A nine degree-of-freedom model of one stage gear system is presented in this research work. The gearbox structure is coupled with the vibration of the gear shaft. The model considers gear size, errors, and faults. The model includes varying meshing stiffness and a realistic representation of the gear transmission error (TE) and gear faults. Gear TE is modeled as a displacement excitation. The model equations are solved using Matlab and using parameters representing a real experimental gearbox rig. Experimental and simulated data are compared for different operating speeds, torque loads, and gear cracks. The simulation results are in good agreement with the experimental ones. The authors believe that the model presented here can be used in studying gear faults and would be very useful in developing gear fault monitoring techniques.
It is projected that, in the following years, the wind‐energy industry will maintain its rapid growth over the last few decades. Such growth in the industry has been accompanied by the desirability and demand for larger wind turbines aimed at harnessing more power. However, the fact that massive turbine blades inherently experience increased fatigue and ultimate loads is no secret, which compromise their structural lifecycle. Accordingly, this demands higher overhaul‐and‐maintenance (O&M) costs, leading to higher cost of energy (COE). Introduction of flow‐control devices on the wind turbine is a plausible solution to this issue. Flow‐control mechanisms feature the ability to effectively enhance/suppress turbulence, advance/delay flow transition, and prevent/promote separation, leading to enhancement in aerodynamic and aeroacoustics performance, load alleviation and fluctuation suppression, and eventually wind turbine power augmentation. These flow‐control devices are operated primarily under two schemes: passive and active control. Development and optimization of flow‐control devices present the potential for reduction in the COE, which is a major challenge against traditional power sources. This review performs a comprehensive and up‐to‐date literature survey of selected flow‐control devices, from their time of development up to the present. It contains a discussion on the current prospects and challenges faced by these devices, along with a comparative analysis centered on their aerodynamic controllability. General considerations and conclusive remarks are presented after the discussion.
This paper pertains to advanced automation of the load transfer process using overhead cranes. Overhead cranes are widely used in various areas of industry, including manufacturing, construction, shipping, etc. Load transfer operations using overhead cranes have to be performed fast and safely. As such, these operations are handled by expert operators1 however, the demand for an automatic consistent and reliable crane operation is on the rise. The crane-load system is highly nonlinear and time-varying, hence, solutions considering model-base approaches may lead to a complicated controller structure. Such a controller may require accurate estimation of the crane system parameters. In this paper we present a new fuzzy logic controller for overhead crane operation. The fuzzy controller is designed based on knowledge of an expert crane operator, and does not require any parameter estimation. It mimics the operator behavior by using the same crane-load system states that are realized by the operator. These states are the trolley position error and the load sway angle. The fuzzy controller action, on the other hand, is the desired trolley speed. The proposed controller is implemented and tested on a small-scale overhead crane. Experimental results show robust operation of the fuzzy controller as compared with that of a conventional controller.
This paper studies the aeroelastic behavior of telescopic, multi-segment, span morphing wings. The wing is modeled as a linear, multi-segment, stepped, cantilever Euler–Bernoulli beam. It consists of three segments along the axis and each segment has different geometric, mechanical, and inertial properties. The aeroelastic analysis takes into account spanwise out-of-plane bending and torsion only, for which the corresponding shape functions are derived and validated. The use of shape functions allows representing the wing as an equivalent aerofoil whose generalized coordinates are defined at the wingtip according to the Rayleigh–Ritz method. Theodorsen’s unsteady aerodynamic theory is used to estimate the aerodynamic loads. A representative Padé approximation for the Theodorsen’s transfer function is utilized to model the aerodynamic behaviors in state-space form allowing time-domain simulation and analysis. The effect of the segments’ mechanical, geometric, and inertial properties on the aeroelastic behavior of the wing is assessed. Finally, the viability of span morphing as a flutter suppression device is studied.
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