Spring Arms Research Articles

Stiffness estimation of planar spiral spring based on Gaussian process regression

Planar spiral spring is important for the dimensional miniaturisation of motor-based elastic actuators. However, when the stiffness calculation of the spring arm is based on simple beam bending theory, the results possess substantial errors compared with the stiffness obtained from finite-element analysis (FEA). It deems that the errors arise from the spiral length term in the calculation formula. Two Gaussian process regression models are trained to amend this term in the stiffness calculation of spring arm and complete spring. For the former, 216 spring arms’ data sets, including different spiral radiuses, pitches, wrap angles and the stiffness from FEA, are employed for training. The latter engages 180 double-arm springs’ data sets, including widths instead of wrap angles. The simulation of five spring arms and five planar spiral springs with arbitrary dimensional parameters verifies that the absolute values of errors between the predicted stiffness and the stiffness from FEA are reduced to be less than 0.5% and 2.8%, respectively. A planar spiral spring for a powered ankle–foot prosthesis is designed and manufactured to verify further, of which the predicted value possesses a 3.25% error compared with the measured stiffness. Therefore, the amendment based on the prediction of trained models is available.

Effects of the angle between the spring arm on spring characteristics on the single coiled torsion spring using Ti-Ni shape memory alloy wire.

We have been investigated one-coil torsion springs using shape memory alloy (SMA) wire for application to welfare equipment (for example, lower limb orthoses), because one-coil torsion springs using SMA wire have small size and large displacement. It is known that the spring properties of a torsion spring depend on the shape of the spring, and design calculation method for springs made of normal metals have already been established. However, SMA has different characteristics from normal metals, and it is difficult to apply conventional design calculation methods. Therefore, we fabricated several SMA torsion springs with different the angle between the spring arm and investigated the effects of shape of the spring on the spring characteristics of SMA torsion springs by spring characteristic tests and fatigue tests. The experimental results show that increasing the angle between the spring arm improves the fatigue life of the SMA torsion springs but the spring generating force decreased. On the other hand, the functional degradation characteristics are independent of the angle between the spring arms.

Poverty, Insecurity, and Climate Change Stare at the EU-AU Relations

The renewed relationship between the European Union (EU) and the African Union (AU) presents a platform for mutuality of benefits and responsibilities. Regional security is one area where both can learn based on recent and present experiences. The EU can learn from the AU from the post-Arab Spring arms proliferation, which led to internal conflicts, transborder crimes, and insurgency across Africa. The AU, on its part, can learn from the EU on civil governance, leadership, and transborder checks. The Regional Security Complex Theory aids our understanding of regional security. This paper examines some challenges confronting both regions and recommends panaceas of mutual benefits.

Modeling verification of an advanced torsional spring for tracked vehicle suspension in 2S1 vehicle model

In the article, the authors present an advanced model of hyperbolic torsion spring based on the Finite Element Method (FEM). This model takes into account the contact forces between the spring arms, which allows you to simulate its operation even in the case of a large twisting angle. On the basis of this FEM model, the spring stiffness characteristics were constructed. Based on this characteristics, the existing 2S1 track platform model has been rebuilt. In this model, a much higher mass of the body is allowed than in the original model. On the basis of the elastic spring model, parameters such as the static deflection of the suspension have also been determined, as well as its range of mobility compared to the original suspension based on torsion bars. In addition, spring deflection phases have been presented in terms of internal stresses, which are important for the strength analysis of the spring. The originality of the described solution lies in the unique design of the so-called a hyperbolic spring. This design has not been previously described in the literature.

Method to characterize a thermal diode in saturated steam atmosphere.

We present a novel measurement method for the characterization of thermal diodes in a saturated steam atmosphere. A measuring setup has been developed in which two pressure sensors are integrated. Using a developed analytical model, the heat flow, the volume flow, and the cracking pressure are determined from the measured absolute pressures and the pressure difference. The analytical model was verified using a flow through an orifice. We first calculated the volume flow through the orifice, with a diameter of 3 mm, using the Reader-Harris equation and then compared it to experimentally determined values. The experimentally determined values showed a discrepancy of 9%. With the measurement setup, we have characterized a check valve developed for magnetocaloric heat pumps, which has a thermally rectifying behavior. The developed check valve consists of three spring arms, which are radially attached to a valve disk. The heat flow through the check valve in the forward direction is 166 W for water, 239 W for ethanol, and 547 W for methanol at a temperature difference of 1 K. In the reverse direction, the heat flow is -0.03 W at a temperature difference of -1 K. For methanol, this corresponds to a rectification coefficient of more than 18 000.

Spiral spring electrostatic actuator for double-layer deformable mirror with continuous phase sheet

A new electrostatic actuator for a double-layer deformable mirror (DM) with continuous phase sheet is presented. The electrostatic actuator employs an upper electrode consisting of multiple Archimedean spiral spring arms supporting a small mass central attachment point and is capable of separating the parameters of actuation voltage, spring constant, and resonance. The feature reduces the complexity in the designing of a double-layer DM with continuous phase sheet, which is widely employed in the adaptive optics area of astronomy. The fabricated device has a diameter of 1250 μm with four single-crystal silicon spiral arms each having a length of 6030 μm, thickness of 15 μm, and width of 30 μm. The actuator was simulated and tested to have a resonant frequency above 2600 Hz and was simulated to be capable of reaching ∼5-μm displacement with a drive voltage of <30 V with an actuator–electrode separation of 15 μm, based on the performance parameter found experimentally.

A Novel Technique for Design of Ultra High Tunable Electrostatic Parallel Plate RF MEMS Variable Capacitor

This paper introduces a novel method for designing of low actuation voltage, high tuning ratio electrostatic parallel plate RF MEMS variable capacitors. It is feasible to achieve ultra-high tuning ratios way beyond 1.5:1 barrier, imposed by pull-in effect, by the proposed method. The proposed method is based on spring strengthening of the structure just before the unstable region. Spring strengthening could be realized by embedding some dimples on the spring arms with the precise height. These dimples shorten the spring length when achieved to the substrate. By the proposed method, as high tuning ratios as 7.5:1 is attainable by only considering four dimple sets. The required actuation voltage for this high tuning ratio is 14.33 V which is simply achievable on-chip by charge pump circuits. Brownian noise effect is also discussed and mechanical natural frequency of the structure is calculated.

Static Design and Finite Element Analysis of Innovative CFRP Transverse Leaf Spring

This paper describes the design and the numerical modelization of a novel transverse Carbon Fiber Reinforced Plastic (CFRP) leaf-spring prototype for a multilink suspension. The most significant innovation is in the functional integration where the leaf spring has been designed to work as spring, anti-roll bar, lower and longitudinal arms at the same time. In particular, the adopted work flow maintains a very close correlation between virtual simulations and experimental tests. Firstly, several tests have been conducted on the CFRP specimen to characterize the material property. Secondly, a virtual card fitting has been carried out in order to set up the leaf-spring Finite Element (FE) model using CRASURV formulation as material law and RADIOSS as solver. Finally, extensive tests have been done on the manufactured component for validation. The results obtained show a good agreement between virtual simulation and experimental tests. Moreover, this solution enabled the suspension to reduce about 75% of the total mass without losing performance.

High Figure of Merit Nonlinear Microelectromagnetic Energy Harvesters for Wideband Applications

We report a new approach for designing high-performance microelectromechanical system (MEMS) electromagnetic energy harvesting devices, which can operate at low frequency (<;1 kHz) over the ultrawide bandwidth of 60-80 Hz. The output from the devices is increased significantly at a low optimized load and this overall enhancement in performances is benchmarked using a power integral (Pf) figure-of-merit. The experimental results show that the efficient nonlinear designs produce large Pf values, giving rise to one of the highest normalized Pf densities among the reported MEMS scale nonlinear energy harvesting devices. This improvement is achieved by suitably designing the nonlinear spring architectures, where the nonlinearity arises from the stretching strain of the specifically designed fixed-fixed configured spring arms under large deflections and gives rise to wideband output response. Different fundamental modes of the mechanical structures are brought relatively close, which further widens the power-frequency response by topologically varying the spring architectures and by realizing the same using the thin silicon-on-insulator substrate using MEMS processing technology. In addition, we have used the magnet as proof mass to increase the output in contrary to conventional approach of using the coil as the proof mass in micro-electromagnetic energy harvesters. The high performance obtained from the MEMS energy harvesters with integrated double layer micro-coil is compared with the same using wire wound copper coil. The experimentally obtained results are qualitatively explained by using a finite-element analysis of the designed structures.

Nonlinear Energy Harvesting Using Electromagnetic Transduction for Wide Bandwidth

We report the relative performances of monostable and bistable miniaturized electromagnetic energy harvesters (EMEHs) using micromachined fiberglass-epoxy spring structures. Monostable nonlinearity is realized in our device using the specially designed spring arms, whereas bistable nonlinearity is introduced through the interactions between repulsively oriented magnets. For devices of similar size, the monostable electromagnetic harvester generates larger output power compared to the bistable system under the same mechanical input. This is due to the additional damping provided by the strong bistable force, which also restricts the bandwidth widening of the bistable device compared to that of the monostable energy harvester. However, as the bistable force changes the linear stiffness of the system as well, the overall frequency response shifts toward the low-frequency region. Hence, low-frequency, wideband harvesting can be obtained in bistable devices compared to monostable devices of the same mechanical dimensions.

A nonlinear stretching based electromagnetic energy harvester on FR4 for wideband operation

We report a nonlinear stretching-based electromagnetic energy harvester using FR4 as a vibrating spring material due to its low Young’s modulus. We show analytically that the nonlinearity is caused by the stretching, in addition to the bending, of the specially designed spring arms; this gives rise to a wider half-power bandwidth of 10 Hz at 1 g acceleration, which is almost 5 times higher than that of a comparable linear counterpart. The output spectra show the first reported experimental evidence of a symmetry broken nonlinear secondary peak in a single potential well system at frequencies close to the nonlinear jump frequency, which may appear to be due to the dynamic symmetry breaking of the oscillator or to the inherent asymmetry of the built prototype. The presence of this secondary peak is useful in generating a significant amount of power compared to the symmetric states, producing ∼3 times more power at the secondary peak than the nearby symmetric states. 110% of the peak power obtained for 0.5 g acceleration is achieved at the secondary peak during the frequency up-sweep. The experimental results are compared with a deterministic numerical model based on the Duffing oscillator, and we include a qualitative discussion on the influence of noise in an experimental energy harvesting system.

Analysis of Nonlinear Spring Arm for Improved Performance of Vibrational Energy Harvesting Devices

Recently, a number of attempts have been made to increase the operational bandwidth of the energy harvesting devices. Nonlinear mechanisms are one of them. In this paper, we report design and analytical formulation of stretching strain of an electromagnetic energy harvester on FR4 material under large deformation of the spring arms. It is found that nonlinearity has an inverse square dependence on thickness of the arms. Numerical solution of a monostable Duffing oscillator that governs the dynamics of such a large deformed nonlinear energy harvester showed that with decrease of load resistance, the average power output increases, where the output response depends strongly on the input force. For small input acceleration, the desired large amplitude vibration does not come into play and the response becomes linear. However, for higher input acceleration nonlinearity appears and the operational bandwidth increases, at the same time, output power level also increases.

Diversity ofSalmonellain biofilms and water in a headwater ecosystem

The diversity of Salmonella was analysed in biofilm and water samples from the spring and slough arms of Spring Lake, the headwaters of the San Marcos River, Texas, during the drought of 2011, with only one potential run-off event at the beginning of the study. Salmonellae were detected in semiselective enrichment cultures by end-point PCR during the entire sampling period of (11 sampling events during 2months). From the spring arm site, 73% of the biofilms and 41% of the water samples were positive for salmonellae, while only 9% of the biofilms and 23% of the water samples were positive from the slough arm site. Salmonellae could be isolated from all positive samples, with higher diversity in biofilms compared with water samples and more strains obtained from the spring arm than from the slough arm. Differences between sites were generally caused by less frequently detected isolates, while the majority of isolates that were present in both biofilms and water from both sites was represented by three strains only. Quantification attempts by quantitative PCR directly in samples without prior enrichment did not result in a reliable detection of salmonellae, suggesting that numbers in all samples were below the detection limit.

Spectral imaging characterization of quartz MOEM tunable Fabry-Perot filter

Recently, prototype MOEM tunable Fabry-Perot filters operating from 400 to 800 nm were fabricated under a program to design miniature hyperspectral imagers operating from the visible to the longwave infrared. The filter design uses two semitransparent 30 nm thick silver-film mirrors, one fixed and the other moving, on a low-cost thin commercial quartz substrate. The moving mirror is supported by three leaf spring arms, which are fabricated by wet etching of the quartz substrate. The tuning of the transmitted wavelength of light from the filter is achieved by electrostatically actuating the moving mirror to vary the distance between the two mirrors. The size of the device is 18×24 mm2. The fixed part has a 6 mm diameter mirror and three electrodes to apply voltages, and the moving mirror is used as a ground electrode. Au bumps deposited on both parts control the initial air gap distance, and an Au-Au bonding is used to bond the two parts together. The spectral imaging performance of the MOEM filter is characterized using a spectrally tunable source and a CCD camera with suitable optics. The authors present a brief description of the filter, its characteristics, spectral imaging characterization experiment and results.

Hydrological prognosis for high and low waters of the river of Rasina

The river of Rasina arises on the slopes of the mountains of Goc and Zeljin, from spring arms of the Velika and Burmanska river. After the flow of 92.3 km, it flows into the river of Zapadna Morava 5 km downstream Krusevac, 134 meters above sea level. This work analyzes the frequency of occurrences of high and low waters, as well as their influence on the regime of Rasina and water management problems in its basin. .

Wafer-transfer robot for use in ultrahigh vacuum

A polar coordinate wafer-transfer robot has been developed that enables thin-film manufacturing to be done in an ultrahigh vacuum. This robot features a frictionless spring structure that operates in a vacuum and is magnetically driven by a motor in the atmosphere (Nikkei Mechanical 1993.5.17). The spring arms are made of sheet springs and rigid plates and were optimized by simulation using the finite element method. All moving parts in the vacuum environment have a minimum of two bearings. As a result, a repeat position precision of 0.2 mm or less was able to be achieved in the atmosphere. Also, a maximum transfer distance of 800 mm and a transfer speed of 400 mm/s were achieved at a pressure of 10−7 Pa. After operation in a clean room at atmospheric pressure, only three particles above 0.1 μm in size were observed. Using this wafer-transfer robot, the area needed for film manufacturing in a multichamber ultrahigh vacuum can be reduced about 30% compared with using a conventional linear-magnet–coupling wafer-transfer robot.

Single note sostenuto for the upright piano

In the upright piano action, the wire protruding up from the damper lever leaning or biased towards the string contacts and slides back to and forth along a pin fixed and protruding straight out from the hammer spring rail towards the string. On the sostenuto rod, attached and moveable horizontally on top of the hammer spring rail, is fixed a thin wire arm with a hooked end extending straight towards the space between the strings, reaching just long enough to clear the damper lever wire as it travels horizontally back and forth when the damper is on the string. When the damper moves off the string after depression of the key, the damper wire slides back along the side of pin in hammer spring rail and is hooked by wire arm on sostenuto rod when it moves horizontally towards the damper wire clamping it securely back, even after release of the depressed key. So long as the sostenuto rod is held in that position, thus allowing the string, after being struck by hammer to continue to vibrate sustaining the tone. A plurality of such sostenuto wire spring arms and hammer spring rail pins for a plurality of damper levers are fixed to the transversely extending hammer spring rail and sostenuto rod which moves the spring arms in unison toward the damper lever wires catching those that are off the string against the hammer spring rail pins and ignoring those that are on the strings allowing all of the piano action to function normally by moving the spring arms beyond the reach of the damper lever wires.

Electromagnetic acoustic transducer with its air gap established at assembly by counteracting springs

A tone generator having a diaphragm and an electromagnet for vibrating the diaphragm to produce sound, the bobbin of the electromagnet being held in a fixed, predetermined relation to the diaphragm and connected to the retaining ring which holds the diaphragm by resilient spring arms that are stressed automatically by assembly of the tone generator to clamp the diaphragm, the pole piece of the electromagnet being held by flexible and resilient supports that are flexed automatically to retain the pole piece when the generator is assembled and to hold an end of the pole piece precisely spaced with respect to the diaphragm.