• Proceedings of the KIPE Conference
• /
• 2002.07a
• /
• pp.443-446
• /
• 2002

Brushless DC motor(BLDCM) are suitable to operate in a wide speed range, easy to control and since there are no mechanical brushes and commutators, require low maintenance costs and are free from restrictions of application environment. And since the ratio of instantaneous torque and rated torque is high, BLDCM are appropriate for variable speed operation. This paper proposes the optimal model by using Matlab/simulink based on modelling and characteristic analysis of trapezoidal back EMF type BLDCM and verifies the validity of the proposed model by applying control systems.

• Journal of KSNVE
• /
• v.7 no.5
• /
• pp.853-860
• /
• 1997

For this study, the multi-degree of freedom analysis model of torsional vibration was developed. This model is combined with mass moment of inertia and torsional spring in two wheel drive and four wheel drive vehicle. We compared and analyzed torsional vibration characteristics by natural frequencies and mode shapes which are obtained by free vibration analysis of this model. And we studied torsional vibration contribution of driveline elements by performing the forced vibration analysis of engine excitation torque. The validity of this model is demonstrated by the field test. The reduction effect of the torsional vibration along the driveline design factor is presented by the analytical results.

• Journal of Drive and Control
• /
• v.15 no.3
• /
• pp.1-7
• /
• 2018

Humanoid robots have fascinated many researchers since they appeared decades ago. For the requirement of both accurate tracking control and the safety of physical human-robot interaction, torque control is basically desirable for humanoid robots. Humanoid robots are highly nonlinear, coupled, complex systems, accordingly the calculation of robot model is difficult and even impossible if precise model of the humanoid robots are unknown. Therefore, it is difficult to control using traditional model-based techniques. To realize model-free torque control, time-delay control (TDC) for humanoid robot was proposed with time-delay estimation technique. Using optimal walking trajectory obtained by particle swarm optimization, TDC with proposed scheme is implemented on whole body of a humanoid, not on biped legs even though it is performed by a virtual humanoid robot. The simulation results show the validity of the proposed TDC for humanoid robots.

• Ocean Systems Engineering
• /
• v.14 no.2
• /
• pp.141-156
• /
• 2024

The turbine system converts the kinetic energy of water flow to electricity by rotating the rotor in a restricted waterway between the seabed and free surface. A turbine system's immersion depth and rotation direction are significantly critical in the turbine's performance along with the shape of the rotor. This study has investigated the hydrodynamic performance of the Savonius hydrokinetic turbine (SHT) according to the immersion depth and rotation direction using computational fluid dynamics (CFD) simulations. The instantaneous torque, torque coefficient, and power coefficients are calculated for the immersion ratios Z/D ranging [0.25, 3.0] and both clockwise (CW) and counterclockwise (CCW) rotations. A flow visualization around the rotor is shown to clarify the correlation between the turbine's performance and the flow field. The CFD simulations show that the CCW rotation produces a higher power at shallow immersion, while the CW rotation performs better at deeper immersion. The immersion ratio should be greater than the minimum of Z/D=1.0 to obtain the maximum power production regardless of the rotation direction.

• Journal of Power Electronics
• /
• v.6 no.1
• /
• pp.38-44
• /
• 2006

In this paper, a speed sensorless control for an ultrasonic motor (USM) using a neural network (NN) is presented. In the proposed method, rotor speed is estimated by a three-layer NN which adapts nonlinearities associated with load torque and motor temperature into control. The intrinsic properties of a USM, such as high torque for low speeds, high static torque, compact size, etc., offer great advantages for industrial applications. However, the speed property of a USM has strong nonlinear properties associated with motor temperature and load torque, which make accurate speed control difficult. These properties are considered in designing a control method through the application of mathematical models. In these strategies, a detailed speed model of the USM is required which makes actual applications impractical. In the proposed method, a three-layer NN estimates the speed of the USM from the drive frequency, the root mean square value of input voltage and the surface temperature of the USM, where no mechanical speed sensor is needed. The NN speed based estimator enables inclusion of variations in driving conditions due to input signals of the NN involved during the driving state of the USM. The disuse of sensors offers many advantages on both the cost and maintenance front. Moreover, the model free sensorless control method offers practical controller construction within a small number of parameters. To validate the proposed speed sensorless control method for a USM, experiments have been executed under several conditions.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.55.4-56
• /
• 2018

Linear Astigmatism Free - Three Mirror System (LAF-TMS) is the linear astigmatism free off-axis wide field telescope with D = 150 mm, F/3.3, and $FOV=5.51^{\circ}{\times}4.13^{\circ}$. We report the design and analysis results of its mirrors and optomechanical structures. Tolerance allowance has been analyzed to the minimum mechanical tolerance of ${\pm}0.05mm$ that is reasonable tolerance for fabrication and optical alignment. The aluminum mirrors are designed with mounting flexure features for the strain-free mounting. From Finite Element Analysis (FEA) results of mounting torque and self-weight, we expect 33 - 80 nm RMS mirror surface deformations. Shims and the L-bracket are mounted between mirrors and the mirror mount for optical alignment. The mirror mount is designed with four light-weighted mechanical parts. It can stably and accurately fix mirrors, and it also suppresses some of stray light.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.05a
• /
• pp.211.1-211.1
• /
• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1993.04b
• /
• pp.185-191
• /
• 1993

A flexible nanipulator can move in the high speed even with the small driving torque. The dynamic equations of flexible manipulator whichinclude 2 vibrationalmodes are derived using the clamped-free boundarycondition. Simulation results of the 6th order modelare well matched with experimental results. The hub angle of the flexible manipulator can be controlled without vibration of beam by the feedback of both hub angle and strain. The overshoot of the hub angle in the step resonse is reduced without sacrificing the rise time using the cycloidal function instead of the step function as the reference input.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1598-1602
• /
• 2003

The parallel-type mechanism provides more accurate and stiff motion than the serial-type mechanism. However, in case of using the haptic device, the performance of the force reflection can be deteriorated due to the singular points existing in workspace. In this paper, we propose a redundantly actuated parallel 3-DOF haptic device, which is singularity-free in the workspace and has an improved force reflection capability. In addition, we propose a new force distribution algorithm, which can reflect force of both high and low resolution, using two sets of actuator with different size. Redundant actuators are attached to the base frame in order to minimize the inertia of the system. Moreover, a wire and gear reduction system is employed to achieve high force reflection along with soft feeling. We confirm the performance of the force reflection capability throughout simulation.

• Proceedings of the KAIS Fall Conference
• /
• 2010.11b
• /
• pp.785-787
• /
• 2010

It is well known that most power steering systems obtain the power by a hydraulic mechanism. Therefore, it consumes more energy because the oil power should be sustained all the times. Recently, to solve this problem the Electric Power System(EPS) or Motor Driven Power System(MDPS) has widely equipped in passenger vehicles. In this research the concurrent simulation technique for an EPS system with MATLAB/SIMULINK and a full vehicle model has been developed. The dynamic responses of vehicle chassis and steering system are evaluated. Then, a full vehicle model interacted with EPS control is concurrently simulated with an impulsive steering wheel torque input to analyze the stability of 'free control' or hands free motion for SUV. This integrated method allows engineers to reduce the prototype testing cost and to shorten the developing period.