AUTOMATIC TARGET BRAKING IN PRAGUE UNDERGROUND

For Prague Underground, Railway Research Institute has developed the automatic target braking device. This device is dedicated for underground motor coaches series Ecs and 81, which were manufactured by Mytyschchi works in Russia. The device is able to automatize all the activities regularly performed by driver.

1. After driver's hint it switches the tape player on to warn the passengers of closing the doors.
2. After the warning it closes the doors and checks the closing. If the doors are not completely closed, it opens them and tries to close again until it succeeds.
3. When all the conditions for departure are accomplished, it switches the white lamp "Ready for departure" on.
4. The driver pushes the button "Departure". The train starts to accelerate.
5. After passing 100 meters (length of the train) the white lamp goes out and the driver can release the button. If he would release it sooner, the train starts the braking.
6. The device keeps the speed on the value required by the driver and by train control system. When the train approaches the place with interrupted power rail, the device switches the power off. After passing this place it switches the power on again.
7. The power is switched off after passing a special combination of magnets or after pushing the blue button.
8. The device controls the braking to the platform. The required deceleration depends on the fall of the track. The precission of stopping is 0.5 meter.
9. 30 m before the stopping point it switches the tape player on to advise passengers upon the station.
10. When the train stops, it opens the doors on that side where the platform is. The opening is in safe way.

The complete device is placed in the head coach. The only components placed on the track are information points consisting of permanent magnets. The combination of the magnets determinates the required function of the device. There are 15 possible combinations, seven of them are used for target braking and some for other purposes (e.g. Interrupted power rail). Info-points used for target braking are placed 500 and 98 meters before the stopping point. In shorter sections, theese distances are 350 and 98 meters.

There are big voltage peaks and great currents (over 15 A) in control circuits of the coaches and therefore the interface between the target braking device and control circuits is realized using the relays and contactors. For coaches serie 81, new contactless switches were developed.

Note: This device was in use on 18 trains (36 head vehicles) in the period from 1975 till 1995, when the Ecs vehicles finished their regular operation.