• Journal of the Korean Society of Industry Convergence
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• v.22 no.2
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• pp.87-93
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• 2019

This research deals with posture optimization for humanoid robot against external forces using genetic algorithm and neural network. When the robot takes a motion to push an object, the torque of each joint is generated by reaction force at the palm. This study aims to optimize the posture of the humanoid robot that will change this torque. This study finds an optimized posture using a genetic algorithm such that torques are evenly distributed over the all joints. Then, a number of different optimized postures are generated from various the reaction forces at the palm. The data is to be used as training data of MLP(Multi-Layer Perceptron) neural network with BP(Back Propagation) learning algorithm. Humanoid robot can find the optimal posture at different reaction forces in real time using the trained neural network include non-training data.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.37-43
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• 2005

A haptic steering system which reflects steering reaction torque has been developed for a fixed base vehicle simulator. The haptic steering system consists of a steering effort sensor, MR-clutch, AC servo motor and controller. In order to generate realistic steering torque feel to driver and at the same time to meet real-time simulation requirement, 3D torque map is constructed by experimental data and torque generation algorithm using the torque map has been also developed. 3D torque map is constructed using curve fitting and interpolation of the measured values of the steering angle, velocity and steering torque from actual slalom test on the proving ground. In order to carry out performance test of the developed haptic steering system, a fixed based vehicle simulator is constructed by integrating real time vehicle dynamics module, VR-video/audio module, and the haptic steering system. Steering torque and steering angle curves have been obtained from virtual testing in the vehicle simulator and performance of the haptic steering system has been evaluated.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.18-28
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• 2014

We assume that two control moment gyros are installed for space qualification in a satellite with four reaction wheels, and study the high agile maneuver method. Using high torque control moment gyros, we reduce the satellite's attitude error. After that, we activate reaction wheels to control remaining attitude error. This proposed method can avoid singularity problem of control moment gyros, and do not require gimbals' angle to calculate torque command. Through numerical simulations, we show that our method's agile performance is similar to previous method and reduce the reaction wheels' required momentum.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.4
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• pp.295-302
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• 2008

This paper examines the design and the performance of a PMA-RSM(permanent-magnet assisted reluctance synchronous motor) for washing machine. A FEM(finite element method) is used to analyze performance and maximum torque characteristic of the proposed PMA-RSM. The designed motor is a combination of salient poles, which is making reluctance torque, and permanent magnet which are located on the air-gap of rotor to get a enough torque during low speed resign. Typical flux barrier type reluctance synchronous motor and the effects of adding magnet into the flux barrier of the rotor of a PMA-RSM are compared and examined. Also the maximum torque point of the reluctance torque by reluctance and reaction torque by magnetic alignment torque, which is in barrier, of the proposed PMS-RSM are derived through simulation. Using this results, the characteristics analysis of a performance, an average torque and a torque ripple of flux barrier RSM and the proposed PMA-RSM are performed through FEM under the saturation effect respectively.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.257-264
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• 2016

Objective: The purpose of this study was to determine the periodicity of shank-foot segment coupling and free torque before and after fatigue induced by prolonged running. Method: Fifteen young healthy male participants with a rear-foot strike ran on instrumented dual-belt treadmills at 70% of their maximum oxygen uptake for 65 min. Kinematic and ground reaction force data were collected for 20 continuous strides at 5 and 65 min (considered the fatigued condition). The approximate entropy tool was applied to assess the periodicity of the shank internal-external rotation, foot inversion-eversion, shank-foot segment coupling, and free torque for the two running conditions. Results: The periodicity of all studied parameters, except foot inversion-eversion, decreased after 65 min of running (fatigued condition) for 80% of the participants in this study. Furthermore, 60% of the participants showed similarities in the change of periodicity pattern in shank internal-external rotation, coupling, and free torque. Conclusion: The findings indicated that the foot inversion-eversion motion may pose a higher risk of injury than the shank internal-external rotation, coupling, and free torque in the fatigued condition during prolonged running.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.651-657
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• 2008

A new approach for maximizing torque capability of low efficient reaction wheel assembly is addressed in this paper. At first, to find out a solution in constrainted field, weighted pseudo-inverse and momentum minimized allocation are suggested instead of a general control allocation called pseudo-inverse. The second method is a structural manner to enlarge torque capability of specific axis by changing installed skew angle of wheels. Two proposed methods are applied to large angle maneuvers of satellite. Improvement of control performance and feasibility for applying to commercial satellite attitude control are demonstrated by numeric simulations.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.31-37
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• 2016

Purpose: The purpose of this study was to investigate the differences in FT (free-torque) components between non-fatigue and fatigue conditions induced by prolonged running. Methods: Fifteen healthy runners with no previous lower-extremity fractures ($22.0{\pm}2.1$ years of age) participated in this study. Ground reaction force data were collected for the right-stance phase for 10 strides of 5 and 125-min running periods at 1,000 Hz using an instrumented force platform (instrumented dual-belt treadmills, Bertec, USA) while the subjects ran on it. The running speed was set according to the preferences of the subjects, which were determined before the experiment. FT variables were calculated from the components of the moment and force output from the force platform. A repeated-measures one-way ANOVA was used to test for significant differences between the two conditions. The alpha level for all the statistical tests was 0.05. Results: The absolute FT at the peak braking force was significantly greater after 5 mins of running than after 125 mins of running-which was regarded as a fatigued state-but there were no significant differences in the absolute peak FT or impulse between the conditions. Conclusion: The FT variables in the fatigue condition during prolonged running hardly affect the tibial stress syndrome.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.56.5-56
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• 2001

In the three axis control of satellite by using reaction wheel and gyro, a reaction wheel produces the control torque by the wheel speed or momentum, and a gyro carries out measuring of the attitude angle and the attitude angular velocity In this study, dynamic modelling of the Low Earth Orbit (LEO) is consisted of the one from the rotational motion of the satellite with the basic rigid body and a flexible body model, and the gyro in addition to the reaction wheel model. The results obtained by the robust controller are compared with those of the PI (Proportional and Integration) controller which is commonly used for the stabilizing satellite.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.185-191
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• 2001

In many papers, the powertrain system generally has been madeled as one-dimensional torque model. One-dimensional powertrain model may calculate the torque correctly but it does not consider the non-rotational degrees-of-freedom of the powertrain components and the interaction of these degrees-of-freedom with the vehicle body frame and suspension. To consider the non-rotational degrees of freedom, the differential is modeled as a three-dimensional rigid body in this paper. A constant velocity joint is newly formulated and a relative constraint is also formulated to model the motion transfer due to gear ratio of the differential. Implementing the proposed powertrain system in the multibody model, more detail dynamic responses can be obtained. Obtained outputs such as reaction torques on the constant velocity joint and reaction forces on the rack can be useful data in the design of a powertrain.

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.230-236
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• 2007

In this study, a tail rotor system for an agricultural RF controlled helicopter was developed and tested. This study concluded the mechanical development of the 'Agro-heli' by completing the tail rotor system and its radio console. The RF control system was closely related with the tail system for the control of flying attitude. The thrust of the tail system balance off the reaction torque, created by the main rotor. Lifting tests with and without the tail system were compared for estimating the consumption of power. The tail system would use $4{\sim}5%$ of the total power which was in an acceptable range. Flying performance and attitude was visually inspected. It showed reliable and safe control during the distance flying trials and could be adapted for utilization in aerial applications. Aerial application using an RF controlled agricultural helicopter may make precise and timely spraying possible.