Acoustical boundary hologram for macroscopic rigid-body levitation.

In previous studies, acoustical levitation in the far-field was limited to particles. Here, this paper proposes the "boundary hologram method," a numerical design technique to generate a static and stable levitation field for macroscopic non-spherical rigid bodies larger than the sound wavelength λ. This paper employs boundary element formulation to approximate the acoustic radiation force and torque applied to a rigid body by discretizing the body surface, which is an explicit function of the transducer's phase and amplitude. Then, the drive of the phased array is numerically optimized to yield an appropriate field that stabilizes the body's position and rotation. In experiments, this paper demonstrates the levitation in air of an expanded polystyrene sphere with a diameter of 3.5 λ and a regular octahedron with diagonal length of 5.9 λ, both located 24 λ from the acoustic elements, by a 40 kHz (λ = 8.5 mm) ultrasonic phased array. This method expands the variety of objects that can be levitated in the far-field of an ultrasonic phased array.

Inter-IC for Wearables (I2We): Power and Data Transfer Over Double-Sided Conductive Textile.

We propose a power and data transfer network on a conductive fabric material based on an existing serial communication protocol, Inter-Integrated Circuit (I2C). We call the proposed network inter-IC for wearables. Continuous dc power and I2C-formatted data are simultaneously transferred to tiny sensor nodes distributed on a double-sided conductive textile. The textile comprises two conductive sides, isolated from each other, and is used as a single planar transmission line. I2C data are transferred along with dc power supply based on frequency division multiplexing. Two carriers are modulated with the clock and the data signals of I2C. A modulation and demodulation circuit is designed such that off-the-shelf I2C-interfaced sensor ICs can be used. The novelty of this paper is that a special filter to enable passive modulation is designed by locating its impedance poles and zeros at the appropriate frequencies. The term "passive modulation" herein implies that the sensor nodes do not generate carrier waves by themselves; instead, they reflect only the externally supplied careers for modulation. The proposed scheme enables the flexible implementation of wearable sensor systems in which multiple off-the-shelf tiny sensors are distributed throughout the system.

Body Sensor Networks Powered by an NFC-Coupled Smartphone in the Pocket.

This paper proposes a body sensor network (BSN) on clothing that is wirelessly powered by a smartphone in a pocket. The network consists of a host device and multiple sensor nodes, which are distributed on a wear and are electrically connected with conductive threads. The smartphone with a built-in near field communication (NFC) feature powers the host, which is fixed at the pocket. These devices are wired to a special cloth embroidered with conductive threads by using a special connector consisting of a pin & socket without one-to-one wiring. In the proposed BSN, the host device and the smartphone are coupled via NFC radio within the pocket. Energy harvesting with NFC radio wave requires maintaining antennas within several centimeters to obtain enough power. Positioning and fixing of the smartphone is required within the pocket. A proposed host device can expand the range of energy harvesting by using multiple antennas and a power aggregation circuit. The experimental results demonstrate the feasibility of the batteryless BSNs system.

Development of a Sensor Network System with High Sampling Rate Based on Highly Accurate Simultaneous Synchronization of Clock and Data Acquisition and Experimental Verification †.

In this paper, we develop a new sensor network system with a high sampling rate (over 500 Hz) based on the simultaneous synchronization of clock and data acquisition for integrating the data obtained from various sensors. Hence, we also propose a method for the synchronization of clock and data acquisition in the sensor network system. In the proposed scheme, multiple sensor nodes including PCs are connected via Ethernet for data communication and for clock synchronization. The timing of the data acquisition of each sensor is locally controlled based on the PC's clock locally provided in the node, and the clocks are globally synchronized over the network. We construct three types of high-speed sensor network systems using the proposed method: the first one is composed of a high-speed tactile sensor node and a high-speed vision node; the second one is composed of a high-speed tactile sensor node and three acceleration sensor nodes; and the last one is composed of a high-speed tactile sensor node, two acceleration sensor nodes, and a gyro sensor node. Through experiments, we verify that the timing error between the sensor nodes for data acquisition is less than 15 µs, which is significantly smaller than the time interval of 2 ms or a shorter sampling time (less than 2 ms). We also confirm the effectiveness of the proposed method and it is expected that the system can be applied to various applications.

Synchronized High-Speed Vision Sensor Network for Expansion of Field of View.

We propose a 500-frames-per-second high-speed vision (HSV) sensor network that acquires frames at a timing that is precisely synchronized across the network. Multiple vision sensor nodes, individually comprising a camera and a PC, are connected via Ethernet for data transmission and for clock synchronization. A network of synchronized HSV sensors provides a significantly expanded field-of-view compared with that of each individual HSV sensor. In the proposed system, the shutter of each camera is controlled based on the clock of the PC locally provided inside the node, and the shutters are globally synchronized using the Precision Time Protocol (PTP) over the network. A theoretical analysis and experiment results indicate that the shutter trigger skew among the nodes is a few tens of microseconds at most, which is significantly smaller than the frame interval of 1000-fps-class high-speed cameras. Experimental results obtained with the proposed system comprising four nodes demonstrated the ability to capture the propagation of a small displacement along a large-scale structure.