Yasukazu Sato

Development of a 2-Degree-of-Freedom Rotational/Linear Switched Reluctance Motor

This paper presents a novel electromagnetic actuator having 2 degrees of freedom for rotational and linear actuation. It is based on a switched reluctance motor. Torque and thrust can be controlled independently. The prototype actuator is designed to perform 2-degree-of-freedom actuation with maximum rotational speed of 1000 min -1 and maximum thrust force of 30 N. In the motor performance testing, it has been confirmed that independently control of rotational speed and linear position is realized

Power-Saving Magnetization for Magnetorheological Fluid Control Using a Combination of Permanent Magnet and Electromagnet

This study proposes a mechanism for controlling the viscosity of a magnetorheological fluid (MRF) to save a significant amount of electric power consumed during the magnetization process. The mechanism takes advantage of the magnetization/demagnetization property of permanent magnet materials. It consumes no electric power while maintaining the applied external magnetic field to the MRF. The device can also continuously control the intensity of the magnetic field using very little electric power. The evaluations of the power-saving and the viscosity control performances are reported. It is confirmed that the magnetizing device is very effective in maintaining the magnetic field to the MRF, while saving a significant amount of electric power. The device is especially useful in applications where long duration magnetization necessary.

Power-Saving Drive in 2-Position Control of Giant-Magnetostrictive Actuator

In the fundamental configuration of a giant magnetostrictive linear actuator (GMA), a giant magnetostrictive material (GMM) rod is energized by a coil surrounding it. However, supply of continuous electric power to the coil is necessary to maintain the expansion of the GMA. The electric power consumption is in proportion to the activation interval and becomes larger especially for applications which maintain the expansion of the GMA for long duration. This research developed a new GMA drive method which wasted no electric power during the GMA expanding. Permanent magnet (Al-Ni-Co) rods are located around the GMM rod, which are magnetized and demagnetized by the coil instantaneously. The permanent magnets supply the magnetic field to the GMM rod without electric power consumption in maintaining the expansion of the GMA. It is possible to achieve both the power-saving drive of the GMA and reduction of the thermal expansion.

A computational effective material data representation for fast simulation models of giant magnetostrictive materials

Aiming at a reduction in time and high efficiency in computation, a set of simple formulas characterizing a giant magnetostrictive material is proposed. It can represent nonlinearity of the magnetic properties with respect to both the magnetic field intensity and the mechanical stress, using easy-to-handle formulas with some adjustable parameters read from measured data resources.

Power-Saving Magnetizing Device for Magnetorheological Fluid Control Using Permanent Magnet

This paper presents a power-saving magnetizing device for magnetorheological fluids (MRFs). This device encompasses a permanent magnet for magnetizing the MRF, instead of an electromagnet that consumes electric power. The permanent magnet applies a magnetic field to the MRF through a specially designed magnetic yoke, and the field intensity can be controlled by moving the magnet. When the magnetic field is controlled by a permanent magnet, the thrust attracting the magnet into the yoke normally acts on the magnet, and consumes power holding and moving the magnet. This paper proposes and evaluates a magnetic circuit design to reduce the thrust, improve magnetic field control, and accomplish a power-saving magnetizing device for MRFs.

Sensorless Torque and Thrust Estimation of a Rotational/Linear Two Degrees-of-Freedom Switched Reluctance Motor

A rotational/linear two degrees-of-freedom switched reluctance motor (2DOF-SRM) has been developed for the purpose of independent control of rotational and linear actuations on one actuator. In the previous study, noncontact-type angular and linear position sensing system that used photoelectric sensors was developed. It was successfully applied to the independent rotational speed and linear displacement control of the 2DOF-SRM. In this paper, both the torque and thrust control are developed as the new function of the 2DOF-SRM. This control is achieved by the electric current control for each phase windings. In this system, actual torque and thrust are independently estimated by a simplified matrix expression from the information of the phase winding current. The performance test results for torque and thrust estimation are presented.

Digital/Analog Hybrid Magnetization of Magnetorheological Fluids for Expansion of Their Controllable Viscosity Range

This paper proposes a mechanism for controlling the viscosity of magnetorheological (MR) fluids from the viewpoint of expanding their controllable viscosity range. An MR fluid changes its viscosity according to the intensity of the applied external magnetic field. Electromagnets are generally used as the source of the applied external magnetic field. For applying the magnetic field effectively to an MR fluid, typical magnetic poles are made to form a pair of plates facing each other. To increase the intensity of the magnetic field, the distance between the magnetic poles must be small. However, from the viewpoint of expanding the controllable viscosity range, the distance must be large in order to reduce the fluid viscosity resistance of the nonmagnetized MR fluid. This study develops a new magnetizing device that can cope with these two conflicting requirements. This device uses a combination of the digital/analog magnetizing method and a modified pulse code modulation. The evaluation of the control performance of the MR fluids viscosity by the proposed device is reported, which confirms that this magnetizing device can continuously control the MR fluids viscosity and is very effective in expanding its controllable range.