In a speed control system used a low resolution rotary encoder, the unstable phenomena is caused by the long pulse period in extremely low speed region. Currently, a speed estimation method utilizing the disturbance observer is applied to suppress it. But this method required highly precise speed detection. So, in order to improve the speed detection characteristics, the speed measurement circuit is increased to four circuits, which number is same as the pulse edge types. And the measurement periods are overlapped each others.
Furthermore, the fluctuation of a static friction at zero speed region cannot be estimated. So there is a problem of the speed hunting phenomena. Therefore, by applying the upper limit information in place of speed detection and continually operating the observer, the torque and speed estimation are corrected more accurately.
It was confirmed through experiments that by applying the above mentioned technology, it is possible to obtain a stable and high speed response characteristic from zero speed to high speed regions.

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Recently, many researches for vibration suppression control of 2-mass systems have been reported because the effects of non-stiff coupling cannot be ignored when a faster speed response is required for motor driving systems. An observer based approach is one of the representative methods to suppress the vibration which assumes that the disturbance torque changes very slowly, or even is constant during the sampling period, and uses a disturbance observer to estimate the tortional torque. And the systems are almost analyzed as continuous time ones. But in case that the system is composed of small equipment, the resonance frequency becomes high enough to be close to the sampling frequency of the speed detector, so we have to use high gains for the observer with the result that the noise and parameter error have strong effects on the calculation of the observer.
In this paper, treating the system as a discrete time one, we propose a novel vibration suppression control method. Assuming that the torsional torque is composed of a periodic component and dc component, we use PI type controller for the speed control system and feed the estimation torque forward to the current reference to suppress the vibration. Experimental results show the validity of the proposal method.

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The ultrasonic motor has an excellent performance and many useful features, which electromagnetic type motors do not possess, such as high torque, low speed, compactness in size, no electromagnetic interferences and so on. Particularly, this motor has a large holding torque and a high response characteristic. So, it has been expected to use as position servomotor. The driving principle of ultrasonic motors is, however, different from those of electromagnetic type motors and its mathematical model has not been developed yet. Moreover, its speed characteristics vary with the driving conditions. Therefore, it is difficult to control ultrasonic motors with high performance. In this paper, the position control method of this motor by adaptive control is proposed. The usefulness and validity of proposed control method is examined in experiment.

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This paper describes a new type high torque induction motor which has the rotating magnets in the rotor. The motor basically consists of a usual stator, cylindrical rotor, and inner cylinder of which surface is covered by a set of magnets. The rotor turns at somewhat less than synchronous speed. The inner cylinder with magnets can revolve freely against a rotor shaft. The magnets revolve synchronized the rotating magnetic field induced by the stator current. The magnets make the flux in the rotor. Then we can expect torque increase by the increase of the flux. The results of magnetic field analysis indicate the flux is increased.
In the experimental results of a test motor which is 400W prototype machine, we have obtained the torque increase by approximately 20% as anticipated in the magnetic field analysis. Moreover, test results show improvements of efficiency and power factor in the motor operations. The efficiency of the test motor is obtained as high as 10% at the rated output than those of a same size conventional induction motor. Although power factor of conventional induction motor is lagging at all times, the test motor can be operated with near unity, leading or lagging by adjusting the AC supplied source voltage.

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This paper presents the latest feasible traveling-wave type ultrasonic motor (USM)-actuated positioning servo driver suitable for some application specific direct-drive motion systems which effectively incorporates the practical and reliable fuzzy-reasoning software controller with speed and position variable feedback schemes. A novel high performance and high precision USM-actuated direct-drive servo position control system treated here is composed of the traveling-wave type USM, directly-coupled mechanical loads, two-phase high frequency load resonant soft-switched inverter with the variable frequency regulation scheme for the USM, high-frequency DC-DC boost chopper with the voltage amplitude regulation scheme for the USM, pulse-encoder mounted to the USM and its signal processing interface for a position detection as well as the computer-based fuzzy-reasoning controller. The trially-produced new position servo driver breadboard using the inverter-fed USM is feasibly implemented and the particular software of fuzzy-reasoning controller is to be designed on the basis of the specific USM characteristics and inherent USM-related control minor loops. The experimental results of this USM position servo driver operating at two-phase high-frequency resonant inverter are illustrated and evaluated using one-axis servo motion drive system from a practical point of view. It is practically proved that a new precise position servo motion drive system using the compact USM which incorporates microprocessor-based two-inputs and one-output fuzzy-reasoning controller is to be able to be cost-effective and more acceptable for special-purpose directdrive servo motion control systems in the state-of-the art industrial, medical, automotive, space and consumer utilizations.

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In this paper, two design methods for two-degree-of-freedom speed servo system under adaptive control are described. The system consists of a speed feedback loop with a fixed gain controller and an adaptive feedforward controller (AFC). The objective of the AFC is to improve the tracking performance, and the parameter is adjusted by an adaptation law so that the dynamic inverse of the plant is constructed in the feedforward path. The fixed gain feedback controller, which significantly restrain any disturbances, is designed by using two methods, one is based on the frequency responses between the disturbance and actual output and the other is on the disturbance observer theory. The responses of the speed servo systems designed by using both methods for a trapezoidal desired output and several types of disturbance are measured. Experimental results demonstrate that the effectiveness of the proposed systems for improvement of the tracking performances and robustness.

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In this paper, high speed synchronization of multiple motion control axes with nonlinearity under neuro servo control is considered. The system consists of multiple axes with constant gain controllers, a synchronizing controller and a neuro servo controller. To achieve high speed synchronization among the axes, the synchronizing controller, which responds to the tracking errors, is introduced. The tracking error in one axis is regarded as the synchronization errors between the relevant axes. The weights of the neuro servo controller are adjusted by the back propagation algorithm so that the tracking and the synchronization errors are minimized. It results in remarkable improvement in the tracking performance and the quick removal of the synchronization errors during the transient as well as at the steady state. The synchronization for four-axes, of which the parameters are significantly different, is investigated. Experimental results demonstrate the effectiveness of the proposed control scheme for synchronization.

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This paper describes a new steering control system for an autonomous road vehicle using the fuzzy neural network algorithm. Most of conventional fuzzy controls are represented by linguistic rules based on an expert's or engineer's control knowledge for a system. But the expert's knowledge is not so clear that it is difficult to represent the characteristics of the control system by these linguistic rules perfectly.
So, this paper proposes a fuzzy neural network control algorithm which includes both the advantages of the fuzzy logic and the neural network to overcome the disadvantages of them. The FCM (Fuzzy C-means Method) clustering algorithm is applied to create the optimal control rules with data measured in off-line control mode. These rules are learned by the error back propagation learning algorithm.
A computer simulator is developed to compare the performance of the proposed fuzzy neural network with those of the conventional fuzzy logic and the CMAC (Cerebellar Model Articulation Controller) neural network for steering control of the autonomous road vehicle. The proposed FNNC is found to be superior in all aspects by computer simulations.

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Slim Floppy Disk Drive, which could be mounted on a Hand-held personal computer, is now under intensive study in Japan. Spindle motor for Floppy Disc Drive has a index position detecting means, a index magnet attached to the outer wall of the periphery of the rotor yoke, and a magnetic sensor detecting the magnetic flux from the index magnet. As a result, spaces for providing the index magnet and the magnetic sensor prevent the motor from being made smaller in size and thinner in thickness.
This paper describes the method for detecting index position of a spindle motor without both the index magnet and the magnetic sensor. This method detects a index position per rotation from two different kinds of frequency generating signals (Main FG and Sub FG) through a index detecting circuit. The thin spindle motor applied this index detecting method performed a smaller degree of rotational speed variation compared with another wellknown one without both the index magnet and the magnetic sensor. This index detecting method is most suitable for less-inatia-thin spindle motor, and is easy to assemble.

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Superconducting magnetic energy storage (SMES) is considered the next generation technology for storing electrical energy because its energy storage efficiency is higher than that of any conventional energy storage system and its charging and discharging times are short.
This paper discusses a SMES input circuit suitable for DC lines and discusses the circuit control method used to achieve the SMES system. Test results showing the basic capability of the input circuit to transfer energy to an SC in a DC-SMES system are also given.

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2-mass system is an important first order approximated model of flexible joint robot, flexible arm, and its vibration suppression control is of a great importance for motion control. For this control problem, there have been many researches on vibration suppression control of 2-mass system in the face of parameter variations, but the effectiveness of their control methods has been only confirmed through simulations.
This paper is concerned with the experimental evaluations of the vibration suppression control of a 2-mass system. Three typical controllers, a PID controller, an H_∞ controller, and a μ controller, are designed and compared from the viewpoint of the control performance against the parameter variations. In the design procedure of H_∞ control and μ-synthesis method, we consider the parameter variations in the mass of the cart2 and the spring constant which correspond to the change of the natural frequency of the 2-mass system between 4.68 and 6.66 rad/sec. Based on these variations, eight kinds of the perturbed models are defined. Then we regard those models as uncertainties and apply μ-synthesis method to 2-mass system. From the experimental results, it is observed that PID control and H_∞ control may lead to poor performances in the presence of the parameter variations, but μ-synthesis yields better transient and steady state responses even if the parameter variations exist.

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Permanent magnet type synchronous machines have been widely used for industrial applications. It is commonly known that they are operated at high efficiency since no excitation input is required. However it is difficult to control the air gap magnetic flux, because the magnetic flux is determined by the property of the permanent magnet and approximately kept constant.
On the other hand synchronous machines with the field winding make it easy to control the air gap magnetic flux. But the copper loss of the field winding becomes large at the rated load.
In order to realize the magnetic flux control easily and improve the performance of the conventional synchronous machine, we propose a hybrid excitation type synchronous machine (HSY) with the permanent magnets and the field winding. Advantages of HSY are (1) it has no brushes (maintenance free), (2) required excitation input is small (high efficiency), (3) it is easy to get a sufficient magnetic flux control, and others. Therefore, HSY has a great possibility to use for various applications.
In this paper, basic principles and characteristics of HSY are mainly discussed and made clear.

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This paper is concerned with robust H^∞ control for an experimantal system of the pantograph with a Linear DC Motor. Recently higher train speeds have caused various problems such as power supply and aerodynamic noise. One of the approaches to solve these problems is to optimize the overhead wire-panotograph system. The low-noise pantograph is now being researched and developed, and needs active force control to stabilize the current. In this paper, we use a Linear DC Motor (LDM) as an actuator of the pantograph in order to control the contact force between the overhead wiring and the pantograph. An experimental machine has been designed and developed, and has an oscillatory characteristic. We designed the robust force controller for the system in order to improve step response and the frequency-domain performance.
At first, the experimental machine and the digital controller of the active pantograph system are introduced. Next, its linearized model is formulated in a state-space form. Then, H^∞ control system using differential game theory in the time domain is designed. Finally, the several experiments are carried out so as to evaluate the control performance of the designs, where the proposed control scheme is compared with the H^∞ mixed sensitivity control.

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