Takao Torii

Design and Workout of ACROSS Transmitters Using Air Bearings

Abstract The generation and extraction of heat due to inherent friction at the ball bearings to support the large force is an important technical problem in current seismic ACROSS transmitters of the rotary type for stable maintenance and routine operation for continuous active monitoring over years. This paper proposes the use of gas bearings to improve the relevant situation, since they are expected to be useful in reduction of heat generation and energy loss to eliminate the peripheries for heat extraction. Since no experience has been reported so far to sustain the eccentric rotor by gas bearings, we made some test experiments of eccentric rotors supported by air bearings, and we confirmed that they are ideal for supporting the centrifugal force generated by rotation of an eccentric rotor for the ACROSS transmitters of the next generation, if it is designed appropriately to meet our utility purposes.

Improving task skill transfer method by acquiring impedance parameters from human demonstration

This paper addresses how to acquire reusable robot skills for practical tasks based on a programming by demonstration approach. Specifically, this paper aims at improving the task skill transfer method, which has been proposed by the authors, by acquiring impedance parameters and equilibrium trajectories simultaneously from demonstration data. First, the overview of the task skill acquisition method is described. Then, how to acquire the impedance parameters is discussed. Finally, the effectiveness of the proposed method is verified by experiments.

Numerical Integration Method to Determine Periodic Solutions of Nonlinear Systems

A new method to obtain periodic solution of nonlinear systems is proposed by combining secant method with numerical integration. This method can be applied to nonlinear systems with discontinuous characteristics without special treatment. To check the validity of the proposed method, we applied this method to nonlinear systems with discontinuous characteristics, such as piecewise linear spring system, system with Coulomb’s friction and impact damper system. Comparing the results by the proposed method with the results by simple numerical integration or experimental results, the validity of the proposed method is confirmed.Copyright

Experimental Identification of the Resistance at the Pairs of a Link Mechanism.

It is necessary for design of a link mechanism to grasp the input torque property, but it is difficult to calculate it theoretically because of the existence of resistance at the pairs. In this study, we propose a method that can be used to identify the resistance at the pairs experimentally. For this purpose, it is supposed that the resistance at the pairs is proportional to the relative velocity of pairs. Based on this assumption, the equation of motion of the link mechanism with the resistance at the pairs is derived. Then, the resistance coefficients of the equation are identified by using experimental data. As an example, we apply the proposed method to a simple slider-clank mechanism, and confirm its validity.

Experimental Identification of Input Torque Property of Link Mechanism.

It is difficult to calculate input torque of a complicated link mechanism theoretically. It is also difficult to calculate the input torque of a link mechanism with friction. In this study, we propose a method which can be used to identify the input torque property of link mechanism, such as the equivalent moment of inertia, experimentally. For this purpose, the input torque property of a system is expressed in the form of Fourier series with respect to the crank angle. The measured torque is also expanded in Fourier series. By comparing the coefficients of the series, we can determine the input torque property. Friction torque is separated by comparing the input torque during clockwise or counterclockwise rotation. As an example, we apply the proposed method to a simple sliderclank mechanism, and the validity of the proposed method is confirmed.

Proposition of an incremental transfer matrix method for nonlinear vibration analysis.

A new transfer matrix method is proposed which can be used to analyze steady-state responses of nonlinear multi-degree-of-freedom systems. For proposing the method, the quantities describing the dynamic state of the system are expressed in the form of Fourier series, and formulation is made with respect to the increments in the Fourier coefficients. As numerical examples, the method is applied to the analysis of harmonic as well as subharmonic oscillations of a three-degree-of-freedom system. By comparing the results of the method with those of numerical integration of the equations of motion, the validity of the proposed method is confirmed.