使用平面加速規及磁場感測器之姿態估測器

Abstract

傳統上主要有以下三種方法獲得物體在3 維空間的姿態：(1)利用3 軸陀螺儀量測物 體的角速度，經過一次積分可獲得物體姿態角。(2)使用3 軸加速規及3 軸磁場感測器， 量測物體所受的重力及磁場強度，經由計算可獲得物體的姿態。(3)使用3 軸陀螺儀、3 軸加速規及3 軸磁場感測器配合卡爾曼估測理論求得最佳的姿態估測。以上的3 種方法 皆有其優缺點及限制。在方法(1)中，因為經由一次積分運算而造成誤差的累積。在方法 (2)中，感測器雜訊會降低或干擾姿態量測的精確度。而方法(3)中，利用估測器計算可 獲得比前述(1)(2)法中更精確的姿態，不過卻比方法(2)多裝置3 軸陀螺儀。 在本論文中，我們提出新式的方法使用平面式純加速規慣性感測單元(coplanar gyro-free IMU)以及磁場感測器來獲得物體的姿態。平面式純加速規慣性感測單元有別於 一般純加速規慣性感測單元(gyro-free IMU)，所有感測元件皆在同一個平面上，無需複 雜3 維空間的放置及對準，並且可取代昂貴的陀螺儀。並由最後模擬的結果，論文中所 提方法的姿態估測精度介於上述法(2)及法(3)。此外，在論文中經由觀測性矩陣的分析， 此系統只使用6 顆單軸加速規及2 軸的磁場感測器，即可估測出物體的姿態。

Typically, there are three ways to measure the attitude of an objection in 3D space, which are (1) 3-axes gyroscopes and a subsequent integral operation, (2) 3-axes linear accelerometers and 3-axes magnetic sensors, (3) 3-axes linear accelerometers, 3-axes gyroscopes and 3-axes magnetic sensors. There are problems and constrains in each approach. Particularly, the first approach suffers from the error accumulation, the second approach suffers from the sensing accuracy and the third approach achieves the best performance among all at by employing expensive gyroscopes components. In this thesis, we present a novel approach using coplanar gyro-free IMU accompanied with magnetic sensors for the attitude measurement. The coplanar gyro-free IMU has the advantages that all the employed sensing devices are situated in the same plane. Furthermore, it measures angular rates without expensive gyro components. Simulation results indicated that we can obtain 3 orientation angles with the measurement accuracy in between the second approach and third approach mentioned above. Moreover, results also suggest that it is possible to use 6 linear accelerometers and 2-axes magnetic sensors to obtain 3 orientation angles with some prior information assumed.