| 摘要 |
<p>Train speed is controlled by propulsion train line (PTL) apparatus, which sets a base level of propulsion effort, and by an advance train line (ATL) apparatus, which varies the propulsion effort up or down from the existing base level in accordance with under or over speed conditions. Each full cycle of ATL operation drives the PTL apparatus to the next higher or lower base level. A propulsion error signal PE drives a comparator-clock network to generate clock pulses and an up/down signal to step the ATL register and thus the PTL encoder to bring speed within the desired range. A speed control, brake error signal SCBE controls normal train braking effort but is inhibited while propulsion control remains effective to reduce speed. When the PTL encoder counts down to the zero propulsion level, the clamp on signal SCBE is removed to activate braking to further reduce speed. Station stops are controlled by a first trigger signal a preset distance in approach to the station and two subsequent triggers at shorter distances to improve the accuracy of the stop. Each trigger signal applies a scaled value of train speed and a distance-to-go indication to an acceleration computer which continually computes the deceleration rate required to stop at the station. When a comparison of the computed deceleration rate with a desired rate results in a preset ratio, the PTL encoder is driven down to zero to reduce speed in preparation for the station stopping action.</p> |
