• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.155.4-155
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• 2001

This paper deals with the inertia property-based redundancy resolution in posture control of a mobile manipulator. As a measure for the redundancy resolution of a mobile manipulator, an effective inertia at the end effector in the operational space is proposed and investigated. The reduced effective inertia has a significant effect on reducing the impulse force in collision with environment. To find a posture satisfying both the reduced inertia and joint limit constraints, we propose a combined potential function method that can deal with multiple constraints. The proposed reduced inertia property algorithm is integrated into a damping controller to reduce the impulse force at collision and to regulate the contact force in mobile manipulation ...

• Structural Engineering and Mechanics
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• v.35 no.1
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• pp.53-65
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• 2010

The rigid body inertia properties of a structure including the mass, the center of gravity location, the mass moments and principal axes of inertia are required for structural dynamic analysis, modeling of mechanical systems, design of mechanisms and optimization. The analytical approaches such as solid or finite element modeling can not be used efficiently for estimating the rigid body inertia properties of complex structures. Several experimental approaches have been developed to determine the rigid body inertia properties of a structure via Frequency Response Functions (FRFs). In the present work two experimental methods are used to estimate the rigid body inertia properties of a frame. The first approach consists of using the amount of mass as input to estimate the other inertia properties of frame. In the second approach, the property of orthogonality of modes is used to derive the inertia properties of a frame. The accuracy of the estimated parameters is evaluated through the comparison of the experimental results with those of the theoretical Solid Work model of frame. Moreover, a thorough discussion about the effect of accuracy of measured FRFs on the estimation of inertia properties is presented.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.81.4-82
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• 2016

Recent analysis on asteroidal thermophysical property revealed that there is a tendency that their thermal inertia decrease with their sizes at least for main belt asteroids. However, little is known about the thermal properties of comet-like bodies. In this work we utilized a simple thermophysical model to calculate the thermal inertia of a bare nucleus of comet P/2006 HR30 (Siding Spring) and an asteroid in comet-like orbit 4015 Wilson-Harrington from AKARI observation data. It is also shown that the determination of their thermal inertia is very sensitive to their spin vector, while the diameter is rather easy to be constrained to a certain range by combining multi-wavelength observational data. Thus, we set diameter and hence the geometric albedo as fixed parameters, and inferred the spin vector and thermal inertia of the targets. Further detailed analyses on these cometary bodies will shed light on our understanding of the detailed surfacial characteristics of them.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1-4
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• 2005

This paper describes work on isolation of vibration related engine by a hydraulic engine mount with controllable area of inertia track. Automotive engine mounts are required to constrain motion of engine shake resulting from low-frequency road input of shock excitation and also to isolate noise and vibration generated by the engine with unbalanced disturbance at the high frequency range. The property of the mount depends on vibration amplitude and excitation frequency, which means that the excitation amplitude is large in low excitation frequency range and small in high frequency range. In this paper, theoretical works with model of the mount to reduce vibrations related engine were conducted. The volumetric stiffness of the mount is greatly changed according to the switching the area of the inertia track. Therefore, when the area of the inertia track is tuned, the transmissibility of the mount is effectively reduced.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1969-1982
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• 2015

The virtual inertia control (VIC) of wind turbine with directly-driven permanent-magnet synchronous generator (D-PMSG) can act similarly to the conventional synchronous generator in inertia response and frequency control, thereby supporting the system frequency stability. However, because the wind speed is inconstant and changeable to a certain extent and the D-PMSG is a complex nonlinear system, there are great difficulties in the virtual inertia optimal control of the D-PMSG. Based on the design principle of the active disturbance rejection control (ADRC), this paper presents a new VIC strategy for the D-PMSG from the perspective of power disturbance suppression in the system. The strategy helps fulfill the power grid disturbance estimation and compensation by means of the extended state observer (ESO) so as to improve the disturbance-resisting performance of the system. Compared with conventional proportional-derivative virtual inertia control (PDVIC), this method, which is of better adaptability and robustness, can not only improve the property of the D-PMSG responding to the system frequency but also reduce the influence of wind speed disturbance. The simulation and experiment results have verified the effectiveness and feasibility of the VIC based on the ADRC.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1190-1193
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• 2004

The purpose of this study is to evaluate the possibility of identifying joint damping property through commercially available isokinetic ergometer (BIODEX). The proposed method is to estimate the damping torque of the knee joint from the difference between the external joint torque for maintaining isokinetic movement and the gravity torque of the lower leg. The damping torque was estimated at various joint angular velocities, from which the damping property would be derived. Measurement setup was composed of the BIODEX system with an external force sensor and Labview system. Matlab was used in the analysis of the damping property. The experimental result showed that the small variation in angular velocity due to acceleration and deceleration of the crank arm resulted in greater change of inertial torque than the damping torque, so that the estimation of damping property from the isokinetic movement is difficult.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.190-194
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• 2005

There is a great demand of micro-actuators for mobile information devices such as SFF optical drives and mobile camera phones. However, conventional magnetic coils of electromagnetic motors are a major obstacle for miniaturization because of their complicated structures and large power consumption. In this paper, a linear ultrasonic motor to actuate focusing lens of mobile devices is proposed. The new actuator uses a ring type bimorph piezoelectric material, and $d_{31}$ mode is adopted for applying linear motion. The interaction between inertia force and friction force makes linear motion by high-frequency saw signal input. The saw signal gives steady forces on the one direction by asymmetric inclination property of the signal itself on time domain. A commercial FEM (ANSYS) was used in this investigation for simulating structural analysis, identification of dynamic property, such as resultant displacement and coupled analysis with piezoelectric material. To evaluate the performance of the new design, a prototype was manufactured and experiments were carried out. Experimental results show the actuator motion of 1.52 mm/s at 10 kHz input signal in 5 V.

• Transactions of the Society of Information Storage Systems
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• v.2 no.4
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• pp.251-256
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• 2006

There is a great demand of micro-actuators for mobile information devices such as SFF optical drives and mobile phone cameras. However, the magnetic coils used in conventional electromagnetic motors are a major obstacle for the miniaturization because of their complicated structures and large power consumption. In this paper, a linear ultrasonic motor to actuate focusing lens of mobile devices is proposed. The new actuator uses a ring type bimorph piezoelectric material, and $d_{31}$ mode is adopted for applying linear motion. The interaction between inertia force and friction force makes linear motion by high-frequency saw signal input. The saw signal gives steady forces on the one direction by asymmetric inclination property of the signal itself on time domain. A commercial FEM(ANSYS) was used in this investigation for simulating structural analysis, identification of dynamic property, such as resultant displacement and coupled analysis with piezoelectric material. To evaluate the performance of the new design, a prototype was manufactured and experiments were carried out. Experimental results show the actuator motion of 5.4 mm/s at 10V saw signal of 41 kHz.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.149-164
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• 2021

Most of high-rise buildings in Japan^*1 are structure with damping systems recently. The design procedure is performance-based design (PBD), which is based on the nonlinear response history procedure (NRHP) using 2 or 3-dimentional frame model. In addition, hysteretic property of steel plates or velocity-dependent property of viscous dampers are common practice for the damping system. However, for the selection of damping system, the easy dynamic analysis of recent date may lead the most of engineers to focus attention on the maximum response only without thinking how it shakes. By nature, the seismic design shall be to figure out the action of inertia forces by complex & dynamic loads including periodic and pulse-like characteristics, what we call seismic ground motion. And it shall be done under the dynamic condition. On the contrary, we engineers engineers have constructed the easy-to-use static loads and devoted ourselves to handle them. The structures with damping system shall be designed considering how the stiffness & damping to be applied to the structures against the inertia forces with the viewpoint of dynamic aspect. In this paper we reconsider the role of damping in vibration and give much thought to the basic of shake with damping from a standpoint of structural design. Then, we present some design examples based on them.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.891-898
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• 2005

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint race, and energy required lot welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy amount of upset. working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine. superalloy Nimonic 80A for valve head of 540mm and high alloy SNCrW for valve stem of 115mm. Due to different material characteristics such as, thermal conductivity and flow stress. on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and Parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the Predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters. especially for welds for which are very expensive materials or large shaft. Many kinds of tests, including macro and microstructure observation, chemical composition tensile , hardness and fatigue test , are conducted to evaluate the qualify of welded joints. Based on the results of the tests it can be concluded that the inertia welding joints of the superalloy exhaust valve spindle are better properties than the material specification of SNCrW.