Linear DC motor driving device

A driving device for a multipolar type linear DC motor using a PWM driving signal, for driving a linear DC motor by causing an excitation coil of said motor, placed in alternating fields, to generate an induction field, and by switching polarities of the induction field, said driving device comprising:

• magnetic field strength detecting means for detecting a strength of a magnetic field acting on said excitation coil in the alternating fields;
• magnetic field discriminating means, including a hysteresis circuit, for discriminating the magnetic field acting on said excitation coil on the basis of a potential of an output signal from said magnetic field strength detecting means by using hysteresis characteristics of said hysteresis circuit;
• and
• polarity switching control means for controlling a direction and generation time of an induction field generated by said excitation coil in accordance with an output signal from said magnetic field discriminating means.

A device comprising:

• a linear DC motor, having an excitation coil, and a Hall element arranged in said coil, for moving a movable stage;
• a linear encoder for detecting a speed of movement of said movable stage;
• speed control means, connected to an output terminal of said Hall element, for driving said motor by switching polarities of a magnetic field in said motor;
• position control means, connected to an output terminal of said linear encoder, for controlling a position of said movable stage;
• driving control means, connected to output terminals of said speed control means and said position control means, for driving said motor while performing position and speed control of said movable stage on the basis of outputs from said speed control means and position control means;
• and
• means for preventing generation of a peak current when a direction of a supply current to said excitation coil of said motor is switched.

A driving device for a multipolar type linear DC motor using a PWM driving signal, for driving a linear DC motor by causing an excitation coil of said motor, placed in alternating fields, to generate an induction field, and by switching polarities of the induction field, said driving device comprising:

• magnetic polarity detecting means for detecting a direction of a magnetic field acting on said excitation coil in the alternating fields;
• an electrical filter for removing an output signal output from said magnetic polarity detecting means and having the same period as a PWM drive period;
• polarity switching control means for controlling a direction and generation time of an induction field generated by said excitation coil in accordance with an output signal from said magnetic polarity detecting means;
• a PWM wave generator for generating a PWM wave in accordance with the PWM driving signal;
• a power MOS field-effect transistor for switching driving and stopping states of said linear DC motor in accordance with a gate drive pulse input to a gate thereof;
• a gate resistor, coupled between said PWM wave generator and said gate, for converting the PWM wave into the gate drive pulse;
• and
• means for compensating the PWM driving signal to compensate a difference between an effective time of the PWM wave and an effective time of the gate drive pulse.

A device comprising:

• a linear DC motor, having an excitation coil, and a Hall element arranged in said coil, for moving a movable stage;
• a linear encoder for detecting a speed of movement of said movable stage;
• speed control means, connected to an output terminal of said Hall element, for driving said motor by switching polarities of a magnetic field in said motor;
• position control means, connected to an output terminal of said linear encoder, for controlling a position of said movable stage;
• driving control means, connected to output terminals of said speed control means and said position control means, for driving said motor while performing position and speed control of said movable stage on the basis of outputs from said speed control means and position control means;
• means for preventing generation of a peak current when a direction of a supply current to said excitation coil is switched;
• change-over switch means for turning on and off said motor;
• and
• means for manually moving said movable stage when said motor is turned off by said change-over switch means.