• Journal of Industrial Technology
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• v.16
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• pp.113-121
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• 1996

In the early developmental stages of robotics,hydraulics played an important role. As the power-to-weight ratio of electric motors increased, they eventually replaced hydraulic actuators in robot manipulators. Recently, however, task requirements have dictated that the manipulator payload capacity increase to accomodate greater payload, greater length, greater reaction forces, and hydraulic actusators are being studied as an effective form of robot actuation again. For efficient control of hydraulic actuators, the knowledge of its dynamic equation is essential. However, the dynamic equation of hydraulic actuators are nonlinear, and the dynamic coefficients are time varying. In this paper, an estimation algorithm of the dynamic coefficients of the hydraulic piston dynamics are formulated. Simulation results are presented to show the possibility of the parameter estimation.

• Smart Structures and Systems
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• v.5 no.3
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• pp.241-260
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• 2009

Shape control of flexible structures using piezoelectric materials has attracted much attention due to its wide applications in controllable systems such as space and aeronautical engineering. The major work in the field is to find a best control voltage or an optimal placement of the piezoelectric actuators in order to actuate the structure shape as close as possible to the desired one. The current research focus on the investigation of static shape control of intelligent shells using spatially distributed piezoelectric curve beam actuators. The finite element formulation of the piezoelectric model is briefly described. The piezoelectric curve beam element is then integrated into a collocated host shell element by using nodal displacement constraint equations. The linear least square method (LLSM) is employed to get the optimum voltage distributions in the control system so that the desired structure shape can be well matched. Furthermore, to find the optimal placement of the piezoelectric curve beam actuators, a genetic algorithm (GA) is introduced in the computation model as well as the consideration of the different objective functions. Numerical results are given to demonstrate the validity of the theoretical model and numerical algorithm developed.

• Journal of Power Electronics
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• v.14 no.5
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• pp.957-966
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• 2014

Some of DC actuators used in home automation, office automation, medical equipment and automotive systems require a position sensor. In low power applications, the introduction of such a transducer remarkably increases the whole system cost, which justifies the development of sensorless position estimation techniques. The well-known AC motor drive sensorless techniques exploiting the fundamental component of the back electromotive force cannot be used on DC motor drives. In addition, the sophisticated approaches based on current or voltage signal injection cannot be used. Therefore, an effective and inexpensive sensorless position estimation technique suitable for DC motors is presented in this paper. This technique exploits the periodic pulses of the armature current caused by commutation. It is based on a simple pulse counting algorithm, suitable for coping with the rather large variability of the pulse frequency and it leads to the realization of a sensorless position control system for low cost, medium performance systems, like those in the field of automotive applications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.155-160
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• 2001

The road simulator system can simulate the longitudinal, lateral, and vertical movement changed by road conditions and vehicle dynamic characteristics while driving. This system provides the durability evaluation of vehicle suspensions. The system consists of hydraulic actuators, link mechanism, and servo controller. The hydraulic actuators are specially manufactured using low friction seals to endure high speed movement. The link mechanism is designed in order to minimize the dynamic effect during motion and remove the interference between 3axes actuators. The servo controller is composed of sensors, sensor amplifiers - displacement transducers and load cells, and an industrial PC with DSP board which calculates the control algorithm to control hydraulic actuators. The test results are included to evaluate the performance of this simulator comparing vehicle driving test.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.12
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• pp.1049-1054
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• 2015

Nowadays, there are many researches involving structural actuators, which have adjustable stiffness; they are also called variable stiffness actuators (VSA). The VSAs can adjust the characteristics of actuators for various functions and human-machine safety. This paper describes the design and analysis of two types of VSAs. To adjust stiffness, the actuators are controlled by a principle of lever ratio mechanism, by changing a pivot position or a spring position in the structure with springs. To make the principle workable, the designs are simplified by using a ball screw system with a motor. Each structure shows different static properties with variable rates of stiffness. We have also shown the experimental verification of the dynamic performance of the two types of VSAs. This research can be applied to various industrial fields, where humans work in conjunction with robots.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.05a
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• pp.603-606
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• 2004

Automatic test case generation for testing an embedded software is considered. Existing tools for test case generation such as finite state machine or mutant test usually adopt top down approach and depend upon graphical transition and decision table, which makes it difficult to find out where the bugs exist. Also it is hard to describe the special features of embedded systems such as concurrent execution of individual components. Most of embedded systems interacts with the real world, receiving signals through sensors or switches and sending output signals to actuators that somehow manipulate the environment. Embedded software controls the entire system based on the logics such as interpreting the sensor inputs and making the actuators to start or stop their intended operation. This study proposes an automatic test case generation procedure that tests the system starting from the control logics of sensors, switches and actuators and then their concurrent execution controls, and finally the entire system operation. Such a stepwise approach makes it easy to generate test cases to tell where the bugs of embedded software exist.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.14-21
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• 1993

Pneumatic actuators have greater power to weight ratio than electric ones, but they have been rarely used as robotic actuators because of poor accuracy resulted from nonliearity of air. On the other hand, electric servo motors have glld controllability, but they have poor power to weight ratio. For the heavy load handling robot a combined actuating method was developed for vertical and horizontal axes of RISTBOT-ll which handles up to 250kgf load. In this paper, the control method is implemented and analyzed for the manufactured heavy load handling robot.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5409-5415
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• 2012

Piezo ceramic actuator is used for various industrial products such as spray, dispenser, and valve control etc. Since the deflection of the piezo ceramic element depends on the applied voltage, it is required a power amplifier with high voltage supply for driving the piezo ceramic actuators. In this paper, we develop a simple H-bridge type power amplifier and a compact flyback type high voltage switching mode power supply for piezo ceramic actuators. It is easy to adjust the amount of energy input to piezo ceramic actuator by pulse-width-modulation with H-bridge type power amplifier.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.90-92
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• 2008

A novel solving technique has been developed to analyze the dynamic characteristics of high speed Thomson-coil arc eliminator. The electromagnetic repulsion actuator based on Thomson-coil is taken as the driving part of the arc eliminator, due to which, the opening and closing time is quite short compare to other type actuators. The electromagnetic repulsion actuator is composed of one repulsion plate and two fixed coils, corresponding to the opening coil and closing coil, respectively. The new solving technique is derived based on the equivalent electric circuit model of the system which is set up by dividing the repulsion plate into multi segments using adaptive segmentation method. This solving technique is applied to the dynamic characteristic analysis of electromagnetic repulsion actuators in high speed Thomson-coil arc eliminators. The calculation results are testified by the FEM calculation results and experiment results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1585-1591
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• 2010

DMFC uses oxygen by reactants. Therefore, cathode electrode must contact with outside air. However, when used in mobile devices, the user's body by blocking the air intake on the oxygen supply DMFC con not. DMFC to supply air to the cooling fan is used. However, by using cooling fan, air inlet to the pressure loss and changes will occurs, the output will be worse. In this paper, we designed air supplying system using piezo actuators. We DMFC evaluation system was implemented, verified the performance of air supplying system. And the operation was connected to an MP3 player.