• 한국기계가공학회지
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• 제10권5호
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• pp.51-57
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• 2011

The lightweight and compact actuator with high power is required to perform motion with multiple degrees of freedom. To reduce the size and inertia of a robot manipulator, the mechanical transmission system is used. The shape memory alloy(SMA) is similar to the muscle-tendon-bone network of a human hand. However, there are some drawback and nonlinearity, such as the hysteresis and the stress dependence. In this paper, the design of the underactuated robot hand is studied. The 3-finger dexterous hand is driven by the SMA actuator using segmental mechanism. This digital approach enables to overcome the nonlinearity of SMA wire. The translational displacement of SMA actuator required to bend a phalanx of the underactuated robot hand is estimated and the bending angle of the underactuated robot hand according to input displacement of SMA actuator is predicted by the multi-body dynamic analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 학술대회 논문집 전문대학교육위원
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• pp.103-107
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• 2001

In this paper, we have developed a new Force-Display system using wire-tension method. The proposed system is based on the HIR Lab Haptic Rendering library, which calculates the real position and renders the reflecting force data to device rapidly. The system is composed of device based tendon-driven method, controller and Haptic rendering library. The developed system will be used on constructing the dynamical virtual environment. To show the efficiency of our system, we designed simulation program which can display the moving force (attaching, grabbing, rotating) on two virtual point. As the result of the experiment, our proposed system shows much higher resolution and stability than any others.

• 제어로봇시스템학회논문지
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• 제22권11호
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• pp.960-966
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• 2016

This paper proposes a new concept of a soft and wearable upper-limb exoskeleton. A novel actuation principle, called the twisted string actuation principle, is implemented to make it lightweight, soft, and therefore easily wearable. Its power transmission mechanism and harness are designed to be soft and wearable, yet have enough control accuracy for rehabilitation. In addition to force transmission optimization, a speed enlargement mechanism is newly introduced in order to increase the contraction speed of the twisted string actuation mechanism by sacrificing the unnecessarily large gear reduction ratio of the twisted string mechanism. A prototype has been tested for mirroring therapy, and the feasibility of the proposed mechanism has been shown through a sufficiently accurate tracking performance.

• 한국정밀공학회지
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• 제10권4호
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• pp.200-205
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• 1993

In many applications, the typical parallel-jaw end-effector of a robot arm has been remarkably satisfactory. But, it is not adequate for the applications such as complicated manipulation. In the study, a finger with 4 joints (so, having redundancy) was consturcted to investigate the characteristics of an articulated hand. Each joint was driven by one actuator, and the motor torque was transmited to each joint through a tendon-pulley system. In the context, major considerations for hardware design and the method to solve the inverse kinematics of a redundant manipulator were presented. Finally, the basic capabilities of an articulated hand were presented through experiments.

• 제어로봇시스템학회논문지
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• 제22권10호
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• pp.853-858
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• 2016

Cooperation and collaboration with robots are key functions of robotic utility that are currently developing. Thus, robots should be safe and resemble human beings to cope with these needs. In particular, dual-arm robots that mimic human kinetics are becoming the focus of recent industrial robotics research. Their size is similar to the size of a human adult; however, they lack natural, human-like motion. One of the critical reasons for this is the shoulder complex. Most recent dual-arm robots have only 2 degrees of freedoms (DOFs), which significantly limits the workspace and mobility of the shoulders and arms. Therefore, a redundant shoulder complex could be very important in new developments that enable new capabilities. However, constructing a kinematically redundant shoulder complex is difficult because of spatial constraints. Therefore, we propose a novel, redundant shoulder complex for a human-like robot that is driven by flexible wire tendons. This kinematically redundant shoulder complex allows human-like robots to move more naturally because of redundant DOFs. To control the proposed shoulder complex, a hybrid control scheme is used. The positioning precision has also been considered, and the ability of the shoulder complex to perform several human-like motions has been verified.

• 로봇학회논문지
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• 제12권4호
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• pp.419-424
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• 2017

Twisted string actuators (TSAs) are tendon-driven actuators that provide high transmission ratios. Twisting a string reduces the length of the string and generates a linear motion of the actuators. In particular, TSAs have characteristic properties (compliance) that are advantageous for operations that need to interact with the external environment. This compliance has the advantage of being robust to disturbance in force control, but it is disadvantageous for precise control because the modeling is inaccurate. In fact, many previous studies have covered the TSA model, but the model is still inadequate to be applied to actual robot control. In this paper, we introduce a modified variable radius model of TASs and experimentally demonstrate that the modified variable radius model is correct compared to the conventional variable radius string model. In addition, the elastic characteristics of the TSAs are discussed along with the experimental results.

• 제어로봇시스템학회논문지
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• 제19권12호
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• pp.1160-1166
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• 2013

This paper presents feedforward controllers to improve the control performance of the motion and grasping force of a surgical instrument used in an MIS (Minimally Invasive Surgery) robot. The surgical instrument has a long distance between the drive motors and its active joints. Therefore, the gripper on the instrument is controlled by a cable drive mechanism, which generates a coupled motion between the wrist joint and the grip direction. In order to solve the problem, this paper analyzes the pulley composition of the surgical instrument and proposes feedforward controllers to eliminate the coupled motion. Furthermore, feedforward controllers to regulate the grasping force are proposed to deal with another coupling problem between the grasping force of the instrument and the motion of the instrument joints. The experimental results demonstrate the improved control performance of the motion and grasping force of the instrument.

• 로봇학회논문지
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• 제12권1호
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• pp.26-32
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• 2017

Previous shape sensors including bend sensors and optic fiber based sensors are widely used in various applications including goniometer and surgical robots. But theses sensors have large nonlinearity, limited in the range of sensing curvature, and sometimes are expensive. This study suggests a new concept of bend sensor using cable-conduit which consists of the outer sheath and the inner wire. The outer sheath is made of helical coil whose length of the central line changes as the sheath bends. This length change of the central line can be measured with the length change of the inner cable. The modeling and the experimental results show that the output signal of the proposed sensor is linearly related with the bend angle of the sheath with root mean square error of 5.3% of $450^{\circ}$ sensing range. Also the polynomial calibration of the sensor can decrease the root mean square error to 2.1% of the full sensing range.

• 로봇학회논문지
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• 제17권3호
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• pp.322-333
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• 2022

The Avatar robot, which is one of the teleoperation robots, aims to enable users to feel the robot as a part of the body to intuitively and naturally perform various tasks. Considering the purpose of the avatar robot, an end-effector identical to a human hand is advantageous, but a robotic hand with human hand level performance has not yet been developed. In this paper we propose a new 3-finger robotic hand with human-avatar hand posture mapping algorithm which were integrated with TOCABI-AVATAR, one of the teleoperation system. Due to the flexible rolling contact joints and tendon driven mechanism applied to the finger, the finger could implement adaptive grasping and absorb the impact force caused by unexpected contacts. In addition, human-avatar hand mapping algorithm using five calibration hand postures propose to compensate physical differences between operators. Using the TOCABI-AVATAR system with the robotic hands and mapping algorithm, the operator can perform 13 out of 16 hand postures of grasping taxonomy and 4 gestures. In addition, using the system, we participated in the ANA AVATAR XPRIZE Semi-final and successfully performed three scenarios which including various social interactions as well as object manipulation.