CG-1280 Rev. N 09/13 - General Dynamics SATCOM Technologies

Overview2.0 OVERVIEW OF THE 7200 ACS2.1 General Information About the 7200 ACSThe 7200 ACS is an antenna pointing system, controlled manually orautomatically, that positions the antenna to receive the peak signal from one ormore communications satellites. The 7200 ACS uses microprocessor technology toprovide accurate antenna positioning, high reliability, and maximum systemflexibility. The system has the capabilities for rapid multiple satellite access, highlysophisticated predictive tracking with inclined orbit satellites, and EIA/TIA-232E,EIA/TIA-422B, IEEE-488 (Optional) remote control communications, and 10BASE-TEthernet.In two-axis applications, azimuth (AZ) and elevation (EL) controls are used toposition the antenna. The three-axis applications use AZ, EL, and polarization (POL)controls to position the antenna and feed assembly. The four-axis applications useAZ, EL, and two polarizations (POL & 4TH AXIS) to control the position of theantenna and feed assembly. Variable speed inverters provide two-speed operationfor AZ and EL with continuously variable drive rates over a range of approximately50 to 1. The 7150 Drive Cabinet houses the drive controls and interfacingequipment to the 7200 ACS. The 7150 Drive Cabinet is normally mounted on theantenna foundation.A large 8-inch by 4-inch electro-luminescent display and a sensible, unclutteredkeypad form a user interface which is fully menu-driven and includes contextsensitivehelp messages. With much detail paid to the man-machine interface, the7200 ACU provides straightforward access to an extremely versatile ACS.The 7200 offers a number of operational modes including manual jog control,several programmed positioning modes, "conventional" steptrack, and therevolutionary Orbit Prediction Track (OPT) mode. OPT provides trackingperformance approaching that of monopulse control systems by combining efficientsteptrack operation with advanced orbital propagation algorithms to produce astate-of-the-art, predictive tracking method. With OPT, the 7200 provides highlyaccurate tracking with minimal initial data (approximately 1.25 hours for initialmodel development).Two-speed motor control is provided as standard equipment, not through the useof expensive clutched arrangements or dual-wound drive motors, but with standardthree-phase induction motors, controlled by solid-state variable frequency inverters.This approach not only provides a reliable and cost-effective means of two-speedoperation (with ratios of up to 50 to 1), but also allows for more precisepositioning than conventional Alternating Current (AC) motor control systemswhich simply use contactors to switch motor power on and off. This is a result ofthe ability of the inverter to "ramp" the motor speed up or down in a controlledmanner rather than simply removing motor power while at full speed. This canresult in uncontrollable coasting and inevitable "overshoot" of the target.2-1