Seamless switchover system and method
A system and method provide seamless control switchover through an input coupled to a power line and a safety apparatus that actuates if the input remains de-energized for a first time interval. Each of a plurality of subsystems has a control unit that controls a power source to energize the power line and is capable of transitioning between master and slave states. A first switch or second and third switches in series couple the power source to the power line. The first switch is closed during master state operation. The second switch is closed during slave operation and the third switch is open if any subsystem control unit is in master state. The system is configured to open or close the first switch, the second switch, or the third switch responsive to a transition of a control unit to or from master state within the first time interval.
1. A system for seamless switchover, the system comprising:
a first power line;
a safety device comprising:
a first input electrically coupled to the first power line; and
a safety apparatus, the safety device configured to actuate the safety apparatus in response to the first input being at a de-energized state for a first time interval; and
a plurality of subsystems, each subsystem comprising:
a control unit configured to be switchable between a master state and a slave state;
a first power source capable of energizing the first power line, the first power source configured to be controlled by the control unit;
a first switch electrically coupled to the first power source and to the first power line, the first switch configured to be closed while the control unit is in the master state;
a second switch electrically coupled to the first power source, the second switch configured to be closed while the control unit is in the slave state; and
a third switch electrically coupled to the second switch and to the first power line, the third switch configured to be open only while the control unit of any subsystem of the plurality of subsystems is in the master state,
the system configured to, within the first time interval, open or close the first switch, the second switch, or the third switch responsive to a transition of a control unit to or from the master state.
2. The system of claim 1 , wherein the safety device is an emergency braking system and the safety apparatus is an emergency brake.
3. The system of claim 1 , wherein the first input is an input to a relay.
4. The system of claim 1 , further comprising an active control line,
wherein the system is further configured so that a control unit in the master state energizes the control line, and
wherein each subsystem of the plurality of subsystems further comprises a switch control configured to actuate the third switch in response to the control line being energized.
5. The system of claim 1 , wherein the control unit of each subsystem of the plurality of subsystems is a vital on-board controller of a train.
6. The system of claim 1 , wherein each subsystem of the plurality of subsystems further comprises a vital supervision card configured to control output of power from the first power source based on a monitored output of the control unit.
7. The system of claim 1 , wherein the first switch and the second switch of each subsystem of the plurality of subsystems are contacts of a relay configured with an exclusive-or logic so that one contact is always closed when the other contact is open.
8. The system of claim 1 , further comprising a second power line, wherein:
the safety device further comprises a second input electrically coupled to the second power line, and the safety device is further configured to actuate the safety apparatus in response to the second input being at the de-energized state for the first time interval, and
each subsystem of the plurality of subsystems further comprises:
a second power source capable of energizing the second power line, the second power source configured to be controlled by the control unit;
a fourth switch electrically coupled to the second power source and to the second power line, the fourth switch configured to be closed while the control unit is in the master state;
a fifth switch electrically coupled to the second power source, the fifth switch configured to be closed while the control unit is in the slave state; and
a sixth switch electrically coupled to the fifth switch and to the second power line, the sixth switch configured to be open only while the control unit of any subsystem of the plurality of subsystems is in the master state, the system further configured to, within the first time interval, open or close the fourth switch, the fifth switch, or the sixth switch responsive to a transition of a control unit to or from the master state.
9. The system of claim 8 , wherein the first input and the second input are inputs to a relay and the first power source has a polarity opposite a polarity of the second power source.
10. The system of claim 1 , wherein the system is further configured so that a maximum of one control unit of a subsystem of the plurality of subsystems is in the master state at any given time.
11. A system for seamless switchover, the system comprising:
a first power line;
a safety device comprising:
a first input electrically coupled to the first power line; and
a safety apparatus, the safety device configured to actuate the safety apparatus in response to the first input being at a de-energized state for a first time interval; and
a first subsystem and a second subsystem, each of the first and second subsystems comprising:
a control unit configured to be switchable between a master state and a slave state;
a first power source communicably coupled with the control unit and configured to energize the first power line, the first power source configured to be controlled by the control unit;
a first switch electrically coupled to the first power source and to the first power line, the first switch configured to be closed during a second time interval during which the control unit is in the master state;
a second switch electrically coupled to the first power source, the second switch configured to be closed during a third time interval during which the control unit is in the slave state; and
a third switch electrically coupled to the second switch and to the first power line, the third switch configured to be open only while the control unit of the first subsystem or the control unit of the second subsystem is in the master state; and
the system configured to, within the first time interval, open or close the first switch, the second switch, or the third switch responsive to a transition of the control unit between the master state and the slave state.
12. The system of claim 11 , wherein the safety device is an emergency braking system and the safety apparatus is an emergency brake.
13. The system of claim 11 , wherein the first input is an input to a relay.
14. The system of claim 11 , further comprising an active control line,
wherein the system is further configured so that a control unit of either the first or second subsystem in the master state energizes the control line, and
wherein the first and second subsystems each further comprise a switch control configured to actuate the third switch in response to the control line being energized.
15. The system of claim 11 , wherein the control unit is a vital on-board controller of a train.
16. The system of claim 11 , wherein the first and second subsystems each further comprise a vital supervision card configured to control output of power from the first power source based on a monitored output of the control unit.
17. The system of claim 11 , wherein the first switch and the second switch of the first and second subsystems are contacts of a relay configured with an exclusive-or logic so that one contact is always closed when the other contact is open.
18. The system of claim 11 , further comprising a second power line, wherein:
the safety device further comprises a second input electrically coupled to the second power line, and the safety device is further configured to actuate the safety apparatus in response to the second input being at the de-energized state for the first time interval, and
the first and second subsystems each further comprise:
a second power source capable of energizing the second power line, the second power source configured to be controlled by the control unit;
a fourth switch electrically coupled to the second power source and to the second power line, the fourth switch configured to be closed while the control unit is in the master state;
a fifth switch electrically coupled to the second power source, the fifth switch configured to be closed while the control unit is in the slave state; and
a sixth switch electrically coupled to the fifth switch and to the second power line, the sixth switch configured to be open only while the control unit of either the first or second subsystem is in the master state, the system further configured to, within the first time interval, open or close the fourth switch, the fifth switch, or the sixth switch responsive to a transition of a control unit of either the first or second subsystem between the master state and the slave state.
19. The system of claim 18 , wherein the first input and the second input are inputs to a relay and the first power source has a polarity opposite a polarity of the second power source.
20. The system of claim 11 , wherein the system is further configured so that a maximum of one control unit of the first or second subsystem is in the master state at any given time.