The proposed method will be used in a typical two-dimensional guidance problem. The simulation results will show the effectiveness of the suggested method in comparing with the existing guidance algorithms.

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.

A new adaptive smooth second-order sliding mode control is proposed for uncertain nonlinear systems in this paper. The finite time stability is proved using a Lyapunov technic. The proposed controller consists of an adaptive term equal to the uncertainty in finite time. This algorithm is used to design terminal guidance law for homing interceptors to intercept maneuvering targets. The guidance law generates smooth acceleration commands and the control signal is able to stabilize relative lateral velocity in a desired time. Finally, the proposed guidance law is compared with the second-order sliding mode guidance law from carried out simulations.

Nonsingular terminal sliding mode (NTSM) guidance for intercepting the desired line of sight (LOS) angle in terminal phase is proposed in this paper. In order to satisfy the predefined LOS angle and to intercep into target, a nonsingular terminal sliding variable is introduced. In reaching phase, in the presence of uncertainties such as target maneuvers, robust NTSM guidance law is designed in order forzeroing the sliding variable in finite reaching time. Then, in sliding phase, due to introducing nonsingular terminal sliding variable, finite time stability of line of sight angle and line of sight angular rate is granteed without singularity in commanded acceleration as control signal Numerical simulations are presented to illustrate the potential of the proposed guidance law.

Usually vehicles are equipped with guidance algorithm based on line of sight (LOS) angle. In this way, some measurements like target acceleration, LOS rate, and closing velocity are provided for the guidance algorithm. The noise effect on the guidance loop would be neglected when the variance of the measurement noise is small. However, the stability property and/or performance of the guidance loop may be effected when the measurement noise is considerable. In this paper, a suitable guidance law is proposed in the presence of measurement noise. Then, a numerical example is provided. The effectiveness of the proposed method in the simulation results is shown in comparison with the previous results.

Usually guidance systems based on the Line of sight (LOS) angle are described by an ordinary differential equation. Guidance algorithms attempt to nullify the LOS rate while the closed loop stabilities guaranteed. Using the nonlinear system stability theory, the guidance law is designed such that the LOS angle would be a constant. Hence the guidance commands are applied to the vehicle actuators in term of some lateral accelerations. In practical implementation of the guidance law, the accelerations must be translated into the vehicle angles. Therefore proportional navigation (PN) guidance law firstly investigated in this paper. Then the PN guidance law is corrected such that the vehicle angle would be a constant while the closed loop stability is guaranteed and less computational effort is used. A numerical example is provided to show the efficiency of proposed procedures.

In this paper, a new procedure for designing the guidance law considering the control loop dynamics is proposed. The nonlinear guidance loop entailing a first order lag as the control loop dynamics is formulated. A new finite time and smooth backstepping sliding mode control scheme is used to guarantee the finite time convergence of relative lateral velocity. Also in the proposed algorithm the chattering is removed and a smooth control signal is produced. Moreover, the target maneuver is considered as an unmatched uncertainty. Then a robust guidance law is designed without requiring the precise measurement or estimation of target acceleration. Simulation results show that the proposed algorithm has better performance as compared to the proportional navigation, augmented PN and the other sliding mode guidance law.

In this paper، a new guidance law for yaw channel of homing interceptors is designed. Because of using the sliding mode theory، the nonlinear equations of motion are used and the target acceleration is considered as an uncertainty. Therefore، the precise measuring or estimating of target acceleration is not required and only the upper bound of target maneuvers is used. A sliding surface is defined using the angle rate of the interceptor target line of sight. For producing a smooth control signal and removing the chattering of the guidance commands، the discontinuous term of guidance law has been approximated with a continuous function. Adjusting the parameter of sliding term leads to decreasing the missile control effort، the time of flight and velocity loses. Simulation results in the presence of a real control system dynamics of a homing interceptor show the effectiveness and robustness of the designed guidance law against maneuvering target in comparison with the proportional navigation algorithm.

In this paper، a three-dimensional midcourse guidance law is presented for interception of moving targets using moving waypoints. The waypoints are selected such that the interceptor ascends initially at higher altitudes to fly its trajectory in the thin layers of atmosphere. The interceptor uses proportional navigation guidance with gravity compensation to fly towards the next waypoint. The waypoint positions are modified in case the target changes its course. Simulation results show that the proposed midcourse guidance has better performance for the long range in comparison with classical midcourse schemes.