Deokwon Yun

A material rigidity effect of a bimorph piezoelectric actuator

This paper presents the numerical modeling of a piezoelectric actuator used to avoid the limitation of the lock-in region in a ring resonator. Ring resonators have proved suitable for use as inertial sensors for navigation, guidance and attitude controls. However, their accuracy has been limited by the lock-in region due to frequency coupling between two counter-propagating waves at low rotation rates. This coupling introduces no phase difference, and no angular increment is detected. The problem can be overcome by mechanically dithering the ring resonator. Mechanically, the vibro-elastic bimorph piezoelectric actuator has been used as a control but is influenced by piezoelectric rigidity effects. To more accurately predict the dithering frequency of a mechanical dither, numerical modeling of a piezoelectric actuator includes the piezoelectric rigidity effect of the actuator, which occurs in both the static and dynamic behaviors of composite plates having piezoelectric layers symmetrically bonded to the top and bottom surfaces. Corrections were made to figures 1 and 2 on 13 June 2007. The corrected electronic version is identical to the print version

Adaptive impedance control for upper limb assist exoskeleton

Need to develop human bodys posture supervised robots, gave the push to researchers to think over dexterous design of exoskeleton robots. It requires to develop quantitative techniques to assess motor function and generate the command for the robots to act accordingly with complex human structure. In this paper, we present a new technique for the upper limb power exoskeleton robot in which load is gripped by the human subject and not by the robot while the robot assists. Main challenge is to find non-biological signal based human desired motion intention to assist as needed. For this purpose, we used newly developed Muscle Circumference Sensor (MCS) instead of electromyogram (EMG) sensors. MCS together with the force sensors is used to estimate the human interactive force from which desired human motion is extracted using adaptive Radial Basis Function Neural Network (RBFNN). Developed Upper limb power exoskeleton has seven degrees of freedom (DOF) in which five DOF are passive while two are active. Active joints include shoulder and elbow in Sagittal plane while abduction and adduction motion in shoulder joint is provided by the passive joints. To ensure high quality performance model reference based adaptive impedance controller is employed. Exoskeleton performance is evaluated experimentally by a neurologically intact subject which validates the effectiveness.

Study on Efficacy of Gait Training for Hemiplegia Patients Using Lower-Limb Wearable Robot

1 한양대학교 메카트로닉스공학과 (Department of Mechatronics Engineering, Hanyang University) 2 한양대학교 기계공학과 (Department of Mechanical Engineering, Hanyang University) 3 한양대학교 기계설계공학과 (Department of Mechanical Design Engineering, Hanyang University) 4 고영테크놀러지 제어기술부 (Control Technology Department, Koh Young Technology) 5 한양대학교 의학과 (Department of Medicine, Hanyang University) 6 한성대학교 기계시스템공학과 (Department of Mechanical System Engineering, Hansung University) 7 한양대학교 로봇공학과 (Department of Robot Engineering, Hanyang University) Corresponding author: cshan@hanyang.ac.kr, Tel: +82-31-400-5247

Upper extremity assist exoskeleton robot

Need to develop human bodys posture supervised robots, gave the push to researchers to think over dexterous design of exoskeleton robots. It requires to develop quantitative techniques to assess motor function and generate the command for the robots to act accordingly with complex human structure. In this paper, we focus on developing new technique for the upper limb power exoskeleton in which load is handled by the human subject and not by the robot. Main challenge along with the design complexity is to find the desired human motion intention and to develop an algorithm to assist as needed accordingly. For this purpose, we used newly developed Muscle Circumference Sensor (MCS) instead of electromyogram (EMG) sensors. MCS together with the load cells is used to estimate the desired human intention by which desired trajectory is generated. The desired trajectory is then tracked by passivity based adaptive control technique. Developed Upper limb power exoskeleton has seven degrees of freedom (DOF) in which five are passive and two are active. Active joints include shoulder and elbow, powered by electric motors and move in Sagittal plane while abduction and adduction motion in shoulder joint is provided by the passive joint. Performance of the exoskeleton is evaluated experimentally by a neurologically intact subject. The results show that after adjusting the motion intention recognition algorithm for the subject, the robot assisted effectively and the subject only felt nominal load regardless of the weight in hand.

Techniques for measuring error motions of a precise rotational stage

Rotating stages in semiconductor industry, biotechnology and many other fields require challenging accuracy to perform their functions properly. To evaluate and improve the performance of such precision machinery, it is inevitable to consider the error motion on which knowledge can be used for error compensation, error-reducing design, and other improvement activity. In this study we have measured the 5 DOF error motions of a rotating stage with capacitive sensors. To achieve the measurement accuracy, we have used Donaldsons reversal, Estlers reversal, and other techniques. We have designed a sensor jig to achieve measurement including reversals effectively.

Neurorehabilitation robot system for neurological patients using H-infinity impedance controller

Patients with paralyzed upper extremities due to central nervous system lesion after stroke, traumatic brain injury and spinal cord injury receive rehabilitation therapy. The rehabilitation robot is studied for the effective therapy. To train the patients more effectively, it is necessary to study not only mechanisms of robots but also control strategy for rehabilitation. The purpose of various control algorithms for therapy is to implement various training repetitively and intensively. Then, these control strategies can induce the plasticity of motors and brain and improve patients motor recovery. In this paper, we propose the upper limb robot system for neurorehabilitation. This robot is combined with the path control algorithm applying H-infinity optimization to impedance control for virtual tunnel. We present the entire robot system, robots mechanism and procedure of optimizing the path controller for robustness. Also, the robot system is verified by test with a healthy person before it applies to the paralyzed patients.

Chattering Free Sliding Mode Control of Upper-limb Rehabilitation Robot with Handling Subject and Model Uncertainties

Need to develop human body`s posture supervised robots, gave the push to researchers to think over dexterous design of exoskeleton robots. It requires to develop quantitative techniques to assess human motor function and generate the command to assist in compliance with complex human motion. Upper limb rehabilitation robots, are one of those robots. These robots are used for the rehabilitation of patients having movement disorder due to spinal or brain injuries. One aspect that must be fulfilled by these robots, is to cope with uncertainties due to different patients, without significantly degrading the performance. In this paper, we propose chattering free sliding mode control technique for this purpose. This control technique is not only able to handle matched uncertainties due to different patients but also for unmatched as well. Using this technique, patients feel active assistance as they deviate from the desired trajectory. Proposed methodology is implemented on seven degrees of freedom (DOF) upper limb rehabilitation robot. In this robot, shoulder and elbow joints are powered by electric motors while rest of the joints are kept passive. Due to these active joints, robot is able to move in sagittal plane only while abduction and adduction motion in shoulder joint is kept passive. Exoskeleton performance is evaluated experimentally by a neurologically intact subjects while varying the mass properties. Results show effectiveness of proposed control methodology for the given scenario even having 20 % uncertain parameters in system modeling.

Development of micro fluidic device for a cell-counter using electrical-impedance method

Many previous researches related with the cell-counter have measured transit of cells by the electrical-impedance method. Most of devices using electrical-impedance method have electrodes which are made by metal deposition process. In this study, the micro channel takes the place of metallic electrodes. The electric current is passed through the micro channel which is filled with PBS solution. The proposed device helps to save the time of fabrications of micro fluidic device. The process for metal deposition and fine alignment process between micro fluidic channel and base of electrodes can be canceled in proposed device. The signal for counting of a red blood cell of human and polymer microspheres were successfully measured.