Design and Analysis of an Active Jet Control System for Helicopter Sling Loads

摘要

An active jet control system for stabilizing the swinging motion of helicopter external sling loads in hover (and forward flight) is described. A velocity feedback control law is obtained by using classical control theory. A nondimensional analysis is performed to give a simple chart for determining the appro¬priate value of feedback gain as a function of cable length, sling length, and load parameters to provide theoretical damping ratios of 0.7. The sensitivity to parameter changes was studied, and a ±10-percent change in parameters was found to affect system performance only slightly. Implementation of the control scheme in a nonlinear simulation produced damping ratios equal to or greater than those calculated. A limited number of piloted flights in a visual simulator indicated a significant reduction in load swinging in the transition to hover, and thus the pilot was able to concentrate on load altitude and position control.