A digital input to a digital-to-analog converter is divided into a most significant portion and a lesser significant portion. A replicated-data system maintains a version number, a membership group identifier, and a membership count, with each replica of a data item. Formed in the electric motor are a first coil 7A1 which is wound between given slots 11, and a second coil 7A2 which is wound in a direction opposite to a direction of the first coil 7A1 between slots 11 existing at positions point-symmetric to the given slots 11 with respect to a center of a rotation shaft. At this time, the stagewise expansion forms include undetermined scalar coefficients and undetermined basis functions.