一般量測飛機空氣阻力的主要方法有兩種,一是風洞測試,另一個是飛
航測試.其作法是在飛機上裝置量測儀器,諸如慣性感測元件,空速計,引擎
轉速錶,扭力錶,爬昇速錶及高度計等傳感器,來量測推力與阻力大小,以及
量測飛機相對位置的地面雷射雷達.無論是慣性感測,地面雷射雷達追蹤或
是風洞測試都是一項成本極高的測試工作,一般只有較高級的飛機才會採
用.至於較低成本之輕航機或無人遙控飛機,則難以進行. 本研究目標
是發展一成本較低且相當精確的方法以量測低成本飛機的阻力與推力,此
方法是採用GPS來量測位置的變化,設計一GPS量測資料處理架構,來估算飛
航載具的阻力參數。處理架構分兩步驟:1)以最小二平方法(Least
Squares)與差分式GPS(DGPS)求載具的位置解;2)由求得的位置解,利用擴
散式卡爾曼濾波(Extended Kalman Filter)以估算輕航機阻力係數及推力
係數. 本研究中以型號為MXL II的輕航機做飛行測試,由上述處理方式
所得之結果,與Datcom所解算出之輕航機性能造型估算值比較,阻力係數與
推力參數的差異量在1%之內.然而在第二動態模組中加入飛行路徑角的估
算,可減少側風的影響.

In general, there are two methods in measuring the
aerodynamic drag of anairplane. One approach is to use the wind
tunnel testing while the other is the in-situ measurement on the
airplane. The later method requires installing the on board
sensing devices such as inertial navigation system(INS),
airspeed,engine speed, torque, rate of climb, altitude
transducers in sensing the thrust and drag forces or of the
ground laser radars in sensing the relative positioning
changes. The operation cost is usuay very high regardless which
methodapproaches is used. In general, only the operation on
those expensive aircrafts will be conducted.As for those low-
cost airplanes like ultra-light ones or RPV, such kind of
testings cannot be afforded. The aim of this study is to
develop a low-cost but fair precise method insensing the drag
and thrust forces for a low-cost airplane. The method uses the
GPS observable in measuring the positioning changes. The
research is designed to establish a data processing structure so
as to precisely estimate the aerodynamic drag parameter. The
structure includes: 1) the positioning determination with using
the least-squares algorithm and Differential GPS(DGPS)
correction technique; 2) the estimation of thrust parameters and
drag coefficients from the above position solutions with using
EKF algorithm. Several flight testings are conducted with an
ultra-light airplane of MXLII. The solution is compared against
the performance modeling prediction of Datcom. The results show
that both the drag coefficient and thrust parameter canbe
adequately estimated by the designed data processing structure.
In comparison with Datcom, the difference is within 1%. With the
designed dynamic Model II of additional flight path angle
estimation, the effect of gust wind can be greatly reduced.