The electric actuators each contain four resistive strain gauges, which are directly connected to the piezoelectric actuators in a Wheatstone bridge structure. These actuators are suitable for closed-loop systems that monitor and use strain signals to determine piezoelectric control drive voltages. Compared with the open-loop configuration, the closed-loop configuration can enhance the control and mastery of the displacement of the actuator during the working process. Moreover, the closed-loop configuration can compensate for the hysteresis effect.

Four foil strain gauges are mounted on the epoxy coating of the sealed driver, and the leads are welded to the end of the strain circuit. The two strain gauges are adjacent to each other, glued along one side of the actuator, and the other two strain gauges are glued to the opposite side. For each pair of strain gauges, one is an active strain gauge and the other is a passive strain gauge. The active strain gauge responds greatly to the length change of the actuator. The passive strain gauge makes a small response to the change of the length of the actuator; It mainly responds to the change of temperature and can reduce the influence of temperature change on strain measurement.

The leads of both drivers are welded to the positive and negative electrodes of the drivers. The co-sintered piezoelectric actuator is composed of lead zirconate titanate (PZT) layer and electrode layer alternately, and then sintered into a whole structure. The discrete stack piezoelectric actuator is formed by connecting a plurality of individually sintered piezoelectric chips with epoxy resin and glass beads. Other differences between the two designs include differences in joint and insulation details.