WO1996031361A2 - Dispositif permettant de detecter l'occupation d'un siege - Google Patents

Dispositif permettant de detecter l'occupation d'un siege Download PDF

Info

Publication number
WO1996031361A2
WO1996031361A2 PCT/IB1996/000287 IB9600287W WO9631361A2 WO 1996031361 A2 WO1996031361 A2 WO 1996031361A2 IB 9600287 W IB9600287 W IB 9600287W WO 9631361 A2 WO9631361 A2 WO 9631361A2
Authority
WO
WIPO (PCT)
Prior art keywords
sensor system
seat
load
sensor
cable
Prior art date
Application number
PCT/IB1996/000287
Other languages
English (en)
Inventor
Richard Hunter Brown
Original Assignee
The Whitaker Corporation
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
Priority claimed from GBGB9507161.9A external-priority patent/GB9507161D0/en
Priority claimed from GBGB9507160.1A external-priority patent/GB9507160D0/en
Priority claimed from GBGB9511663.8A external-priority patent/GB9511663D0/en
Application filed by The Whitaker Corporation filed Critical The Whitaker Corporation
Publication of WO1996031361A2 publication Critical patent/WO1996031361A2/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
    • B60R21/015—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting the presence or position of passengers, passenger seats or child seats, and the related safety parameters therefor, e.g. speed or timing of airbag inflation in relation to occupant position or seat belt use
    • B60R21/01512—Passenger detection systems
    • B60R21/01516—Passenger detection systems using force or pressure sensing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60N—SEATS SPECIALLY ADAPTED FOR VEHICLES; VEHICLE PASSENGER ACCOMMODATION NOT OTHERWISE PROVIDED FOR
    • B60N2/00—Seats specially adapted for vehicles; Arrangement or mounting of seats in vehicles
    • B60N2/002—Seats provided with an occupancy detection means mounted therein or thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
    • B60R21/015—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting the presence or position of passengers, passenger seats or child seats, and the related safety parameters therefor, e.g. speed or timing of airbag inflation in relation to occupant position or seat belt use
    • B60R21/01512—Passenger detection systems
    • B60R21/01516—Passenger detection systems using force or pressure sensing means
    • B60R21/01526—Passenger detection systems using force or pressure sensing means using piezoelectric elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
    • B60R21/015—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting the presence or position of passengers, passenger seats or child seats, and the related safety parameters therefor, e.g. speed or timing of airbag inflation in relation to occupant position or seat belt use
    • B60R21/01512—Passenger detection systems
    • B60R21/0153—Passenger detection systems using field detection presence sensors
    • B60R21/01532—Passenger detection systems using field detection presence sensors using electric or capacitive field sensors
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
    • E05B77/00—Vehicle locks characterised by special functions or purposes
    • E05B77/22—Functions related to actuation of locks from the passenger compartment of the vehicle
    • E05B77/24—Functions related to actuation of locks from the passenger compartment of the vehicle preventing use of an inner door handle, sill button, lock knob or the like
    • E05B77/26—Functions related to actuation of locks from the passenger compartment of the vehicle preventing use of an inner door handle, sill button, lock knob or the like specially adapted for child safety
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
    • E05B77/00—Vehicle locks characterised by special functions or purposes
    • E05B77/22—Functions related to actuation of locks from the passenger compartment of the vehicle
    • E05B77/24—Functions related to actuation of locks from the passenger compartment of the vehicle preventing use of an inner door handle, sill button, lock knob or the like
    • E05B77/28—Functions related to actuation of locks from the passenger compartment of the vehicle preventing use of an inner door handle, sill button, lock knob or the like for anti-theft purposes, e.g. double-locking or super-locking
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05B—LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
    • E05B81/00—Power-actuated vehicle locks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/02—Measuring force or stress, in general by hydraulic or pneumatic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
    • G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/24—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
    • G01L5/243—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed using washers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P13/00—Indicating or recording presence, absence, or direction, of movement
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/09—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by piezoelectric pick-up
    • G01P15/0907—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by piezoelectric pick-up of the compression mode type

Definitions

  • the invention is directed to a sensor system which could be used for determining whether an automobile seat is occupied, more particularly for example to control an automotive airbag safety system.
  • the standard locking system is of conventional design and would involve power door locks that are responsive to activation from within the vehicle at a central location, typically accessible by the driver, or at each of the individual doors and from the outside of the vehicle by use of a key, either conventional or electronic.
  • This locking system results in the doors being locked but they can still be opened from the inside of the vehicle.
  • the additional and newly incorporated dead-lock feature is incorporated for anti-theft protection and provides that the doors will be prevented from being opened without the use of a "key”.
  • the "key” may either be a conventional key, an electronic code or an infra-red source as is now common in remote locking devices.
  • the dead-lock feature performs adequately as an anti-theft device, the system is not completely user friendly in that it is possible that the system would be activated with an occupant still in the vehicle. If this were to occur, it is not possible for the occupant to exit the vehicle, as even from the inside, without the "key", once activated, the dead-lock feature will maintain all of the doors in a locked condition. Especially with the use of the infra-red locking devices and where operators are not fully cognisant of the systems within the vehicle, it is possible that someone may become accidentally trapped within the vehicle. It would be especially advantageous to provide a sensor system that would sense when a person is in the vehicle and would prevent activation of the dead ⁇ lock inhibitor, whereby the locking system might instead default to the standard locking condition where the occupant could unlock the door and exit the vehicle.
  • airbags safety restraint systems
  • airbags safety restraint systems
  • one airbag it is typical for one airbag to be located within the steering wheel on the driver's side, while another is located within the front dash on the passenger's side.
  • Other locations for airbags may also be used.
  • the airbags are ignited and activated to prevent the occupants from incurring harm. While these systems have increased the safety within the automobiles, they are yet to be perfected, in so far as sensing capabilities are concerned. Said differently, the airbags always fire regardless of whether or not someone occupies the seats and independent of the physical characteristics of the occupant.
  • the present invention describes a novel sensor system which could be especially useful in determining the presence of a human occupant in a seat (typically a car passenger seat) through the use of a novel device.
  • the device may be enhanced in such a way as to allow a self-test to be preformed periodically.
  • piezoelectric sensor cable responds strongly to the event of a person sitting down on the seat, it is anticipated that the more useful information content of the signals from the cable comprise the much smaller signals from slight bodily movement, muscular impulses and other physiological signs such as pulse and respiration. It is these smaller signals that enable distinguishing whether an alive being is present upon the seat or an inanimate object, such as a box of books, is resting thereupon. These signals are reasonably easy to detect when the vehicle is stationary making such a sensor particularly useful for the deadlock inhibitor application described above.
  • these small signals generated by the occupancy sensor are all found to be substantially incoherent when the vehicle is in motion due to the associated vehicle induced vibration that is also detected.
  • comparison of the signals from the accelerometer(s) and from the piezoelectric cable sensor(s) may be compared/interpreted to deduce whether the load (if any) borne by the seat is animate or inanimate.
  • the force transducer could provide the magnitude of the load, thereby providing additional useful information.
  • the force transducer may operate on a principle whereby an ultrasonic pulse is used to measure the thickness of a compressible compliant elastomeric layer, and the accelerometer may use one or several cantilever beams, with each surface of the beam(s) bearing a piezoelectric layer such that one layer may be used to detect vibration and the other used to excite vibration.
  • the combined sensor may be used to detect weight applied in compression, with overall acceleration of the structure being detected and corresponding correction applied. It may even be desirable to combine the two into a single device.
  • Combined force transducers and accelerometers are known, and used in the field of vibration monitoring to measure the mechanical impedance of a structure.
  • US Patent No. 4,964,302 discloses a force transducer comprising a base, an ultrasonic transducer capable of launching and receiving fast acoustic signals, an elastomeric layer, and a reflector plate.
  • the time of flight of an ultrasonic pulse is used to determine the compression of the elastomeric layer which in turn yields an estimate of the applied force. It is a characteristic feature of this device that, when operating, a train of pulses is always present, with the width of each pulse representing the distance between the piezoelectric layer and the reflector plate. If a malfunction occurs, then the pulse is either absent, or has a width which lies outside normal operating limits, and so the malfunction is readily detected.
  • the device of the present invention further differs from the known art in that each component is designed to allow self-test, and preferably supplies an output of digital form which may be read easily by a micro-controller or similar interface.
  • an ultrasonic force transducer as described above can take the form of an annular piezoelectric film deposited on an annular washer, with a second annular washer sandwiching the piezoelectric film as well as an annular shaped elastomeric member.
  • a fastener can be positioned between the two washers to retain them n the expanded position, but where they are allowed to contract.
  • the washers are the ground electrodes.
  • an ultrasonic force transducer as described above is formed using an annular printed circuit board as a carrier for the piezoelectric transducer, preferably formed using thin PVDF (polyvinylidene fluoride) or copolymer (P(VDF)TrFE) film.
  • a cavity above the PCB/film structure is filled with compliant elastomer such as silicone rubber.
  • An upper cap of annular form acts both as a thrust plate (for exerting compressive force on the elastomer) , and as a reflector for the ultrasonic signals.
  • a cavity below the PCB allows the mounting of a metallic beam structure, forming the accelerometer device as described above.
  • the accelerometer comprises at least one beam, angled so as to respond to vertical acceleration through the sensor.
  • a further embodiment allows for another sensing axis in a lateral direction, such that forward acceleration is detected independently.
  • the required electronic circuitry for operation of the force sensor and the accelerometer may be formed separately and mounted in chip form on appropriate surfaces of the PCB, or alternatively may be combined into a single structure and similarly mounted to the PCB. It is anticipated that the chips be wire-bonded to the PCB, commonly described as "chip-on-board" process.
  • the housing for the above outlined structure comprises a metal lower body and metal top cap, such that the entire assembly is well shielded from electromagnetic disturbance.
  • the outer metal housing may be connected separately to the chassis of the vehicle, isolated from the sensor ground line.
  • the ultrasonic force sensor as described above allows provision of an additional propagation path of fixed length, or known additional length beyond the moving path length, such that the response of the compliant elastomeric layer can be compensated for the effects of temperature.
  • Such compensation may be applied within the sensor drive circuitry if the output signal comprises the difference in flight-time between the moving path and the reference path.
  • the reflecting top plate may include a recess of known depth, covering an area of one- half that of the total reflecting area, such that two echoes arrive back from this reflector: one at the time corresponding to (2h/c) , and another at a time corresponding to (2(h+dh)/c), where h is the spacing between the piezo film sensor and the nearer portion of the top plate, dh is the depth of the recess, and c is the speed of sound in the elastomer.
  • Combined force and acceleration sensor may conveniently be installed as part of the seat mounting arrangement, such that a known proportion of the seat load is borne by the structure.
  • the signals presented by both force transducer and accelerometer are in the form of digital signals, for example with a pulse width coding relating to amplitude. It is anticipated that force, acceleration in "Z-axis” and (where optionally detected) acceleration in "Y-axis” signals are brought out independently, to allow flexibility in the further interpretation and processing of the information.
  • Signals generated by the force transducer allow approximate measurement of the total load borne by the seat. Further compensation for vehicle vibration (using signals from the accelerometer(s) allow more accurate weighing of the load, such that a weight threshold may be applied to the occupancy decision algorithm.
  • the piezoelectric cable may be terminated at its far end with a capacitance, where the value of this added capacitance is similar or greater than the sensor cable, such that, by periodically measuring total capacitance, the integrity of the cable may be checked.
  • Figure 1 shows a representational view of a seat occupancy sensor system according to the present invention
  • Figure 2 shows a schematic view of the seat occupancy system of Figure 1;
  • Figure 3 shows an electrical circuit incorporated into the system of Figure 1;
  • Figure 4 shows a cross sectional view of the first embodiment of a transducer of the system of Figure 1;
  • Figure 5 shows piezoelectric film deposited on the lower washer of the transducer of Figure 4.
  • Figure 6 shows a representation of the electrical characteristics of the force transducer of Figure 4
  • Figure 7 shows the upper and lower cover of a second embodiment of the transducer of Figure 4;
  • Figure 8 shows the lower housing part being installed with a printed circuit board carrying the piezoelectric film and an elastomeric member of the second embodiment of Figure 7;
  • Figure 9 shows the complete assembly of the second embodiment
  • Figure 10 shows a further embodiment of a transducer including an accelerometer mounted to the lower side of the printed circuit board;
  • FIG 11 shows the time response characteristics of the embodiment shown in Figure 10.
  • a representational and schematic view is shown comprising a seat 2 having an occupancy sensor 4 of piezoelectric cable 5 and a combination force transducer and acceleration transducer 6 affixed to the seat 2 by an anchor point 8.
  • the signals from the occupancy sensor 4 and force transducing accelerometer 6 are brought into an electronic control module (ECM) 10 which, by simple means of counting and timing of digital events, discriminates the various conditions of occupancy of the seat (vacant, animate occupant, inner load, etc.).
  • ECM electronice control module
  • Another sensor such as a transponder 12 can also be included, which could be used to detect if a child's car seat is present, and if so, in what direction it is facing.
  • the piezo mat 4 is comprised of a length of piezo cable 5, approximately two meters in length, which is wound into the sheet or mat 4 that could fit into the seat 2.
  • the far end 14 of the cable 5 is connected into a charge amplifier 15 as shown in Figure 3.
  • the opposite end 16 can be terminated with an extra capacitive load 18. If the cable 5 has a capacitance of approximately 800 Picofarads/metre which is normal, two metres would yield 1600 Picofarads. This may result in difficulty detecting significant changes in capacitance.
  • Typical piezoelectric cable shown a capacitance of 800pF/metre. Based on this figure, the total sensor capacitance is determined and a load capacitance 18, desirably at least double that of the sensor 5, can be added to the end 16 of the sensor 5. This combined capacitance can then be used in an electrical circuit of Figure 3 in order to monitor the capacitance and detect sensor responses. The capacitance presence can also be detected by an oscillator operating at a frequency determined in part by the capacitance. By arranging a voltage dividing network of capacitive reactances the fault conditions of short circuited or severed cables would create distinctly different oscillator frequencies which could be filtered to create logic signals for "gating" the final output.
  • a DC bias may be incorporated to detect resistance across the cable such as if contamination of a splice or termination were to be occurring. All of which is in circuitry incorporating logic that reverts to a state detecting a piezo event.
  • the cable 5 or mat 4 is actually put into the seat 2 itself, close to the surface, as shown in Figure 1.
  • the cable 5 or mat 4 may also be disposed in other locations, such as beneath the seat 2.
  • large voltage signals are given off by the cable 5 or mat 4 initially, but that is not the interesting signal. Rather what is being looked for is a certain frequency band that is quite characteristic of human life. If a box is placed on this cable mat 4, an initial signal is given as the box is placed.
  • a band pass filter 20 should also be included possibly set to 0.5 Hz to 5 Hz concentrated about 1 cycle per second. That is typical of an animate object being present and where a pulse occurs and also tends to coincide with muscular twitching. This is something that looks quite easy to detect. The only difficulty is when you have a lot of vehicle vibration present as well, you want to make sure that the vibration your picking up is not just the box bouncing on the seat.
  • the mat 4 could be directly incorporated into an automobile seat 2.
  • the seat 2 would be any one of the seats in the vehicle.
  • suitable electronics for example, buffer, bandpass filter, event detector or counter, such as shown in Figure 3, for isolating the desired signals as described above.
  • the ECM 10 would then take on the function of controlling various aspects of the vehicle, such as the locking systems to inhibit the external deadlock activation if required.
  • the ECM 10 may take on other control functions such as individual seat heaters and may control one or more functions.
  • the accelerometer/force sensor 6 is especially useful in this regard and will now be described.
  • the load sensor 6 is shown at 30 comprised of upper and lower washer members in the form of annular shaped disks, 32 and 34 respectively where a fastener assembly 36 is inserted through the centre of the washer members 32 and 34.
  • a piezoelectric film element 38 is bonded to the lower washer 34, as shown in Figures 1 and 2, and has a silver ink electrode 40 printed on the upper surface of the film only.
  • the film is bonded with a very thin layer of epoxy resin or similar adhesive to the lower washer, whereby the lower washer 34 serves as a ground electrode with electrical coupling through the fastener member 36 to the upper washer 32.
  • An annular shaped elastomeric member 42 is positioned above the piezoelectric film 10 and is also sandwiched by the upper and lower washer members 32,34.
  • the piezoelectric film element 38 is used to launch an acoustic pulse into the elastomer 42 whereby a much larger proportion of the energy propagates into the elastomer than the steel washer 34, since the acoustic impedance of the elastomer 14 is much more closely matched to the piezo polymer 38.
  • the time delay between transmission of this pulse, and the arrival time at the film 38 after the pulse reflects from the upper washer 32, allows the thickness of the elastomer 14 to be measured.
  • the lock nut 44 of the fastener 8 arrangement prevents any loosening of fastener under load, so that the device 30 works only in compression and not for extension.
  • the second embodiment of the load sensor identified as 60 will be described with greater detail.
  • the upper and lower washers 32,34 have been replaced by an upper cover 62 and a lower housing portion 64. Both of these members however are preferably of annular shape, the lower housing member 64 including a piezoelectric film 66 positioned on a printed circuit board 68 with an annular elastomeric ring 70 being positioned above the piezoelectric film 66.
  • the assembly is completed by the placement of the upper cover 62 over the assembly of Figure 8, and although not specifically shown, it is anticipated that a fastener member, similar to that shown in Figure 4, would retain the two cover members 62,64 together.
  • the lower housing member 64 has a cup shaped cross-sectional recess 72 defining an upwardly directed shoulder at 74, upon which the printed circuit board 68 may rest ( Figure 8) .
  • an accelerometer 78 can be mounted to the under side of the printed circuit board 68 to reside in the recess 76.
  • the printed circuit board 68 includes a copper track on the top thereof forming a signal electrode, with the piezo film 66 bonded thereto with no metallization underneath, such that the film 66 sits over the copper. The copper then effectively becomes the active electrode for the film 66. The top of the film 66 would be fully metallized and connected to ground.
  • the double sided circuit board 68 is significant, as it allows a shielded sensor just by using standard patterning of copper tracks on a circuit board 68. Both sides of the circuit board 68 carry copper tracks of different patterns.
  • the upper side of the piezo film 66 is fully metallized and just connected to the ground.
  • the signal electrode which is a copper track between the circuit board 68 and the piezo film 66 is driven on outsides of the receiver signal electrode.
  • a pulse When a pulse is then applied onto that copper track on the board, it causes the piezo film 66 to expand or contract and it launches an acoustic signal into that elastomer 70 which will actually propagates down into the circuit board 68 material itself but most of it is absorbed or dissipated. So most of the energy travels up into the elastomer 70.
  • the acoustic signal hits the top plate 62 which will be metallic and the top plate 62 acts like a mirror, the elastomer 70 carries the signal back down and then it arrives back at the same piezo film element 66 that it was sent on. By which time the electronics have switched into receive mode and is ready to catch the echo. So actually pulse echo detection is being carried out with exactly the same piece of piezo film.
  • a recess 80 in the top plate 62 as shown in Figure 10, or a shaped reflector so that there are two distinct paths, a short path (h) and a long path (h+dh) , as long as there is a known difference apart that allows the two paths (h, h+dh) electronically to be read independently, and therefore to compensate for any change in the speed of sound in that elastomer as temperature varies, e.g. from -40 to +70 * C this would mean some change in the speed of sound.
  • the underside of the circuit board 68 would carry a miniature accelerometer 78 possibly with its own custom chip as well. So the principle of this type of device is that a beam therein basically flexes as it undergoes vertical acceleration and piezo film is applied to at least one surface and picks up the bending of that beam, the output of which is then a measure of acceleration. It is also possible to put piezo film on both sides of that beam and to do the self diagnostics, by putting in a short test pulse onto the underside. The pulse causes the beam to deflect and that deflection can then be picked up by the piezo film on the opposite side which would generate an output. If there is film on both sides of the beam and if a 4 Volt logical pulse is applied to one side of the beam and listen, using the film on the other side of the receiver then one can actually verify that the beam does indeed deflect when we apply the 5 Volt pulse.
  • the beam is mounted as a cantilever, so that it is clamped on one end and the other end is free. As the whole assembly is vertically accelerated upwards, then the beam deflects under its own inertia resulting from its own self mass and the film bonded onto the beam.
  • the beam must be tiny (1mm) wide and a couple of mm's long, possibly (3mm) , but it does flex and, as the film is highly sensitive, it detects flexing or deflection. The film itself would see a stretching as beam flexes.
  • the resulting electrical signal is proportional to the acceleration.
  • the force transducer 32 on its own can weight the occupant but only if the vehicle was stationary, so the force transducer 32 with the accelerometer, can compensate with the vertical acceleration.
  • the piezo cable sensor detects displacement of the load thereupon.
  • the physiological life signs of the occupant, against the counter example that there is a box on the seat must be separated to determine true occupancy.
  • the sensor system is then further enhanced so that if you were driving over a cobblestone street, where you would then get signals that look rather similar to what you get from a person under different conditions, by incorporating an accelerometer into the system the information therefrom would be used to further qualify the output of the cable sensor.
  • a force sensor may also be provided as part of the system whereby the seat occupant's weight is determined which could then further be fed to the ECM in order to control various aspects of the automobile.
  • the accelerometer functions then partly to compensate for both the force sensors and the cable sensors for the dynamics of vehicle motion.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Child & Adolescent Psychology (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Transportation (AREA)
  • Acoustics & Sound (AREA)
  • Toxicology (AREA)
  • Seats For Vehicles (AREA)

Abstract

Un système de capteur permet de détecter l'occupation d'un siège (2) relié à un châssis et de faire la distinction entre des charges animées et inanimées. Ce système de capteur comprend un transducteur de mouvement (4) couplé au siège (2) et configuré pour émettre un premier signal de sortie en réponse à un mouvement de la charge sur ce siège (2). Il comprend aussi un dispositif de commande (10) qui reçoit ce premier signal de sortie et en discerne une composante qui est carastéristique d'un mouvement animé.
PCT/IB1996/000287 1995-04-06 1996-04-04 Dispositif permettant de detecter l'occupation d'un siege WO1996031361A2 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB9507161.9 1995-04-06
GBGB9507161.9A GB9507161D0 (en) 1995-04-06 1995-04-06 Means of determining seat occupancy
GB9507160.1 1995-04-06
GBGB9507160.1A GB9507160D0 (en) 1995-04-06 1995-04-06 Means of determining seat occupancy
GBGB9511663.8A GB9511663D0 (en) 1995-06-08 1995-06-08 Means of determining seat occupancy
GB9511663.8 1995-06-08

Publications (1)

Publication Number Publication Date
WO1996031361A2 true WO1996031361A2 (fr) 1996-10-10

Family

ID=27267661

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB1996/000287 WO1996031361A2 (fr) 1995-04-06 1996-04-04 Dispositif permettant de detecter l'occupation d'un siege

Country Status (1)

Country Link
WO (1) WO1996031361A2 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000052440A1 (fr) * 1999-03-05 2000-09-08 Hill-Rom Services, Inc. Systeme et procede de controle
EP0978614A3 (fr) * 1998-08-05 2001-01-31 Rover Group Limited Véhicule avec serrures à sécurité enfants automatique
EP1139078A2 (fr) * 2000-03-29 2001-10-04 Delphi Technologies, Inc. Détermination d'un poids
FR2812329A1 (fr) * 2000-07-31 2002-02-01 Valeo Securite Habitacle Procede de gestion de l'acces a un vehicule automobile et dispositif pour la mise en oeuvre de ce procede
EP1452400A1 (fr) * 1997-05-12 2004-09-01 Automotive Systems Laboratory Inc. Dispositif de prédiction de la tension d'une ceinture de sécurité via un accéléromètre monté sur le siège et un capteur de poids

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1452400A1 (fr) * 1997-05-12 2004-09-01 Automotive Systems Laboratory Inc. Dispositif de prédiction de la tension d'une ceinture de sécurité via un accéléromètre monté sur le siège et un capteur de poids
EP0978614A3 (fr) * 1998-08-05 2001-01-31 Rover Group Limited Véhicule avec serrures à sécurité enfants automatique
WO2000052440A1 (fr) * 1999-03-05 2000-09-08 Hill-Rom Services, Inc. Systeme et procede de controle
US6252512B1 (en) 1999-03-05 2001-06-26 Hill-Rom, Inc. Monitoring system and method
US6819254B2 (en) 1999-03-05 2004-11-16 Hill-Rom Services, Inc. Monitoring system and method
EP1139078A2 (fr) * 2000-03-29 2001-10-04 Delphi Technologies, Inc. Détermination d'un poids
EP1139078A3 (fr) * 2000-03-29 2003-04-09 Delphi Technologies, Inc. Détermination d'un poids
FR2812329A1 (fr) * 2000-07-31 2002-02-01 Valeo Securite Habitacle Procede de gestion de l'acces a un vehicule automobile et dispositif pour la mise en oeuvre de ce procede

Similar Documents

Publication Publication Date Title
EP1621412B1 (fr) Capteur de collision omnidirectionnel
EP1757490B1 (fr) Système de détection d'impact pour véhicule
JP3995109B2 (ja) 車両ドアエッジの移動感知用のシステム及び方法
US6275146B1 (en) Vehicle occupant sensing
US5767766A (en) Apparatus and method for monitoring vehicular impacts using magnetostrictive sensors
CA2414608C (fr) Detecteur piezo-electrique
US5797623A (en) Smart skin sensor for real-time side impact detection and off-line diagnostics
US7836998B2 (en) Crash sensor
US4864288A (en) Hall effect motion detector responsive to dual frequency stimuli
CA2473556C (fr) Detecteur d'impact omnidirectionnel
JP2930729B2 (ja) 加速度検出用のマイクロメカニクスセンサユニット
WO1996031361A2 (fr) Dispositif permettant de detecter l'occupation d'un siege
WO2004016465A2 (fr) Detecteur de charge de dossier de siege
JP4694478B2 (ja) 圧電センサを介した衝突検知
US20030229431A1 (en) Electrical circuit module with magnetic detection of loose or detached state
WO2008088948A1 (fr) Capteur de pression et d'accélération
CA1239455A (fr) Detecteur pour systeme d'alarme
JPH02504078A (ja) 加速度センサ
JPH1062444A (ja) 加速度センサ及びコントロールユニット及び車両の乗員保護システム
EP1619521A1 (fr) Electrode transmetteur capacitive
EP1795880B1 (fr) Détecteur d'impact omni-directionnel
US20040114465A1 (en) System for classifying occupants of a vehicle
WO2004067330A1 (fr) Revetement conducteur a detecteur integre de passager
AU2003203046A1 (en) Omni-directional crash sensor

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): CN JP KR US

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct app. not ent. europ. phase