Abstract
This paper deals with a force estimation method by using driving current of a piezoelectric actuator. Because the size of sensors sometimes restricts the size of a whole device, a sensor-less control is preferable to build a device compactly. A mechanical clamp device including the actuator was represented as an equivalent electric circuit by applying Martin's model, and a force change is calculated from the driving current. Although only dynamic behavior generates the electric charge in the piezoelectric actuator, a static stress varies its piezoelectric constant. Then the stiffness of the piezoelectric actuator will change. The preload of the piezoelectric actuator can be estimated from the resonant frequency of residual vibration of the driving current, which coincided with the mechanical vibration of the device. Consequently, the generated force can be represented as a linear function of the applied voltage and resonance frequency of the current. The force containing the static preload was estimated with an error less than 12% for step response.
