| 摘要: | 每年全世界的截肢人數因意外事故、疾病或老化逐年攀升，但是由於設備價格及人員短缺，導致開發中國家仍有75%的人尚未使用義肢，為了降低人員訓練的時間及門檻，一套便於使用且準確的量測系統便成為重要的議題。本研究目的在於建立一套能夠便於擷取義肢穿戴者下肢步行步態的裝置與系統，協助使用者及專業人員能容易且客觀的分析下肢姿態；透過安裝7組Wi-Fi無線慣性感測器於受試者下肢(包含腰部、左右大腿下外側、左右小腿下外側以及左右腳背處等)，擷取行走時的線加速度及角速度，分析受試者下肢行走軌跡及步態參數，包含骨盆水平面、矢狀面旋活動角度，髖、膝及踝關節屈曲角度、身體橫向位移等，提供醫師或義肢矯具師量化結果，方便客觀地評估患者復健及穿戴適當性，利於復健計畫修正及義肢調整。
考量先前演算方式不周全，導致需要費時比對及可能誤差，本研究提出3種修正演算法，包括(1)根據用行走特徵，將誤置座標方位的慣性感測器修正為正確的座標系統，結果能修正誤置所造成不合理的活動角度與肢體動作； (2)利用踝關節腳背傾斜補償演算法，將腳背上IMU從傾斜狀態修正為水平，校正後能改善傾斜所帶來的誤差，能夠傾斜誤差降低到1度以下； (3)根據傅立葉分析原則，消除直流分量與雜訊，相比實驗室先前使用的Madgwick演算法降低了1度左右的誤差。藉由上述修正演算法能提高計算準確度，有利於醫師或義肢裝具師正確判讀受試者的運動姿態與步態軌跡。
研究中分別以商用機器手臂、旋轉平台、及激振器驗證本系統之信度與效度。在機械手臂實驗，二維運動軌跡誤差百分比為1.36 – 1.7%，三維運動軌跡則介於2.86 – 2.97%；旋轉平台實驗的陀螺儀每軸RMSE小於0.73°；激振器實驗的加速規每軸RMSE小於0.03 g。
研究中收錄5位膝上與9位膝下義肢穿戴受試者10m步行實驗的慣性感測資料及計算其步態參數，分組分析(1)骨盆旋轉角度、(2)骨盆傾斜角度、(3)膝關節站立期的背屈角度、(4)踝關節機構、及(5)身體航向位移。結果顯示義肢穿戴者骨盆水平面與矢狀面的穩定性較差，旋轉與傾斜角度範圍較大，分別為 14.7°與 6.4°；因代償作用導致膝上與膝下義肢穿戴受試者的患側膝關節ROM分別為 52.6°與 45°，略大於健側；患側踝關節ROM會受義肢限制，分別為22.7°與 22.1°，略小於健側。
;The number of amputees worldwide is increasing every year due to accidents, diseases, and aging, but 75% of people in developing countries still do not use prostheses due to the cost of equipment and shortage of personnel. The purpose of this study is to develop a device and system that can easily capture the walking gait of the lower extremities of prosthesis wearers, to help users and professionals to analyze the lower extremity posture easily and objectively. The walking trajectory and gait parameters of the subject′s lower extremities are analyzed, including the pelvic horizontal and sagittal plane rotation angles, hip, knee, and ankle flexion angles, and lateral body of displacement, etc. The results are quantified by the physician or prosthetist to facilitate objective assessment of the patient′s rehabilitation and wear appropriateness for revise rehabilitation project and prosthetic adjustment.
In view of the time consuming comparison and possible errors caused by the incomplete calculation methods, this study proposes three correction algorithms, including (1) The inertial sensors with misaligned coordinates were corrected to the correct coordinates system based on the walking characteristics, which resulted in the correction of unreasonable movement angles and limb movements caused by the misalignment; (2) The ankle dorsal foot tilt compensation algorithm was used to correct the IMU on the dorsal foot from tilt to horizontal, which improved the error caused by tilt and reduced the tilt error to less than 1 degree; (3) The Fourier analysis principle was used to eliminate DC components and noise, which reduced the error by about 1 degree compared with the Madgwick algorithm previously used in the laboratory. The above correction algorithm can improve the accuracy of calculation and facilitate the physician or prosthetist to correctly interpret the subject′s motion and gait trajectory.
The reliability and validity of the system were verified with a commercial robotic arm, a rotating platform, and a shaker. In the robotic arm experiment, the percentage error of the 2D motion trajectory was between 1.36 - 1.7%, and the 3D motion trajectory was between 2.86 - 2.97%; the RMSE of the gyroscope was less than 0.73° per axis in the rotating platform experiment; and the RMSE of the accelerometer was less than 0.03 g per axis in the shaker experiment.
The inertial and gait parameters of the 10m walking experiment were collected from five above-knee and five below-knee prostheses subjects and analyzed in groups for (1) pelvic rotation, (2) pelvic tilt, (3) knee flexion in stance phase, (4) ankle mechanism, and (5) lateral displacement of body. The results showed that the prosthesis wearers had poor stability in the horizontal and sagittal planes of the pelvis, with rotation and tilt angles of 14.7° and 6.4°, respectively; the above-knee and below-knee prosthesis wearers had a slightly greater knee ROM of 52.6° and 45°, respectively, than the healthy side due to compensatory effects; the affected ankle ROM was limited by the prosthesis at 22.7° and 22.1°, respectively, slightly less than the healthy side. The ankle ROM on the affected side was slightly smaller than that on the healthy side at 22.7° and 22.1° respectively. |
