In this paper, we present an experimental result of 3-D real-time speed-variable biped walking using our second prototype Ostrich-II. Ostrich-II has 10 degrees of freedom; 6 for sagittal plane and 4 for lateral plane. The synchronization of motions in both planes is very important to realize stable walking. We propose Virtual Inverted Pendulum(VIP) method as the solution. We introduce following two techniques; (a) synchronization of the motions in both planes, (b) realization of synchronized acceleration/deceleration. We made an actual biped machine and its control system. We confirmed the effectiveness of VIP method by laboratory experiment. Ostrich-II realizes variable real-time biped walking, such as steady walking (0.5s/step, 0.1m/s), acceleration( from 0.lm/s to 0.2m/s, etc.), and so on.

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This paper proposes a cooperative motion control strategy of multimanipulator based on workspace disturbance observer with variable compliance gain. The workspace disturbance observer as an acceleration controller provides a simple, robust and flexible controller structure and computation while the addition of variable compliance gain will maintain the performance of the system in free motion as well as in contact conditions. It is assumed that the goal of the system is to move the grasped object tracking the desired motion trajectory in the presence of a stiff contact environment with a relatively constant system's performance. To achieve the goal of system, the motion trajectory control of the cooperative control is realized using an impedance control approach enhanced by a variable compliance gain. The compliance gain is considered as a reflexive response against the interaction force which plays an important role in adjusting the stiffness of the cooperative system. The value of this gain increases exponentially with the increasing interaction force to resemble the response of muscle against an external force disturbance. The experimental results show that the use of variable compliance gain has advantages over that of conventional impedance control aproach such as it does not no longer require a switching mechanism to set the system's compliance according to the object motion condition.

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This paper descrives a design method of two-degree of freedom controllers for a low stiffness positioning system with a reduction gear. The gear apparently reduces the load inatia. This results in the difficulty of estimating torsional torque by a disturbance observer. Therefore. it is difficult to use resonance raito control method for the positioning system. In the proposed system. a state feedback controller(I-PD controller) is designed based on the feedback control theory so that the torsional vibration is significantly restrained. To improve the tracking performance, an adaptive feedforward controller is introduced. The responses of the positioning system for trapezoidal desiredoutput signals are measured. Experimental results demonstrate the effectiveness of the proposed two-degree of freedom controller.

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This paper describes a decentralized control strategy for redundant manipulator with a large degree-of-freedom. Here we introduce a hierarchical impedance control in order to simplify the control system. The proposed controller consists of several subsystems and the dynamic force propagates along them. This means that the total motion of the manipulator is controlled arbitrary according to the propagated force. The controller of each subsystem is constructed independently of the total number of degree-of-freedom and the motion characteristic of each subsystem is determined by using information from only adjoining subsystems. This is one of the remarkable points of our approach and results in a simplification of the total controller. Several simulated and experimental results are shown to confirm the feasibility of our approach.

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When a robot manipulator performs fast motion control, high joint torque is required. Moreover, additional joint torque is necessary to suppress disturbance. However, as an actuator can not produce very high joint torque, the saturation on joint torque occurs. This paper proposes a strategy to solve the saturation problem stated above. The two algorithms called the torque limiting algorithm and the reference adjusting algorithm are introduced. The torque limiting algorithm is applied in order to prevent the saturation of joint torque. Another algorithm called the path reference adjusting algorithm will suppress the deviation on path tracking caused by the limitation. The effectiveness of the proposed method is confirmed by experimental results of a 2-link planar arm manipulator.

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Recent researches of electric vehicle are normally focused on batteries and motors themselves. However electric vehicle can achieve high performance motion control by taking advantage of its excellent controllability. In this paper, we propose “traction control”. First, we clarify the static characteristic of vehicle slip phenomena by introducing “constant slip ratio curve”. Next, we propose “model following control” and “slip ratio control” and show their effectiveness by experiments using a real test vehicle.

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Nonlinear friction in machine elements is one of the inherent nonlinearities, which causes stick-slip motion in very low velocity control range and tracking errors in trajectory control due to the break-away friction and Stribeck effect. Since those greatly affect the control accuracy of servo drive systems, the appropriate modeling and/or compensation for friction is indispensable to achieve the higher performance motion.
The authors have already proposed the compensation scheme for nonlinear friction by using a remarkable disturbance observer which is designed on the basis of Coulomb friction characteristic. In this paper, the dynamic characteristic of nonlinear friction is examined by means of a friction model with elastic bristles between sliding surfaces. The analysis reveals that the nonlinear friction behaves in Coulomb friction under the dynamic motion at velocity reversal and, as a result, it is concluded clearly that the proposed disturbance observer is quite useful to estimate the instantaneous friction. Experimental results using a table drive system show the significant performance improvement of the proposed scheme in precise trajectory control.

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In the controller design of position or velocity control, the flexibility of the mechanical system is always the limiting factor to the higher performance. In this paper, the speed control of a two-mass resonant system, where the speed sensor is located only on the drive motor side, is investigated. Such a system is typically found in steel mill drives. The controller design is made successfully in practical sense using various design techniques, such as classical control, resonance ratio control with disturbance observer, and H_∞ control. However, a unified theoretical approach is needed to understand the real nature of the problem. For this purpose, a new controller design approach, called “Coefficient Diagram Method”, is introduced. The result shows that the optimum controller, in normalized form, is the sole function of the ratio of motor inertia to the total inertia. As the ratio increases, the controller type needed varies from PI control to PI control with lag, and finally to PID control with lag where D control is week positive feedback. The typical controller designed in the past have been compared with this design.

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The high performance drives of PM motor with a sinusoidal back-EMF can be achieved by the current vector control, where the armature current is controlled as a sinusoidal waveform based on the rotor position information and the current phase is suitably controlled according to the operating condition. In such high performance drive system, a high resolution position information is desired. In this paper, a sinusoidal current drive system with a low resolution position sensor is proposed. The high resolution position information is obtained by the position estimating circuit from the signal of a low resolution positionn sensor. The steady-state and transient characteristics are examined by the several experiments, then it is confirmed that the sinusoidal current drive, the high performance current vector control and the speed control can be achieved by the proposed drive system.

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This paper proposes an active noise control system with minimized amount of calculation for periodic noise. A modified algorithm based on the filtered-x adaptive notch filter is applied on the diesel engine noise generated in the cabin of an all-terrain vehicle. Diesel engine noise is periodic and includes some harmonic components due to engine rotation. Numerical simulation results using measured data indicated that the proposed system could be controlled by using fewer calculations compared to the conventional system. The controller was made using an eight bit microcomputer without a digital signal processor and installed in the vehicle. Results of the driving tests achieved a large noise reduction for some harmonic components, second, fourth and sixth order components. This shows that the control system is effective for noise reduction.

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A Superconducting Magnetic Energy Storage (SMES) using superconductive coil is effective power storage system. An electric power system using SMES can perform levelling load power fluctuation and improve the, stability of power system. It is impossible to examine a control strategy for levelling load power fluctuation using a SMES, because we can not realize a large capacity of SMES. So we build a SMES simulator as a trial that operates coordinately as a superconductive coil.
In this paper, a superconductive coil composed of a coil and a inverter curcuit is realized by numerical expression and experiment. The contorol strategy based on an auto-tuning of scailing factors with neural network can realize levelling the fluctuating active power and compensating the reactive power using the SMES simulator.

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This paper proposes a novel multiple power conversion system using voltage source power converters and phase shifting transformer suited for application to power systems. Conventionally, for harmonic elimination, serial composition method of out-put voltages of power converter units using serially connected windings of transformers has been applied. But, the conventional method has imbalance problems of transformer voltages and of voltages of DC-link connected in series. This proposed converter has a transformer with primary windings connected in parallel or with common primary winding. By this method, the imbalance problems can be remarkably solved, and harmonic elimination can be provided. On the other hand, harmonic currents flow between the power converter units. For solving this problem, coupling reactors or leakage transformers are used to suppress harmonic cross currents. And these suppression methods are analyzed in detail. In conclusions, we can see following advantages. (1) Voltage imbalance problems can be remarkably solved. (2) Harmonic problems can be remarkably solved. (3) More high voltage can be realized.

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First of all, the combined alternating torque of small three phase induction motor fed by six stepped wave voltage-source inverter is analysed by the simplified basic model. The various harmonic components of the combined torque are clarified and shown on the look-up table which are consisted of the stator magnetic field and rotor current. Moreover, the causes of these torques are pointed out.
Secondly, the fundamental equations of the combined toruque which are derived from the basic model are expressed by the equivalent circuit parameters. As a result of the simulation of the fundamental equations, the more pracically simplified equations are derived and also the experiment by the laboratory equipment are performed to evaluate the validity. The simplified equations are satisfied the following items; (1) the higher harmonics below the 17th harmonics are neglected, (2) the only actual effective alternating torque components are calculated.
Finally, as a result of comparision between computation and experiment, we confirmed the validity of the simplified equations.

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This paper proposes a new transportation and switching system based on an electric non-contact switching method utilizing the X-YLIM. The characteristics of this new concept were determined based on trail production of the system. This system employs a magnetic-levitation system for the straight sections, and an air-levitation system for the switching part. Thus, it ensures non-contact transportation of a bogie-truck until switching is complete. The degree of freedom of switching has been extended to enable the selection of a wider switching angle range. Based on the test methods employed for the current systems. This experiment has attempted to determine the basic traveling characteristics of bogie-trucks in this new system. The theoretical performance of the system is compared against the experimental values based on the switching orbit equation. Furthermore, this paper discusses the total evaluation of the system utilizing branching performance as the criteria.

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Shinkansen signalling system uses track circuits to detect Shinkansen trains. The basic logic of train signalling is that one train should not be introduced to the section where another train exists. So that the train detection information is very important and treated as absolute information. Track circuit uses rail as a part of electrical transmission line, and detects train by the short circuit which is composed by train axle and the both side rails, so it is very stable and reliable. Furthermore track circuit is used to transmit speed signal information to the train cab via the induction coil on the train. Shinkansen is 25000V A. C. electrified line that there are many harmonic waves in the power supply circuit and obstruct the track circuit current. To avoid this obstruction, Shinkansen track circuit adopts synchronized SSB, Single Side Band, system. This system is very excellent system without a fatal accident during 33 years since Shinkansen had begun its operation in 1964. Nevertheless the electromagnetic environment has been changing with the introduction of the high power rolling stocks with the standstill system like PWM, Pulse Width Modulation, converter, inverter, and so on. As the result of it, non-synchronized noise has increased. Moreover there are several problems in the synchronized SSB system now, for example, information number shortage and so on. So that new type signalling systems are being proposed. To evaluate new system, electromagnetic noise endurance character is necessary. In this paper, precise analysis of the Shinkansen track circuit electromagnetic environment is discussed, and electromagnetic noise endurance character of new type systems are evaluated. Moreover the character research of each system is carried out.

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Performances of vector controlled induction motor are improved by knowing the spacial position of the rotating magnetic flux in the induction motor at every instant. Usually. hole generators are buried in the teeth of the stator for detecting the air gap flux. However, this method is strongly affected with the slot ripple and does not work well due to the high temperature operating condition.
This paper proposes a novel and effective method for detecting the magnetic flux. Zero magnetic field sensor(MFS) is applied, which is buried in the yoke of the stator, since it has a wide operating temperature range (-76_??_300°C) with the high accuracy of 0.1%. Two components, radial component and tangential one, are investigated for which is more fit for the purpose. Both of them include no slot ripple but their wave distortion is inevitable owing to the nonlinearity of the core. Inadition, the value of the detected flux also varies as a function of the mounted position of MFS. Their degree is much smaller in the tangential component than that in the radial one. This signifies that the tangential component is profitable for our purpose. The effect of the wave distortion can be almost completely suppressed by properly arranging three MFSs based on the three phase theory without using any filters. DC flux at zero frequency can also be detected. Effectiveness of the proposed method is verified through these experimental investigation.

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A well known control system which can reduce the adverse effect of a periodic disturbance with single frequency is the disturbance obsever. However, in many cases of industrial systems disturbance frequency is varied for some frequency range. Therefore, it may be difficult to reduce the adverse effect of the disturbance by the use of the traditional disturbance observer.
In this paper, a design method of new disturbance observer which can cope with the frequency variation is proposed. The main idea of this design method is to synthesize the disturbance observer as a gain-scheduled controller. The proposed disturbance observer is constructed as low degree and low gain controller with superior steadystate characteristic. As compared with the traditional disturbance observer and the H∞ controller, the usefulness of the proposed disturbance observer was shown by numerical simulations.

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