Aiming to realize the newly actuator without any electric cable, the use of laser-induced water vaper bubble has been proposed and performed the principle confirmation experiment. The laser induced water bubble has been applied for the liquid jet therapeutic catheter in medical field. The liquid jet system use physiologic saline for the liquid and a Ho: YAG laser of 2.1 µm wavelength that has highly absorption of water. Instead of this combination, we propose the use of carbon powder suspension for working liquid and an infrared Laser Diode (LD) of 970nm wavelength. As the 970nm LD light is not absorbed by water but carbon, the water of the working liquid could be vaporized by heated carbon. LD is considered as a suitable laser source for the actuator in the viewpoint of output controllability by the drive-current modulation. Figure 1 shows the conceptual image of the laser-induced water bubble actuator. It is constructed with a 970nm LD, an optical fiber and an actuator unit with working liquid for producing bubble.
An optical fiber connector (SMA connector) has been used for the bubble generator unit in our principle confirmation experiment. We use the inlet space for inserting and fixing fiber cable as the actuator cylinder. The working liquid was prepared by suspending carbon powder of 20µm particle size in water with surface active agent. After the working liquid has been injected in the cylinder, a stainless steel rod of Φ2.3mm diameter and 30mm length inserted as the actuator piston. When the laser irradiation was performed at the LD power of 160-180W and the pulse duration of 2msec, the reciprocating motions of the stainless steel rod have been observed.
For the next step, we are planning to evaluate the operating characteristic and also try to maximize the generating force.
This work was supported by JSPS KAKENHI Grant Number JP16K12914.

High speed on/off valve (HSV) is an essential digital hydraulic component, and has been widely used for pressure and flow control in hydraulic systems, which require faster and more stable dynamic performance of HSVs to improve control preciseness. However, for some special kinds of HSVs, like ball structure and poppet structure valves which can reset by the hydraulic pressure instead of a traditional reset spring, their dynamic performance is greatly affected by the hydraulic pressure. Aiming at this problem, a self-correcting PWM control algorithm based on current feedback (SPWMCF) is proposed to improve and even maintain the HSVs’ original dynamic performance under changing pressures. Using current feedback analysis based on critical switching currents, the operational state of the HSV is estimated, and adaptive logic switching of different duty ratios of power source is also realized to preserve the dynamic performance of HSV under changing supply pressure to the maximum extent. Finally, a ball structure HSV is used as a research object, through numerical and experimental studies, it is demonstrated that the supply pressure has a great influence on the dynamic characteristics of the HSV, and the proposed control algorithm achieves the expected effect that the dynamic characteristics of the HSV is not only greatly improved but adapted to pressure changes, and the variation range of the dynamic performance can be controlled within 7.4% (0.3ms) under 4-20MPa operating conditions. The presented control algorithm is effective and can be applied in HSV-controlled systems to improve the robustness of the target actuator.

Terahertz (THz) radiations lie in electromagnetic spectrum gap between the infra-red and the microwave frequencies from 0.10 THz to 30 THz. In last few decades, generation and detection of THz radiations has attracted considerable interest not only in technological applications for THz imaging but also as a tool to investigate fundamental properties of materials by using time domain THz spectroscopy. Other applications too include information technology, biomedical sciences, non-destructive evaluation, security, quality control of foods beverage and medicines, environment monitoring and ultrafast computing etc. Much effort has been made to increase the generated terahertz radiation power. Among various methods, generation of THz radiation with the biased photoconductive switch (PCS), play very important role owing to its simple configuration and power controllability by bias and geometrical scaling. The low temperature (LT) grown GaAs PCS is most commonly used due to its sub picosecond lifetime and high mobility. Though, the THz generation efficiency is limited by its low breakdown field of about 5 x 105 V/cm. Thus, wide band gap materials with high breakdown electric fields are attractive for high power THz radiation, e.g., GaN with breakdown voltage 3.3 x 106 V/cm having high saturation velocity 2.5 x 107 V/cm and high thermal conductivity 1.3 W/cm K. Thus we investigate the most straight forward electromagnetic radiation from a GaN based large aperture LA-PCS. A carbon doped epitaxial layer was used for active region to realize high resistivity to stand high bias voltage.
THz pulses of 93.3 pJ/pulse energy was estimated at 500 V bias on excitation with 120 fs laser pulses of 266 nm wavelength with device structure as shown in fig.1. Figure 2 depicts the experimental setup with typical THz pulses and THz spectrum generated by LA GaN-PCS and measured with TDS detection.

The descriptor systems are convenient and natural modeling process for the practical plants. The state space method and the geometric approach are used to study the structure properties and to design the controllers. Comparing these methods, there are not so many literatures using the polynomial matrix approach. In this paper, we will propose an analysis method of the descriptor systems using the regularizing polynomial matrix. The regularizing polynomial matrix compensates the singularity of the descriptor systems, like an interactor matrix for rational function matrices. In fact, the regularizing matrix is almost equivalent to an interactor. Although some derivation methods of the interactor were proposed, almost of all were complex. Mutoh and Ortege proposed the algebraic equation, which the coefficient matrices of the interactor should be satisfied.  However, the solution method was not adequate for computer calculations. The authors proposed a solution of the equation using Moore-Penrose pseudo-inverse. Since a function to calculate the pseudo-inverse is available in some standard software for control engineering, the method is adequate for computer calculations.
We will show that the degree of the regularizing polynomial matrix presents a structural aspect of a given descriptor system. That is, there exists the regularizing matrix of degree one if a given system has no impulsive mode. There exists the regularizing matrix of degree two if a given system has some impulsive modes. We will also a condition for the impulsive controllability of the descriptor systems using the analysis. A method to stabilize the descriptor systems using the polynomial matrix approach will be given.