Tsutomu Kominami

A Novel Nine-Switch Inverter for Independent Control of Two Three-Phase Loads

Industrial applications require large numbers of motors. For example, motors are used to manipulate industrial robots, an electric vehicles with in-wheel motors and electric trains. Two methods exist for controlling PM motors providing an inverter to control each motor, and connecting the motors in parallel and driving them with a single inverter. The first method makes an experimental apparatus complex and expensive; the second does not allow independent control of each motor because of differences in rotor angle between the two motors. Thus, we propose a novel nine-switch inverter that can independently control two three-phase loads. This paper introduces the structure of the nine-switch inverter, which is made from nine switches. The validity of the proposed inverter is verified through simulations and experiments.

Development and Analysis of a High Thrust Force Direct-Drive Linear Actuator

This paper presents the design and analysis of a novel high thrust force linear actuator with high backdrivability. This motor consists of a mover and a stator with spiral (helical) structure. The mover moves spirally in the stator, and the linear motion is extracted to drive the load. This motor is a direct-drive system and highly backdrivable. In this paper, a basic model and thrust-force/torque equations are proposed, and finite-element method analysis and experimental results of a prototype are presented. From experiments, the designed spiral motor achieves 2000-N rated thrust force. The thrust-force capabilities of the spiral motor are compared with other linear motors. It is confirmed that the spiral motor is almost close to the latest state of the art in linear motor technology.

Inverter with Reduced Switching-Device Count for Independent AC Motor Control

This paper proposes a novel inverter named nine-switch inverter. The inverter has nine switching devices and can control two loads. First, the configuration of the inverter is introduced. Then, a PWM method for the inverter is elaborated. The validity of the inverter is verified by simulations and experiments. In addition, this paper proposes a 3N + 3-switch inverter, which is an extension of the nine-switch inverter. This inverter has 3N + 3 switches and can control N loads independently. The validity of the 3N + 3-switch inverter is also verified by simulations.

Magnetic levitation control and spiral-linear transformation system for spiral motor

Various industrial applications utilize linear actuators which are usually performed by rotational type motors combined with ball gear and by linear motors. Each of their methods has advantages and disadvantages. A spiral motor is expected to be superior to traditional linear actuator. The spiral motor is a tubular type linear actuator which has a spiral type mover and stator with magnetic levitation. It realizes friction free screw motion and few flux leakage. However, it needs a large winding current to activate the mover because the magnetic attraction force between the mover and the stator of the spiral motor is very large. Large current may break the windings of the spiral motor. Also two inverters are required when the spiral motor is driven because the two stator windings have to be independently controlled. However, the experimental apparatus and the cost increase if two inverters are used. Thus, a novel inverter which can independently control two windings is proposed. A novel transformation system from spiral motion to linear motion is introduced to realize effective motion. In this paper, a current value at activation and a novel inverter were verified by simulation. The development of simplified motor and the spiral-linear transformation system are reported

Development of a high thrust linear actuator with high backdrivability

This paper presents design and analysis of a novel high thrust linear actuator with high backdrivability. This motor consists of a mover and stator with spiral structure. The mover moves spirally in the stator and the linear motion is extracted to drive the load. This motor is a direct-drive system and highly backdrivable. In this paper, a basic model and thrust/torque equations are proposed, and the development of a prototype is presented. From the analysis, the designed spiral motor is expected to achieve higher thrust per unit volume than the conventional linear motors.

Dynamic model and control of six-phase spiral motor

Various industrial applications utilize linear actuators which are usually performed by rotational type motors in combination with ball screw, by hydraulic actuators, and by linear motors. The ball screw has small friction, which has bad influence on positioning accuracy. The hydraulic actuators have maintenance problem. Also the equipment of the linear motors becomes complicated it makes a lot of magnetic flux of leak. In this paper, we propose a new spiral type motor which overcome the conventional defects of these linear actuators. By using spirally shaped rotor and stator, it can transform the rotational motion to forth-and-back movement according to the screw mechanism. The friction free screw mechanism is realized by magnetic levitation of the rotor. The basic model of six-phase spiral motor is introduced. The model was analyzed by using a equivalent magnetic circuit. All interlinkage magnetic flux is given from a equivalent magnetic circuit. The thrust and torque equation is also given and the numerical examples are shown. When the spiral motor is driven, it is required to keep the displacement of gap x/sub g/ being zero in order to avoid touchdown. We applied a two-degree-of-freedom control to the gap control. The simulation results of the gap control are shown.

Development of a Spirally-Shaped Linear Actuator

This paper reports development of a novel high thrust linear machine with spiral structure. This motor consists of a mover and stator with spirally-shaped iron cores. The mover moves spirally in the stator and the linear motion is extracted to drive the load. In this paper, a basic model and thrust/torque equations are provided based on permeance analysis, and experimental results of a prototype are presented. From the analysis, thrust of the designed spiral motor of 43 [kg] weight is expected to achieve 3000 [N], which is higher than the conventional linear motors thrust.