Abstract
A high-speed hydraulic servo valve using a moving-coil-type linear dc motor (LDM) was developed. A moving-magnet-type LDM has been studied as means of reducing the mass of magnets, which is desirable for economic reasons. This paper describes the static thrust characteristics of the moving-magnet-type LDM, and compares the LDM with the moving-coil type LDM for hydraulic servo valve. The following conclusions are reached: (1) the calculation errors obtained for the static thrust of the moving-magnet-type LDM by using the permeance analysis method and the finite element method are 7% and 2%, respectively, and (2) the masses of the permanent magnets used for the moving-magnet-type LDM are 43% less than those used for the moving-coil-type LDM. However, the electric time constant and the mechanical time constant of the moving-magnet-type LDM are larger than those of the moving-coil-type LDM.
