Control system for transducer positioning motor

A control system in combination with a stepper motor having at least one phase winding for controlling the movement of said stepper motor, comprising:

• a current sensor coupled to said phase winding for producing a current feedback signal indicative of the current in said phase winding of said stepper motor;
• a voltage sensor coupled to said phase winding for producing a voltage feedback signal indicative of the voltage across said phase winding of said stepper motor;
• a mode switch receiving said current feedback signal and said voltage feedback signal as inputs, said mode switch selecting between said current feedback signal and said voltage feedback signal;
• and
• a pulse width modulation control circuit operatively coupled to said phase winding and receiving as an input the selected one of said current feedback signal and said voltage feedback signal;
• whereby said stepper motor may be operated in either current control mode utilizing said current sensor and said current feedback signal or in voltage control mode utilizing said voltage sensor and said voltage feedback signal.

A control system in combination with a stepper motor having a plurality of phase windings for controlling the movement of said stepper motor, comprising:

• a current sensor for each of said plurality of phase windings coupled to each respective one of said plurality of phase windings for producing current feedback signals for each respective phase winding indicative of the current in each respective one of said phase windings of said stepper motor;
• a voltage sensor for each of said plurality of phase windings coupled across each respective one of said plurality of phase windings for producing voltage feedback signals for each respective phase winding indicative of the voltage across each respective one of said phase windings of said stepper motor;
• a mode switch receiving said current feedback signals and said voltage feedback signals as inputs and for selecting between respective said current feedback signals and said voltage feedback signals, the selected signals being respective feedback signals;
• and
• a pulse width modulation control circuit for each of said plurality of phase windings operatively coupled to each respective phase winding and coupled to receive said feedback signals as an input signal;
• whereby said stepper motor may be operated in either current control mode utilizing said current sensors or in voltage control mode utilizing said voltage sensors.

A control system in combination with controlling a stepper motor of the type capable of moving from a first position to a second position and of the type which generates a motionally induced emf and an inductively induced emf while moving from said first position to said second position, comprising:

• a current control means having a high output impedance for controlling said stepper motor by supplying to said motor a programmable current relatively independent of said motionally induced emf and said inductively induced emf;
• a voltage control means having a low output impedance for controlling said stepper motor by supplying a programmable voltage relatively independent of the instantaneous current in said stepper motor, and
• a switching means for selecting said current control means when said stepper motor is making coarse adjustments in position relative to said second position and for selecting said voltage control means when said stepper motor is making fine adjustments in position relative to said second position.
• whereby said motionally induced emf of said stepper motor may be dissipated into the low output impedance of said voltage control means and the internal impedance of said stepper motor when it is making fine adjustments in position.