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Initially Clamped Piezoelectric Inchworm Linear Motor based on Force Amplification Mechanisms Design for Miniaturized and Large Force Actuation Applications
1  Mechanical and Medical Engineering, Furtwangen University, Robert-Gerwig-Platz 1, 78120 Furtwangen (registering DOI)

Piezoelectric inchworm linear motor (PZT-ILM) are common in high precision positioning applications, such in optical equipment and precision manufacturing. PZT-ILM can be realized with one or multiple PZT stacks. The positioning of an object is performed either through direct contact of PZT elements that are functioning in shear mode [1-2], or indirect contact, through flexural mechanisms, where the PZT elements are functioning in normal mode [3-4]. The main advantage of using flexural mechanism is to enhance the reliability against damaging. Fortunately, flexural mechanisms can be also designed to amplify the generated displacement or force by PZT stack. However, miniaturization, large-force actuation capability, large internal stresses, fragile flexural design based on lever concept and requirement for high precision manufacturing are main challenges for realizing PZT-ILM based amplified mechanisms.

In this paper, a novel monolithic structural design of PZT-ILM utilizing three Force-Amplification-Mode (FAM) mechanisms is presented as an approach to overcome the fore mentioned design challenges. The new design consists of three main integrated mechanisms, such that each is driven by single PZT element. Two clamping mechanism, initially confined by a mechanical guidance, and become released when the corresponding PZT element is electrically polarized.

The other mechanism is centered between the clamping units, and perform device stretching when the corresponding PZT element is electrically polarized. In this work, a mechanical system model based on Simulink software was developed for a proposed design of a FAM PZT-ILM. The dynamic response of the motor was simulated at the moment of releasing the pre-stressed stretching mechanism, where one clamping mechanism is subjected to friction force, while the other clamping unit is free to move. The results showed backlash response due to the mass acceleration of the mechanisms. The effect of applying mechanisms of different mass amounts on the overall dynamic behavior was also investigated.

[1] H. Huang, L. Wang, Y. Wu; Design and Experimental Research of a Rotary Micro-Actuator Based on a Shearing Piezoelectric Stack, Micromachines 2019, 10, 96; 2019.
[2] B. Zhao, R. Fang, W. Shi; Modeling of Motion Characteristics and Performance Analysis of an Ultra Precision Piezoelectric Inchworm Motor; Materials 2020; 13, 3976; 2020.
[3] L. Ma, C. Jiang, J. Xiao, K. Wang; Design and analysis of a piezoelectric inchworm actuator; Journal of MicroRobot 2014, 9:11-21; 2014.
[4] X. Chen, M. Li, H. Zhang, Q. Lu, S. Lyu; Improvement on the Structure Design of a Kind of Linear Piezoelectric Motor with Flexible Drive-Foot; International Journal of Precision Engineering and Manufacturing 2020, 21:81-89; 2020.

Keywords: Force Amplification Mechanisms; Piezoelectric Actuator; Inchworm Motor