TITLE: VEHICLE WARNING SYSTEM: METHOD AND APPARATUSThe present invention relates to a method and apparatus for the transmission by visual means of speed related information from the rear of a motor vehicle.
BACKGROUND TO THE INVENTIONAt the present time the only information which is automatically signalled from one vehicle to another is by the brake warning lights and reversing lights. However, this information is intermittent, and not directly related to speed. The brake warning lights are illuminated when the driver applies the brakes, providing a warning to following vehicle drivers that the vehicle is being braked, but a vehicle's speed can change from zero to maximum and return to zero without the brakes being applied. On today's congested roads this lack of information can lead to accidents.
I have now devised a method and apparatus for monitoring, measuring, and displaying speed related information of a moving vehicle in visual form to a following vehicle, so as to provide the driver of that vehicle with continuous speed related information, even though the brakes may not have been applied. The method and apparatus of the invention operate to give consistent information and can be applied to a wide range of vehicles. The invention can be fitted to existing vehicles as well as new vehicles.
SIJMMARY OF THE INVENTIONAccordingly, the present invention provides a method for continuously displaying speed related information to following vehicle drivers, by using rear facing indicators to show one of three vehicle states, whenever the vehicle is in motion: 1. A steady state which shows, regardless of the forward speed,that the vehicle speed is substantially constant, withinpredetermined limits.
2. Acceleration which shows when the vehicle is acceleratingat more than a predetermined value, and/or a plurality ofindicators which are energised at different accelerationvalues.
3. Deceleration which shows when the vehicle is deceleratingat more than a predetermined value, and/or a plurality ofindicators which are energised at different decelerationvalues.
The invention also provides a vehicle adapted to be moved along varying forward speed and which is provided an apparatus which comprises: a) means for detecting that speed and for measuring the rate ofchange of that speed; and b) means for directing signals rearwardly of the vehicle and meansfor changing the signal when the rate of change of speed exceedspredetermined values.
The indicators may also be colour and/or size coded. The acceleration and deceleration indicators may also be sub-divided into more than one colour and/or size.
An object of the invention is that the system can be fitted to both new and existing vehicles without confusion. If a vehicle driver sees the steady rate indicator in a vehicle ahead, he will know that the vehicle is fitted with the device, that it is operating, and that the vehicle is proceeding at a steady rate. Another object of the invention is that the system will update the signal information within 0.6 seconds and respond to speed changes down to 0.16 km per second, as longer delays detract from the value of the information.
Also the predetermined limits will be standardised and tamper-proof.
In order that the information will always relate to the same rate of speed change, regardless of the type of vehicle to which it is fitted.
The method and apparatus of the invention can be applied to any of a wide range of vehicles which are adapted to move at variable forward speeds, for example to motorcyles and heavy goods vehicles. For convenience, the invention will be described in terms of a motor car in which lamps are used to give the rearwardly directed signals to the driver of a following car.
The forward speed of the car can be detected in any suitable way, for example by monitoring the rotation of some component of the propulsion system of the car. It is particularly prefered to monitor the rotation of some part of the mechanism driving the road wheels of the car in which that rotation is directly related to the ground speed of the car.
The rotation of the drive shaft or other component can be monitored by any suitable method. However, it is prefered to use a non-contacting sensor, since this will usually overcome problems in accurate positioning of contact detection device and may reduce problems of reliability.
A particularly prefered means for monitoring the speed of rotation of the rotating part is one in which a beam of visible or infra red light is interrupted by a disc or other means carried by the rotating shaft or is reflected from a component carried by the shaft so that a photocell sensor receives a series of light pulses. The sensor thus produces a series of pulsed signals whose frequency varies with the speed of rotation of the shaft and hence with the road speed of the car.
The changes in speed observed by the above means can be monitored and the signal to the following car can be modified when the rate of change in speed, either acceleration or deceleration, exceeds predetermined rates. The series of pulsed signals will require processing before a change of speed can be determined. This is conveniently done using conventional microprocessor techniques. Thus, for example, the pulses from an optical sensor linked to the rotation of the drive shaft can be fed to a counter/timer mechanism in which the number of pulses occurring per unit time are computed. This number is then stored and compared with the number obtained from the subsequent computation to give a measure of the rate of change of speed of the car.
The sampling of the speed and the monitoring of any change therein can be carried out continuously or intermittently. However, it is prefered to ensure that the sampling is carried out with sufficient frequency that the time interval between display changes is less than the average reaction time of a driver. Thus, the sampling will preferably be carried out at intervals of from 0.1 to 0.6 seconds. The frequency of sampling is conveniently controlled by the counter/timer used in monitoring the speed of the car and the intervals can be based upon a time interval or upon a count interval, corresponding to the desired time interval.
As stated above, the signals given to the following car are modified when the speed of the first car changes by an amount exceeding predetermined values. These values can be set to any desired levels, eg. at a change of 1.6, 8 or 16 km per hour per second, depending upon the circumstances. However, I have found that it is desirable that the first signal change be triggered at a level which is sufficiently low to ensure that the maximum notice is given to the following driver of any speed change and yet which is not so low that the signal is being triggered repeatedly. Thus, it is prefered that signal changes be triggered at a change in speed of from 0.16 to 1.6 km per hour per second, notably from 0.3 to 0.8 km per hour per second.
The level at which the signals are triggered can be selected using known techniques.
When the car is in motion one of the three indications will be illuminated a) substantially constant b) acceleration c) deceleration.
Thus, the method and apparatus of the invention can incorporate three light signals, one red one to show deceleration, one yellow to show a steady speed, and a green one to show acceleration, these for example being located in the rear window of the moving vehicle or incorporated into the rear light cluster of the vehicle. Preferably the indicator will take the form of a strip indicator with multiple light segments.
The steady indicator segment being located near the mid-point with multiple segments each side. One series of segments for acceleration and the other for deceleration. For example as the acceleration rate increases more segments will be illuminated. Alternatively, other forms of illumination, such as LED displays, may be-used.
The method and apparatus of the invention thus provide a simple and effective way for signalling to a following motorist that the vehicle in front is travelling at a steady speed or is accelerating or decelerating. This gives the driver more reaction time within which to respond to the speed changes of the car in front. Since the apparatus and method are operated independently of the braking system and of any external sensors or roadside signalling systems, the invention can be applied to existing cars as well as being incorporated into new cars during construction.
DESCRIPTION OF THE DRAWINGS:The invention will now be illustrated by way of example only and with respect to the prefered form of the invention shown in the accompanying drawings in which Figure 1 is a diagrammatic perspective view of the components of the apparatus and Figure 2 is a diagrammatic view of the apparatus mounted upon the transmission system of a car.
DESCRIPTION OF A PREFERED EMBODIMENT OF THE INVENTION:The apparatus comprises a mounting means 1 by which a photocell sensor 2 and light source 3 are mounted adjacent to the drive shaft 4 of the car. This mounting can take the form of a bracket screwed or bolted directly to some fixed part of the transmission train. However, it is prefered to use a circular mounting clamp 1 which can be sized and configured to accept the rear end of the gearbox housing 5 of a variety of cars, so that a universal mounting means can be used.
The mounting clamp 1 incorporates means by which the photocell 2 and light source 3 are carried and supported in the desired position.
Again , this preferably made in an adjustable form, for example as an arm 6 carrying the photocell and light source terminally thereon.
The light beam passing between the light source 3 and the photocell 2 is interrupted by a disc or other interrupting means 7 mounted on the drive shaft 4 so that the interrupting means 7 is rotated in front of photocell 2 and the light source 3 by the shaft 4. The disc 7 conveniently takes the form of a split ring which is clamped onto the shaft 4 at the desired location so that the periphery of the disc 7 is in close proximity to the photocell 2 and the light source 3. The disc can be formed with a castellated rim 11 or with a series of black and white bars 12 on the periphery to provide a series of interruptions of the light beam as the disc rotates.In order to achieve the desired number of pulses from the photocell at typical speeds of rotation of the shaft 4, it'is prefered to have at least 70 to 100 castellations or bars ie interruptions of the light beam, per rotation of the disc 1. Typically there will be approximately 2300 pulses per second at 60 km per hour.
The signals from the photocell 2 are fed to a conventional counter/ timer mechanism 20, for example one utilising a microprocessor in conventional manner, to develop a series of signals corresponding to the speed of the vehicle. These are compared at such intervals as may be desired to determine what change in the speed of the vehicle there has been. Typically, the comparisons will take place at intervals of about 0.1 seconds.
The change in speed observed from the signals generated by disc 7 is monitored against preset limiting values, which have been programmed into the microprocessor or other mechanism 20 carrying out the measurement, to determine whether or not the signal to the following car should be modified. Typically, the limiting value corresponds to a change in speed of the car of about 0.48 km per second.
When the change in speed exceeds any of the limiting values the rearwardly facing signal 30 is modified to. give a visual warning to a following driver.
The apparatus of the invention can readily be fitted to existing cars. The invention thus provides a kit of parts adapted to be mounted in a first vehicle to give a signal to a following vehicle of the forward speed of that first vehicle, which kit of parts comprises means for sensing the speed of the vehicle and changes in that speed and the rate of such a change; in association with means for giving a visual signal rearwardly of the vehicle to indicate to a driver of a following vehicle.