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6. servo [ P1-132 ]
B. Translate the lst, 4th and 5th paragraphs of lesson 31 into Chinese
C. Explain the following abbreviations
1. VMO
2. ADC
3. OX
4. MB
5. FCC
6. CAS
D. Answer the questions 1～15 that are given for lesson 31 Reading
material.
LESSON 32
INERTIAL REFERENCE SYSTEM
VOCABULARY
1. IRS = Inertial Reference System 慣性基準系統
2. FMS = Flight Management System 飛行管理系統
3. be responsible for [ ris'p nsbl ] 對…負責
4. baseline [ 'beislain ] a. 基本的;原始的
5. IRU = Inertial Reference Unit 慣性基準裝置
6. MSU = Mode Select Unit [ moud ] 方式(狀態)選擇組件
7. DAA = Digital-to-Analog Adapter 數一摸轉換器(適配器)
['did itl] ['ænl g]['dæpt]
8. alignment [ 'lainmnt ] n. 對準;校準
9. laser [ 'leiz ] n. 激光
10. gyro [ 'd airou ] n. 陀螺
11. accelerometer [ æksel'r mit ] n. 加速度表(計)
12. ground speed 地速
13. drift angle [ drift ]['ægl ] 偏流角
14. present position [ 'preznt ] 當前位置
15. orient [ ' :rint ] vt. 取向
16. orientation [ :rien'tein ] n. 取向
17. strap-down [ stræp ] n. 捷聯式
18. with respect to [ ris'pekt ] 關于;相對于;就…而言
19. manipulation [ mnipju'lein ] n. 計算;處理
20. along with … 與…一道;隨著
21. local vertical [ 'loukl ] [ 'v:tikl ] 當地垂線
22. true north [ tru: ] [ n : ] 真北(方向)
23. premise [ 'premis ] n. 前提
24. perpendiculur [ p:pn'dikjul] a. 與…垂直的;正交的
25. manipulate [ m'nipjuleit ] v. 計算;運算;處理
26. modify [ 'm difai ] vt. 修正(改);改進
27. real time [ ril ] 實時
28. minimize [ 'minimaiz ] vt. 使…降到最小(值
29. inadvertent [ind'v:tnt ] a. 偶然的;不注意的
30. barrier [ 'bæri ] n. 攔阻裝置;卡子;擋扳
31. progress [ 'prougres ] v. 進行;進展
32. enable [ i'neibl ] vt. 使能夠;起啟動
33. degrade [ di'greid ] v. 削減;降低
34. shutdown [ 't'daun ] n. 關閉;停止運轉
35. procedure [ pr'si:d ] n. 程序;步驟;過程
TEXT
[1] The inertial reference system (IRS) is one part of the Flight
Management System (FMS). It is responsible for providing baseline
navigation information, vertical speed, and airplane altitude information.
The IRS consists of two inertial reference unit (IRU), a mode select unit
(MSU) , an inertial system display unit (ISDU) and two digital-to-analog
adapter (DAA). Latitude and longitude are entered into the system at the
starting point during alignment. After alignment, airplane movement is
sensed by inertial laser gyros and accelerometers. The movement is
computed by the IRS, and provided as output data to other airplane
systems. Output data includes ground speed, drift angle, present position,
attitude, heading, and angular information .
Fig. 32-1 inertial reference system
[2] The IRS provides heading and attitude reference information by
utilizing computations based on accelerometer and laser gyro sensed
signals. Three accelerometers and three laser gyros are used. The
accelerometers are positioned in the inertial reference units so that they
are oriented along the x, y and z axes of the airplane. This orientation
allows the IRU to sense accelerations along each of the three axes. The
three laser gyros are positioned to sense pitch, roll and yaw rotation
around the x, y , and z axes. These accelerometers and laser gyros are in
the strap-down configuration. That is , they are oriented with respect to
each of the aircraft's three axes and are not allowed to move when the
aircraft rotate about or accelerates along any of these axes. Computer
manipulation of the signals from all six sensors provide the basic heading
and attitude reference signals along with present position, accelerations,
ground speed, drift angle and attitude rate information.
Fig. 32-2 IRS general theory
[3] The first requirement which must be met for proper IRS operation is
alignment, IRS alignment basically consists of determination of local
vertical and true north. Both accelerometer and laser gyro inputs are used
for alignment. The alignment computations use the basic premise that the
only accelerations during alignment are caused by earth's gravity. The
only motion during alignment is caused by the earth's rotation.
Acceleration because of gravity are always perpendicular to the earth's
surface, see figure 32-3. Three accelerometers are used to sense the
　
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