A COMPUTER CONTROLLED TYPE-2 TELEMETRY TRACKING SYSTEM

Abstract

The seven WSMR Transportable Telemetry Acquisition Systems (TTAS), have served WSMR well as primary telemetry tracking systems since their acquisition over twenty years ago. Increasing maintenance demands for the original analog position control system (the antenna feed, servo power amplifiers, and position compensation) coupled with the potential for substantial tracking system performance improvement and self-diagnostic capability offered by current technology led to the establishment of a new instrumentation development task at WSMR whose objective was the development of a new, almost totally digital prototype tracking system to replace the aging analog control system in one of the TTAS’s. A modern conical scan feed has replaced the original monopulse feed, pulse-width-modulated power amplifiers have replaced the originals using SCR’s, and a VMEbus-based computer using a real-time operating system has replaced the analog compensation and overall control of the system. In this paper, following an overview of the prototype tracking system, the results of the development of a new position control algorithm for the prototype tracking system are described using root loci, computer simulation, and from the actual tracking system using servo test software developed for the computer controller. The results of the study of the old analog control system using computer simulation are presented for comparison. Problems encountered with the TTAS directly affecting position control are also presented. The new position control algorithm was designed to accommodate all of the critical tracking system nonlinearities (power amplifier saturation, current limiting, dead band, and control output saturation), all tracking modes (autotrack, manual, and using external pointing data), different operating bandwidths, and all possible drive inputs to the system. It has converted the tracking system from a type-1 to a type-2 control system improving the dynamic capability of the TTAs.