Stepping motor control apparatus

A stepping motor control apparatus comprising:

• a current detection means for detecting phase currents flowing into a stepping motor;
• an equivalent model-of-motor arithmetic means that includes a coefficient multiplication means which performs multiplication using a coefficient ka′=Ts/τ as a multiplier, a coefficient multiplication means which performs multiplication using a coefficient kb′=τ/(Ts+τ) as a multiplier, and a coefficient multiplication means which performs multiplication using a coefficient kg′=I0/E0 as a multiplier, where an initially applied voltage is E0, an initial current flowing responsively to application of the initially applied voltage E0 is I0, a resistance of a winding is R=E0/I0, a sampling cycle is Ts, an inductance is L, and a time constant of the winding is τ=L/R, and that calculates an estimated angle of excitation;
• a current control means for controlling an exciting current on the basis of the estimated angle of excitation, an angle command, and the phase currents detected by the current detection means;
• and
• a variable voltage inverter that applies phase voltages to phase windings included in the stepping motor according to outputs of the current control means.