| Popis: |
Accurate estimations of the height and velocity of precision airdrop systems are required to control final deceleration maneuvers. Airdrop systems have a limited deceleration window, so robust and reliable estimations are required. Radar, sodar, and lidar sensors have all been evaluated for this role with varying degrees of success. Foliage and vegetation prove troubling for many of the sensors. However, sodar has been shown to successfully penetrate ground vegetation at certain frequencies. The development and testing of a Sodar Height Sensor (SHS) for precision airdrop applications is reported in this paper. The SHS incorporates a speaker, a microphone, a barometer, and temperature sensors. Estimation algorithms running on a Digital Signal Processor (DSP) produce continuous estimates of the sensor height above ground. The sensor's performance has been characterized in a series of laboratory, field, and airdrop tests. Ground detection ranges in excess of 1,000 ft have been demonstrated in certain mounting configurations while a height estimation accuracy of ± 2 ft has been measured closer to the ground. |
