scholarly journals Design of Two-Axial Actuator for Controlled Vibration Damper for Large Rams

Actuators ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 199
Author(s):  
Lukáš Novotný ◽  
Jaroslav Červenka ◽  
Matěj Sulitka ◽  
Jiří Švéda ◽  
Miroslav Janota ◽  
...  
Keyword(s):  
Machine Tool ◽  
Vibration Suppression ◽  
Dynamic Compliance ◽  
Current Control ◽  
Dynamic Force ◽  
Position Measurement ◽  
Electric Drives ◽  
Construction Design ◽  
Stiffness And Damping ◽  
Contact Position

Machine tool rams are important constructional elements found on vertical lathes as well as on many other machines. In most cases, a machine tool ram constitutes an assembly with significant dynamic compliance that affects the machine’s ability to achieve stable cutting conditions. There are various solutions for increasing a machine tool ram’s stiffness and damping. This paper describes an innovative concept of a two-axial electromagnetic actuator for controlled vibration dampers with high dynamic force values. The described solution is purposefully based on the use of standard electric drives. As a result, the size of the actuator is easier to scale to the required application. The solution is designed as a spacer between the end of the ram and the head. The paper presents the actuator concept, construction design, current control loop solution and experimental verification of the controlled vibration damper’s function on the test ram in detail. The presented position measurement concept will enable the use of non-contact position sensors for motor commutation as well as for possible use in vibration suppression control. Applications can be expected mainly in the field of vibration suppression of vertical rams of large machine tools.

Experimental and Theoretical Rotordynamic Characteristics of a Hybrid Journal Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 132-141 ◽  
Author(s):  
J. T. Sawicki ◽  
R. J. Capaldi ◽  
M. L. Adams
Keyword(s):  
Journal Bearing ◽  
Operating Conditions ◽  
Dynamic Force ◽  
Test Results ◽  
Force Measurements ◽  
Lubrication Equation ◽  
Load Cells ◽  
Theoretical Predictions ◽  
Stiffness And Damping

This paper describes an experimental and theoretical investigation of a four-pocket, oil-fed, orifice-compensated hydrostatic bearing including the hybrid effects of journal rotation. The test apparatus incorporates a double-spool-shaft spindle which permits independent control over the journal spin speed and the frequency of an adjustable-magnitude circular orbit, for both forward and backward whirling. This configuration yields data that enables determination of the full linear anisotropic rotordynamic model. The dynamic force measurements were made simultaneously with two independent systems, one with piezoelectric load cells and the other with strain gage load cells. Theoretical predictions are made for the same configuration and operating conditions as the test matrix using a finite-difference solver of Reynolds lubrication equation. The computational results agree well with test results, theoretical predictions of stiffness and damping coefficients are typically within thirty percent of the experimental results.

Active Vibration Absorption Using Delayed Resonator With Relative Position Measurement

1995 ◽  
Author(s):  
Nejat Olgac ◽  
Martin Hosek
Keyword(s):  
Relative Position ◽  
Primary Structure ◽  
Vibration Suppression ◽  
Control Force ◽  
Range Analysis ◽  
Position Measurement ◽  
Harmonic Force ◽  
Stability Range ◽  
Vibration Absorption ◽  
Active Vibration

Abstract A novel active vibration absorption technique, the Delayed Resonator, has been introduced recently as a unique way of suppressing undesired oscillations. It suggests a control force on a mass-spring-damper absorber in the form of a proportional position feedback with a time delay. Its strengths consist of extremely simple implementation of the control algorithm, total vibration suppression of the primary structure against a harmonic force excitation and full effectiveness of the absorber in a semi-infinite range of disturbance frequency, achieved by real-time tuning. All this development work was done using the absolute displacements of the absorber in the feedback. These displacement measurements may be difficult to obtain and for some applications impossible. This paper deals with a substitute and easier measurement: the relative motion of the absorber with respect to the primary structure. Theoretical foundations for the Delayed Resonator (DR) are briefly recapitulated and its implementation on a single-degree-of-freedom primary structure disturbed by a harmonic force is introduced utilizing both absolute and relative position measurement of absorber mass. Methods for stability range analysis and transient behavior are presented. Properties acquired for the same system with these two different feedback are compared. Relative position measurement case is found to be more advantageous in most applications of the Delayed Resonator method.

Method of Assessment of Casting Accuracy and Minimization of Machining Allowances

2012 ◽  
Author(s):  
Andrzej Gessner ◽  
Roman Staniek
Keyword(s):  
Machine Tool ◽  
Accuracy Assessment ◽  
Assessment Method ◽  
Machining Process ◽  
Shape Accuracy ◽  
Construction Design ◽  
Optical Scanner ◽  
Course Of Action ◽  
Reference Design ◽  
Method Of Assessment

The publication demonstrates an accuracy assessment method for machine tool body casting utilizing an optical scanner and a reference design of the machine tool body. The process allows assessing the casting shape accuracy, as well as determining whether the size of the allowances of all work surfaces is sufficient for appropriate machining, corresponding to the construction design. The described method allows dispensing with the arduous manual operation - marking out. Marking out, depending on the size and complexity, might take several working shifts for prototype casting. In case of large and elaborate casts, as those of machine tool bodies, marking out is often restricted only to the first cast of the desired body produced in a given casting mold. Such course of action is based on an assumption that casting is reproducible; hence, no need to assess each and every individual cast. While this approach saves time, it often results in late detection of casting errors (allowance shifts or insufficiencies) during the actual machining process. That, in turn, results in considerable losses due to the disruption of the work process and often demands cast repair. The aim of the hereby presented study is to introduce a new technological premise dispensing with manual marking out as well as allowing fast verification of the cast shapes.

A Low-Cost and High-Resolution Micro Machine Tool With Toggle-Based Mechanism

2014 ◽  
Author(s):  
Shih-Ming Wang ◽  
Chih-Peng Yang ◽  
Zhe-Zhi Ye ◽  
Chuntai Yen
Keyword(s):  
Machine Tool ◽  
Low Cost ◽  
Dynamic Compliance ◽  
Cnc Machine ◽  
Positioning Accuracy ◽  
New Type ◽  
Weight Structure ◽  
Micro Machine ◽  
Fine Resolution ◽  
Micro Machine Tool

The products of 3C, bioscience, medical industry, and aerospace industry are becoming smaller and smaller. The components of the products are made of various materials with complex 3D shapes requiring high accuracy in their dimensions and contours. An accurate micro-/meso-scale CNC machine tool is an essential part of this technology. A new type of CNC micro machine tool with a toggle-like mechanism having the characteristics of low-cost and fine-resolution was developed. With geometric reduction principle, the machine can provide finer feed resolution and better positioning accuracy without using high-end driving components and controller. The kinematics model and characteristics of the machine were derived and analyzed. Modal analysis and dynamic compliance analysis were employed to design a light-weight structure with good stiffness. The accuracy calibration results showed the machine can reach a positioning accuracy of 500 nm. Prototype of the machine was built, and furthermore some micro machining examples were demonstrated in this paper.

scholarly journals Effects of Design Alterations on the Vibration Suppression of a Machine Tool Structure

2016 ◽  
Vol 15 (3) ◽  
pp. 122-129 ◽  
Author(s):  
Young Jo Kim ◽  
Seung Hoon Ro ◽  
Ho Beom Shin ◽  
Yun Ho Shin ◽  
Keun Sup Jung ◽  
...  
Keyword(s):  
Machine Tool ◽  
Vibration Suppression ◽  
Machine Tool Structure

Substructure Coupling of a Machine Tool in Arbitrary Axis Positions Considering Local Linear Damping Models

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Thomas Semm ◽  
Michael B. Nierlich ◽  
Michael F. Zaeh
Keyword(s):  
Finite Element ◽  
Machine Tool ◽  
Dynamic Behavior ◽  
Element Model ◽  
Damping Behavior ◽  
Linear Damping ◽  
Virtual Prototypes ◽  
Damping Effects ◽  
Stiffness And Damping ◽  
Arbitrary Axis

Virtual prototypes, e.g., finite element models, are commonly used to reduce the development times of a new machine tool generation. However, the accuracy of these models is often limited by their representation of damping effects and the possibility to efficiently simulate the dynamic behavior in different axis positions. This paper shows the changing local damping distribution within a single-axis machine tool configuration for different axis positions. Based on this investigation, an approach to accurately model the position-dependent dynamics, while keeping the calculation times small, is presented. The virtual model of the machine is divided in several substructures, which consider the local damping behavior of each dissipation source. The reduced mass, stiffness, and damping matrices are coupled in the desired machine position by using multipoint constraints, which are generated at the desired machine position after the reduction of the substructures. Four different approaches to apply multipoint constraints on reduced substructures are compared, followed by an investigation of their influencing parameters. The most promising approach is compared with a model without local damping representation as well as a model without substructuring. By considering the local damping effects within the finite element model and coupling the reduced models of each component in arbitrary axis positions, an efficient analysis and optimization of the dynamic behavior of a machine tool over the whole workspace can be conducted.

scholarly journals The Effect of the Pivot Stiffness on the Performances of Five-Pad Tilting Pad Bearings

Lubricants ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 61 ◽  
Author(s):  
Phuoc Vinh Dang ◽  
Steven Chatterton ◽  
Paolo Pennacchi
Keyword(s):  
Excitation Frequency ◽  
Experimental Results ◽  
Dynamic Force ◽  
Dynamic Coefficients ◽  
Pivot Bearing ◽  
Tilting Pad ◽  
In Series ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearings

The role of the pivot flexibility in tilting-pad journal bearings (TPJBs) has become essential, particularly for bearings working at high applied load and relatively high rotor speeds. Predictions from a simple bearing model with rigid pivots show incorrect estimation of the dynamic coefficients in comparison with the experimental results. Normally, the more flexible the pad pivot, the lower the dynamic coefficients because the stiffness of the pivot takes in series with the stiffness and damping of the oil film. This paper investigates the influence of pivot stiffness on the dynamic force coefficients of two different five-pad TPJBs as a function of the applied static load and excitation frequency: rocker-backed pivot and spherical pivot bearings. In order to highlight the effect of the pivot stiffness in the spherical pivot bearing, displacement restriction components and elastic copper made shims have been used. Firstly, a thermo-elasto-hydrodynamic model for the static and dynamic characteristics of the two bearings is described. This model takes into account the flexibility of both pad and pivot. The pivot stiffnesses calculated by means of the Hertz theory and those obtained by experiments have been introduced and compared in the model. The clearance profiles of two tested bearing and the shaft center loci obtained by measurement and prediction are also shown. The dynamic coefficients of the two bearings obtained from the numerical simulation were compared with the experimental results. By the analysis it can be concluded that the effect of the pivot flexibility on the clearance profile, the shaft locus and on the dynamic coefficients is very significant. More important, it is important to estimate the pivot stiffness of each single pad using experimental measurements.

Broadband Vibration Suppression Assessment of Negative Impedance Shunts

2008 ◽  
Author(s):  
Benjamin Beck ◽  
Kenneth A. Cunefare ◽  
Massimo Ruzzene
Keyword(s):  
Active Control ◽  
Vibration Suppression ◽  
Piezoelectric Materials ◽  
Input Power ◽  
Experimental Results ◽  
Spatial Average ◽  
Negative Capacitance ◽  
Damping Properties ◽  
Control Solution ◽  
Stiffness And Damping

Piezoelectric materials allow for the manipulation of stiffness and damping properties of host structures by the application of electrical shunting networks. The use of piezoelectric patches for broadband control of vibration using a negative impedance shunt has been shown to be an effective active control solution. The wave-tuning and minimization of reactive input power shunt selection methodologies require the use a negative capacitance. This paper shows that the two theories are comparative and obtain the same shunt parameters. The results of the theoretical shunt selection and simulation are compared to experimental results of tip vibration suppression, spatial average vibration, and reactive input power minimization.

Research on Auxiliary Electromagnetic Damping System for Machine Tool Spindle

2012 ◽  
Vol 271-272 ◽  
pp. 617-620
Author(s):  
Han Wang ◽  
Xin Du Chen ◽  
Xue Song Chen ◽  
Qiang Liu ◽  
Zhi Jun Yang ◽  
...  
Keyword(s):  
Machine Tool ◽  
Low Cost ◽  
Dynamic Control ◽  
Machining Accuracy ◽  
Magnetic Actuator ◽  
Machine Tool Spindle ◽  
Electromagnetic Damping ◽  
Conventional Machine ◽  
Control Dynamic ◽  
Stiffness And Damping

This paper studies auxiliary electromagnetic damping system in the conventional machine tools. Through the establishment of auxiliary active magnetic actuator array and the application of optimal control, dynamic control of additional stiffness and damping are achieved, so some active interventions can be applied to reduce the chatter of traditional machine tool spindle. Thus it causes to lower the radial vibration amplitude of the spindle at work and improve the machining accuracy. The experiments show that this system can reduce more than 88.06% spindle radial amplitude, and it can actually improve the precision to about1um, so the system has enormous potential for low-cost upgrade of traditional machine.

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