Levitation-guidance stabilization of superconducting maglev through LSM currents
This paper presents a modeling and simulation of a superconducting maglev vehicle with a levitation and guidance assist method we have proposed. The assist system stabilizes and assists the vehicle operation so that the vehicle does not need to depend on the mechanical wheels as much as possible at low speeds. By controlling the LSM armature currents, the auxiliary levitation and guidance forces are provided. The results show that the assist system produces appropriate levitation and guidance forces, establishing the reference levitation height and a sufficient guidance at low speeds even against the disturbance force of lateral wind.
Investigation of superconducting linear synchronous motor propulsion control via an exact mathematical model
This paper describes the performance of the superconducting linear synchronous motor control system used for a transportation vehicle by using an exact dq0-axis mathematical model. The paper first shows the detailed block diagram of the speed control system, which includes the blocks of propulsion force and speed emf computations. A detailed discussion is devoted to the design of the control system. A cascade control system with PI controllers is designed as a numerical demonstration. It is also pointed out that the cascade control structure is a natural form for the power feeding method with three inverters. Performance simulations are shown for severe track conditions such as tunnel and track gradients as well as in a normal case. It is demonstrated that integrator windup of the speed controller can occur in the case of a severe condition in which one of the inverters is disabled. We present a design with more robustly stable performance by designing an antiwindup controller. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 45–52, 1999
Refinement of crystal structure parameters using convergent‐beam electron diffraction: the low‐temperature phase of SrTiO3
The method to refine crystal structure parameters (atom positions and Debye–Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO3. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be \varphi = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.