EP0726553A1 - Indicateur avec détection de défauts - Google Patents

Indicateur avec détection de défauts Download PDF

Info

Publication number
EP0726553A1
EP0726553A1 EP96300682A EP96300682A EP0726553A1 EP 0726553 A1 EP0726553 A1 EP 0726553A1 EP 96300682 A EP96300682 A EP 96300682A EP 96300682 A EP96300682 A EP 96300682A EP 0726553 A1 EP0726553 A1 EP 0726553A1
Authority
EP
European Patent Office
Prior art keywords
lane
indicator
light source
light
photodetector
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96300682A
Other languages
German (de)
English (en)
Inventor
John M. Ironside
Russell Weilson-Jones
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ZF International UK Ltd
Original Assignee
Lucas Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lucas Industries Ltd filed Critical Lucas Industries Ltd
Publication of EP0726553A1 publication Critical patent/EP0726553A1/fr
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/10—Monitoring of the annunciator circuits

Definitions

  • the present invention relates to an indicator having fault detection.
  • Such an indicator is suitable for use as a display in safety critical systems and/or for warning of the presence of a fault.
  • a malfunction indicator light is used to indicate to an operator that a fault has been detected in an electronic controller, a sensor, an actuator, or a part or parts of the vehicle monitored or influenced by the control system.
  • a malfunction indicator light may indicate that only one sub-system of a redundant pair remains available. Upon illumination of the malfunction indicator light, the driver ought to investigate the problem and, if appropriate, continue driving but at a reduced speed.
  • malfunction indicator lights are functioning properly. It is customary to have a malfunction indicator light lamp-test facility in order to check the operation of the malfunction indicator lamps. This is usually initiated during the starting sequence of the vehicle and causes all of the malfunction indicator lights to be switched on so that the operator has an opportunity to note whether they are lit or not. However, it is believed that in many cases users do not notice when a malfunction indicator light has failed to illuminate. This may occur because the users do not recollect exactly which malfunction indicator lights should be lit, or because they do not pay attention to the control panel during the test sequence.
  • DE-A-3 630 372 discloses a light emitting diode having a built in photodetector for monitoring the operation of the light emitting diode.
  • the photodetector is located behind a filter selected such that the photodetector is only sensitive to light having a wavelength similar to the wavelength emitted by the light emitting diode.
  • a further filter is provided around the periphery of the light emitting diode so as to screen ambient light from the photodetector.
  • an indicator as defined in the appended Claim 1.
  • an indicator having fault detection comprising at least first and second lanes, each lane comprising a lane controller, at least one light source and at least one photodetector responsive to light produced by a light source of the or at least one other lane, each of the controllers being arranged to cooperate in an indicator test sequence in which each controller operates its respective at least one light source in a predetermined pattern, monitors the output of its respective photodetector to determine the output of the or at least one other lane, compares the output of the or at least one other lane with the predetermined pattern and indicates a result of the comparison.
  • Each light source may be an incandescent filament lamp, but preferably each light source is a light emitting diode (LED).
  • LEDs generally have longer lives than filament lamps and also tend to suffer a gradual degradation in performance rather than a catastrophic failure.
  • LEDs are light sensitive and a non-illuminated LED can be used as a photodetector.
  • each LED can act both as a light source and as a photodetector.
  • the photo-current induced within a single LED within a Hewlett-Packard HLMP 2685 GaAsP LED light bar due to light emanating from a neighbouring LED operating at full power is easily measured.
  • the photo-current is, however, about one hundred times less than the photocurrent induced by exposure of the device to sun light.
  • the current due to a neighbouring LED can be distinguished from the current induced by ambient illumination so as to confirm the correct operation of the LEDs. Furthermore, this device is not optimised for optical cross-coupling between neighbouring LEDs so further signal strength improvements are attainable due to improvements in optical coupling.
  • the controllers of the at least first and second lanes may be implemented independently of one another. Alternatively, the controllers of one or more lanes may be implemented within a single controller unit.
  • the light sources are arranged such that most of the light emitted by each source is directed towards a viewing region, i.e. where an operator is expected to be positioned. However, a portion of the light emitted from each light source is arranged to be incident on at least a photodetector of the or at least one other lane.
  • the controllers are arranged such that the or each light source in each lane is actuated in turn. Preferably when the or each light source of one lane is actuated, the or each light source of the or each other lane is not actuated. If the controller of one lane suspects that the or any of the lanes that it is monitoring are faulty, the controller may send a "fail" signal and/or may enter a warning mode so as to indicate to the user that a fault has been detected within the indicator. The warning mode may be indicated by a low frequency flashing of the light source of the lane signalling a fault.
  • the test sequence is initiated at vehicle start up.
  • the indicator comprises two lanes, each of which has a controller arranged to control a respective LED and uses its LED to monitor the operation of the other lane.
  • the first lane compares a measurement of the illumination arriving at its LED in a first period when the LED of the second lane is unilluminated with the illumination arriving at its LED in a second period when the LED of the second lane is illuminated.
  • the first and second periods are of equal duration. The comparison reveals whether or not the second LED was illuminated and sufficiently bright in the second period.
  • the first period represents a measurement of the ambient light
  • the second period represents a measurement of the sum of the ambient light and the light produced by the second LED.
  • a measurement of ambient light in a third period following the expiry of the second period may also be made to improve the measurement of the ambient light level.
  • the LEDs acting as photodetectors respond more quickly to changes in illumination than does the human eye. Consequently, when the ambient light is provided by an artificial light source such as a street light or a cabin light, the measurement of ambient light made by the LED may vary, for example, due to the source of ambient light being driven from an alternating power supply, while the human eye may observe a constant ambient light level.
  • the indicator test function can be made substantially immune to repetitive variations in the ambient light by making repeated measurements and actuating the LED under test with a repetition frequency which is not a multiple of the power supply frequency used to drive the ambient light source.
  • the mains frequencies in the USA and the European countries are either 50 Hz or 60 Hz.
  • a convenient repetition frequency for driving the LED in each lane is 270 Hz as this is not a multiple of 50 or 60Hz.
  • each controller may communicate with each other via a dedicated communications link so as to maintain synchronism.
  • each controller may be electrically isolated from each other controller and one controller may be arranged to act as a master and the or each other controller may be arranged to optically monitor the operation of the master controller and to maintain synchronism with it.
  • the controllers may also be arranged to perform intermittent tests at times other than during a vehicle start-up sequence.
  • the controllers may be arranged to operate their respective light sources with only a small duty cycle such that the illumination generated by each light source is substantially imperceptible to the human eye during the test sequence.
  • the indicator illustrated in Figure 1 has an indicator element 2 containing first and second LEDs 4 and 6, respectively, and first and second photodetectors 8 and 10, respectively.
  • the indicator 2 is controlled by a controller 12 which is divided into first and second lanes.
  • the first LED 4 and the first photodetector 8 are connected to the first lane whereas the second LED 6 and the second photodetector 10 are connected to the second lane.
  • the first photodetector 8 is arranged to receive light emitted by the second LED 6 and the second photodetector 10 is arranged to receive light emitted by the first LED 4.
  • the LEDs may be arranged to become illuminated to signal the same fault condition or they may signal different fault conditions and appear to the user to be separate indicators.
  • the controller 12 is responsive to a test enable signal, TESTEN, to perform a test sequence.
  • the test enable signal is asserted during a vehicle start up sequence of the vehicle having the indicator, or when manually invoked by the operator.
  • Figure 2 shows an indicator 2 in which a first light emitting diode 4 is controlled by a first controller 20, and a second light emitting diode 6 is controlled by a second controller 22.
  • the first and second controllers 20 and 22 are responsive to a test enable signal TESTEN in order to commence a test sequence.
  • the first LED 4 is also arranged to act as a photodetector during those periods when it is not acting as a light source.
  • the second LED 6 is also arranged to act as a photodetector when not being used as a light source.
  • the first and second controllers 20 and 22 may be synchronized via an electrical connection (not shown) or optically via the LEDs 4 and 6 as will be described hereinafter.
  • FIG 3 schematically illustrates a sequence of operation of the embodiments as shown in Figure 1 or Figure 2.
  • each controller cyclically repeats a test pattern comprising four equal periods P1 to P4.
  • the test pattern repetition frequency is 270 Hz, and each period lasts 1/1080 seconds.
  • the light source 4 of the first lane is illuminated during each first period P1.
  • the light source 6 of the second lane is illuminated during each third period P3.
  • the photodetector 8 of the first lane which can be the LED 4 in the embodiment shown in Figure 2, measures the light incident on it during the second to fourth periods P2-P4.
  • the second photodetector 10 which can be the LED 6 in the embodiment as shown in Figure 2, measures the light incident on it in the periods P4, P1 and P2.
  • the measurements of light made by the first photodetector 8, 4 during the second to fourth periods are indicated by ⁇ 12 , ⁇ 13 and ⁇ 14 , respectively.
  • the measurements of the light incident on the second photodetector 10, 6 during the periods P4, P1 and P2 are denoted by ⁇ 24 , ⁇ 21 and ⁇ 22 , respectively.
  • the measurements ⁇ 12 and ⁇ 14 are measurements of the ambient lighting levels
  • ⁇ 13 is the measurement of the sum of the ambient lighting level and the light arriving at the first photodetector from the second light source 6.
  • the light emitted from the second light source 6 can be deduced by subtracting ⁇ 12 from ⁇ 13 .
  • the light emitted from the second source can be calculated by finding the difference between ⁇ 13 and the average of ⁇ 12 and ⁇ 14 .
  • Each measurement ⁇ 12 to ⁇ 14 may comprise an average of a plurality of measurements in a sampled data processing system, or may be an average or an integral formed in an analogue processing element having a low pass or integrating transfer function.
  • FIG. 4 schematically illustrates a processing circuit within each controller 12, 20, 22 for estimating the amount of light produced by the light source of the other lane.
  • the circuit will be described as implemented in the first controller 20, but the corresponding circuit in the other controller is identical except that it receives different input data.
  • the circuit comprises a first summer 30 which sums the values ⁇ 12 and ⁇ 14 to form a sum of the ambient light during the second and fourth periods P2 and P4.
  • An output of the first summer 30 is provided to an input of a divide by two stage 32.
  • An output of the divide by two stage 32 is provided to a subtracting input of a second summer 34.
  • An adding input of the second summer 34 receives the value ⁇ 13 .
  • An output of the second summer 34 which represents the light produced by the LED 6, is provided to an input of an averaging element 36.
  • the averaging element 36 forms an average of the measurements conducted over a plurality of cycles so as to improve the reliability of the test.
  • An output of the averaging element 36 is provided to an inverting input of a comparator 38.
  • a reference value 40 is provided to the non-inverting input of the comparator 38. If the average value of the measured light output of the second light source 6 is greater than the reference value, the output of the comparator 38 remains "low” (Logic 0) signalling that the second light source 6 is functioning correctly. Otherwise, the comparator 38 signals that a fault has occurred in lane 2.
  • FIG. 5 schematically illustrates the first lane controller 20 of Figure 2 in greater detail.
  • the LED 4 is connected to a power supply 50 via a current limiting resistor 52 and an electronically controllable two-pole two-way ganged switch 54.
  • the switch 54 is switchable between a first position, as illustrated in Figure 5, in which the anode of the LED 4 is connected to the supply 50 via the resistor 52 and the cathode of the LED 4 is connected to ground, and a second mode in which the anode of the LED 4 is connected to ground and the cathode of the LED 4 is connected to an input of a charge amplifier 56.
  • a monitoring and control circuit 58 controls the operation of the switch 54 and the charge amplifier 56.
  • the circuit 58 also monitors the voltage of the supply to the LED 4.
  • the circuit 58 switches the switch 54 to the position shown in Figure 5 to illuminate the LED 4 during the first periods P1.
  • the switch 54 is switched to its other position during the periods P2 to P4 so that the LED 4 is not illuminated and can be used as a photodetector. Light falling on the LED 4 causes a photo-current to be induced therein.
  • the photo current is amplified and integrated by the charge amplifier 56.
  • the output of the charge amplifier 56 is read by the circuit 58 and then the charge amplifier 56 is reset in response to a reset signal issued by the circuit 58.
  • a similar arrangement is provided within the lane controller 22 of the second lane.
  • the lane controllers may be kept in synchronism by an electronic communications link (not shown).
  • the stored outputs of the charge amplifier 56 corresponds to the signals ⁇ 12 to ⁇ 14 shown in Figures 3 and 4.
  • the operation of the two lane system has been described with reference to a four phase measurement scheme.
  • N is an integer
  • the minimum number of discrete time periods within each measurement cycle is equal to (N + 1) but greater accuracy can be achieved with more measurement periods.
  • controller If either controller cannot verify the correct functioning of the other lane, the controller repeatedly operates the switch 54 to cause the LED 4 to flash on and off at a relatively low frequency so as to attract the user's attention.
  • FIG. 6 schematically illustrates a timing diagram for an indicator having three lanes.
  • the timing diagram is an extension to that shown in Figure 3.
  • Each measurement cycle is divided into six periods P1 to P6.
  • the light source of the first lane LED 1 is actuated during each first period
  • the light source of the second lane LED 2 is actuated during each third period
  • the light source of the third lane LED 3 is actuated during each fifth period.
  • Figure 6 illustrates the wave forms for a complete first cycle and a partially complete second cycle. Measurements made by the first lane sensor (sensor 1) during the periods P2 to P6 of the first cycle are designated ⁇ 12 to ⁇ 16 , respectively, whereas the corresponding measurements in the second cycle are designated ⁇ ' 12 to ⁇ ' 16 . A similar nomenclature is used with respect to measurements made by the sensors of the second and third lanes within each period.
  • FIGs 7 to 9 illustrate the signal processing arrangements within the first, second and third lanes, respectively.
  • the processing arrangements are very similar so only the processing arrangement of the first lane, as illustrated in Figure 7, will be described in detail.
  • the signal processing arrangement comprises a first summer 30, a divide by two 32, a second summer 34 and an averaging element 36 as described with reference to Figure 4.
  • An output of the averaging element 36 is applied to a comparator 70 whose output is a logic 1 when the output of the averager 36 is below a predetermined threshold, and a logic 0 when the output of the averager 36 is above the predetermined threshold.
  • the first summer 30 receives the signals ⁇ 12 and ⁇ 14 and forms a sum thereof. This sum is divided by two to form an average of ⁇ 12 and ⁇ 14 .
  • the second summer 34 receives the signals ⁇ 13 and an average of ⁇ 12 and ⁇ 14 and forms a difference between these signals.
  • An output of the comparator 70 is supplied to a first input of an OR gate 72.
  • an output of the relevant comparator 70 or 82 goes high and a "fail" signal is asserted at an output of the OR gate 72.
  • the output of the OR gate 72 is connected to a lane 1 flash circuit 86 via an electronically controllable switch 84 which is closed during the test sequence.
  • the lane 1 flash circuit 86 causes the LED of lane 1 to be flashed after the completion of the test sequence if a failure has been detected.
  • a similar arrangement is provided in the second and third lanes as illustrated in Figures 8 and 9. Each lane may assert a "fail" signal to be communicate to other systems.
  • test sequences rely on the controllers being kept in synchronism, but it may be desirable to keep the controllers of each lane electrically isolated from the or each other lane so as to lessen the risk that a fault in one controller causes a failure in another controller. This may be done using an optical path provided by the sources and photo detectors, as will be explained with reference to the two lane controller illustrated in Figure 2.
  • confusion may arise between the orderly end of the test and a genuine lane failure unless both lanes finish the test together.
  • one controller is arranged as a master controller and the other controller is arranged to adjust its operation to become synchronised with the master controller.
  • the second controller can detect its relative phase with respect to the first controller by comparing the ambient light measurements made during the fourth and subsequent second periods. If more light is consistently measured during the fourth period than the following second period, this indicates that the first lane light source is coming on somewhat early or much too late with respect to the second lane. In either case, the second lane advances the start of its cycle a small amount in proportion to the light level measured in the fourth period minus the light level measured in the second period. Thus the second lane controller can catch up with the first lane controller over a number of measurement cycles, say 16 to 64.
  • the result of ⁇ 24 minus ⁇ ' 22 as determined by a subtracter 90 is supplied to the input of a loop compensator 92, for example, a lead-lag network.
  • An output of the compensator 92 is supplied to a circuit 94 for adjusting the start of the cycle of the second lane.
  • An output of the compensator 92 is also provided to a synchronism detector 96 which enables the test sequence to be performed when the first and second lanes are synchronised.
  • the indicator In the event that the indicator is required to display that a system has failed, it may be illuminated continuously.
  • a light source may fail after the test sequence has been performed but while the vehicle is still in operation.
  • the indicator may be arranged to undergo a periodic test or a continuous further test in which the light sources of each lane are pulsed on very briefly, for say one microsecond, such that their illumination is substantially imperceptible.
  • the sequence illustrated in Figure 3 may be modified to that illustrated in Figure 11 in which the illumination during the period P1 is reduced to two short pulses at the beginning and the end of the period P1.
  • Such an arrangement still enables the processing circuits illustrated in Figures 4, 5 and 7 to 9 to detect the correct operation of the light sources, albeit with a requirement to average a larger number of measurements in order to maintain reliability.
  • the first, second and any further light sources need not be arranged to indicate the same failure but may be in adjacent malfunction indicator lamps provided that light from one lamp is detectable within the or each other lamp.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
EP96300682A 1995-02-10 1996-01-31 Indicateur avec détection de défauts Withdrawn EP0726553A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9502602.7A GB9502602D0 (en) 1995-02-10 1995-02-10 indicator having fault detection
GB9502602 1995-02-10

Publications (1)

Publication Number Publication Date
EP0726553A1 true EP0726553A1 (fr) 1996-08-14

Family

ID=10769384

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96300682A Withdrawn EP0726553A1 (fr) 1995-02-10 1996-01-31 Indicateur avec détection de défauts

Country Status (2)

Country Link
EP (1) EP0726553A1 (fr)
GB (1) GB9502602D0 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112249345B (zh) * 2020-10-15 2024-04-16 航宇救生装备有限公司 一种椅载电子式开伞器状态指示装置及方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4588896A (en) * 1983-11-18 1986-05-13 Eastman Kodak Company Bistable circuits having a monolithic device formed with light emitting diodes and detectors
DE3630372A1 (de) * 1986-09-05 1988-03-10 Siemens Ag Leuchtdiode mit integriertem funktions-ueberwachungselement
US4990896A (en) * 1989-05-09 1991-02-05 Gray William F Light responsive device for monitoring on-line indicator lights

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4588896A (en) * 1983-11-18 1986-05-13 Eastman Kodak Company Bistable circuits having a monolithic device formed with light emitting diodes and detectors
DE3630372A1 (de) * 1986-09-05 1988-03-10 Siemens Ag Leuchtdiode mit integriertem funktions-ueberwachungselement
US4990896A (en) * 1989-05-09 1991-02-05 Gray William F Light responsive device for monitoring on-line indicator lights

Also Published As

Publication number Publication date
GB9502602D0 (en) 1995-03-29

Similar Documents

Publication Publication Date Title
US4689573A (en) On-vehicle diagnostic unit for electronic ignition systems
US7652480B2 (en) Methods and systems for testing a functional status of a light unit
CA2316632C (fr) Module d'interface de signaux
US4451822A (en) Device for automatically checking a plurality of electric indicator lights
US4990895A (en) Method and apparatus for testing photoelectric circuits
EP1501167A2 (fr) Système et procédé pour détecter des défauts dans un réseau électrique d'un avion
GB2283813A (en) Photoelectric smoke sensor sensitivity test
US4568923A (en) Fire alarm system
EP0726553A1 (fr) Indicateur avec détection de défauts
CA1232468A (fr) Methode et instrument de controle d'un cable optique pour evaluer son aptitude a transmettre la lumiere et mesurer les degerditions inadmissibles attribuables a des defauts
US4024473A (en) Stroboscopic device
US10939528B2 (en) Electronic circuit with an LED module
CN112512864B (zh) 用于从牵引车动态地监控挂车照明的方法
US6917164B2 (en) Light signaling device related to the operating state of a system
CA2406582C (fr) Processus de gestion d'un dispositif de signalisation lumineuse, et dispositif utilisant ce processus, particulierement pour l'avionique
US4315196A (en) Disconnection detecting circuit of double-filament spherical lamp
US6696799B2 (en) Diagnostic system for a strobe lamp and its operating circuit
US3745547A (en) Lamp supervisory circuit
EP0906851A1 (fr) Procédé et dispositif de détection de défaillance pour un indicateur lumineux
CN211506141U (zh) 一种双滤光片切换测试装置
PL164731B1 (pl) Automat do gier hazardowych PL
JP2993783B2 (ja) 警告表示制御装置
JP2515125Y2 (ja) 多光軸光電スイッチ
KR200162414Y1 (ko) 화재전용 asic 저전류 구동회로
JP3688501B2 (ja) 光電式分離型感知器

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE ES FR GB IT

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19970215