Abstract: The stepping motor driver comprises current sensors that detect winding current values, an angle detection means that detects a rotational angle of a rotor, a first coordinate transformation means that transforms winding current values into winding current values in a rotational coordinate system, an angle calculation means that calculates a command angle value, a third coordinate transformation means that transforms command current values into command current values in the rotational coordinate system according to the difference between the command angle value and the rotor angle value, a current control means that generates current control signals in the rotational coordinate system based on the differences between the command current values in the rotational coordinate system and the winding current values in the rotational coordinate system, a second coordinate transformation means that transforms the current control signals in the rotational coordinate system into current control signals in a fixed coord

Abstract: The controller comprises current sensors for detecting motor currents, an inverter containing a current control means for feeding currents to motor windings, a coordinate transformer that transforms the motor currents in a fixed coordinates system into currents in a first rotational coordinates system, and an angle calculator that transforms a command pulse into a command angle. A second rotational coordinates system composed of a dp axis and a qp axis perpendicular to the dp axis is determined from the command angle. A command current on the dp axis is set to be a value corresponding to a motor current amplitude and another command current on the qp axis is set to be zero. The motor current is projected on the dp and qp axes and controlled so as to make the components on the dp and qp axes coincide with the respective command currents on the dp and qp axes.

Abstract: A large-diameter welded steel pipe having a straight seam and tab plates attached to its ends as extensions of the seam is laid along a setting line with the seam upward. An apparatus for treating the ends of such a pipe has a tab plate cutting unit and a bead removing unit. The tab plate cutting unit cuts the tab plates off with a torch. The bead removing unit removes the weld beads on the inner surface of the ends of the pipe by cutting them with a rotary cutter.