具缺陷補償、直接角度量測之壓電陀螺儀系統(I)

Abstract

微機電運動感測器仍蘊藏龐大商機，根據市場研究機構The Information Network 預估： 2012 年 全球MEMS 應用市場規模將達154 億美元。目前市場上的運動感測器仍以加速度計為主，因其性能 符合要求且價格便宜。市場普遍看好的陀螺儀則成長緩慢，主要原因為元件（機械結構、感測電路） 製作精度要求較高，導致成本過高、普及不易。 由文獻回顧得知，決定微機械陀螺儀性能的三大因素：（1）機械結構缺陷（imperfections）（2） 感測電路缺陷（3）在獲得角度過程中，積分所造成的誤差累積。而目前有關陀螺儀性能改善的研究 報告中，大多是利用昂貴的後製程（post processing）來改善機械結構缺陷；複雜的線路設計來改善 感測電路缺陷，僅有少數文獻利用回授控制技術來補償機械結構的不確定性，尚未發現任何文獻利 用回授控制來補償感測電路的缺陷。此外，僅有少數的文獻提出可直接量測角度的陀螺儀控制方法， 然而該方法僅適用於「完美」的陀螺儀機械結構與感測電路（系統參數已知）。 本計畫主要針對微機電陀螺儀開發一套完整的即時控制系統，將機械結構的非理想現象、感測線 路的非理想現象一併估測、補償，並進而控制陀螺儀的動態，直接獲得角度資訊。由於是以控制器 設計（軟體）來提升陀螺儀性能，預期可大幅降低陀螺儀製作成本與技術門檻。此一控制器設計已 獲初步成果，並於國際研討會中發表。本計劃將持續進行此控制器設計的改善與探討，同時對於此 一控制器的實現，設計製作壓電式陀螺儀，規劃一系列的實驗，以三年的時程來逐步驗證具直接角 度量測的微機械式陀螺儀的可行性。

The market of MEMS motion sensors keeps growing vastly. According to the investigation by The Information Network, the market of MEMS will be 15.4 billion in 2012 by prediction. The most popular MEMS motion sensors in the market now are accelerometers. They are widely used in consumer electronics products due to its acceptable performance and low cost. Oppositely, the complicated component designs and high cost due to inextricable trimming process seriously limit the market growth of MEMS gyroscopes. According to paper surveys, three issues dictate the performance of MEMS gyroscopes, which are: mechanical structure imperfections, interface circuit imperfections, and error accumulations when obtaining rotation angles from angular rate measurements. Most researches proposed using “post processing” to trim mechanical structures, and complicated circuit designs to null out the circuit imperfections. Meaning that, in those approaches, the mechanical structures and interface circuits were optimized physically (in hardware) and individually. As a consequence, MEMS gyroscopes are rather expensive. Only a few papers proposed using control techniques to compensate mechanical structure imperfections; none of a paper has been found compensates interface circuit imperfections with control techniques. Besides, only a few papers proposed control algorithms that can obtain rotation angles without the error accumulation problem. The reason could be that those methods were only applicable to gyroscope systems wherein most of the system parameters are known. In this project, we proposed using control techniques to estimate and compensate the effects from both mechanical structure imperfections and interface circuit imperfections. The compensated system dynamics can be used to obtain rotation angles without the error accumulation problem. Because the proposed method improves the system performance by control techniques, it is expected to lower the fabrication cost of gyroscopes substantially. The proof-concept simulation results have been obtained and presented in an international conference. We plan to continue developing this control algorithm and proceed a series of experiments to demonstrate its feasibility. By the end of this three-year project, we plan to demonstrate a working piezoelectric gyroscope accompanied with the capability of imperfection compensations and direct angle measurements.