Kosuke Harada

A new torque transducer using stress sensitive amorphous ribbons

A new torque transducer of the noncontact type employing the magnetostrictive effect is presented. In this torque transducer, two stress-sensitive amorphous ribbons are glued to a torsion bar which is used as a part of the shaft. Unidirectional magnetoelastic magnetic anisotropy is created in each ribbon in such a manner that one of the anisotropies lies along 45° to the shaft axis and another along -45°. The applied torque is detected as a difference in permeability between the amorphous ribbons by an ac bias field. The amorphous ribbon used in experiments is of Fe-Si-B system whose saturation magnetostriction \lambda_{s} \simeq 24\times10^{-6} and I_{s} \simeq 1.5 T. With this torque transducer, instantaneous torque as well as static torque is detected with sufficient accuracy. Due to the easy-to-mount structure, this torque transducer is well suited for the torque control application.

Torque transducers with stress-sensitive amorphous ribbons of chevron-pattern

In this paper, a simplified assembling method is presented by which a reliable and compact torque transducer exhibiting wide dynamic range and good linearity is obtained. The only modification applied to the shaft to obtain the torque transducer is to glue several pairs of stress-sensitive amorphous ribbons of rectangular form or of parallelogram form to the shaft in a chevron-pattern. Experiments are carried out on torque transducers with the nonmagnetic torsion bar to comfirm the theoretical prediction and with the magnetic steel torsion bar to examine the output characteristics and the dynamic response.

Balanced charging of series connected battery cells

Novel method of charging and discharging the battery cells serially connected is presented. The principle is the control of charge stored in respective cells by using electronic switches so that the voltages of respective cells may be balanced automatically. The circuit to realize this principle is essentially the same as that of the ringing choke converter for the DC-to-DC power converter which is the simplest of minimum number of components. The cell voltage being low from 1.2 V to 3.6 V, the trench type MOSFET for the synchronous rectifier is used as a switching element.

Noncontact torque sensors using magnetic heads and a magnetostrictive layer on the shaft surface - application of plasma jet spraying process

A noncontact torque sensor using magnetic heads and a magnetostrictive layer deposited uniformly on the shaft surface is presented. To realize the torque sensor, a new circuit is developed. Using a Ni layer deposited by the plasma jet spraying process, fundamental characteristics of the torque sensor are investigated, and possibility of detecting instantaneous value of the applied torque is demonstrated.

Generation of zero-level fluctuation and its reduction in the magnetic head type torque sensor with L-R bridge configuration

A theory is presented to describe the behavior of extrinsic zero-level fluctuations (ZLFs) for the magnetic-head-type torque sensor with L-R bridge configuration. A method for suppressing the extrinsic ZLF is derived from the theory. The method is demonstrated using an as-ground carbon steel (S45C in JIS) shaft of 12-mm diameter. It is found that the relationship between unbalances in the magnetic pickup and the generation of the external ZLF is well described by the theory. By combining the method for suppressing the extrinsic ZLF and surface processing of the shaft to reduce inhomogeneities, torque sensors for various control applications can be realized. >

Current sensors with a small saturable core and MOSFETs

Simple, noncontact-type current sensors for detecting instantaneous value of the current are reported. The sensor are especially suitable for DC-to-DC converters and uninterruptible power supplies. The circuits are based on the principle of the transistor-core multivibrator, in which MOSFETs are used for switching. Both theoretical and experimental results are given, showing that the sensors are practical. >

Controlled power-interface between solar cells and AC source

A novel interface circuit between solar cells and a commercial AC bus using Van Allens multivibrator is presented. In this circuit, the AC source is used for the backup of solar cells, and the source and load power flow is automatically balanced by the circuit itself without any external phase control. Based on an analysis of the characteristics of the oscillator, the authors describe a novel method to control the DC power from the solar cells according to the current load conditions as well as a simple and fast optimization method to derive the maximum solar power.<<ETX>>

Patterned growth of ZnO nanowalls by nanoparticle-assisted pulsed laser deposition

We have succeeded in controlling the growth density of ZnO nanowires synthesized by nanoparticle-assisted pulsed laser deposition (NAPLD) using a ZnO buffer layer and laser irradiation. The density of the nanowires decreased with increasing thickness of the buffer layer. In addition, the nanowire density also decreased by laser irradiation to the buffer layer. Patterned growth of ZnO nanowalls using NAPLD was successfully achieved with the help of the buffer layer patterned by interfering laser beams.

A new method of assembling a torque transducer by the use of bilayer-structure amorphous ribbons

Bilayer-structure amorphous ribbons consisting of different types of amorphous layers concerning magnetostrictive effect has possibility of realizing various kinds of force transducers. In this paper, a torque transducer is assembled using bilayer-structure amorphous ribbons formed by gluing separate amorphous ribbons prepared by the single roll quenching method. Experimental results show that the torque transducer so assembled is acceptable for practical applications.

A new thin pickup coil for magnetic head type torque sensors

A new thin pickup head is proposed for magnetic-head-type torque sensors. The new pickup head consists of a stacked pair of figure eight coils, in which one of the coils is rotated in the coil plane by 90 degrees from the other. The applied torque can be detected from the difference in self-inductances of a pair of the figure eight coils faced to the shaft through an air gap in a manner such that each figure eight coil sees the permeability of the shaft along either 45 degrees or -45 degrees from the axis. Unlike conventional pickup heads of 3-D structure, the proposed pickup head is thin, making it easy to build the torque sensor on a shaft. Experimental results using a magnetic yoke backing the pickup head show good linearity with small hysteresis. >