WO2003047928A2

WO2003047928A2 - Automatic windshield wiper system

Info

Publication number: WO2003047928A2
Application number: PCT/IN2002/000227
Authority: WO
Inventors: Anish Lohokare
Original assignee: The Indian Institute Of Technology, Bombay
Priority date: 2001-12-04
Filing date: 2002-12-03
Publication date: 2003-06-12
Also published as: WO2003047928A3; AU2002361491A1; AU2002361491A8

Abstract

This invention relates to an automated system for wiping of windshields of automobiles and the like and in particular to an automated wiping system with means for variation of mode and/or intensity of whiping, based on rainfall. The system is also integrated with manual option to change the mode of variable wiping. The invention further provides for an automated wiper systen with combination of options such as of intermittent operation with dwell-time variation between two wiping cycles of the wiper motor or continuous operation with speed control depending on the rainfall intensity and frequency. The automated wiper system can be adapted to be fitted into any variety of vehicles and is free from adverse effects of extraneous and environmental factors such as sound, impurities in the rainwater, presence of foreign bodies in the rainwater, dirt on the windshield, smog, etc. The automated system for wiping of windshields of automobiles and the like comprise: a rain sensor assembly comprising of rain water measuring device and/or a low rainfall detector; a detector selection control circuit operatively connected to said sensor assembly and adapted to generate signals based on output of said rain water measuring device and/or low rainfall detector to selectively actuate or deactive a wiper motor driving the wipers on said screen.

Description

FIELD OF THE INVENTION

The present invention relates to an automated system for wiping of windshields of automobiles and the like and in particular to an automated wiping system with means for variation of mode and/or intensity of wiping based on the rainfall. The system is also integrated with manual option to change the mode of variable wiping.

A clean windshield is an essential requirement for safe driving. It is a common practice for drivers to activate the windshield wiper of their vehicles during rain to ensure clear vision. Several developments related to automated wipers are also available in literature and some of them have been commercially exploited. Prior Art on this subject is varied and may be classified under five major technology options and are based on the basic principle of detecting water droplets on the windscreen with an appropriate sensor and then transmitting the signal to a device to actuate the wiping system.

The water detection principle on windscreens are based on a variety of detection methods which are used to drive the wiping systems and are described in the literature listed below:

There are several wiper systems based on Optical methods as described in Patents JP 59045250A2, US 6097024, US 6160369, US 5453676, US 5117168, EP 1015286A1. These methods use emitters, receivers and transmitters (light, infrared, microwave, etc), image sensing or photography to measure rainfall.

US Patent numbers 4942349, 4710878 and 4827198 based on Capacitive/Resistive methods sense the amount of water precipitated on the windscreen as a function of the capacitance or the resistance of the incident rainfall.

US Patent numbers 5773946, US 3786330 and US 5432415 based on the acoustic principles use sound receivers and transmitters to detect and measure the frequency of impact on the vehicle's surface due to raindrops which is translated to the amount and intensity of rainfall.

US Patent No. 5119002 based on pressure transducers determine the amount of rainfall depending upon the force with the raindrops impinge on the transducers on the windscreens.

US Patent No. 3643145 uses principles based on current variation that determine the amount of rainfall depending on the variation of current drawn by the wiper motor due to change in wetting condition of the windshield. Japanese Patent JP 5254397A2 and US Patent 6002229 are based on the raindrop sensors that detect water and activate the wiper system.

Some of the shortcomings of the techniques described in the prior art are as follows as:

1. The circuit is momentarily disabled for a new measurement in certain type of sensors resulting in poor response.

2. Some automatic wiper systems are intermittent with limited speed variation or sometimes no speed variation. In several cases the wiper remains continuously on.

3. In case of sensors that measure resistance, capacitance, etc, their response can get adversely affected by impurities presents in the rainwater, the temperature of rainwater, as well as the pattern of the water between the wires for optical/infrared sensors.

4. The optical sensors under certain situations are unable to differentiate other entities on the glass as rainwater thereby affecting the functioning of the automated wiper system.

5. Varying rainwater drop sizes and their frequency for the same amount of rain can cause may cause inconsistent responses in case of transducer-based sensors.

6. Vibration based sensors may adversely get affected by disturbances caused by extraneous mechanical vibrations.

7. A small part of the screen used for detection of rain may not be a good representative of the whole screen in case of optical sensors.

Therefore there is long felt need in the automobile industry to provide for user-friendly automatic wiper which can be regulated based on the intensity of rainfall i.e. light or heavy shower, its duration and at the same time would be reliable, cost effective and adapted for use in variety of vehicles.

OBJECT OF THE INVENTION

It is thus the basic objective of the present invention to provide for system for automated wiping of automobile windshields and the like which would be reliable, user friendly and also cost- effective and would be effective for both low rainfall wiping as well as during extreme heavy downpour.

Another object of the invention is to provide for an automated wiper system with combination of options such as of intermittent operation with dwell-time variation between two wiping cycles of the wiper motor or continuous operation with speed control depending on the rainfall intensity and frequency. Yet another object of the invention is to provide for an automated wiper system with a suitable combination of both dwell time variation between two wiping cycles of the wiper and speed control of the wiper motor or continuous operation with speed control depending on the rainfall intensity and frequency.

Yet it is another object of the invention to provide for an automated wiper system with a combination for manual option to change the transition from intermittent to continuous speed of the wiper as and when required.

It is yet another object of this invention to provide for an automated wiper system that is adapted to be fitted into any variety of vehicles thus providing for its extensive use and application.

Yet another object of the invention is to provide for an automated wiper system that is free from adverse effects of extraneous and environmental factors such as sound, impurities in the rainwater, presence of foreign bodies in the rainwater, dirt on the windshield, smog, etc.

Another object of the present invention to provide for a system of indicating intensity of rainfall especially for use in vehicles and the like to actuate wiper systems.

SUMMARY OF THE INVENTION

Thus in accordance with basic aspect of the present invention there is provided an automated system for wiping of windshields of automobiles and the like comprising:

- a rain sensor assembly comprising of rain water measuring device and/or a low rainfall detector;

a detector selection control circuit operatively connected to said sensor assembly and adapted to generate signals based on output of said rain water measuring device and/or low rainfall detector to selectively actuate or deactivate a wiper motor driving the wipers on said screen.

In accordance with a preferred aspect the said detector selection control circuit comprises means to compare the signal output of said rainwater measuring device and the low rainfall detector to selectively actuate or deactivate said wiper motor directly or to actuate said wiper motion through a wiper operation circuit based on the amount of rainfall. In the above automated system in accordance with one embodiment said rainwater-measuring device comprise a calibrated collection vessel and a water level measuring means. While the calibrated rain collection^' vessel can^' be of any desired shape preferably it is obtained of cylindrical shape. The calibrated collection vessel is specially developed and comprises plurality of perforations of predetermined number and sizes on the vessel wall at specific heights to enable outflow of the collected water at a specified rate for varying amount and intensity of rainfall and is further provided with an overflow outlet at the top indicative of the possible maximum change in the water level in the collection vessel. .

The level of the rainwater in the collection vessel is monitored by means of a float operatively connected to means for transferring the level changes into electrical signals. The float is linked to a support via a spring to act as a damper of any stray vibrations.

Preferably, the cross sectional area and shape of the float are made compatible with that of the collection vessel. V the submerged volume of the float is governed by the relationship V < A_cx H /10 where A_c is the cross sectional area of the float. The spring is governed by the relationship 0 < k < V p_w g / H where H is the height of the vessel up to the overflow point, p_w is the density of water, g is acceleration due to gravity, k is the spring constant of the spring holding the float. The float is adapted to drive a slider on a high resistance wire that is connected across a battery so that changes in the float moves the slider across the wire thereby translating into a change of the detected resistance of the wire to be fed as input into the said detector selection control circuit.

Importantly, the said calibrated rain collection vessel is calibrated to indicate a maximum volume for the measurement of collected rainwater of A/12 where A is the cross sectional area of the vessel in cm². The calibration can be based on the relationship H²/> 36/π where H is the height of the vessel in cm. Up to the overflow point.

In accordance with another embodiment the rainwater-measuring device used in the system can comprise rainwater flow measuring device. The flow-measuring device can be a rotameter, piston type area flowmeter and the like.

Preferably, the rainwater flow measuring device has a sensitivity of less than or equal to A/30 cm³/sec.

In accordance with another preferred aspect the automated wiper system is provided with means for manual switchover from intermittent wiping and continuous wiping as and when required. The low rainfall detector can comprise a detector positioned on the windshield, which can be activated by falling droplets of rain on windscreen to indicate or generate signals for low rainfall.

The above system thus provides for the automated wiping of the windshields with start, stop and variation of wiping speed through combination of intermittent operation with dwell time variation between two wiping cycles of the wiper or a suitable combination of both dwell time variation between two wiping cycles of the wiper and speed control of the wiper motor, or continuous operation with speed control depending on the rainfall intensity including the manual option to change the transition from intermittent to continuous wiping speeds.

The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustrations as per the accompanying figures wherein

Figure 1 illustrates the automatic wiper system in accordance with the present invention.

Figure 2 illustrates an embodiment of the rain sensor assembly used in the system.

Figure 3A illustrates and 3B illustrates the collection vessel with perforations used in the system.

Figure 4 illustrates another embodiment of the rain sensor assembly.

Reference is invited to Figure 1, which illustrates an embodiment of the automated system of wiper assembly in accordance with the present invention. As illustrates in said figure, the system basically comprises of the rain sensor (100) providing for rain water measuring and/or the low rain fall detector which is operatively connected to the detector selection control circuit (8) which in turn is connected to the wiper motor (12) directly as well as through the wiper operation circuit (1000) for the desired selective operation of the wiper.

As discussed above the system provides for measuring of the rain water and/or detection of the low rain fall by said rain sensor assembly and said rain sensor assembly operatively connected to a detector control circuit which is adapted to generate output signals based on the rain sensor assembly output to selectively actuate or deactivate water motor driving wipers directly or through the wiper operation circuit.

As also discussed earlier, the rain sensor assembly can be obtained under various embodiments, which are now discussed hereunder: Reference is invited to Figure 2, which illustrates an embodiment of the rain sensor (100A). As shown in said figure, rain sensor assembly basically comprises of the rain water measuring device and low rain fall detector. In this embodiment, the rain-measuring device comprises of the calibrated collection vessel (1) with a plurality of perforations (13), which is operatively connected to a wiper level measuring means. Rain water falling on a part of the vehicle is canalised to the rainwater collection vessel (1).

The rainwater collection vessel (1), is provided with perforation(s) (13) at specific heights that enable outflow of the water at a specified rate collected in the collection vessel at varying amount and intensity of rainfall. The residence time of the water level at each of the overflow points is dependent and is controlled by the number and size of perforation(s) (13).

There is an overflow outlet at the top beyond which no further change in the level takes place in the collection vessel

The Level Detector (7) consists of a float (102), slider (105), battery (130) and high resistance wire (107). The high resistance wire (107) is connected across the battery (130) as shown. 201 is the point of maximum potential on the high resistance wire (107). The point of minimum potential on the high resistance wire (107) is 202. The float (102) is so designed to minimize any leakage of water between the float wall and the inner surface of the vessel. The slider (105) slides over the high resistance wire (107) and is connected to the spring (104) and float (102) as shown. As the float (102) moves up with increase in the level of the collected rainwater, the slider (105) rises and the voltage (V25) between the slider (105) and the point 202 increases.

A damping device (50) is provided consisting of Spring (104), Support (106), Constriction (103) The assembly of the spring (104), support (106) and the constriction (103) acts as a damping device for the float (102). The spring (104) is suspended from the support (106) by one end and the other end is attached to the slider (105) as shown in fig 3. The constriction (103) enables the float (102) to move only in the direction of the vertical axis of the vessel. Optionally, it is also possible that the support (106), slider (105), spring (104), constriction (103), constriction (103), high resistance wire (107) and float (102) are integrated into a single assembly. Additionally a Damping Device (5) may be optionally used to damp the vibrations of the vessel (1).

The Low Rainfall Detector (6) is also shown in Figure 3. This is provided for detecting low rainfall. The two electrodes (3 and 4) with a gap between them are embedded to the windshield located in the area of windshield that is within the wiping zone of the wiper. When a water drop comes within the gap of the electrodes the electrical properties between the electrodes (3 and 4) changes. These changes are detected by the low rainfall detector (6) and the signal is fed to the Detector Selection Control Circuit (8).

The calibrator container (1) is comprised of perforations of desired dimensions and numbers to indicate the intensity of the flow of rain in said container. Embodiments of such perforated construction of container vessel are illustrates in figures 3A and 3B.

Reference is now invited to Figure 4, which illustrates an alternative embodiment of the rain sensor (100B) for use in the system of the invention. As illustrated in said figure in this embodiment rainwater flow measuring device (4A) is operatively connected to the detector control circuit (8). Further the low rainfall detector (6) similar to the earlier embodiment is provided on the windscreen as explained in relation to the rain sensor (100A) earlier. Output of this detector is again fed into the detector selection control circuit.

The said flow-measuring device (4A) can be a rotameter, piston type area flowmeter, etc.

Rainwater falling on a part of the vehicle of a predetermined area (A) is transported to a flow- measuring device (4A). The output of the flow-measuring device (4A) is given to the Detector Selection Control Circuit (8).

For detecting low rainfall, low rainfall detector (6) and the two electrodes (3 and 4) are used in the same manner as described previously. The low rainfall detector (6) gives its signal to Detector Selection Control Circuit (8).

Reference is now invited again to Figure 1 which illustrates in detailed the Detector Selection Control Circuit (8): This circuit selects the output of the Low Rainfall Detector (6) or that of the Level Detector (7) / Flow Measuring Device (4A) based on a predetermined set threshold. In case of very low rainfall, where the output is lower than the threshold, the output of the Low Rainfall Detector (6) is selected in preference to the output of the Level Detector (7).

In case of higher rainfall when the output is greater or equal to the threshold, the output of the Level Detector (7) / Flow Measuring Device (4A) is selected. The selected output is fed to the Wiper Operation Circuit (1000).

The functioning of the Detector Selection Control Circuit (8) is being illustrated with a non- limiting example. EXAMPLE - A

In this study it is assumed that the sensitivity of the Detection Selection Control Circuit is equal to or exceeds 0.1 V and that the Low Rainfall Detector (6) gives an output of 5V when a drop is detected.

Alternatively in the embodiment involving the Flow Measuring Device, it is assumed that the associated flow-measuring device (4A) gives an output voltage (V50). Also, as stated earlier, voltage (V25) is the output of the level detector (7)

Under these conditions the Detector Selection Control Circuit (8) performs as follows:

i) If the low rainfall detector (6) gives an output, and if the voltage (V25) or voltage (V50), whichever applicable, is less than 0.1 V, then the Control Circuit (8) drives the wiper at a predetermined speed and delay time between the wiping cycles.

ii) If the low rainfall detector (6) gives an output, and if the voltage (V25) or voltage (V50), whichever applicable, is equal to or more than 0.1 V then the Detector Selection Control Circuit (8) gives the voltage (V25) to the Wiper Operation Circuit (1000).

As further illustrated in Figure 1 the Wiper Operation Circuit (1000) consists of the following components:

(a) Comparator (9)

(b) Intermittent Wiper Control Circuit (10)

(c) Continuous Wiper Control Circuit (11)

If the input to the Comparator (9) is below a predetermined threshold (300), the comparator (9) drives the Intermittent Wiper Control Circuit (10). This circuit changes the dwell time between wiping cycles at a predetermined speed of the wiper motor based on the intensity of the rainfall. Alternatively, a suitable combination of increase in wiper motor speed and reduction in dwell time may be used as the input to the Intermittent Wiper Control Circuit (10). If the input to the Comparator (9) exceeds the predetermined threshold, then the comparator (9) drives the Continuous Wiper Control Circuit (11 ).

The Wiper Operation Circuit (1000) is not activated unless there is at least some output from the low rainfall detector (6). When it stops raining the water in the collection vessel (1) drains out and the water between the wires (3 and 4) is wiped off, no signal is received by Detector Selection Control Circuit (8) and the wiper operation stops. In the embodiment involving the flow-measuring device (100B) the water in the flow-measuring device (4A) flows out and the water between the electrodes (3 and 4) is wiped off, no signal is received by Detector Selection Control Circuit (8) and the wiper operation stops.

The invention also provides options for manual control of the operations and to change the threshold (300) based on user preferences for intermittent and continuous wiping of the windshield.

In another manual option if the user finds the wiping excessive, it would be possible for him to use a fraction of the output of the Comparator (9) for the operation of the Control Circuit (1000).

This invention is further illustrated with some non-limiting examples.

Example - B

For the purpose of this study the area chosen for the collection of rainwater was 120cm². Three cylindrical tubes of 1cm diameter were used as collection vessels with a range of perforations varying in sizes and numbers at different heights shown in figures 3a and 3b. The vessel are calibrated, for example, to give a near linear variation of flow rate of the water collected into the vessel with height by so choosing the number of holes, size of the holes and the gap between them which was adjusted to be 1.33 cm³/s flow rate of the collected water per cm of height in the collection vessel.

An overflow outlet at the height of 7.5 cm corresponded to a flow rate of water at 10 cm³/s. When this stage is reached, the wiper would operate in a continuous mode at maximum speed.

For the case of low rainfall, intermittent wiping of the windshield with a delay time between two wiping cycles takes place and the delay time decreases with the increase in the intensity of the rainfall. For medium and high rainfall, continuous wiping of the windshield with a near zero delay time between two wiping cycles takes place and the speed of the wiper motor increases with the increase in the intensity of the rainfall.

The threshold between intermittent and continuous wiping was set at 5 cm³/s. At this flow rate wiper motor had a speed of 30 rpm and the speed increases with increase in flow rate. For example the motor had a speed of 45 rpm for a flow rate of 7.5 cm³/s and 60 rpm for a flow rate of 10 cm³/s. Below 5 cm³/s the delay time increases with decrease in intensity of rainfall falling on the vehicle.

Table 1 illustrates the results on wiping speeds with associated delay times obtained for water overflow rates of 2.2 cm³/s, 6 cm³/s, and 8 cm³/s with the collection vessels described in figures 3a and 3b.

Table No. 1

Experimental results:

As evident from the above the automated windshield wiper operates reliably under varied rainfall intensities, and self adjusts the speed of the motor and frequency of wiping and at the same time is independent of the impurities presents in the rain water, the temperature of rainwater, as well as the pattern or drop size of the water on the windshield. Its function is not affected by vibrations and does not get activated erroneously by any extraneous effects such as vibrations, sounds, smog, particles, etc. The system provides for options of continuous speed variation as well as intermittent operation depending on rainfall conditions or user preferences. The power consumption is also optimal

Claims

We claim

1. An automated system for wiping of windshields of automobiles and the like comprising:

- a detector selection control circuit operatively connected to said sensor assembly and adapted to generate signals based on output of said rain water measuring device and/or low rainfall detector to selectively actuate or deactivate a wiper motor driving the wipers on said screen.

2. An automated system as claimed in claim 1 wherein said detector selection control circuit is connected to said wiper motor directly and/or to said wiper motor via a wiper operation circuit.

3. An automated system as claimed in claim 2 wherein said a wiper operation circuit comprising of a comparator capable of comparing the signal output of said rainwater measuring device to a threshold ion to selectively trigger an intermittent wiping operation or a continuous wiping operation.

4. An automated system as claimed in anyone of claims 1 to 3 comprising means for manual switchover from intermittent wiping to continuous wiping and vice-versa as and when required.

5. An automated system as claimed in anyone of claims 1 to 4 wherein said rainwater measuring device comprise a calibrated collection vessel and a water level measuring means.

6. An automated system as claimed in anyone of claims 1 to 4 wherein said rainwater measuring device comprise rainwater flow measuring unit.

7. An automated system as claimed in claim 5 wherein said calibrated rain collection vessel is of desired shape preferably cylindrical.

8. An automated system as claimed in claim 7 wherein the said calibrated rain collection vessel is calibrated to indicate a maximum volume for the measurement of collected rainwater of A/12 where A is the water collection area cm².

9. An automated system as claimed in claim 7 wherein the said calibrated rain collection vessel is calibrated based on the relationship H²/ > 36/TI where H is the height of the vessel in cm.

10. An automated system as claimed in anyone of claims 5 to 9 wherein said calibrated collection vessel comprises a plurality of perforations of predetermined number and sizes on the vessel wall at specific heights to enable outflow of the collected water at a specified rate for varying amount and intensity of rainfall and is further provided with an overflow outlet at the top indicative of the possible maximum change in the water level in the collection vessel.

11. An automated system as claimed in anyone of claims 5 to 10 wherein level of the rainwater in the collection vessel is monitored by means of a float operatively connected to means for transferring the level changes into electrical signals.

12. An automated system as claimed in claim 11 wherein said cross sectional area and shape of said float is compatible with that of the collection vessel and governed by the relationship V < A_c x H /10 where A_c is the cross sectional area of the float 0 < k < V p_w g / H where and V is the submerged volume of the float. The spring is governed by the relationship 0 < k < V ρ_w g / H where p_w is the density of water, g is acceleration due to gravity, k is the spring constant of the spring linked to the float.

13. An automated system as claimed in anyone of claims 11 to 12 wherein said float is adapted to drive a slider on a high resistance wire that is connected across a battery so that changes in the float moves the slider across the wire thereby translating into a change of the detected resistance of the wire to be fed as input into the said detector selection control circuit.

14. An automated system as claimed in anyone of claims 1 to 13 wherein said rainwater flow measuring unit has a sensitivity of less than or equal to A/30 cm³/sec, and accuracy of flow measurement in the range A 12 cm³/sec to A/10 cm³/sec.

15. An automated system as claimed in anyone of claims 1 to 14 wherein said low rainfall detector is located internally on the windshield and comprise a set of electrodes sensitive to detect changes in the electrical properties when raindrops impinge on them.

16. An automated system as claimed in anyone of claims 1 to 15 wherein said detector selection control circuit comprise comparator means to compare signal output of rainwater measuring arrangement and the low rainfall detector to selectively actuate or deactivate the wiper motor directly or actuate a wiper operation circuit based on the amount of rainfall set by a predetermined threshold.

17. An automated system as claimed in anyone of claims 1 to 16 wherein said the detector selection control circuit functions based on a preset threshold such that in case of very low rainfall, where the output is lower than the threshold, the output of the Low Rainfall Detector is selected in preference to the output of the said water level measuring unit or the output of the flow measuring device to be fed to said wiper operation circuit

18. An automated system as claimed in anyone of claims 2 to 17 wherein the said wiper operation circuit comprises of a comparator, intermittent wiper control circuit, a continuous wiper control circuit including means for automated/manual change the threshold points.

19. An automated system as claimed in claim 18 wherein said the comparator is capable of automatically and selectively triggering the intermittent wiping circuit or a continuous wiping circuit based on a preset threshold.

20. An automated system as claimed in claims 2 or 19 wherein said wiper operation circuit comprise means for manual switchover between intermittent and continuous control circuits based on user preferences.

21. An automated system as claimed in anyone of claims 3 to 20 wherein said the intermittent wiping circuit is adapted to be automatically actuated by the said comparator and comprise means of automatically changing the dwell time between wiping cycles at a predetermined speed of the wiper motor

22. An automated system as claimed in anyone of claims 3 to 20 wherein said the intermittent wiping circuit is adapted to be automatically actuated by the said comparator and comprise means of automatically changing both the dwell time between wiping cycles as well as the speed of the wiper motor depending on the intensity of the rainfall.

23. An automated system as claimed in anyone of claims 3 to 21 wherein said the continuous wiping circuit is adapted to automatically actuate and comprise means for automatically driving the wiper motor to a continuous mode of wiping based on the intensity of the rainfall.

24. An automated system as claimed in anyone of claims 1 to 23 wherein the detector selection control circuit is operative to actuate the wiper operation circuit only when it receives signals from said rain sensor assembly.

25. An automated system as claimed in claim 24 wherein said collection vessel is adapted to drain off water.

26. An automated system as claimed in anyone of claims 1 to 25 comprising damping arrangements for the said collection vessel and/or flow-measuring device.

27. An automated system as claimed in anyone of claims 6 to 26 wherein said rainfall flow measuring unit comprise a rotameter, piston type area flowmeter and the like.

28. A system for indicating the intensity of rainfall comprising; a calibrated rainfall collection vessel; means to monitor the water level in said vessel and generate signals indicating the intensity of rainfall.

29. An automated system as claimed in claim 28 wherein the said calibrated rain collection vessel is calibrated to indicate a maximum volume for the measurement of collected rainwater of A/12 where A is the rainwater collection area in cm².

30. An automated system as claimed in claim 29 wherein the said calibrated rain collection vessel is calibrated based on the relationship H²/ > 36/π where H is the height of the vessel in cm.

31. An automated system as claimed in claim 30 wherein said calibrated collection vessel comprise plurality of perforations of predetermined number and sizes on the vessel wall at specific heights to enable outflow of the collected water at a specified rate for varying amount and intensity of rainfall and is further provided with an overflow outlet at the top indicative of the possible maximum change in the water level in the collection vessel.

32. An automated system as claimed in claim 31 wherein level of the rainwater in the collection vessel is monitored by means of a float operatively connected to means for transferring the level changes into electrical signals.

33. An automated system as claimed in claim 32 wherein said cross sectional area and shape of said float is compatible with that of the collection vessel and governed by the relationship 0 < k < V p_w g / H where V is the submerged volume of the float, p_w is the density of water, g is acceleration due to gravity, k is the spring constant of the spring holding the float. V is governed by the relationship V < A_cx H /10 where A₀ is the cross sectional area of the float.

34. An automated system as claimed in claim 33 wherein said float is adapted to drive a slider on a high resistance wire that is connected across a battery so that changes in the float moves the slider across the wire thereby translating into a change of the detected resistance of the wire to be fed as input into the said detector selection control circuit.

35. An automated system as claimed ϊn claim 34 wherein said rainwater flow measuring apparatus has a sensitivity of less than or equal to A/30 cm³/sec and accuracy of flow measurement in the range A/12 cm³/sec to A/10 cm³/sec.

36. An automated system as claimed in anyone of claims 28 to 35 for use with wipers such as windscreen wipers for automobiles and the like.

37. An automated system of wiper assembly the automobiles and the like and a system for determining the intensity of rainfall substantially as herein described and illustrated with reference to the accompanying figures.