• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.883-888
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• 2011

Laparoscopic surgery is being used in various surgical fields because it minimizes scarring. Laparoscopic operations require practical hand skills, so surgeons train on animals and via surgery training tool sets. However, these tool sets do not give the surgeon the sensation of touching real organs. A recently developed laparoscope simulator has a high friction force along the translational axis and a high gravity force along the pitch axis, and therefore it does not permit the operator to control his or her hands delecately. In the paper, the friction force along the axes is auumed to depend on the veolcity, and the gravity force on the angle and distance. We develop a compensation model that combines the gravity and friction force models.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.15-16
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.393-397
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• 1996

A stewart platform-based force/torque sensor with 6 elastic legs was designed and manufactured Kinematic design parameters were determined so that the force/torque sensor might have the isotropic force/torque properities. In a force/torque analysis, it was used the solution of forward kinematics by linearization of the solution of the inverse kinematics. The performance of te force/torque sensor was investigated by measurement experiments. The gravity compensation was conducted to reduce the force and torque effects by the weights of the upper plate, joints and other sensor parts.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.1
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• pp.78-83
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• 1997

The paper presents the experimental analysis of a Stewart platform-based force-torque senor. The closed-form solution of forward kinematics of the Stewart platform is derived approximately by way of a linearization technique, and the solution is used in the force analysis of the force-torque sensor. An exper- mental studies show that the proposed method including gravity compensation algorithm is valid for Stew- art platform-based force-torque sensors. The performance of the developed force-torque sensor is evaluated in view of accuracy and linearity in measurements.

• The Journal of Korean Physical Therapy
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• v.11 no.1
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• pp.63-70
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• 1999

This study was for mathematical method of calculating the joint reaction force during on single - leg stance on a normal and hemiplegic patients. It is important to compare the distance of the line of gravity from the hip joint on hemiplegic patients with this on normal in this study. In earlier studies, there is no include the concept about biomechanical analysis on the shin of line of gravity of hemiplegic patients. Though this concept, we found the compensation make the line of gravity closer to the supporting hip joint and the trunk was toward the side of paralysis. The result of the Joint reaction force on hemiplegic patients is found to be approximately $31.33\%$ in the unaffected side by biomechanical analysis.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.275-282
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• 2013

Applications such as vibration isolation, gravity compensation, pick-and-place machines, etc., would benefit from (long-stroke) cylindrical/tubular permanent magnet (PM) actuators with integrated passive gravity compensation to minimize the power consumption. As an example, in component placing (pick-and-place) machines on printed circuit boards, passive devices allow the powerless counteraction of translator including nozzles or tooling bits. In these applications, an increasing demand is arising for high-speed actuation with high precision and bandwidth capability mainly due to the placement head being at the foundation of the motion chain, hence, a large mass of this device will result in high force/power requirements for the driving mechanism (i.e. an H-bridge with three linear permanent magnet motors placed in an H-configuration). This paper investigates a tubular actuator topology combined with passive gravity compensation. These two functionalities are separately introduced, where the combination is verified using comprehensive three dimensional (3D) finite element analyses.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.136-142
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• 2015

In the paper, a design method of knee and pelvis joint in the biped robot is proposed for shock absorption and gravity compensation. Similarly to the human's body, the knee joints of the biped robot support most body weight and get a shock from the landing motion of the foot on the floor. The torque of joint motor is also increased sharply to keep the balance of the robot. Knee and pelvis joints with the spring are designed to compensate the gravity force and reduce the contact shock of the robot. To verify the efficiency of the proposed design method, we develope a biped robot with the joint mechanism using springs. At first, we experiment with the developed robot on the static motions such as the bent-knee posture both without load and with load on the flat ground, and the balance posture on the incline plane. The current of knee joint is measured to analyze the impact force and energy consumption of the joint motors. Also, we observe the motor current of knee and pelvis joints for the walking motion of the biped robot. The current responses of joint motors show that the proposed method has an effect on shock reduction and gravity compensation, and improve the energy efficiency of walking motions for the biped robot.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.524-527
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• 1988

Basic types of bilateral servo systems were described and practical consideration in the bilateral servo controller design was introduced. Power assistance to the operator is essential for high efficiency and accurate force reflection is necessary for dexterous manipulation. This paper shows a controller structure under development at KIMM which employs nonlinear friction compensation and memory based gravity compensation technique for efficiency and dexterity.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.5
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• pp.257-263
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• 2000

One of the basic assumptions in the static gait design for a walking robot is that the weight of leg should be negligible compared to that of body, so that the total gravity center is not affected by swing of a leg. Based on the ideal assumption of zero leg-weight, conventional static gait has been simply designed for the gravity center of body to be inside the support polygon, consisting of each support leg's tip position. In case that the weight of leg is relatively heavy, however, while the gravity center of body is kept inside the support polygon, the total gravity center of walking robot can be out of the polygon due to weight of a swinging leg, which causes instability in walking. Thus, it is necessary in the static gait design of a real robot a compensation scheme for the fluctuation in the gravity center. In this paper, a body impedance control is proposed to obtain the total gravity center based on foot forces measured from load cells of a real walking robot and to adjust its position to track the pre-designed trajectory of the corresponding ideal robot's body center. Therefore, the walking stability is secured even in case that the weight of leg has serious influence on the total gravity center of robot.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.2
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• pp.160-167
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• 2001

This paper presents control and evaluation of a new haptic device with a 6-DOF parallel mechanism for interfacing with virtual reality. This haptic device has low inertial, high bandwidth compactness, and high output force capability mainly due to of base-fixed motors. It has also wider orientation workspace mainly due to a RRR type spherical joint. A control method is presented with gravity compensation and with force feedback by an F/T sensor to compensate for the effects of unmodeled dynamics such as friction and inertia. Also, dynamic performance has been evaluated by experiments. for force characteristics such as maximum applicable force, static-friction force, minimum controllable force, and force bandwidth Virtual wall simulation with the developed haptic device has been demonstrated.