scholarly journals Self-Tuning Algorithm for Tuneable Clamping Table for Chatter Suppression in Blade Recontouring

2021 ◽  
Vol 11 (6) ◽  
pp. 2569
Author(s):  
Markel Sanz-Calle ◽  
Zoltan Dombovari ◽  
Jokin Munoa ◽  
Alexander Iglesias ◽  
Luis Norberto López de Lacalle
Keyword(s):  
Limiting Factors ◽  
Chatter Suppression ◽  
Milling Operations ◽  
Blade Machining ◽  
Eddy Current Damping ◽  
In Series ◽  
Bandwidth Tuning ◽  
Self Tuning ◽  
Tuning Methods ◽  
Stiffness And Damping

The production and repair of blades for aerospace engines and energy turbines is a complex process due their inherently low stiffness and damping properties. The final recontouring operation is usually performed by milling operations where regenerative chatter is one of the main productivity limiting factors. With the objective of avoiding specific stiffening fixtures for each blade geometry, this paper proposes a semi-active tuneable clamping table (TCT) based on mode tuning for blade machining. The active mode of the device can be externally controlled by means of a rotary spring and eddy current damping modules. Its in-series architecture allows damping to be introduced to the critical mode of the thin-walled part without any direct contact in the machining area and enables a more universal clamping. Its chatter suppression capabilities are maximized by means of a novel self-tuning algorithm that iteratively optimizes the tuning for the measured chatter frequency. The benefits of the iterative algorithm are validated through semidiscretization and initial value time-domain simulations, showing a clear improvement in blade recontouring stability compared to regular broad-bandwidth tuning methods.

scholarly journals Optimum Selection of Variable Pitch for Chatter Suppression in Face Milling Operations

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 112 ◽  
Author(s):  
Alex Iglesias ◽  
Zoltan Dombovari ◽  
German Gonzalez ◽  
Jokin Munoa ◽  
Gabor Stepan
Keyword(s):  
Removal Rate ◽  
Face Milling ◽  
Heavy Duty ◽  
Variable Pitch ◽  
Thin Walls ◽  
Chatter Suppression ◽  
Milling Operations ◽  
Optimum Selection ◽  
Cutting Capacity ◽  
Selection Of

Cutting capacity can be seriously limited in heavy duty face milling processes due to self-excited structural vibrations. Special geometry tools and, specifically, variable pitch milling tools have been extensively used in aeronautic applications with the purpose of removing these detrimental chatter vibrations, where high frequency chatter related to slender tools or thin walls limits productivity. However, the application of this technique in heavy duty face milling operations has not been thoroughly explored. In this paper, a method for the definition of the optimum angles between inserts is presented, based on the optimum pitch angle and the stabilizability diagrams. These diagrams are obtained through the brute force (BF) iterative method, which basically consists of an iterative maximization of the stability by using the semidiscretization method. From the observed results, hints for the selection of the optimum pitch pattern and the optimum values of the angles between inserts are presented. A practical application is implemented and the cutting performance when using an optimized variable pitch tool is assessed. It is concluded that with an optimum selection of the pitch, the material removal rate can be improved up to three times. Finally, the existence of two more different stability lobe families related to the saddle-node and flip type stability losses is demonstrated.

scholarly journals BELAIDŽIO RYŠIO SIŲSTUVŲ-IMTUVŲ SUSIDERINIMO BŪDŲ ANALIZĖ / ANALYSIS OF SELF TUNING METHODS FOR DIRECT CONVERSION TRANSCEIVERS

2018 ◽  
Vol 10 (0) ◽  
pp. 1-11
Author(s):  
Leonid Kladovščikov ◽  
Romualdas Navickas
Keyword(s):  
Direct Conversion ◽  
Self Tuning ◽  
Tuning Methods

Integrinių grandynų gamybos technologinių procesų paklaidos didina daugiastandarčių siųstuvų-imtuvų komponentų parametrų sklaidą ir blogina jų veiką, tad siekiama komponentų verčių nuokrypius kompensuoti. Pagrindiniai derinami parametrai yra tokie: siųstuvo ir imtuvo kvadratūrinių kanalų nuolatinės dedamosios, amplitudės ir fazės poslinkiai, antrosios eilės iškraipymai. Darbe išanalizuoti žinomi daugiastandarčių belaidžio ryšio siųstuvų-imtuvų derinimo būdai, jie suskirstyti į tiesioginio, netiesioginio ir grįžtamojo ryšio bei mišriuosius būdus. Ištirtos analoginės ir skaitmeninės modernių siųstuvų-imtuvų derinimo sistemos, atlikta jų privalumų ir trūkumų bei modernioms belaidžio ryšio sistemoms aktualių derinimo parametrų analizė.

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.

scholarly journals DESIGN OF A FAST SERVO MULTI-ELEMENT FEED DRIVE

2011 ◽  
Author(s):  
A. T. Elfizy ◽  
M. A. Elbestawi
Keyword(s):  
High Resolution ◽  
Data Storage ◽  
High Precision ◽  
Experimental Testing ◽  
Drive System ◽  
Precision Positioning ◽  
Chatter Suppression ◽  
Feed Drive ◽  
In Series ◽  
Feed Drive System

High precision positioning has become one of the most important features of a precision machine. Such a machine is required to provide versatility, speed and workspace and high precision positioning. Combining coarse (large stroke) and fine (high resolution) drive elements, connected in series, in a multi-element feed drive system provides the capacity of a large workspace with the property of high resolution motion. The performance of the whole system may be improved by adopting the merits of both drive elements to work in a complementary fashion. The multi-element feed drive concept has several applications in manufacturing, robotics and data storage. Fast tool servo in manufacturing is a direct use of the concept and its applications range from the creation of asymmetric surfaces to online chatter suppression. Micro-macro robots are also examples of multi-element feed drive systems that provide advantages when both large work space and accurate end-effector positioning are required. This paper presents an innovative design of a multi-element feed drive system for machine tools. It studies the design methodology and the implementation of the system and investigates several considerations that govern the design process and determine the performance. A multi-element feed drive setup based on a combination of PA and LM was built for experimental testing. Results show that the multi-element feed drive is able to improve the tracking performance as well as the steady state error. It also achieves faster settling time.

Energy harvesting from car suspension system: Mathematical approach for half car model

2021 ◽  
Vol 15 (1) ◽  
pp. 7695-7714
Author(s):  
Tariq Darabseh ◽  
Doaa Al-Yafeai ◽  
Abdel-Hamid Ismail Mourad
Keyword(s):  
Significant Contribution ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Suspension System ◽  
Ride Quality ◽  
Car Model ◽  
Car Suspension ◽  
In Series ◽  
Piezoelectric Stacks ◽  
Stiffness And Damping

A significant contribution of this paper is developing a half car model with a built-in piezoelectric stack to evaluate the potential of harvesting power from the car suspension system. The regenerative car suspension system is modelled mathematically using Laplace transformation and simulated using MATLAB/Simulink. Two piezoelectric stacks are installed in series with the front and rear suspension springs to maintain the performance of the original suspension system in ride quality and comfortability. Half car model is subjected under harmonic excitation with acceleration of 0.5 g and velocity of 9.17 rad/s. The harvested voltage and power are tested in both time, and frequency domain approaches. The influence of the different parameters of the piezoelectric stack (number of stack layers and area to thickness) and car suspension (sprung and unsprung stiffness and damping coefficients) are examined. Also, the effect of road amplitude unevenness is considered. The results illustrate that the maximum generated voltage and power at the excitation frequency of 1.46 Hz are 33.51 V and 56.25 mW, respectively.

Effective and Robust Vibration Control Using Series Multiple Tuned-Mass Dampers

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Lei Zuo
Keyword(s):  
Total Mass ◽  
Primary System ◽  
Vibration Absorbers ◽  
Mass Ratio ◽  
Tuned Mass Dampers ◽  
In Series ◽  
New Type ◽  
Parameter Variance ◽  
Stiffness And Damping ◽  
Optimal Series

Various types of tuned-mass dampers (TMDs), or dynamic vibration absorbers, have been proposed in literature, including the classic TMD, (parallel) multiple TMDs, multidegree-of-freedom (DOF) TMD, and three-element TMD. In this paper we study the characteristics and optimization of a new type of TMD system, in which multiple absorbers are connected to the primary system in series. Decentralized H2 and H∞ control methods are adopted to optimize the parameters of spring stiffness and damping coefficients for random and harmonic vibration. It is found that series multiple TMDs are more effective and robust than all the other types of TMDs of the same mass ratio. The series two TMDs of total mass ratio of 5% can appear to have 31–66% more mass than the classical TMD, and it can perform better than the optimal parallel ten TMDs of the same total mass ratio. The series TMDs are also less sensitive to the parameter variance of the primary system than other TMD(s). Unlike in the parallel multiple TMDs where at the optimum the absorber mass is almost equally distributed, in the optimal series TMDs the mass of the first absorber is generally much larger than the second one. Similar to the 2DOF TMD, the optimal series two TMDs also have zero damping in one of its two connections, and further increased effectiveness can be obtained if a negative dashpot is allowed. The optimal performance and parameters of series two TMDs are obtained and presented in a form of ready-to-use design charts.

scholarly journals Piezoelectric Shunt Stiffness in Rhombic Piezoelectric Stack Transducer with Hybrid Negative-Impedance Shunts: Theoretical Modeling and Stability Analysis

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3387
Author(s):  
He ◽  
Zheng ◽  
Zhao ◽  
Wu
Keyword(s):  
Coupled System ◽  
Analytical Framework ◽  
Negative Stiffness ◽  
Negative Capacitance ◽  
Control Engineering ◽  
Locus Method ◽  
In Series ◽  
The Stability ◽  
Stiffness And Damping ◽  
Piezoelectric Shunt

Negative-capacitance shunted piezoelectric polymer was investigated in depth due to its considerable damping effect. This paper discusses the novel controlled stiffness performance from a rhombic piezoelectric stack transducer with three hybrid negative-impedance shunts, namely, negative capacitance in series with resistance, negative capacitance in parallel with resistance, and negative inductance/negative capacitance (NINC) in series with resistance. An analytical framework for establishing the model of the coupled system is presented. Piezoelectric shunt stiffness (PSS) and piezoelectric shunt damping (PSD) are proposed to analyze the stiffness and damping performances of the hybrid shunts. Theoretical analysis proves that the PSS can produce both positive and negative stiffness by changing the negative capacitance and adjustable resistance. The Routh–Hurwitz criterion and the root locus method are utilized to judge the stability of the three hybrid shunts. The results point out that the negative capacitance should be selected carefully to sustain the stability and to achieve the negative stiffness effect of the transducer. Furthermore, negative capacitance in parallel with resistance has a considerably better stiffness bandwidth and damping performance than the other two shunts. This study demonstrates a novel electrically controlled stiffness method for vibration control engineering.

Research on the Boring Chatter Suppression Based on MR Fluid

2006 ◽  
Vol 532-533 ◽  
pp. 365-368
Author(s):  
Tian Rong Kong ◽  
Zhe He Yao ◽  
Zi Chen Chen
Keyword(s):  
Magnetic Field ◽  
Experimental System ◽  
Machining Accuracy ◽  
Mr Fluid ◽  
Boring Bar ◽  
Chatter Suppression ◽  
Excitation Coil ◽  
Precision Hole ◽  
Stiffness And Damping ◽  
Working Efficiency

Chatter during boring process is one of the main adverse factors influenced on the machining accuracy of precision hole, surface quality and working efficiency. In order to suppress chatter, an innovative controlling means of MR-intelligent-boring-bar with self-chatter-suppression is proposed, which is composed of MR fluid, shell structure, excitation coil and boring bar. The MR fluid’s mechanical characteristic can be adjusted by changing the intensity of magnetic field, thus the system stiffness and damping will be modified, and then the boring chatter can be suppressed. Otherwise, the dynamic model of MR-intelligent-boring-bar with self-chatter-suppression is built. Lastly, the experimental system of MR-intelligent-boring-bar is established, and the experiments of chatter suppression during boring process are performed. The results of experiments show that the new means of chatter suppression is effective.

scholarly journals Toward Efficient Navigation of Massive-Scale Geo-Textual Streams

2019 ◽  
Author(s):  
Chengcheng Yang ◽  
Lisi Chen ◽  
Shuo Shang ◽  
Fan Zhu ◽  
Li Liu ◽  
...  
Keyword(s):  
Cost Model ◽  
Streaming Data ◽  
Maintenance Cost ◽  
Portable Devices ◽  
Time Data ◽  
Tuning Method ◽  
Massive Scale ◽  
Self Tuning ◽  
Real World Datasets ◽  
Tuning Methods

With the popularization of portable devices, numerous applications continuously produce huge streams of geo-tagged textual data, thus posing challenges to index geo-textual streaming data efficiently, which is an important task in both data management and AI applications, e.g., real-time data streams mining and targeted advertising. This, however, is not possible with the state-of-the-art indexing methods as they focus on search optimizations of static datasets, and have high index maintenance cost. In this paper, we present NQ-tree, which combines new structure designs and self-tuning methods to navigate between update and search efficiency. Our contributions include: (1) the design of multiple stores each with a different emphasis on write-friendness and read-friendness; (2) utilizing data compression techniques to reduce the I/O cost; (3) exploiting both spatial and keyword information to improve the pruning efficiency; (4) proposing an analytical cost model, and using an online self-tuning method to achieve efficient accesses to different workloads. Experiments on two real-world datasets show that NQ-tree outperforms two well designed baselines by up to 10×.

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