Position control device

A position control device, comprising:

• a position sensor mounted on a rotary shaft to detect a rotational position of the rotary shaft and produce a position feedback signal to control the position;
• and
• a program to find data on detection error caused by eccentricity or mounting error of an element to be detected by the position sensor mounted on said rotary shaft,
• wherein the program is executed when a revolving speed of the shaft becomes not less than a predetermined speed, so that the detection error data is automatically obtained based on an output signal from the position sensor and is then stored in a memory of the position control device, and a command rotational position is corrected based on the stored detection error data, providing a corrected command for rotational position of the motor.

A position control method, comprising:

• rotating a rotary shaft on which is fixed an element to be detected by a position sensor, at a predetermined revolving speed, monitoring a signal detecting portion of the element to be detected at predetermined sampling periods, and finding an amount of movement within a sampling period;
• finding a maximum value and a minimum value among the amounts of movement during one revolution of the element to be detected;
• finding a time period from a point of reception of one revolution signal from the detected element to a point of detection of the maximum value among the amounts of movement;
• determining an error with respect to a command angle based on the predetermined revolving speed, the sampling period and at least one of the maximum value, minimum value, and time period;
• and
• equally dividing the rotary shaft into n sections, n being an integer of not less than 1, to find an amount of correction for canceling the error, and adding the amount of correction to the movement command for the motor which drives the rotary shaft, every time the rotary shaft is advanced by an angle 2″/n.

A position control device to control a rotational position of a rotary shaft, comprising:

• a rotatable shaft with an element mounted thereon;
• a motor to drive said rotatable shaft;
• a position sensor positioned adjacent said element so as to detect detection error data of an eccentricity or mounting error of said element as mounted on said rotatable shaft;
• a calculator to calculate the detection error data based on an output signal of said position sensor and a detected rotational position of the rotatable shaft;
• a storage device to store said detection error data;
• and
• a correction device to provide a command rotational position for said motor driving said rotatable shaft corrected for said calculated detection error data.

A position control device to control a rotational position of a rotary shaft, comprising:

• a rotatable shaft with an element mounted thereon;
• a motor to drive said rotatable shaft;
• and
• a position sensor positioned adjacent said element so as to detect detection error data of an eccentricity or mounting error of said element as mounted on said rotatable shaft,
• wherein said position control device calculates the detection error data based on an output signal of said position sensor and a detected rotational position of the rotatable shaft, stores said detection error data, and provides a command rotational position signal for said motor driving said rotatable shaft that is corrected for said detected error data.

A method for controlling the position of a rotating shaft comprising:

• rotating a shaft with an element mounted thereon with a motor;
• detecting detection error data of an eccentricity or mounting error of the element mounted on the rotating shaft with a position sensor mounted adjacent to the detecting element by calculating the detection error data based on an output signal of the position sensor and a detected rotational position of the rotatable shaft, and storing the detection error data;
• and
• generating a command rotational position signal that has been corrected for the detection error data to drive the motor rotating shaft.