TATE, Derek (Westinghouse Way, Melksham, Wiltshire SN12 6LT, GB)
1. A control system for a platform screen door system, which platform screen door system has a door drive means and a microprocessor door drive control means adapted to control the opening and closing of the door according to a predetermined profile, the control system further comprising at least one probe adapted to monitor the drive means and/or door motion, characterised in that the control system further comprises a controller adapted to control the door drive means, wherein in use, the controller brakes the door drive means if a signal from the probe is outside a predetermined door operating envelope.
2. A control system according to claim 1 , wherein the probe is adapted to measure the speed of the door.
3. A control system according to Claim 1 or Claim 2, wherein the probe is adapted to measure the current drawn by the door drive means.
4. A control system according to any one of Claims 1 to 3, wherein once the door has reached a predetermined speed, the microprocessor is adapted to maintain the door at a constant speed for a predetermined time or distance and then to brake the door to a second predetermined speed, which second predetermined speed is lower than the first predetermined speed and wherein if the controller determines that the door speed is higher than second predetermined speed, the drive means are braked.
5. A control system according to any one of the preceding claims, wherein the probe is a Hall probe.
6. A control system according to claim 5, wherein the time between successive rising edges of the Hall probe signals is measured such that the door speed is within limit when the current drawn between successive rising edges does not exceed a predetermined limit.
7. A control system according to any one of Claims 1 to 6, wherein the door operating envelope has selectable operating boundaries for different doors.
8. A control system according to any one of the preceding claims, wherein the door is a platform screen door. |
Platform screen door
The invention relates to a control system for a platform screen door system and a method of operating the closing of the doors.
The conventional railway station consisting of a raised platform adjacent to the track is essentially the same design as has been used since the beginning of the railway industry in the nineteenth century and is an effective solution to the problem of maximising passenger boarding speed.
However, the basic platform arrangement suffers from several well known problems, such as passengers falling under trains either deliberately or unintentionally and also ■ litter from passengers falling onto the track. Although incidents of people falling under trains are not common, they result in significant disruption to the network and are traumatic incidents for everyone present. The problem of litter on the track has also increased in recent years and can represent a serious health and safety risk on underground or sub-surface systems where the litter will remain in tunnels until it is cleared up.
Platform screen door systems or automated platform gates are well known in the railway industry as one approach of dealing with these problems. Due to the problem of lining up doors on the platform and the train, these systems are usually only installed on lines where the rolling stock is standardised, which in practice is on metro or underground systems, although some dedicated high speed systems are also provided with screens.
As the doors are quite heavy, weighing in some cases over 100kg, and hence require a significant energy to move the door, the door and gate systems are usually provided with obstruction detection so that a brake can be applied in the event that someone or something becomes trapped between the leading door edge and the system in the closed and locked position. Presently installed systems use microprocessor based software control to control the motor speed in accordance with predetermined characteristic profiles, in which the final portion of the door movement is comparatively slow so that in the event that someone or something becomes trapped, lower forces are applied which will not cause serious injuries.
The known systems suffer from the problem that it is possible for the doors under microprocessor / software control to go into overspeed by overshooting the characteristic profile. Due to the nature of the injuries which could be caused by failure of the software controlling the door it has to be validated to a minimum level of SIL2.
The present invention seeks to provide apparatus and a method for controlling the closing of a door or gate in a platform screen door system that enhances the safety of the system.
According to the present invention there is provided a control system for a platform screen door system, which platform screen door system has a door drive means and a microprocessor door drive control means adapted to control the opening and closing of the door according to a predetermined profile, the control system comprising at least one probe adapted to monitor the drive means and/or door motion, the control system further comprising a controller adapted to control the door drive means, wherein in use, the controller brakes the door drive means if a signal from the probe is outside a predetermined door operating envelope.
In a preferred embodiment, the drive means comprises at least one motor driven pulley and the probe is adapted to measure the current drawn by the motor.
Preferably, the probe is adapted to measure the speed of the door and/or the current drawn by the door drive means.
Preferably, once the door has reached a predetermined speed, the microprocessor is adapted to maintain the door at a constant speed for a predetermined time or distance and then to brake the door to a second predetermined speed, which second predetermined speed is lower than the first predetermined speed and wherein if the controller determines that the door speed is higher than second predetermined speed, the drive means are braked.
Preferably, the probe is a Hall probe and the time between successive rising edges of the Hall probe signals is measured such that the door speed is within limit when the current drawn between successive rising edges does not exceed a predetermined limit.
Preferably, the door operating envelope has selectable operating boundaries for different doors.
The system of the invention has the advantage over the known systems of providing both obstruction detection and door overspeed control using independent hardware control in addition to software control thereby enhancing safety through redundancy and diversity.
An exemplary embodiment of the invention will now be described in greater detail with reference to the drawing in which:
Fig. 1 shows a platform screen door system;
Fig. 2 shows a schematic of a speed profile for closing a door.
Figure 1 shows a schematic of a platform screen door system with the sliding doors in the closed position on a railway platform comprising a first sliding door 1 , adjacent to a fixed driving panel 2, which fixed driving panel 2 is narrower than the sliding door 1. The fixed driving panel 2 is adjacent to a fixed panel 3 or the pivoting door, which in turn is adjacent to a further fixed driving panel 4, which is adjacent to a further sliding door 5. A guide 6 is provided at the lower edges of the fixed driving panels 2 and 4. A head structure 7 is provided on the upper edge of the fixed driving panels 2 and 3 and the fixed panel 3. The door system is provided with a drive mechanism comprising two pairs of motor driven pulleys and two belts fixed to opposite ends of the sliding door 1 ,5.
In known door systems, the operation of the motor is controlled by a local microprocessor which actuates the door opening when a door open signal is received from the train, typically via the track signalling system. The door movement follows a profile, which is shown schematically in Figure 2, where it can be seen that the door accelerates from rest to a first constant speed, during which time the door covers most of the distance between the open and closed positions. When the door is approaching the closed position, it is braked and the speed reduced sharply so that in the event of a passenger's head being trapped between the sliding door leafs, the force applied to the passenger is greatly reduced to thereby prevent the passenger being squeezed. The door speed is then slowly brought to zero at the point at which the door is in the closed position. Once in the closed position, the controller can lock
the door and inform the train that the doors are closed and locked so that the train may depart.
Due to safety considerations, there are two limits defined for the energy stored in the moving door leafs. A high level for a closing leaf in the section labelled A to . B in Figure 2 dropping to a much lower limit for the final closing section B to C. The microprocessor is programmed during the installation of the door system so that the door speeds will follow the speed profile shown in Figure 2 to ensure that the door does not have too much kinetic energy, which might otherwise compromise safety.
In the invention a controller in the form of a programmable array logic (PAL) is provided to monitor the door speed, door position and motor current when the door is moving. Each motor is provided with a Hall probe adapted to measure the speed of the motor and the output signal of the Hall probe is fed to the PAL. A clock and a multistage counter are provided to measure the time between successive rising edges of the Hall probe output signal with the counter being pulse by a speedclock and being reset on each rising edge of the Hall probe signal.
To ensure that safety requirements are met, it is necessary to ensure that the energy in the door movement does not exceed predefined levels throughout its travel that will not cause significant injury. As with the known microprocessor software controlled solutions, a higher level is set for most of the closing distance and a lower level is set for the final section. The energy in the door will be a function of the mass of the door and hence for a heavier door, the level of permitted door speed will be lower. These levels are set to be higher that the levels set in the profiles followed by the microprocessor so that unless there is a fault with the microprocessor, the microprocessor will continue to control the door closing. These levels are also lower than the levels which are generally recognised as being capable of causing injury.
The door speed is within the predefined safety limit when the multistage counter reaches a defined current speed limit between successive rising edges of the Hall probe signal. The status of this counter is buffered so that several cycles of over- speed running are allowed before overspeed is detected.
In the event that the PAL detects overspeed, then the door will be forced into braking mode by interrupting the power to the motors. The braking will remain in effect until the motor speed has dropped to a very low speed, the door speed will then be limited
to a low speed limit until the doors are fully closed and locked. At which point the motor can be released to revert to the normal profiles. In systems having more than one motor per door, in the event that overspeed in detected in any one of the motors then all motors will be braked.
The PAL is also adapted to be able to detect whether an obstruction is present. The PAL monitors the current being drawn by the motor at all times. The PAL determines that the motor is accelerating for a set distance whenever the door speed has either dropped to a very low speed or the direction has changed. If the current being drawn by the motor exceeds a predetermined limit, wherein a higher limit will be set for when the door is accelerating than the limit for when the door is travelling at constant speed or decelerating, it is likely that there is an obstruction in the door. If the current exceeds this predetermined limit for longer than the defined period then the motors are again braked and brought to a standstill. The PAL will then reset the door control unit and disable the motor for 10 seconds, to allow the doors to be to freed from the obstruction, before returning control to the micro.
The invention is suitable for use in both full height door systems and half height systems, in which the doors are also called gates.
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