Jeong-Hoi Koo

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To cool down image sensors in observation satellites, a miniature linear cryogenic cooler is used. The cooler operates at a constant frequency and it creates the main vibration disturbance that is transmitted to the image sensors, causing poor image quality. A semi-active vibration system using a tuned vibration absorber (TVA) has shown to be effective for(More)
Miniature cryogenic coolers are widely used to cool down sensitive image sensors in observation and surveillance satellites. The linear actuator in the cooler compressor operates at a relatively constant rate and this is the main source of vibration disturbance transmitted to the imaging sensor. Passive vibration isolation with and without an absorber, and(More)
This paper presents a new miniature haptic button based on MR fluids which conveys realistic and exiting haptic button profiles in small handheld devices. A novel mechanism is presented to maximize the resistive force and create various kinesthetic sensations even in the small size. After construction of a prototype, the performance of the proposed haptic(More)
Haptic display units have been widely used for conveying button sensations to users, primarily employing vibrotactile actuators. However, the human feeling for pressing buttons mainly relies on kinaesthetic sensations (rather than vibrotactile sensations), and little studies exist on small-scale kinaesthetic haptic units. Thus, the primary goals of this(More)
An adaptive tunable vibration absober based on magnetorheological elastomer (MRE) is designed as an intelligent device for auto-tuning itself to the time-varying harmonic disturbance force to reduce the unwanted vibration of the primary system in the steady state. The objectives of this note are to develop and implement a continuous control method for a MRE(More)
This paper presents a novel Magneto-rheological (MR) brake system that can self-regulate the output braking torques. The proposed MR brake can generate a braking torque at a critical rotation speed without an external power source, sensors, or controllers, making it a simple and cost-effective device. The brake system consists of a rotary disk, permanent(More)
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