In recent times, personal mobile devices have become an integral part of daily life. However, since these devices typically demand prolonged durations of focus, they adversely affect a user's blinking rate. Blinking is an essential function of the eye that spreads tears, and thereby, helps avoid eye dryness and soreness. Several blink detection methods have been proposed, however, these methods are unable to effectively monitor involuntary blinks when the camera frame rate is low. To address this issue, this paper proposes a blink detection method for a real-time vision system implemented on the devices that dynamically change the frame rate of the built-in camera according to the usage environment. In the proposed method, the location of eyes is determined and an open-eye template is created by image differencing the initial blinks of the user. Subsequently, the eye is tracked by template matching using the open-eye template in each frame. During eye tracking, the correlation score is analyzed and thresholded with a criterion in order to detect closed eyelids at each frame. Several-frames-of-moving-averaged value of highest correlation score at each frame is used as the threshold value with an offset. In the experimental evaluation, the proposed blink detection method was implemented on a laptop-PC. A total of more than 10,000 true blinks from twenty-three test subjects yielded detection accuracies of 92.2 and 90.1% at 30 and 6 fps frame rate, respectively.
This paper presents a method for walking assist control that uses an inertial measurement unit (IMU) sensor fixed to an elderly person's foot to estimate his or her walking motion. In the proposed approach, a mobile device is synchronously driven by the user's walking motion. Furthermore, a manipulator mounted on the mobile device can support and help the user walk. These functions make it possible for the device to move beside the user and coordinate with his or her steps. The validity of the proposed approach was confirmed through several experiments.
Loss minimization is vital in high-power choppers for electric drive systems in automobiles. This paper describes the evaluation of partial turn-off behavior in IGBTs (Insulated Gate Bipolar Transistor) by ZVS (Zero Voltage Switching) without over-elimination based on Partial SAZZ (Snubber Assisted Zero Voltage and Zero Current Transition). High power BTB (back to back) experiments using a 90kW 3-phase interleaved chopper derived the good characteristics of the Partial SAZZ method and compared them with those of the hard switching (Hard SW) method. The total switching loss of the main circuit, which accounted for 48% (674W) in Hard SW, reduced to 192W, a 72% reduction, in Partial SAZZ. The Partial SAZZ method obtained the highest efficiency of 97.42% at 30kW, 1.82% higher than Hard SW (95.6%) and the highest efficiency over the entire power region. This was verified through a load test and loss breakdown of up to 30kW per phase.
A novel integrated magnetic structure suitable for a transformer-linked interleaved boost chopper circuit is proposed in this paper. Coupled inductors with high coupling are known to be effective for downsizing magnetic components. However, it is difficult to obtain the optional leakage inductance with high coupling for coupled inductors with EE or EI cores because of the fringing effect in the air gap. In order to overcome this problem, a novel integrated magnetic structure is first proposed. Then, a design method for the coupled inductor with the proposed magnetic structure is introduced on the basis of the magnetic circuit model. Finally, the effectiveness of the novel magnetic core structure is validated and discussed from an experimental viewpoint.