Step motor control

A control system for controlling a stepping motor of the type including a rotor and a plurality of electromagnetic field winding adapted to be separately energized to control rotation of said rotor, comprising:

• means for generating a signal representative of the back electromotive force induced by said rotor in an energized one of said field windings by subtracting a detected waveform representing the current induced in said field winding from a simulation waveform representing the current induced in said field winding due to its self inductance;
• means for providing a reference voltage corresponding to a desired angle of lead in driving said rotor of said motor;
• means for comparing said signal representative of the back electromotive force with said reference voltage;
• control means operable in response to detection of coincidence between said signal representative of the back electromotive force and said reference voltage for developing an instruction to start selective energization and deenergization of said field windings for a subsequent stepping motion of said motor;
• and
• means for driving said motor in response to the instruction from said control means.

A process of controlling a stepping motion of a stepping motor of the type including a rotor and a plurality of electromagnetic field windings adapted to be separately energized to control rotation of said rotor, comprising:

• generating a signal representative of the back electromotive force induced by said rotor in an energized one of said field windings by subtracting a detected waveform representing the current induced in said field winding from a simulation waveform representing the current induced in said field winding due to its self inductance;
• generating a reference voltage corresponding to a desired angle of lead in driving said rotor of said motor;
• comparing said signal representative of the back electromotive force with said reference voltage;
• and
• starting selective energization and deenergization of said field windings for a subsequent stepping motion of said motor when coincidence between said signal representative of the back electromotive force and said reference voltage is detected.

A control system for controlling a stepping motor of the type including a rotor having a permanent magnet and a plurality of electromagnetic field windings adapted to be separately energized to control rotation of said rotor, comprising:

• means for continuously detecting an electric current flowing through a last energized one of said field windings and for developing a voltage signal representing the electric current;
• simulation means for simulating a signal induced in said last energized field winding due to self inductance of said last energized field winding;
• means for successively comparing said signal induced in said last energized field winding with said voltage signal to produce a position signal induced in said last energized field winding by said permanent magnet pole of said rotor and indicating a current position of said rotor relative to said last energized field winding;
• means for providing a reference voltage corresponding to a desired angle of lead in driving said rotor of said motor;
• means for detecting coincidence of said position signal and said reference voltage;
• and
• control means operable in response to detection of coincidence between said position signal and said reference voltage for controlling selective energization and deenergization of said field windings of said motor.