Design of a Novel Variable Stiffness Series Elastic Actuator for Extended Linearity

Recently, Series Elastic Actuator (SEA) has been popularly used as a torque sensor thanks to its notable ability to calibrate the relation between torque and displacement. It has been applied to many robotic applications and used in a various industrial automation fields. However, most of the current SEAs have nonlinear torque-displacement characteristics which could not be easily alleviated. In order to be utilized as a feasible torque sensor, the wide linearity of a SEA in torque-displacement relationship is not an option. Also, adjustable compliance is needed to implement a mechanism with different stiffness, depending on the various cases where SEA can be applied. In this paper, we designed a Variable Stiffness Linear Series Elastic Actuator (VLSEA) mechanism that can achieve variable stiffness with a linear relationship between torque and displacement. At first, a design with a four-bar link was proposed for linear relations, but it was difficult to implement variable stiffness. We modified the design using the Scotch Yoke mechanisms for the model to have variable stiffness. Simulation of the designed model then verifies that the model can properly implement linearity and variable stiffness.

Failure Detection for Multiple Micro-Punches Outfitted in Progressive Piercing Processes With Artificial Intelligent Model

The purpose of this study is to establish a model for the diagnosis of multiple micro-punch failures. The punch is assumed to a rigid body structure with a small change in the stiffness during the piercing process and its diameter is varied between Ø0.8–1.2 mm. Thus, the wearing trend of multiple punches in the piercing process and source of the interfered signals make it extremely difficult to analyze. The two major challenges that affect punch failure estimation are the poor signal-to-noise ratio within the factory environment and the rigid body mode disturbance in the signal. To acquire the vibratory signals of the piercing motion, uniaxial accelerometers were outfitted in the vertical direction on the progressive die. Since the piercing process is a series of highly nonlinear transient processes, the Ensemble Empirical Mode Decomposition (EEMD) is adopted as a decoupling operation tool for this kind of non-stationary signal. Furthermore, the dimension-reduced process can be manipulated by Intrinsic Mode Function (IMF) and a function representative of the feature is selected as the input for neural network model training. The training target is the most direct relationship with the product quality, the selected models are multi-layer perceptron and the back-propagation neural network (BPNN) of the error inversion algorithm. The artificial intelligence failure diagnosis of the piercing process is also realized.

Sound-Induced Vibration to Hard Disk Drive in a Data Storage Enclosure

The data read and write operation in a hard disk drive (HDD) relies on precision mechanical components, such as air bearing sliders, suspension, and piezo actuators. Many of those mechanical components are sensitive to mechanical disturbances. It is found that sound a disturbance (or airborne disturbance) increases the position error signal (PES), such that the tracking, following and seeking performance is compromised. For a data storage enclosure and server in a data center, cooling fans generate strong sound noise, resulting in degradation of the performance of HDDs. In this study, we showed that the PES degrades when placing a sound source next to the HDD, indicating that the sound-induced vibration links to the mechanical components inside the HDD. It is also found that the PES is very sensitive to the location of the sound source. A vibration model was built by finite element method (FEM). The simulation results were compared to experiments on a thin plate structure to explain this dependency on the location of sound source.

Design and Implementation of a High Accuracy Interpolation Encoder IC for Magnetic Sensor

The magnetic encoder (ME) always employs sensor passing through periodic and equal distance grating and then generates periodic quadrature scaling signals for displacement measurement. The phase is relative to the movement. To improve encoder accuracy or resolution, electronic interpolation technique had been developed to subdivide the phase of quadrature scaling signals. According to the trends, this paper proposed a specific method with excellent noise immunity characteristic and a complete calibration process to improve the accuracy of the system. The designed circuit is taped-out using TSMC 0.18-μm CMOS process, where the active area is 1643 μm × 1676 μm. The chip has the specification of 3.3 V supply voltage, 20 MHz clock frequency, and 0.0859 mW power consumption. The accuracy of the measurement system is 1.065um.

Platform Design for Characterizing Shear Force Produced by Magnetized Magnetorheological Fluid

In this paper we proposed a platform for measuring shear force of magnetorheological (MR) fluid by which the relationship of yield stress and magnetic flux density of specific material can be determined. The device consisted of a rotatable center tube in a frame body and the magnetic field was provided by two blocks of permanent magnets placed oppositely outside the frame body. The magnitude and direction of the magnetic field were manipulated by changing the distance of the two permanent magnets from the frame body and rotating the center tube, respectively. For determining the magnetic field of the device, we adopted an effective method by fitting the FEM (finite element method) result to the measured one and then rebuilt the absent components to approximate the magnetic field, which was hardly to be measured simultaneously as different device setup were required. With the proposed platform and analytical methods, the drawing shear force and the corresponding yield stress contributed by MR fluid could be evaluated in respect to the magnitude and direction of given magnetic flux density with acceptable accuracy for specific designing purposes without a large, complex, and expensive instrument.

Cost Effective On-Site Fault Diagnosis Home Appliance Using a Smart Phone and Support Vector Machine

One of the common rotating machines of the consumer electronics might be a washing machine. The rotating machinery normally suffers mechanical failures even during daily operations that results in poor performance or shortening lifetime of the machine. Therefore, engineers have been interested in the earliest fault diagnosis of the rotating machine. Existing fault diagnosis methods for rotating machines have used fast fourier transform (FFT) method in frequency domain to detect abnormal frequency. However, it is difficult to diagnose using the FFT method if the normal frequency components of the rotating machines overlaps with the fault frequencies. In this paper, sets of acoustic signals generated by the washing machines are collected by using a smart phone in which an inexpensive microphone is equipped, and collected data are analyzed using a new algorithm, which combining the skewness, kurtosis, A-weighting filter, high-pass filter (HPF), and FFT. The analyzed data is applied to support vector machine (SVM) to determine defect existence. The proposed algorithm solves the disadvantages of the existing method and is accurate enough to discriminate the data collected by the cheap microphone of the smart phone.

Deposition of Highly Transparent and Conductive Films on Tilted Substrates by Atmospheric Pressure Plasma Jet

We study the influence of the substrate tilt angle on the microstructure and optoelectronic properties of gallium-doped zinc oxide (GZO) thin films deposited by the atmosphere pressure plasma jet (APPJ) method. The nozzle trajectories play a key role in oblique angle deposition. In the process of oblique angle deposition, if the nozzle scanned from the upstream side to the downstream side, the electrical properties such as resistivity, carrier concentration and mobility deteriorate considerably. The optical properties also worsen — specular transmittance goes down and diffuse transmittance increase to a significant amount. This degradation can be attributed to the “pre-deposition” of the GZO adsorbed particles (ad-particles) on the downstream side of the raw glass where the nozzle has not scanned. These GZO ad-particles serve as nuclei on which the incoming vapor particles deposit preferentially. Scanning electron microscopy (SEM), and grazing incidence X-ray diffraction (GIXRD confirmed that the film near the downstream is thicker, less smooth, and porous than that near the upstream. The undesirable situation can be mitigated or even completely removed via proper nozzle scanning trajectories — reversing the scanning trajectory of the nozzle. If the nozzle scans from the downstream side to the upstream side, no pre-deposition of the GZO ad-particles to deteriorate the film properties and therefore the obliquely deposited films perform as well as the films deposited without tilt, i.e. flat substrate. This work presents a solution to the challenge of depositing TCO on tilted and curved surfaces.

Application of Code Division Multiple Access Technology in Readout Circuit and System Design for an Ultra-Thin On-Cell Flexible Capacitive Touch Panel

A capacitive sensing circuit including electrodes for a 7-inch ultra-thin flexible on-cell touch panel has been designed. Implementing code-division multiple sensing (CDMS) with Walsh transform to scan Tx electrodes is chosen to improve the signal-to-noise ratio (SNR). The algorithm applies to field programmable logic array (FPGA). The sensing readout algorithm is applied to work on 4 Tx transmitter electrodes and 4 Rx sensing electrodes. The switched-capacitor (SC) circuit is applied to avoid disturbing sample signal from parasitic capacitance and enlarge the voltage difference from capacitance changes of the touch panel. 12-bit ADC to transfer the front-end analog signal to digital code. The digital part adopts a correction algorithm to eliminate the background value of the panel, the moving average algorithm has an adjustable signal-to-noise ratio function, and the Walsh conversion demodulation algorithm improves the touch report rate to achieve high SNR with up-to 34 dB.

Development of a Portable Reader for an Optical Intraocular Pressure Sensor

This paper presents various designs of a handheld reader for an interferometric intraocular pressure measurement system. Reflected lights from the implanted sensor form interference fringes which can be captured using a camera. Image processing software was used to analyze the fringe pattern and determine the eye pressure. Various light sources were considered and the LED with a laser line filter was selected for its ability to generate quality fringe patterns and portability. Three generations of handheld readers have been developed and tested. Interference patterns acquired from each reader were compared to assess the limiting and promising features related to measurement time, form factor, working distance, ease of use, and quality of fringes. Results show that the DSLR-based reader has the highest quality images with the largest form factor while the smartphone-based reader offers the smallest form factor with ease of use and accessibility for the patient.

Investigation of Zinc-Silver Oxide-Thermoplastic Composite for Application in a Biofilm Retardant Urinary Catheter

Catheter acquired urinary tract infection (CAUTI) is a significant problem in the medical community. Interdisciplinary teams have coordinated to address this problem, yet there is still a need for an adequate solution. In this study, we investigate an electricidal solution by adopting electrochemically active materials that can be incorporated into a urinary catheter. Zinc and silver oxide powders deposited in the form of patterned electrodes on a thermoplastic substrate are shown to illustrate electricidal properties in urine, including the ability to produce electric fields, pH increases, as well as, formation of hydrogen peroxide. The newly developed samples show promising results for killing planktonic E. coli in a controlled setting.