Piezoelectric actuator, robot hand, and robot

A robot hand comprising:

• a vibrating body including a piezoelectric device that operates a moving member;
• a driving unit that supplies a driving signal to the piezoelectric device;
• an oscillator that supplies a frequency to the driving unit to make the driving signal;
• a phase difference detector that detects a phase difference between the driving signal and a detection signal detected based on vibration of the vibrating body;
• a control unit that controls the frequency and a voltage for the driving signal based on a fast sweeping state, a slow sweeping state and a phase difference control state of the piezoelectric actuator, the control unit having a state transition controller that supplies a frequency value to the oscillator;
• and
• a plurality of finger portions, wherein
• the state transition controller changes the frequency value by a first frequency change rate during the fast sweeping state,
• the state transition controller changes the frequency value by a second frequency change rate that is smaller than the first frequency change rate during the slow sweeping state,
• the control unit sets the voltage to an upper voltage value when the phase difference is within a predetermined range by changing the frequency during the phase difference control state, and the control unit sets the voltage to a lower voltage value, which is smaller than the upper voltage value, when the phase difference is outside the predetermined range, and
• when the driving signal, which corresponds to the lower voltage value, is supplied to the piezoelectric device, the piezoelectric device vibrates so that the phase difference detector detects the phase difference and the piezoelectric device operates the moving member.

A robot comprising:

• a vibrating body including a piezoelectric device that operates a moving member;
• a driving unit that supplies a driving signal to the piezoelectric device;
• an oscillator that supplies a frequency to the driving unit to make the driving signal;
• a phase difference detector that detects a phase difference between the driving signal and a detection signal detected based on vibration of the vibrating body;
• a control unit that controls the frequency and a voltage for the driving signal based on a fast sweeping state, a slow sweeping state and a phase difference control stare of the piezoelectric actuator, the control unit having a state transition controller that supplies a frequency value to the oscillator;
• and
• a pivotable arm portion, wherein
• the state transition controller changes the frequency value by a first frequency change rate during the fast sweeping state,
• the state transition controller chances the frequency value by a second frequency change rate that is smaller than the first frequency chance rate during the slow sweeping state,
• the control unit sets the voltage to an upper voltage value when the phase difference is within a predetermined range by changing the frequency during the phase difference control state, and the control unit sets the voltage to a lower voltage value, which is smaller than the upper voltage value, when the phase difference is outside the predetermined range, and
• when the driving signal, which corresponds to the lower voltage value, is supplied to the piezoelectric device, the piezoelectric device vibrates so that the phase difference detector detects the phase difference and the piezoelectric device operates the moving member.