Development of High‐Acceleration Linear Motor to Realize Resource Saving and High Productivity

The use of linear motors has been rapidly increasing in recent years in response to the rising demand for drive mechanisms with higher speed and acceleration to improve the throughput of semiconductor production equipment, machine tools, and so on. In this study, we have developed a new type of linear motor with an opposed magnetic pole structure and twin movers. To achieve higher acceleration of a linear motor, it is necessary to satisfy both large thrust and low inertia. In our proposed new type linear motor, the thrust is improved by increasing the facing area between the permanent magnets and magnetic pole teeth by using multistage movers. Furthermore, the magnetic leakage flux is reduced by multiplexing the magnetic flux path. In a short stroke (approximately 210 mm) drive, the high acceleration of 1670 m/s² and maximum velocity of 14.2 m/s is demonstrated using a prototype linear motor (maximum thrust = 25 kN).     

Extension of Mathematical Models Taking Temperature Variation in Permanent Magnet Synchronous Motors into Consideration

We have developed novel mathematical models of d‐axis and q‐axis magnetic fluxes ?_d and ?_q for permanent magnet synchronous motors (PMSMs). The models can be used to approximate magnetic characteristics using simple fractional equations with i_d and i_q as variables. They include eight constants, and some of them represent the degree of magnetic saturation and cross‐coupling. However, the magnetic characteristics are varied with the temperature rise in PMSMs, which are dependent on the load torque and motor speed. In this paper, the characteristics of the eight constants that vary with the motor temperature and the residual flux density B_r are shown. Further, we propose to extend the mathematical models by considering the temperature and B_r variation.