• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.57-58
• /
• 2012

• Smart Structures and Systems
• /
• v.14 no.5
• /
• pp.765-784
• /
• 2014

In comparison with conventional shape memory actuated structures, antagonistic shape memory alloy (SMA) actuators permits a fully reversible two-way response and higher response frequency. However, excessive internal stress could adversely reduce the stroke of the actuators under repeated use. The two-way shape memory effect might further decrease the range of the recovered strain under actuation of an antagonistic SMA actuator unless additional components (e.g., spring and stopper) are added to regain the overall actuation capability. In this paper, the performance of all four possible types of SMA actuation schemes is investigated in detail with emphasis on five key properties: recovered strain, cyclic degradation, response frequency, self-sensing control accuracy, and controllable maximum output. The testing parameters are chosen based on the maximization of recovered strain. Three types of these actuators are antagonistic SMA actuators, which drive with two active SMA wires in two directions. The antagonistic SMA actuator with an additional pair of springs exhibits wider displacement range, more stable performance under reuse, and faster response, although accurate control cannot be maintained under force interference. With two additional stoppers to prevent the over stretch of the spring, the results showed that the proposed structure could achieve significant improvement on all five properties. It can be concluded that, the last type actuator scheme with additional spring and stopper provide much better applicability than the other three in most conditions. The results of the performance analysis of all four SMA actuators could provide a solid basis for the practical design of SMA actuators.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.2
• /
• pp.215-222
• /
• 2003

In this paper, kinematic analysis and design of constant force mechanisms which employ a linear spring are studied. Firstly, sufficient conditions for the mechanisms to be the constant force mechanisms are derived in terms of displacement variables through the kinematic analysis. Secondly, a few conceptual mechanisms satisfying these constraints are proposed.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.26 no.2
• /
• pp.147-152
• /
• 2016

Shape Memory Alloys (SMAs) undergo changes in shape and hardness when heated or cooled, and do so with great force. Since wire-type SMAs contract in length when heated and pull with a surprisingly large force and move silently, they can be used as actuactors which replace motors. These SMA actuators can be heated directly with electricity and can be used to create a wide range of motions. This paper presents the mechanical design and control for a three fingered, six degree-of-freedom robotic hand actuated by SMA actuators. Each finger has two joints and each joint is actuated with two tendons in the antagonistic manner. In order to create the sufficient force to make the smooth motion, the tendon is composed of two SMA actuators in parallel. For controlling the current to heat the SMA actuators, PWM drivers are used. In experiments, the antagonistic interaction of fingers are evaluated.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.9
• /
• pp.2284-2296
• /
• 1994

Force control of robotic mechanisms continues to be a challenging area. Previous implementation have seldom produced satisfactory results, and researchers in the past have experienced significant instability problems associated with their force controllers. In this study, a new stability factor in force control will be pointed out. When a manipulator is constrained to an environment(force-controlled), geometric instability due to the relationship between the manipulator configuration and the force-controlled direction is shown to be a significant factor in overall system stability. This exploratory study points out a rather intuitive, geometrically based stability factor in terms of an effective system stiffness and analyzes the phenomenon both analytically and graphically. Also, a stiffness control algorithm using the kinematic redundancy of a kinematically redundant manipulator is proposed to improve the overall stability in force control.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.9
• /
• pp.68-79
• /
• 1997

A six DOF fine manipulator based on magnetic levitation is developed. Since most of magnetic levitation system are inherently unstable, a proposed magnetically levitated fine manipulator is implemented by use of an antagonistic structure to increase stability. From mathematical modeling and experiment, the equations of motion are derived. In addition, a six DOF sensing system is implemented by use of three 2-axis PSD sensors. A model reference-$H_{\infty}$ controller is applied to the system for the position control, In application of the fine manipulator, a wafer probing system is proposed to identify nonfunctional circuts. The probing system requires compliance to avoid destruction of DUT(device under test). A feedfor- ward-PD controllers are presented by the terms of the position accuracy, the settling time and the force accuracy.y.

• Journal of Korea Entertainment Industry Association
• /
• v.14 no.7
• /
• pp.309-318
• /
• 2020

This research studies the specific cases of how Hayao Miyazaki re-arranges Hollywood's conservative storytelling model, such as the three-act, eight-sequences structure, and the use of antagonist and antagonistic force, and how he applies them into his fairytale-like narratives to increase the attention of the audience. At the same time, this research also studies the cases of how fairytale-like characters of Miyazaki's storytelling make up for the drawbacks caused by the re-arranged narrative structure and the relationship between the characters, to make the audience keep track to follow the protagonist's journey. This research focuses on the re-arrangement of the three-act structure and the eight-sequences structure. For the details, this research focuses on the alternative use of antagonistic force in My Neighbor Totoro and the cases of antagonists turning to the protagonists' side around the mid-point in Spirited Away and Howl's Moving Castle. Also, the study shows how Miyazaki expands the second act (the third to the sixth sequence) and shortens the third act (the seventh to the eighth sequence) to earn the time for the audience to be in the same position with the protagonist, and how the fairytale-like characters of these films make up for the disadvantages caused by the shortened third act.

• Journal of the Ergonomics Society of Korea
• /
• v.28 no.3
• /
• pp.1-6
• /
• 2009

Recently, importance of the rehabilitation of hand pathologies as well as the development of high-technology hand robot has been increased. The biomechanical model of hand is indispensable due to the difficulty of direct measurement of muscle forces and joint forces in hands. In this study, a three-dimensional biomechanical model of four fingers including three joints and ten muscles in each finger was developed and a mathematical relationship between neural commands and finger forces which represents the enslaving effect and the force deficit effect was proposed. When pressing a plate under the flexed posture, the muscle forces and the joint forces were predicted by the optimization technique. The results showed that the major activated muscles were flexion muscles (flexor digitorum profundus, radial interosseous, and ulnar interosseous). In addition, it was found that the antagonistic muscles were also activated rather than the previous models, which is more realistic phenomenon. The present model has considered the interaction among fingers, thus can be more powerful while developing a robot hand that can totally control the multiple fingers like human.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.4
• /
• pp.1164-1176
• /
• 1996

A magnetically levitated micro-positioner is implemented to avoid mechanical friction and increase precision. Since magnetic levitation system is inherently unstable, most concern is focused on a magnetic circuit design to increase the system dynamic stability. For this, the proposed levitation system is constructed by using an antagonistic structure which permits a simple design and robust stability. From the dynamic equations of motion, it is verified that the proposed magnetically levitated system is decoupled in 6 degree-of-freedom motion. Experimental results are presented in terms of time response and accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.891-894
• /
• 2005

This paper describes a human finger model driven by shape memory alloy(SMA) wires. The finger model has three joints that are similar to human finger. Each joint is actuated with two wires in the antagonistic manner and six wires are used to actuate three finger joint. In order to obtain the desirable finger motion, the diameters of the SMA wires are designed with different diameters by considering the required actuating force and response time. The rotary sensors are used to measure the angle positions of the joints and PWM control using PID algorithm is used to achieve desired angle positions of the finger joints. After estimating the control performance of each finger joint for the desired angle position, the antagonistic motion control of the finger model is experimentally evaluated.