Longitudinal control system of the intermediate capacity transit system

Abstract

To meet the Intermediate Capacity Transit System (ICTS) operational requirements driverless automatic longitudinal control is necessary. The Vehicle Control Centre (VCC) of the SELTRAC Automatic Train Control determines safe maximum velocities as a function of train position and safe stopping points for each train. These depend on the positions of trains, go slow zones, switches, stations, and other designated stopping points. Commanded braking rates are determined as a function of grade, being half maximum of 1 m/s2except for designated stopping points. The safe stopping point, maximum speed and braking rate and grade are transmitted from the VCC to each train. The Vehicle On Board Control (VOBC) on each train reports position, speed and other train information to the VCC. All computers are check redundant and all communications are protected by a redundancy code for safety. The VOBC computes braking curves for the stopping point based on a constant deceleration rate. When the train intercepts the braking curve, it goes into the constant rate deceleration mode, commanded to the speed of the braking curve as a function of its distance from the stopping point. Allowance is made in the braking curves for jerk into and out of deceleration. The Automatic Speed Control (ASC) is a closed control loop which generates motoring and regenerative braking commands to the propulsion system and blended braking commands to the disk brakes to control the train trajectories. Check-redundant tachometers and a servo accelerometer comprise the feedback elements of the ASC loop. Proportional plus integral elements provide compensation and the accelerometer provides rate feedback. The compensation and feedback elements provide close control of both transient and steady state operation. The system was developed on the TRAJCONT simulation and has been successfully tested and proven on both test and production vehicles on the Metro Canada System Test Track at Kingston, Ontario.