BACKGROUND OF THE INVENTION

THIS invention relates to a braking indicator device, a vehicle comprising a braking indicator device, and a method of operating one or more brake indicators/s of a vehicle during braking.

Most vehicles, for example, automobiles, trailers, motorcycles, watercrafts, or the like, include brake lights disposed at a rear of these vehicles. The brake lights, typically comprising light emitting diodes (LEDs), are configured to be turned on when the brake system or brake pedal of the vehicle is actuated thereby alerting a following driver that the vehicle is decelerating.

Although actuation of the brake lights indicate to a following driver that the vehicle is likely to decelerate, it seldom indicates, or more particularly differentiates, instances wherein the vehicle undergoes gentle deceleration (normal deceleration) or more importantly rapid deceleration (emergency deceleration), for example, in an emergency braking situation. The latter problem in particular often increases the risk of a rear collision between the vehicle and a following vehicle.

Systems and devices which indicate rapid deceleration of a vehicle, for example, by flashing the brake lights, or increasing the brightness of the brake lights, often do not take the effects of gravity and slope of the road, which the vehicle is travelling on, into account when indicating rapid deceleration of the vehicle thus leading to incorrect or undesirable results. However, systems and devices which do take gravity into account are often complicated, differently configured to the present invention, and typically require the use of at least two accelerometers to determine rapid deceleration conditions. It will be appreciated that these latter systems and devices are often difficult and costly to manufacture and install to vehicles, especially retrospectively. In addition, systems using two or more accelerometers are not as accurate in determining critical metrics used to determine emergency braking.

It is therefore an object of the present invention to address the abovementioned problems by providing a more accurate, simpler and cost effective way to indicate, or facilitate indicating, braking of a vehicle.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a braking indicator device connectable to a vehicle for facilitating indication of braking of the vehicle by way of one or more brake indicator/s, the device comprising: a deceleration determining module configured to: obtain a first deceleration measurement associated with the vehicle at a first pre-determined time after an initial actuation of a braking system of the vehicle is determined; obtain a second deceleration measurement associated with the vehicle at a second pre-determined time after the first pre-determined time; and determine a deceleration value in the direction of travel of the vehicle by subtracting the first deceleration measurement from the second deceleration measurement; a comparator module configured to compare the determined deceleration value in the direction of travel of the vehicle with a predetermined deceleration threshold thereby to determine if the vehicle is undergoing emergency/rapid deceleration or normal/gentle deceleration; and an output module configured to output a suitable emergency brake control signal to the one or more brake indicator/s if the vehicle is undergoing emergency/rapid deceleration and further configured to output a suitable normal brake control signal to the one or more brake indicators if the vehicle is undergoing normal/gentle deceleration.

The braking indicator device may further comprise: an accelerometer, disposed relative to the vehicle, wherein the accelerometer is configured to measure deceleration of the vehicle in the direction of travel of the vehicle; and a brake actuation determining means configured to determine actuation of the braking system of the vehicle. The braking indicator device may comprise a single accelerometer. The accelerometer may typically be a single axis accelerometer. However, in other example embodiments, the accelerometer may be a dual axis accelerometer.

The deceleration determining module may be configured to: obtain first and second deceleration measurements from the accelerometer; or obtain first and second deceleration measurements from a data processing unit associated with the vehicle.

The first pre-determined time may be selected to allow for electronic components of the braking indicator device to settle after powering up. In a preferred embodiment, the first pre-determined time may be between four and 10 milliseconds, most preferably four milliseconds, after the initial actuation of the braking system or it is determined that the braking system of the vehicle is actuated. It will be appreciated that the time between the initial actuation of the braking system and the first pre-determined time, should be a minimum as it is limited by the startup time of electronics associated with the device, e.g. the microcontroller, the settling time of the output of the accelerometer after power-up, or the like. It follows that this time may be reduced or increased depending on hardware used.

The first deceleration measurement may be an average of a plurality of measurements taken over a first measuring interval after the first predetermined time. The first measuring interval may be approximately 10 milliseconds.

The first deceleration measurement may be taken after at least one of the accelerometer and the brake actuation determining means have settled in taking measurements but before the braking system has been actuated sufficiently to decelerate the vehicle. The second pre-determined time may any time up to 50 milliseconds after the first measuring interval. Preferably, the second pre-determined time may be approximately 50 milliseconds after the first measuring interval.

Similarly to the first deceleration measurement, the second deceleration measurement may be an average of a plurality of measurements taken over a second measuring interval after the second predetermined time. Preferably, the second measuring interval may be 10 milliseconds.

The second deceleration measurement may be taken after it is determined, by way of one or both of the brake actuation determining means and the accelerometer, that the braking system of the vehicle has been substantially operated and/or the vehicle is experiencing substantial deceleration as a result of the braking system of the vehicle.

The output module may be configured to turn the brake light on immediately on actuation of the braking system of the vehicle for a predetermined period of time until the emergency or normal brake control signal is output.

The deceleration determining module may be further configured, in an iterative fashion until the braking system of the vehicle is not actuated or deactivated, to: obtain further deceleration measurements at predetermined intervals after output of the emergency or normal brake control signals respectively; and determine iterative deceleration values in the direction of travel of the vehicle by subtracting the first deceleration measurement from the further deceleration measurements. It will be appreciated that for each iterative determination of the iterative deceleration value, the comparator module and output module is operated in a similar fashion as hereinbefore described.

In one embodiment of the invention, the brake actuation determining means may be in communication with a pressure sensor or switch located on a master cylinder associated with the braking system thereby to determine actuation of a braking system of the vehicle. Instead, or in addition brake actuation determining means may comprise a pressure sensor or switch operatively connectable to a brake pedal, lever, or handle of the vehicle braking system thereby to determine actuation of a braking system of the vehicle, wherein operation of the brake pedal, lever, or handle actuates the braking system. Instead, or in addition, the brake actuation determining means may be in communication with the data processing unit of the vehicle thereby to determine actuation of the braking system of the vehicle therefrom.

The device may typically comprise a plurality of brake indicators, or is in communication with existing brake lights of the vehicle, or both. The brake indicators may comprise brake lights selected from one or more of incandescent light bulbs, fluorescent light bulbs, or light emitting diodes (LEDs).

It will be appreciated that the emergency brake control signal output by the output module may be arranged to operate the brake lights to brightly flash such that, in use, a following driver is alerted that the vehicle is undergoing emergency/rapid deceleration due to braking. Whereas, the normal brake control signal output by the output module may be arranged to operate brake lights to dimly glow such that, in use, a following driver is alerted that the vehicle is undergoing normal/gentle deceleration. In an example embodiment, the normal brake control signal may be arranged to operate the brake lights to flash with a high frequency so as to appear to be turned on albeit dimmer than if the emergency brake control signal was applied thereto. The normal brake control signal may be arranged to operate the brake lights to enter a pulse width modulation loop, for example, with a 50% duty cycle.

The braking indicator device may be arranged to be calibrated when powered up for a first time thereby at least to obtain a reference deceleration measurement from the accelerometer when the vehicle is on a substantially level surface so as to account for variations in measurements obtained for different accelerometers.

In one embodiment of the invention, the pre-determined deceleration threshold may be a function of at least a sensitivity associated with the accelerometer, and a coefficient of static friction associated with tyres of the and/or a road surface.

The braking indicator device may further comprise a processor, wherein the processor comprises the deceleration determining module, the comparator module, and the output module.

The braking indicator device may be configured to be retrospectively attachable to a vehicle by a suitable person, for example, a technician. Instead, or in addition, the braking indicator device may be integral with a vehicle.

According to a second aspect of the invention there is provided a method of operating one or more brake indicator/s associated with a vehicle during braking, the method comprising: obtaining, by way of a deceleration determining module, a first deceleration measurement at a first pre-determined time after an initial actuation of a braking system of the vehicle is determined; obtaining, by way of the deceleration determining module, a second deceleration measurement at a second pre-determined time after the first pre-determined time; determining, by way of the deceleration determining module, a deceleration value in the direction of travel of the vehicle by subtracting the first deceleration measurement from the second deceleration measurement; comparing, by way of a comparator module, the determined deceleration value in the direction of travel of the vehicle with a predetermined deceleration threshold thereby to determine if the vehicle is undergoing emergency/rapid deceleration or normal/gentle deceleration; and outputting, by way of an output module, a suitable emergency brake control signal to the one or more brake indicator/s if the vehicle is undergoing emergency/rapid deceleration or outputting a suitable normal brake control signal to the one or more brake indicator/s if the vehicle is undergoing normal/gentle deceleration.

The method may further comprise determining, by way of a brake actuation determining means, actuation of the braking system of the vehicle, prior to the step of obtaining the first deceleration measurement.

The steps of obtaining the first and second deceleration measurements may comprise: obtaining first and second deceleration measurements from an accelerometer; or obtaining first and second deceleration measurements from a data processing unit associated with the vehicle.

As hereinbefore mentioned, the one or more brake indicator/s may comprise brake lights selected from one or more of incandescent light bulbs, fluorescent light bulbs, or light emitting diodes (LEDs). The method may further comprise substantially immediately switching the brake lights on upon determining the initial actuation of the braking system of the vehicle, typically, at the reduced brightness of normal braking conditions.

The method may also further comprise: obtaining further deceleration measurements from the accelerometer at predetermined intervals after output of the emergency or normal brake control signals respectively; determining iterative deceleration values in the direction of travel of the vehicle by subtracting first deceleration measurement from the further deceleration measurements; comparing the determined iterative deceleration values in the direction of travel of the vehicle with the pre-determined deceleration value; and outputting the emergency brake control signal or normal brake control signal if the vehicle is undergoing emergency deceleration or normal deceleration respectively.

The steps of obtaining further deceleration measurements, determining iterative deceleration values, comparing and outputting the emergency brake control signal or normal brake control signal may be repeated in a loop fashion until it is determined that the braking system of the vehicle is not actuated or deactivated.

The emergency brake control signal may cause the brake lights to brightly flash such that, in use, a following driver is alerted that the vehicle is undergoing emergency/rapid deceleration due to braking. The normal brake control signal may cause the brake lights to dimly glow such that, in use, a following driver is alerted that the vehicle is undergoing normal/gentle deceleration. It will be appreciated the "dim" in this context is the normal brightness level of a vehicle's brake lights upon operation whereas the brightly flashing lights are brighter than the aforementioned operation.

According to a third aspect of the invention, there is provided a vehicle comprising a braking indicator device as hereinbefore described.

According to a fourth aspect of the invention, there is provided a system for facilitating indication of braking of a vehicle, the system comprising: a braking indicator device substantially as hereinbefore described; and at least one brake indicator operatively connected to the braking indicator device, the at least one brake indicator being arranged to indicate to a following driver whether the vehicle is undergoing emergency/rapid deceleration or normal/gentle deceleration.

The at least one brake indicator may typically comprise a brake light. In an example embodiment, the brake indicator may comprise a plurality of brake lights, for example, light emitting diodes (LEDs) operatively mountable to a vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a functional block diagram of a braking indicator device in accordance with an example embodiment;

Figure 2 shows a schematic diagram of the braking indicator device of

Figure 1 in accordance with an example embodiment; Figure 3 shows another schematic diagram of the braking indicator device of Figure 1 in accordance with a preferred example embodiment;

Figure 4 shows a diagram a vehicle indicating slope of a surface on which the vehicle travels;

Figure 5 shows a flow diagram of a method of operating at least one brake indicator of a vehicle during braking; and

Figure 6 shows another flow diagram of a method of operating at least one brake indicator of a vehicle during braking functional, in more detail.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of an embodiment of the present disclosure. It will be evident, however, to one skilled in the art that the present disclosure may be practiced without these specific details.

Referring to Figures 1 to 4 of the drawings, a braking indicator device in accordance with an example embodiment is generally indicated by reference numeral 10. The brake indicator device 10 is typically connectable to or in a vehicle such as an automobile or car 12 to at least facilitate indicating braking or deceleration due to braking of the vehicle 12 to a following driver. This is done preferably by operating at least one brake indicator of the vehicle 12, or a separate brake indicator of the device 10, or both.

The at least one brake indicator may typically comprise a brake light. In a preferred example embodiment, the brake indicator comprises a plurality of brake lights, for example, incandescent light bulbs, fluorescent light bulbs, or preferably light emitting diodes (LEDs) 9 conveniently disposed at a rear of the vehicle 12. It is important to note that the LEDs 9 are run at very low power during normal braking, and output similar brightness levels to normal braking lamps. During emergency braking, they ramp up to a higher power state and flash brightly. One cannot use standard LEDs in this product as they are not powerful enough in emergency braking conditions. It follows that the LEDs 9 can accommodate or may be modified to accommodate a brighter level of operation.

The brake indicator device 10 typically comprises a brake actuation determining means 14 configured to determine actuation of a braking system of the vehicle 12. The means 14 may conveniently comprise or may be in communication with a suitable sensor or switch, for example, a pressure sensor or switch operatively connected to a brake pedal of the vehicle 12 thereby to determine when the driver of the vehicle 12 depresses the brake pedal and hence actuates the braking system of the vehicle 12. It will be appreciated that in order example embodiments, the means 14 may be connectable to a data processing unit or onboard computer system of the vehicle 12 to determine when the braking system of the vehicle 12 is actuated. In a preferred example embodiment, the brake actuation determining means 14 is in communication with a pressure switch located on, for example, a master cylinder associated with the braking system thereby to determine actuation of a braking system of the vehicle12. The switch is typically already installed in most vehicles. The power is supplied through this switch to the device 10.

For brevity, operation or depression of the brake pedal of the vehicle 12 will be understood to mean operating or actuating the braking system of the vehicle 12.

In a preferred embodiment, the actuation of the brake pedal powers up the device. Once powered up, the device operate as described herein. ln any event, the device 10 further comprises an accelerometer 16 disposed relative to the vehicle 12 to measure deceleration of the vehicle 12 in the direction of travel of the vehicle 12, for example, in the direction of the Z-axis as illustrated in Figure 4. The accelerometer 16 is typically a single axis accelerometer, which is sufficient for the present invention. However, in other example embodiments the accelerometer 16 can be a dual or a dual axis accelerometer. In the present example embodiment, the Z-axis of the accelerometer 16 is parallel to a road surface 18.

It will be appreciated that certain components of the device 10 are provided on a printed circuit board (PCB) associated with the device 10. The PCB layout of the present device 10 has the Z-axis of the accelerometer 16 pointing in the direction of travel of the vehicle 12 (not counting sideways movement of the car). For a dual axis accelerometer, an X-axis is perpendicular to the road surface 8, as illustrated in Figure 4.

The device 10 also comprises a processor 20 in communication with the brake actuation determining means 14 and the accelerometer 16. The communication is typically electronic communication by way of wires. However, this communication may be wireless, e.g., by way of Bluetooth, or the like. The processor 20 may include a machine-readable medium, e.g. memory in the processor 20, which carries a set of instructions to direct the operation of the device 10. It is to be understood that the processor 20 may be one or more microprocessors, controllers, or any other suitable computing device, resource, hardware, software, or embedded logic.

The device 10, particularly the processor 20, comprises a plurality of modules corresponding to certain desired tasks to be performed by the device 10. It is to be noted that, for the purposes of this specification, the term "module" includes an identifiable portion of code, computational or executable instructions, data, or computational object to achieve a particular function, operation, processing, or procedure. However, a module need not be implemented in software; a module may be implemented in software, hardware, or a combination of software and hardware.

In particular, the processor 20 comprises a deceleration determining module 22 configured to obtain a first deceleration measurement from the accelerometer 16 at a first pre-determined time after an initial actuation of the braking system of the vehicle 12 is determined by the means 14. The first pre-determined time is typically any time up to 10 milliseconds (the shorter this time the better) after it is determined that the brake pedal has been depressed.

As previously mentioned, the means 14 determines the initial actuation of the braking system by way of the pressure sensor or switch attached to the brake pedal or the master cylinder of the braking system as hereinbefore described. It will be understood that the device 10 is configured to be powered only when the brake pedal is depressed, or more particularly when the device determines that the brake pedal is depressed by way of the means 14.

In some example embodiments, the means 14 is provided as a module in the processor 20 to obtain signals from the master cylinder of the vehicle 12 braking system thereby to determine if the braking system has been actuated or not.

In any event, in a preferred example embodiment, the first pre-determined time is 4 milliseconds. This predetermined time is selected conveniently so as to allow an output signal from the accelerometer 16 to stabilise as well as to allow a clock associated with the processor 20 to settle, typically before the braking system has had time to engage.

This first-predetermined time should be as soon as possible after actuation of the braking system is determined. However, if this is too soon, the bandwidth of the accelerometer 16 has to be increased and noise due to vibration becomes more significant. To reduce errors due to transients and effects of vibration of the vehicle 12 on the road surface 18, the first deceleration measurement is an average of a plurality of measurements, for example, eight measurements taken over a first measuring interval, for example, approximately 10 milliseconds after the first predetermined time.

It will be appreciated that the first deceleration measurement is a voltage measurement, V _Z1 , from the accelerometer 16, for example, the measurement in the z-direction of the accelerometer 16 before the braking system has started to decelerate the car 12.

The first deceleration measurement is due to the gain of the accelerometer and the effect of gravity (a function of the slope of the road). In particular, the first voltage measurement V _Z1 may be given by the following equation: zi = VzRef + (X.sinO), where:

V _ZRef is a reference voltage obtained during calibration of the accelerometer (discussed below);

Θ corresponds to the angle of slope of the road surface 18 as indicated in Figure 4; and

X is a constant of 458mV corresponding to the sensitivity of the accelerometer 16 in one particular example embodiment.

From this, a more accurate value of the slope of the road is possible as sinO varies quite a bit as Θ approaches 0 or a flat surface. With a 10 bit A/D on the processor 20, and a sensitivity of 458mV/g, this allows for a higher signal to noise ratio as opposed to using an accelerometer transverse, particularly perpendicular, to the road surface 18.

It will be noted that the first deceleration measurement is conveniently taken after the electronics for measurement, for example, the accelerometer 16 for one has settled but before the brake pedal has been pressed sufficiently to decelerate the vehicle 12. The deceleration determining module 22 is further configured to obtain a second deceleration measurement from the accelerometer 16 at a second pre-determined time after the first pre-determined time. The second predetermined time may be any time up to 50 milliseconds after the first measuring interval. In a preferred example embodiment, the second predetermined time is approximately 50 milliseconds after the first measuring interval.

Similarly, as described above, the second deceleration measurement is an average of a plurality of measurements, for example, eight measurements taken over a second measuring interval, for example, approximately 10 milliseconds, after the second predetermined time.

The second deceleration measurement is a second voltage measurement V _Z2 from the accelerometer 16 when the brake pedal is fully depressed, or in the process of being depressed such that the vehicle is experiencing deceleration due to the braking system, at which or just after the car is decelerating at a maximum in the direction of travel. The second voltage measurement V _Z2 may be given by the following equation: z2 = _ZR ef + (458mV.sin9) + V _DE c, where:

V _DEC corresponds to the perceived deceleration of the car 12 in the direction of travel.

It will be appreciated that the second deceleration measurement is taken after the brake pedal has been substantially or fully depressed and/or the vehicle 12 is experiencing substantial deceleration due to the actuation of the braking system of the vehicle.

The module 22 is further configured to determine a deceleration value V _DEC in the direction of travel of the vehicle by subtracting the first deceleration measurement V _Z1 from the second deceleration measurement V _Z2 . In terms of the voltage measurements, as described above, from the accelerometer 16:

The processor 20 also comprises a comparator module 24 configured to compare the determined deceleration value V _D EC in the direction of travel of the vehicle 12 with a pre-determined deceleration threshold K thereby to determine if the vehicle 12 is undergoing emergency/rapid deceleration or normal/gentle deceleration.

The predetermined deceleration threshold K may be a constant which is a function of the sensitivity of the accelerometer 12 and coefficient of static friction of the tyres of the vehicle 12 and/or the general road surface. In an example embodiment, for low cost economy tyres with a coefficient of static friction of 0.9, for example, the constant K, typically experimentally determined, would be set to 60% of this. Therefore, in this particular example embodiment, the accelerometer 16 has a sensitivity of 458mV/g, therefore K = (0.6).(0.9).(458mV)

As mentioned, the constant K may vary depending on the accelerometer used and the type of tyres used, for example, economy, intermediate sport or sport tyres. The different tyres have different braking thresholds, for example, the economy tyres have a low threshold, the intermediate tyres have a medium threshold, and sport tyres have the highest braking threshold.

The processor 20 also comprises an output module 26 configured to output a suitable emergency brake control signal to the LEDs 9 if the vehicle 12 is undergoing emergency/rapid deceleration and further configured to output a suitable normal brake control signal to the LEDs if the vehicle 12 is undergoing normal/gentle deceleration. The emergency brake control signal output by the output module 26 operates the LEDs 9 to brightly flash such that, in use, a following driver is alerted that the vehicle 12 is undergoing emergency/rapid deceleration due to braking or operation of the braking system of the vehicle 12 by the driver thereof.

The normal brake control signal output by the output module 26 operates the LEDs 9 to dimly glow such that, in use, a following driver is alerted that the vehicle 12 is undergoing normal/gentle deceleration due to braking. By "dimly glow", is meant that the brightness of the LEDs 9 is dim in comparison to the flashing brightness, but comparable to normal brake light indicators on other vehicles. The normal brake control signal may operate the LEDs 9 to flash with a high frequency so as to appear to be turned on albeit dimmer than if the emergency brake control signal was applied thereto. The normal brake control signal may operate the LEDs 9 to enter a pulse width modulation loop with, for example, a 50% duty cycle.

In addition, the output module 26 is configured to turn the LEDs on immediately on actuation of the braking system of the vehicle 12 until the emergency or normal brake control signal is output, for example, around approximately 74 milliseconds after activation of the braking system. During this operation, the LEDs 9 are advantageously running at full power. If there is no emergency they become dimmer. The initial bright flash of the LEDs 9 is perceivable by following drivers and may advantageously help in shortening the reaction time of the following driver in both emergency and in normal braking conditions. Another benefit of the present invention is that in emergency situations, the LEDs 9 illuminate much brighter than in normal braking conditions.

As previously indicated, the device 10 may be configured or calibrated the first time that it is operated at least to obtain and to permanently store V _REF thereby at least to account for variation of voltages from accelerometers from different batches. This is the tolerance on the specified average of the accelerometers, and not an operating condition. ln any event, a flag in EEPROM of the device 1 0 is programmed when the FLASH memory is programmed. This flag indicates that the device 10 needs calibration. Ideally, calibration takes place when the device 10 is installed in the car 1 2 and powered for the first time on a flat surface. Preferably, this will be at the place of manufacture of the vehicle.

It will be appreciated that the deceleration determining module 22 may be further configured, in an iterative fashion until the brake pedal is released, or it is determined that the brake pedal is released, to obtain further deceleration measurements from the acceierometer 16 at predetermined intervals after output of the emergency or normal brake control signals respectively.

The module 22 is also configured to determine iterative deceleration values VDEC in the direction of travel of the vehicle 12 by subtracting first deceleration measurement from the further deceleration measurements in a similar fashion as hereinbefore described.

It follows that for each iterative determination of the iterative deceleration value, the comparator module 24 and output module 26 are operated in a similar fashion as also hereinbefore described.

A second acceierometer pointing perpendicular to the road surface or even a second measurement in the x-direction perpendicular to the road (from the dual axis acceierometer 16, for example) may be used to determine pot-holes, etc. In any event, the signal output (in the x-direction) from a downward pointing acceierometer may be accurately determined. After measurement, any difference between the calculated and measured values must be due to a movement of the vehicle 12 perpendicular to the road surface, indicating potholes, etc. In this case, a threshold may be set, above which the emergency situation is not initiated. This voltage measurement V _X from the acceierometer 16 perpendicular to the road may be given by the following equation: V _x = VXREF + 458mV.lcos9l,

since V _XRE F and cos are known, any deviation of this voltage may be used to predict transient movement along the x-axis.

In any event, there are further components of the device 10 which are present, for example, provided in the PCB. For example, referring to Figure 2, component 30 is a 3.3V regulator, as the accelerometer 16 in the present example embodiment is only rated to 3.6V. The A D converter on the microcontroller 20 has this regulated voltage (also its Vcc) as a reference, so this also helps in maintaining the Og point. In other words, if the output of the regulator is 3V, then the mid-point identified by the A/D is 1.5V. Also, since the output of the accelerometer 16 is ratiometric, the Og (no acceleration) voltage will be 1.5V. The same applies if the output of the regulator is at any other value. This is an important feature, because obviously regulators are not perfect and will vary with temperature and age and batch etc.

Capacitors 32 and 33 are AC decoupling capacitors for the regulator.

Regulator 34 is configured to operate as a constant current source. Particularly with high powered LEDs 9, with a change in temperature the impedance can change dramatically. Driving them with a constant current source lengthens their life as well as providing a more repeatable optical output.

Resistor 36 sets the constant current source: the voltage across the resistor is nominally 1.25V, therefore the source is programmed to l=V/R=1.25V/3.30hm = 380mA. The LEDs 9 are subject to a de-rating curve, therefore they are not driven at their maximum current. Although the ambient temperature is expected to be roughly tolerable to humans (as the device is inside the vehicle where the passengers are), this is not guaranteed, and there is a safety factor included. Capacitors 38 and 39 set the output bandwidth of the signals to approximately 100Hz. This lowers the noise on the output (vs having no capacitors) and rejects higher frequency transients such as vibrations due to the roughness of the road surface. It should be noted that these values are not set in stone, they are merely given by way of example. Increasing the capacitance reduces noise and effects of vibrations, but it also reduces the settling time of the signals and the turn-on time of the accelerometer 16, so a balance is needed.

ISP (In System Programming) port 40 for programming the microcontroller 20. Whereas ports 42 and 44 are general purpose ports for connection to other devices if need be. Resistor 46 is a current limiting resistor for driving transistor 48. Transistor 48 is an NPN transistor which allows the current from Regulator 34 to pass through the LEDs 9.

Another, preferred, example embodiment of the electronic layout of the device 10 is illustrated in Figure 3. The embodiment in Figure 3 is similar to the embodiment illustrated in Figure 2 and therefore similar parts will be indicated by the same reference numerals. However, notably, the example embodiment illustrated in Figure 3 comprises predominantly automotive parts rated for automotive applications.

In any event, the example device 10 illustrated in Figure 3 is powered via a power connector 102, which is connected to an electrical supply which ordinarily supplies power to the brake lights of the vehicle 12. Capacitor 104 is a low pass filter intended to reduce the amplitude of any transients on the supply voltage. For larger transients, tranzorb 106, reduces its impedance as the supply voltage rises. Voltage regulator 108 provides 5V to the accelerometer 16 and microcontroller 20. A low pass filter 1 10 is provided for the output of the voltage regulator 108.

The microcontroller 20, receives the deceleration signals from the accelerometer 16. An output from the accelerometer 16 is also low pass filtered, to reduce the effects of higher frequency vibrations. Pin 112 of the microcontroller 20 functions as a programming pin as well as an enable output for the LED drivers. Pins 1 14, 1 16, and 1 18 also form part of the programming interface.

Three identical arrangements of LEDs 9 are provided with LED drivers 120, each arrangement has three LEDs each. This design modification is more aesthetically agreeable than the embodiment illustrated in Figure 2, the latter mentioned incidentally being a prototype example of the invention. The LED arrangements comprise low pass filters 122 to prevent oscillations on the LED drivers 120. By setting a logic high on pin 1 12, pin 124 of the LED driver 120 passes current through resistor 126 and biases transistor 128. A current sense resistor 30 is used to detect the LED current, providing a feedback loop which allows the LED driver 120 to set a constant current through the LEDs 9.

The device 10 may conveniently be configured to be attachable to the vehicle 12 by a technician, or the like. The technician may connect the pressure switch to the brake pedal of the car 12 as hereinbefore described. Instead, or in addition, the technician may simply replace an existing third brake light on the vehicle 12 with LEDs 9 of the device 10 and use the pressure switch already installed in the vehicle 12 to obtain information indicative of actuation of the braking system thereof.

In any event, the technician may connect the output module 26 to the LEDs 9 in such a way as to control the LEDs 9. In certain example embodiments the module 26 can be connected directly to the LEDs 9 or it can be connected to control the power supply to the LEDs.

The technician may place the PCB of the device 10 in the car 12 such that the accelerometer 16 z-direction or measuring direction is parallel to the road surface 18.

It will be appreciated that the LEDs 9 are the vehicle's factory fitted LED's. However, the LEDs 9 could be retrospectively attachable to the vehicle 12 and, together with the device 10, could form part of a system which may be attachable to the vehicle 12.

In some example embodiments, the device 10 could be integrated with a vehicle 12 during manufacture thereof. In this regard, it will be appreciated that the on-board computer of the vehicle 12 may be configured to provide the modules as hereinbefore described, to receive deceleration measurements from suitable components in the vehicle as well as to output the control signals to the brake lights of the vehicle 12. It will be evident to those skilled in the art that one may put the invention into practice in a vehicle in a plurality of different ways. However, these different embodiments may not detract from the invention disclosed herein.

Example embodiments will now be further described, in use, with reference to Figures 5 and 6. The example methods shown in Figures 5 and 6 are described with reference to Figures 1 to 4, although it is to be appreciated that the example methods may be applicable to other devices (not illustrated) as well. The methods 5 and 6 may be effected by the device 10 by way of a set of computer readable instructions stored on a computer readable medium associated with the device 10, particularly the processor 20.

Referring to Figure 5 of the drawings where a flow diagram of a method of operating brake lights 9 of a vehicle 12 during braking is indicated by reference numeral 50. The method 50 initially determines, at block 52, actuation of the braking system of the vehicle 12 by way of module 14 as hereinbefore described.

The method 50 then comprises obtaining, at block 54, a first deceleration measurement, V _Z , from an accelerometer 16 at the first pre-determined time by way of the module 22 as hereinbefore described.

The method 50 also comprises obtaining, at block 56, a second deceleration measurement, V _Z2 , from the accelerometer 16 at the second pre-determined time also by way of the deceleration determining module 22 as hereinbefore described.

The method 50 further comprises determining, at block 58, a deceleration value, V _DEC , in the direction of travel of the vehicle 12 by way of the module 22 as hereinbefore described.

The method 50 also comprises comparing, at block 60 by way of the module 24, the determined deceleration value V _D EC in the direction of travel of the vehicle 12 with a pre-determined deceleration threshold K as hereinbefore described to determine if the vehicle 12 is undergoing emergency/rapid deceleration or normal/gentle deceleration.

In the present example embodiment, if V _DEC is greater than the deceleration threshold K, or in other words an emergency braking condition, the method 50 comprises outputting, at block 62 by way of module 26, a suitable emergency brake control signal to the LEDs 9. It will be noted that the emergency braking condition is characterised by the driver of the vehicle 12 "slamming" or aggressively pressing on the brake pedal of the vehicle 12.

Similarly, if V _DE c is less than the deceleration threshold K, or in other words normal braking condition, the method 50 comprises outputting, at block 64 by way of module 26, a suitable normal brake control signal to the LEDs 9. The normal braking condition is characterised by the driver of the vehicle 12 gently depressing the brake pedal of the vehicle 12.

It will be noted that the steps 56 to 64 of the method 50 may be repeated substantially similarly as hereinbefore described as long as the brake pedal is depressed. However, for these further iterations it will be noted that the method 50 comprises determining iterative deceleration values, for comparison with the deceleration value K as hereinbefore described, by subtracting the first deceleration measurement from the further deceleration measurements as hereinbefore described. Referring now to Figure 6 of the drawings where a flow diagram of a method in accordance with an example embodiment is generally indicated by reference numeral 70. The method 70 is similar to the method 50 and therefore similar steps will be indicated by the same reference numerals.

The method 70 initiates when it is determined that the brake pedal is depressed, similarly as hereinbefore described with reference to block 52 of Figure 4. At this point, the device 10 is conveniently powered.

The method 70 comprises turning, at block 72 by way of the module 26, the brake lights or LEDs 9 on. There must obviously be no delay in illuminating the brake lights, whether in a normal situation or emergency situation.

The method 70 comprises waiting, at block 74, 4 milliseconds for the accelerometer to settle. As hereinbefore described, this is the first predetermined time to allow the microcontroller clock to settle, and the accelerometer output signal to stabilise. It has been determined that 4 ms is a reasonable value, also that the braking system has not had time to engage yet.

The method 70 comprises determining, at block 76, if it is the first time which the device 10 is running. As previously mentioned, a flag in EEPROM is programmed when the FLASH memory is programmed. This flag indicates the device 10 needs calibration. If the device 10 needs calibration, the method 70 comprises providing a 100 millisecond delay at block 78. The method 70 then comprises measuring and storing, at block 80, VZREF and V _XRE F (measured in the X-direction for a dual axis accelerometer) as hereinbefore described as these are indicative of a variation of the Og voltages of accelerometers between batches. Also as previously mentioned, this calibration is performed when the device 10 is installed in the car 12 and powered for the first time. This must be done on a horizontal surface. ln any event, when it is not the first time running, the method 70 comprises measuring or obtaining, at block 54, the first deceleration measurement V _Z1 , as hereinbefore described by way of module 22.

The method 70 then comprises waiting, at block 82, for 50ms, after obtaining the first deceleration measurement, for the brake pedal to settle. It will be appreciated that this is an experimentally determined time delay that would allow the brake pedal to be fully depressed, after which the car 12 would experience maximum deceleration.

The method 70 may then comprise measuring or obtaining the second deceleration measurement V _Z2 , as well as determining the deceleration value VDEC, block 56 & 58 as hereinbefore described.

The method 70 then comprises comparing, at block 60, V _DEC with the deceleration threshold value K as hereinbefore described. As previously described, for low cost economy tyres with a coefficient of static friction of 0.9 for example, this value would be set to 60% of this (for example).

If VDEC K, the method 70 comprises turning, at block 84, the brake lights or LEDs 9 off. A delay of 200ms is issued, at block 86, and the LEDs are turned on again, at block 88, and then another 150ms delay is issued at block 90. It will be appreciated that the emergency brake control signal is arranged to control the LEDs to operate as described in steps 84 to 90.

After block 90, in a loop like fashion, further deceleration measurements are obtained, at intervals determined by the types of signals output, and further V _DEC values are obtained for comparison at block 60. It will be noted that when an emergency brake control signal is output, the interval to determine the further deceleration measurement is approximately 350 milliseconds from the last time that a deceleration measurement was determined or obtained. It will be appreciated that this loop results in a bright flashing of the LEDs 9 in emergency braking conditions thereby warning the following driver of the same. It should be noted that the flashing frequency can be changed to optimize the human response by altering these delay times.

If VDEC < K, the method 70 comprises turning the brake lights or LEDs 9 off, at block 92. A further 50ms delay is issued at block 94 and the LEDs are then turned on again at block 96. It will be appreciated that the normal brake control signal is arranged to control the LEDs to operate as described in steps 92 to 96.

After block 96, in a similar fashion as hereinbefore described, further deceleration measurements are obtained and further V _DEC values are obtained for comparison at block 60. It will be noted that when a normal brake control signal is output, the interval to determine the further deceleration measurement is approximately 50 milliseconds from the last time that a deceleration measurement was determined or obtained. This loop results in the LEDs 9 entering a 50% PWM loop, the frequency of which is high enough so that the LEDs 9 just appear to be turned on (but dimmer than if they were in emergency). In this loop, the brightness of the LEDs are comparable in brightness to normal brake lights in other vehicles.

It follows that the two loops described above operate for as long as the brake pedal is depressed by the driver of the vehicle 12. It is also assumed that the likelihood of the road changing slope by a great amount during this condition is low, so the measured slope value will remain relatively accurate.

As hereinbefore described, for a dual axis accelerometer 16 or where the device 10 has a second accelerometer 16, a measurement from the accelerometer perpendicular to the road may be compared to a threshold thereby to indicate potholes, etc. in the road to the following driver.

There are at least two features of the present invention that are beneficial. The first is that for at least the first 110ms of illumination, the LEDs 9 are running at full power, and if there is no emergency, they become dimmer. The initial bright flash is perceivable and will help in shortening the reaction time of the driver following anyway (due to the inverse of persistence of vision of the human eye). The second benefit is that that in emergency situations the LEDs illuminate much brighter than normal conditions.

The present invention provides a more accurate determination of the slope of the road as hereinbefore described and therefore results in a lower probability of false announcements of emergencies. Also, a single axis accelerometer used for the present invention may reduce costs of the device.