![]() ![]() The reason for this is the small stroke of the piezo actuators, which need to be aligned carefully to each other. The piezo stepper motor however is particularly prone to wear, because a good operation requires strict tolerances. Next to that, during stepping, the contacts will wear off like in any kind of frictional contact. Subsequently, piezo C is retracted to its original position, resulting in state number 4.įinally, piezo B is extended again and piezo A is retracted, restoring the initial conditions of the first state.īecause of the different steps involved in the moving mechanism, a piezo stepper motor typically achieves low travelling speeds (i.e. Now only piezo A is in contact with the slider, see state 3. Next, piezo A is extended and piezo B is retracted. Piezo C is expanded to realize the translational motion of the slider via the contact of piezo B, which is shown in state 2. Only the contact point of piezo B remains in contact with the slider. During the start of a motion cycle, which is shown in state 1 in Figure 2, piezo A is retracted while piezo B is expanded. piezo C in Figure 2).Īt rest, both piezos A and B are in contact with the slider. actuator A and B in Figure 2) and act as a clamping mechanism, while others are used to generate the translational motion of the slider (i.e. Some of the actuators are in contact with the slider (i.e. (Hunstig, 2017)Ī typical stepping piezo motor consists of at least three piezo actuators. Researchers from the Paderborn University in Germany have written a review paper, which presents a more detailed overview of all commercially available stick-slip and inertial piezo motors. The speed of most common stick-slip piezo motors is limited to about 20 mm/s. Although this is effective to perform fine positioning, it becomes impossible to keep the final position stable at nanometer level with zero drift, or without powering the motor. Some stick-slip motors use a DC scanning mode to realize a very fine resolution. ![]() A stick-slip motor is characterized by a minimum step size during motion and it is virtually impossible to achieve a high repeatability because the step size depends on many operating conditions (for instance the motion direction). The impact-based driving mechanism also causes a significant amount of wear in the contact materials, typically limiting the lifetime of this type of stages. The noise can be very irritating and sometimes even cause health issues, especially when humans need to operate in the vicinity of the device. The impact on the stage, which occurs during the slipping phase, causes an excitation of the system dynamics. More information about this type of motor can be found in “Piezoelectric Inertia Motors – A Critical Review of History, Concepts, Design, Applications, and Perspectives” (Hunstig, 2017). Although the driving signals are identical to the stick-slip principle, the inertial motor does not have a slipping contact point. By repeating these two steps, a macroscopic movement is realized.Ī very similar type of piezo motor is called the ‘inertial’ piezo motor. This is called the ‘slip-phase’ and results in a net displacement of the slider. Because of the inertia of the slider, it remains stationary and the contact point slips back to its original position. Then, the piezo actuator is rapidly retracted by applying a rapidly decreasing voltage, see state 3 in Figure 1. ![]() The slider moves together with the moving contact point because of the friction force between the contact point and slider. During the ‘stick-phase’, which is shown in state 2, the piezo is slowly extended because of a slow increase in voltage. ![]()
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