Jen-Yuan Chang

Modeling and development of tension force measurement system for cable-driven hand exoskeleton robot

With rapidly growing of aged and disabled population, insufficiency of medical care for those impaired patients, such as shortage of physical therapist has drawn much attention recently. The aim of this paper is devoted to investigation of how tension force in a cable-driven hand exoskeleton robot varies with different engagement of exoskeleton motion under the non-loading condition. A Lagrange model for the hand exoskeleton robot is derived and validated by careful mechatronic measurements with good agreement. Results from the present study suggest the proposed model can accurately estimate the variation profile of cable tension force with different engagement of metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints in the hand exoskeleton robot.

Enhancement in (002) texture of electroplated Co-based hard magnet layers

Electroplated hard magnet layers with out-of-plane performance play important roles in electro-mechanical devices. We designed to improve magnetic performance of electroplated Co-based hard magnet layer via the enhancement of HCP(002) texture using a thin seed-layer whose HCP(002) texture is intrinsically high. The seed-layer is either CoP or CoNiMnP fixed at 1μm thickness. Top hard magnet layers CoNiP and CoP with varied thickness were electroplated on top of the seed-layer. The results indicate that the improvement in out-of-plane magnetic properties of top layer is 38% to 100% in Br, 13% to 100% in Hc and 57% to 300% in (BH)max due to introduction of the seed-layer. The evolution in texture coefficient of HCP(002) of the top layer was quantitatively studied. The resultant magnetic properties correlate well with the induced texture coefficient.

Evaluation of Sheet Metal Leveling Based on Elimination of Coilset Residual Stress

Flexible media such as tape, web or sheet metal are commonly used in the mass production manufacturing. In the modern manufacturing process, about one third of the steel production is converted to sheet metal [1]. Sheet metal is normally winded and stored into coil form which can be easily tranported. However, when it is unwinded for metal forming process such as press stamping, laser cutting or any other forming process, sheet metal will have coilset residual stress which can cause defects from the forming process. The coilset residual stress is caused by the way the sheet metal is stored and packaged [2]. Therefore, in order to eliminate such residual stress, leveing process is carried out to eliminate common coilset residual stress.Copyright

Development of Integrated Roller Leveling System for Magnetic Encoding Medium Manufacturing

Magnetic linear encoder has been increasingly integrated in various position control system while demands for high precision machine tool to produce high precision products increase. During the manufacture of magnetic encoding medium, the medium is not expected to be flat due to packaging induced plastic deformation and residual stress. Medium deformation will result in damaging the performance of the medium such as the accuracy and magnetic flux density distribution. In this paper, the research efforts are devoted to develop a roller leveling system to flatten the curved magnetic medium, validated by parameter studies to investigate how roller leveling can be integrated into the manufacture of magnetic encoding medium in order to improve mechanical deflection and residual stress. The mechanical design of the roller leveling cycles has been completed. Experimental results demonstrate that roller leveling can significantly improve mechanical deflection of pre-stressed curve magnetic medium up to almost 60%.Copyright

A Data Mining Approach for Diagnosis of Nonlinear Stochastic Dynamics of TFC Active Slider in Nano-Meter Spacing

Storage of 10 Tb/in2 in hard disk drives requires a physical spacing in the level of 0.25 nm at the read-write transducer location. A lot of physical and tribology issues exist to such a low flying height. At such a small spacing intermittent contact of solid-to-solid and solid-to-liquid between the slider and disk surface becomes inevitable, which motivates the improvement needs for the present MEMS-based thermal fly-height control (TFC) technology to satisfy the future storage needs. How to control slider to reduce touchdown instability and eventually eliminate bouncing has been a pressing and challenging research topic. There are many researches dedicated in addressing this challenging issue. For examples, the hysteresis, the influences of surface roughness and waviness, the lubricant modulation and uncertainty, and the nonlinear properties and identification have been investigated and examined in the literatures [1–9]. Knowledge obtained from the literatures concludes that the contact dynamics of slider involve strong nonlinearity and stochastic properties. By using FFT spectral analysis, existing research has clarified many nonlinear dynamics phenomena during touchdown. However, many more complicated phenomena such as narrowband and wideband frequency spectrum and the stochastic features of system response have yet clarified. The existing analytical and numerical researches have been centered on deterministic model analysis. The widely observed random properties of roughness and waviness of solid surfaces and modulation of lubricant have not been fully reflected in the analysis. Inherently not applicable to strong nonlinear and stochastic dynamics problems by classical FFT approach, this paper then proposes to develop a data mining-based approach to diagnosis the complex nonlinear stochastic dynamics of the TFC active slider at nano-meter spacing to the surface during touchdown event.Copyright

Mechatronic Integration of Magnetic Linear Encoding Medium Manufacturing

Linear encoder has been widely used in various position controls in industries, especially in machinery industry. The purpose of using linear encoders is to give precise position control in dynamic applications. Furthermore, using linear encoders helps minimize errors caused by human or mechanical problems such as backlash and thermal expansion [2]. There are various types of linear encoders such as mechanical, optical, magnetic, etc. Nevertheless, magnetic encoders are able to withstand harsh environment such as oil, grease, and dust much effective than the rest. Magnetic encoders have several advantageous qualities: low cost, fast response, and high reliability [1, 3]. Figure 1 shows the magnetic field of a magnetic scale where the yellow curves indicate the change of magnetic poles. The upper half of the scale is the incremental mark and the bottom half is the reference mark. Prior to magnetization, the scale has only the incremental mark, and the magnetizing process is to magnetize bottom half of the incremental mark into reference mark as shown in Fig. 1.Copyright

Intelligent Diagnosis of Bolting System Under Dynamic Impact

The properties of fasteners as significant parts in varied engineering systems have been widely investigated [1–3], from hard disk drive devices to construction ground control. These problems are complex in nature because every bolting involves different sources of nonlinear and uncertainty characteristics. The interfaces forces such as contact forces, friction forces and bonding are not known in reality. The base forces and deformation could be redistributed non-uniformly in the presence of complex loadings such as shock and impact. Most of the reported studies focused on the design issues, characterization of the linear dynamic properties and energy dissipation of bolting system as well as using bolts with integrated detecting systems or dynamometers. The capability to assess the interface properties of bolting system is important for mechatronics, mechanical, civil and mining engineering [1–4]. Even though some conventional approaches have been used to infer bolting integrity, the diagnosis technology has been lacking. This study is conducted to explore the possibility of the diagnosis bolting interface integrity under impact by using accelerometer signal. The statistical pattern identification such as artificial neural network and support vector machine is used to diagnose the bolting integrity. By integrating the analysis and experimental data, an ANN is established as a nonparametric model to predict the system properties. Numerous numerical and experimental researches have been conducted to characterize the typical bolting system, which enables extraction of varied dynamic features from different mechanisms associated with the failures. This kind of database could be used as feature to characterizing the effect of complex loads on bolting for ANN training. To further illustrate the feature extraction, we investigated system models. Due to its adaptive and nonlinear input–output transformation capabilities, artificial neural network (ANN) has been widely applied in the field of pattern and system recognition. The proposed approach is capable of monitoring the stress/strain history and integrity of bolting interface with the goal of detecting structural damage and defects. The results from simulation, testing and ANN identification demonstrated the high performance of the proposed approach compared with conventional ones. In the following, an approach is proposed to reliably estimate the dynamic properties of a bolt-surrounding solid mass specimen using its impact response signal. The developed approach can be readily extended to the bolting connection in other systems such as mechanical and mechatronics systems.Copyright

An Insight Into the Nonlinear Touchdown Dynamics of TFC Active Slider

Storage of 10 Tb/in 2 in hard disk drives within the next decade requires a significant change to reduce the physical spacing as little as 0.25 nm at the read-write transducer location. A lot of tribology issues exist to such a low flying height, the touch down and take off instability and hysteresis, the flying height avalanche, the influences of surface topography and morphology, the lubricant modulation and pick-up, robust air bearing surface and suspension design, just to name a few. Understandings of the complex tribo-dynamics issues in the near contact and contact states are very important to further reduce the flying height. At such a small spacing intermittent contact between the slider and disk surface becomes inevitable and the current MEMS-based thermal fly-height control (TFC) technology needs further improvement to satisfy the future needs. How to control the slider to reduce touchdown instability and eventually eliminate bouncing has been a pressing and challenging research topic. Most of existing work on touchdown dynamics applied conventional nonlinear dynamics theory and spectrum as well as harmonics analysis, which could suffer from the assumptions of small nonlinearity and stationary. This study presents a concurrence plot and Lyapunov exponent analysis which could offer an insight to the problem in the context of contemporary nonlinear dynamics theory.Copyright

Dynamics of Reader Head Suspension on a Magnetic Scale With Grooves

In machine tool industry, the current trend is to use magnetic scales instead of mechanical scales or optical scales for linear position identification and control. As the demand for more accurate precision in magnetic scale, more stable reading head suspension is thought. Magnetic media with grooves, such as patterned-media, are considered to achieve ultrahigh magnetic pitch density. Patterned-media consists of land parts for magnetized N pole and grooves parts for S pole. The higher magnetic pitch density on the media, the lower magnetic flux we can measure. In order to measure reliable magnetic flux signal, the distance between the media and reader head needs to be as close as possible. During the process, aerodynamics, which caused by the reader head passing through groove parts with tiny distance between reader head and media, have an impact on reader head suspension which leads to vibration and misjudgment of measured signals. In this paper, parameter studies are conducted with the goal placed on correlating response of certain suspension vibration modes to optimal parameters in reader head suspension design.Copyright

Reduction of flying height modulation of hybrid active slider — A nonlinear control approach

This paper is concerned with the issue of reduction of fly height vibration (modulation) associated with hybrid active slider which is driven by both thermal and piezoelectric actuators. Since the accurate system parameters are hard to obtain, a Lyapunov based nonlinear control approach is proposed to control the fly height modulation after a simplified system model is proposed. The controller only requires the bounds of the estimation errors of the selected system parameters and the feedback of selected system states, is thus simple in structure and efficient in real time application. The proof and verification of the effectiveness of proposed approach to reduce the fly height modulation is given.