Ultrasonic motor device

Abstract

An ultrasonic motor device includes: an ultrasonic motor that moves an object; a detecting unit that detects movement of the object; and a control unit that drives the ultrasonic motor according to a first driving signal before detection of the movement of the object, and drives the ultrasonic motor according to a second driving signal, which is different from the first driving signal, after detection of the movement of the object.

1 . An ultrasonic motor device comprising: 
 an ultrasonic motor that moves an object;    a detecting unit that detects movement of the object; and    a control unit that drives the ultrasonic motor according to a first driving signal before detection of the movement of the object, and drives the ultrasonic motor according to a second driving signal, which is different from the first driving signal, after detection of the movement of the object.    
   
   
       2 . An ultrasonic motor device according to  claim 1 , further comprising a transmission unit that transmits driving force of the ultrasonic motor to the object, wherein the control unit controls transmission error in the transmission unit by driving the ultrasonic motor according to the first driving signal.  
   
   
       3 . An ultrasonic motor device according to  claim 2 , wherein the transmission unit includes a gear train.  
   
   
       4 . An ultrasonic motor device according to  claim 1 , wherein the control unit sets the first driving signal and the second driving signal such that a driving speed of the ultrasonic motor driven according to the second driving signal is faster than a driving speed of the ultrasonic motor driven according to the first driving signal.  
   
   
       5 . An ultrasonic motor device according to  claim 1 , wherein the control unit detects a movement speed of the object which is the same as a movement speed of the object driven according to the first driving signal, during at least one of a time of acceleration and a time of deceleration when the ultrasonic motor is driven according to the second driving signal.  
   
   
       6 . An ultrasonic motor device according to  claim 1 , wherein the control unit drives the ultrasonic motor according to the second driving signal, following driving the ultrasonic motor according to the first driving signal for a predetermined amount of time.  
   
   
       7 . An ultrasonic motor device according to  claim 1 , wherein the detecting unit comprises an encoder.  
   
   
       8 . An ultrasonic motor device according to  claim 1 , wherein the first driving signal is a signal used for driving the ultrasonic motor under open loop control, and the second driving signal is a signal used for driving the ultrasonic motor under feedback control.  
   
   
       9 . An ultrasonic motor device according to  claim 8 , wherein the control unit performs feedback control according to the second driving signal, based on information from the detecting unit.  
   
   
       10 . A lens barrel comprising: 
 a main lens barrel having an optical component; and    an ultrasonic motor device according to  claim 1 .    
   
   
       11 . A lens barrel comprising: 
 a main lens barrel having an optical component; and    an ultrasonic motor device according to  claim 8 .    
   
   
       12 . A camera capable of mounting a lens barrel according to  claim 10 .  
   
   
       13 . A camera capable of mounting a lens barrel according to  claim 11 .  
   
   
       14 . A control method for controlling an ultrasonic motor device, comprising: 
 driving of an ultrasonic motor according to a first driving signal;    detecting of movement of an object moved by the ultrasonic motor; and    driving of the ultrasonic motor according to a second driving signal which differs from the first driving signal, following detection of the movement of the object.    
   
   
       15 . A control method according to  claim 14 , wherein, in an event that the ultrasonic motor is driven according to the first driving signal for a predetermined amount of time before detection of the movement of the object, control mode is switched to a mode in which the ultrasonic motor is driven according to the second driving signal.  
   
   
       16 . A control method according to  claim 14 , wherein a movement speed of the object which is the same as a movement speed of the object driven according to the first driving signal is detected during at least one of a time of acceleration and a time of deceleration when the ultrasonic motor is driven according to the second driving signal.  
   
   
       17 . A control method according to  claim 14 , wherein the first driving signal is a signal used for driving the ultrasonic motor under open loop control, and the second driving signal is a signal used for driving the ultrasonic motor under feedback control.  
   
   
       18 . A control method according to  claim 17 , wherein, in an event that the ultrasonic motor is driven according to the first driving signal for a predetermined amount of time before detection of the movement of the object, control mode is switched to a mode in which the ultrasonic motor is driven according to the second driving signal.  
   
   
       19 . A control method according to  claim 17 , wherein a movement speed of the object which is the same as a movement speed of the object driven according to the first driving signal is detected during at least one of a time of acceleration and a time of deceleration when the ultrasonic motor is driven according to the second driving signal.