Mechanical Switch Research Articles

Design of Adjustable Cogging Torque Permanent Magnet Machine With High Contrast Ratio

This article presents a new adjustable cogging torque permanent magnet (ACT-PM) machine, which can provide two distinct operating states: the low cogging torque (LCT) state and the high cogging torque (HCT) state. The contrast ratio is defined as the ratio of the cogging torques between HCT and LCT states. The LCT state of this machine is designed to have similar performance as a conventional permanent magnet machine, with high average torque and low torque ripple that offer smoothness and control precision. For the HCT state, on the other hand, the machine generates HCT that can provide passive self-lock ability under power-OFF condition, serving as a parking brake that prevents the driveshaft from rolling. Consequently, a conventional mechanical parking brake that has corrosion and wearing-out concerns can be removed. The potential applications of this machine include auto-guided vehicles and other types of electric vehicles. This article illustrates the design flowchart and the proposed candidate structure, followed by the investigation and comparison of electromagnetic performances between different stator/rotor combinations. Then, multiobjective optimization and single parameter optimization are applied to the candidate structure to further improve the contrast ratio for cogging torque. A prototype machine with the optimal design parameters is fabricated and experimentally verified, where a mechanical switch is designed to adjust the machine between LCT and HCT states. The test result shows a good agreement with the finite-element analysis, and this confirms the feasibility of the proposed ACT-PM machine.

Ferroelasticity in Organic–Inorganic Hybrid Perovskites

Molecular ferroelastics have received particular attention for potential applications in mechanical switches, shape memory, energy conversion, information processing, and solar cells, by taking advantages of their low-cost, light-weight, easy preparation, and mechanical flexibility. The unique structures of organic-inorganic hybrid perovskites have been considered to be a design platform for symmetry-breaking-associated order-disorder in lattice, thereby possessing great potential for ferroelastic phase transition. Herein, we review the research progress of organic-inorganic hybrid perovskite ferroelastics in recent years, focusing on the crystal structures, dimensions, phase transitions and ferroelastic properties. In view of the few reports on molecular-based hybrid ferroelastics, we look forward to the structural design strategies of molecular ferroelastic materials, as well as the opportunities and challenges faced by molecular-based hybrid ferroelastic materials in the future. This review will have positive guiding significance for the synthesis and future exploration of organic-inorganic hybrid molecular ferroelastics.

A New Thyristor-Based DC Circuit Breaker Using Diode Clamping Switching

It has been widely accepted to apply dc circuit breakers (DCCBs) to protect dc grids. Nevertheless, existing DCCBs have one or more following limitations: insulation recovery scheme of mechanical switch, additional precharge power supply, high conduction loss, unreliable current-breaking process, and unidirectional design. In this letter, a new DCCB with low conduction loss, simple precharging scheme, and reliable breaking ability is proposed. The proposed DCCB could break both fault and operating current actively with the same simple operation sequences. Moreover, bidirectional topology possessing all advantages mentioned previously is also presented. Topology introduction, parameters designing, and scaled-down experiment of the proposed DCCB are all presented in the letter.

Adaptive thermoelectric cooling system for Energy-Efficient local and transient heat management

Current cooling systems such as convection-based heat sinks and vapor compression refrigeration systems are frequently inefficient in managing localized and transient heat sources due to their bulky design, large energy consumption, and slow response time. Here, we propose an adaptive thermoelectric cooling system that uses an array circuit of thermoelectric coolers to cool locally and eliminate transient heat efficiently. Compared to existing thermoelectric cooling systems, the proposed system provides a merit of combined functionalities of detecting and cooling localized and transient heat sources. As a proof of concept, six thermoelectric coolers are used for both tracking the temperature and cooling the hot spots without additional sensors. The temperature for each thermoelectric cooler is continuously monitored by scanning the Seebeck voltage of each cooler using a mechanical switching system. When localized heat is applied to specific locations and the temperatures of those locations exceed a designated limit, only particular thermoelectric coolers are activated to cool the over-heated spots selectively. The adaptive thermoelectric cooling system demonstrates fast cooling and effectively maintains the system temperature below the target temperature. Numerical analysis verifies that the adaptive thermoelectric cooling system offers exclusive cooling on hot spots preventing overcooling in other regimes, which makes it consume 47% less power than a conventional bulk thermoelectric cooling system. The proposed cooling system may provide an efficient heat management platform for numerous devices.

Substrate Stiffness Controls the Cell Cycle of Human Mesenchymal Stem Cells Via Cellular Traction

The microenvironment of human mesenchymal stem cells (hMSCs) regulates their self-renewal and differentiation properties. Previously, it was shown that hMSCs remain quiescent on soft (0.25 kPa) polyacrylamide (PA) gels, but re-enter the cell cycle on a stiff (7.5 kPa) gel. However, how cells behave on intermediate stiffness and what intracellular factors transmit mechanical changes to cell interior, thereby regulating cell cycle, remained unknown. In this work, we have demonstrated that PA gels of stiffness between 1 kPa and 5 kPa act as a mechanical switch from quiescence to proliferation in the cell cycle of hMSCs. Further studies with ROCK inhibitor Y-27632 have revealed that contractile proteins, but not cell spread area, account for the sensitivity of hMSCs towards substrate stiffness, and hence correlates with their changes in cell cycle. These observations therefore suggest that substrate stiffness regulates hMSC proliferation through contractile forces, as generated by cellular contractile proteins in a unique pattern that is distinct from the two other cell types studied here, C2C12 and 3T3.

A Novel Low-Loss Bidirectional T-Source Circuit Breaker With Physical Isolation for Low-Voltage DC Distribution Network

The development of a low-voltage dc distribution network has advanced the research on dc circuit breakers. Compared with the Z-source circuit breakers, T-source circuit breakers offer more advantages and greater research value. However, the existing bidirectional Z-source and T-source circuit breakers still suffer from limitations, such as high conduction loss, complex topology, and no physical isolation. Therefore, to solve these limitations, in this article, a novel low-loss bidirectional T-source circuit breaker with physical isolation is proposed. The proposed circuit breaker employs mechanical switches to reduce conduction loss, realize physical isolation, and change the power-flow direction. Since mechanical switches do not need to operate in the fault-clearing stage, the novel circuit breaker does not generate a dc arc and retains the fast self-shut <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-off</small> characteristic of T-source circuit breakers. Moreover, soft-starting circuit and manual-tripping circuit are integrated into the proposed circuit breaker. The detailed analysis and design equations of the circuit breaker are provided. Finally, the capabilities of the novel circuit breaker are verified by simulation and experiment.

Bidirectional mechanical switching window in ferroelectric thin films predicted by first-principle-based simulations

Mechanical control of ferroelectric domain evolution has attracted much interest over the past decade. Nevertheless, bidirectional 180° mechanical switching, i.e., a complete cycle of mechanical writing and then erasing of a ferroelectric nanodomain, has not yet been realized in tip-film architectures. Here, via first-principles-based molecular dynamics simulations, we demonstrate that bidirectional 180° mechanical switching is possible in tip-film architectures when screening condition of ferroelectric films and tip loading force are within an appropriate window. The switching utilizes a delicate competition between the flexoelectric field and an overlooked effective dipolar field. The effective dipolar field dominates at small tip force and trigger switching from a downward single-domain state to an upward poly-domain state, whereas the flexoelectric field dominates at relatively large tip force and enables a back-switching. Bidirectional mechanical switching is achieved by applying tip force pulses with alternatively varying strength. The dipole-dipole interaction dynamics play important roles in mechanical switching.

Reduced-Time Finite Element Model for Thomson Coil Actuator

With the rapid development of DC systems and the increasing demand for DC circuit breakers, electromagnetic repulsive drive-based Thomson coil actuators (TCAs) are widely investigated to provide high-speed actuating required for ultra-fast mechanical switches, especially used in hybrid DC circuit breakers. The actuating mechanism is required to be fast, reliable, and economic. This also creates the need to perform fast highly accurate modeling, simulation, and optimization to investigate the operating mechanism performance. In this study, the fast-operating mechanism-based Thomson coil repulsive drive actuator modeling is investigated. Two simulation methods, equivalent-circuit method (ECM), and finite element method (FEM) are performed for analyzing the TCA performance. In the ECM simulation, Newton’s equation of motion is solved together with the circuit equations of the coils. On the other hand, the electrical, magnetic, and mechanical coupling is solved by FEM simulation. A sliding mesh technique is introduced to reduce the computational cost. The two developed solutions were then compared with the experiment for model verification. Results showed that the presented mesh technique was able to significantly reduce the simulation time, and results were in good agreement with the experiment compared to ECM.

3D Printed Acoustically Programmable Soft Microactuators.

The concept of creating all-mechanical soft microrobotic systems has great potential to address outstanding challenges in biomedical applications, and introduce more sustainable and multifunctional products. To this end, magnetic fields and light have been extensively studied as potential energy sources. On the other hand, coupling the response of materials to pressure waves has been overlooked despite the abundant use of acoustics in nature and engineering solutions. In this study, we show that programmed commands can be contained on 3D nanoprinted polymer systems with the introduction of selectively excited air bubbles and rationally designed compliant mechanisms. A repertoire of micromechanical systems is engineered using experimentally validated computational models that consider the effects of primary and secondary pressure fields on entrapped air bubbles and the surrounding fluid. Coupling the dynamics of bubble oscillators reveals rich acoustofluidic interactions that can be programmed in space and time. We prescribe kinematics by harnessing the forces generated through these interactions to deform structural elements, which can be remotely reconfigured on demand with the incorporation of mechanical switches. These basic actuation and analog control modules will serve as the building blocks for the development of a novel class of micromechanical systems powered and programmed by acoustic signals.

A Review on Thomson Coil Actuators in Fast Mechanical Switching

With the rapid development of DC power systems and the increasing demand for DC circuit breakers, electromagnetic repulsive drives-based Thomson coil actuators (TCA) are widely investigated to provide the high-speed actuating required for ultra-fast mechanical switches, especially those used in hybrid DC circuit breakers. The actuating mechanism is required to be fast, reliable, and economic. This article summarizes the development of Thomson coil actuators in circuit breakers in recent years, further illustrating the basic principles and the actuator topology. In addition, it discusses the various structural components of TCA and describes the utilized modeling and simulation methods. The main objective was to provide a comprehensive overview of the TCA field.

A Series-Type Hybrid Circuit Breaker Concept for Ultrafast DC Fault Protection

A new series-type hybrid circuit breaker (S-HCB) concept for dc fault protection is reported that is fundamentally different from other prior-art hybrid circuit breakers (HCB) or solid-state circuit breakers (SSCB) in the literature. The S-HCB conducts its load current through metal wires instead of power semiconductor switches and curtails its fault current to near zero throughout the entire opening process of a series mechanical switch. It offers the low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistance of the conventional mechanical contacts for normal operation and µs-scale fault response even faster than the fast-acting SSCBs. A proof-of-concept S-HCB prototype experimentally demonstrates the interruption of a fault current of 30 A within 10 μs at a dc voltage of 600 V. The operating principle, simulation, and experimental results are discussed in this letter.

Two-Step Dielectric Responsive Organic-Inorganic Hybrid Material with Mid-Band Light Emission.

Hybrid organic-inorganic perovskite (HOIP) have received tremendous scientific attention because of the phase transition and photovoltaic properties. However, achieving the special perovskite structure with both two-step dielectric response and luminescence characteristics is rarely reported. Herein, we report an organic-inorganic hybrid perovskite, [(BA)2 ⋅ PbI4 ] (Compound 1, BA=n-butylamine) by introducing flexible organic cations (HBA+ ), with direct mid-band gap as 2.28 eV. Interestingly, this material exhibits two-step reversible dielectric response at 350 K and 460 K (in heating process), respectively. Besides, the photoluminescence was found: it emits charming green light under 365 nm lamp (Photoluminescence quantum yield is 9.52 %). The outstanding two-step dielectric response and luminescence characteristics of this compound might pave the way for the application of dielectric and ferroelectric functional materials in temperature sensors and mechanical switches.

Combining advanced 3D printing technologies with origami principles: A new paradigm for the design of functional, durable, and scalable springs

Origami has recently emerged as a platform for building functional engineering systems with versatile characteristics that targeted niche applications. One widely utilized origami-based structure is known as the Kresling origami spring (KOS), which inspired, among many other things, the design of vibration isolators, fluidic muscles, and mechanical bit memory switches. Previous demonstrations of such concepts were carried out using paper-based KOSs, which are suitable for conceptual illustrations but not for implementation in a real environment. In addition to the very low durability resulting from the high plastic deformations at the paper folds; lack of repeatability, and high variation of performance among similar samples are also inevitable. To circumvent these issues, this paper presents a novel approach for the design of a non-paper based KOS, which mimics the qualitative behavior of the paper-based KOS without compromising on durability, repeatability, and functionality. In the new design, each fundamental triangle in the paper-based KOS is replaced by an inner central rigid core and an outer flexible rubber-like frame, which are fabricated out of different visco-elastic materials using advanced 3-D printing technologies. The quasi-static behavior of the fabricated springs was assessed under both compressive and tensile loads. It is shown that KOSs with linear, softening, hardening, mono- and bi-stable restoring force behavior can be fabricated using the proposed design by simple changes to the geometric design parameters, further pointing to the vast range of potential applications of such springs.

Development of a Hybrid Fault Current Limiter Using Liquid Metal for Large Capacity MVdc Power Systems

A hybrid fault current limiter (FCL) for medium voltage direct current (MVDC) power systems is introduced in this paper. It achieves low operation loss and high current limiting resistance through the combination of a fast mechanical switch, a magnetic induction module and a number of liquid metal units (LMUs). Firstly, the parameters of the magnetic induction module are designed to achieve a desired fault current commutation process. Then, the working principle of LMU is introduced, and its resistance properties corresponding to the liquid metal arc are studied in detail. Equations are deduced to model the V-I characteristic of LMU. Thus the current limiting performance of the topology can be simulated. To verify the feasibility of the FCL, a 5-kV/5-kA prototype is developed and laboratory tests are implemented. Comparisons with other FCLs are also conducted to demonstrate the advantages of the proposed one. It is concluded that the prototype provides the basis for further commercial product development.

Metal Oxide Varistor Design Optimization and Main Breaker Branch Switch Control of a Progressively Switched Hybrid DC Circuit Breaker

In this article, metal oxide varistor (MOV) design optimization and switching control in the main circuit breaker (MCB) branch of a progressively switched hybrid dc circuit breaker (DCCB) is presented. A progressively switched hybrid DCCB can achieve faster fault isolation with reduced peak fault current magnitude and transient recovery voltage compared with a regular hybrid DCCB due to its modified switching strategy. Consequently, thermal stress on the semiconductor devices in MCB is significantly reduced. Analytical model of the system dynamics during fault isolation with progressive switching is derived to demonstrate the switching scheme’s effect on the energy-absorbing component, MOV, during turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> process. Derived analytical model in conjunction with the displacement curve of the fast mechanical switch of the hybrid DCCB is utilized to optimize the components of the main circuit breaker branch to reduce MOV degradation through asymmetric energy dissipation. A model of the circuit breaker is built in PSCAD to validate the performance of the proposed optimization method in a 10-kV/250-A system with four stage progressive switching. Additionally, a low voltage system model at 380 V is developed in PLECS for two stage progressive switching that works as the basis of experimental validation. This includes both lookup table-based MOV model and device thermal model for junction temperature estimation. Experimental results are provided for a 380-V system to demonstrate reduced fault current peak in a progressive switching and near uniform energy absorption in optimally selected MOVs.

Mechanical Switching of Ferroelectric Domains in 33‐200 nm‐Thick Sol‐Gel‐Grown PbZr0.2Ti0.8O3 Films Assisted by Nanocavities

AbstractThe mechanical switching of ferroelectric domains is achieved in PbZr0.2Ti0.8O3 thin films obtained by the sol‐gel method for thicknesses up to 200 nm. The dielectric polarization can be switched when a force higher than a given threshold value in the order of some μNewtons is applied with the tip of an atomic force microscope. This threshold is determined as a function of the thickness of the films, and local hysteresis loops are recorded under mechanical stress. The possibility of switching the polarization in such unusually thick films is related to the existence in their volume of physical nanoscale defects, which might play the role of pinning centers for the domains.

Parameters design of voltage sharing components for the series multi‐break mechanical switch

Series multi-break mechanical switch is one of the critical components of high-voltage hybrid DC circuit breakers. However, due to the existence of distributed capacitance, the voltage distribution between the breaks is not balanced. This paper proposed a voltage sharing configuration method of the mechanical switch of hybrid DC circuit breaker, and carried out the static DC voltage and the transient voltage distribution characteristics tests to verify its effectiveness. Considering the influence of whole structure of the circuit breaker, this paper established the electrostatic field model and circuit simulation model of a typical ±535-kV hybrid DC circuit breaker. And it analyzed the influence of single break's opening fault, breaking open distance, and the shielding fitting on the voltage distribution characteristics of series six break mechanical switch. According to the simulation results based on the Zhangbei voltage source converter-based high-voltage direct current project type test parameters, the parameters design of the voltage sharing components of the mechanical switch are obtained, which can meet the voltage sharing coefficient requirement of 95%.

Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films

AbstractFerroelectric polymer films offer strong advantages like mechanical flexibility, biocompatibility, optical transparency, and low‐cost processing. However, their dielectric or piezoelectric performance is often inferior to that of oxide ferroelectric materials. Key to the dielectric or piezoelectric performance of semicrystalline polymers is the enhancement of electric dipolar order that is naturally lower than in crystalline ferroelectrics. Here, reorientation and alignment of the electric polarization in thin films by the mechanical effect of a scanning unbiased force microscopy tip is demonstrated as a versatile tool for nanoscale domain writing. Thin films (50–150 nm) of PVDF‐TrFE (78:22) on graphite are prepared with dense (110)‐oriented β‐phase lamellae randomly oriented in the film plane. The in‐plane polarization can be poled “mechanically” along any deliberately chosen direction in the film plane after vertical electric poling. Domain patterns with resolution down to ≈50 nm are written with four (out of six possible) local polarization orientations. Written domains show excellent long‐time stability. The surface roughening from the mechanical treatment is moderate (rms roughness of 2–3 nm). A ferroelastic origin of the mechanical polarization switching is discussed. Finally, suggestions are made how to utilize the domain patterns in thin film devices.

LC Passive Wireless Sensor System Based on Two Switches for Detection of Triple Parameters.

This paper presents the LC-type passive wireless sensing system for the simultaneous and independent detection of triple parameters, featuring three different capacitive sensors controlled by two mechanical switches. The sensor coil was connected with three different capacitors in parallel and two mechanical switches were in series between every two capacitors, which made the whole system have three resonant frequencies. The readout coil was magnetically coupled with the sensor coil to interrogate the sensor wirelessly. The circuit was simulated advanced design system (ADS) software, and the LC sensor system was mathematically analyzed by MATLAB. Results showed that the proposed LC sensing system could test three different capacitive sensors by detecting three different resonant frequencies. The sensitivity of sensors could be determined by the capacitance calculated from the detected resonant frequencies, and the resolution of capacitance was 0.1 PF and 0.2 PF when using the proposed sensor system in practical applications. To validate the proposed scheme, a PCB inductor and three variable capacitors were constructed with two mechanical switches to realize the desired system. Experimental results closely verified the simulation outputs.

QUBIC VII: The feedhorn-switch system of the technological demonstrator

We present the design, manufacturing and performance of the horn-switch system developed for the technological demonstrator of QUBIC (the Q&U Bolometric Interferometer for Cosmology). This system consists of 64 back-to-back dual-band (150 GHz and 220 GHz) corrugated feed-horns interposed with mechanical switches used to select desired baselines during the instrument self-calibration. We manufactured the horns in aluminum platelets milled by photo-chemical etching and mechanically tightened with screws. The switches are based on steel blades that open and close the waveguide between the back-to-back horns and are operated by miniaturized electromagnets. The measured electromagnetic performance of the feedhorns agrees with simulations. In particular we obtained a return loss around –20 dB up to 230 GHz and beam patterns in agreement with single-mode simulations down to –30 dB. The switches for this prototype were designed and built for the 150 GHz band. In this frequency range we find return and insertion losses consistent with expectations (< –25 dB and ∼ –0.1 dB, respectively) and an isolation larger than 70 dB. In this paper we also show the current development status of the feedhorn-switch system for the QUBIC full instrument, based on an array of 400 horn-switch assemblies.