Honggul Jun

Walking and sit-to-stand support system for elderly and disabled

Walking and sit-to-stand support system, the smart mobile walker, is being developed to help elderly and disabled to live an independent daily life. It comprises almost omnidirectional driving mechanism, sit-to-stand support mechanism, and motion compliance module to control the system. The development and evaluation of basic motion compliance algorithm shows that the algorithm for extraction of user intention from the interaction of the operator and the system determines performance of the system. The required parameters and performance index for improving sit-to-stand function are evaluated by the analysis of force reflection between the operator and the system. Finally, future research topics to improve the performance are addressed

Posture balancing control of smart mobile walker for uneven terrain

This paper introduces a posture control of smart mobile walker, where the controller adjusts four linear actuators based on the measurement of orientation and ground forces to balance manipulator and to keep wheel contact with ground. It is an important feature for this walker to adapt its pose to uneven terrains such as ramp or slope since it aims to assist elderly and disabled safely. Control scheme is based on PID impedance control where sensor noise and wind-up due to low actuator performance are considered. Hardware implementation and its experimental result are presented.

Disturbance Analysis in an Optical Disk Drive Using Model Based Disturbance Observer and Waterfall Technique

A novel disturbance measurement method, model based disturbance observer (MBDO) for optical disk drives (ODDs), is proposed and the disturbance analysis using the proposed method is performed under various conditions. In ODDs, the quantitative and qualitative analysis for the generated disturbance during normal operation is very important to successful servo loop design. However, the disturbance measurement is difficult, and high precision measurement is necessary. Furthermore, the conventional disturbance measurement method using a LDV (laser Doppler vibrometer) has many difficulties in eccentricity direction due to the vertical movement of an optical disk. To solve this problem, the MBDO is proposed. First, the relationship between the servo loop for ODDs and the generated disturbance are briefly reviewed. Second, the principle of the MBDO is introduced, and the disturbance measurement results, which are measured by the MBDO and a LDV, are compared. In these experiments, test DVD-ROM disks are used to generate quantitative/qualitative disturbance. Then, the disturbance analysis under various conditions is performed using waterfall technique. This technique clearly shows the disturbance trend from the inner part of an optical disk to the outer part of it. Finally, the various disturbances measurement results are summarized and some remarks for it are commented.