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Balance control analysis of humanoid robot based on Zero Moment Point (ZMP) feedback control is presented. ZMP is mostly used as standard evaluation of stability of humanoid robot, and balance control is conducted by controlling ZMP position so that it is always in convex hull of the foot-support area. To simplify the design of controller, it is mainly used as one mass inverted pendulum model which represents lower body of humanoid robot model. However this model causes system to become non-minimum phase and performance limitation of the system occurrs, because of the presence of Waterbed effect in frequency domain and unavoidable undershoot in time domain. This paper proposes ZMP feedback control using two masses inverted pendulum model which represents lower and upper body of humanoid robot and creates minimum phase system. The design of the controller based on the proposed model using linear quadratic by considering output is described and confirmed using simulation.

The light-triggered thyristor (LTT), which can be directly fired by light, does not need gate electronics on the high-voltage side and is thus a near-ideal semiconductor device for a HVDC valve. In providing overvoltage protection for an LTT without losing its advantage of simple circuits associated with the thyristor, the overvoltage protection system adopted in the conventional electrically triggered thyristor is not necessarily appropriate. The authors have shown that high-speed protective gate pulses generated from the valve base electronics together with the valve arrester are sufficient for the LTT valve overvoltage protection. The adequacy of this protection strategy is demonstrated by factory type tests and also excellent service experiences.

The Hokkaido-Honshu HVDC link entered service in 1979 for the first phase (150 MW, 125 kV-1200 A) and in 1980 for the second phase (300 MW, 250 kV-1200 A) and has since been operating in good condition. In the Kamikita converter station situated on the Honshu side, the thyristor valves for the first and second phases use 1344 thyristors rated 4 kV-1.5 kA. To examine secular changes in the characteristics of thyristors and estimate their life expectancy, we picked up eight thyristors from the thyristor valves, measured the main characteristics and compared measurements with the corresponding values measured before they entered service. Further, two thyristors were subjected to temperature and voltage acceleration tests to check for a change over time of leakage current. From the results of these investigations it was verified that the thyristors that have been in service for 16 years have the characteristics and service life equivalent to those of the new ones. But further investigation is required as to the change of turn-off characteristics.

In this paper, we will design a path tracking controller for an articulated vehicle with double trailers using time scale transformation and exact linearization technique, which are developed in nonlinear control theory. We will show, in the simulation, that the proposed controller works satisfactorily, and the articulated vehicle with double trailers follows the desired path even when it is moving backward.

The authors propose a method of supporting a thyristor valve using an aseismic isolation system to enhance its seismic performance. In this method, the thyristor valve is supported by laminated rubber bearings with a very small spring constant in the horizontal direction. Its natural frequency is thereby lower than the predominant frequencies of earthquakes and thus decreases conduction of the earthquake motion. Dynamic analysis and structural analysis were conducted for a structure aseismically supported by the method of this study and for a conventional floor-mounted structure. The effects of aseismic support were studied and it was proved that the stress generated was considerably decreased. >

Conceptual designs for convertor substation equipment for a HVDC (high-voltage direct current) transmission system using current- as well as voltage-source-type GTO (gate turn-off thyristors) power convertors (referred to as VSTGC and CSTGC) are presented. A study indicates that the VSTGC is preferable to the CSTGC. Also presented is a preliminary economic comparison between two HVDC-system alternatives for applying power to a weak AC system, one using a self-commutated GTO power convertor and the other combining a line-commutated convertor and a synchronous condenser. The result indicates that the two HVDC convertor substation alternatives cost about the same. >

H/spl infin/ control theory is utilized to design the controller for molten steel surface level in a mold of continuous casting machine installed at Kimitsu Works of Nippon Steel. It is shown that this theory is more effective for unknown process parameter changes and disturbances. First, we show the reason why this control method is introduced. Next, we derive the mathematical model of the plant, and setup the control problem, where the generalized plant is constructed with frequency weighting functions. Finally, experimental results in the real plant is shown. Experiments were carried out in order to evaluate the performance and robustness of H/spl infin/ design compared with the adaptive control design. The results confirm the system designed by H/spl infin/ has better performance of suppressing disturbance and robustness of stable against parameter changes than the system designed by adaptive control under large disturbance. >

The Hokkaido-Honshu HVDC link was increased to 600 MW in 1993. In the DC link, new devices and equipment such as light-triggered thyristors, dead-tank type DC filters and so on, are employed. This DC link features a unique control system, automatic frequency control (AFC), applying modern control theory. This paper describes these new techniques and operating experiences. The Tohoku Region, where one terminal is located, was hit by a large earthquake in 1994, the effects and damage to the equipment is described in this paper.

A sensory feedback controller for a three-dimensional linear-motion mechanical system is proposed. This controller specifies that the end-effector of the mechanical system will follow the path of a laser beam according to the operator's commands. Thus, it is possible to manually position the end-effector by moving the laser beam and specifying whether the end-effector should move forward or backward along its path. This system is ideal for manually operating robots. The sensor is designed to detect both the laser beam's direction and the end-effector's deviation from the beam's path. The experimental results confirm the viability of the proposed system. The controller can also be used for highly accurate servo-control because the position of the end-effector can be directly determined from the laser beam. >