2D Omni-Directional Wireless Power Transfer Modeling for Unmanned Aerial Vehicles with Noncollaborative Charging System Control

Wireless power transfer (WPT) has been extensively studied from various aspects such as far field and near field, operating frequency, coil design, matched capacitance values, misaligned locations of transmitting and receiving coils, distance variance between them, target loads in the specific locations, environment, and operating conditions. This is due to the usefulness of WPT technology in many applications, including the revolutionary method of auto-recharging of unmanned aerial vehicles (UAVs). This paper presents analytical modeling of a WPT-link with two orthogonal transmitting coils arranged to produce an omnidirectional magnetic field suitable for charging a moving rotating load, maximizing energy transfer without any feedback from the receiving end. To achieve a suitable 2D WPT simulation system, as well as an accurate control design, the mutual coupling values in terms of receiver angular rotation are simulated using Ansys software. Power transfer is maximized by using extremum seeking control (ESC), making use of the input power as an objective function with specific parameter values that represent the WPT model to obtain the results. The results shown are those of the input power transmitted by the transmitting-end coils to a load of an orbiting mobile UAV. Based on the simulation results, the controller can achieve maximum power transfer in 100 µs of duration when the speed of the UAV is close to 314 rad/s.

Numerical and Experimental Investigation of a Semi-Active Vibration Control System by Means of Vibration Energy Conversion

A vibration control concept based on vibration energy conversion and storage with respect to a serial-stiffness-switch system (4S) has previously been proposed. Here, we first present a rotational electromagnetic serial-stiffness-switch system as a novel practical vibration control system for experimental validation of the concept and, furthermore, an improved control strategy for higher vibration suppression performance is also proposed. The system consists of two spring-switch elements in series, where a parallel switch can block a spring. As an alternating mechanical switch, the experimental system uses two electromagnets with a shared armature. By connecting the armature to the rotating load or the base, the electromagnets decide which of the two spiral springs is blocked, while the other is active. A switching law based on the rotation velocity of the payload is used. Modelling and building of the experimental system were carried out. The corresponding experiment and simulation were executed and they matched well. These results prove that our serial-stiffness-switch system is capable of converting vibration energy and realizing vibration reduction under a forced harmonic disturbance. The effects of disturbance frequency, disturbance amplitude and sampling frequency on the system performance are shown as well. A position feedback control-based switching law is further put forward and experimentally verified to improve the repositioning accuracy of the disturbed system.

Study on the influencing factors of existing buildings green renovation in old residential areas

Based on problems existing in the green transformation of existing buildings in old residential areas, this paper aims to find out the influencing factors that hinder the green transformation of existing buildings in old residential areas, so as to change the situation that the green transformation of existing buildings in old residential areas advances slowly. It uses the grounded theory based on “science and technology literature” and factor analysis method to determine the 16 key influencing factors and importance ranking, reliability test and validity test, and calculates the initial load square sum of squares, rotating load characteristic value, and the cumulative value indicators to extract six common factors and put forward some proposals for the results obtained from the analysis. Furthermore, it provides decision-making reference for the implementation of green transformation of existing buildings in old residential areas.

Nonlinear vibrations of a thin isotropic circular plate subjected to moving point loads

Here, we have studied the linear and nonlinear vibrations of a thin circular plate subjected to circularly, radially, and spirally moving transverse point loads. We follow Kirchoff’s theory and then incorporate von Kármán nonlinearity and employ Hamilton’s principle to obtain the governing equations and the associated boundary conditions. We solve the governing equations for the simply-supported and clamped boundary conditions using the mode summation method. Using the harmonic balance method for frequency response and Runge-Kutta method for time response, we solve the resulting coupled and cubic nonlinear ordinary differential equations. We show that the resonance instability due to a circularly moving load can be avoided by splitting it into multiple loads rotating at the same radius and angular speed. With the increasing magnitude of the rotating load, the frequency response of the transverse displacement shows jumps and modal interaction. The transverse response collected at the centre of the plate shows subharmonics of the axisymmetric frequencies only. The spectrum of the linear response due to spirally moving load contains axisymmetric frequencies, the angular speed of the load, their combination, and superharmonics of axisymmetric frequencies.

Loss Factor of Elastomeric Dampers for Rotating Machinery Application

Elastomeric dampers have potential application in rotating machinery vibration control. They are however not widely used due to lack of reliable data on their loss factor. Most available data on these dampers are obtained from testing undertaken during stationary condition of the shaft. When the shaft rotates, the dampers are subjected to rotating load that may affect their loss factor. The effect of shaft rotation on the loss factor is experimentally examined in this work. Impact test was used to determine the frequency response function (FRF) of the dampers. For the dampers subjected to rotating load, the loss factor values derived from the FRF was found to be in good agreement with those determined from the half-power bandwidth method. The results further showed that the loss factor at resonant frequency determined from testing of the dampers under stationary shaft condition underestimates the values of the loss factor when the shaft is rotating. The effect of shaft rotation on the values of the damper’s loss factor was more noticeable for the response in the X-direction as opposed to the Y-direction, indicating that pre-strain plays a more dominant role in influencing the loss factor of the dampers compared to the dynamic amplitude.

A new methodology for the estimation of wheel–rail contact forces at a high-frequency range

Online measurement of wheel–rail contact forces is nowadays in demand for evaluating safety and manoeuvring the condition in real time and in real operation. In this study, the wheel–rail contact forces are estimated using a novel indirect identification method based on the measured radial strain on the wheel web. Further, the strain response of the rolling wheel is derived using an analytical solution of the disk under a rotating load, and a scheme was prepared for the identification of the rolling wheel parameters and its corresponding characteristic matrix. An appropriate angular strain configuration is employed to eliminate the effect of wheel rotation. The Tikhonov regularization technique is employed to solve the ill-posed least square problem and to attenuate the effect of noisy measurement and numerical uncertainty during the estimation of the forces. A finite element model of the rotating load is then constructed to investigate the effectiveness and accuracy of the proposed methodology. The effects of the rotating speed, loading and measurement noise on the estimated normal force are studied. It is found that neglecting the effect of the rotating speed causes a notable error particularly in the high-speed range.

Complete and Simplified Models for Estimating Vibration Instability of Cyclically Symmetric Ring Structures: Comparison and Verification

In-plane vibration of cyclically symmetric ring structures is examined with emphasis on the comparison of instabilities estimated by complete and simplified models. The aim of this paper is to understand under what conditions and to what degree the simplified models can approach the complete model. Previous studies develop time-variant models and employ perturbation method by assuming weak support. This work casts the rotating-load problem into a nonrotating load problem. A complete model with time-invariant coefficients is developed in rotating-support-fixed frame, where the bending and extensional deformations are incorporated. It is then reduced into two simplified ones based on different deformation restrictions. Due to the time-invariant effect observed in the rotating-support-fixed frame, the eigenvalues are formulated directly by using classical vibration theory and compared based on a sample structure. The comparisons verify that the two types of models are comparable only for weak support. Furthermore, the simplified models cannot accurately predict all unstable behaviors in particular for strong support. The eigenvalues are different even in comparable regions. For verification purpose, the time-invariant models are transformed into time-variant ones in the inertial frame, based on which instabilities are estimated by using Floquét theory. Consistence between the time-invariant and -variant models verifies the comparisons.

Stability-Guaranteed Anti-Sway Controller Design for a Redundant Articulated Hydraulic Manipulator in the Vertical Plane

Articulated hydraulic manipulators are widely used for moving heavy loads. Commercial manipulators are most often equipped with a rotating load-grasping tool connected at the end of the manipulator via a pair of passive (unactuated) revolute joints. In free-space motion, these passive joints are subject to swaying motions due to the manipulator tip accelerations. Because these passive joints are not directly controllable due to their passive nature, a skilled driver is needed to compensate for the load swaying. In this paper, we extend the nonlinear model-based Virtual Decomposition Control (VDC) theory to cover anti-sway control of underactuated multiple degrees-of-freedom (DOF) hydraulic redundant manipulators. The proposed nonlinear controller performs the control design and stability analysis of the hydraulic robotic manipulator at the subsystem level. Experiments are conducted in a full-scale loader manipulator to verify that the proposed controller can efficiently damp the load swaying in a case study of redundant vertical plane motion.

A direct numerical approach to compute the nonlinear rotordynamic coefficient of the noncircular gas journal bearing

Gas bearings are extensively used in several industrial applications to support the rotating load at high speed due to its favorable characteristics. The numerical computation of the gas film damping and stiffness coefficients is a difficult task due to nonlinearity in the Reynolds equation for compressible lubricant. In the present work, a numerical method based on the finite element method is developed for the direct computation of gas film damping and stiffness coefficients. In this method, a double partial differential equation approach has been used to compute the dynamic characteristics. Further, the numerical results presented shows that the bearing ellipticity ratio significantly affects the nonlinear trajectory of the journal.