A Simplified Dynamic Model for the Analysis of the Slider Off-Track Motion Due to Head-Disk Interactions

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Yanhui Yuan ◽  
Shao Wang
Keyword(s):  
Contact Force ◽  
Rotational Speed ◽  
Disk Drive ◽  
Roll Angle ◽  
Transverse Motion ◽  
Transverse Displacement ◽  
Skew Angle ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Displacement Based

A five-degree-of-freedom model was developed for the analysis of the off-track motion of the magnetic head slider in a hard disk drive. The air bearing was integrated into the dynamic system by combining its stiffness and damping matrices with those of the suspension. Simulation was conducted for the slider in intermittent contact with circumferentially located bumps on a rotating magnetic disk. For a single bump, the excitation to the transverse displacement of the slider is close to that of an impulse. However, for multiple bumps in a sequence, the excitation gives an effect similar to that of a step force function. The maximum transverse displacement increases almost linearly with both the coefficient of friction and the skew angle. The average contact force is determined by the maximum contact force, the contact time ratio, and the shape factor of the contact force, which change with the bump spacing and the rotational speed of the disk. The steady-state transverse displacement is related to the average contact force. As the bump spacing decreases, the average contact force increases, resulting in a greater transverse displacement. Based on the system dynamic characteristics alone, changing the rotational speed of the disk has only a small impact on the average contact force and, thus, on the transverse displacement. At zero skew angle with the bump path close to a rear pad edge, significant transverse motion occurs because of the excited roll mode and the coupling between the roll angle and the transverse displacement. The off-track motion of the slider is dominated by the rotational mode of the actuator arm and the sway mode of the suspension, as verified by comparing the results of the transverse displacement from the 5DOF model to that from a 2DOF model of the transverse motions of the actuator arm and suspension. The effects of the roll angle on the transverse displacement through coupling were found to be responsible for the difference in the transverse displacements obtained from the two models.

A Near Zero Skew Actuation Mechanism for Hard Disk Drives

2013 ◽  
Author(s):  
Zhimin He ◽  
Jianqiang Mou ◽  
Kheong Sann Chan ◽  
Suet Hoi Lam ◽  
Boon Long See ◽  
...  
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Disk Drive ◽  
Outer Diameter ◽  
Disk Drives ◽  
Skew Angle ◽  
Link Mechanism ◽  
Tracking Direction ◽  
The Difference ◽  
Zero Skew

One of the issues in VCM rotary actuation in hard disk drives (HDDs) is the excessive sensitivity of the system to the skew angle. The rotation of the VCM from the inner diameter (ID) to the outer diameter (OD) of the disk results in an angle of skew between the read/write head and the track. The difference in skew angle, between the ID to the OD can be as large as 25 to 30 degrees in conventional 3.5″ and 2.5″ HDDs. A large skew angle affects the slider’s flying performance and off-track capability, causing an increase in side reading and writing, and thus reduces the achievable recording density. Large skewed actuation also complicates the position error signal calibration process in the hard disk drive servo loop. This paper presents a 4 link mechanism which can be designed to achieve near zero skew actuation in hard disk drives. The profiles of the arm, suspension, and links can be designed and optimized such that the skew angle is close to zero while the VCM actuator rotates from the ID to the OD. Study shows that the 4-link mechanism does not degrade the resonance performance along the tracking direction compared to a conventional actuator.

scholarly journals Suppress Vibration on Robotic Polishing with Impedance Matching

Actuators ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 59
Author(s):  
Junjie Dai ◽  
Chin-Yin Chen ◽  
Renfeng Zhu ◽  
Guilin Yang ◽  
Chongchong Wang ◽  
...  
Keyword(s):  
Contact Force ◽  
Force Control ◽  
Impedance Control ◽  
Impedance Matching ◽  
Industrial Robots ◽  
Contact Phase ◽  
Dynamic Tracking ◽  
Force Tracking ◽  
The Difference ◽  
End Effectors

Installing force-controlled end-effectors on the end of industrial robots has become the mainstream method for robot force control. Additionally, during the polishing process, contact force stability has an important impact on polishing quality. However, due to the difference between the robot structure and the force-controlled end-effector, in the polishing operation, direct force control will have impact during the transition from noncontact to contact between the tool and the workpiece. Although impedance control can solve this problem, industrial robots still produce vibrations with high inertia and low stiffness. Therefore, this research proposes an impedance matching control strategy based on traditional direct force control and impedance control methods to improve this problem. This method’s primary purpose is to avoid force vibration in the contact phase and maintain force–tracking performance during the dynamic tracking phase. Simulation and experimental results show that this method can smoothly track the contact force and reduce vibration compared with traditional force control and impedance control.

scholarly journals The Effect of Co-Deposition of SiC Sub-Micron Particles and Heat Treatment on Wear Behaviour of Ni–P Coatings

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 180
Author(s):  
Donya Ahmadkhaniha ◽  
Lucia Lattanzi ◽  
Fabio Bonora ◽  
Annalisa Fortini ◽  
Mattia Merlin ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Friction Coefficient ◽  
Wear Mechanisms ◽  
Composite Coatings ◽  
Wear Behaviour ◽  
Maximum Hardness ◽  
Sic Particles ◽  
Heat Treated ◽  
The Coefficient Of Friction ◽  
The Difference

The purpose of the study is to assess the influence of SiC particles and heat treatment on the wear behaviour of Ni–P coatings when in contact with a 100Cr6 steel. Addition of reinforcing particles and heat treatment are two common methods to increase Ni–P hardness. Ball-on-disc wear tests coupled with SEM investigations were used to compare as-plated and heat-treated coatings, both pure and composite ones, and to evaluate the wear mechanisms. In the as-plated coatings, the presence of SiC particles determined higher friction coefficient and wear rate than the pure Ni–P coatings, despite the limited increase in hardness, of about 15%. The effect of SiC particles was shown in combination with heat treatment. The maximum hardness in pure Ni–P coating was achieved by heating at 400 °C for 1 h while for composite coatings heating for 2 h at 360 °C was sufficient to obtain the maximum hardness. The difference between the friction coefficient of composite and pure coatings was disclosed by heating at 300 °C for 2 h. In other cases, the coefficient of friction (COF) stabilised at similar values. The wear mechanisms involved were mainly abrasion and tribo-oxidation, with the formation of lubricant Fe oxides produced at the counterpart.

scholarly journals Experimental Study on the Transition between Static and Kinetic Frictions of Steel/Shale Pairs

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qin Lian ◽  
Chunxu Yang ◽  
Jifei Cao
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Critical Distance ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Dynamic Friction Coefficient ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Stick Slip Motion ◽  
Insight Into

The transition between static and kinetic frictions of steel/shale pairs has been studied. It was found that the coefficient of friction decreased exponentially from static to dynamic friction coefficient with increasing sliding displacement. The difference between static and dynamic friction coefficients and the critical distance Dc under the dry friction condition is much larger than that under the lubricated condition. The transition from static to dynamic friction coefficient is greatly affected by the normal load, quiescent time, and sliding velocity, especially the lubricating condition. Maintaining continuous lubrication of the contact area by the lubricant is crucial to reduce or eliminate the stick-slip motion. The results provide an insight into the transition from static to dynamic friction of steel/shale pairs.

scholarly journals The Influence of Water and Mineral Oil On Volumetric Losses in a Hydraulic Motor

2017 ◽  
Vol 24 (s1) ◽  
pp. 213-223 ◽  
Author(s):  
Pawel Śliwiński
Keyword(s):  
Mathematical Model ◽  
Rotational Speed ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Mineral Oil ◽  
Hydraulic Motor ◽  
Small Constant ◽  
Influence Of Water ◽  
The Difference ◽  
Lubricating Properties

Abstract In this paper volumetric losses in hydraulic motor supplied with water and mineral oil (two liquids having significantly different viscosity and lubricating properties) are described and compared. The experimental tests were conducted using an innovative hydraulic satellite motor, that is dedicated to work with different liquids, including water. The sources of leaks in this motor are also characterized and described. On this basis, a mathematical model of volumetric losses and model of effective rotational speed have been developed and presented. The results of calculation of volumetric losses according to the model are compared with the results of experiment. It was found that the difference is not more than 20%. Furthermore, it has been demonstrated that this model well describes in both the volumetric losses in the motor supplied with water and oil. Experimental studies have shown that the volumetric losses in the motor supplied with water are even three times greater than the volumetric losses in the motor supplied with oil. It has been shown, that in a small constant stream of water the speed of the motor is reduced even by half in comparison of speed of motor supplied with the same stream of oil.

scholarly journals Investigation on Flooding-Resistant Performance of Integral Abutment and Jointless Bridge

2020 ◽  
Vol 2020 ◽  
pp. 1-25
Author(s):  
Yizhou Zhuang ◽  
Keyao Wu ◽  
Liang Xu ◽  
Huihui Li ◽  
Diego Maria Barbieri ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Plastic Hinge ◽  
Transverse Displacement ◽  
Integral Abutment ◽  
Skew Angle ◽  
Element Analysis ◽  
Water Blocking ◽  
Load Tests ◽  
Bridge Performance ◽  
Jointless Bridge

Bridge washouts connected to flood events are deemed one of the main reasons for structural collapse. Compared to traditional continuous jointed bridges, integral abutment and jointless bridges (IAJBs) have better lateral stability because there are no expansion devices. The mechanical performance of Shangban IAJ bridge, located in Fujian, China, is thoroughly investigated by Finite Element Analysis (FEA). The numerical model is created and validated based on experimental results obtained from static load tests performed on the bridge. A detailed parametric analysis is carried out to assess the correlation between the flood-resistant performance and a number of parameters: skew angle, water-blocking area, span number, pile section geometry, and abutment height. Except for the abutment height, other parameters significantly affect the bridge performance. Furthermore, the change in the span number has a meaningful impact only when fewer than four spans are modeled. Finally, pushover analyses estimate the maximum transverse displacement and the sequence of plastic hinge creation as well as the mechanical behaviour of the structure under lateral flood loads. The analysis results show that IAJBs have better flooding-resistant performance than conventional jointed bridges.

scholarly journals Tribology behaviour investigation of 3D printed polymers

2019 ◽  
Vol 10 (2) ◽  
pp. 173-181
Author(s):  
Muammel M. Hanon ◽  
Márk Kovács ◽  
László Zsidai
Keyword(s):  
Acrylonitrile Butadiene Styrene ◽  
Poly Lactic Acid ◽  
Fused Deposition Modelling ◽  
Tribological Behaviour ◽  
Fused Deposition ◽  
Motion System ◽  
Friction Factors ◽  
The Coefficient Of Friction ◽  
3D Printed ◽  
The Difference

3D printing of Acrylonitrile Butadiene Styrene (ABS) and Poly Lactic Acid (PLA) were used to prepare specimens utilising fused deposition modelling (FDM) technology. Two colours of PLA filament were printed; white and grey, whereas ABS only in white colour. Determining the tribological properties of 3D printed samples have been carried out, through obtaining the frictional features of different 3D printable filaments. Alternating-motion system employed for measuring the tribological factors. Studying the difference between static and dynamic friction factors and the examination of wear values were included. A comparison among the tribological behaviour of the 3D printed polymers has been investigated. The printed white ABS and PLA specimens show insignificant differences in the results tendency. On the contrary, the grey PLA exhibits a considerable variation due to the incredible growth in the coefficient of friction and wear average as well.

scholarly journals Empirical Modelling of Hydrodynamic Effects on Starch Nanoparticles Precipitation in a Spinning Disc Reactor

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2202 ◽  
Author(s):  
Sahr Sana ◽  
Vladimir Zivkovic ◽  
Kamelia Boodhoo
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Rotational Speed ◽  
Precipitation Process ◽  
Empirical Modelling ◽  
Operating Variables ◽  
Antisolvent Precipitation ◽  
Passive Mixing ◽  
The Difference ◽  
Spinning Disc

Empirical correlations have been developed to relate experimentally determined starch nanoparticle size obtained in a solvent–antisolvent precipitation process with key hydrodynamic parameters of a spinning disc reactor (SDR). Three different combinations of dimensionless groups including a conventional Reynolds number (Re), rotational Reynolds number (Reω) and Rossby number (Ro) have been applied in individual models for two disc surfaces (smooth and grooved) to represent operating variables affecting film flow such as liquid flowrate and disc rotational speed, whilst initial supersaturation (S) has been included to represent varying antisolvent concentrations. Model 1 featuring a combination of Re, Reω and S shows good agreement with the experimental data for both the grooved and smooth discs. For the grooved disc, Re has a greater impact on particle size, whereas Reω is more influential on the smooth disc surface, the difference likely being due to the passive mixing induced by the grooves irrespective of the magnitude of the disc speed. Supersaturation has little impact on particle size within the limited initial supersaturation range studied. Model 2 which characterises both flow rate and disc rotational speed through Ro alone and combined with Re was less accurate in predicting particle size due to several inherent limitations.

Identification of Contact Conditions from Contact Force and Moment - Experimental Verification in Effective Sensing Strategy -

2009 ◽  
Vol 21 (2) ◽  
pp. 236-244 ◽  
Author(s):  
Takayoshi Yamada ◽  
◽  
Tetsuya Mouri ◽  
Akira Tanaka ◽  
Nobuharu Mimura ◽  
...  
Keyword(s):  
Contact Force ◽  
Contact Line ◽  
Contact Conditions ◽  
Contact Type ◽  
Degree Of Separation ◽  
Direction Of Movement ◽  
Force Contact ◽  
The Difference ◽  
Contact Position ◽  
Small Eigenvalues

This paper discusses an effective sensing strategy for identification of contact conditions by using experiments. The contact conditions include contact position, contact force, contact type, direction of contact normal, and direction of contact line. To distinguish contact type more quickly and accurately, we must raise the degree of separation of large and small eigenvalues of a covariance matrix for estimating contact moment. Firstly, several sensing strategies are investigated through experiments. The difference of these strategies is the origin and direction of movement because the contact moment, which expresses the characteristic of contact type, is generated at a contact frame. Secondly, a more effective sensing movement is suggested from experimental results. Finally, it is pointed out that these strategies are related to sensing movement by a human being.

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