Applications Using Programmable Logic Controllers精品.pdfVIP

Applications Using Programmable Logic Controllers for MARTA’s Automatic Train Control System Michael G. Cooper Metropolitan Atlanta Rapid Transit Authority 2775 East Ponce De Leon Avenue Decatur, Georgia 30030 404 848-3276 404 848-3268 (Fax) Richard W. Leslie, P.E. Regional Transit Partners P.O. Box 14 145 Atlanta, Georgia 30324 404 848-6714 404 848 6710 (Fax) H. R. Stewart Metropolitan Atlanta Rapid Transit Authority 2775 East Ponce De Leon Avenue Decatur, Georgia 30030 404 848-30 17 404 848-3268 (Fax) ABSTRACT As Metropolitan Atlanta Rapid Transit Authority’s (MARTA) automatic train control (ATC) equipment ages and operational requirements evolve, pressure is exerted upon system engineering to create innovative solutions. MARTA’s ATC maintenance department and system engineering group, in cooperation with their general engineering consultant, Regional Transit Partners (RTP), has used programmable logic controllers (PLC), at a substantial cost reduction. This cost reduction originates from using the PLC instead of relay logic. This paper will illustrate the monetary and size economies, and the ease of installation of PLCs into existing relay applications that until recently was deemed too costly to attempt with relays alone. MARTA recognized they were incurring sizable costs in time, manpower, and travel to the local train control rooms (TCR) when implementing exit prohibits. MARTA utilizes an exit prohibit to prevent train routing into work zones between interlockings, thus protecting workers on the track. The ATC department embarked on a project to control the exit prohibits remotely anywhere on the system from one of four workstations. Initial estimates revealed that use of relay equipment was impractical; therefore, MARTA explored the use of PLCs. Today, MARTA can adjust to work area