GB2539281A

GB2539281A - Object detection

Info

Publication number: GB2539281A
Application number: GB1513698.9A
Authority: GB
Inventors: Stephen Westhead Karl; Coredon Edward Griffiths Tom; Robert Hall Mark
Original assignee: Avire Ltd
Current assignee: Avire Ltd
Priority date: 2015-01-13
Filing date: 2015-08-03
Publication date: 2016-12-14
Also published as: GB201500513D0; WO2016113564A1; GB201513698D0

Abstract

A system for detecting the presence of an object 520 in a doorway 100-2, 100-2 of an elevator having a powered door comprises a radiation source 540 for transmitting at least two radiation beams 510, two or more radiation receivers 550 for receiving the radiation beams and a processor configured to detect sequential interruption of radiation received by a first and a second radiation receiver 550, indicating the presence of an object 520 in the doorway 100-2, 100-2. The object may be a narrow object such as a dog lead. Then the presence of an object 520 is detected the elevator may return to the previous floor and the doorway may be opened. An accelerometer may be used to determine the direction of motion of the elevator which may be used to determine consistency with the sequential interruption of radiation. The system may be enabled when the doors are within a predetermined separation such as substantially closed, as detected by a separation sensor 560 such as a Hall effect sensor. There may be an array of radiation sources 540, which may be LEDs, and an array of radiation receivers 550.

Description

Object detection

Field of invention

The invention relates to object detection and, in particular a system, apparatus and method for detecting objects, for example in a doorway.

Background

Powered doorways, such as those used in elevators, often include devices which prevent the door from closing on an object. The predominant technology in this field is the use of infra-red beams being directed across the doorway; if one or more of the beams are interrupted the doors stop closing and reverse so as to allow the user to enter / exit without danger of being impacted by the door.

However, these devices rely on a large number of infrared beams so as to be able to detect actions such as a user placing their arm in the path of the doors. For this reason, prior art devices have focussed on ways of increasing the effective numbers of infra-red beams that may be interrupted by an object, for example GB 2420176 in the name of Memco Limited describes a device whereby an array of transmitters transmit to a corresponding array of receivers thereby creating a 'curtain' of infra-red beams (as shown in Figure 1). However, these devices still have areas which do not contain any beams, particularly located near either door, in between the transmitters/receivers. This problem is exacerbated when the powered door is nearly closed, and the infra-red elements are therefore at a close separation, because the effective infra-red coverage is reduced as a result of the limited angle at which the infra-red radiation leaves the transmitters. In some cases, the edge device may even turn off when the door is below a certain separation because no beams can be reliably detected. This can be problematic because, if a narrow object is placed between the doors when the doors are close together, the object may be caught between the closing doors, possibly resulting in injury to a user if the object is a body part such as a hand, finger or foot.

Other systems exist which attempt to avoid the problem of doors impacting on objects by installing a mechanical device which detects when the doors impact on an object. An example device is described in US 3,627,082 titled 'Elevator door safety device' and US 2,878,898 titled 'Elevator Closure Systems' which both describe an edge device protruding in advance of the moving door that detects an object by physically moving following an impact. However, such a device may be unsuitable for small gaps because lag in the mechanism may result in injury to a user before the doors begin to reverse. -2 -

Furthermore, these systems may be unnerving for users as it requires physical contact with a door.

Another problematic scenario is where a user with a dog (such as a guide dog) enters the elevator, but the dog remains outside (or vice versa). The dog lead may be not be wide enough to interfere with any of the infrared beams, nor substantial enough to trigger a sufficient mechanical movement of a mechanical safety edge to cause door reversal. Accordingly, the elevator doors may close and the elevator depart with unfavourable consequences.

There is therefore a need for an improved object detection system.

According to one aspect there is provided a system for detecting the presence of an object in a doorway of an elevator having a powered door, the system comprising: a radiation source for transmitting at least two radiation beams; two or more radiation receivers for receiving the radiation beams transmitted by the radiation source; and a processer configured to detect sequential interruption of radiation received by a first and a second radiation receiver; wherein the processor is adapted to detect the presence of an object in the doorway when said sequential interruption of radiation received by said first and second radiation receivers is detected. Such a system allows for objects trapped in elevator doors whilst the elevator is moving to be detected.

For increased safety, the processor may be configured to trigger a safety response when an object is detected.

The safety response may be to return the elevator to the previous floor and open the powered doorway, thus allowing a trapped object to be removed safely.

The processor may be further configured to monitor the direction of motion off the elevator.

Preferably, the processor is configured to determine the direction of motion of the elevator based on information relating to the elevator's current position and destination.

Preferably, the system further comprises an accelerometer, wherein the processor is configured to determine the direction of motion of the elevator based on an acceleration detected by the accelerometer. -3 -

Preferably, an object is detected if the sequential interruption of the radiation beams is detected is consistent with the determined direction of motion of the elevator.

Preferably, the system further comprises a separation sensor for detecting the separation of the doorway; preferably wherein the separation sensor is adapted to detect when the separation of the doorway is less than a predetermined separation.

For energy efficiency and reliability, the processor may be adapted to enable the system when the powered doors are within a predetermined separation. Preferably, the predetermined distance is less than 20mm, and preferably when the doors are substantially closed.

For simplicity, the separation sensor may comprise at least one of: a Hall Effect sensor; and said radiation transmitter and said radiation receivers.

Preferably, the radiation source and radiation receiver array are affixed to opposite sides of the doorway.

Preferably, the radiation source and radiation receiver array are affixed to the same side of the doorway.

Preferably, the radiation receivers are spaced along an edge of the powered doorway.

Preferably, the first and second radiation receivers are neighbouring in the receiver array.

So as to reduce the false positive rate, the radiation source may be adapted to modulate the transmitted radiation.

Preferably, the radiation source transmits radiation in at least one of: the infra-red spectrum, and the visible spectrum. This avoids ambient light being detected and interpreted as the transmitted radiation.

According to another aspect there is provided a controller for the system as described herein, the controller comprising: a processor configured to detect when radiation received by two or more of the radiation receivers is interrupted, and to control the movement of the powered doorway in dependence on the order in which the interruptions are detected. -4 -

Preferably, the processor is further configured to control the movement of the elevator in dependence on the sequence in which the interruptions are detected.

Preferably, the controller device is operable to detect when the separation of the powered doorway is below a pre-determined distance, and controlling the movement of powered doorway in dependence on this separation.

According to another aspect there is provided an edge device comprising two or more radiation receivers, the edge device being suitable for providing a signal to the controller as described herein.

Preferably, the edge device comprises means (for example, a processor and associated memory) for signalling the interruption of each of said radiation receivers independently.

Preferably, the edge device comprises a separation sensor for detecting the separation of the doorway; preferably wherein the separation sensor is adapted to detect when the separation of the doorway is less than a predetermined separation.

According to another aspect there is provided a method of detecting the presence of an object in a doorway of an elevator having a powered door, the method comprising steps of: receiving radiation at two or more radiation receivers; and determining sequential interruption of radiation received at a first and a second radiation receiver; thereby detecting the presence of an object in the doorway.

For improved safety, the method may comprise triggering a safety response when an object is detected.

Preferably the safety response is to return the elevator to the previous floor and open the powered doorway.

Preferably, the method comprises determining the direction of motion off the elevator.

Preferably, the method comprises determining the direction of motion of the elevator based on information relating to the current position and destination of the elevator.

Preferably, the presence of an object is detected if the sequence of interruption of the radiation beams is consistent with the determined direction of motion of the elevator. -5 -

Preferably, the method comprises determining a separation of the powered doors, and detecting the presence of an object in the doorway if the separation is below a predetermined distance.

According to another aspect there is provided a system for detecting the presence of an object in a doorway having a powered door, the system comprising: a radiation transmitter adapted to direct radiation substantially along a longitudinal edge of the doorway in a direction substantially perpendicular to a direction of motion of said powered door; a radiation receiver for receiving the radiation transmitted by the radiation transmitter; a processer configured to detect interruption of said radiation by an object whereby to detect the presence of an object in the doorway. Such a system improves the safety of powered doors.

The transmitter may be adapted to direct radiation towards a reflective element at the opposing end of the doorway; and the receiver being adapted to detect the radiation reflected from said reflective element.

For simplicity of construction, the reflective element may be a sill of the doorway.

The radiation transmitter and radiation receiver may be adapted to be affixed to the same side of the doorway.

The radiation transmitter may be adapted to be affixed at one side of the doorway and the radiation receiver is adapted to be affixed at the opposing side of the doorway.

For efficiency of operation, the radiation transmitter may comprise a collimated light source.

For efficiency of manufacture and/or operation, the collimated light source may comprise a laser.

For efficiency of manufacture and/or operation, the laser may comprise a laser diode.

For efficiency of manufacture and/or operation, the collimated light source may comprise a collimated LED.

For efficiency of manufacture and/or operation, the receiver may comprise a photodiode. -6 -

In order for the transmitted radiation to be distinguishable from other radiation sources, the system may comprise a modulator to modulate the transmitted radiation.

The modulation may comprise pulsing the transmitted radiation.

For safety and/or efficiency of operation, the radiation transmitter may be adapted to transmit light in the visible spectrum.

For safety and/or efficiency of operation, the system may further comprise a separation sensor for detecting the separation of the doorway.

The separation sensor may be adapted to detect when the separation of the doorway is less than a predetermined separation.

For safety, the processor may be adapted to enable the system when the powered doors are closing and disable the system when the powered doors are opening.

For safety, the processor may be adapted to enable the system when the powered doors are within a predetermined separation, the predetermined separation preferably being 100mm, preferably 20mm.

For convenience and/or protection, the radiation receiver may be adapted to be integrated into a door safety edge device.

For convenience and/or protection, the radiation receiver may be integrated into a door safety edge device end cap for said integration into the door safety edge device door safety edge device.

For safety, the processor may be adapted to control the movement of the powered door on detection of said interruption.

In order to for the transmitted radiation to be distinguishable from other radiation sources, the processor may be adapted to discriminate between a plurality of different types of -7 -said received radiation (e.g. between background radiation and radiation received directly or indirectly from said transmitter).

The radiation transmitter may be adapted to modulate the transmitted radiation. Modulation of the transmitted radiation allows discrimination between different radiation sources.

Discriminating between a plurality of different types of said received radiation may comprise detecting the modulation of the radiation.

Discriminating between a plurality of different types of said received radiation may comprise detecting a spectral property of the radiation.

The spectral property may be a wavelength band.

The spectral property may be an intensity.

For compactness and/or convenience, the transmitter may be adapted to be integrated into a door edge and the system further comprises a radiation redirecting means adapted to be affixed to the door edge so as to redirect the transmitted radiation substantially along a longitudinal edge of the doorway in a direction substantially perpendicular to a direction of motion of said powered door.

The radiation redirecting means may be a mirror or prism.

The radiation redirecting means may be sprung so as to protrude from the door edge.

According to another aspect there is provided an edge device for a powered door, the edge device comprising a radiation transmitter for the system described herein: the radiation transmitter being adapted to direct radiation substantially along the longitudinal edge of the doorway in the direction substantially perpendicular to the direction of motion of said powered door. -8 -

The radiation transmitter may be transversely offset from the edge device. This allows for a substantially longitudinal beam offset from the door edge to be transmitted.

The transmitter may be located towards a longitudinal end of said edge device. This allows for improved coverage by the beam and therefore improved safety.

The edge device may further comprise an array of radiation transmitters adapted to transmit radiation substantially perpendicular to the longitudinal edge of the doorway. This allows for a compact edge device.

The edge device may further comprise an array of radiation receivers adapted to receive radiation from a direction substantially perpendicular to the longitudinal edge of the doorway. This allows for a compact edge device.

The edge device may further comprise a radiation receiver at the opposing end of the edge device to the radiation transmitter.

The radiation receiver may be positioned so as to face substantially away from the radiation transmitter.

According to another aspect there is provided an edge device for powered door, the edge device comprising a radiation receiver for the system as described herein: the radiation receiver being located towards a longitudinal end of said edge device and being adapted to receive the radiation transmitted by the radiation transmitter. This allows for improved coverage by the beam and therefore improved safety.

The edge device may further comprise an array of further radiation receivers adapted to receive radiation from a direction substantially perpendicular to the longitudinal edge of the edge device.

The edge device may further comprise an array of radiation transmitters adapted to transmit radiation substantially perpendicular to the longitudinal edge of the edge device.

The edge device may be adapted to be fitted to a longitudinal edge of a powered door. -9 -

According to another aspect of the present invention there is provided a controller for the system as described herein comprising said processor for detection of interruption of transmitted radiation.

According to another aspect there is provided a method of detecting the presence of an object in a doorway, the method comprising the steps of: transmitting, at a transmitter, radiation substantially along the longitudinal edge of the doorway; receiving radiation at a receiver; and controlling the movement of said doorway in dependence on said received radiation.

The invention extends to any novel aspects or features described and/or illustrated herein.

Further features of the invention are characterised by the other independent and dependent claims Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly.

Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory.

It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and/or supplied and/or used independently.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

The invention will now be disclosed with reference to the accompanying figures in which: Figure 1 shows an arrangement of radiation transmitter and receivers; Figures 2 show exemplary transmitter / receiver arrangements installed on the edges of a pair of powered doors; Figure 3 shows a flow diagram of an example object detection method; Figure 4 is a schematic diagram of an example object detection system; Figure 5 shows a further arrangement of radiation transmitters and receivers; Figure 6 is a flow diagram of a further example object detection method; and Figure 7 shows a further schematic diagram of an example object detection system.

Detailed description

Figures 1 to 4 illustrate exemplary an object detection system as described above.

In the system illustrated in Figures 1 to 4, safety is enhanced by provision of a secondary detection capability (in addition to a primary 'light curtain' system as shown in Figure 1) that is capable of detecting even the smallest of objects in a narrowing gap between the closing doors of a powered doorway (or between the door and a solid edge against which a single powered door closes).

The secondary detection capability comprises at least one additional or 'secondary' radiation transmitter provided on one side of the doorway and at least one corresponding or 'secondary' radiation receiver provided on the other. The secondary transmitter is arranged at an orientation such that radiation is directed, with a substantially vertical main beam axis, along the longitudinal edge of the doorway (albeit that the beam of radiation may be conical rather than collimated). A reflective element provided at the opposite longitudinal end of the doorway is arranged to reflect at least some of the radiation from the secondary transmitter towards a range of positions that the secondary receiver will occupy when the doors are closing and the gap between them is relatively narrow. The secondary detection capability is enabled when the gap is relatively narrow and the risk to object contact/entrapment is at its highest.

The system comprises control circuitry that detects interruption of the beam by an object, such as a finger, foot, umbrella, newspaper etc. The control circuitry is adapted to enable the system when the powered doors are closing, and to disable the system when the doors are opening so as to detect objects which are at risk of being contacted / entrapped. The control circuitry is operable to discriminate different types of signal so that the interruption of the beam can be determined and thus signal the movement of the doors to be stopped and/or reversed.

Accordingly, beneficially, the radiation transmitted along the longitudinal edge of the doorway and detected by the radiation receiver at substantially the opposite longitudinal end is broken when the gap between the doors (or the gap between a single door and a frame/slam post) is narrow and an object is placed in the gap, near the edge of that door. If the beam is detected to have been broken, a signal is sent to stop and reverse the movement of the door thereby reducing the risk of any contact between the door and the object and enhancing safety. For example, such a system allows small objects such as fingers (which may be inserted as the doors are almost completely closed) to be detected so as to avoid injury and/or damage to the door.

Figure 1 shows a primary object detection system in the form of a 'light curtain' for an elevator door created by an array of infra-red transmitters on one side 100-1 of the doorway transmitting to an array of infra-red receivers on the opposing side 100-2 of the doorway in a substantially transverse direction (indicated by arrow T). When one or more of these beams are broken (for example by a user), this is detected by a controller, which controls the movement of the elevator doors such that the doors will not close, or will reverse if they are already closing. Hence, the user can enter or exit the elevator. In this example, the array of infra-red transmitters / receivers is provided in a separate device which is retrofitted to the edges of a doorway. Such devices are commonly termed 'edge devices'. It should be appreciated that one side of the doorway 100-1, 100-2 may be a fixed edge (slam post') rather than a moving door.

Figures 2(a)-(e) show various embodiments of a further safety system which is advantageously (although not necessarily) utilised together with a 'light curtain' system as shown in Figure 1 to provide the secondary detection capability; the system in Figure 2 being operable to detect objects when the doors are separated by a small distance. In the system of Figures 2(a)-(e), a radiation transmitting device 202 is affixed towards the top of one of the doorways 100-1, orientated so as to direct a beam of radiation substantially along the longitudinal edge of the doorway (i.e. towards the bottom of the doorway 100-1, indicated by arrow L). If used alongside an infra-red light curtain device, the transmitting device 202 is preferably affixed to the same side as the edge with the transmitting array so as to avoid any cross-talk between the two separate safety systems. The radiation emitted from the radiation transmitter 202 travels along the edge of the doorway 100-1 and is incident on the sill of the doorway 110. The radiation then is reflected in a disperse fashion (as the sill 110 is not typically a smooth surface), with some radiation being -12 -reflected towards a radiation receiver device 204 affixed on towards the bottom of the doorway 100-2 (and on the opposing side of the doorway in Figure 2(b)). If the radiation receiver 204 detects radiation incident upon it, the system can determine that the beam has not been interrupted and that no object is present so the doorway can continue to close.

Figure 2(c) shows an example arrangement where both doors 100-1, 100-2 have a radiation transmitter 202-1, 202-3 and receiver 204-1, 204-3. The type of radiation and/or modulation may differ for either side so that the receivers 204-1, 204-3 can determine the source of the received radiation.

Figure 2(d) shows an example arrangement where the receiver 204-1 receives light from the transmitter 202-1 directly. Such an arrangement may require more accurate fixing and calibration than previous arrangements, but would result in a higher proportion of the transmitted radiation reaching the receiver 204-1. Figure 2(d) also shows cut-outs 203 on the opposing side of the doorway 100-2 so as to allow the doorway to close fully. It should be appreciated that the transmitter 202-1 and receiver 204-1 may not extend the entire depth of the door 100-1, so the cut-outs 203 may match the extent of the transmitter 202-1 and receiver 204-1 rather than being channels across the depth of the door 100-1.

Figure 2(e) shows another example arrangement where the transmitter 202-1 and receiver 204-1 are embedded within the doorway 100-1 and facing outwards (in a transverse direction). Mirrors or prisms 205 are positioned adjacent the transmitter 202-1 and receiver 204-1 so as to redirect (e.g. reflect or refract) the radiation from a transverse direction to a longitudinal direction, then back to a transverse direction for receipt by the radiation receiver 204-1. The mirrors or prisms 205 may be sprung so as to protrude only when the doorway is open.

The system of Figures 2(a), (c), (d) and (e) would operate in the same manner irrespective of the distance 'X' between the doors, however in order to save energy, the system may only be activated when there is a realistic possibility of an object being trapped between the closing doors or between the door and the slam post, in one example this is when X becomes less than 100mm, preferably less than 20mm. In contrast, I, the system of Figure 2(b) relies on a sufficient amount of radiation being reflected from the doorway sill 110 and becoming incident on the radiation receiver 204-2, otherwise the system may falsely determine that the beam has been interrupted by an object. For this reason, the system is only activated once the doorway is at a certain stage of closure. In one example, the system is only activated when the doors 100-1, 100-2 are within 100mm of one-another, preferably less than 20mm.

The separation 'X' in Figure 2 is in one example determined by a separation sensor 206 (described in more detail below with reference to Figure 4). In the examples shown in Figures 2(b) and (c), the role of separation sensor 206 may be provided by the radiation receiver 204-2, 204-3 receiving a sufficient level of radiation from the opposing transmitter 202-3, 202-1 reflected from the door sill 110. Receipt of a certain level of radiation from the opposing side of the door sill 110 is indicative of how close the doors are together and thus (following suitable calibration) can be utilised as a separation sensor 206.

The beam is shown in the example of Figure 2 as being approximately parallel to the longitudinal edge of the door. Here, the radiation transmitter 202 is offset from the edge of the doorway 100-1. This is so that the beam is at a likely to be interrupted before the doors have closed if an object is placed in between the doorways. In the example where the system is activated when the separation is 20mm or less, the offset may be 5mm.

The radiation beam is in the form of a collimated beam, this reduces the dispersion of the beam so that the beam is localised to the area along the doorway edge so as to be able to detect an object obstructing the doors. Having a collimated beam also means that a significant proportion of the beam is incident on the doorway sill for reflecting towards the radiation receiver (as opposed to being dispersed elsewhere), so a lower power radiation transmitter 202 may be used.

The collimation may be afforded by the radiation transmitter 202 being a laser, preferably a laser diode. In this example, the laser at a wavelength and power so as to not pose a risk to a user if they were (for example) to look directly at the radiation transmitter. A power of less than 5mW, preferably less than 1 mW would not pose a significant risk to users. The laser may be pulsed so as to save energy and pose a lower risk to users; in one example the duty cycle of the pulsing is around 50%. The wavelength of the laser should ideally not overlap with the wavelength of the infra-red light curtain (if utilised) so as to avoid cross-talk (for example, some existing infra-red light curtains use LEDs with wavelengths ranging from 850nm -950nm). Light in the visible spectrum is preferable so that an engineer can determine whether the laser is functioning correctly and is aligned correctly. Therefore, red laser light with a wavelength of 635nm is a particularly -14 -advantageous choice as laser diodes are available at this wavelength, and such lasers are inexpensive and readily available.

Alternatively, the radiation transmitter 202 may be a collimated Light Emitting Diode (LED). The collimation may be afforded by a lens / aperture, an arrangement of lenses / apertures. LEDs of varying wavelength and intensity are inexpensive, reliable and readily available. The wavelength of the LED should preferably not overlap with the wavelength of the infra-red light curtain (if utilised) so as to avoid cross-talk. Light in the visible spectrum is preferable so that an engineer can determine whether the LED is functioning correctly and is aligned correctly. Therefore, red LED light with a wavelength of 635nm is a particularly advantageous choice, and such LEDs are inexpensive, energy efficient, and readily available.

Lasers and LEDs both emit radiation with a relatively narrow waveband, so the radiation receiver 204 may differentiate this radiation from background radiation by way of a waveband filter without the loss of a significant amount of incident power (as may be the case for other light sources); this is described in more detail below. In all of the above examples, the radiation receiver 204 is chosen based on the choice of radiation transmitter 202 so as to be able to detect the specific wavelength and intensity of radiation transmitted by the radiation transmitter 202.

Using light, particularly light in the visible spectrum, opens up the possibility of radiation from the surrounding environment to be falsely detected as originating from the radiation transmitter 202. This may result in the receiver 204 detecting radiation despite the presence of an object intersecting the beam, thus the doors continuing to close on the object. To mitigate this possibility, a characteristic of the light received at the radiation receiver 204 may be determined. This determination may comprise examining at least one of the following spectral properties of the received radiation: * The intensity of the received radiation -the intensity of the received radiation must be above a pre-defined threshold for the receiver 204 to determine that the radiation originated from the transmitter 202. This intensity may be set relative to a background radiation intensity, which may be dynamically adjusted. For example, the intensity threshold is 1(t) + A where 1(t) is a time dependent background intensity and A is the amount the intensity must exceed the background intensity. An intensity threshold may always be in place in practice as the radiation receiver 204 has a lower intensity sensitivity threshold * The wavelength of the received radiation -If a specific wavelength or range of wavelengths is transmitted by the transmitter 202, the receiver 204 could be programmed so as to only respond to this particular wavelength or range of wavelengths. A wavelength filter may always be in place in practice as the radiation receiver 204 may only be able to detect radiation over a certain range of wavelengths. Such a wavelength filter may be combined with the intensity threshold as described above so as to avoid background radiation containing the appreciable power in the wavelength range. In such an example, the wavelength filter may subtract an expected (or measured) background wavelength intensity (spectrum) from a received wavelength intensity (spectrum) and apply a threshold so as to determine whether the received radiation originated from the radiation transmitter 202.

* The modulation of the received radiation -In order to differentiate the radiation from background radiation, the transmitter 202 may modulate the transmission of the radiation. The receiver 204 then determines if the specific modulation is present in the received radiation. This method can be tailored to be very resistant to influence from background radiation as background radiation is typically constant, or slowly varying. The period of modulation is chosen so that the presence of modulation can be determined in a short time period, but not so short that it is mistaken for a constant signal (if, for example, it has been contaminated with noise). A similar consideration applies to the intensity of modulation; ideally, the variance in the intensity is as large as possible, the signal varying between zero and maximum intensity. This may be achieved by 'pulsing' the radiation. An advantageous modulation range is a wave with a frequency of between 5kHz and 15kHz, preferably between 8kHz and 12kHz.

The determination of a characteristic of the light received at the radiation receiver 204 may be performed at the radiation receiver 204 or at a central control unit 208 (described in more detail below with reference to Figure 4).

As shown in Figure 2(a), the radiation receiver 204 is located towards the bottom of the doorway opposing that which the transmitter 202 is affixed. In one example, the radiation receiver 204 is incorporated within the edge of the door 100-2, preferably within the end-cap of an edge device affixed to the door 100-2. This affords the advantage of a compact system which is less likely to be damaged. Incorporating the radiation receiver 204 into the end cap allows retro-fitting of the system onto doorways already having edge devices, thereby removing the need to purchase and install a new edge device.

-16 -Figure 3 shows a flow-diagram indicating the method that the system detects an object. The method starts at step 302 when the doors begin to close. A separation sensor 206 (see Figure 4) determines whether the separation between the doors is less than X. If not, the process loops until the inequality is satisfied. Although this is shown as a loop, it may equally be a switch whereby the system is dormant until the sensor determines that the separation is less than X. This may be afforded by one of the doors 100, or the door driving mechanism, activating a switch as the doors close.

Once the system is activated, the radiation transmitter 202 starts transmitting radiation (step 306). The radiation receiver then initially determines whether it receives a signal (corresponding to the received radiation) at step 308. If no signal is detected, the system determines that an object is present and jumps to step 314. If a signal is detected, the system then must determine whether the radiation received was in fact from the radiation transmitter 202 or some other source. The received signal is analysed at step 310 to determine whether the radiation has a specified characteristic. Examples of characteristics are described above, and include: intensity, wavelength and modulation. If the detected signal is deemed not to have the specified characteristic, the system determines that an object is present and goes to step 314, otherwise the system determines that no object is detected.

If an object is detected, a signal is sent to the machinery powering the doors to stop closing (and preferably to reverse) so as to avoid contacting the detected object. As no contact with the door is made by the object (the beam being offset from the door edge), the doors have time to stop or reverse before any contact is made with the object. This may be important in powered doors where the momentum of the moving doors results in the doors continuing to close after a signal to reverse has been received, exacerbating the injury to the object / damage to the door as in prior art systems which rely on physical contact.

Figure 4 is a schematic representation of the object detection system. The system comprises a radiation receiver 202 and receiver 204, a separation sensor 206 and a control unit 208. The control unit comprises a processor 210 and associated memory 212, a sensor input module 214, a transmitter control module 216, modulator 218, receiver input module 220, demodulator 222 and output module 224.

In use, the separation sensor 206 detects that the doors are less than a certain separation and sends a signal to the sensor input module 214 within the control unit 208.

This processor 210 then determines whether further action is necessary (for example, comparing the separation received from the separation sensor to a stored separation in memory 212). If the processor 210 determines that the transmitter 202 should be activated, it sends a signal to the transmitter control module 216 which prepares a signal to be emitted by the transmitter 202. This signal is then modulated by modulator 218 prior to being passed to the transmitter 202. In one example, the modulator 218 is adapted to modulate power supplied to the transmitter 204 thereby modulating the signal transmitted therefrom. In a simple example corresponding to 'pulsed' modulation, the modulator is effectively a switch whereby the power supplied to the transmitter 202 is switched on and off.

Radiation is received by the radiation receiver 204, some of which being from the radiation transmitter 202 if no object 226 is present. The signal produced by the radiation receiver in response to receiving radiation (for example, a data signal) is passed to the control unit 204 via receiver input module 220 for determination of the source. The characteristics of the signal are then investigated (as described above with reference to Figure 3), for example the processor 210 may determine that the received signal has an intensity below a predetermined threshold (stored in memory 212) and signal that an object 226 is present. Following this, or at the same time, the signal is passed to a demodulator 222 to determine the modulation of the signal. The demodulator 222 (with assistance from processor 210) determines the period of modulation of the received signal and compares this to the transmitted modulation stored in memory 212. If the modulation is not within a predetermined range of the transmitted modulation, the system indicates that an object 226 is present.

The control unit 208 comprises an output unit 224 which is adapted to communicate with the machinery powering the doors to stop closing (and preferably to reverse) so as to avoid contacting the detected object. This may be via a separate control unit (not shown) which is concemed with the opening and closing of the doors, or the functionality may be incorporated into a single control unit. In one example, the present system is provided as a retro-fit to an existing doorway system, so the output unit 224 is adapted to communicate to the existing control unit.

The memory 212 may be hard-coded with the various thresholds and system settings, or they may be programmable by a user so as to calibrate the system according to a set of specifications (for example, the door may be in a particularly light / dark area so intensity thresholds may need to be adjusted). In the former example, the processor and memory may be provided by an Application Specific Integrated Circuit (ASIC) and in the latter, they may be provided in the form of a Field Programmable Gate Array (FGPA) or other Complex Programmable Logic Device (CPLD).

Alternatives and modifications Various other modifications will be apparent to those skilled in the art, for example the radiation transmitter 202 is illustrated in Figure 2 as being at towards the top of the doorway 100-1 and the receiver 204 at the bottom, whereas the orientation could be reversed (i.e. the transmitter 202 is located towards the bottom and the receiver 204 towards the top). In such an example, the radiation would reflect off the header of the doorway as opposed to the sill 110.

Alternatively, the radiation transmitter and/or receiver may be provided in a fixed location with respect to the closing door(s). The system is activated when the doors are below a threshold separation as before. Such an arrangement may be simpler, but may afford less safety.

In an alternative example, the radiation beam transmitted by the radiation transmitter 202 may be angled slightly away from the edge of the doorway 100-1 so that an angle is created to reflect the beam towards the radiation receiver 204 (i.e. the beam may have a small transverse component). If the angle is too great, the beam will be intercepted by the opposing door 100-2 before the door is fully closed, which may be interpreted as an object being present (or effectively stop the system from detecting objects when the separation of the doors is less than a certain amount). In an example where objects are required to be detected with the doors 10mm apart, the angle is less than tan-1(10mm/H) where H is the height of the transmitter above the door sill. If H = 2m (2000mm), the maximum angle is therefore approximately 0.005 radians (0.29 degrees).

It should be appreciated that any of the arrangements of Figures 2(a)-(e) may be combined in any appropriate manner. For example, Figure 2(e) may incorporate the cutouts 203 of Figure 2(d) rather than the mirrors or prisms 205 being sprung (or vice versa).

Example of suitable 'separation sensors' 206 described above include switches and the existing radiation detector, but also include information from the infra-red light curtain, magnetic sensors, and infra-red proximity sensors.

In one example, a separation sensor 206 is not required at all, the system being activated for the duration that the doors are closing.

In a simple example, the radiation transmitter 202 is on substantially all the time, and the radiation receiver 202 detects the presence or absence of the signal (following appropriate filtering of ambient radiation). A permanent (or adjustable) trigger threshold is set which determines whether or not an object is obstructing the doorway.

It should be appreciated that in the processor 210 may be either a signal processor or a microprocessor, or both (and potentially within a single component). The processor may comprise an electronic circuit in which a signal is generated (or terminated) when the beam is interrupted whereby to effectively detect the interruption.

In the examples described above, the radiation reflects off the door sill 110, but in alternative examples a reflective element may be provided. The reflective element may comprise a reflective strip placed on the sill 110, or an angled reflective element affixed to towards the bottom of the doorway 100-1, angled so as to direct the radiation towards the radiation receiver. Such a reflective element may be incorporated into an edge device on the doorway, for example, it may be incorporated into an end-cap of the edge device. This arrangement may remove the necessity to calibrate the system so as to account for door sills 110 having a different albedo (reflection coefficient) or where the sill 110 is not suitably shaped to reflect the light towards the opposing door 100-2.

In another example, the radiation receiver 204 is positioned on the same edge as the radiation transmitter 202, and is adapted to detect radiation received directly from the radiation transmitter 202. Such an arrangement results in a simpler device as all the componentry can be affixed to one edge device, and the system would require less calibration as there is no reflection of the beam which may be affected by differing albedos of various door sills 110. However, this arrangement may be prone to errors due to the radiation receiver 204 facing upwards (and transversely offset from the door edge), meaning that it may be more susceptible to background radiation, damage and dirt. Furthermore, the radiation beam may reflect off the door edge and reach the receiver 204 even when an object obstructs the main beam path. This would be particularly relevant if the beam is not well collimated and/or the object interrupts the beam at a significant distance from the radiation transmitter 202. Requiring the radiation beam to reflect off a reflective element (such as the door sill 110) restricts the number of optical paths the beam can take and still reach the receiver essentially down to a single path, meaning that any obstruction of this path results in an object being detected.

Trapped obiect detection The above described system is effective at detecting objects above a certain width between the closing doors. However, narrow objects (for example a dog lead) may not be detected by the system, and become trapped between the doors with unfortunate consequences, especially in elevators. An additional system is therefore needed that can detect narrow objects. An example of such an additional system is illustrated in Figures 5-6.

Figure 5 shows an example of a further object detection system, operable for the detection of narrow objects 520 when the doors are closed. An array of radiation transmitting devices 540 are fixed to one side of the doorway 100-1, which transmit radiation beams 510 in a substantially transverse direction to an array of receiving devices 550 on the opposing side of the doorway 100-2. In one example, the radiation transmitters 540 and receivers 550 are fixed to the inner set of doors (i.e. the set that move with the elevator) in order to avoid the need to have separate arrays of transmitters and receivers on each floor that the elevator stops at.

A narrow object 520, for example a 'dog lead', may be located between the doors when they close. Due to its small size, it may not have been detected by any other detection systems present, and will therefore become trapped between the two sides of the doorway. At this point the object may not interrupt any of the radiation beams 510. As the elevator begins to move upwards or downwards on its journey, its direction of motion is detected by control circuitry. The object will move relative to the elevator, being dragged either upwards or downwards, and in doing so interrupt consecutive beams 510 in a manner consistent with the elevator's motion. The sequence of interruption of each of these beams is detected by the control circuitry via the radiation receiver corresponding to the interrupted beam. If the sequence in which the beams are interrupted is consistent with the direction of the elevator's motion, then the control circuitry registers the presence of an object, and activates a safety procedure and/or response. If no object is detected the elevator continues its journey as usual.

It is not necessary that the interrupted beams be detected in a consecutive sequence; for resilience, it is only necessary that the second (and possibly subsequent) detections occur in a position consistent with the motion of the elevator.

-21 -For example, when the elevator starts to move in the upward direction, the control circuitry will detect and record its direction of motion. The object moves downwards relative to the elevator and intersect a first beam and the interruption of this beam will be detected and recorded by the system. As the elevator continues to move upwards with the object, the object will intersect a second beams lower down in the array, usually starting with the one immediately below the first. The order in which the beams are intersected is determined by the control circuitry, and compared to the detected direction of motion.

If an object is detected by the system in this way, then the control circuitry initiates a safety procedure. This comprises outputting a control signal instructing the elevator to stop, then return to the previous floor and then open its doors, allowing the narrow object to be freed.

It should be appreciated that the radiation receivers 550 may alternatively be located on the same side of the doorway 100-1 as the radiation transmitters 540, with a reflecting surface on the opposing side of the doorway 100-2, such that the transmitted radiation beams 510 are reflected off on the doorway 100-2 towards the corresponding receivers.

The radiation transmitters 540 may be provided by LEDs, since these transmit radiation in a relatively narrow waveband. They are also inexpensive, reliable and readily available. The transmitted radiation can be in the infra-red spectrum, which is advantageous if the object detection system is integrated with an infra-red light curtain system, or can be in the visible spectrum, which may be possible since very little visible light will be present between the doors when substantially closed, making it easier to determine when the transmitted light is present. The radiation receiver array 540 may be provided by photodiodes. Those skilled in the art will appreciate that the radiation may be provided by means other than an array of transmitters. For example, a single radiation source may be provided that transmits radiation a substantially longitudinal direction along doorway 100-2, with a series of half-silvered mirrors used to direct the beam towards the receiver array 550. Alternatively, a single radiation source may be used. Many other examples are possible.

The system may additionally comprise a separation sensor 560 operable to detect when the separation of the doors, X, is within a pre-determined distance. The separation sensor may, for example, be provided by the radiation receiver array itself, or by a Hall Effect sensor located on the edge of the doors. In one example, the system is configured -22 -to only activate once the separation is within this pre-set distance, preferably below 20mm, and preferably when the doors are substantially cl. This removes the need to have the system on all the time, decreasing its energy use, and allowing the components of the system (such as the radiation transmitters and receivers) to be used for other purposes when the doors are not almost fully closed.

The array of radiation transmitters 510 and detectors 550 may comprise part of the 'light curtain' detection system of Figure 1, with the further detection system of Figure 5 only being activated when the separation between the doors is within some pre-set distance, preferably one below which the light curtain's effectiveness is reduced. The system of Figure 5 can therefore be referred to as the 'high sensitivity' mode of the overall detection system.

The system also comprises control circuitry, adapted to enable the system to be activated when the separation between the doors is below a pre-set distance and to monitor the direction of motion of the elevator. The future and/or current direction of motion of the elevator may be monitored by using information about the current location of the elevator and its destination. For example, if the current floor that the elevator is on is below the destination floor, then control circuitry will determine that the elevator will be moving in an upwards direction. Alternatively, the system may further comprise an accelerometer, which can be used to determine the direction of motion of the elevator by detecting the direction of its initial acceleration when it starts moving from rest.

The control circuitry is also operable to distinguish between signals received from different radiation receivers in the array 540 in order to determine which, if any, of the radiation beams 510 have been interrupted by an object.

In another example, the movement of the elevator is not used, rather if two or more beams are interrupted, it is assumed that the elevator is moving and a safety procedure is initiated.

In one example, there may be a greater density of radiation receivers at the bottom portion of the edge device, this is because this area is likely to be more prone to interruption by a dog lead; the higher the density of receivers, the faster the system can detect and react to an object becoming trapped.

Figure 6 shows a flow diagram indicating an example method the system of Figure 5 uses to detect narrow objects trapped in the closed doors. At step 610 the doors begin to close. When the separation of the doors is detected to be within some pre-set limit 'X' 620, and the control circuitry determines that upward or downwards motion of the elevator is expected 630, the detection system is activated and enters high sensitivity mode 640. The presence of an object trapped between the doors is detected by the interruption of beams in an order consistent with the detected/anticipated motion 650. For example, if the elevator was moving in an upward direction and beams were interrupted in a downward sequence, then the system would register this as the presence of an object between the closed doors 660. This triggers a response retuming the elevator to the previous floor (i.e. the floor it had just departed) and causing the doors to open once that floor is reached. If no object is detected 670, then the elevator continues its journey as usual.

Figure 7 is a schematic representation of the object detection system of Figure 5. The system comprises a radiation transmitter 540-1 and at least two radiation receivers 550, and a control unit 708. The control unit comprises a processor 710 and associated memory 712, a sensor input module 714, a transmitter control module 716, modulator 718, receiver input module 720, demodulator 722 and output module 724. It may optionally comprise an accelerometer 728, a separation sensor 560 and/or further radiation transmitters 540-2, which can be arranged in an array.

In use, the system enters a 'high sensitivity mode' when the doors are either closed or are separated by less than a specific distance. Such a state may be triggered upon receipt of a 'door closed' signal from the controller (e.g. the elevator is preparing to move), or from a sensor such as a separation sensor 560, In the latter case, the separation sensor 560 detects that the doors are less than a certain separation and sends a signal to the sensor input module 714 within the control unit 708.

In a simple example, the high sensitivity mode is entered whenever the elevator doors are closed, or below a certain separation. Alternatively the processor 710 may determine if the elevator is, or is expected to be, in motion, and optionally the direction of that motion prior to entering the high sensitivity mode. Such an additional stage may reduce the energy consumption of the system. Detecting motion of the elevator may be by either (or both) monitoring the current and destination floors of the elevator, or by detecting the initial acceleration of the elevator of it departs a floor using accelerometer 728. This direction is stored in the memory 712.

-24 -If the processor 710 detects that the doors are less than a certain separation, and optionally that the elevator is or will be in motion, then it determines that the system should enter 'high sensitivity' mode 640. A signal is sent to the transmitter control 716, which prepares a signal to be output by the transmitters 540. This signal may be modulated by the modulator 716 prior to transmission so as to distinguish the signal from background radiation. The modulation can involve varying the intensity of the transmitted radiation. In one example this can be simply switching the radiation transmission on and off at a predetermined frequency.

The transmitted radiation is received by the radiation receivers 550 if no object is present to block the radiation beams. However, other radiation, such as background radiation may be present and received by the receivers. In order to determine if the transmitted radiation has been blocked, the signal from each of the radiation receivers 550 is passed to the control unit 708, via a receiver input module 720. The signal is then demodulated to determine whether the received signal contains the signal transmitted by the radiation transmitters 540. If no signal has been received, or if the modulation is not within a predetermined range of the transmitted modulation, the system indicates that the beam has been interrupted. Other characteristics of the signal can also be investigated, for example the processor 710 may determine that the received signal has an intensity below a predetermined threshold (stored in memory 712) and signal that the beam is interrupted. If multiple beams are detected to be interrupted then the order in which they are interrupted is compared by the processor 710 with the direction of the elevator's motion stored in the memory 712 and, if the order is consistent with an object being dragged through the transmitted radiation by the elevator, then the system indicates that an object is present. The processor may also determine the time between consecutive beam interruptions to determine whether the pattern of interruptions is consistent with an object being between the elevator doors.

The control unit 708 comprises an output unit 724 which is adapted to communicate with the machinery controlling the elevator and the machinery powering the doors, in order, upon detection of an object between the doors, to control the elevator to return to the floor it had just departed and open the doors. This may be via separate control units (not shown) which are concerned with elevator control and the opening and closing of the doors respectively, or the functionality may be incorporated into a single control unit. In one example, the present system is provided as a retro-fit to an existing doorway system, so the output unit 724 is adapted to communicate to the existing control unit.

The memory 712 may be hard-coded with the various thresholds and system settings, or they may be programmable by a user so as to calibrate the system according to a set of specifications (for example, the door may be in a particularly light / dark area so intensity thresholds may need to be adjusted). In the former example, the processor and memory may be provided by an Application Specific Integrated Circuit (ASIC) and in the latter, they may be provided in the form of a Field Programmable Gate Array (FGPA) or other Complex Programmable Logic Device (CPLD).

Individual components of the above system may be combined into an edge device for installation into a powered doorway. For example, the radiation receivers, control circuitry and separation sensor may all form a single edge device, which can easier to install into a powered doorway than individual components. In embodiments where the radiation source is located on the same side of the doorway as the radiation receiver array, the radiation source may also form part of the edge device.

The examples described above state that the modulation of the radiation is 'pulsed', but modulation may equally be afforded by way of a sine wave, square wave, triangle wave or other amplitude, frequency or phase modulation.

The above examples describe the object detection system advantageously being used alongside an infra-red 'curtain' so as to be able to detect objects when the doorway is at both large and small separations. It will be appreciated that the object detection system may also be used alongside other object detection systems such as physical detectors (as described in the background section), visible light detectors; or equally it may be used on its own.

The terms 'receiver' and 'detector' used herein are interchangeable.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

-26 -Claims 1. A system for detecting the presence of an object in a doorway of an elevator having a powered door, the system comprising: a radiation source for transmitting at least two radiation beams; two or more radiation receivers for receiving the radiation beams transmitted by the radiation source; and a processer configured to detect sequential interruption of radiation received by a first and a second radiation receiver; wherein the processor is adapted to detect the presence of an object in the doorway when said sequential interruption of radiation received by said first and second radiation receivers is detected.
2. A system according to claim 1 wherein the processor is configured to trigger a safety response when an object is detected.
3. A system according to claim 2, wherein the safety response is to return the elevator to the previous floor and open the powered doorway.
4. A system according to any preceding claim, wherein the processor is further configured to determine the direction of motion of the elevator.
5. A system according to claim 4, wherein the processor is configured to determine the direction of motion of the elevator based on information relating to the elevator's current position and destination.
6. A system according to claim 4, further comprising an accelerometer, wherein the processor is configured to determine the direction of motion of the elevator based on an acceleration detected by the accelerometer.
7. A system according to any of claims claim 4 to 6 wherein an object is detected if the sequential interruption of the radiation beams is detected is consistent with the determined direction of motion of the elevator.
8. A system according to any preceding claim, further comprising a separation sensor for detecting the separation of the doorway; preferably wherein the separation sensor is adapted to detect when the separation of the doorway is less than a predetermined separation.
9. A system according to claim 8, wherein the processor is adapted to enable the system when the powered doors are within a predetermined separation.
10. A system according to claims 8 or 9, wherein the predetermined distance is less than 20mm, and preferably when the doors are substantially closed.
11. A system according to any of claims 8 to 10, wherein the separation sensor comprises at least one of: a Hall Effect sensor; and said radiation transmitter and said radiation receivers.
12. A system according to any preceding claim, wherein the radiation source and radiation receiver array are affixed to opposite sides of the doorway.
13. A system according to any of claims 1 to 11, wherein the radiation source and radiation receiver array are affixed to the same side of the doorway.
14. A system according to any preceding claim, wherein the radiation receivers are spaced along an edge of the powered doorway.
15. A system according to any preceding claim, wherein the first and second radiation receivers are neighbouring in the receiver array.
16. A system according to any preceding claim wherein the radiation source is adapted to modulate the transmitted radiation.
17. A system according to any preceding claim, wherein the radiation source transmits radiation in at least one of: the infra-red spectrum, and the visible spectrum.
18. A controller for the system of any preceding claim, the controller comprising: a processor configured to detect when radiation received by two or more of the radiation receivers is interrupted, and to control the movement of the powered doorway in dependence on the order in which the interruptions are detected.
19. A controller according to claim 18 wherein the processor is further configured to control the movement of the elevator in dependence on the sequence in which the interruptions are detected.
20. A controller device according to claims 18 or 19 being operable to detect when the separation of the powered doorway is below a pre-determined distance, and controlling the movement of powered doorway in dependence on this separation.

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21. An edge device comprising two or more radiation receivers, the edge device being suitable for providing a signal to the controller of any of claims 18 to 20.
22. An edge device according to claim 21 comprising means for signalling the interruption of each of said radiation receivers independently.
23. An edge device according to claim 21 or 22 comprising a separation sensor for detecting the separation of the doorway; preferably wherein the separation sensor is adapted to detect when the separation of the doorway is less than a predetermined separation.
24. A method of detecting the presence of an object in a doorway of an elevator having a powered door, the method comprising steps of: receiving radiation at two or more radiation receivers; and determining sequential interruption of radiation received at a first and a second radiation receiver; thereby detecting the presence of an object in the doorway.
25. A method according to claim 24 comprising triggering a safety response when an object is detected.
26. A system according to claim 25, wherein the safety response is to retum the elevator to the previous floor and open the powered doorway.
27. A method according to any of claims 24 to 26, comprising determining the direction of motion off the elevator.
28. A method according to claim 27, comprising determining the direction of motion of the elevator based on information relating to the current position and destination of the elevator.
29. A method according to claims 27 or 28 wherein the presence of an object is detected if the sequence of interruption of the radiation beams is consistent with the determined direction of motion of the elevator.
30. A method according to any of claims 24 to 29 comprising determining a separation of the powered doors, and detecting the presence of an object in the doorway if the separation is below a predetermined distance.
31. A system substantially as described herein and/or as illustrated by accompanying Figures 5, 6 or 7.

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32. An apparatus substantially as described herein and/or as illustrated by accompanying Figures 5, 6 or 7.
33. A method substantially as described herein and/or as illustrated by accompanying Figures 5, 6 or 7.