Wearable posture measurement units are capable of enabling real-time performance evaluation and providing feedback to end users. This paper presents a wearable feedback prototype designed for freestyle swimming with focus on trunk rotation measurement. The system consists of a nine-degree-of-freedom inertial sensor, which is built in a central data collection and processing unit, and two vibration motors for delivering real-time feedback. Theses devices form a fundamental body area network (BAN). In the experiment setup, four recreational swimmers were asked to do two sets of 4 x 25m freestyle swimming without and with feedback provided respectively. Results showed that real-time biofeedback mechanism improves swimmers kinematic performance by an average of 4.5% reduction in session time. Swimmers can gradually adapt to feedback signals, and the biofeedback control system can be employed in swimmers daily training for fitness maintenance.
Intrabody communication (IBC) is a promising data communication technique for body area networks. This short-distance communication approach uses human body tissue as the medium of signal propagation. IBC is defined as one of the physical layers for the new IEEE 802.15.6 or wireless body area network (WBAN) standard, which can provide a suitable data rate for real-time physiological data communication while consuming lower power compared to that of radio-frequency protocols such as Bluetooth. In this paper, impulse radio (IR) IBC (IR-IBC) is examined using a field-programmable gate array (FPGA) implementation of an IBC system. A carrier-free pulse position modulation (PPM) scheme is implemented using an IBC transmitter in an FPGA board. PPM is a modulation technique that uses time-based pulse characteristics to encode data based on IR concepts. The transmission performance of the scheme was evaluated through signal propagation measurements of the human arm using 4- and 8-PPM transmitters, respectively. 4 or 8 is the number of symbols during modulations. It was found that the received signal-to-noise ratio (SNR) decreases approximately 8.0 dB for a range of arm distances (5–50 cm) between the transmitter and receiver electrodes with constant noise power and various signal amplitudes. The SNR for the 4-PPM scheme is approximately 2 dB higher than that for the 8-PPM one. In addition, the bit error rate (BER) is theoretically analyzed for the human body channel with additive white Gaussian noise. The 4- and 8-PPM IBC systems have average BER values of 10−5 and 10−10, respectively. The results indicate the superiority of the 8-PPM scheme compared to the 4-PPM one when implementing the IBC system. The performance evaluation of the proposed IBC system will improve further IBC transceiver design.
Temperature-dependent fluorescence of YAG:Ce was studied as an example of a spectral characterization method. According to the steady-state emission at various temperatures, four types of temperature sensing functions were retrieved using behaviors of 1) wavenumber at emission band maximum magnitude, 2) wavenumber of emission band barycenter, 3) emission bandwidth, and 4) the ratio of intensities at different wavelengths in the emission band. All four types of functions demonstrate a near linear relationship with temperature in the measured temperature range. Function No. 2 shows finer precision than function No. 1, while they have the same meaning in physics. Mechanisms of the temperature dependence are discussed after a brief review of emission peak shifts of Ce 3+ -doped garnets. Function No. 3 shows an abnormal narrowing of the band with increasing temperature which can be related to the narrowing ground levels' splitting gap. In the experiment, the two novel spectral characterization methods showed their advantages: the barycenter technique contains the smallest uncertainty, and the self-referenced intensity ratio technique provides flexible ratiometric sensing functions for various measurement needs. Seshadri, "Rapid microwave preparation of highly efficient Ce 3+ -substituted garnet phosphors for solid state white lighting," Chem. Mater. 24(6), 1198-1204 (2012). 10. S. P. Ying, P. T. Chou, and H. K. Fu, "Influence of the temperature dependent spectral power distribution of light-emitting Diodes on the illuminance responsivity of a photometer," Opt. Lasers Eng. 51(10), 1179-1184 (2013). Defects Solids 158(1-6), 39-47 (2003). 14. M. Grinberg, "High pressure spectroscopy of rare earth ions doped crystals -new results," Opt. Mater. 28(1-2), 26-34 (2006) 8-12 (2015).
Intrabody communications (IBC) is a novel communication technique which uses the human body itself as the signal propagation medium. This communication method is categorized as a physical layer of IEEE 802.15.6 or Wireless Body Area Network (WBAN) standard. It is significant to investigate the IBC systems to improve the transceiver design characteristics such as data rate and power consumption. In this paper, we propose a new IBC transmitter implementing pulse position modulation (PPM) scheme based on impulse radio. A FPGA is employed to implement the architecture of a carrierfree PPM transmission. Results demonstrate the data rate of 1.56 Mb/s which is suitable for the galvanic coupling IBC method. The PPM transmitter power consumption is 2.0 mW with 3.3 V supply voltage. Having energy efficiency as low as 1.28 nJ/bit provides an enhanced solution for portable biomedical applications based on body area networks.
Accurate measurement of hand forces in motorbike riding is highly desirable for studies of safe riding. In this paper, we implement a force-sensing glove system for measuring real-time hand forces during motorbike riding with the aim of giving feedback to the riders. It consists of a pair of gloves with tactile sensors suitably mounted and configured for data acquisition via a wireless smartphone. A novel calibration method is developed for dynamic calibration considering force measurement in natural operation and environments. Consequently, a series of data classification algorithms ensure accurate hand performance feedbacks for motorbike riders. The feedback data could potentially alert the riders to predict and prevent accidents. Validation tests demonstrate that this force-sensing glove system has a strong potential as a tool for hand performance monitoring in real environment.
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