Yoshihiro Hasegawa

Fabrication of a wearable fabric tactile sensor produced by artificial hollow fiber

An artificial-hollow-fiber structure as a new material for MEMS was developed and applied to a novel type of fabric tactile sensor. The artificial hollow fiber was fabricated by uniformly deposited metal and insulation layers on the surface of an elastic tube. A special rotating mechanism for uniformly depositing a metal layer on the tube surface during sputtering was developed. A rectangular-shaped fabric tactile sensor was produced by combining artificial hollow fibers and typical cotton yarns, like a cloth. The sensor can detect a contact force by measuring changes in capacitance at all intersection points of the artificial hollow fibers. Two different types of wearable-tactile-sensor glove, a patched type and a direct knit type, were also fabricated, and it was confirmed that both types can detect a normal load by measuring the capacitance change.

An active tactile sensor for detecting mechanical characteristics of contacted objects

We propose an active tactile sensor actuated by magnetic force. The tactile sensor has the advantage of being able to detect mechanical characteristics related to a tactile impression of contacted objects using a single sensor structure, much as human skin functions. It consists of a displacement-sensing element of piezoresistors formed on a silicon diaphragm, and a magnetic actuating element (a permanent magnet and a flat coil). The sensor has two modes of operation, quasi-static and vibration, and it can detect contact force, elasticity and damping of contacted objects by choosing between operation modes. We fabricated the piezoresistor sensing and magnetic actuating elements by applying the microelectromechanical systems technologies, and assembled them in a hybrid manner. The size of the sensor was 6.0 mm × 6.0 mm × 10 µm. As contact samples we used three different rubber materials with hardness values ranging from A20 to A60 in Shore A. We experimentally confirmed that both the resonance frequency and the Q-factor of the sensing element in the vibration mode changed with different samples. We were able to calculate the elastic and damping coefficients of the contacted rubber objects by analyzing the vibrational response of the diaphragm. From the results, we concluded that the active sensor can detect mechanical characteristics of contacted objects using a single sensor structure.

Novel type of fabric tactile sensor made from artificial hollow fiber

We proposed an artificial hollow fiber structure as a new material for MEMS, and applied it for realizing a novel type of fabric tactile sensor. The hollow fiber structure is fabricated from commercially available silicone rubber tube by laminating a metal and an insulation layers on the surface. The fabricated hollow fiber is 250 mum in external diameter and 40 mum in thickness. The fabric tactile sensor is produced by weaving the hollow fibers like a cloth. Contact force on the sensor is detected by measuring the capacitance change at the intersection of two intersected fibers. The sensor detects the 2D contact-force distribution by sequentially scanning the capacitances at all fiber intersection points. The advantage of this novel fabric tactile sensor is that it can realize a genuine wearable sensor by directly weaving artificial fibers. In the present study, we fabricated artificial hollow fibers by thin-film deposition, and created a fabric tactile sensor by weaving the hollow fibers by hand. We confirmed the developed fabric tactile sensor can detect the contact force by measuring the capacitance change between the intersecting hollow fibers.

Multifunctional active tactile sensor using magnetic micro actuator

This paper proposes a multifunctional tactile sensor device driven by magnetic force. The device has the advantage that it can detect multiple physical values, such as contact-force and the elastic and damping coefficients of a contacted object. We previously used an external pneumatic system for actuating the device, and confirmed it can measure the elastic-coefficient of an object. This time, we realized hybrid active tactile sensor system by assembling a magnetic driving mechanism for detecting multiple physical values. We also developed a theoretical model of the detection, and experimentally confirmed both elastic and damping coefficient detection by using different types of silicone rubbers as samples.

Magnetic actuation of a micro-diaphragm structure for an active tactile sensor

We previously proposed an active tactile sensor that detects both the contact force and hardness of objects such as fingertips. We validated the device principle by using a pneumatic actuation system [1-2]. As a new method for driving the sensor element, we proposed the idea of using a magnetic force working between a permanent magnet on the sensor element and a microfabricated flat coil. We developed the flat coil by using thick photoresist as a mold and electroplated copper as a conductor. We assembled the sensor element and the flat coil, and constructed a hybrid active tactile sensor system. When we dynamically drove the sensor with the magnetic actuator, we could drive the sensor element around its mechanical resonance frequency. We expect that this active tactile sensor can detect a variety of information about an object, such as its hardness and damping factor.

Hardness detection using a micromachined active tactile sensor

We developed a new type of micromachined tactile sensor that detects both the contact force and hardness of an object. It consists of a diaphragm with a mesa structure, a piezo-resistive strain sensor on the diaphragm, and a chamber for pneumatic actuation. We theoretically designed the device specifications to detect humanfinger touch. We developed the fabrication process of the device using micromachining technology. The sensor element measures 6.0 mm /spl times/ 6.0 mm /spl times/ 0.4 mm. We experimentally evaluated the device characteristics by using silicone rubbers with different hardnesses as the model materials, and we verified the hardness detection performance. The fabricated tactile sensor detected differences in hardness in the range of 10/sup 3/ to 10/sup 5/ N/m.

Impact Resilience Measurement of Elastic Materials by using Active Tactile Sensor

This paper proposes an active tactile sensor driven by using piezo-electrical actuator. It consists of a silicon diaphragm having piezoresistive strain sensors for measuring displacement of the diaphragm, and a piezoelectric actuator for driving the sensing element. The proposed active tactile sensor has an advantage in that it can detect the multiple physical values, elasticity and impact resilience of a contact object, by analyzing the obtained step-response waveform. We fabricated the sensor element by using micro-electro-mechanical-systems (MEMS) technologies, and assembled it with a commercially available piezoelectric actuator in hybrid manners to produce the active tactile sensor. The sensor was 15 mm times 15 mm times 20 mm. Six different rubbers of different hardness ranging from A30 to A70 in Shore A, was used to evaluate the elasticity detection function of the sensor, and we confirmed that the output increased linearly with the increase in the rubber hardness (elasticity). We also evaluated two different rubber materials, urethane and damping rubbers, which had different values of impact resilience, and found that step responses of the sensor output were quite different between two (the damping rubber showed overshooting phenomena at the rise). We therefore concluded that the proposed sensor is capable of detecting two values, elasticity and impact resilience, of a contact object