Iwanori Murakami

Wireless Piping Inspection Vehicle Using Magnetic Adsorption Force

A robot is developed which is able to climb on a perpendicular branched piping and moves on the ceiling in the piping with the radio control. This inspection robot adsorbs to the piping using the magnetic adsorption force of a magnetic crawler and moves in piping. Therefore, the crawler should be composed of magnets that have optimal adsorption force. In order to design the crawler, the magnetic adsorption force is analyzed, and the design method of the inspection robot in the piping is shown. The robot mounts a radio control unit and a compact radio camera so as to inspect inside of piping. To validate it, a compact crawler type radio control robot is made, and traveling performance or inspection performance in the piping is examined.

The parametrization of all disturbance observers for plants with input disturbance

The disturbance observers have been used to estimate the disturbance in the plant. Several papers on design methods of disturbance observers have been published. Recently, the parametrization of all disturbance observers for plants with any output disturbance was clarified. However, no paper examines the parametrization of all disturbance observers for plants with any input disturbance. In this paper, we clarify existance conditions of a disturbance observer and a linear functional disturbance observers for plants with any input disturbance. Under these conditions, we propose the parametrizations of all disturbance observers and all linear functional disturbance observers for plants with any input disturbance.

Pulse motor with high-temperature superconducting levitation

A simple but stable noncontact high T/sub c/ superconducting levitation system with a vertical shaft has been presented. The system consists of a superconductor and permanent magnets. In the system, only a high T/sub c/ superconductor supports the lower end of the shaft, and the other end is supported by two ordinary permanent magnets. Since the restoring force is small with respect to the radial direction, the system becomes unstable when the force acts in the radial direction, so it is difficult to drive the shaft by electromagnetic forces when using motors. A driving system using electromagnets has been presented, in which the balanced forces act on two opposite sides of the disc-type rotor in the axial direction. Since the system has no unbalanced force from an analytical point of view, the rotor will be able to rotate without control. In the system, however, since there is eccentricity between the center of rotation and the magnetic center, vibrations are generated. This study also presents an optimal control method for the vibrations. To validate the proposed system and the control method experimental tests have been carried out.

Relationship between number of teeth and positioning accuracy on cylindrical magnetic gear

A magnetic gear can transmit a torque and a motion without the contact by the magnetic force. Today a magnetic gear are studied about increasing transmit torque and decreasing cogging torque. The property of the positioning is another significant property in use of a motion transmission by magnetic gears. Therefore it is important to measure the positioning property. The purpose of this research is to check the relationship between the number of the magnet of the gear and positioning property. Then we have developed three types of gear which have a different number of teeth severally. By using the developed three types of gear, the average and the standard deviation are calculated from experimental results. We reveal the influence of the number of the teeth to positioning property in several operation conditions.

A design method for two-degree-of-freedom multi-period repetitive controllers for multiple-input/multiple-output systems

Abstract Multi-period repetitive controller was proposed by Gotou et al., in order to improve the disturbance attenuation characteristic of modified repetitive control systems and that follows the periodic reference input with small steady state error. Recently, the parameterization of all stabilizing multi-period repetitive controllers was studied. However, when the parameterization of all stabilizing multi-period repetitive controllers is used, the input-output characteristic and the feedback characteristic cannot be specified separately. From the practical point of view, it is desirable to specify the input-output characteristic and the feedback characteristic separately. In addition, the parameterization is useful to design stabilizing controllers. Yamada et al. solved this problem by obtaining the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers. However, the method by Yamada et al. cannot be applied to multiple-input/multiple-output plants. Because, the method by Yamada et al. uses the characteristic of single-input/single-output system. In this paper, we propose the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers for multiple-input/multiple-output systems.

A Design Method for Stabilizing Modified Smith Predictors for Multiple-Input/Multiple-Output Time-Delay Plants

The modified Smith predictor is well known as an effective time-delay compensator for a plant with large time-delays, and several papers on the modified Smith predictor have been published. The parameterization of all stabilizing modified Smith predictors for single-input/single-output time-delay plants is obtained by Yamada et al. However, they do not examine the parameterization of all stabilizing modified Smith predictors for multiple-input/multiple-output time-delay plants. The purpose of this paper is to expand the result by Yamada et al. and to propose the parameterization of all stabilizing modified Smith predictors for multiple-input/multiple-output time-delay plants. Control characteristics of the control system using obtained parameterization of all stabilizing modified Smith predictors are also given. Finally, a numerical example is illustrated to show the effectiveness of proposed parameterization of all stabilizing modified Smith predictors.

Control of tension device for coil winding

To improve efficiency of a coil winding machine, the speed of winding the wire is increased. Then the some problems occur with increasing the wire winding speed. For example, the wire is broken or stretched too much. This paper has a discussion a control of the wire tension to avoid these situations. At first, we set a tension device at the initial position. If the tension arm moves from the original position, we control an angle of the arm to keep an original position by moving the drive motor. As a result, the angle of arm and the tension of wire are kept at specified value with small error. By the simulation, we confirm effectiveness of the proposed controller.

A Design Method for Two-Degree-of-Freedom Multi-Period Repetitive Control Systems

Multi-period repetitive controllers improve the disturbance attenuation characteristic of the modified repetitive control system that follows the periodic reference input with a small steady state error. Recently, the parameterization of all stabilizing multi-period repetitive controllers was studied. However, when the parameterization of all stabilizing multi-period repetitive controllers is used, the input-output characteristic and the feedback characteristic cannot be specified separately. From the practical point of view, it is desirable to specify the input-output characteristic and the feedback characteristic separately. In addition, the parameterization is useful to design stabilizing controllers. Therefore, the problem of obtaining the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers that can specify the input-output characteristic and the disturbance attenuation characteristic separately is important to solve. In this paper, we propose the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers.

Analysis and Experiment of Cylindrical Magnetic Gear

The magnetic gears can transmit torque without contact by applying magnetic force. So in comparison to normal mechanical gears, it may offer a lot of advantages such as low noise, low vibration, wear less, dustless and no lubricant oil at all. Besides, when a very large of input torque entered, magnetic force that pull each other exceeds it limit and the gear spin empty, resulting these magnetic gears limited the torque transmission and can function as torque limiter. However, as disadvantage, it is lack in transmitting torque. In the previous research, we designed cylindrical magnetic gear prototype to increase torque transmission and measured slip torque only. As a torque transmitter, the measurement of driving torque itself is more important. Therefore, the purpose of this research is to measure and study the driving torque due to implication of revolution speed, distance between the magnetic gears and rotational load.

Development of magnetic levitation synchronous motor with high-Tc superconducting bearing

In this study, we propose a new magnetic levitation synchronous motor with a high-Tc superconducting bearing. The levitation rotor obtains the levitation force by the magnetic attraction and the restoring force (axially and radially to the shaft) from a superconducting bearing. The levitation rotor to which the magnetic flux concentration method is applied has a large magnetic field outside of the rotor. Because the superconducting bearing constrains this concentrated magnetic flux, the rotor obtains a large restoring force. In addition, a superconducting bearing with a small bulk can be realized. We stabilized the rotor using this method and confirmed that this motor passed the resonance and that its speed increased to approximately 3500 [rpm] without control.