Positioning control device for an electric motor

A positioning control device for an electric motor comprising:

• position detection means for detecting a rotational position of said motor;
• setting means for setting a positioning target value;
• control means for supplying a stop command to said motor in accordance with the relationship between position data detected by said position detection means and said positioning target value;
• learning means, operative at each positioning operation of said motor, for detecting and storing an error of an actual stop position of said motor relative to the target value when stopping of said motor has been completed in response to said stop command;
• and
• correction means, operative at the next positioning operation to a like positioning target value, for correcting a timing for supplying said stop command in said control means in response to the error detected and stored at the previous positioning operation in that target value.

An apparatus for providing at a precise time a stop signal causing braking of a rotating shaft electric motor in order that, after a period of deacceleration, the shaft of the motor may stop rotation at a position closely proximate to a target stop position received by the apparatus, the apparatus comprising:

• means for detecting a current rotational position of the rotating shaft of the motor;
• storage means, receiving the target stop position, for supplying a correction to the target stop position;
• control means, receiving the target stop position and also receiving the correction to the target stop position from the storage means and also receiving the rotational position from the means for detecting, for supplying at a precise time a stop signal causing braking of the rotating shaft electric motor until, after a period of deacceleration, the shaft of the motor does stop;
• and
• learning means, receiving the target stop position and also receiving the rotational position of the shaft of the stopped motor from the means for detecting, for computing a revised correction in respect of both the target stop position and the rotational position and for storing the revised correction within the storage means as the correction to a subsequent same target stop position.

In a learning, adaptive, positioning control system for rotational positional control of an electric motor having

• position detection means for detecting a rotational position of the motor;
• directive means for supplying positioning target values;
• memory means for storing offset values respectively associated with the positioning target values;
• positioning control means, responsive to the positioning target value received from the directive means and to an associated corrective offset value received from the memory means, for stopping the motor at a rotational position proximate to each positioning target value;
• and
• adaptive learning means, responsive to the rotational position received from the position detection means and to each positioning target value, for providing after each stopping of the motor a correction to that offset value stored in the memory means which was contributory, by action of the positioning control means, to the rotational position assumed by the motor upon each stopping;
• an improvement comprising:
• the correction provided by the adaptive learning means to the offset value is of a magnitude within a limited range, the maximum magnitude correction within the limited range being less than a maximum offset value stored within the memory means.

A positioning control device for an electric motor comprising:

• position detection means for detecting a rotational position of said motor;
• velocity detection means for detecting the velocity of rotation of said motor;
• setting means for setting a positioning target value;
• overrun amount estimation means for determining an estimated amount of overrun by employing the detected velocity;
• compensation means for modifying at least one of the value of position data obtained by said position detection means and the positioning target value in accordance with the estimated amount of overrun determined by said estimation means;
• control means for supplying a stop command to said motor in accordance with the relationship between the position data and the target value after the modification by said compensation means;
• and
• learning means for detecting an error of an actual stop position of said motor relative to the target value when positioning for stopping said motor has been completed in response to said stop command and correcting a timing for supplying said stop command in said control means in response to the detected error.