Journal of Aerospace Mechanics
Year:2019 | Volume:15 | Issue:1 (55) |Papers Count:12

In this paper, design and implementation of model predictive controller for turbofan engine fuel control are proposed. The satisfaction of operational and structural limits of the engine is a controller design challenge. The control system must ensure that the engine operates without any limit violation at all times, i. e. without over-speed of the shaft, compressor stall, combustion chamber blow out and turbine over-temperature. In this regard, a controller is required which can take into account these constraints while obtaining an optimal control input. Therefore, the model predictive control for turbofan engine fuel control using a linear model of the engine at one operating point is designed. The simulation results show that while model predictive control generate optimal control signal, all the constraints are perfectly satisfied. After assuring the valid performance of the controller in computer simulations, the fuel control algorithm is implemented on a hardware framework. For this purpose, the controller algorithm is implemented on a microcontroller and hardware-in-the-loop test is performed. The results of the hardware-in-the-loop simulation indicate the correct implementation of the model predictive controller on the hardware framework.

Recent progress in the aerial robots’ technology facilitates these platforms to incorporate in complex missions such as delivering, search and rescue, and surveillance over urban environments. An accurate control and guidance system is necessary to broaden the mission domain, increase the reliability of robots, and enhance compliance with safety and communicative constraints. In this research, a hybrid flight controller besides a Guidance system is proposed for a quadrotor aerial robot which contains separate guidance and control modules. Realization and implementation capacity of the generated control law is particularly considered in the design of control system. Furthermore, in the design of the control system, dynamical limitations of quadrotor specially underactuated-ness are considered in order to enable the quadrotor to track a three-dimensional trajectory. Guidance subsystem is designed based on a behavioral algorithm, which produces a trajectory based on leader-follower concept for both linear and nonlinear dynamic inversion controllers. The simulation results exhibit the potency of the presented method for further researches on obstacle avoidance and formation flights.

One of the major challenges in the use of predictive control systems, particularly in the fast system is computational burden. To accelerate the process and reduce the amount of computation and optimization of functions, we use the Laguerre functions. The purpose of this paper is to provide a linear predictive control method using Laguerre functions with constraints on signal and the rate control signal for a helicopter flight control system design in the status of hover maneuver. By tuning parameters of predictive control in nonlinear model, the performance of the proposed method evaluate by two index entries, maneuverability and coupling effect based on standards for design a helicopter flight control system. Multiplicative uncertainty in state-space model has been described due to uncertainty on system modeling to study the robustness of the proposed method. The simulation results of this method have been compared with the results of generalized predictive control method. Simulation results show that in addition of public benefits in generalized predictive control, Laguerre predictive control has the advantage of reducing the time and burden of computation and it is clear to see that the control law we have obtained for the hovering flight condition achieve the top level performance in two categories under examination.

Electro hydraulic control systems are important in their ability to handle large torque loads and quick response. Velocity, position and torque control are the most important controlling methods for the systems. The control systems suggested before including uncertainty parameters such as: internal friction, external noises, and non-linearity in the model behavior. Parallel distributed compensator method based on Takagi-Sugeno and fuzzy controller are used in this paper by feedback error learning's idea. In addition velocity control and identification of the model is carried out by applying regulation scheme. Results indicate that the controller presents better performance and response to the other controllers Also stability of controller is validated by linear matrix inequality method.

The cutting tool wear degrades the quality, reliability and productivity of the product in the manufacturing process. Accordingly, an on-line monitoring of the cutting tool wear level is essential to prevent any deterioration. Unfortunately, there is no direct method to measure the cutting tool wear on-line. Consequently, an indirect method can be adopted where wear will be estimated from the measurement of one or more physical parameters appearing during the machining process such as vibrations, electrical current, cutting force, etc. In this paper, two techniques namely Adaptive Neuro-Fuzzy Inference System (ANFIS) and Multi-Layer Perceptron (MLP) have been used for prediction of tool wear in face milling. For this purpose, a series of experiment is carried out on a milling machine. It is observed that there was an increase in the current amplitude with increasing the tool wear. Besides, the effects of tool wear, feed, and depth of cut on the current are analyzed. Comparison of the tool wear detection techniques shows 92% of correct tool wear detection for ANFIS and 84% for MLP. As a result, ANFIS can be proposed as proper technique for intelligent fault detection of the tool wear and breakage due to its high efficiency in diagnosing wear and tool breakage.

Because of the high cost of mechanical and optical gyroscopes, in recent years the low cost measurement systems based on Micro Electro Mechanical sensor (MEMS) are widely used. These systems often are integrated with radio navigation to achieve the required accuracy. MEMS gyroscopes suffer some problems like large drift and acoustic sensitivity, compare with MEMS accelerometers. So the design of low cost inertial measurement system without using the gyroscope, and based on a suitable geometry configuration of accelerometers is considered in literature in recent years. The goal of this research is to design and manufacture of such free gyroscope measurement unit. For this purpose, first an appropriate geometry configuration of accelerometer is proposed then the mathematical relationship between the output of linear accelerometers and linear and revolving acceleration of the center of mass of the structure is derived and then the angular velocities are estimated. The proposed free gyroepocs IMU is constructed using the ADXL345 accelerometers as sensors and the ARM-LPC1768 microcontroller as processing unit. The experimental results using a rotating table as reference are gathered in the Lab. The results show the suitable performance of the measurements unit.

This paper aims at investigating the mechanical behavior of a nonlinear system consisting of two coupled beams and a PZT material attached on each beam, excited with a single resonant frequency, for energy harvesting. In order to model the beams, in-extensional assumption and Euler-Bernoulli beam theory are utilized. It is assumed that the beams undergo large amplitude vibrations; which necessitates the application of a nonlinear theory which is taking into account curvature-related and inertial-related nonlinearities. Numerical studies were carried out to study the effect of the different parameters such as external resistance load, gap distance between beams on the nonlinear behavior of the system. It was obtained that as the gap distance between beams decreases, the scavenged power increases and the system behavior tends to exhibit non-periodic response. In addition, a comparison was done between linear and nonlinear systems shown that considering nonlinearity in the system accompanies a shift in the resonance frequency and induces hardening nonlinear behavior in the system.

In this paper, free vibration of functionally graded carbon nanotube annular sector plates is studied. Distribution of carbon nanotubes is continuous and meaningful and gradual changes of materials in the direction of thickness are in the form of volume fraction. Annular sector plate is placed on the Winkler-Pasternak two parameters elastic foundation. The motion equations of plate are derived using the Hamilton principle and the refined plate theory. These coupled differential equations are transformed to ordinary equations using the trigonometric series expansion of space variation functions and then are solved with the help of differential quadrature method. The obtained results are compared with the other researcher’ s results and an excellent agreement can be observed between them. Finally, the effects of different geometric parameters, different distributions of carbon nanotubes in the thickness direction, elastic foundation, and also different boundary conditions on the natural frequencies are investigated.

In this paper, a comprehensive structure is expressed for multidisciplinary design optimization of the unmanned air vehicle and the design optimization of Predator MQ-1 has been studied for validation. The considered modules in the multidisciplinary analysis are performance, aerodynamic, weight, center of gravity, stability and control derivatives, trim and dynamic stability characteristics. The minimization of take-off weight and cruise drag are considered as objective functions. Since two objective functions are considered, therefore multi-objective genetic algorithm (with the non-dominated sorting concept) is used as optimizer which can generate set of optimal solutions as Pareto fronts. A method based on fuzzy logic named satisfaction degree function is expressed for final solution selection. The strengths of this paper are its comprehensiveness (the number of design modules, the number of design variables and constraints) and the presentation of a simple and efficient method for final solution selection. The optimization results show the effectiveness of the structured framework and suggested method.

In this paper, a fuzzy robust backstepping control is presented to control of underactuated mechanical systems with two-degrees of freedom. To do this, the system is divided into two first and second subsystems. Subsequently, for each of these sub-systems, a robust backstepping controller is designed. The mathematical proof shows that the first and second subsystems, with the application of controllers in the presence of existing structured and un-structured uncertainties, have global asymptotic stability. Because this system only has one input, so simultaneous control of the first and second subsystems will not be possible. For this reason, for connecting sub-systems, a function with specific characteristics is defined, which can be used to control these subsystems simultaneously, and also the global asymptotic stability of closed loop system in the presence of existing uncertainties can be guaranty. Then, using fuzzy logic, a fuzzy approximator is presented to implement this particular function. Since the switching terms are used in proposed control input, the occurrence of undesirable chattering phenomenon in the control input is inevitable. Therefore, using fuzzy theory, a solution is proposed to overcome this phenomenon in the amplitude control input.

In this article, an analytical solution for buckling of annular sectorial porous plates, is presented. At first, based on first order shear deformation plate theory, the governing equilibrium equations and boundary conditions are obtained using minimum total potential energy principle. Then, the stability equations of the plate, are derived in terms of infinitesimal displacements using adjacent equilibrium criterion. Since these equations are highly coupled, it is so difficult to find an analytical solution for them. So, by introducing four auxiliary functions and doing some mathematical manipulations, the stability equations are decoupled and converted to two independent differential equation which can be solved analytically. For this purpose, it has been assumed the simply supported boundary conditions for the radial edges and desired boundary conditions for the circumferential edges of the plate. Finally, the critical buckling load has been calculated for different conditions of the plate. In section of numerical results, the effect of different geometrical parameters, such as sector angle, thickness and inner radius of the plate, also effect of porosity of the plate upon the critical buckling load has been studied for different arbitrary boundary conditions on circumferential edges. The result show that the effect of increase in porosity of the plate upon decrease of the critical buckling load is significantly fewer than the effect of geometrical parameters and the boundary conditions.

Inertial navigation is a method to determine the position, velocity and attitude of a vehicle. In these systems, three perpendicular accelerometers and three perpendicular gyroscopes are used to measure linear accelerations and angular velocities of vehicles, respectively. Using some special equations and the measured accelerations and angular velocities, the position, velocity and attitude of a vehicle can be determined. Although these systems have great advantages, some disadvantages such as the increase of error position, velocity and attitude of vehicle by the passage of time exist. These disadvantages are due to errors of inertial sensors. In this paper, firstly, a suitable error model of inertial sensors is proposed. In the following, to decrease these errors and to correct the operation of inertial navigation system; the INS is integrated with GPS. Integration of INS and GPS is done using extended Kalman filter. To this purpose, required equations and relations for integration of INS and GPS are extracted and proposed completely and illustratively. Finally, the simulation of integration of INS and GPS is presented for two different motion scenarios. The results of simulation show great improvements in characteristic of INS+GPS system in comparison to INS individually.