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  3. Inertial guidance is the name given to those types of systems which guide and keep track of the location of vehicles which are f

Inertial guidance is the name given to those types of systems which guide and keep track of the location of vehicles which are f

admin2010-07-06  72
问题      Inertial guidance is the name given to those types of systems which guide and keep track of the location of vehicles which are free to move in three dimensions. Vehicles which move only on a plane surface, such as ships or automobiles, require only an accurate compass, sextant, and clock to keep track of their present position. When a vehicle can travel up or down as well as north or east, it is much more difficult to fix its position. An inertial platform is used in inertial guidance to measure vehicle altitude and acceleration which are then integrated to provide position and velocity. The inertial platform consists of three gyroscopes and three accelerometers mounted in the inner gimbal of the four gimbal platform. The purpose of the inertial platform is to allow the vehicle to move in any direction about the inner gimbal containing the gyros and accelerometers, without disturbing or turning them from their original orientation. Thus the gyros and accelerometers do not mm when the vehicle turns so they sense altitude and acceleration with respect to their original inertial reference frame. If the acceleration is always known with respect to this original inertial reference frame, it can be integrated to provide velocity and then integrated again to provide distance. Thus the distance and velocity of the vehicle with respect to its starting point are known.
     Inertial guidance systems are used today in airplanes, submarines, and spacecraft. They display for the pilot his pitch, roll and yaw angles, his heading, his speed, and his latitude and longitude. These are very important items to have readily available, whether one is in a high speed vehicle with very low visibility due to poor weather, or in a spacecraft traveling in lunar orbit. The main features of inertial systems are that they are automatic and do not require any external information. Thus, the pilot does not have to feed in any information except the original position and altitude. Inertial systems serve a need on fast moving vehicles moving in a three dimensional plane, where position information is required by the pilot almost constantly.
Spaceships need an inertial guidance system, but automobiles do not because of
选项 A、the relative speed of the vehicles.
B、the relative size of the vehicles.
C、the relative cost of the vehicles.
D、their different methods of travel.
答案D
解析 本题考查推理判断。从文章所介绍的制导系统的功能和用途可知，它在一个立体的范围内制导(即文章中所述的不仅朝南北、东西方向，而且朝上下方向)，而汽车不像宇宙飞船那样朝上朝下运动，它只是沿平面运动。由此可知，汽车不需要惯性制导系统，是因为它们的运动方式不同，故正确答案为D 。惯性制导系统与运动体速度、大小和成本均无关，所以选项A ，B ，C 都是错误的。
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