Motor speed control device
AssigneeNikon Corporation
InventorsJunichi Omi, Hidenori Miyamoto, Tatsuo Amanuma, Toshiyuki Nakamura
Life of this patent
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Abstract
A motor speed control device, preferably for use in a camera, controls a motor to rotate at a constant speed in accordance with a pulsed signal output from a motor speed detector, such as a photointerrupter. To overcome the control problems that occur when the motor abnormally stops rotating, preventing generation of pulsed, the motor speed control device includes a timer that measures elapsed time from a most recent pulse. When the elapsed time exceeds a predetermined value, the motor speed control device accelerates the motor so that control of the motor at a constant speed can continue.
Claims20
A motor speed control device, comprising:
- a motor speed detector coupled with a motor to detect motor speed and generate a pulsed signal having pulse intervals that vary in accordance with motor speed;
- and
- a controller coupled with the motor speed detector to receive the pulsed signal from the motor speed detector, the controller comprising:
- a timing mechanism for measuring pulse intervals of the pulsed signal;
- a comparator coupled with the timing mechanism to compare pulse intervals of the pulsed signal to a target value corresponding to a target motor speed, and to compare time elapsed since a most recent pulse to a maximum value corresponding to an abnormally low motor speed;
- and
- a command generator coupled with the comparator to generate a drive command in accordance with the pulse-intervals-to-target-value comparison to drive the motor at the target speed, the command generator further generating an accelerate command in accordance with the elapsed-time-to-maximum-value comparison to accelerate the motor when the elapsed time is greater than or equal to the maximum value.
A motor speed control device, comprising:
- motor speed detecting means for detecting speed of a motor, the motor speed detecting means generating a pulsed signal having pulse intervals that vary in accordance with motor speed;
- timing means for timing a duration of said pulse intervals;
- comparing means for comparing said duration of said pulse intervals of the pulsed signal to a target value corresponding to a target motor speed, and for comparing time elapsed since a most recent pulse to a maximum value corresponding to an abnormally low motor speed;
- and
- command generating means for generating a drive command in accordance with the pulse-intervals-to-target-value comparison to drive the motor at the target speed and for generating an accelerate command in accordance with the elapsed-time-to-maximum-value comparison to accelerate the motor when the elapsed time is greater than or equal to the maximum value.
A method of operating a motor, comprising:
- detecting a pulsed signal having pulse intervals that vary in accordance with the speed of a motor;
- comparing, when a pulse is detected during the detecting step, pulse intervals of the pulsed signal to a target value corresponding to a target motor speed;
- generating a drive command in accordance with the pulse-intervals-to-target-value comparing step to drive the motor at the target speed;
- comparing, when a pulse is not detected during the detecting step, time elapsed since a most recent pulse to a maximum value corresponding to an abnormally low motor speed;
- and
- generating an accelerate command in accordance with the elapsed-time-to-maximum-value comparing step to accelerate the motor when the elapsed time is greater than or equal to the maximum value.
A motor speed control device, comprising:
- a motor speed detector coupled with a motor to detect motor speed and generate a pulsed signal having pulse intervals that vary in accordance with motor speed;
- and
- a controller coupled with the motor speed detector to receive the pulsed signal from the motor speed detector, the controller comprising:
- a timing mechanism for measuring pulse intervals of the pulsed signal;
- a comparator coupled with the timing mechanism to compare pulse intervals of the pulsed signal to a target value corresponding to a target motor speed;
- and
- a command generator coupled with the comparator to generate a drive command in accordance with the pulse-intervals-to-target-value comparison to drive the motor at the target speed, the command generator generating a decelerate command to decelerate the motor when the pulse intervals are less than or equal to the target value.
Dependencies are inferred from the claim text.