CA1089950A - Accelerometers - Google Patents

Abstract

A B S T R A C T

The invention provides for an accelerometer having an acceleration responsive means associated with a presence detector for detecting the continuous activation of the acceleration responsive means for a predetermined time duration. The accelerometer may further have recording and indicating means responsive to the presence detector. The accelerometer may particularly be used in a motor vehicle to detect excessive acceleration thereof.

Description

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; THIS INVENTION relates to improvements in or relating to accelerometers ~or use with vehicles and -to vehicles having the accelero~eters.

According to the invention there is provided an apparatus Eor detecting and recording abuse o:E a motor vehiclc~
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an aoceleration responsive means which provides a ~irst output si~nal responsive to acceleration o~ the veh1cle above a presat level;
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a signal presence detector means connec-ted to -the accelera-tion responsive means providing a second output signal when the first output signal persists for a ~irst prede-termined period of time;
a recorder;
means responsive to the second outpu-t signal ~or actuating the recorder and then preventing the recorder from recording any further signals during a second period o~ time substantially greater than the first period of time.

In -this specification by "accelera-tion" is to be understood both positive and negative acceleration, i.e. speeding up and slowing down, unless otherwise indica-ted.

The signal presence detec-tor means ma~ continue to provide the second output signal un-til the firs-t output signal is removed, at which time the signal presence detec-tor means resets itself and then only provides the second output signal when it again recelves the first output signal and the first output signal persists ~or the first period of time. Similarly, the means responsive to the second ou-tput signal may be auto-matically reset at -the end of each second period o~ time. Al-ternatively, -the signal presence detec-tor means may be au-to-matically reset a-t the end of each :Eirst period o~ -time such that i~ -the ~irst ou-tput signal persists for a period of time substantially greater -than the first period of time, the signal presence detector means provides a train o:E seconcl output signals.

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., The signal presence detector means and the means responsive to the second output signal may be variable so as to vary both the first and -the second time periods.

The acceleration responsive means may be respon~sive to inertial forces and to linear or centripetal acceleration.
The acceleration responsive means may be adapted -to provide a digital output signal. Convenien-tly, it may be a binary, "o~-o~
device. The acceleration responsive means may be a pendulum, a mercury switch or a cystal transducer.

The apparatus may~be electrically, magnetically, mechanically or hydraulically operable. Pre~erably, -the appara-tus is elec-trically operable. Accordingly, -the acceleration responsive means, the signal presence detector means, and the means responsive to -the second output signal may all be elec-tri-cally operable.

In one embodiment, the accelera-tion responsive means - may comprise an electrically conductive pendulum and a con-tac-t,the pendulum and the con-tac-t having electrical connectian means with khe pendulum being pivo-table into con-tact with the contact, 2Q due to a predetermined iner-tial accelera-tlve ~orce, to electrica~ly bridge the connec-tlon means. The signal presence detecto.r means may comprise an in-tegrator and a level de-tec-tor~ the lntegrator being supplied ~rom a voltage source via the pendulum and the contact~ The inkegrator may conveniently be in the :Eorm o:f a Z5 series capacitive/resistive ne-twork, the level de-ector being ~.

5ai set to detect a vol-tage level subs-tan-tially less than the supply voltage. A discharge path for the capacitor is provided in this embodiment.

The recorder may be a coun-ter ~or counting the number of times a second output signal is provided by the signal presence de-tector means when the recorder is not disabled by the secbnd output signal responsive means.

Further, the apparatus may include visual or audible indicating means ~that are responsive to the second outpu-t signal responsive means. Such indicating means may for example be lamps, buzzers, loudspeakers, a hooter, or the like.

ln an elec-trically operable embodimen-t o~ the second output signal responsive means, the said means may include a ramp generator and a level detec~tor arranged to ~orm a time base.
Alternatively, a monostable multi-vibrator or some other timing device may be utilised.
, In order to tes-t whether -the apparatus is operating correctly, a test means may be included. The test means may supply an artificial first ou-tput signal to the signal presence detector means, to -tes-t the opera-tion o~ the apparatus. Th~
tes-t means may ~urther be lockable so tha-t only authorised per-~ons can test the appara-tus.

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The accelera-tion responsive means may be further adapted to provide one of a number of output signals dependen-t on the character of -the acceleration. For example, the output signals may be depen~ent on the quantised amplitude of the acceleration or on the direction of the acceleration. In one embodimen-t the acceleration responsive means may be electrically operable and comprise a pendulum and a plurality o~ contacts.
The con-tacts may be arranged to be successively con-tacted as the pivotal angle o~ the pendulum increases to be responsive to the amplitude of the acceleration; or -they may be disposed in a plane abou-t the pendulum to be responsive -to the direction of the acceleration. Alternatively, in another embodiment, a plurali-ty of accelera-tion responsive elements, such as pendulums, may be u-tilised, each o~ the elements being responsive -to acceieration o~ a prede-termined magni-tude or direction.

With such acceleration responsive means, a plurality of signal presence de-tector means may be provided, one ~'or each o~ the output signals of -the accelera-tion responsive means.
Similarly, a plurality of recording means, indica-ting m~ ans and second output signal responsive means may be provided, each being responsive -to one o~ the signal presence detector means By this means the magnitude o~ the acceleration responded to b~ the acceleration responsive means, or i-ts direc-t.ion, m~y be inde-pendently recorded and/or indicated.

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, The apparatus may have moun-ting means for mounting it in the vehicle. Connecting means may also be provi~ed for electrically connecting the apparatus to control apparatus and/or operating element~ o~ the vehicle. For example, the apparatus may have its own power source, or it may be connectible ~o a source of electrical power such as an accumulator in the vehicle) or the apparatus may be interconnected with the windscreen wipers or headlamps of the vehicle to render the accelera-tion responsive means or the signal presence detector means more sensi-tive.
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The components o~ the appara-tus may con~eniently be housed in a tamper-proof sealed housing. The apparatus may be ~`
self-sufficient or it may be removably receivable in a bracket which is mountable in a vehicle and which is connec-tible by sui-table connec-ting means to elements of the vehicle.
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The apparatus may have a region, e.g. on -the housing, on which a da-tum reference value may be recorded. This datum reference value may for example be the odometer reading o~ the vehicle or -the date of installation or of initial use, of the appara-tus.

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2Q The appara-tus may further have instruc-tions to the clrlver-exhorting and explaining to him how to drive sa~ely.

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The invention will now be described by way of examples, 7 _ , ~B~9SO

with reference to the accompanying drawings, in which~-Figure 1 shows a block diagram of an accelerometer according to the invention;

Figure 2 is a circuit diagram o~ an electrically operable embodimen~t of the accelerometer;

Figure 3 shows a sectional view of a pendulum for use with the embodiment of Figure 2;

Figure 4 shows an undernea-th plan view o~ -the pendulum o~ Figure 3; and ' ~

1~ Figure 5 shows a three-dimensional view of a housing for the accelerometer, sui-table for use in a vehicle.

Referring -to Figure 1~ the accelerometer is referred -to generally by reference numeral 10. The aocelerometer 10 comprises an acceleration responsive means - 8 - :

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12 connected to a signal presence detector 14. The presence detector 14 in turn drives a disabling means 16 and a -timer 18. The output of -the disabling means 16 is connected to a recording means 20 and an indicating "
means 22. ~he accelerometer 10 ~urther includes a source of power 24 and a test means 26 for testing the op- `
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eration of the accelerometer 10. I~ the accelerometer 10 `
` is for use with a motor vehicle, then it ~urther comprises a means 28 for inter-connecting the components of the `
accelerometer 10, to in~teract with the vehicle's controls.

In operation, the acceleration responsive means 12 responds to acceleration to emi-t a signal to the signal presence detector 14 when i-t is actua-ted. The acceleration responsive means 12 is such that it only emits a signal i~
the acceleration which it responds to is of a pre-determined ma~nitude. In this manner the output o~ the ; acceleration responsive means is quant.ised in a binary ~orma-t, i.e. either ON or OFF.

The presence de-tector 14 processes the signal which it receives ~rom the acceleration responsive mean~
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12 and if the signal is continuously present ~or a pre-determined time duration`it emits a signal to the disabl:lng means 16 and the timer 18. This time duration is variable.
~he timer 18 aggregates the amount o~ time that a signal .
~5 is emitted ~rom the presence detec-tor, i.e. the amount o~
time in excess of the presence time duration that -the acceleration responsive means is actuated.~ On receipt o~

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a signal from the presence detector 14, the disabling means 16 activates the recording means 20 and the indicating means 22. It then disables the recording means 20 and the indica-ting means 22 for a predetermined time dura-tion by not emitting an activation signal during this period i~ subsequent signals are received ~rom the presence detector during this period. This time duration is also variable.

The recording means may be any suitable means, such as a counter, which counts the number of activation signals it receives; a camera; or the like. Similarly the indicating means 22 may give a visual and/or audible indicati~g signal. It may accordingly be a lamp, a a hooter, buzzer, a loudspeaker,/or the like.

If the accelerometer 10 is moun-ted in a vehicle, in order to sense the acceleration experienced by the vehicle, the accelerome-ter may be interconnected and interac-t wi-th the vehicle's controls. In one embodiment, activation of the lights or windscreen wipers of the ~0 vehicle tnteracts with the presence detector 14 to decrease the presence time duration, rendering the accelerometer more sensitive.
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The operation o~ the accelerometer is tes-ted by activa-ting the test means 26. The test means 26 then , emits a signal of sufficient duration to the presence detec-tor 1~. If the accelerometer 10 is operating cornectly ' s~

- then the timer 18, any other recording means 20 and the indicating means will all be activated. The test means 26 may further disable the -timer 18 and the o-ther recording means 20 so tha-t they are not activated.

It is to be understood that the above elements of the accelerometer 10 may be greatly varied without departing from the spirit or the scope of the invention.
For example, the accelerometer may be operable by any suitable means - mechanically, hydraulically or pneumatically, but preferably electrically. Further, the acceleration responsive means 12 may be such as to emit a plurality of signals depending on the charactèr of -the acceleration.
In this event, a corresponding number of presence detectors 14 may be provided ~or each signal, each o~ -the presence ; 15 detectbrs having their own associated disabling means 16, -timers 18 and recording means 20. Only one indicating means 22 may be provided, actuable by a signal ~rom an~ of the signal paths provided by the presence detectors.

Referring to Figure 2, the circuit diagram of a par-ticular electrically operable accelerometer 10 is shown. The various sections of -the circuit corresponding to the elements of the block diagram o~ Fi~ure 1 are corre~-pondingly numbered. The ~arious elements are no~ con sidered.
, The circuit is powered by a power source 2~ com-prising a 6 ~olt battery 30. A voltmeter 32 is connected ~, . :. ,: , .. .. .

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across the battery 30, via a push-button switch 3~ for checking the EMF of the battery 30. The voltmeter 32 and switch 3~ ~orm par-t o~ the ~est means 26.

The acceleration responsive means 12 comprises a pendulum 36 which is pi~otal to form a bridge between the battery 30 and the presence detector 14. The pendu-lum 36 is indicated in more detail in Figure 3 and 4, and will be considered hereina~ter. ~ -two-pole switch 38 and a push-button switch ~0 are provided to disconnect the pendulum 36 and by-pass it.

The presence detector 14 comprises a series net-work o~ a variable resistance 42 and a capacitor L~4, their junc-tion connec-ted to the base L~6.1 o~ a transistor L~6~
The contact ~6.1 o~ the pendulum 36 is connec-ted to the resistance L~2. A further discharge resis-tance 48 is connected in parallel with the capaci-tor to ground~ The collector 46.2 o~ -the transistor 46 is connec-ted ~ria biassin~
resistances 50 and 52 to the positive supply o~ the battery 30. Their junction is connec-ted to the timer 18 and the disabling means 16. The timer 18 is ~urther connected via a normally closed isolating switch 5~ to the posltive supply.

The disabling means 16 comprises -two in-ter-connected transistors 56 and 58, -the bases and -the collectors o~ the two transistors being connected. The emitter o~ the transistor 56 is connected via a safe-ty ` resistance 60 to the junction between a capacitor 62 and .
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- a variable resistance 64, the resis-tance 64 and capacitor 62 being serially connected across the power supply 24.
The base of the transis-tor 56 comprises -the input to the disabling means 16 and is connected, in parallel with the timer 18 to the junction 53 of the resistances 50 an~ 52. The emit-ter of the transi~tor 58 is connected via a safety resistance 66 -to earth and to the base o~ a switching transistor 68. The emit-ter of this transistor is earthed, the collector forming the output 70 oE the disabling means, 16.
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The output 70 oE the disabling means 16 is connected to one terminal of -the counter 20, the o-ther end o~ which is connected via a normally closed isolating switch 72 to the positive supply. The counter 20 is electro magn~tically operated.

The output 70 is also connected to -the indicating means 22. The indicating means 22 has a light emitting diode 74 and a coil driven loudspeaker 76. The operation o:E the LED 74 and -the loudspeaker 76 is controlled by a circuit having two transistors 78.1 and 78.2 connected a~
an oscillator, with a capacitor 80 pro~idin~ the necessar~
~eedback. The con-trol circuit also includes a tl~ling network provided by a capacitor 82 and -three resi~tances 8~,1, 84.2 and 84.3~ A ~urther.inter:Eace resis-tance 86 ~5 and diode 88 are connected to the outpu-t 70 as shown.

A further resistance 90 is connected5 via a . .
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normally open switch 92 across the variable resistance 42 of the presence detector 14. The switch 92 is inter-connected with the windscreen wiper and/or headlamps of a vehicle (no-t shown) in which the accelerometer lq~s installed.

The voltmeter 32 and switch 34, the switches 38 and 40, and the switches 54 and 72 comprise the test`
means 26 o~ Figure 1.

In normal operation9 when the pendulum 36 is actuated, in response to inertial accelerative ~orces, i-t engages the contac-t 36.1 and the capacitor 44 starts char~ing. I~ -the pendulum 36 is actuated for a su~ficien-t period of time, determined by the relevant values o:~ the resis-tances 44 and 48, the capacitor 44, the base-emi-tter resistance of -the transistor 46 and the switch~on voltage of the transistor, the capacitor 44 is su~iciently charged - and the transistor 46 switches ON. This period is o~ the to 200 order o~ 10/milliseconds.

The voltage at the ~unction point 53 drops, actlvating the timer 18. ~he -timer 18 r~cords accumu-- ~ativ`ely -the amoun-t o~ time the -translstor 46 remain~
ON, i.e. the total`time in~ excess o~ the presence time duration that the pendulum is actuated.

Further, as the ~oltage at the junction poin-t 53 drops below the supply voltage, the transistor 56` and ~ ~ - 14 - ~ ~

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subsequently the -transistors 58 and 68 are switched ON.
The capacitor 6?, which was charged to the suppl~ voltage then discharges to earth through the resistance 60 (which is of a low value) and the transis~ors 56, 58 and 68.
As the -transistor 56 is now reverse biased, it switches OFF, switching the other two transistors 58 and 68 also OFF.
As this transistor 56 will remain reverse biased, even i~
the transistor 46 is ON~ until the capacitor 62 has been charged ramp-wise sufficiently through the resistance io 64. The disabling means 16 accordingly reacts to a signal from the presence detector 14 and then does not react and isolates -the counter 20 and the indicating means 22 for a time duration determined by the resistance 6L~ and the capa-ci-tor 62. This period is aboùt 2 seconds.

When the -transistor 68 switches on momentarily in response to an initial signal from the presence de-tector 14, a current pulse ~lows through the counter 20 activating i-t and increasing the count by 1.

Also, when -the transis-tor 68 switches ON, the capacitor 82 discharges through it, and via the resistance ~6 and the d.lode 88. The transis-tors 78.1 and 78.2 are aecor-~
dingly enabled, acti.ng as an oscillator with a :Erequelncy:
determined by the capaoitor 80 and the inductance o:E the coll o~ the loudspeaker 76. The loudspeaker 76 accordingl~
~5 emits ~ noise and the LED 74 glows. The capacitor 82 however charges up through the resistances 84.1 and 84.2 until the translstor 78.1 is no longer forwardly biased.

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The indicating means 22 is then de-acti~ated'until it receives a further pulse from the disabling means 16. The indicating means 22 is accordingly activated ~or about 1 second.

To test the accelerometer 109 the switch 38 is operated to remove t~ pendulum 36 from the circui-t. The switches 54 and 72 may be linked to the switch 38 to be simultaneously opened -to isolate the timer 18 and the counter 20. The switch 38 may be lockable so that only authorised persons may test the 'accelerometer 10. ~he press-button switch 40 is closed, providing the presence detec-tor with an activating signal. I~ the circuit is operating correctly, the loudspeaker 76 and the light 74 are ope'rated. ~ ' Referring to Figures 3 and 4, an embodiment o:~
the acceleration responsive means 10 is shown having a pendulum 36 as its operative element, The pendulum 36 is electricàlly conductive and has a spherical formation 100 at~ its upper end. This ~ormation 100 is receivable in a cup shaped indentation 102 in a metal supp~rt plate ; ~ 104 so that the pendulum 36 is ~reely pivotable. ~ contac-t plate 36.1? spaced ~rom the support plate 104, is provided having an opening 108 in which the pendulum is receivable~
' ~he support plate 104 and the~contact plate 36.1 are both ~5 mo~m-ted on an insula-ting base board 106 which may conven-iently be part o~ a prin-ted circuit board. The contact plate 36.1 may be mounted by means o~ metal bol-ts 110. The .

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support pla-te 104 and the con-tact plate 36.1 are connected -to the circuit componen-ts shown in Figure 2 by wire connec-tors 112 or by circuit connec-tors printed on the base board 106.

If the pendulum 36 experiences an inertial force, it pivots away from its rest position. If the inertial Eorce is of a sufficient magnitude, the pendulum 36 engages the contact plate 36.1, Porming an electrical bri ~ g connection.

Figure 5 shows a housing 120 for the accelerometer 10. The housing 120 is sealed so that the counter and .
timer of the accelerometer 10 are tamper-proof. The '~
housing 120 has a mounting bracke-t 122 by means oP ~ich it may be mounted in a motor vehicle (not shown) utilising -the holes 124. Apertures 123 and 125 are provided in the Pornt wall 126 of the housing 120 so -that the reading 20.1 of the coun-ter and the LED 74 may be visible. A region 128 is also provided ~here a datum re~erence mileage ~, reading o~ the vehicle may be recorded. The Pront wall 126 fur-ther has ins-tructionsl~0 instruc-ting the driver o~
-the vehicle as -to safe drl~ing procedure.

By this means, an~`excessive acceleration o:E
the vehi¢le, due to excessive acceleration, braki~g or cornering, causes the pendulum -to be actuated, -thereby registering on the counter. Accordingly, Por each drlving error incurred by the drlver, the counter registers a .

so -count thereby recording the driving pattern of -the driver.

Further, as the pendulum is required to be activa-ted ~or a predetermined time durationt spurious operation o~ the pendulum not due to excessive driving of the vbhicle but due to resonant excitation of the pendulum are not acted on. This can ~or example occur when driving over a bumpy road. A further aspect is tha-t if the pendulum is activa-ted a number of times in a short time period, e.g. by~?the sharp application of the vehicle's brakes several times in a shor-t period~due to the disabling means only one "driving error" is recorded. I~ the vehicle undergoes the excessive acceleration for longer -than this disabled period, indicating excessive driving, then more than one error is recorded.

Accordingly, i:E a driver drives within a speed limit, e.g. an urban speed limit o~ 60 KM/H and he brakes excessively, the vehicle will be able -to come to a halt in the disabled time period, thereby registering only one error. However, if he exceeds this speed, and he ~o requires to brake excessively to come -to a halt, the pendulum will be actuated for longer than the disabled period and more than one error will be recorded. B~
this means an indirec-t relationship be-tween the speed o~ the vehicle and the driver's driving pa-ttern 1s obtainefl~

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Claims (9)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for detecting and recording abuse of a motor vehicle, including an acceleration responsive means which provides a first output signal responsive to acceleration of the vehicle above a preset level;
a signal presence detector means connected to the acceleration responsive means providing a second output signal when the first output signal persists for a first predetermined period of time;
a recorder;
means responsive to the second output signal for actuating the recorder and then preventing the recorder from recording any further signals during a second period of time substantially greater than the first period of time.

2. Apparatus as claimed in Claim 1, in which the signal presence detector means continues to provide the second output signal until the first output signal is removed; and the means responsive to the second output signal is auto-matically reset at the end of each second period of time.

3. Apparatus as claimed in Claim 1, in which the signal presence detector means is automatically reset at the end of each first period of time such that the first period of time is automatically re-started; and the means responsive to the second output signal is also automatically reset at the end of each second period of time.

4. Apparatus as claimed in Claim 1, in which the signal presence detector means is variable to vary the first time period.

5. Apparatus as claimed in Claim 1, in which the means re-sponsive to the second output signal is variable to vary the second time period.

6. Apparatus as claimed in Claim 1, in which the acceleration responsive means is responsive to linear and centripetal inertial forces.

7. Apparatus as claimed in Claim 1, which includes visual indicating means and the means responsive to the second output signal also activates the indicating means.

8. Apparatus as claimed in Claim 1, which includes audible indicating means and the means responsive to the second output signal also activates the indicating means.

9. Apparatus as claimed in Claim 1, which includes test means for supplying an artificial first output signal to the signal presence detector means to test the operation of the apparatus.