• 로봇학회논문지
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• 제19권1호
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• pp.53-57
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• 2024

A hopping robot can move through a confined environment while overcoming obstacles. To create a small hopping robot, it must be able to generate a large amount of energy and release it at the same time. However, due to the small size of the robot, there is a limit to the size of the actuator that can be used, so it is mainly used to collect energy in an elastic element and release it at once. In this paper, we propose a small hopping robot with a simplified design by removing ancillary parts and enabling continuous hopping using only a small actuator based on a direct-drive method. In addition, repeated actuation over the rated voltage can cause thermal breakdown of the actuator. To check the safety of the actuator at high voltage, we perform modeling to predict the temperature of the actuator and verify the accuracy of the modeling through experiments.

• Design & Manufacturing
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• 제14권3호
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• pp.23-30
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• 2020

Laser Assisted Thermo-Compression Bonding (LATCB) has been proposed to improve the "chip tilt due to the difference in solder bump height" that occurs during the conventional semiconductor chip bonding process. The bonding module of the LATCB system has used a piezoelectric actuator to control the inclination of the compression jig on a micro scale, and the piezoelectric actuator has been directly coupled to the compression jig to minimize the assembly tolerance of the compression jig. However, this structure generates a lateral force in the piezoelectric actuator when the compression jig is tilted, and the stacked piezoelectric element vulnerable to the lateral force has a risk of failure. In this paper, the optimal design of the flexure hinge was performed to minimize the lateral force generated in the piezoelectric actuator when the compression jig is tilted by using the displacement difference of the piezoelectric actuator in the bonding module for LATCB. The design variables of the flexure hinge were defined as the hinge height, the minimum diameter, and the notch radius. And the effect of the change of each variable on the stress generated in the flexible hinge and the lateral force acting on the piezoelectric actuator was analyzed. Also, optimization was carried out using commercial structural analysis software. As a result, when the displacement difference between the piezoelectric actuators is the maximum (90um), the maximum stress generated in the flexible hinge is 11.5% of the elastic limit of the hinge material, and the lateral force acting on the piezoelectric actuator is less than 1N.

• Structural Engineering and Mechanics
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• 제44권2호
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• pp.127-138
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• 2012

The composite materials may be exposed to environmental (thermal or hygral or both) condition during their service life. The effect of environmental condition is usually adverse from the point of view of design of composite structures. In the present research study the effect of hygrothermal condition on the design of laminated composite structures is investigated. The active fiber composite (AFC) which may be utilized as actuator or sensor is considered in the present analysis. The sensor layer is used to sense the level of response of the composite structures. The sensed voltage is fed back to the actuator through the controller. In this study both displacement and velocity feedback controllers are employed to reduce the response of the composite laminate within acceptable limit. The Newmark direct time integration scheme is employed along with modal superposition method to improve the computational efficiency. It is observed from the numerical study that the laminated composite structures become weak in the presence of hygrothermal load. The response of the structure can be brought to the acceptable level once the AFC layer is activated through the feedback loop.

• 한국정밀공학회지
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• 제32권6호
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• pp.553-562
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• 2015

This paper presents a strategy and an algorithm for levitation control of an over-actuated passive maglev tray system. The passive maglev tray system has more actuators than its degrees of freedom. The actuators of the system are switching when the tray travels longitudinally. Furthermore, the levitation forces of the actuators are non-homogeneous because the actuation devices are not in the moving platform. These characteristics make a limit in using conventional control approaches for levitation. For smooth actuator switching, the actuator force generation should be dependent on longitudinal positions of the tray. To enable constant pose tracking, this research introduces a control strategy and a control algorithm based on integral controllers on virtual variables. The states of the tray are estimated using a Kalman filter and fed to the proposed controller. The performances of the proposed control strategy and the algorithm are validated through tests.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.484-491
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• 2002

We developed a new type of human-sized BWR (biped walking robot) driven by a new actuator based on the ball screw which has high strength and high gear ratio. Each leg of the robot is composed of three pitch joints and one roll joint. In all, a 10 degree-of-freedom robot with two balancing joints was developed. A new type of actuator for the robot is proposed, which is composed of four bar link mechanism driven by the ball screw. The robot overcomes the limit of the driving torque of conventional BWRs. The BWR was designed to walk autonomously by adapting small DC motors for the robot actuators and has a space to board DC battery and controllers. In the performance test, the BWR performed sitting-up and down motion, and walking motion. Through the test, we found the possibility of a high performance biped-walking.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.615-618
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• 2005

All over the world, many kinds of micro-actuators were already developed for various applications. The actuators are using various principles such as electromagnetic, piezoelectric and thermopneumatic etc. The most of the micro-actuators have been made using 2D based MEMS technology. In these actuators, it is difficult to drive 3-dimensional motion. This characteristic gives the limit of actuator application. However, micro-stereolithography technology has made it possible to fabricate freeform three-dimensional microstructures. In this technology, 2-dimensional micro-shape layer is cumulated on the other layers. This layer-by-layer process is the main principle to fabricate 3-dimensioal micro-structures. In this research, a micro-bellows actuator that is vertically moving was developed using the micro-stereolithography technology. When pressure was applied into the bellows, a non-contact actuating motion is generated. For actuation experiment, syringe pump and laser interferometer were used for applying pressure and measuring the displacement. Several hundreds micro-scale actuation was observed. And, to demonstrate the feasibility of proposed actuation principle, in this research, a micro-gripper was developed using half-bellows structure.

• 한국항공우주학회지
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• 제47권9호
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• pp.607-616
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• 2019

항공우주비행체 정적구조시험을 위한 과하중 방지를 위해 사용되는 하중제한밸브(LLV)의 파일럿 스테이지의 주요 구성품들에 대한 자유물체도 분석을 수행하였다. 이 분석을 통하여 유압작동기의 동일한 힘에서 일관성있게 포펫 개방되도록 하기 위해서는 파일럿스테이지에 있는 두 포펫의 직경비($(D_2)^{ten}/D_2)^{comp}$)가 작동기의 피스톤 면적비($A_{comp}/A_{ten}$)와 동일해야만 한다는 것을 보였다. 실험실에서 외산으로 수입하여 사용하고 있는 4개의 서로 다른 하중제한밸브의 포펫들 형상을 측정하고 대응되는 4개의 다른 용량을 갖는 유압작동기들의 피스톤 면적비들로부터 위의 분석결과가 타당함을 확인하였다. 두 개의 다른 파일럿스테이지로 수행한 "조절자 분해능시험들"의 결과들로부터 조절자 각 회전에서 얻은 Fi(포펫개방 순간의 작동기 힘)의 최대 표준편차는 각 평균값으로부터 0.3KN이고 표준편차를 각 평균값으로 나눈 무차원값으로 분석하면 최대편차는 3.7%이다. 이 결과로 부터 동일 포펫 직경비를 갖는 두 개의 파일럿스테이지들의 포펫은 각 조절자 회전에 대해 Fi/(평균 Fi) 값이 +/- 3.7% 범위에서 일관성 있게 개방되고 있음을 확인하였다. 위의 편차는 포펫 O-링의 마찰력으로부터 유발되는 것임을 보였다. 부가적으로 파일럿스테이지의 다른 주요부품인 포펫 스프링과 조절자의 주요설계인자들도 식별하였고 이들의 결정과정도 본 연구에서 보였다.

• 한국소음진동공학회논문집
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• 제19권8호
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• pp.788-794
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• 2009

Various types of latch designs for hard disk drives using load/unload mechanism have been introduced to protect undesired release motions of a voice coil motor(VCM) actuator from sudden disturbances. Recently, various inertia-type latches have been widely used because locking performance is better than that of other types of latch. However there has been a limit in the inertia type in order to guarantee perfect latch and unlatch operations because of changes in latch/unlatch conditions due to mechanical tolerance and temperature-dependent friction. In this paper, a reliable and robust magnetic latch mechanism is proposed through only simple modifications of coil and yoke shapes in order to overcome the mechanical limit of current inertia-type latches. This new magnetic latch does not have only a simple structure but it also ensures reliable operations and anti-shock performance. The operating mechanism of the proposed latch is theoretically analyzed and optimally designed using an electromagnetic simulation.

• 제어로봇시스템학회논문지
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• 제21권5호
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• pp.471-476
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• 2015

This paper presents a maximum velocity trajectory planning algorithm for differential mobile robots with wheel velocity constraint to cope with physical limits in the joint space for two-wheeled mobile robots (TMR). In previous research, the convolution operator was able to generate a central velocity that deals with the physical constraints of a mobile robot while considering the heading angles along a smooth curve in terms of time-dependent parameter. However, the velocity could not track the predefined path. An algorithm is proposed to compensate an error that occurs between the actual and driven distance by the velocity of the center of a TMR within a sampling time. The velocity commands in Cartesian space are also converted to actuator commands to drive two wheels. In the case that the actuator commands exceed the maximum velocity the trajectory is redeveloped with the compensated center velocity. The new center velocity is obtained according to the curvature of the path to provide a maximum allowable velocity meaning a time-optimal trajectory. The effectiveness of the algorithm is shown through numerical examples.

• 전력전자학회논문지
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• 제11권1호
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• pp.46-55
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• 2006

본 논문은 DC 모터와 MR(magnetorheological) 브레이크를 갖는 하이브리드 구동기의 제어 방법을 제안한다 로봇을 포함하여 여러 영역에서 이용되는 DC 모터는 대표적인 능동형구동기로 중량 대비 출력 이 작고, 출력한계로 인해 어느 정도 이상의 제어 이득에서 힘 제어 특성이 불안정해지는 성질이 있다. 따라서 이러한 DC 모터의 제어 불안정성을 해결하고, 투명성을 높이기 위해 반능동형 구동기인 MR 브레이크를 DC 모터와 병렬로 연결한 하이브리드 구동기를 제안하고 이에 대하여 네트워크 이론에 기반을 둔 제어 방법을 제안한다. 입력전류의 방향에 따라 스스로 출력을 내는 DC 모터와는 달리 MR 브레이크는 입력전류의 부호가 바뀌는 것에 상관없이 외부의 부하와 반대의 출력을 내는 것이 그 특징이다. 이러한 MR 브레이크의 성질을 수동적이라 하고 네트워크 이론의 수동성을 이용한 하이브리드 구동기의 힘 제어 방법을 제안하고 실험을 통해 이의 성능과 안정성을 입증하였다.