Masao Tomisawa

Developing a Device for Measuring and Regulating the Rope Tension of Elevators.

We describes a tension measurement and regulation method for an elevator rope. The rope tension imbalance causes the rope life to be shortened and the sheave groove to become worn in the early stage, and the elevator car riding comfort is decreased. Usually, rope tension measurement is done manually and regulation is carried out by trial and error based on experience. These procedures require much manual labor and corresponding time. Thus, we have developed a rope tension estimation algorithm based on the reciprocating time of the rope acceleration wave generated by hand excitation. Second, we have formulated the relationship between the tension adjustment value and the rope vibration wave reciprocating time. The results of our experiments indicate that the proposed method is able to adjust the tension easily and the accuracy is sufficient for even super highspeed elevators. Lastly, we developed a device for measuring and regulating rope tension. The device is small enough to be carried by hand.

Analysis of Mid-frequency Resonance Phenomenon in Step Motors.

A new method is presented for analysing so-called mid-frequency resonance in a step motor, which is an unstable vibration arising from the interaction between rotor motion and coil current. Firstly, state equation in the time invariant form is derived using the rotating coodinate which is synchronous with the rotor. Secondly, a reduced-order model of 2nd order is obtained from the 4th-order state equation through modeling of a rotor fluctuation mode, in which a particular emphasis is placed on the low-frequency band of the torque transfer function. As a result, mid-frequenty instability can be analytically predicted from an approximated algebraic expression in closed form. Capability of the above approximated algebraic expression is demonstrated with an explanation for the difference of mid-frequency resonance between the hybrid-type motor and claw-type motor.

The relationship of journal bearing loads and alinment conditions of multispan rotors.

This paper presents a method to calculate the static bearing loads of multispan rotors by considering the nonlinear characteristics of oil film bearings. The initial alignment to be installed in the rotor is determined by minimizing the difference of the bearing load from the designed value and the stress of rigid couplings. To investigate the effects of the journal center displacement varying with rotating speeds, an actual turbogenerator system with four couplings and eight bearings is numerically investigated under initial and misaligned conditions. It is shown that the amount and direction of bearing loads strongly depend on rotating speeds under the misaligned conditions, but are negligibly small under the initial condition. To clarify the fundamental properties induced by the misalignment of the rotor system, the load direction effects on the journal center, unbalanced response and stability are investigated for a partial arc bearing.