Contact Force Estimation and Sensorless Force Control in Piezoelectric Bending Actuators

Abstract

This paper presents a sensorless approach for contact force estimation and control of piezoelectric bending actuators. A high-accuracy force sensor is generally used to control the interaction force between a manipulator and contact object. In contrast, sensorless control is desired to reduce the cost and installation space in micro/nano-scale working systems. In this study, the contact force is computed according to the mechanical/electrical models under the contact conditions with the environment. A dynamic model including the creep phenomenon is considered for the static mechanical model. In addition, a self-sensing technique is introduced to separate the actuation and sensing voltages, wherein the passive elements are connected in series with the piezoelectric bending actuator. The force is estimated from the model using the voltage applied to the actuator and the voltage across the passive elements as inputs. The parameters used in the model are calibrated through preliminary tests. A feedback control system based on the estimated signal is evaluated from experiments using a piezoelectric bending actuator and different contact objects.