نشریه مهندسی هوانوردی
سال نوزدهم شماره 1 (بهار و تابستان 1396)

In this article, Design and simulation of model predictive control for turbojet engine fuel control of the missile has been proposed. Operational and structural constraints of the engine are controller design challenges. The control system must make sure that the engine always works in full health condition, i.e. without acceleration of the shaft speed, staling compressor, ignition of the combustion chamber, turbine temperature increase etc. In this regard, a controller is needed which can take into account these constraints while obtaining a suitable control signal. Using the model predictive control as well as taking into the account the limitations of various parameters such as rotational speed, turbine inlet temperature, stalactite compressor, etc. the control of turbojet engine fuel for a linear model of this engine at a functional point has been investigated. In the final section, the performance results of this controller has been compared with the results of Min-Max controller and indicated that in the predictive control, in addition to producing optimized the optimal control signal, all constraints are in the desired range.

An adaptive higher order controller for uncertain chaotic systems is designed in this paper. Employing second order integration and second order derivative terms to PID controller lead to deflect the steady state error and increase of convergence speed of the systems. Concept of sliding mode used to adaptation of designed controller. Also an adequate supervisory controller employed to avoid divergence of states of the systems. The ultimate controller is sum of these controllers. In addition, in order to description of chaotic systems, plant uncertainty employed to demonstrate robustly of system. Also, external disturbances are considered. The results illustrate the effectiveness of the proposed robust adaptive higher order controller.

In this paper, a new automatic landing system is suggested for unmanned aerial vehicles based on a groundbased vision system. Auto-land is the main challenge in all kinds of UAVs where the most accidents happen in the phase of flight. A low-cost auto-landing system, which is useful for variety types of UAVs and movable between different runways, is required in UAV’s industries. In the proposed method, a vision navigation system equipped with a tracking systems and a Laser distance finder is mounted on the center and end of the runway. The navigation system calculates the position of the target UAV and communicates it to the UAV. Some computations show that the accuracy of the system is approximately 20 times more than GPS for landing phase. In follows, a landing algorithm is suggested for obtaining optimal flight path for a safe landing. The algorithm employs two guidance systems for calculating the desired altitude based on image vector field guidance law (IVFGL) and desired heading based on descent and flare phases. The results of this article are investigated by implementation with hardware in the loop on the UAV.

In this research, the experimental investigation of unsteady flow around a cylinder model with three plates perpendicular to it has been discussed. This study has been done at different speeds, primary model angle of attacks and length ratios. The results show that the model has steady and unsteady oscillation and rotational motions. These types of behaviors depend on the plate’s length ratio, primary object angle of attack, and free stream velocity. The model has damping motion around an angle of 60 degree, at low speed and length ratio. The greatest oscillational or rotational flow has appeared at initial angle of attack of 0 degree. In low length ratio, the regime of motion is oscillations that it changed to rotational motion when the length ratio and free stream velocity increase. The variation of angular velocity at length ratio of 1 and 4, with respect to time, are accompanied with reduction of vibrations range per motion. Also, over time, the vibrational velocity of the model is reduced. In addition, the results show that by increasing the Reynolds Number, Strouhal number becomes constant.

In this paper, a model is used to harvest energy from the piezoelectric. The harvested energy is in large uncertainties such as uncertainties caused by the material properties, loading conditions and the uncertainty resulting from the tolerances sensitive. Therefore, in order to achieve the proper functioning on the uncertainties, the reliability based design optimization is planned. The results show that if reliability base design optimization method with to the uncertainty caused by tolerances to be done for energy harvesting systems, power output requirement and also ensure the proper functioning significantly increased when compared with the stochastic optimization. In this study, a piezoelectric vibration energy harvester designed to replace the battery supply for actuators and sensors in the unmanned aircraft with respect to predetermined power requirement. In this case, the vibration source is the aircraft engine vibrations.

In this paper, FLUENT software capabilities are used to calculate and compare the sound produced by the flow of air through several geometries with different cross-sections. The method used in this simulation is the combination of the large eddy simulation turbulence model and Ffowcs-Williams and Hawkings acoustic model. Three cross-sections of circle, square and triangle are studied. The aim of this study, in addition to assess the ability and accuracy of numerical calculation of the farfield sound, is to find the maximum sound pressure level of each simple cross section. Two microphones are defined over long distances of the numerical domain to compare the numerical sound calculations with experimental results. After the necessary calculations, results are provided as sound pressure level curves of turbulence solver using the acoustic analogy at microphones locations. Respectively, the received sound pressure at the microphone farther- located is in lower quantity and the arrival time of the sound at that location is longer. The results show that the maximum sound pressure level, at the same velocity, belongs to circular, triangular and square cross-sections respectively.