GB2231664A - An accelerometric device in a moving vehicle - Google Patents

Abstract

A signalling device is attached to a road using vehicle to indicate to other road users about the dynamics of the vehicle by using accelerometric information. When driving behind other vehicles, in particular on motorways where traffic is moving at high speeds, drivers can assess changes in the velocities of vehicles in front of them only through second order parameters, a thing which seriously delays their reaction to such changes. The accelerometric signaling device will indicate changes in the velocity of a vehicle, helping other drivers to adapt their own speed in accordance and in good time, e.g. a red light, 6 in Figure 2, will be switched on as soon as the vehicle starts decelerating, turning into a flashing light for accentuated deceleration. A green light, 8 in Figure 2, will turn on when the vehicle is accelerating, and a white light, 7 in Figure 2, will be on for constant velocities. <IMAGE>

Description

AN ACCELEROMETRIC DEVICE TO SIGNAL THE DYNAMICS OF A MOVING VEHICLE This invention relates to a signalling device for motor cars and other road using vehicles.

When driving behind a moving vehicle, in particular on motorways where speeds are high, a driver does not have direct information about the most important parameter relating to the vehicle in front : is it closing in or going away? Evaluation of this crucial parameter is left, today, to second order estimates of the distance, relying on judgment of the relative size of the other vehicle, its dimensions relative to the scenery and other indirect information based on the driver's experience. This may be sufficient as long as one does not need to react fast and when the distance to the vehicle in front is far enough to accommodate for the required reaction time in case of an emergency stop. However, when this is not the case, and when appropriate distances are not kept, or when weather conditions are bad and limit drivers' visibility, serious accidents do occur.The problem is that the only signals available, today, are the brake lights. This information is late, and does not tell whether it is an accentuated deceleration or a slight one, neither does it indicate deceleration of the vehicle without braking.

It is a basic concept in control theory, that in order to optimise the behaviour of the controlled body one needs to feed the controller with information not only about the controlled parameter but also about its derivatives. In the case of road transport, the main controlled parameter is the velocity. Its first derivative is the acceleration (positive and negative). Using such information will enable drivers, once they become acquainted with its use, to better adjust their own speed to that of other vehicles on the road. Knowing that the vehicle in front is slowing down before Its driver actually activated his brakes. can provide the driver with ample warning and allow him to adjust his own speed, accordingly and in time.

According to the present invention, a signalling device attached to road using vehicles, warns other vehicles about speed changes, by using accelerometric information.

A specific embodiment will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a functional block diagram of the main parts of the system.

Figure 2 is a schematic drawing of a motor car equipped with the device.

Referring to Figure 1, the accelerometer 1 provides output proportional to the car acceleration\ deceleration situation. If zero voltage represents zero acceleration, then positive values will be produced for acceleration and negative values for deceleration. Sensitivities of, say, 10 millivolts per g can normally be expected. This signal is amplified in amplifier 2, from which signals of the order of plus minus 5 volts per 0.1 g are obtained. This signals are fed to threshold circuits 3 which are activated at a certain, predetermined level to produce an "on" signal. There are three levels of activation for three threshold circuits: two for negative signals ( deceleration) and one for positive signals (acceleration).At constant velocities the output of the accelerometer will be below the required levels of the threshold circuits, thus activating neither the red nor the green light. In this situation the white light will be on.

Once a level of positive acceleration is reached a level enough to pass the threshold, the green light relay, in the driver unit 5 , will be switched on, extinguishing the white light and activating the green light 8. A similar process will take place for the first level of deceleration activating the red light 6. However, if a larger value of deceleration takes place, sufficient to surpass the second threshold, then, a flasher unit 4 is activated, in addition to the the red relay in driver 5, and the red light 6 is fed with a pulsating voltage, producing a blinking signal. Optionally, one can modulate the frequency of the flasherl 4 by the level of the deceleration signal producing higher rates of flashing for higher values of deceleration.

The device can be mounted on the rear side of the vehicle in a manner shown in figure 2.

A second specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 3 shows a schematic of an horizontal swivel arm accelerometer; Figure 4 illustrates an electric circuit which activates the three signalling lights at the back of the vehicle , as shown in Figure 2.

The swivel arm accelerometer is mounted in a balanced gimbal to avoid influence of slopes and banking. During travel at a constant speed, the arm rests in its central position, near the optoelectronic proximity switch 9, in Figure 3, causing it to be at the activated position, thus activating relay 15 (B) in Figure 4. The arm is damped by a damper 11 mounted near its pivot I, Figure 3, thus avoiding excessive oscillations due to vibrations. It is also clear from figure 3 that a certain amount of oscillations of the arm are tolerable due to the prolonged structure of the end e:ement 6. The mass of element 6, the length of the arm 3 and the springs coefficients are calculated to fit with the accelerations typical of the vehicle, and according to the values desired to elicit warning signals.

When the vehicle's speed is decreased, while moving forward, the arm swivels forward, in direction a, and approaches proximity switch 8. Once the critical distance is reached, the switch turns on and relay 14 (A), Figure 4, is activated, causing the red light 11 to turn on via the normally closed contacts of the flasher unit 18 (F) and normally open contact a2, now closing. This situation will continue as long as the level of deceleration is kept at or near this value. If deceleration is increased, for instance by depressing the brakes, then proximity switch 7 will turn on, activating relay 16 (C). Relay 16 (C) will start the flasher 18 (F), via normally open contact cl, which will now cause the red light 11 to blink.

This will go on until the deceleration decreases to a level enough to release proximity switch 7, thus releasing relay 16 (C).

Further decrease in deceleration will activate proximity switch 9, once again, activating relay 15 (B), a thing which releases the self hold of Relay 14 (A) by opening of bl, extinguishing the red light 11. The length of the element 6 is calculated so as to avoid a possibility of activating proximity switches 8 and 9 simultaneously. A similar sequence of events takes place for forward acceleration as follows: The arm will move backwards (direction b in Figure 3) activating proximity switch 10, causing the green light 13 to turn on, following the activation of relay 17(D) via d2. This condition is kept via the self holding of relay 17 (D), until the moment that the acceleration decreases to the extent that proximity switch 9 turns on again. This, in turn, releases the self hold of 17 by opening of b2, which is a normally closed contact.

A third specific embodiment of the invention will now be described by way of example.

An analogue signal proportional to the velocity of the vehicle can be generated by means of a tachogenerator attached to the transmission or to any other convenient location. Such a device will produce a signal proportional to the vehicle's speed. It also may be obtainable by other means already existing in some vehicles. The analogue signal may be treated by analogue circuitry, using operational amplifiers to amplify and activate a derivative function to get a signal proportional to the acceleration. It may, on the other hand, be treated digitally by converting it into digital signals by connecting it to an A\D converter such as ADC 0808. The signal is then fed into a microcontroller such as 8051.By sampling the velocity at different times, and by subtracting consequent velocity values, dividing the difference by the difference in sampling times, a value proportional to the acceleration can be obtained. This is done by a set of instructions controlling the microcontroller. These instructions also can identify when does the acceleration pass a preset critical value. All the generated signals - including identification of the sign of the acceleration, are sent through programmable input\output devices such as 8155, to be converted back to analogue by digital to analogue converters such as DAC 0800. A decoder is employed to enable, via the programme, the correct output to be activated Both versions of the circuit - the analogue and the digital, produce four outputs, each representing a level of acceleration: one for zero acceleration, one for forward acceleration and two for deceleration. These outputs can activate relays which turn on and off the appropriate lights1 as shown in Figure 2. The two deceleration signals represent two levels of deceleration: slight and accentuated, the latter activating a flasher unit.

Claims (19)

1. A signalling device attached to a road using vehicle to warn other vehicles about its speed changes, using accelerometric information.

2. A signalling device as claimed in CLAIM 1 that uses accelerometric information in combination with other information on the car's dynamic behaviour.

3. A signalling device as claimed in CLAIM 1 to indicate the dynamic situation of a vehicle on the road using light signals for rear signalling.

4. A signalling device as claimed in CLAIM 2 that uses light signals for back and front signalling.

5. A signalling device as claimed in CLAIM 3 that uses the combination of three colours - red, green and white to indicate deceleration, acceleration and constant velocity, respectively.

6. A signalling device, as claimed in CLAIM 4, where a constant red light indicates moderate deceleration, and a flashing red light indicates accentuated deceleration.

7. A signalling device as claimed in CLAIM 1 that uses accelerometric information in combination with the brake lights signals.

8. A signalling device as claimed in CLAIM 1 that uses accelerometric information in combination with reverse moving information.

9.A singnaling device as claimed in CLAIM 1 that uses speed information and derives the information on acceleration by analogue electronic means.

10. A signalling device as claimed in CLAIM 1 that uses speed information and derives the information on acceleration by means of digital electronic circuits.

11. A signalling device as claimed in CLAIM 1 that uses seismic masses as a means to measure the acceleration.

12. A signalling device as claimed in CLAIM 1 that uses pendulous devices to measure the acceleration.

13. A signalling device as claimed in CLAIM 1 that uses a strain gauge accelerometer to measure the acceleration.

14. A signalling device as claimed in CLAIM 1 that uses piezo electric devices to measure the acceleration.

15. A signsaling device as claimed in CLAIM 1 that uses a "spring type" accelerometer for this application.

16. A signalling device, as claimed in CLAIM 3, using a multi-light system with several lights of each colour and thus signalling what the rate of acceleration is.

17. A signalling device substantially as described herein with reference to Figures 1-2 of the accompanying drawings.

18. A signalling device substantially as described herein with reference to Figures 3-4 of the accompanying drawings.

19. A signalling device substantially as described herein with reference to the third specific embodiment.