Compound optimal control of harmonic drive considering hysteresis characteristic

Hysteresis behavior widely exists in the transmission process of harmonic drives. Eliminating the hysteresis effect is highly desired in the high-precision mechanical transmission, which results in challenges in the control design. This paper aims to improve the tracking accuracy of the motor-harmonic drive serial system. Firstly, a modified Bouc-Wen model based on uniform smooth approximating function is applied to describe the hysteresis behavior of the harmonic drive. By using coordinate transformation and accurate state feedback linearization, we then obtain the mathematical model of the serial system of the motor-harmonic drive. Finally, the reference trajectory is tracked by a compound optimal controller that is based on a linear quadratic regulator. Simulation results show that compared with the disturbance observer-based control (DOBC) using a linear observer, the new compound optimal controller in this paper presents a smoother control signal with the elimination of large amount of high-frequency oscillations. Furthermore, the relative error in the steady state tracking tends to approach to zero and no cyclic fluctuations appears. With the employing of optimal control, the output of the harmonic drive can trace more complex trajectory

Developmental Functions of miR156-Regulated \u3cem\u3eSQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL)\u3c/em\u3e Genes in \u3cem\u3eArabidopsis thaliana\u3c/em\u3e

Correct developmental timing is essential for plant fitness and reproductive success. Two important transitions in shoot development—the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition—are mediated by a group of genes targeted by miR156, SQUAMOSA PROMOTER BINDING PROTEIN (SBP) genes. To determine the developmental functions of these genes in Arabidopsis thaliana, we characterized their expression patterns, and their gain-of-function and loss-of-function phenotypes. Our results reveal that SBP-LIKE (SPL) genes in Arabidopsis can be divided into three functionally distinct groups: 1) SPL2, SPL9, SPL10, SPL11, SPL13 and SPL15 contribute to both the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition, with SPL9, SP13 and SPL15 being more important for these processes than SPL2, SPL10 and SPL11; 2) SPL3, SPL4 and SPL5 do not play a major role in vegetative phase change or floral induction, but promote the floral meristem identity transition; 3) SPL6 does not have a major function in shoot morphogenesis, but may be important for certain physiological processes. We also found that miR156-regulated SPL genes repress adventitious root development, providing an explanation for the observation that the capacity for adventitious root production declines as the shoot ages. miR156 is expressed at very high levels in young seedlings, and declines in abundance as the shoot develops. It completely blocks the expression of its SPL targets in the first two leaves of the rosette, and represses these genes to different degrees at later stages of development, primarily by promoting their translational repression. These results provide a framework for future studies of this multifunctional family of transcription factors, and offer new insights into the role of miR156 in Arabidopsis development

Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively

Numerical simulation of droplet coalescence based on the SPH method

In this paper, the smoothed particle hydrodynamics (SPH) method is employed in modeling and numerical simulation of droplet coalescence. Considering the effect of tangential force on boundary material, besides normal force, tangential force is also introduced in the continuum surface force (CSF) model. The formation of droplet, the coalescence processes of two droplets and three droplets are simulated by the modified CSF model. The validity of the modified model is verified from the aspects of the morphological change of the droplet, the smoothness of free surface and the conservation of the centroid of the system. Compared with finite element method, the results of the modified CSF model show that tangential force plays a crucial role in the CSF model when dealing with model boundary with curves and sharp angles

Fatigue Assessment of Explosive Bolts Considering Vibration of Fixtures

In order to comprehensively evaluate the safety and reliability of a missile, this paper gives a process of how to perform fatigue assessment for release devices—such as explosive bolts—considering road roughness during its carrying on different classes of roads. Firstly, displacement power spectral density (PSD) function is used to fit models of road surfaces of Class A, C, and E. Taking the surface models as simulations, multi-body dynamics analyses with code ADAMS are performed to obtain acceleration responses of different points on the missile. Loading these accelerations, the corresponding stress distribution of explosive bolts is achieved with FEM code ABAQUS. These loads are counted by rainflow method. Finally, constant life curves with different survival rates are employed to get the S-N curves at different stress ratios and stress concentration coefficients, and fatigue lives of explosive bolts are assessed based on the stress-life method. Afterward, the effect of pretension force on the vibration load is obtained. This paper provides a fatigue evaluation procedure for release devices, which is helpful to raise the reliability of release devices for both design and service procedures

Research on the cutting heat and wear of indexable inserts with different transition surfaces

Conference Name:3rd international Conference on Manufacturing Science and Engineering, ICMSE 2012. Conference Address: Xiamen, China. Time:March 27, 2012 - March 29, 2012.Fujian University of Technology; Xiamen University; Fuzhou University; Huaqiao University; University of WollongongThe transition surface of blade tip has direct impacts on the quality and lifespan of indexable inserts. For rectangle indexable inserts with four different transition surfaces, the paper analyzed how the transition surfaces put impacts on the cutting temperature and wear of inserts by finite element analysis software. The simulation results show that clearance angle of inserts has serious impacts on the blade performance. Besides, to control the clearance angle in an appropriate range, the cutting temperature and wear of insert would decrease accompanying with the rise of clearance angle. 漏 (2012) Trans Tech Publications

Fabrication of Heterogeneous Double-Ring-Like Structure Arrays by Combination of Colloidal Lithography and Controllable Dewetting

We report a novel technique for fabricating the heterogeneous double-ring-like structural array by colloidal lithography and two-step dewetting process. First, the 2D non-closed-packed (ncp) silica sphere arrays were obtained by lift-up lithography. Then, the ncp sphere array transferred onto the Rhodamine B (RB)@poly­(vinyl alcohol) (PVA) film was used for the mask during reactive ion etching (RIE) process. Sequentially, the substrate with RB@PVA ring-like structure arrays under the silica sphere was dip-coated from poly­(<i>N</i>-vinylcarbazole) (PVK) chloroform solution with certain concentration. Due to the presence of ordered 2D sphere arrays, the two-step dewetting behavior happened on top of the sphere and the silicon wafer between adjacent spheres, respectively. After removing the silica sphere arrays by hydrofluoric acid, the RB@PVA/PVK heterogeneous double-ring-like structure array was exhibited on the substrate. We characterized this particular structure by SEM, AFM, and fluorescence spectrum, which prove that both the inner RB@PVA ring and outer PVK ring are independent without any reaction. Accordingly, this method could be extended to other materials owing to its universality. These unique structural arrays have potential application in optoelectronic devices, surface photocatalysis, and surface enhanced Raman scattering (SERS)

Developmental Functions of miR156-Regulated <i>SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL)</i> Genes in <i>Arabidopsis thaliana</i>

<div><p>Correct developmental timing is essential for plant fitness and reproductive success. Two important transitions in shoot development—the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition—are mediated by a group of genes targeted by miR156, SQUAMOSA PROMOTER BINDING PROTEIN (SBP) genes. To determine the developmental functions of these genes in <i>Arabidopsis thaliana</i>, we characterized their expression patterns, and their gain-of-function and loss-of-function phenotypes. Our results reveal that <i>SBP-LIKE</i> (<i>SPL</i>) genes in <i>Arabidopsis</i> can be divided into three functionally distinct groups: 1) <i>SPL2</i>, <i>SPL9</i>, <i>SPL10</i>, <i>SPL11</i>, <i>SPL13</i> and <i>SPL15</i> contribute to both the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition, with <i>SPL9</i>, <i>SP13</i> and <i>SPL15</i> being more important for these processes than <i>SPL2</i>, <i>SPL10</i> and <i>SPL11</i>; 2) <i>SPL3</i>, <i>SPL4</i> and <i>SPL5</i> do not play a major role in vegetative phase change or floral induction, but promote the floral meristem identity transition; 3) <i>SPL6</i> does not have a major function in shoot morphogenesis, but may be important for certain physiological processes. We also found that miR156-regulated <i>SPL</i> genes repress adventitious root development, providing an explanation for the observation that the capacity for adventitious root production declines as the shoot ages. miR156 is expressed at very high levels in young seedlings, and declines in abundance as the shoot develops. It completely blocks the expression of its <i>SPL</i> targets in the first two leaves of the rosette, and represses these genes to different degrees at later stages of development, primarily by promoting their translational repression. These results provide a framework for future studies of this multifunctional family of transcription factors, and offer new insights into the role of miR156 in <i>Arabidopsis</i> development.</p></div

<i>spl</i> mutations reduce the expression of genes involved in floral induction and floral meristem identity.

<p>qRT-PCR analysis of transcripts isolated from shoot apices of 11 day-old plants. Values are normalized to Col, and represent the mean from 2 biological replicates ± SE.</p