PRECISION LINEAR POSITION AND CONTROL FOR FLEXIBLE WALL NOZZLE

摘要

The Von Karman Facility (VKF) located at Arnold Engineering Development Complex (AEDC) consists of one supersonic wind tunnel and two hypersonic wind tunnels. Tunnel A, a supersonic tunnel, consists of a variable density two-dimensional continuous curvature nozzle and a diffuser that can be adjusted over a Mach number range from 1.5 to 5.5. The nozzle consists of two symmetrical flexible steel plates (upper and lower walls) used to set the Mach contour and two parallel steel sidewall plates that make up the process air boundary. Each flexible plate is 40 inches wide X 30 feet long and is electrically driven by 40 dual linear actuators (80 total). The nozzle can be positioned at one of eleven predetermined calibrated contours representative of the Mach range 1.5-5.5. The diffuser has a variable geometry with fixed sidewalls. The top and bottom walls are movable to match the Mach number contour of the variable nozzle. The diffuser, controlled by five actuators, consists of four hinged plates for each of the top and bottom sections. During recent efforts to modernize the Nozzle/Diffuser control system, accurate measurement of plate position with high repeatability was deemed critical. The plate position relative to the tunnel centerline was vital in achieving a desired Mach Contour. This paper will explore four aspects of this process: selection of plate position sensors; the in place plate position calibration approach based on desired plate position relative to tunnel centerline; the utilization of those sensors in the position control loop to achieve the desired contour under dynamic loads; and suggested future improvements based on lessons learned throughout the course of the modernization effort.