Vibration type actuator drive controller and method of controlling drive speed of vibration type actuator

• US 20050046363A1
• Filed: 08/27/2004
• Published: 03/03/2005
• Est. Priority Date: 09/01/2003
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Yamamoto, Shinji
• Granted Patent: US 6,987,345 B2
• Time in Patent Office: Days
• US Class Current: 318/114
• CPC Class Codes: H02N 2/142 Small signal circuits; Means for controlling position or derived quantities, e.g. speed, torque, starting, stopping, reversing
• CPC Class Codes: H02P 25/032 Reciprocating, oscillating or vibrating motors

Abstract

This disclosure relates to a technique for smoothly carrying out an acceleration operation and a deceleration operation for a vibration type actuator to prevent a situation where in starting the vibration type actuator, a drive frequency is reduced to become lower than a resonance frequency to stop the vibration type actuator. A first counter performs up-count from a first value to a second value larger than the first value at predetermined time intervals in accelerating the vibration type actuator. A rate multiplier outputs a clock signal having a frequency corresponding to the count value. A second counter measures a period of a pulse signal, the period being adapted to change in correspondence to a drive speed of the vibration type actuator, by counting the clock pulses. The drive speed of the vibration type actuator is controlled such that the measured pulse period becomes a predetermined target value.

Claims

1. A vibration type actuator drive controller for controlling a drive speed of a vibration type actuator adapted to excite a vibration member by applying an A.C. signal to an electromechanical energy transducer to obtain a drive force, comprising:

an encoder which outputs a pulse signal having a period adapted to change in correspondence to the drive speed of the vibration type actuator;

a counter which carries out up-count from a first value to a second value larger than the first value at predetermined time intervals while the vibration type actuator is accelerated;

clock output unit which outputs a clock signal having a frequency corresponding to a count value of the counter;

measurement unit which measures the period of the pulse signal outputted from the encoder by counting clock pulses of the clock signal outputted from the clock output unit; and

control unit which controls the drive speed of the vibration type actuator such that the period of the pulse signal measured by the measurement unit becomes a predetermined target value.

2. A vibration type actuator drive controller according to Claim 1, wherein the counter carries out down-count from the second value to a predetermined value smaller than the second value at predetermined time intervals while the vibration type actuator is decelerated.

3. A vibration type actuator drive controller according to claim 1, wherein when the vibration type actuator is instructed to be decelerated while the vibration type actuation is accelerated and the count value of the counter is a third value between the first value and the second value, the counter carries out down-count from the third value to a predetermined value smaller than the third value at predetermined time intervals.

4. A vibration type actuator drive controller according to claim 1, wherein the clock output unit comprises a rate multiplier adapted to have the count value of the counter as rate data.

5. A vibration type actuator drive controller according to claim 1, further comprising:

timing control unit which controls a timing at which the counter is operated in accordance with an external command.

6. A vibration type actuator drive controller according to claim 5, wherein the timing control unit comprises a ring counter having a value of the external command as its period.

7. A vibration type actuator drive controller according to claim 1, further comprising a plurality of logic circuits, wherein the plurality of logic circuits are a synchronous circuit adapted to operate in accordance with an identical clock signal.

8. A vibration type actuator drive controller according to claim 1, wherein the control unit controls the drive speed of the vibration type actuator by changing a frequency of the A.C. signal applied to the electromechanical energy transducer.

9. A vibration type actuator drive controller according to claim 1, wherein the control unit controls the drive speed of the vibration type actuator by changing a voltage of the A.C. signal applied to the electromechanical energy transducer.

10. A vibration type actuator drive controller according to claim 1, wherein the control unit controls the drive speed of the vibration type actuator by changing a phase difference between the plurality of A.C. signals applied to the electromechanical energy transducer.

11. A method of controlling a drive speed of a vibration type actuator adapted to excite a vibration member by applying an A.C. signal to an electromechanical energy transducer to obtain a drive force, comprising:

outputting a pulse signal having a period adapted to change in correspondence to the drive speed of the vibration type actuator;

counting a count value by carrying out up-count from a first value to a second value larger than the first value at predetermined time intervals while the vibration type actuator is accelerated;

outputting a clock signal having a frequency corresponding to the count value;

measuring the period of the pulse signal by counting clock pulses of the clock signal; and

controlling the drive speed of the vibration type actuator such that the period of the pulse signal becomes a predetermined target value.

12. A method of controlling a drive speed of a vibration type actuator according to claim 11, wherein the counting is conducted by carrying out down-count from the second value to a predetermined value smaller than the second value at predetermined time intervals while the vibration type actuator is decelerated.

13. A method of controlling a drive speed of a vibration type actuator according to claim 11, wherein when the vibration type actuator is instructed to be decelerated while the vibration type actuation is accelerated and the count value is a third value between the first value and the second value, the counting is conducted by carrying out down-count from the third value to a predetermined value smaller than the third value at predetermined time intervals.

14. A method of controlling a drive speed of a vibration type actuator according to claim 11, wherein the clock signal outputting is carried out by using a rate multiplier adapted to have the count value as rate data.

15. A method of controlling a drive speed of a vibration type actuator according to claim 11, further comprising:

controlling a timing at which the count value is obtained in accordance with an external command.

16. A method of controlling a drive speed of a vibration type actuator according to claim 15, wherein the timing controlling is carried out by using a ring counter having a value of the external command as its period.

17. A method of controlling a drive speed of a vibration type actuator according to claim 11, wherein the method is implemented by using a plurality of logic circuits, and the plurality of logic circuits are a synchronous circuit adapted to operate in accordance with an identical clock signal.