Susumu Tadakuma

Microprocessor-Based Adjustable-Speed DC Motor Drives Using Model Reference Adaptive Control

Model reference adaptive control (MRAC) is applied to microprocessor-based adjustable-speed dc motor drives. The algorithm of the MRAC is based on the linear model following control (LMFC) and is the combination of the adaptive controller with the LMFC. The MRAC-based speed controller allows the indistinctness and/or inaccuracy in the motor and load parameters in the system design stage. It also maintains the prescribed control performance in the presence of the motor parameter perturbations and the load disturbances. The experimental setup is constructed using a microprocessor. The experimental results confirm the useful effects of the MRAC-based speed controller.

A Study of Energy-Saving Shoes for Robot Considering Lateral Plane Motion

In this paper, we propose a flexible shoe system for biped robots to optimize energy consumption of the lateral plane motion. This shoe system is made to deform decline outside in the lateral plane and it can absorb the kinetic energy of the robot in the lateral plane. Furthermore, this hardware (shoes) and software (controller) can be easily applicable to the ordinary walking robot system. The effectiveness and characteristics of this system are confirmed by computer simulations and experimental results. It is confirmed that the stiffness of the shoe is a very important parameter for energy consumption by using computer simulations and experimental results.

A novel multilevel carrier-based PWM-control method for GTO inverter in low index modulation region

Gate turn offs (GTOs) have an inherent minimum ON-OFF time, which is needed for their safe operation. For GTO-based three-level or neutral-point-clamped (NPC) inverters, this minimum ON-OFF pulsewidth limitation results in a distortion of the output voltage and current waveforms, especially in the low index modulation region. Some approaches have been previously proposed to compensate for the minimum ON pulse. However, these methods increase the inverter switching losses. Two new methods of pulsewidth-modulation (PWM) control based on: 1) adding a bias to the reference voltage of the inverter and 2) switching patterns are presented. The former method improves the output waveforms, but increases the switching losses; while the latter improves the output waveforms without increasing the switching losses. The fluctuations of the neutral-point voltage are also reduced using this method. The theoretical and practical aspects as well as the experimental results are presented in this paper.

Characteristics of Linear Synchronous Motor Drive Cycloconverter for Maglev Vehicle ML-500 at Miyazaki Test Track

Maglev vehicle ML-500 in Japan attained a speed of 517 km/h on December 21, 1979. The linear synchronous motor (LSM) drive cycloconverter fabricated and submitted to the track test has a capacity of approximately 12 000 kVA in a continuously variable frequency range of 0-34 Hz with a sinusoidal current waveform. The current can be arbitrarily controlled in a range of 200-1300 A. Despite the rigorous power conversion and control, excellent current control characteristics were obtained: less than 4 percent in deviation of current peak value, about 4 ° in leading phase deviation and approximately 1.2 ms in zero current interval. Some observations about the LSM driving system are made, and an outline of the design and the data obtained from the super-high-speed running tests on Miyazaki test track are given.

Improved PWM control for GTO inverters with pulse number modulation

A pulse width modulated (PWM) inverter using GTOs is one of the promising power converters for AC motor drives. There are, however, still some unsolved problems with GTO inverters: (1) the modulation factor of conventional GTO inverters is limited to about 0.8 in order to maintain the minimum on-time of every GTO. If a modulation factor of 1.0 is possible in the bridge-type inverter, the output capacity would be larger in proportion to the modulation factor. The pulse number modulation (PNM) is proposed as an effective measure for this modulation factor improvement; and (2) the minimum on-time of a GTO brings about uncontrollability for a low voltage reference in the neutral point clamped (NPC) inverter. The authors propose a new procedure using the PNM technique to solve this voltage uncontrollability. The PNM method contributes to make an equivalent unity modulation factor in PWM inverters and to linearize voltage control characteristics in NPC inverters. >

Current Response Simulation in Six-Phase and Twelve-Phase Cycloconverters

Cycloconverters are aptly used for the power supply of variable speed synchronous motors. However, output current offset and phase deviation increase in higher output frequency operation, and ripple current causes torque pulsation of the synchronous motor. A compensating method to improve current response performance is proposed and a digital simulation procedure in order to analyze the output current response of a cycloconverter is discussed. First, the six-phase noncirculating-type cycloconverter is discussed. Next the six-phase cycloconverter simulation was applied to the 12-phase cycloconverter. The simulated waveforms were compared with the experimental results in motor operation or regenerative operation. It was clarified that offset and phase deviation became zero using the compensating circuit. Additionally the average torque pulsation, the output current distortion factor, and the ripple torque versus the output-input frequency ratio were calculated by simulation in the cycloconverter-fed synchronous motor.

Finite-Time Settling Control Based Current Controller for Thyristor Dual Converter

A finite-time settling control (FTSC) is used aptly for digital control systems because of deadbeat performance. A thyristor converter, which is regarded as a voltage controller including a sampler and a holder, apparently is acceptable for FTSC-based current control. The output current of the converter, however, frequently overshoots the reference current on account of time delay due to line commutation. Application of the FTSC method to current control of thyristor dual converters is described. The authors introduce a softening filter, or interpolation method, in addition to the finite-time settling control to maintain a completely deadbeat performance. The proposal is verified by simulations and experiments.

Circulating Current Control For Delta-Connected Cycloconverters Via Decoupling Control

A delta-connected cycloconverter promises high performance and moderate cost for ac motor drives. The circulating current of the cycloconverter is used for controlling the input reactive power. There exists stong interaction between the load current control and the circulating current control. This paper presents the decoupling control method for substantial isolation of both control loops.