The voltage-mode first order universal filter using single voltage differencing differential input buffered amplifier with electronic controllability

In this research contribution, the electronically tunable first-order universal filter employing a single voltage differencing differential input buffered amplifier (VD-DIBA) (constructed from two commercially available integrated circuit (IC): the operational transconductance amplifier, IC number LT1228, and the differential voltage input buffer, IC number AD830), one capacitor and two resistors. The features of the designed first order universal filter are as follows. Three voltage-mode first-order functions, low-pass (LP), all-pass (AP) and high-pass (HP) responses are given. The natural frequency (𝜔0) of the presented configuration can be electronically adjusted by setting the DC bias current. Moreover, the voltage gain of the LP and HP filters can be controllable. The phase responses of an AP configuration can be varied from 00 to −1800 and 1800 to 00. The power supply voltages were set at ±5 𝑉. Verification of the theoretically described performances of the introduced electronically tunable universal filter was proved by the PSpice simulation and experiment.

Enhanced transmission efficiency of magneto-inductive wave propagating in non-homogeneous 2-D magnetic metamaterial array

In this work, we investigate the propagation of magneto-inductive waves (MIWs) in ordering magnetic metamaterial (MM) structures. The proposed non-homogeneous MM slab consists of 9 × 9 MM unit cells constructed from a five-turn spiral embedded on an FR-4 substrate. External capacitors with the value of 40 pF or 50 pF were added to control the resonant frequency of each unit cell in accordance with the waveguide configurations. The characteristics of metamaterial structures, such as negative permeability, current ratio, transmission response, and field distribution in the waveguide, have been thoroughly analyzed by simulation and experiment. Because of the strong magnetic field confinement in the waveguide, the transmittance after nine elements of the non-homogeneous MM slab is 5.2 times greater than that of the homogeneous MM slab. This structure can be applied to the planar near-field wireless power transfer, position sensor, and low-frequency communication.

Broadband low-frequency acoustic absorber based on a metaporous composite

Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering. Here, we numerically and experimentally present a design of a broadband low-frequency absorber based on an acoustic metaporous composite (AMC). The AMC absorber is constructed by embedding a single metamaterial resonator into a porous layer. The finite element simulations show that a high absorption (absorptance A > 0.8) can be achieved within a broad frequency range (from 290 Hz to 1074 Hz), while the thickness of AMC is 1/13 of the corresponding wavelength at 290 Hz. The broadband and high-efficiency performances of the absorber are attributed to the coupling between the two resonant absorptions and the trapped mode. A good agreement between the numerical simulation and experiment is obtained. Moreover, the high broadband absorption can be maintained under random incident acoustic waves. The proposed absorber provides potential applications in low-frequency noise reduction especially when limited space is demanded.

Motion analysis of screw drive in-pipe cleaning robot

In-pipe cleaning robots often need to carry cleaning tools, and their tails are connected with cables such as water pipes and air pipes. Especially when cleaning vertical straight pipes and curved pipes, a greater traction is required. Therefore, a new type of screw drive in-pipe cleaning robot was designed in this paper. The robot solves the problems of small traction, complex structure, and unstable motion of the in-pipe cleaning robot. The kinematics modeling was carried out on the screw drive in-pipe cleaning robot’s screw module for generating traction, and the force analysis was performed on this basis. The function model of the torque, air pressure, and traction of the screw module was established, which was verified by the simulation and experiment. The results show that the screw in-pipe cleaning robot has a large traction, stable operation, and can be well adapted to the vertical straight pipes and curved pipes.

Assembly and Disassembly Mechanics of a Cylindrical Snap Fit

Snap fit is a common mechanical mechanism. It uses the physical asymmetry that is easy to assemble but difficult to disassemble to provide a simple and fast link between objects. The ingenious combination of geometric shape, bending elasticity and friction of the snap fit is the mechanism behind the easy to assemble but difficult to disassemble disassemble. Yoshida and Wada (2020) has done a groundbreaking work in the analysis of the elastic snap fit. During our study of their paper, while we really enjoyed their research, unfortunately we detected several questioning formulations. After careful checking, we found that those formulations are not typographical, therefore it is necessary to make corrections. This paper reformulates the linear elasticity of a cylindrical snap fit, obtains an exact solution and proposes an accurate relation between the opening angle and bending tangent angle. Under the first order approximation, our formulations can reduced to the results of Yoshida and Wada and hence confirms the scientific correctness of Yoshida and Wada's work. Furthermore, this paper also derives a correct vertical displacement expression, and propose a new way of disassembly by bending for the first time and formulate a scaling law by data fitting. All formulations are validated by finite element simulation and experiment. The research here is helpful to the design of elastic snap fit or adjustable mechanical mechanism and metamaterial cell.

Experimental study and numerical simulation of inerter-based systems

Based on a single degree of freedom system, the inerter principles of an inertial mass damper and clutch inerter damper are introduced. The motion equations of the systems are derived, and the rotational speed and damping are considered. In addition, a reducer is innovatively combined with clutch inerter damper to significantly improve the inertance. Accordingly, an innovative reducer clutch inerter damper is proposed. Shaking table experiments are carried out on the uncontrolled inertial mass damper, clutch inerter damper, and reducer clutch inerter damper structures under the inputs of harmonic and seismic waves. Simulation models of the four types of structures are developed, and the validity of the theoretical models is verified by a comparison between the simulation and experiment. Moreover, the nonlinear models of clutch inerter damper and reducer clutch inerter damper are discussed. Finally, according to the test results, the vibration reduction effects of the three inerters are analyzed, and the reasons why they are different from the ideal clutch inerter damper are also explained. The results show that clutch inerter damper, especially reducer clutch inerter damper, has a good vibration damping performance.

A Coupled-Inductor Interleaved LLC Resonant Converter for Wide Operation Range

In this paper, a coupled-inductor interleaved LLC resonant converter (CI-ILLC) was proposed, which can achieve extensive operation range applications by multiplexing inductors and switches. In this proposed CI-ILLC, the coupled-inductor not only serves as a filter inductor but also plays the role of transformer to improve the power density. By changing the modulation methods, the proposed converter can work at three modes for a wide operation range, namely high gain (HG) mode, medium gain (MG) mode, and low gain (LG) mode. Moreover, the interleaved structure greatly reduces the current ripple and current stress of switches. Besides, in HG and MG modes, all switches can realize zero-voltage switching, with high energy transmission efficiency. Finally, the simulation and experiment results of the prototype with 120–200 V input and 50–200 V output are presented to verify the viability of the proposed converter.