Initially Clamped Piezoelectric Inchworm Linear Motor based on Force Amplification Mechanisms Design for Miniaturized and Large Force Actuation Applications

Hussam Kloub

Abstract:

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.

Literature
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