Stiffness modeling, identification, and measuring of a rotating spindle

2019 ◽  
Vol 234 (6) ◽  
pp. 1239-1252
Author(s):  
Liping Wang ◽  
Binbin Zhang ◽  
Jun Wu ◽  
Qinzhi Zhao ◽  
Junjian Wang
Keyword(s):  
Least Squares Method ◽  
Machining Accuracy ◽  
Identification Algorithm ◽  
Principle Of Superposition ◽  
Stiffness Modeling ◽  
Comprehensive Method ◽  
High Speeds ◽  
Cutting Surface ◽  
Stiffness Model

The stiffness of a spindle at high speeds has a significant effect on the quality of the cutting surface and the machining accuracy. However, the spindle stiffness is difficult to be detected directly when the spindle is rotating, and the measured stiffness values are usually coupled with other parts of the spindle–tool system (such as toolholder, spindle–toolholder joint, tool). This paper presents a comprehensive method to deal with the stiffness modeling, identification, and measuring of a rotating spindle. Based on the deflection equation and the principle of superposition, the stiffness model is derived, for a spindle–tool system including a spindle, a specially manufactured toolholder, and a spindle–toolholder joint. A three-step identification algorithm is proposed to decouple and identify the actual spindle stiffness value. First, when the spindle is static, the stiffness values of the shaft, toolholder, and joint are obtained by using the least-squares method. Second, when the spindle is rotating, the stiffness values of the rear bearings and front bearings are identified based on the spindle error analysis method. Third, the stiffness values of the spindle under different rotating conditions are calculated based on the identification results from the previous two steps. Furthermore, the stiffness model and identification algorithm are verified experimentally on an instrumented spindle. The static stiffness value of the same spindle is also measured and compared with the stiffness value under rotating conditions subsequently. This work is useful and can be utilized as a guide for spindle stiffness testing and spindle performance evaluation to spindle manufacturers.

Paddlefish: Ecological, Aquacultural, and Regulatory Challenges of Managing a Global Resource

2019 ◽  
Keyword(s):  
Habitat Restoration ◽  
Local Level ◽  
High Speeds ◽  
The Status ◽  
Low Head ◽  
Management Techniques ◽  
High Head ◽  
Elevated Rate ◽  
Access And Quality

<i>Abstract</i>.—Paddlefish <i>Polyodon spathula</i> are behaviorally, morphologically, and physiologically adapted for prolonged free-swimming at moderately high speeds but not for maneuverability which makes them prone to impacts from submerged structures. These structures include low-head dams, weirs, dikes, levees, high-head dams, dredges, diversions, intakes, and vessels. Impacts include blocked migrations, reduced access and quality of habitat, entrainment, impingement, trauma, and stranding. Effects of these impacts on individuals are displacement, injuries, and death; effects on populations are fragmentation, lower gene flow, lower reproductive success, and elevated rate of mortality. Despite this, the status of the Paddlefish in most parts of its historic range is secure. Management techniques, like stocking and habitat restoration, are typically implemented at the local level but appear effective at conserving the species range wide. Refinement of management techniques, however, is still possible by modifying operations of structures and by rescuing stranded Paddlefish.

scholarly journals Rotation-joint stiffness modeling for industrial robots considering contacts

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879306 ◽  
Author(s):  
Zhifeng Liu ◽  
Jingjing Xu ◽  
Qiang Cheng ◽  
Yongsheng Zhao ◽  
Yanhu Pei
Keyword(s):  
Fractal Theory ◽  
Joint Stiffness ◽  
Industrial Robots ◽  
Torsional Stiffness ◽  
Equivalent Stiffness ◽  
Force Analysis ◽  
Joint System ◽  
End Effector ◽  
Stiffness Modeling ◽  
High Speeds

Joint flexibility has a major impact on the motion accuracy of a robotic end effector, particularly at high speeds. This work proposes a technique of precisely modeling the torsional stiffness of the rotational joints for the industrial robots. This technique considers the contacts that exist in the joint system, which can have a significant effect on the overall joint stiffness. The torsional stiffness of the connections that commonly exist in the rotational joints, such as the belt connection, the connections using key, bolts, and pins, were modeled by combining the force analysis and the fractal theory. Through modeling the equivalent stiffness for the springs in serial and in parallel, the torsional stiffness of all joints for the ER3A-C60 robot were calculated and analyzed. The results show that the estimated stiffness based on the proposed technique is closer to the actual values than that based on the previous model without considering the contacts. The analysis is useful for controlling the dynamic characteristic of the industrial robots with the rotational joints while planning the trajectory for the end effector.

The Study of Bone Cutting Force with FEM

2014 ◽  
Vol 974 ◽  
pp. 389-393 ◽  
Author(s):  
Sen Liu ◽  
Dong Mei Wu ◽  
Jun Zhao
Keyword(s):  
Finite Element ◽  
Cutting Force ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Element Model ◽  
Cutting Surface ◽  
On Line ◽  
Force Velocity ◽  
Optimization Of Cutting Parameters

In orthopedic surgery, it is easy to do harm to surrounding tissues, so the study of bone cutting is necessary. In this article, a finite element model (FEM) of orthogonal bone cutting is developed. Cutting force intra-operatively can provide the surgeon with additional on-line information to support him to control quality of cutting surface. The obtained cutting force decreased little with cutting speed increasing, but ascended evidently with cutting depth increasing. The results of finite element simulations are aimed at providing optimization of cutting parameters and the basic information for hybrid force-velocity control of a robot-assisted bone milling system.

Haptic Data Compression Based on Linear Prediction

2013 ◽  
Vol 712-715 ◽  
pp. 2712-2715
Author(s):  
Feng Hua Guo
Keyword(s):  
Data Reduction ◽  
Haptic Perception ◽  
Linear Prediction ◽  
Least Squares Method ◽  
Reduction Rate ◽  
Perceptual Quality ◽  
Data Packets ◽  
Data Reduction Technique ◽  
Prediction Approach

A new linear prediction-based haptic data reduction technique is presented. The prediction approach relies on the least-squares method to reduce the number of data packets. Knowledge from human haptic perception is incorporated into the architecture to assess the perceptual quality of the compressed haptic signals. Experiments prove the effectiveness of the proposed approach in data reduction rate.

scholarly journals Precision Machining of Nimonic C 263 Super AlloyUsing WEDM

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 590
Author(s):  
Katerina Mouralova ◽  
Libor Benes ◽  
Josef Bednar ◽  
Radim Zahradnicek ◽  
Tomas Prokes ◽  
...  
Keyword(s):  
Electrical Discharge ◽  
Cutting Speed ◽  
Machining Process ◽  
Precision Machining ◽  
Machining Accuracy ◽  
Pulse On Time ◽  
Pulse Off Time ◽  
Super Alloy ◽  
Machined Surfaces

Wire electrical discharge machining (WEDM) is an unconventional and very efficient technology for precision machining of the Nimonic C 263 super alloy, which is very widespread, especially in the energy, aerospace and automotive industries. Due to electrical discharge, defects in the form of cracks or burned cavities often occur on the machined surfaces, which negatively affect the correct functionality and service life of the manufactured components. To increase the efficiency of the machining of Nimonic C 263 using WEDM, in this study, extensive design of experiments was carried out, monitoring input factors in the form of machine parameters like Pulse off time, Gap voltage, Discharge current, Pulse on time and Wire feed, the output of which was comprehensive information about the behaviour of such machined surfaces, which allowed the optimization of the entire machining process. Thus, the optimization of the Cutting speed was performed in relation to the quality of the machined surface and the machining accuracy, as well as an analysis of the chemical composition of the machined surfaces and a detailed analysis of the lamella using a transmission electron microscope. A detailed study of the occurrence of surface or subsurface defects was also included. It was found that with the help of complex optimization tools, it is possible to significantly increase the efficiency of the machining of the Nimonic C 263 super alloy and achieve both financial savings in the form of shortened machine time and increasing the quality of machined surfaces.

Stiffness Modeling of the Tricept Robot Using the Overall Jacobian Matrix

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
Youyu Wang ◽  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Jacobian Matrix ◽  
Singular Value ◽  
Compatibility Conditions ◽  
Compliance Matrix ◽  
Stiffness Modeling ◽  
Global Indices ◽  
Stiffness Model ◽  
Stiffness Evaluation ◽  
Parallel Kinematic ◽  
Value Decomposition

Taking the 3DOF parallel mechanism within the Tricept robot as an example, this paper presents an analytical approach for the stiffness modeling of parallel kinematic machines having a properly constrained passive limb. The stiffness model is formulated using the 6×6overall Jacobian. It takes particular interest in the precise formulation of the bending stiffness matrix of the properly constrained passive limb by considering the compatibility conditions of the system. Stiffness evaluation of a sample Tricept robot is carried out using two global indices obtained from singular value decomposition of the compliance matrix.

Quality assurance for concave-arc ball-end milling cutters

2003 ◽  
Vol 217 (2) ◽  
pp. 181-191 ◽  
Author(s):  
W-F Chen ◽  
H-Y Lai ◽  
C-K Chen
Keyword(s):  
End Milling ◽  
Spherical Surface ◽  
Numerical Control ◽  
Machining Accuracy ◽  
Milling Cutter ◽  
Modelling Procedure ◽  
Profile Errors ◽  
Complicated Surface ◽  
Dies And Moulds

This paper presents a systematic modelling procedure for assessing the profile quality of concave-arc ball-end (CABE) milling cutters with a cylindrical shank. CABE milling cutters are widely used in three-axis numerical control (NC) machines for producing dies and moulds of complicated surface features. Evaluation of the contour quality of the CABE milling cutter is crucial in enhancing machining accuracy and efficiency. In order adequately to describe the shape of the clamped cutter, the centre-line axis of the minimum circumscribed cylinder of the cylinder shank is taken as the referenced datum axis. The minimum circumscribed concave-arc revolving surface and the minimum circumscribed spherical surface are carefully derived in sequence. The profile errors and tolerances are estimated. The quality of the CABE milling cutter is assured by using the proposed modelling procedure, and several numerical examples are presented to illustrate its effectiveness. The results indicate that the present method is feasible and can be extended to enhance the quality of various revolving cutters.

The Optimization Study about Technological Parameters of YAG Laser Precision Cutting Stainless Sheet

2013 ◽  
Vol 652-654 ◽  
pp. 2369-2373
Author(s):  
Gui Min Yin ◽  
Zhan Guo Li ◽  
Meng Li
Keyword(s):  
Output Power ◽  
Cutting Speed ◽  
Technological Parameters ◽  
Impulse Frequency ◽  
Scanning Velocity ◽  
Optimization Study ◽  
Cutting Surface ◽  
Two Factors ◽  
Single Factor Experiment

Using high power Nd3+:YAG pulse laser for precision cutting stainless sheet, study the effects of the laser cutting technological parameters on quality of cutting surface and joint-cutting width. The data of single factor experiment proved： With the increasing of scanning velocity, the joint-cutting width decreased; the width increased with the increasing of scanning velocity, laser current, impulse frequency and impulse width; the increasing of impulse frequency may improve the processing quality and ultimate cutting speed; the data of two-factors experiment proved: when the output power and impulse width are fixed, the impulse frequency will be increased, the joint-cutting width will be decreased; when the output power and impulse frequency are fixed, the impulse width will be increased, the joint-cutting width will be decreased.

scholarly journals Stressed state simulation of discrete abrasive disk cutting surface

2017 ◽  
Vol 2 (10) ◽  
pp. 18-23
Author(s):  
Алексей Морозов ◽  
Aleksey Morozov ◽  
Владимир Гусев ◽  
Vladimir Gusev
Keyword(s):  
Stressed State ◽  
High Frequency ◽  
Central Hole ◽  
Vibration Level ◽  
Cutting Surface ◽  
Abrasive Disk ◽  
Simulation Results ◽  
Thermal Intensity ◽  
Positive Effect

Grinding disks with high frequency discretization of a cutting surface allow not only breaking a cutting process and de-creasing its thermal intensity, but decreasing a vibration level of a technological system which has a positive effect upon quality of a surface worked. But, for realization of intensive grinding modes these tools should possess a mechanical strength not only in the central hole, but that of a discrete cutting surface. In this connection in modern CAE-complex CosmosWorks a computer simulation of a stressed state of a cutting surface and a central hole of the grinding disk subjected to a high-frequency discretization is carried out. On the basis of the simulation results there is developed a durable tool allowing the fulfillment of discrete grinding in intensive modes.

scholarly journals The role of an objective function in the mathematical modelling of wide-angle X-ray diffraction curves of semi-crystalline polymers

2021 ◽  
Vol 77 (6) ◽  
Author(s):  
Małgorzata Rabiej ◽  
Stanisław Rabiej
Keyword(s):  
Objective Function ◽  
Polyvinylidene Fluoride ◽  
Least Squares Method ◽  
Statistical Tests ◽  
Crystalline Polymer ◽  
Polyamide 6 ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
X Ray

To decompose a wide-angle X-ray diffraction (WAXD) curve of a semi-crystalline polymer into crystalline peaks and amorphous halos, a theoretical best-fitted curve, i.e. a mathematical model, is constructed. In fitting the theoretical curve to the experimental one, various functions can be used to quantify and minimize the deviations between the curves. The analyses and calculations performed in this work have proved that the quality of the model, its parameters and consequently the information on the structure of the investigated polymer are considerably dependent on the shape of an objective function. It is shown that the best models are obtained employing the least-squares method in which the sum of squared absolute errors is minimized. On the other hand, the methods in which the objective functions are based on the relative errors do not give a good fit and should not be used. The comparison and evaluation were performed using WAXD curves of seven polymers: isotactic polypropylene, polyvinylidene fluoride, cellulose I, cellulose II, polyethylene, polyethylene terephthalate and polyamide 6. The methods were compared and evaluated using statistical tests and measures of the quality of fitting.

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