具有V型夾持致動器之線性超音波馬達

Abstract

摘 要 本論文研發一種線性超音波馬達，以V型定子夾持推桿前進及後退運動。將正交的弦波電壓施加於V型梁定子正反面貼附的兩組壓電片，激振耦合之撓曲振動模態。第一面內對稱撓曲模態及第二面外撓曲模態耦合，使得定子內側兩個接觸點進行橢圓形軌跡面外往復運動，藉摩擦力推動推桿，兩弦波之間的相位延遲或領先可切換推桿的運動方向。精細地調整定子尺寸可將目標之撓性模態共振頻率耦合於29.2 kHz。本文將超音波馬達定子的有限元素分析程序歸納成一定子設計流程。定子的共振頻率對於基定子座固定螺栓扭矩值非常敏感，因此提出一強健性設計，避免共振頻率因扭矩大小而改變。本研究以鋁合金及PZT-4壓電陶瓷元件製作超音波馬達原型機定子，進行性能測試。以300 Vp-p電壓驅動，單一定子推動直徑8 mm 之不銹鋼推桿，最高線性速度可達85 mm /s，最大推力為0.539 N，將定子堆疊可以產生更大的推力。

關鍵字：線性超音波馬達、V型梁定子、耦合振動模態、面外往復運動、強健性設計

ABSTRACT

This thesis presents a linear ultrasonic motor with the Chevron clamp stator which is used to propel a push rod forward and backward. Two orthogonal sinusoidal voltages are applied to two sets of piezoelectric elements adhered on the opposite faces of the V-shaped beam stator to excite two coupled flexural vibration modes. Two contact points located on the inner sides of the stator undergo an out-of-plane elliptical trajectory formed by the fundamental in-plane symmetric mode and the second out-of-plane mode. The rod was propelled via friction force, and its moving direction could be switched by phase lag or lead between two sinusoidal inputs. The target flexural modes were fine-tuned to approach a consistent resonant frequency at 29.2 kHz through adjusting dimensions of the stator. A flow chart based on finite-element analysis for modal coupling of the stator is summarized. Resonant frequencies of the stator are sensitive to the value of base screw torque. A robust design for the stator successfully gets rid of the frequency change. A prototype stator made of aluminum alloy and PZT-4 was use to carry out the performance tests. A single stator can achieve the highest linear speed up to 85 mm/s and the maximum thrust 0.539 N for a stainless steel push rod of diameter 8 mm and different lengths under an applied voltage of 300 Vp-p. The stator can be stacked to induce more thrust on the push rod. Keywords: linear ultrasonic motor, V-shaped beam stator, coupled vibration modes, out-of-plane oscillating motion, robust design