Stepping motor control device

A stepping motor control device, comprising:

• a stepping motor including a rotor having magnetic poles equally spaced in a circumferential direction at intervals of an angle of θ°, and M-phase excitation coils (M is an integer greater than or equal to two, and the M-phase does not include a reverse phase);
• driving means for supplying a driving current having a plurality of levels to the excitation coils in accordance with command values;
• command value generating means for generating the command value where the driving current takes a different value having at least K levels (K is an integer);
• rotational angle detecting means for generating n pulses (n is an integer satisfying n≧M·K) corresponding to rotation of the rotor;
• excitation switching timing generating means for selecting pulses from the n pulses of the rotational angle detecting means in a predetermined order, and generating an excitation switching timing in the K levels to each M-phase excitation-coil;
• control means for switching between first, second, and third operation modes,
• wherein in the first operation mode, microstep driving is performed by the driving means, and the rotor is held at a predetermined angular position when the stepping motor is at rest,
• in the second operation mode, when the stepping motor is rotated by a predetermined amount or more, the command value generating means is caused to generate a command value in accordance with a timing generated by the control means itself, and thereafter, the second operation mode is switched to the third operation mode,
• in the third operation mode, the stepping motor is controlled by changing the command value in accordance with an output of the excitation switching timing means, and
• wherein in the second operation mode, the command value generating means generates a first command value for supplying a positive first driving current to the excitation coils, a second command value for supplying a negative second driving current whose direction is reverse to that of the first driving current to the excitation coils, and a third command value for supplying a third driving current taking a value between the first and second driving currents to the excitation coils, and generates different command values to the command value generating means in accordance with an angular position of the rotor by the control means.

A stepping motor control device for controlling a speed of a subject to be controlled by a driving current to the stepping motor, comprising:

• displacement detecting means for generating a detection pulse signal in accordance with a predetermined amount of displacement of the subject to be controlled;
• timer means for measuring a time interval from the last detection pulse signal to the present time;
• control means for changing the driving current when an output of the timer means exceeds a predetermined reference value;
• and
• reference value updating means for updating the reference value in accordance with an output of the displacement detecting means.

A stepping motor control device, comprising:

• a stepping motor including a rotor and a plurality of excitation coils;
• displacement detecting means for generating a detection pulse signal corresponding to a rotational displacement of the rotor;
• driving means for supplying a driving current to each excitation coil in accordance with an input command value;
• control means for controlling the stepping motor by changing the command value supplied to the driving means in accordance with a timing corresponding to the detection pulse signal of the displacement detecting means;
• and
• timer means for measuring a time interval from the last detection pulse signal to the present time,
• wherein the control means changes a ratio of a driving current supplied to each excitation coil by changing the command value when an output of the timer means exceeds a reference value.

A stepping motor control device for controlling a speed of a subject to be controlled by a driving current to the stepping motor, comprising:

• displacement detecting means for generating a detection signal corresponding to a predetermined amount of displacement of the subject to be controlled;
• timer means for measuring a time interval from the last detection signal to the present time;
• and
• control means for changing the driving current when an output of the timer means exceeds a predetermined reference value,
• wherein a change in the driving current is increased in accordance with an output of the timer means.

A stepping motor control device, comprising:

• a stepping motor including a rotor and at least one excitation coil;
• driving means for supplying a driving current to the excitation coils in accordance with an input command value;
• control means for controlling the stepping motor by changing the command value supplied to the driving means;
• displacement detecting means for generating a detection signal corresponding to a rotational displacement of the rotor;
• and
• timer means for measuring a time interval from the last detection signal to the present time,
• wherein the control means switches between a first operation mode and a second operation mode, changes the command value supplied to the driving means in accordance with a timing generated by the control means itself in the first operation mode, and changes the command value supplied to the driving means in accordance with a timing corresponding to the detection signal of the displacement detecting means in the second operation mode, to control the stepping motor, and
• wherein the control means switches the operation mode from the second operation mode to the first operation mode when an output of the timer means exceeds a predetermined reference value.

A stepping motor control device, comprising:

• a stepping motor including an armature and an excitation coil;
• control means for controlling an amplitude and an excitation phase of a driving current supplied to the excitation coils;
• and
• a position detecting means for generating a detection signal corresponding to a position of the armature,
• wherein the control means provides a first operation mode and a second operation mode, the first and second operation modes being capable of being switched,
• in the first operation mode, an excitation phase of the driving current is controlled in accordance with a timing corresponding to the detection signal of the position detecting means,
• in the second operation mode, an excitation phase of the driving current is controlled in accordance with a timing generated by the control means itself, and
• when an operation mode of the control means is switched from the first operation mode to the second operation mode, a maximum amplitude of the driving current in the second operation mode is designed in accordance with an amplitude of the driving current in the first operation mode.