Tadahiro Hasegawa

Modeling of shape memory alloy actuator and tracking control system with the model

There has been great demand for shape memory alloy (SMA) actuators within the field of micro-machines. However, the thermomechanical behavior of SMA actuators is too complicated to accurately predict their response. Moreover the tracking control accuracy of SMA actuators is limited due to the inherent hysteresis nonlinearity. The paper presents a model of an SMA actuator for use in mechanical design and a control system for compensating the hysteresis. First, the model based on constitutive laws developed by Brinson et al. (1996) and our proposed hysteresis model is demonstrated. Next, we propose a control system composed of a proportional integral derivative (PID) feedback loop and a feedforward loop. In the feedforward loop, the desired control input corresponding to the desired displacement is obtained from a static SMA model derived by modifying the classic Preisach hysteresis model. We also propose a method for identifying parameters of the hysteresis model. This methods demands only measurement of the major loop. Application of the control system to our developed SMA actuator shows that the tracking control performance is improved.

A control system to compensate the hysteresis by Preisach model on SMA actuator

Hysteresis phenomena often degrade system performance such as giving rise to undesirable inaccuracy. Shape Memory Alloy (SMA) actuators are chosen as an example of a plant with hysteresis and a control system to compensate the hysteresis is proposed in this paper. Firstly, a model which represents the temperature hysteretic property of SMA and its inverse model are designed. Secondly, a controller is proposed to compensate the hysteretic property by using the inverse model. Lastly, this method is applied to control the electrical resistance of SMA, which reflects its state, and the usefulness of the controller is confirmed experimentally.

MICRO ULTRASONIC HOMOGENIZER CHIP MADE BY HYBRID MICROSTEREOLITHOGRAPHY

The world’s first micro-ultrasonic homogenizer chip, a new type of biochemical IC chip [1], is proposed and developed successfully. The homogenizer chip utilizes ultrasonic cavitation to disrupt cells. Both a piezoelectric element and an exponential horn to generate ultrasonic cavitation are hybridized in the chip by using our original microstereolithography technique, the “hybrid-IH process [2]”. We succeeded to disrupt cells (PC 12) within only 3 seconds by using this chip. The efficiency of cell homogenization was almost 100%. The proteins extracted from PC 12 cells were separated and detected by using SDS gel-electrophoresis and silver staining. The micro homogenizer chip is useful for pretreatment of various biochemical and biological analyses in microscale.

Simple and Effective Method for Hold and Connet of Chemical IC Chip-Set

We developed a simple and effective coupling method for interconnecting modular micro fluidic devices such as “Biochemical IC Family” proposed by Ikuta [1]. Thin silicone rubber films formed from a polymer mold are utilized as reusable couplers. This simple coupler provides a good seal under high pressure (>400 kPa). Moreover, this connection can minimize a dead volume between the biochemical IC chips containing multiple micro fluidic devices. This coupling method is useful not only for the biochemical IC chips but also other micro fluidic devices.

The optimized SMA micro pump chip applicable to liquids and gases

We fabricated a high performance micro pump chip with optimized design. This chip can flow not only liquids but also gases (12 µ/min., 25 kPa for water. 11 µ/min., 5 kPa for air). Moreover, the micro pump is tolerant of gas bubbles in the liquid chamber and it is possible to prime itself. To achieve this performance, the micro pump improved three elements. The first one is eliminating pressure loss of the check valves. The second one is optimizing flow pattern inside the deformable chamber. And the third one is increasing compression ratio of the deformable chamber. Our original 3D micro fabrication process named “Hybrid IH process (micro stereo lithography)” to hybridize various micro parts (silicone rubbers, SMA actuators etc.) with UV-polymer structure was utilized for chip fabrication. Therefore, their packaging without leakage was made successfully.

Silicone Rubber Coupling for Micro Fluidic Devices - Theoretical Analysis of Sealing Properties for Interconnection -

We have developed the simple and effective method “Silicone Rubber Coupling” for holding and connecting of the modular micro fluidic device “Biochemical IC” proposed by Ikuta [1][2]. The experimental data of this method showed very unique characteristics. The maximum leakage pressure increases while the coupling part gets thin, differing from general sealing technology “O-ring”. Thin coupling part is effective in practical use. Additionally, it is of importance in academic. Therefore, the sealing properties of the silicone rubber coupling method was analyzed theoretically, whose results proved the validity of the experiments. This method is low-cost and useful not only for the biochemical IC chips but also the micro fluidic devices in general

Microstereolithography and its application to biochemical IC chip

The worlds first micro stereo lithography, named IH process, was proposed and developed by the speaker in 1992. By now, several types of micro stereo lithography systems have been developed. Three-dimensional resolution of solidification has reached to 0.2 micron at present. These 3D micro fabrication processes using UV curable polymer gave a big impact on not only MEMS but also optics. The latest version of IH process enables us to make a movable micro mechanism without assemble process or sacrificial layer technique often used in silicon process. It is well known that the IH process is the mother of two-photon micro stereo lithography and its applications. Recently new micro chemical device named Biochemical IC Chip was proposed and developed by the speaker. This chip is based on the module IC chip-set like todays TTL family. IH process enable to make the biochemical IC including real three-dimensional micro fluid channels. Various kinds of Biochemical IC chips such as micro pump, switching valve, reactor, concentrator and detector have already been fabricated successfully. Basic performance of micro chemical devices constructed by the biochemical IC chips were demonstrated. The biochemical IC chips will open new bioscience and medicine based on innovative technology.

Development of constant altitude flight system using two dimensional laser range finder with mirrors

This paper proposes a constant altitude flight system using two dimensional laser range finder with mirrors. Recently, unmanned aerial vehicles (UAVs) are expected to perform in the inspection of deteriorated infrastructures such as bridges and tunnels. In the most of such operations, UAVs should be navigated and controlled in GPS-denied environment. In this paper, we apply two dimensional laser range finder with mirrors that can scan over horizontal direction and can measure vertical direction by using the change of the laser direction with mirrors. Consequently, the sensor makes it possible to achieve three dimensional environmental recognition. This paper proposes altitude estimation method from the point data obtained by the sensor and demonstrates constant altitude flight experiment using that two dimensional laser range finder with mirrors. The flight experiment verified the validity of the developed system.

Improvement of Flexible Electrostatic Adhesive Device and its Performance Evaluations

A flexible electrostatic adhesive device was modified successfully to improve an aging characteristics. The experimental results using a previous electrostatic adhesive device has shown that, in concrete wall, the maximum adhesive force was 1kgf or more during applied voltage 10kV. However, problems that the adhesive force decreases depending on aging arose. To solve the problem, the design of the electrostatic device was modified. Thereby, the electrostatic adhesive device succeeded that an adhesive force was generated 1kgf or more during a month or more. The flexible electrostatic adhesive device is useful for a practical use to stick to an inspection apparatus on a concrete wall of a bridge or a tunnel.

Fall detection using smart phone and ubiquitous pulse wave sensor

We have proposed the fall detection method using acceleration and angular velocity sensor in android device as well as pulse wave sensor in other device. Acceleration and angular velocity are measured by smartphones sensors while pulse wave is measured by an external sensor. The application software for detecting the start to fall using smartphone, and the ubiquitous pulse wave sensor that can measure a human pulse even during fall motion was developed successfully.