Position control device

• US 5,939,851 A
• Filed: 12/23/1997
• Issued: 08/17/1999
• Est. Priority Date: 12/27/1996
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yamamoto, Shinji, Hayashi, Tadashi, Kataoka, Kenichi
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/997,484
• Time in Patent Office: 602 Days
• Field of Search: 318/611, 318/623, 318/624, 318/280, 318/281, 318/283, 318/445, 318/447, 318/452, 318/466, 318/470, 318/114, 318/120, 318/127, 310/316, 310/317
• US Class Current: 318/611
• CPC Class Codes: G05B 19/231 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: G05B 2219/41423 Noise filter as function of rate of displacement, speed, for stabilisation
• CPC Class Codes: G05B 2219/42229 Shut off control, system, power on detection of zero or neutral position

Abstract

A position control device for driving a movable member by a motor to a target position prevents a re-start of the motor by the vibration after stopping of the movable member. A re-start operation is forcedly inhibited during a predetermined period after a stopping operation of the movable member at the target position, and is permitted, only after the predetermined period, is entered by the position of the movable member is different from the target position.

Claims

1. A position control device for use with a motor, a movable member driven by the motor, and detection means for detecting a position of the movable member, said position control device effecting position control by starting and stopping a drive operation of the motor based on the result of a comparison of a target position and the position detected by the detection means, said position control device comprising:

a stopping circuit for stopping a drive operation of the motor when the positional relationship between the target position and the position detected by the detection means reaches a first positional relationship;

a starting circuit for starting a drive operation of the motor when the positional relationship between the target position and the position detected by the detection means reaches a second positional relationship different from said first positional relationship; and

an inhibition circuit for inhibiting said starting circuit from restarting a drive operation for a predetermined period after a drive operation of the motor is stopped by said stopping circuit, regardless of the result of the comparison, the predetermined period being an elapsed time measured from a moment at which the positional relationship between the target position and the position detected by the detection means reaches the first positional relationship.

2. A position control device according to claim 1, wherein said stopping circuit stops a drive operation of the motor when the difference between the target position and the position detected by the detection means reaches a first range.

3. A position control device according to claim 2, wherein said starting circuit restarts a drive operation of the motor if the difference between the target position and the position detected by the detection means is outside the first range after the predetermined period.

4. A position control device according to claim 2, wherein said starting circuit restarts a drive operation of the motor if the difference between the target position and the position detected by the detection means is outside a second range wider than the first range after the predetermined period.

5. A position control device according to claim 1, wherein the motor is a vibration type motor.

6. A position control device for use with a motor, a movable member driven by the motor, and detection means for detecting a position of the movable member, said position control device effecting position control by starting and stopping a drive operation of the motor based on the result of a comparison of a target position and the position detected by the detection means, said position control device comprising:

a stopping circuit for stopping a drive operation of the motor when a positional relationship between the target position and the position detected by the detection means reaches a first positional relationship;

a starting circuit for starting a drive operation of the motor when the positional relationship between the target position and the position detected by the detection means reaches a second positional relationship different from the first positional relationship; and

an inhibition circuit for inhibiting said starting circuit from restarting a drive operation of the motor after the stopping circuit stops a drive operation of the motor restarted by said starting circuit plural times.

7. A position control device according to claim 6, wherein the motor is a vibration type motor.

8. A position control device for use with a motor, a movable member connected to the motor, an encoder provided on the movable member, a comparator circuit which compares an output of the encoder with a set value and outputs (1) a stop signal when a relationship between the output of the encoder and the set value reaches a first relationship and (2) a start signal when the relationship between the output of the encoder and the set value reaches a second relationship different from the first relationship, and a motor drive circuit, which is connected to the comparator circuit and includes a switching element for providing power supply to the motor, and which causes the switching element (i) to start providing power supply in response to a start signal, and (ii) to stop providing power supply in response to a stop signal, said position control device comprising:

a timer circuit, connected to the comparator circuit, for starting a time measurement operation for measuring a predetermined elapsed time in response to a stop signal; and

an inhibition circuit, connected to said timer circuit and responsive to the output of said timer circuit, for inhibiting operation of said motor drive circuit in response to a start signal during a period in which the timer circuit measures the predetermined elapsed time.

9. A position control device according to claim 8, wherein the motor is a vibration type motor.