Mechanical Spring Research Articles

Mechanical spring discharge-based multipillar triboelectric nanogenerator with enhanced power output

With the extensive use of small portable electronics in digital healthcare, the triboelectric nanogenerator (TENG), which can convert mechanical energy into electricity, has been developed for these portable electronics. However, the high mechanical input power for TENG performance improvement causes constant damage and excessive noise, which can make applying portable devices in daily life inconvenient. Nevertheless, the TENG electrical limitation, generating a low current output as nanoampere to microampere, still is not overcome. In this study, a portable multipillar TENG (PMP-TENG) with conductive springs can provide amplified output, developed mechanical characteristics simultaneously. When a moving electrode with a surface charge contacts the springs, the PMP-TENG continuously generates a high discharge output and increases the output frequency through the elastic force of the spring. In addition, the spring can prevent crack damage and harmful noise via shock absorption of the moving electrode. During the PMP-TENG operating mechanical input of 2.5 Hz, the average peak voltage, current is 165 V, 34 mA, respectively. The PMP-TENG is used to charge small electronics or power warning lights in portable devices during human motion, such as walking, running, and jumping, increasing its advantages.

Absolute displacement measurement using an inertial reference generated by linearised electromagnetic levitation

This paper proposes a novel passive absolute displacement measurement system (ADMS) utilising the electromagnetic levitation approach, instead of any mechanical spring. The most distinctive feature of the proposed ADMS is its measuring amplitude range of 30μm–1.2 mm with a lower frequency limit of 2 Hz. Consequently, a wider measuring bandwidth and higher measurement accuracy for absolute displacement signals can be realised without feedback/serve-type inertia sensors, which are usually expensive and vulnerable. Both features make the proposed system promising for of low-frequency measurement applications, such as precision vibration isolation of optical platforms in vibrational environments, anti-shake UAV platforms, monitoring of seismic wave signals, ship equipment protection and safety inspection of long-span bridges. First, the principles of the proposed ADMS are introduced. Subsequently, the measuring performance of the proposed ADMS is simulated and analysed. Finally, a prototype of the ADMS is constructed and tested. The experimental results confirm the validity of the proposed ADMS design and demonstrate its capability to measure the absolute displacement with a low-frequency and wider amplitude range.

Estimating the thermal effect in gPhoneX observations

Stationary relative gravimeters are used in variety of applications, mainly due to their high sampling rate which is more suitable for study of certain geodynamic effects than absolute gravimeters. Study of weak signals is almost exclusively in the domain of superconducting gravimeters, as they possess the highest accuracy and stability of all types of relative gravimeters. Possible alternative to superconducting gravimeters are portable earth tide metal spring gravimeters. Zero-length spring gravimeters (e.g. LCR instruments) are usually considered to be the most accurate mechanical spring gravimeters. However, compared to superconducting instruments they remain too unstable for long-term gravity monitoring. Main reason supporting this statement is related to instrument's sensitivity to temperature changes and temperature induced tilts. Gravity observations from the gPhoneX #108 gravimeter stationed at Hurbanovo gravimetric observatory were tested in order to confirm the correlation between the observed gravity changes and ambient temperature changes and provide a solution for correcting the gPhone data for influence of the ambient temperature changes. Paper also aims to serve as a guide for other operators to estimate a parameters required for the calculation of ambient temperature correction.

Assessment of harmonic mitigation performance of electric springs with different inverter topologies

Electric spring (ES) is a new technology inspired by the idea of realization a system that is equivalent to mechanical springs in terms of functionality within power systems. Electric springs are comprised from a DC voltage source, an inverter and an LC filter at the grid side. It can be used effectively in power systems to perform many functions such as voltage regulation, reactive power compensation, demand management and energy storage. On the other hand, due to the semiconductor elements in ES structure, it causes distortion on voltage and current waveforms. However, various control approaches have been proposed in the literature in order to prevent the aforementioned distortions. In this study, three different ESs has been modeled with the inverter topologies chosen from the frequently preferred once used in applications, namely Half-Bridge, Full-Bridge, and Neutral Point Clamped Multi-Level Inverter (NPC-MLI). The disruptive effects of electric springs with different inverter topologies on the grid and their performance in harmonic elimination have been examined through the results obtained from simulations realized in MATLAB/Simulink®.

Design and Robust Control of a Precise Torque Controllable Steering Module for Steer-by-Wire Systems

Steer-by-wire (SBW) system has been introduced to reduce the number of parts in a vehicle by eliminating the mechanical link between the steering wheel and the road wheel. Even though intensive research has been conducted on the SBW system, the performance of the actuator system that provides the desired steering feel still needs improvement. Therefore, this article presents a compact size torque controllable steering wheel module for the SBW system, where the actuator that provides the steering feel to the driver is modularized with the gear mechanism and the spring. The steering torque sensing mechanism is compactly integrated by placing the spring inside the gear mechanism. Thanks to the advantage in the torque measurement and control ability by the spring mechanism, high gear-ratio transmission can be employed in the proposed module, which can also address the low inherent mechanical impedance problem that may cause fail-safety issues in the SBW system. To enhance the impedance rendering performance of the proposed module, an internal model compensator which is composed of inertia and friction compensation is applied. The kinematics, statics, and dynamics of the proposed module are theoretically analyzed, and a model-based control algorithm is proposed based on this analysis result. Finally, the increase in the inherent impedance and the torque control performance of the proposed module are verified through experiments.

Principle and Control of Active Engine Mount Based on Magnetostrictive Actuator

Engine mount system affects the automobile NVH performance. Active mounts would achieve excellent vibration isolation and relative displacement control performance in a broad frequency bandwidth by outputting controlled force to the mounting system. The actuator and control method of the active mounts determine the system performance. In this paper, an active mount based on the smart material, i.e., Terfenol-D rod, is proposed, which mainly includes three parts: rubber spring, magnetostrictive actuator (MA), and hydraulic amplification mechanism (HAM). Dynamic model of the active mount is correspondingly established. A state feedback control method based on x-LMS (Least-Mean-Square) algorithm is proposed as well. Specifically, with the consideration of the unmeasurable state parameters in the active mounting system, an x-LMS state feedback controller with the system state as the reference signal is constructed by employing Sage-Husa Kalman filter to realize the state estimation of the active mounting system. Then a detailed analysis of the proposed control method is conducted, with deriving iterative formula of tap-weight vector. Sequentially, the problem of the dependence on the excitation signal in the x-LMS algorithm is addressed. The feasibility and capability of the proposed control method are verified and evaluated by simulation of a two-degree-of-freedom active mounting system.

Performance of a vibration isolator with sigmoidal force-deflection curve

This paper presents a theoretical insight on the performance of a vibration isolator consisting of a combination of linear mechanical springs arranged to achieve a specific form of geometric nonlinearity. In particular, positive and negative stiffness nonlinearities are combined to achieve a sigmoidal shape of the force-deflection curve, which is proven to be beneficial for vibration isolation purposes when the amplitude of vibration is relatively large. Such behaviour is fundamentally different from that of the classical quasi-zero-stiffness isolator, which presents a low dynamic stiffness at the equilibrium configuration and is thus effective for relatively low amplitude of vibration. The analytical findings are validated by numerical simulations, providing useful guidelines for the design of such isolators.

The Design of a Sub-Hz Magnetic-Suspended Geophone

A geophone usually behaves like a high-pass filter. The lower bound of its measuring bandwidth is often dependent on the dynamics of the interior mass-spring mechanical structure. Reducing the stiffness of the interior mechanical spring could be an effective way to improve the low-frequency performance of a geophone. Unfortunately, the resultant system may produce a nonlinear response and suffer a stability problem. In this article, a novel magnetic-suspended (MS) geophone is developed. It employs four well-designed concentric magnetic cylinders as the magnetic spring to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">suspend the proof-mass</i> , therein, the two middle magnetic cylinders produce a uniform magnetic flux around the induction coil. Moreover, two compensating coils are introduced to be independently driven by adjustable direct currents. They provide a low linear stiffness and can also compensate for the magnetic force errors of the magnetic spring caused by the manufacturing and assembly. Therefore, the sensitivity of the MS geophone is kept constant, and a sub-Hz natural frequency is obtained. A physical prototype has been built to evaluate the dynamic behaviors. The results have shown that the natural frequency and the sensitivity of the developed MS geophone are, respectively, 0.59 Hz and 412 V/(m/s). The proof-mass excursion is within the range of ±1.2 mm. The prototype may be used as a complementation of the commercial geophone for the applications of low-frequency active vibration isolation.

Experimental determination of the law of vibration of the improved jet mechanism of the sewing machine

The article presents the results of experimental determination of the oscillation law of the proposed additional conical spring mechanism of the effective reaction. The results of calculation of compressive strength and spring elasticity are presented. The change in the force acting on the reaction is determined by the electrostrain method and is based on its parameters.

A Rigid and Flexible Combined Finger Exoskeleton Design with Variable Curvature

Some hand exoskeletons have been used in the rehabilitation treatment of paralyzed patients caused by stroke and cerebral apoplexy as a result of research into hand exoskeletons. However, how to make the patient more comfortable to use and how to make the exoskeleton more precise are still key issues that need to be studied. Aiming at the motion law and skeletal characteristics of the human hand, this paper proposes a soft exoskeleton machine for hand rehabilitation training that combines rigidity and flexibility. Using a simplified two-layer sliding spring mechanism, the device combines the comfort and fit of a flexible device with the accurate kinematics of a rigid device. The mechanism requires only one degree of freedom to drive the normal flexion and expansion of the three finger joints. By changing the section thickness of the spring sheet to change its section moment of inertia, the bending effect of the mechanism is optimized to better fit the bending characteristics of the finger joints. To simplify the simulation of the mechanism, the method of the pseudo-rigid-body model is used to target the spring leaf’s nonlinear deformation, to achieve intuitively understandable kinematics. Finally, the accuracy of the design is demonstrated through simulation and prototype models.

Novel Force Estimation Method for Magnetic Lead Screw-Based RotLin Actuator

This article proposes a method to precisely estimate the load force of magnetic lead screw (MLS)-based series elastic actuators (SEAs) in real time. The elastic transmissions of MLS-based SEAs generally comprise permanent magnets (PMs). Owing to the magnetic pole distortion and the characteristic nonlinear force of PMs, conventional force estimation methods are less accurate for MLS-based actuators than for SEAs with mechanical springs. In the proposed method, to precisely estimate force of MLSs, the nonlinear force characteristic of an MLS is modeled with a sinusoidal force model, and the magnetic force hysteresis phenomenon is predicted based on Bouc–Wen-type hysteresis equations. Moreover, a method called the relative displacement normalization method is proposed to detect the magnetic pole distortion and to compensate for the related force estimation error. In addition, the proposed method is applied to a rotary-linear (RotLin) actuator, which is a novel MLS-based linear SEA. The force estimation accuracy is experimentally evaluated by comparison with existing methods. The results demonstrate that the root-mean-square error of the proposed method is less than that of the existing polynomial model by up to 81.2%. Finally, a force controller and a static force control system is designed with the proposed model to prove its feasibility.

Hydrochemical Characteristics and Genetic Mechanism of Geothermal Springs in the Aba Area, Western Sichuan Province, China

Geothermal resources have been a source of significant clean energy in the world. The Sichuan Province is famous for its abundant geothermal resources in China, especially in western Sichuan. The Aba area is a significant minority region in northwestern Sichuan with abundant geothermal resources. In this study, hydrochemical and D-O analyses were conducted on the eight collected geothermal springs to investigate the genetic mechanism of the geothermal resource in the Aba area. The exposed temperatures and pH values of the geothermal springs ranged from 23 °C to 48 °C and from 6.6 to 9.5, respectively. Based on the hydrochemical characteristics, the eight geothermal springs were classified into two types: class A and class B. The class A geothermal springs belonged to the hydrochemical type of Ca-Mg-HCO3-SO4 and Ca-Mg-HCO3 and were affected by the weathering and dissolution of carbonate and silicate. The class B hydrochemical type of geothermal spring was Na-HCO3, which was determined by the weathering and dissolution of evaporite and silicate. A Na-K-Mg triangle diagram revealed that the geothermal springs belonged to immature water. A chalcedony geothermometer indicated that the temperature of the class A shallow geothermal reservoir in the Aba area was 59.70–73.00 °C and 70.65–120.91 °C for class B. Silicon enthalpy approaches showed that the initial reservoir temperature for class A was 181.36–203.07 °C (mixed by 85.76–89.44% cold water) and 271.74–295.58 °C (mixed by 87.39–87.54% cold water) for class B. The recharge elevation of the geothermal spring was 3415–3495 m as calculated by the D-O isotopes. We have proposed these genetic models of the two typical geothermal springs. The achievements provide a vital reference for the further development of geothermal water and the sustainable utilization of geothermal resources in the Aba area.

Non-Hookean large elastic deformation in bulk crystalline metals

Crystalline metals can have large theoretical elastic strain limits. However, a macroscopic block of conventional crystalline metals practically suffers a very limited elastic deformation of <0.5% with a linear stress–strain relationship obeying Hooke’s law. Here, we report on the experimental observation of a large tensile elastic deformation with an elastic strain of >4.3% in a Cu-based single crystalline alloy at its bulk scale at room temperature. The large macroscopic elastic strain that originates from the reversible lattice strain of a single phase is demonstrated by in situ microstructure and neutron diffraction observations. Furthermore, the elastic reversible deformation, which is nonhysteretic and quasilinear, is associated with a pronounced elastic softening phenomenon. The increase in the stress gives rise to a reduced Young’s modulus, unlike the traditional Hooke’s law behaviour. The experimental discovery of a non-Hookean large elastic deformation offers the potential for the development of bulk crystalline metals as high-performance mechanical springs or for new applications via “elastic strain engineering.”

Presentation and Management of a Complex Orbital Apex Syndrome From Penetrating Mechanical Spring Hook: A Case Report

Our case report demonstrates the management of a unique penetrating orbital injury. The intraorbital foreign body was an approximately 22 cm long metal dishwasher spring hook lodged into the left orbital apex. An ophthalmological check-up a couple of weeks following the removal surgery discerned the patient had anunprecedented case of orbital apex syndrome. We present this unique case so physicians, medical students, and other emergency and medical professionals can learn about the diagnostic, surgical, and multidisciplinary management necessary to achieve a favorable clinical outcome.

Design, characterisation and validation of a haptic interface based on twisted string actuation.

This paper presents the design and experimental characterisation of a wrist haptic interface based on a twisted string actuator. The interface is designed for controlled actuation of wrist flexion/extension and is capable of rendering torque feedback through a rotary handle driven by the twisted string actuator and spring-loaded cable mechanisms. The interface was characterised to obtain its static and dynamic haptic feedback rendering capabilities. Compliance in the spring and actuation mechanism makes the interface suitable for smooth rendering of haptic feedback of large magnitudes due to the high motion transmission ratio of the twisted strings. Haptic virtual wall rendering capabilities are demonstrated.

Production and performance of a low temperature shape-memory actuator based on twisted-coiled spring mechanics

Demand for new types of actuators continues to grow, and novel approaches have been made possible by the advent of new materials and fabrication strategies. Self-powered actuators have attracted significant attention owing to their ability to be driven by elements in ambient environments. This type of actuator can be used in flexible strain sensors, artificial muscles, soft robotics, and smart breathing textiles. However, petrochemical-based polymers are generally environmentally unfriendly and cause ecological problems. The use of biodegradable polymers is one of the preferred solutions to ecological problems. Polylactic acid is a biodegradable and biocompatible polymer with a high potential. In this study, nanoclay reinforced polylactic acid/thermoplastic polyurethane was used as a precursor. The yarn that was produced was highly twisted. The twisted yarn was then shaped into a coiled structure via mandrel annealing. An apparatus was designed to investigate the thermal actuation behavior of twisted-coiled yarn in an isometric state. The blocked force and free stroke were calculated in an isometric state by using linear material equations. The thermal actuation behavior of the twisted-coiled yarn was also studied in the isotonic state. This precursor exhibited a considerable two-way shape-memory effect in a twisted-coiled structure. It also showed a significant reversible contraction stroke within the low temperature range. The theoretical stroke was determined using two different models: the force–stroke equation and spring mechanics. The theoretical results were compared with the experimental results, which revealed acceptable agreement between the theoretical and experimental values.

Design and Manufacturing of a Metal-Based Mechanical Metamaterial with Tunable Damping Properties.

In the present work, a novel concept for metallic metamaterials is presented, motivated by the creation of next-generation reversible damping systems that can be exposed to various environmental conditions. For this purpose, a unit cell is designed that consists of a parallel arrangement of a spring and snap-fit mechanism. The combination of the two concepts enables damping properties one order of magnitude higher than those of the constituting metal material. The spring element stores elastic energy while the snap-fit allows to absorb and dissipate energy and to reach a second stable state. Different configurations of single unit cells and connected cell assemblies are manufactured by laser powder bed fusion using Ti6Al4V powder. The dimensioning is supported by finite element modelling and the characteristic properties of the unit cells are studied in cyclic compression experiments. The metamaterial exhibits damping properties in the range of polymeric foams while retaining its higher environmental resistance. By variation of selected geometrical parameters, either bistable or self-recovering characteristics are achieved. Therefore, a metamaterial as an assembly of the described unit cells could offer a high potential as a structural element in future damping or energy storage systems operating at elevated temperatures and extreme environmental conditions.

WIELAND B44

Abstract Wieland B44 is a multi-alloy phosphor bronze containing 4% tin, 4% zinc and 4% lead. This makes it possible to achieve high mechanical strength and good spring properties. Wieland B44 exhibits excellent wear and corrosion resistance. It has good cold working and excellent machining properties. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance and wear resistance as well as heat treating and machining. Filing Code: Cu-933. Producer or source: Wieland-Werke AG.

On springtails (Hexapoda: Collembola): a morphofunctional study of the jumping apparatus

BackgroundSpringtails (Hexapoda: Collembola) are tiny organisms that lead a hidden life, mostly occuring deep in the soil and on leaf litter. They have a variety of interesting body morphology patterns, the most famous of which is the catapult-like structure that enables them to jump and flee from predators. This highly specialized jumping apparatus consists of a mobile furca, which when at rest fits into a trigger, "the retinaculum" on the ventral side of the abdomen. Despite the many studies that have attempted to investigate the jumping apparatus, the actual mechanisms involved in the jump, for example the way in which the furca is released by the retinaculum, how and where the mechanisms of spring and hydrostatic pressure originate, are still not properly understood. The morphology of the jumping apparatus of Orchesella cincta was investigated in detail using confocal laser scanning microscopy and MicroCT techniques for 3D reconstruction.ResultsThe morphology of O. cincta with both flexed and extended furca is analysed and described. The abdominal musculature involved in the jumping mechanism and relevant structures of the exoskeleton of retinaculum and furca are described in detail. With the data obtained in this study, hypotheses can be made about (1) where and how the spring and hydrostatic pressure mechanisms originate; (2) which muscles act on the extension and flexion of the furca; (3) which muscles act on the retinaculum and (4) how the retinaculum is released from the furca.ConclusionsThe comparative morphological study proved informative, and shows how springtail jumping involves mechanisms unique to this taxon. Hydrostatic pressure regulation possibly varies between animals with distinct segmentation, and those with fused segmentation. Interesting cuticular characters were revealed, such as basal plates and sclerites related to the construction of the spring mechanism. The present study establishes itself as a model option for future morphofunctional studies on springtail’s jumping. Analysis of videos and images using a high speed camera will be useful for understanding how the jump develops through take-off, aerial and landing phases.

Evaluation of the Stiffness Mechanism on the Performance of a Hinged Wave Energy Converter

Abstract This paper presents the numerical and experimental study of a new spring mechanism adapted to a cone-shaped point absorber wave energy converter (WEC). The WEC is intended to be hinged to a floating wind platform with a long arm to create a combined wind and wave harvesting concept. The main objective of the spring mechanism is to improve the platform by restoring moments against the wind thrust forces, generated by the wind turbine. However, the study is presented for the case where the WEC dynamics is investigated outside the platform and attached to a fixed frame, to validate the mathematical model of the WEC concept and study the effects of the spring mechanism on wave energy absorption. In addition, the impact on the power harvesting performance is investigated with and without spring mechanism scenarios and different sea states.