scholarly journals Optimal Controller Design for Ultra-Precision Fast-Actuation Cutting Systems

Micromachines ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 33
Author(s):  
Fei Ding ◽  
Xichun Luo ◽  
Duo Li ◽  
Zheng Qiao ◽  
Bo Wang
Keyword(s):  
Controller Design ◽  
Structural Parameters ◽  
Point Of View ◽  
Design Stage ◽  
Controller Tuning ◽  
Positioning Errors ◽  
Ultra Precision ◽  
Bearing Stiffness ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping

Fast-actuation cutting systems are in high demand for machining of freeform optical parts. Design of such motion systems requires good balance between structural hardware and controller design. However, the controller tuning process is mostly based on human experience, and it is not feasible to predict positioning performance during the design stage. In this paper, a deterministic controller design approach is adopted to preclude the uncertainty associated with controller tuning, which results in a control law minimizing positioning errors based on plant and disturbance models. Then, the influences of mechanical parameters such as mass, damping, and stiffness are revealed within the closed-loop framework. The positioning error was reduced from 1.19 nm RMS to 0.68 nm RMS with the new controller. Under the measured disturbance conditions, the optimal bearing stiffness and damping coefficient are 1.1×105 N/m and 237.7 N/(m·s−1), respectively. We also found that greater moving inertia helps to reduce all disturbances at high frequencies, in agreement with the positioning experiments. A quantitative understanding of how plant structural parameters affect positioning stability is thus shown in this paper. This is helpful for the understanding of how to reduce error sources from the design point of view.

Rotor Vibration under the Coupled Effects of Mass Unbalance and Asymmetric Bearings

2016 ◽  
Vol 846 ◽  
pp. 199-204 ◽  
Author(s):  
Joseph Patrick Spagnol ◽  
Helen Wu
Keyword(s):  
Critical Speed ◽  
High Energy ◽  
Damping Matrix ◽  
Mass Unbalance ◽  
Rotor Bearing ◽  
Bearing Stiffness ◽  
Stiffness And Damping Coefficient ◽  
Early Fault Detection ◽  
Stiffness And Damping ◽  
Rotor Dynamic

Large unbalance in rotor-dynamic systems is typically responsible for high energy vibrations and the consequent decrease in machine life. This paper presents an analytical model developed using Lagrangian mechanics and partial differential equations (PDEs) for the purpose of early fault-detection in rotor-bearing systems. The model was validated through a Fortran based program, RDA99 developed by Adams (2010), by successfully quantifying the single-peak unbalance response of the simple 8 DOF and 12 DOF rotor-bearing mass stations over two cases. Case I uses bearings with symmetric stiffness and damping matrix. The critical speed for Case I occurred at 1690 rpm and orbital shapes of each mass station was found to be circular with forward-whirl orbits. In Case II asymmetrical bearing stiffness and damping coefficient matrices demonstrate an anisotropic system. Critical speed occurred at 1655 rpm and rotor, bearing and pedestal orbits were seen to be elliptical and changing with shaft speed. Both cases demonstrated a significant shaft bending contribution to the disk displacement.

Effect of Manufacturing Tolerances on Stiffness and Damping of Hydrodynamic Journal Bearings

2010 ◽  
Vol 139-141 ◽  
pp. 2662-2667
Author(s):  
Wu Bin Xu ◽  
Peter J. Ogrodnik ◽  
Mike J. Goodwin ◽  
Gordon Bancroft
Keyword(s):  
Journal Bearing ◽  
Design Stage ◽  
Design Parameters ◽  
Damping Characteristics ◽  
Theoretical Predictions ◽  
Bearing Stiffness ◽  
Manufacturing Tolerances ◽  
Hydrodynamic Journal Bearing ◽  
Stiffness And Damping ◽  
Bearing System

From a manufacturing viewpoint, the manufacturing tolerances of a hydrodynamic journal bearing system are inevitable. To examine and understand the effect of manufacturing tolerances on dynamic characteristics of a hydrodynamic journal bearing system can help engineers to confidently choose reasonable tolerances at design stage or to enable the system with certain manufacturing tolerances to operate closer to the theoretical predictions. This study presented a theoretical analysis method to determine and demonstrate the effect of manufacturing tolerances on bearing stiffness and damping, in which the concepts of limits, tolerances and nominal dimensions are introduced in. The results show that the manufacturing tolerances of a hydrodynamic journal bearing system have profound influences on the bearing stiffness and damping, and the magnitude of effect depends on system design parameters in the form of Sommerfeld number. The presented method will better predict system stiffness and damping characteristics.

Identification of Bearing Stiffness and Damping Coefficients Using Phase-Plane Diagrams

2012 ◽  
Author(s):  
Juan C. Jáuregui ◽  
Luis San Andrés ◽  
Oscar De Santiago
Keyword(s):  
Phase Diagram ◽  
Reference Model ◽  
Measurement Data ◽  
Point Of View ◽  
Dynamic Parameters ◽  
Force Coefficients ◽  
On Line ◽  
Bearing Stiffness ◽  
Spring System ◽  
Stiffness And Damping

The reliable identification of dynamic parameters in mechanical systems remains a big challenge, in particular for nonlinear systems. There is not a single mathematical model encompassing the universe of most systems. From a practical point of view, the identification of system parameters depends on the measurement data as well as on the reference model. This paper presents a novel method for identifying the dynamic parameters of a gas bearing, whose force coefficients are strong functions of frequency. The method is based on the analysis of the phase diagram with the model assuming a mass-damper-spring system with time-dependent force coefficients. The phase diagram could be implemented electronically for on line monitoring and ready fault detection.

THEORETICAL AND METHODOLOGICAL ASPECTS OF UNDERSTANDING OF THE SYSTEM OBJECT IN DESIGN

2020 ◽  
Vol 1 (4) ◽  
pp. 5-10
Author(s):  
V. Barysheva ◽  
O. Druzhinina
Keyword(s):  
Scientific Research Institute ◽  
Point Of View ◽  
Design Stage ◽  
Comprehensive Understanding ◽  
Design Culture ◽  
Design Program ◽  
Methodological Aspects ◽  
Cultural Experts ◽  
Union Scientific Research Institute ◽  
Separate Product

The article is devoted to the analysis of the system object from the point of view of design from design, sociocultural and philosophical positions. The authors systematize the definitions of a system object of design proposed in the 1960–1980s by theorists and practitioners, art historians, cultural experts and philosophers from different countries, including Russia, which allows a comprehensive understanding of the phenomenon of design culture. This article is devoted to the characteristic properties of the system object in design. They were considered and analyzed on the example of the «Absheron» design-program when designing of agricultural village). This concept was developed at the All-Union Scientific Research Institute of Technical Aesthetics (VNIITE) in 1983. Using the same example, the features of the approach to designing a system object in design was observed not only as a separate product, but as a sociocultural situation that constantly changes at each design stage.

scholarly journals Design and Field Validation of a Low Power Wireless Sensor Node for Structural Health Monitoring

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1050
Author(s):  
Federico Zanelli ◽  
Francesco Castelli-Dezza ◽  
Davide Tarsitano ◽  
Marco Mauri ◽  
Maria Laura Bacci ◽  
...  
Keyword(s):  
Low Power ◽  
Sensor Node ◽  
Weather Conditions ◽  
Point Of View ◽  
Design Stage ◽  
Monitoring Systems ◽  
Wireless Sensor Node ◽  
Process Data ◽  
Fatigue Life Estimation ◽  
Remaining Fatigue Life

Smart monitoring systems are currently gaining more attention and are being employed in several technological areas. These devices are particularly appreciated in the structural field, where the collected data are used with purposes of real time alarm generation and remaining fatigue life estimation. Furthermore, monitoring systems allow one to take advantage of predictive maintenance logics that are nowadays essential tools for mechanical and civil structures. In this context, a smart wireless node has been designed and developed. The sensor node main tasks are to carry out accelerometric measurements, to process data on-board, and to send wirelessly synthetic information. A deep analysis of the design stage is carried out, both in terms of hardware and software development. A key role is played by energy harvesting integrated in the device, which represents a peculiar feature and it is thanks to this solution and to the adoption of low power components that the node is essentially autonomous from an energy point of view. Some prototypes have been assembled and tested in a laboratory in order to check the design features. Finally, a field test on a real structure under extreme weather conditions has been performed in order to assess the accuracy and reliability of the sensors.

scholarly journals Crystallographic and structural characterization of heterometallic platinum compounds Part VII. Heterohepta- and heterooctanuclear clusters

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Milan Melnik ◽  
Peter Mikuš ◽  
Clive E. Holloway
Keyword(s):  
Structural Characterization ◽  
Structural Parameters ◽  
Bond Distance ◽  
Point Of View ◽  
Platinum Compounds ◽  
Metal Atoms ◽  
Platinum Clusters ◽  
Structural Point

AbstractThis review classifies and analyzes over fifty heterohepta- and heterooctanuclear platinum clusters. There are eight types of metal combinations in heteroheptanuclear: Pt6M, Pt5M2, Pt4M3, Pt3M4, Pt2M5, PtM6, Pt3Hg2Ru2 and Pt2Os3Fe2. The seven metal atoms are in a wide variety of arrangements, with the most common being one in which the central M atom (mostly M(I)) is sandwiched by two M3 triangles. Another arrangement often found is an octahedron of M6 atoms asymmetrically capped by an M atom. The shortest Pt-M bond distances (non-transition and transition) are 2.326(1) Å (M = Ga) and 2.537(6) Å (M = Fe). The shortest Pt-Pt bond distance is 2.576(2) Å.In heterooctanuclear platinum clusters there are eight types of metal combinations: Pt6M2, Pt4M4, Pt3Ru5, Pt2M6, PtM7, Pt2W4Ni2, PtAu6Hg and PtAu5Hg2. From a structural point of view, the clusters are complex with bicapped octahedrons of eight metal atoms prevailing. The shortest Pt-M bond distances (non-transition and transition) are 2.651(3) Å (M = Hg) and 2.624(1) Å (M = Os). The shortest Pt-Pt bond distance is 2.622(1) Å. These values are somewhat longer than those in the heteroheptanuclear clusters. Several relationships between the structural parameters were found, and are discussed and compared with the smaller heterometallic platinum clusters

Estimating Critical Speeds of Stepped Shafts with Flexible Bearings

1971 ◽  
Vol 8 (03) ◽  
pp. 327-333
Author(s):  
R. H. Salzman
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Design Stage ◽  
Normal Range ◽  
Critical Speeds ◽  
Stepped Shaft ◽  
Bearing Stiffness ◽  
Variable Support ◽  
Method Show ◽  
Good Agreement

This paper presents a semi-graphical approach for finding the first critical speed of a stepped shaft with finite bearing stiffness. The method is particularly applicable to high-speed turbine rotors with journal bearings. Using Rayleigh's Method and the exact solution for whirling of a uniform shaft with variable support stiffness, estimates of the lowest critical speed are easily obtained which are useful in the design stage. First critical speeds determined by this method show good agreement with values computed by the Prohl Method for the normal range of bearing stiffness. A criterion is also established for determining if the criticals are "bearing critical speeds" or "bending critical speeds," which is of importance in design. Discusser E. G. Baker

Performance Analysis of Gas-Expanded Lubricants in a Hybrid Bearing Using Computational Fluid Dynamics

2015 ◽  
Author(s):  
Brian K. Weaver ◽  
Gen Fu ◽  
Andres F. Clarens ◽  
Alexandrina Untaroiu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Phase Behavior ◽  
Ambient Pressure ◽  
Operating Conditions ◽  
Full Potential ◽  
Dissolved Carbon ◽  
Bearing Stiffness ◽  
Multi Phase ◽  
Stiffness And Damping

Gas-expanded lubricants (GELs), tunable mixtures of synthetic oil and dissolved carbon dioxide, have been previously shown to potentially increase bearing efficiency, rotordynamic control, and long-term reliability in flooded journal bearings by controlling the properties of the lubricant in real time. Previous experimental work has established the properties of these mixtures and multiple numerical studies have predicted that GELs stand to increase the performance of flooded bearings by reducing bearing power losses and operating temperatures while also providing control over bearing stiffness and damping properties. However, to date all previous analytical studies have utilized Reynolds equation-based approaches while assuming a single-phase mixture under high-ambient pressure conditions. The potential implications of multi-phase behavior could be significant to bearing performance, therefore a more detailed study of alternative operating conditions that may include multi-phase behavior is necessary to better understanding the full potential of GELs and their effects on bearing performance. In this work, the performance of GELs in a fixed geometry journal bearing were evaluated to examine the effects of these lubricants on the fluid and bearing dynamics of the system under varying operating conditions. The bearing considered for this study was a hybrid hydrodynamic-hydrostatic bearing to allow for the study of various lubricant supply and operating conditions. A computational fluid dynamics (CFD)-based approach allowed for a detailed evaluation of the lubricant injection pathway, the flow of fluid throughout the bearing geometry, thermal behavior, and the collection of the lubricant as it exits the bearing. This also allowed for the study of the effects of the lubricant behavior on overall bearing performance.

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