H. Mozaffari , A. Nahvi ,
Volume 19, Issue 1 (1-2019)
Abstract
Regarding the growing development of traffic perception systems, advanced driver assistance systems play a significant role in improving automotive safety. They should be able to guide intelligent vehicles through complicated driving scenarios. The complex nature of the driving process results in complicated control engineering methods. Modeling driver behavior based on psychological concepts would simplify the driving logic and human-machine interaction. In this research, psychological concepts and tire force limitations are formulated based on vehicle kinematics and kinetics as a function of speed and curvature. A multi-objective cost function is defined based on psychological concepts and tire force limits. The speed and the curvature, at which the cost function is minimal, are selected as the decided values. Saturated proportional controllers set the vehicle speed and path curvature on the decided values by adjusting the steering angle of the front wheels, accelerator pedal position, and brake force. The model performance is evaluated by a complicated driving scenario, which includes travelling in the same and opposite directions, presence of obstacles with different sizes and speeds, and high curvature paths. The model avoids face-to-face collisions with a time-to-collision close to 0.72 s. Also, it can avoid obstacles in tight spaces as narrow as 30 cm. Simulation results indicate that the proposed driver model performs safely at the presence of moving obstacles and tight spaces.
H. Pourhashem , A. Jamali, N. Narimanzade ,
Volume 19, Issue 2 (2-2019)
Abstract
Because of the widespread application in complex modeling based on experimental data, neuro-fuzzy networks have attracted the attention of researchers. In the neuro-fuzzy inference system, the objective is to reduce the system's prediction error relative to the actual data. The regulation of parameters of neuro-fuzzy network is very important and affects its performance. So, a new optimization algorithm based on Particle Swarm Optimization (PSO) and Differential Evolution (DE) has been proposed. In this algorithm, the coefficients of the operator speed are calculated dynamically, using fuzzy logic. These coefficients are set according to the generation number and variance of the particles. Proposed operator leads the particles to explore and exploit the search domain more precisely. Next, the performance of the proposed algorithm is checked by optimizing three benchmarks and comparing it with the results, which are obtained by conventional PSO and DE. The results show that the proposed algorithm obtained better solution in comparison with DE and PSO and proved its performance and efficiency. Finally, a neuro-fuzzy system has been employed to forecast the time series of Mackey-Glass. The parameters of this neuro-fuzzy network are optimized by the new algorithm and the PSO and DE method multi-objectively and the Pareto charts obtained by each method of optimization are compared with each other, indicating the better performance of the new algorithm.
O. Mohammadpour, R. Ahmadi,
Volume 19, Issue 2 (2-2019)
Abstract
In this paper, a robust discrete control law is presented, using a time delay control method for an omnidirectional mobile robot in the presence of system uncertainties. Although time delay control method has attracted the great attention of researchers due to its structure simplicity, the major part of these research have been performed by the assumption of continuous time delay control and infinitesimal time delay that is in contradict of physical nature of digital devices, as implementation tools of time delay controllers, which have finite and specific sample time. Also, the discretization of continuous-time systems has been usually done by Euler estimation method, which has sufficient accuracy for infinitesimal sample times. So, in this paper, after modeling the robot, considering the dynamics of robot motors, a new method for more accurate discretization of continuous nonlinear systems is presented and, then, a robust discrete control law is designed, using the backstepping technique at the voltage level of the robot motors. In the design of control law, a new adaptive sliding mode method is used to overcome the system uncertainties and stability of the closed-loop system is proved by error convergence to a small neighborhood of zero. The proposed controller is designed in the discrete domain without the necessity of being known the bound of system uncertainties and simulation results represent the desired performance of the controller in trajectory tracking.
M. Mokhtari, M. Taghizadeh, M. Mazare,
Volume 19, Issue 3 (3-2019)
Abstract
External disturbances and internal uncertainties with an unknown range, as well as the connection between the human body and robot, are major problems in control and stability of exoskeleton robots. In order to deal with disturbances and uncertainties with the known range of the system, the sliding mode controller is used as a robust approach. The chattering phenomenon is one of the drawbacks of sliding mode controller, which boundary layer is employed to reduce the effects of this phenomenon. In this case, not only the chattering phenomenon is not completely eliminated, but the robust characteristics of the controller are mitigated. In this paper, in order to cope with the disturbances and uncertainties with unknown range, and guard against chattering as a key ingredient of excessive energy consumption and convergence rate reduction, optimal adaptive high-order super twisting sliding mode control has been applied. The dynamic model of a lower limb exoskeleton robot is extracted using the Lagrange method in which four actuators on the hip and knee joints of the left and right legs are considered. To achieve optimal performance, controller parameters are determined using Harmony Search algorithm by minimizing an objective function consisting of ITAE and control signal rate. The proposed controller performance is compared with optimal adaptive supper twisting sliding mode and optimal sliding mode controllers which shows the superiority of the optimal adaptive high-order sliding mode controller rather than other designed controllers.
A. Mohammadi , E. Abbasi , M. Ghayour , M. Danesh,
Volume 19, Issue 4 (4-2019)
Abstract
In this research, the objective is using 4 quadrotors in a group to carry out a certain weighted load. The load is connected by cables to each quadrotor. The equations of motion of the quadrotors are considered completely and without simplification. Unlike other researches, to express the relationship between the load and the quadrotors, the ropes are considered as springs, so they are pulled out and retracted during the mission. Formation control design and path tracking by the group is done by using feedback linearization control. Control protocol design is presented in two structure, centralized, and decentralized. Unlike other papers, in decentralized structure, there is no information communication between the agents to reduce the communication costs. The mission of the group is defined as the quadrotors first pick off the load from the ground and, then, track the desired path to reach the target point. When the load reaches the target point, the quadrotors should put the load on the ground and, then, land themselves. Cutting the cable of one of the quadrotors is applied to the system as a fault and in addition to providing a method to detect its occurrence, the performance of the centralized controller is checked in this situation.
M. Mazare, M. Taghizadeh , S.m. Aghaeinezhad ,
Volume 19, Issue 4 (4-2019)
Abstract
Conspicuously, pitch angle control strategy has been applied to mitigate the influence of mechanical load and also output power control at above-rated wind speeds. In this paper, a wind turbine is modeled based on simplified two-mass model and an adaptive sliding mode controller (ASMC) is designed based on individual pitch control (IPC) strategy. To do this, the single-blade approach is used and the wind turbine was divided into aerodynamics and mechanical subsystems and governing equations of each subsystem were derived. By designing and applying the ASMC to two-mass model, system behavior is observed and simulated in terms of step and turbulent wind speed inputs. In addition, to verify the validity of the ASMC, the proposed controller is implemented in the FAST environment and the wind speed profiles are generated using TurbSim. In order to analyze the environmental effects on the dynamic behavior of the system, the controller performance is explored in presence of parametric uncertainties. It should be noted that rotor speed tracking error is evaluated and demonstrated through different criteria.
A. Soleymani , M. Nosratollahi , S.h. Sadati ,
Volume 19, Issue 4 (4-2019)
Abstract
The aim of this paper is designing a decision-making system (DMS) for temperature management of the satellite plates in the presence of actuators faults. The thermal stresses caused by solar radiation pressure perturbations is considered as a threat to the mission of satellites. In this paper, a new mechanism is used, which includes 4 fluidic momentum controller (FMC) actuators for sustaining the situation and performing various satellite missions in a pyramid. In this case, it is assumed that the satellite's plates are exposed to solar perturbations, and as a result, various faults have occurred for satellite actuators. To detect and isolate the defect of each actuator, recordable data from satellite and actuators are stored and feature extraction of these data is executed by linear differentiation analysis methods and analysis of the main components. To evaluate these methods, the confidence matrix is used, and the K-nearest neighborhood method is selected as the optimal method. To solve the temperature problem of the plates, the DMS is designed, so that if one of the plates reaches critical temperature, after examining the occurrence of a fault and adopting the appropriate strategy, the plate's rotation of the target plate is in the shadow. As a result, the temperature of the plate with the maximum temperature will reduce. The simulation results show that despite the perturbations and actuators’ faults, the designed DMS can manage the temperature of the plates somehow that does not enter the critical point.
V. Mohammad-Zadeh Eivaghi, M. Aliyari Shooredeli,
Volume 19, Issue 5 (5-2019)
Abstract
An alarm threshold plays an important role in an industrial fault detection system and directly contributes the False Alarm Rate (FAR) and Missed Alarm Rate (MAR). A crucial consideration for designing a threshold is estimating the Probability Density Function (PDF) of both normal and abnormal based on samples. The existence of measurement error in samples will be the contributors to an inaccurate estimation, following that, the alarm threshold will also be inaccurate. Therefore, grasping and recognizing measurement errors is highly important; in this paper, this problem will be investigated. For this purpose, firstly, a mathematical closed-form of statistical parameters will be estimated, and, then, based on error propagation rule, the computation error estimated parameters will be explored. It is assumed the high limit and low limit values of the measurement error are known or computable. Secondly, an approach is introduced to design a varying alarm threshold adapting to the current value of measurement based on . The proposed method is confirmed via a Monte Carlo simulation and it is finally applied to an industrial benchmark, Gas Turbine V94.2, experiencing fouling fault.
F. Sharifzadeh, A. Naghash,
Volume 19, Issue 6 (6-2019)
Abstract
Today, Ducted Fan micro aerial vehicle much attention in the field of business and research due to the duct and, thus, the ability to be safe in enclosed environments. In order to identify and practical help to control and implement the vehicle in various maneuvers, the experimental example of this VTOL MAV was built by of Amirkabir University of Technology. In this research, in the first step, the modeling of the ducted fan is considered. In this way, after obtaining the dynamic model of the fan, the parameters in this model are calculated, using empirical methods. In this regard, the aerodynamic coefficients of the control levels and the inertia of the fan can be mentioned. In the second step, the controller design of the ducted fan is discussed. -Fan MAV control is one of the important issues in designing this fan due to inherent instability. The study of vehicle that reported shows that nonlinear dynamic inversion is an appropriate choice among control methods due to its successful empirical implementation on . Thus, by choosing this method, the control system was designed to follow the desired command of the vehicle in the Simulink simulation environment. In this process, the position command is first applied to the fan and converted by the controller to the command of state control actuators, after which these commands by changing the angles of the control levels of the fan lead to the change in the angles of the fan’s side, the pitch, and and, thus, achieved a desired position. The results indicated that the desired command was correctly followed; also, the stability of the closed loop system was successfully accomplished by using dynamic inversion method for the Ducted Fan MAV.
S. Roshanravan, S. Shamaghdari,
Volume 19, Issue 6 (6-2019)
Abstract
This paper presents a new method to design stabilizing and tracking control laws for a class of nonlinear systems whose state space description is in the form of polynomial functions. This method employs the nonlinear model directly in the controller design process without the need for local about an operating point. The approach is based on the sum of squares (SOS) decomposition of multivariate polynomials which is transformed into a convex optimization problem. It is shown that the design problem can be formulated as a sum of squares optimization problem. This method can guarantee of the nonlinear system with less conservatism than based Also, a sum of squares technique is used to evaluate the stability of closed loop system state with respect to exogenous input. The nonlinear dynamic model of air vehicles can usually be expressed by polynomial nonlinear equations. Therefore, the proposed method can be applied to design an air vehicle autopilot. The hardware in the loop (HIL) simulation is an important test for evaluation of the aerospace control system before flight test. The HIL results using designed controller for a supersonic air vehicle are presented. The results from HIL is compared to the software simulation that the appropriate consistency of results shows the efficiency of the proposed method in the air vehicle autopilot control loop.
N. Rahimi, T. Binazadeh,
Volume 19, Issue 7 (7-2019)
Abstract
In this paper, distributed adaptive robust controller is investigated to solve the leader-follower consensus problem for a multi-agent system consisting of several single-link robot arms. In this approach, each arm is considered as an agent. The dynamical model of each arm contains known and unknown non-linear terms. Unknown terms may be due to parameter uncertainty or simplification of the model. Furthermore, external disturbances are considered in the dynamical equations of each agent. Moreover, the input signal amplitude for each agent should be limited, which is due to the upper bound of the saturation function of the input. In this paper, in order to eliminate the effect of uncertain terms, the adaptive robust approach is used in the design of control laws. In this regard, the upper bounds of uncertain terms are obtained through adaptive laws, which dramatically reduce conservatism. Furthermore, the distributed control laws are designed in such a way that all the agents reach consensus in spite of the uncertain terms and input saturation constraint. The basis of the approach proposed in this paper is based on adaptive sliding mode techniques. For this purpose, suitable sliding surfaces are proposed and distributed adaptive sliding mode controllers are designed. Finally, simulations are presented to confirm the results of theories.
H. Arefkhani, S.h. Sadati, M. Shahravi,
Volume 19, Issue 8 (8-2019)
Abstract
In this paper, a nonlinear inverse dynamic controller is designed for a magnetic actuated satellite. Since the stability of linear control laws in nonlinear dynamics is not guaranteed far from the equilibrium point, a global stabilizing nonlinear control law is necessary. In this method, by changing the system parameters, the nonlinear dynamics of the system is converted to linear dynamics and the input controller compensates the changes. The stability of the closed loop system was, then, investigated and proved by the Lyapunov method. Dynamic and kinematic equations of satellite are also developed in the presence of aerodynamic disturbance, gravity gradient, magnetic and radiation moments, and the linearization of the motion equations is done around the equilibrium point. In order to evaluate the performance of the dynamic inverse controller, the proportional-derivative linear control law and linear quadratic regulator optimal control law are designed and the results are compared. By modeling satellite orbit, the disturbance moments and the local magnetic field vector are calculated instantaneously according to the satellite's position in the orbit. Finally, the system response is presented by considering the saturation range of magnetic actuators. The results show a better performance of the nonlinear dynamic inversion controllers in both accuracy and convergence time.
S. Mahmoudkhani, A. Yazdani,
Volume 19, Issue 8 (8-2019)
Abstract
In the present study, the flutter and aeroelastic response of mistuned bladed disks to the engine order excitation are studied with the aim of determining the effects of disk structural properties and also establishing an efficient method of analysis. For modeling the solid-fluid interaction, the Whitehead’s incompressible, two dimensional cascade theory is used. The structure is also modeled, using a 4 degrees of freedom lumped mass-spring system, which accounts for the bending and torsional deformation of the blade and the disk. This model would enable us to study the effect of structural coupling of adjacent sections as well as the disk flexibility. The solution is based on expansion of the mistuned-blade response in terms of the traveling-wave modes of a tuned bladed disk. The adopted method would be appropriate for determining the aeroelastic response, since the aerodynamic loads are available only for each individual traveling-wave mode. The obtained solution is used to study the effects of disk flexibility on the aeroelastic instability, variations of natural frequencies with different numbers of nodal diameters, and the sensitivity of the vibration amplitude response to the mistuning. Furthermore, the effects of mistuning in blades torsional frequencies and the mistuning in engine order excitation is considered. Parametric studies show that for disks with a lower bending stiffness, the mistuning can significantly influence the aeroelastic behavior such that the for a certain amount of the natural frequency, the disk response could be increased more than 8 times due to the presence of mistuning.
M. Moghadasian, J. Roshanian,
Volume 19, Issue 11 (11-2019)
Abstract
In this research, an innovative approach has been proposed to the calculation of high order sensitivities and designing its guidance commands for an unmanned aerial vehicle landing strategy design. This method, which is called vectorised high order method, has been developed based on high order expansions method and its implementation using matrix-based mathematical calculations. In this research, a method is presented to design and extract the acceleration commands for landing maneuvers, by combining the vectorised high order expansions method and optimal control theory. Accordingly, the sensitivity variables for the given problem are calculated up to the 6th term and then the reference trajectory and acceleration command in the simulations are updated based on the initial deviations. In order to performance evaluation of the proposed method, 3 landing scenarios with the different initial deviations have been considered and the results of simulation of the proposed guidance law have been presented.
M.h. Shafiei, A. Azadian,
Volume 19, Issue 11 (11-2019)
Abstract
In this paper, a sliding mode predictive control method is proposed for function improvement of affine discrete-time nonlinear systems using integral terminal sliding mode method (ITSMC). The proposed method is based on the integration of terminal integral sliding mode method and model predictive controller which leads to using the advantages of both methods. Indeed, in the proposed method, integral and terminal characteristics of terminal integral sliding mode method are used to design the sliding surface in order to reduce the error (in reaching phase) and to converge to the origin (in sliding phase). Moreover, the chattering phenomenon which usually exists in sliding mode based methods will be decreased using the model predictive controller. The proposed control method has the capability to eliminate the effect of external disturbances and uncertainties. In this paper, it is shown that the model predictive method decreases the chattering phenomenon more than using the saturation function in the control law of the sliding mode method. In addition, using numerical and functional examples, the performance of the proposed method in improving the quality of the system response in the presence of external disturbances and uncertainties is illustrated.
M. Navabi, Sh. Hossini,
Volume 19, Issue 12 (12-2019)
Abstract
Maneuvering with the highest speed and low power has always been a challenge to design a satellite and spacecraft control system. In this paper, apart from the complexity of modeling actuators, different control methods were used to control the satellite attitude in the presence of uncertainties and disturbances in satellites, in order to obtain an explicit response to minimize the EULERINT criterion. The EULERINT criterion is the integral of the Euler angles between the body axes and the target around Euler's axis over time and somehow interprets the speed of the satellite maneuver in the three control axes. First, using the proportional-derivative control, the comparison of the EULERINT criterion in the application of different kinematic representations (Euler, quaternion vectors and direction cosine matrix equations) in linear and nonlinear models of the satellite was carried out. Then the comparison of the EULERINT criterion between the different methods was presented using the quaternion kinematic, which has the least amount of EULERINT, through changing the proportional-derivative controller to linear-quadratic regulator controllers, pole placement, adaptive, fuzzy, and adaptive-fuzzy. The comparison was conducted to achieve the best control method in terms of frequency response, the lowest EULERINT and the least control effort to control the attitude of the satellite in the presence of disturbance and uncertainty.
A. Kosari, S.i. Kassaei , A. Rostampour , S. Seyedzamani,
Volume 20, Issue 5 (5-2020)
Abstract
In this paper, a novel method for designing the flight paths of an aircraft is presented based on the concept of conformal mapping. Here, a low-altitude route-planning problem has been considered. In this problem, maintaining the control effort to reduce aircraft's altitude and increasing the speed with the limitations of Terrain Following (TF) and Terrain Avoidance (TA) issues, is the main strategy of this performance maneuver. In the proposed approach, attempts are made to convert the real space including terrains and obstacles, in which their data are provided using a digital elevation map, into a pseudo obstacle-free virtual space with no barriers and altitude constraints. In this regard, the concept of conformal mapping has been used as a facilitating mathematical tool for this problem-solving space transformation. The transformation of the problem-solving spaces under the mapping leads to solving the problem of dynamic reflection, the performance criterion, and the real altitude constraints in the virtual space. It is noteworthy that in designing a path in a newly converted space, the effect of barriers on the formation of flight routes is somehow included in the equations expressed in the virtual space. The results of multiple case studies and numerical optimizations performed for 2D geometrical terrains and obstacles show that the proposed approach is more consistent with the basic flight concepts as well as real-world applications.
M. Dalir, N. Bigdeli,
Volume 20, Issue 7 (6-2020)
Abstract
Today, the magnetic levitation system is widely used in various industries. This system is inherently unstable and nonlinear, which is presented by nonlinear equations. On the other hand, the existence of a time delay in these systems also causes system instability or even chaos, which creates additional problems in their control, thus requiring the design of robust and optimal control. In this paper, a robust adaptive intelligent controller based on the backstepping-sliding mode is proposed for the stability and proper tracking of the magnetic levitation system in the presence of time delay, uncertainty, and external disturbances. Due to changes in the equilibrium point, comparative control is used to update the system's momentary information and intelligent controller to estimate uncertainties and disturbances and non-linearity of the system. A robust controller is used to asymptomatic stabilize the Maglev system. The Lyapunov stability theory is used to analyze the stability of the magnetic levitation system with the proposed controller. In the end, in order to demonstrate the performance of the proposed controller, numerical simulations have been used in MATLAB software. The simulation results show that good tracking has been performed and the controller is very good against noise and disturbance.
Vafa Samadi, Mostafa Mostafaei, Ali Nejat Lorestani,
Volume 21, Issue 8 (8-2021)
Abstract
To minimize the cost of maintenance and repair of rotating industrial equipment, one of the methods used is condition monitoring by sound analysis. This study was performed to diagnose the fault of a single-phase electric motor through machine learning method aiming to monitor its situation by sound analysis. Test conditions included healthy state, bearing failure, shaft imbalance and shaft wear at two speeds of 500 and 1400 rpm. A microphone was installed on the electric motor to record data. After data acquisition, signal processing and statistical analysis, the best characteristics were selected by PCA method and then the data were clustered by machine learning method and K mean algorithm. These features used in the ANFIS modeling process were common features selected in both electromotor speed situations. After evaluating the models, the best model had the highest accuracy value of 96.82%. The average accuracy was 96.71% for overall fault classification. The results showed that the analysis of acoustic signals and modeling process can be used to diagnose electromotor defects by machine learning method. Based on the obtained results, condition monitoring of the electromotor through acoustic analysis reduces its stop and continues its work process in the industry. The repair costs of the electromotor are reduced by its proper condition monitoring.
Mohsen Rafat, Shahram Azadi, Ali Analooee, Sajjad Samiee, Hamidreza Rezaei,
Volume 21, Issue 8 (8-2021)
Abstract
With the increasing number of road accidents and driver assistance systems development, the automated vehicles importance has increased more than ever. As the issue of automated vehicles comes up, attending to their safety, and the impact of the other vehicles in traffic flow on their performance dramatically increased. One of the most important problems for automated vehicles is designing and controlling the trajectory regarding the surrounding vehicles in transient dynamic traffic conditions during complicated maneuvers. Although various studies have been performed in the field of lane change in dynamic traffic conditions and even in critical high speed, considering the transient dynamic conditions has been limited to the beginning of the maneuver and no solution has been provided for the surrounding vehicles’ immediate changes during the maneuver. The algorithm presented in this paper is able to design new safe optimized trajectories according to the sudden decisions of the surrounding vehicles during the lane change maneuver, also ensures collision avoidance in the whole maneuver via vehicle’s simultaneous longitudinal and lateral control. After evaluating the decision-making unit’s performance by real driving tests, the presented algorithm is simulated with different scenarios in complicated transient dynamic traffic conditions by using MATLAB software and its desired performance has been proven in the dynamic environment of IPG CarMaker, in the presence of surrounding vehicles.
