High Reduction Ratio Research Articles

Efficiency Analysis of a Cycloid Reducer Considering Tolerance

High precision reducers such as cycloid reducers have been used to meet the mechanical system requirements of industrial robots for advantages such as: high reduction ratio, large torque capability, and high efficiency. Although efficiency of reducers is one of important performances, there are few studies on efficiency of a cycloid reducer considering its tolerance. This paper presents efficiency analysis of a cycloid reducer with tolerance using the approximate force distribution of an ideal cycloid reducer. First, we present an FE analysis of a cycloid reducer with tolerances. Then, we approximate force distribution of the cycloid reducer with tolerance using an ideal cycloid reducer without any tolerance. The approximated force distribution of the cycloid reducer can be easily calculated using the theory of the ideal cycloid reducer. Finally, efficiency analysis of the cycloid reducer is performed using the approximate force distribution. Tolerance has great effect on efficiency on a cycloid reducer.

Improvement of positive position feedback controller for suppressing compressor blade oscillations

Positive position feedback is an important control vibration algorithm as it exhibits very high reduction ratios but at a specific bandwidth. Out of this bandwidth, there exist two peaks with high amplitudes, which is considered the major drawback of this controller. In this paper, we are going to improve its performance by suppressing the two peaks to acceptable levels. That can be done by coupling additional nonlinear saturation controllers (NSC) with the main system to impose a V-curve at each one of the peaks. The V-curves positions are controlled by adjusting the natural frequencies of the NSCs. The overall behaviors of the system with and without control are clarified by the extracted equations via the multiple time scales analysis. Time history and different response curves of the controlled system are included for showing the controller effect. Eventually, validation curves and comparison with previously work are included.

Low-loss gears precision planetary gearboxes: reduction of the load dependent power losses and efficiency estimation through a hybrid analytical-numerical optimization tool

In the field of robotics, extremely accurate gearboxes are mandatory in order to ensure the adequate precision required by the automatic processes. For these applications, planetary gearboxes represent one of the most attractive solutions because they ensure high reduction ratios in a compact solution. However, their compactness and high power density, imply some thermal limitations. In order to overcome this problem, new gear designs have been studied by a hybrid analytical-numerical approach in order to reduce the power dissipation and, consequently, the operating temperatures. The efficiency increase is obtained mainly by a reduction of the module of the gears. This, together with other modifications of the tooth form (pressure angle, profile shift, etc.), allows to reduce the relative sliding between the tooth flanks that causes the power loss maintaining at the same time an adequate load carrying capacity. Low-loss gears have already been studied by other authors on bigger gears. Furthermore, by means of dedicated CFD simulations performed with an especially developed tool based on the open-source code OpenFOAM®, it has been shown that the sliding optimized design has a positive impact also on the churning power losses. The global winning in terms of reduction of the gear meshing power losses can be assessed in about 50%, depending on the reduction ratio. The new design has been validated by means of experimental tests performed in the internal laboratory of the company. The results have fully validated both the numerical approach and the new design.

Design and fabrication of an automatic dual axis solar tracker by using LDR sensors

Due to the rotation of the earth in an orbit, direction of the Sun changes relatively. This paper represents a setup, which is fabricated to minimize the angle of incidence between incoming light from Sun and a flat photovoltaic (PV) panel to increase the intensity of the light received. It increases the power generated by an installed power generating unit. This setup consists of a mechanical mechanism to tilt the flat PV panel towards the Sun. This mechanism is derived by DC motors having a high reduction ratio. Voltage supplies to these motors are controlled by the LDR (Light Dependent Registers) sensors by the means of electronic circuits. The energy consumed by the tracking system is very less. The cost of the mechanical parts and electronic components are very less. The Microprocessor is not used in this setup. Hence it does not require programming and computer interface. Not any geological data are required, because LDRs work on the differential of the light intensity at the both ends of the plate. The motive of the work is to fabricate a solar tracker at a very low cost.Keywords: Solar Tracker, LDR, Photovoltaic (PV) cell, Dual Axis, Solar Collectors, Solar power plant

Characteristics of cases needing advanced treatment for intractable Posner\u2013Schlossman syndrome

BackgroundIn Posner-Schlossman syndrome (PSS), which is characterized by recurrent unilateral attacks of ocular hypertension. Surgical treatment is sometimes necessary because intraocular pressure (IOP) cannot be controlled with anti-glaucoma medications. To identify the clinical features of Posner–Schlossman syndrome (PSS) indicative of the need for intraocular pressure (IOP)-controlling surgery.MethodsThis study was a retrospective case-series analysis of the clinical charts of 33 patients diagnosed with PSS, who underwent surgery to control IOP or received medication only. Various clinical factors were compared between the surgical and medication groups.ResultsThe surgical group had a higher corneal endothelial cell (CEC) density loss (p < 0.05), higher maximum IOP (p < 0.01), greater visual field loss (p < 0.01) and higher positive number for cytomegalovirus (CMV) (p < 0.001) than the non-surgical group. Eighteen of the 33 patients had a high CEC reduction ratio. Of these 18, 16 required glaucoma surgery.ConclusionsPSS patients with a higher CEC reduction ratio, higher maximum IOP, greater visual field loss and higher positive number for CMV in the aqueous humor tended to be more likely to require progressive treatment, such as glaucoma surgery.

Hysteresis curve analysis of a cycloid reducer using non-linear spring with a dead zone

Cycloid reducers are widely used for high-precision industrial instruments and robots because of many advantages: high efficiency, high stiffness and a high reduction ratio in a compact size. Nevertheless, the few studies that have investigated the hysteresis characteristics of a cycloid reducer used a time-consuming iterative procedure. This paper presents an efficient FE analysis procedure for the hysteresis characteristics of a cycloid reducer using a nonlinear spring with a dead zone. First, we introduced a cycloid reducer and performed a kinematic analysis of the cycloid disk with tolerance. Next, connecting elements of the cycloid reducer such as the input bearing, pin-roller and output roller were approximated as nonlinear springs with a dead zone. In particular, the dead zone for the nonlinear springs was introduced to represent the clearance of each connecting element. Then, a full FE model of the cycloid reducer was built incorporating the nonlinear springs, and the hysteresis characteristic of the cycloid reducer was directly evaluated at one time so as to significantly save its analysis effort and time. Results showed that tolerance had a great effect on torque and the torsional angle relationship of the cycloid reducer. such as lost motion, back lash and torsional rigidity.

Optimization of Planetary Gear Box for High reduction ratio

Optimization of Planetary Gear Box for High reduction ratio

Design and realization of a novel magnetic nutation drive for industry robotic wrist reducer

PurposeThe purpose of this research is to achieve a novel magnetic nutation drive for an industry robotic wrist reducer.Design/methodology/approachA novel magnetic nutation drive is proposed, and the structure and principle of the designed magnetic nutation drive are described in this study. Three-dimensional finite element analysis is used to compute the magnetic and torque of the magnetic nutation drive. Furthermore, a prototype of this novel magnetic nutation drive device is developed with 3D printing technology and tested to verify the feasibility of the proposed structure and principle.FindingsThe simulation and experimental results indicated that the proposed magnetic nutation drive device could meet the desired specifications, and that this novel magnetic nutation drive device successfully realized the non-contact transmission ratio of 105:1 required for a robotic wrist reducer.Practical implicationsThis novel magnetic nutation drive is low-cost and easy to make and use, and which provides the non-contact transmission ratio of 105:1 required for a robotic wrist reducer.Originality/valueFor the first time, this research applies the permanent magnet drive technology to nutation drive and puts forward a new non-contact nutation drive mode. The novel drive mode can solve some problems of the traditional mechanical contact nutation drive, such as vibration, friction loss, mechanical fatigue and necessity of lubrication. The proposed non-contact nutation drive device can achieve a high reduction ratio with compact structure and can be suitable for industry application.

A fast feature selection approach based on extreme learning machine and coefficient of variation

Feature selection is the method of reducing the size of data without degrading their accuracy. In this study, we propose a novel feature selection approach, based on extreme learning machines (ELMs) and the coefficient of variation (CV). In the proposed approach, the most relevant features are identified by ranking each feature with the coefficient obtained through ELM divided by CV. The achieved accuracies and computational costs, obtained with the use of features selected via the proposed approach in 9 classification and 26 regression benchmark data sets, were compared to those obtained with all features, as well as those obtained with the features selected by a wrapper and a filtering method. The achieved accuracy values obtained with the proposed approach were generally higher than when using all features. Furthermore, high feature reduction ratios were obtained with the proposed approach, including the achieved feature reduction ratios in epilepsy, liver, EMG, shuttle, and abalone. Stock data sets were 90.48%, 90%, 70.59%, 66.67%, 75%, and 77.78%, respectively. This approach is an extremely fast process that is independent of the employed machine-learning methods.

DESIGN AND ANALYSIS OF A THREE-STAGE CYCLOIDAL PLANETARY GEAR DRIVE FOR HIGH REDUCTION RATIO

A new compact design of three-stage differential cycloidal planetary gear drive based on the concept of the so-called RV-reducer is proposed for high reduction ratio. The aim of the paper is to explore the structural and the loading characteristics of this new design. The drive consists of an involute stage and The reduction ratio of this drive type can be positive or negative depending on the tooth numbers of the gears. The relation of transmitted torques onto each component are derived based on the relations of torque and power equilibrium. The loaded tooth contact analysis of the drive is also developed based on the influence coefficients method. The influence of the two mechanism types and the arrangement of the cranks on the shared loads and contact stress acting on multiple tooth-pairs as well as the transmitted torques are analyzed and discussed in the paper.

THE ENGINEERING DESIGN AND TRANSMISSION EFFICIENCY VERIFICATION OF HELICAL SPUR GEAR TRANSMISSION WITH A SINGLE GEAR PAIR

The transmission efficiency of a gear reducer (ηT) can be expressed as ηT = ηm × ηb × ηs, where ηm is the meshing efficiency of gear pairs, ηb is the efficiency of bearings, and ηs is efficiency of oil seals. Based on the research of Hsieh, et al., the meshing efficiencies of a helical spur gear pair (4, 77) are between 96.13 and 99.20%. The purpose of this article is to analyze the theoretical transmission efficiencies of non-standard helical spur gear pair and verify the theorem. According to the gear data, the theoretical transmission efficiencies are calculated to be 90.13–97.85%. And its test values of transmission efficiencies are between 82.3 and 91.9% (acceptable values). There are only 5.39–14.14% errors between these two values. This manuscript verifies that a helical spur gear pair can have a high reduction ratio (20–30) and acceptable real transmission efficiencies.

Concentration of Skim Milk by a Cascade Comprised of Ultrafiltration and Nanofiltration: Investigation of the Nanofiltration of Skim Milk Ultrafiltration Permeate

In order to reach a high volume reduction ratio (VRR) prior to drying of skim milk, a membrane cascade comprising of an ultrafiltration (UF) coupled with a nanofiltration (NF) can be applied. The present study investigated the impact of processing (filtration temperature, transmembrane pressure (TMP)) and product (feed pH) parameters on the NF of skim milk UF permeate. It could be shown that a low filtration temperature of 10 °C is more advantageous in terms of flux stability and rejection of the solute fraction as compared to higher filtration temperatures up to 45 °C. The solution pH did not affect permeate flux and lactose retention. However, in order to avoid calcium losses, it is more favorable to conduct the concentration at a pH of 6.8 instead of at a lower pH of 5. The application of a higher TMP (up to 4 MPa) enhances permeate flux and VRR as well as solute rejection during concentration of UF permeate. It was also shown that the retention of solutes decreases towards the end of the concentration process. As a consequence, the achievement of high final VRR must be weighed against increased product losses at the end.

Performance evaluation of the novel multi-shaft mill using DEM modelling

Comminution is well known to be an inefficient process and a large consumer of energy globally, giving rise to the development of novel comminution devices trying to exploit this opportunity. A multi-shaft mill, considered to be a novel comminution device, combines a series of rotating shafts with attached flingers which impact gravity fed material. The mill offers positive benefits in terms of plant footprint, high reduction ratio, high throughput and potential benefits through ore specific circuit integration. A process performance evaluation was conducted by surveying the mill along with using Discrete Element Method (DEM) modelling. The survey proved the mills ability to continuously sustain operation and product size for two different ore types under various configurations. The DEM predicted that gravity fed material entering the multi-shaft mill, with 50% of particles accelerated to a velocity higher than 184km/h and 10% higher than 299km/h. These velocities are converted to comminution energy through collisions with liners or particle-particle interactions. Each particle is subject to more than 24 impacts per second, greater than the critical breakage strength of a particle (0.01kWh/t), leading to potential efficient comminution. Significant numbers of collisions were simulated in the mill alongside significant breakage being recorded through the surveying of the mill, leading to a reasonable comparison of product size distributions from the simulated adsorbed collision energies compared to the survey data. Using this baseline of the mills performance evaluation methodology further simulation work will aim to better quantify the breakage environment through a full-scale simulation run in parallel with future proposed survey work which will address wear rates and tailored operating conditions for specific ore types.

Twinning-detwinning assisted reversible plasticity in thin magnesium wires prepared by one-step direct extrusion

The present study examines the micromechanisms of plastic deformation in magnesium wires with diameters of 250μm, which were prepared by one-step direct extrusion with a high reduction ratio of 576:1 at a temperature of 577K. It is shown that small wire diameter combined with appropriate microstructure (grain size 14±2μm and strong texture) can yield convenient mechanical properties even in pure Mg. Reversible bending plasticity is achieved by abundant 101̅2 twinning-detwinning of selected variants in the compression zone and moderate dislocation activity in the tensile zone of bended wires. The 101̅2 twinning during bending is facilitated by the medium grain size and by the strong texture with the c-axis of grains roughly perpendicular to the extrusion direction. Intense or repeated plastic bending of wires results in twinning-induced grain refinement in the compression zone. Tensile tests conducted at room temperature and at strain rates of 10−3 and 10−1s−1 reveal maximum true stresses of 198±2 and 246±4MPa and ductility values of 10 and 8%, respectively. In contrast with bending, tensile deformation of wires almost exclusively includes dislocation mechanisms, and a minor contribution of any twinning mode is observed.

Lost motion analysis of one stage cycloid reducer considering tolerances

Cycloid reducers have a high reduction ratio, high efficiency, high stiffness and are a compact size, compared to conventional reducer mechanisms, so that they are attractive candidates for limited space and precision applications such as industrial robots and cars. However, the integrated performance of torsional stiffness and backlash or lost motion has not been studied yet. This paper investigates the lost motion of a cycloid reducer combining FE and kinematic analyses. First, we introduce the cycloid reducer and its hysteresis curve. Next, a kinematic analysis of the cycloid reducer is performed considering tolerance. Then, an iterative FE analysis of the lost motion of the cycloid reducer is performed combining the results of the kinematic analysis. We conclude that the lost motion of the cycloid reducer depends on not only its torsional stiffness but also its tolerance.

An alpha particle detector based on a GPS mosaic scintillator plate for continuous air monitoring in plutonium handling facilities

An alpha particle detector was developed for continuous air monitoring of radioactive contamination in working chambers at plutonium handling facilities. A 5-cm-square Gd2Si2O7:Ce (cerium-doped gadolinium pyro-silicate, GPS:Ce) mosaic scintillator plate for alpha particle measurements was fabricated from GPS single-crystal grains of around 550 μm diameter; the GPS grains were made of a GPS polycrystalline body grown using a top seeded solution method. The scintillator layer thickness was approximately 100 μm. The surface filling rate of the GPS grains was ca. 62%. To suppress the influence of non-uniformity of pulse heights of a photomultiplier tube, a central part of ∅ 40 mm of a 76-mm-diameter photomultiplier tube was used. In addition, 3 mm thick high-transmission glass was used as a substrate of the scintillator plate. The detector achieved energy resolution of 13% for 5.5 MeV alpha particles, detection efficiency of 61% and a radon progeny nuclide reduction ratio of 64.5%. A new alpha particle detector was developed to achieve a high radon progeny nuclide reduction ratio approaching that of a silicon semiconductor detector, with high resistance to electromagnetic noise and corrosion.

Investigation of beam steering performances in rotation Risley-prism scanner.

Rotation Risley-prism scanner appears to be the most promising solution to high-accuracy beam scanning and target tracking. In the paper, some important issues crucial to the function implementation are thoroughly investigated. First the forming law of scan blind zone relative to double-prism structural parameters is explored by a quantitative analysis method. Then the nonlinear relationship between the rotation speeds of double prisms and the change rate of beam deviation angle is presented, and the beam scan singularity is indicated as an essential factor that confines the beam scan region. Finally, the high-accuracy radial scan theory is verified to illustrate the important application owing to the high reduction ratio from the rotation angles of double prisms to the deviation angles of the emergent beam. The research not only reveals the inner mechanisms of the Risley-prism beam scanning in principle, but also provide a foundation for the nonlinear control of various beam scan modes.

Refining sugarcane juice by an integrated membrane process: Filtration behavior of polymeric membrane at high temperature

Application of membrane filtration to sugarcane juice refining is appealing because it can eliminate the usage of chemicals, achieve continuous and automated production, as well as produce superior quality of juice. However, some technical problems, such as low permeate flux, high sucrose loss in membrane retentate and serious membrane fouling, are impeding this technological upgrading in sugar industry. In this work, an integrated membrane process consisting of a tubular loose ultrafiltration (UF), a spiral-wound tight UF and a spiral-wound NF was developed to refine the raw sugarcane juice at pilot-plant scale. With a super high volume reduction ratio (VRR) of 20, the loose UF was able to be operated at a flux from 30 to 70Lm−2h−1, and the tight UF could run at a flux from 10 to 40Lm−2h−1; at the same time, the color removal kept more than 95%. Moreover, diafiltration operation could recover most of sugar in the UF concentrates, leading to a high sucrose recovery of up to 98% in two-stage UF. A novel cascade diafiltration mode was proposed to save water by 25% compared with the separated diafiltration. Mathematical models could well predict the diafiltration efficiency for the loose UF but not for the tight UF. Permeate flux of the loose UF was dominated by membrane fouling while for the tight UF, osmotic pressure played a more important role in the flux decline. With a suitable cleaning strategy, the performance of this integrated membrane process can be nearly regenerated although the temperature jump between filtration and cleaning (60–30°C) might result in some foulants accumulating in the membrane system. These results would serve as a valuable guide for process design and practical operation in subsequent industrial application.

Impact of Protein Removal by an Upstream Ultrafiltration on the Reverse Osmosis of Skim Milk and Sweet Whey

AbstractConcentration of milk and whey by ultrafiltration and reverse osmosis (RO) in cascade mode is an amendment of evaporation for high volume reduction ratios (VRR) prior to drying. This study investigated the impact of a prior protein removal and the transmembrane pressure (TMP) on the RO stage, compared to skim milk and sweet whey. It could be found that removal of the protein fraction of both skim milk and sweet whey improved the efficiency of the RO. An upstream ultrafiltration resulted in higher VRR as well as an increased permeate flux.

クラウン減速機の精度向上のための歯形の設計

Generally, low backlash mechanisms are required for robot joints to perform tasks accurately, so we are proposing a new concept of a low backlash reducer using precessing crown gears. We call it the crown reducer. The features of this reducer are low backlash, high reduction ratio and ease of downsizing which we believe will contribute to the design of small mechanisms such as finger joints of robot hands. This paper describes a design of tooth profile for improvement of accurate motion. Firstly, we propose the clearance of tooth profile for stator gear to avoid increasing input torque. Secondary, we change design of the rotor gear with coaxial double circular gear to single circular gear for reduction of manufacturing cost. Finally, we discuss the effect using manufactured prototype reducers.