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