Papers by Keyword: Levitation Mass Method

Abstract: Dynamic-error caused by the mass attached to the sensing part of a force transducer is experimentally investigated using the Levitation Mass Method (LMM), in which the dynamic-force applied to the force transducer is measured based on the definition of force, i.e. the product of mass and acceleration. It is experimentally proved that the change in the dynamic correction coefficient (DCC) is proportional to the additional mass as expected by the theory. The effective mass and the effective spring constant of the transducer with the additional mass are estimated from the experimental result. It is experimentally proved that the DCC for the transducer with the additional mass can be calculated using the estimated properties, i.e. the effective mass and the effective spring constant, and the dynamic-error can be corrected with the calculated DCC.

Abstract: At present, a method for evaluating dynamic characteristics of force sensors against small and short-duration impact forces has been developed. In this method, a small mass collides with a force sensor and the impact force is measured with high accuracy as the inertial force of the mass. A pneumatic linear bearing is used in order to realize linear motion with sufficiently small friction acting on the mass, i.e., the moving part of the bearing. Using this method, the dynamic characteristics of the force sensor are evaluated in detail: small and various-duration impact forces with maximum values of approximately 0.4-6.0 N and full width at half maximum (FWHM) of approximately 0.6-2.8 ms are applied to the force sensor and the impact responses of the force sensor are evaluated.

Abstract: Impact response of contact lenses is measured using the Levitation Mass Method (LMM). In the LMM, a small mass collides with contact lenses and the impact force is measured with high accuracy as the inertial force of the moving part. A pneumatic linear bearing is used to achieve linear motion with sufficiently small friction acting on the moving part. Hysteresis loop and consumed energy as mechanical characteristics of contact lenses are also calculated.

Abstract: The requirements for evaluating the mechanical characteristics of materials have increased in the various industrial, research and the applications such as materials testing. Therefore, the authors have proposed a method for measuring force acting a material using pendulum [1]. In the Material tester, the mechanical characteristics of material against small force are measured by means of the pendulum mechanism based on the levitation mass method (LMM) [2,3,4].In the LMM, the Doppler shift frequency is measured for measuring the inertial force. The Doppler shift frequency of a laser beam reflected from the mass is accurately measured by using optical interferometer. The velocity, position, acceleration and inertia force of the mass are calculated from the measured time-varying Doppler shift frequency. Thus, the accurate measure of frequency makes that of force.

Abstract: This paper reviews the present status and future prospects of the levitation mass method (LMM), which is a precision mechanical measurement method. The LMM has been proposed and improved by the author for 10 years. The force generated by the actuator is measured as the inertial force of the mass levitated with sufficiently small friction using an aerostatic linear bearing and connected to the moving part of the actuator. During the measurement, the Doppler shift frequency of the laser beam reflected by the mass is measured with a high accuracy with the help of an optical interferometer. Subsequently, the velocity, position, acceleration, and inertial force of the mass are calculated using based on this frequency. Simultaneously, the current and voltage supplied to the actuator are measured.

Abstract: A method for reducing the size and cost of optical system for precision measurement based on the Levitation Mass Method (LMM) is proposed. In the LMM, a mass levitated using a pneumatic linear bearing with sufficiently small friction is made to collide with the object being tested. The velocity and acceleration of the mass are measured using a compact optical interferometer. The size of the optical system can be drastically reduced by using a planar lightwave circuit (PLC), in which several optical elements are arranged on a planar surface of a silica or semiconductor substrate. Several applications of the PLC to precision measurement will be discussed.

Abstract: A testing method for precision force measurement using a small pendulum based on the levitation mass method (LMM) has been developed. In this method, the force acting on the material to be tested is measured using an optical interferometer. In this paper, a collision test of the spring and the pendulum is performed. As the result of the test, the maximum force on the spring was evaluated as approximately 0.533 N. To demonstrate the performance of the developed instrument, the impact responses of the pendulum are accurately evaluated. The possible applications of the developed method are also discussed.

Abstract: In this paper, dynamic response of 1-inch hard disk drive (HDD) head arm assembly (HAA) against an impact load is obtained by means of a 3D non-linear finite element model in ANSYS/LS-DYNA and experiments using Optical method. A mass is modeled as a rigid body and is made to collide with the arm. The velocity, displacement, acceleration and the inertial force of the mass are obtained from the time- history of finite element analysis (FEA). In the experiment, a mass that is levitated with an aerostatic linear bearing, and hence encounters negligible friction, is made to collide with the HAA and the dynamic bending test for the arm is realized. During the collision the Doppler frequency shift of the laser beam reflecting from the mass is accurately measured using an optical interferometer. The velocity, the position, the acceleration and the inertial force of the mass are calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental data and FEA results is observed.

Abstract: This paper reviewed the present status and the future prospects of a method for precision mass and force measurement based on levitation mass method (LMM). The LMM has been proposed and improved by the author The mass which levitated using a pneumatic linear bearing in LMM is used to producte a inertial force which used as the reference force applied to the objects under test, such as to force sensor calibration, material and structure test. The inertial force is calibrated only from Doppler shift frequency. The stability of laser’s wavelength has improved in the LMM. The futhure work and the method to improve the precision have described.