نشریه مهندسی مکانیک ایران
سال بیست و سوم شماره 4 (پیاپی 65، زمستان 1400)

This paper proposes an optimal H adaptive observer based on Linear Matrix Inequality (LMI) for fault estimation (FE) with a sliding mode adaptive fault tolerance (FTC) controller (ASM) to propose a fault for the three-degree helicopter model. Has been. In this approach, the system states and the effects of the types of faults (shrinkage, loss of efficiency and locking of the operator) occurring in the operator, uncertainties in system dynamics and operators in the presence of external perturbation and noise are estimated by the adaptive observer. The saturation phenomenon is also considered in this study. Since in practice, for the large control signals, the actuators become saturated, the saturation effect of the actuators is modeled and the saturation effect is estimated by the observer. In the end, simulation results are presented on the dynamics of three degrees of freedom helicopter to demonstrate the effectiveness of the proposed approach, which results in satisfactory and satisfactory performance of the proposed algorithm.

Nonlinear dynamic inversion is one of the well-known methods in the field of dynamic flight control, which its development refers to the Incremental Nonlinear Dynamic Inversion (INDI). Based on this, in this paper, the non-linear slow and fast modes of the aircraft is separated into two parts. Then, a distinct control is designed for each part. In the outer and inner loops, the PID and the sliding mode controller are designed, respectively. In addition stability analysis, the simulation results for Boeing 747 are presented and compared with the reference model modes and the conventional INDI.Nonlinear dynamic inversion is one of the well-known methods in the field of dynamic flight control, which its development refers to the Incremental Nonlinear Dynamic Inversion (INDI). Based on this, in this paper, the non-linear slow and fast modes of the aircraft is separated into two parts. Then, a distinct control is designed for each part. In the outer and inner loops, the PID and the sliding mode controller are designed, respectively. In addition stability analysis, the simulation results for Boeing 747 are presented and compared with the reference model modes and the conventional INDI.

Fuel consumption in the transportation has been rising in recent decades and consequently,, it has increased pollution and environmental footprint. To address this worldwide problem, the aim of this study is to design a high-level controller with the capability to be implemented to a hybrid electric car in real time, while optimizing fuel consumption and drivability. To achieve this goal, nonlinear model predictive control is utilized based on the longitudinal dynamics of the powertrain. First, the controller is designed for a specific reference. In the next step, the controller is set for a wide range of reference inputs, through tuning the weighting parameters of the optimal control problem. It ultimately shows that all control targets are satisfied. Also applying the proposed energy management system to the powertrain model leads to considerable fuel consumption reduction. Meanwhile, the controller has the capability of being implemented in real time while considering the complex dynamics of the system.

In this article, the vibrations suppression of Timoshenko beam with or without fluid loading has been studied. Firstly, free vibrations of the beam without fluid loading and under fluid loading was studied and then by utilizing of control actuators, beam vibrations with or without fluid loading was dissipated. Stabilization proof has been accomplished by use of Lyapunov control concept and adopting Lyapunov functional, for both cases. In this research, the coupled governing equation of the beam and the fluid has been presented and by utilizing boundary control actuators and using boundary actuators just in the beam boundary, the beam vibrations and fluid motion was stabilized simultaneously. Afterwards, ABAQUS commercial software was used to verify the numerical results. It was been clear the beam vibrations in the presence of the fluid have the lower frequencies due to augmented mass of the fluid and therefore, the vibrations dissipation of the beam will be slower that the dry beam.

In this study, we designed a time-invariant controller for the dynamic stabilization of a five-link runner robot in two dimensions. The running is modeled with three phases of single-stance phase, flight phase, and collision phase. The dynamic equations of the robot in each phase were extracted by the Lagrange method. The robot's heel-strike is also rigidly modeled. The controller in each phase guides the robot by zeroing predetermined outputs in the form of path trajectories via the feedback linearization method. The outputs are designed so that a rhythmic running will be presented by the robot on a limit cycle. The created limit cycle has been determined and its stability has been investigated using the Poincare return map. The robot's controller robustness to disturbances has been investigated and shown that the controller can return the robot to a limit cycle with a deviation of 20% with respect to the stable limit cycle. It has been shown that the relevant geometry by the proposed controller can absorb the gait into the limit cycle in conditions of deviation of 20% in 10 steps.

Gearboxes may be defective during the manufacturing, assembly or operation process. In gearbox manufacturing factories, it is important to identify defective gearboxes to prevent them from entering the consumption cycle. Audio signals indicate the operation of the gearbox and the condition of its internal components. Therefore, this system is a powerful method to diagnose the gearbox healthy or defective in different gears. In this study, intelligent gearbox troubleshooting using audio signals has been done. After receiving the audio signals, suitable algorithms for troubleshooting were proposed and based on that, the troubleshooting process was performed. In this test, the gearbox of the Thunder 90 passenger car in the assembly line was checked for the health or defect. The received audio signals are first processed in the time, frequency (fast Fourier transform) and time-frequency (discrete wavelet transform) domains. Then the feature was extracted from the processed signals in all three domains of time, frequency and time-frequency; Then, using the error test method and statistical inference method, the desired characteristics were selected for use in classification. Then, using various methods of artificial neural network classification and support vector machine, the intelligent diagnostic process was performed. The results showed that the backup machine classification method on data processed with discrete wavelet transform has an average error of less than 9%. This error is less than the error of other signal processing and classification methods in this experiment.

The effect of ground proximity on the some performance parameters of tandem rotors was measured using a multifunctional test rig in this study. Trust, produced power and induced power measurements of the rotors were performed in three different overlap values ​​to investigate the effects of ground proximity on these values ​​in hover flight. The results showed that the positive effect of ground proximity on the produced trust of tandem rotors is more than single rotors. In the ground effect, as the amount of overlap of the tandem rotors increased and the effect of the fountain flow recirculated from the ground increased, the amount of thrust increased . The results of power measurements showed that with decreasing the height of the rotors in the ground effect, the amount of induced power as well as the negative effect of aerodynamic interference due to their overlap decreased, These findings lead to a new approach to evaluating the performance of this type of helicopters.

By reviewing the research conducted on the eddy current braking system's analysis and optimization, it is observed that eddy current braking's physical characteristics are not studied in the automotive application, and its braking torque is not sufficient. In this paper, the governing equations of the braking torque of the eddy current brake with the addition of skin effect and heat are applied, and the results of the two basic and modified models are compared. Then the sensitivity analysis was performed by the finite element method. The analysis results show that by applying the skin effect and heat, the skin effect and heat, the braking torque increases and decreases, respectively. The sensitivity analysis results show the effect of the system's geometric, dynamic, and electromagnetic parameters and structural modifications on the initial value, peak value, and durability of the braking torque produced by the eddy current brake.Keywords: Eddy currentbraking, braking torque, skin effect, heat effect, sensitivity analysis

In this study, the forced vibrations of an annular circular plate with clamped edges under harmonic load is investigated. Analysis of circular plate is based on First-order Shear Deformation Theory (FSDT). The pseudoelastic behavior is simulated by Boyd-Lagoudas constitutive model. The Hamilton’s principle is used to obtain the equations of motion.In the state without phase change (pure austenite) the plate was examined in nonlinear conditions and compared with the existing reference.Differential Quadrature, Newmark methods, and convex cutting plane mapping algorithm are utilized to get the time and frequency responses of the plate. The phase transformation effects are studied on the time and frequency responses of the plate. Also, the harmonic load and the harmonic load, with a constant value are investigated. Then, the accuracy of these results is checked with the available literature and FEM software ABAQUS. The results indicate that the alloy phase transformation leads to reduced material strength and the nonlinear behavior of the alloy.

These days, regarding to advanced technologies, the use of ultralight aircraft for transportation and goods movement has been attended by industries and people. One of the major challenges for ultralight aircraft designers is related to reduction of engine vibrations. In this paper, determination of torsional damper for this aircraft engine types and their effect on reducing vibrations by combining three experimental, analytical and numerical methods are discussed. Starting with dynamic analysis and coding in MATLAB software, the system gas pressure and torque were validated with experimental results with less than 2% differences. Then the amount of angular displacement was validated at maximum rotating velocity with 1.86% difference by numerical and analytical methods, then the natural frequencies of system were obtained. Finally, the equation was extracted in order to determine the appropriate damping coefficient and its characteristics were determined. The results showed that using the damper reduces the system vibrations amplitude up to 40%.