GB2486452A

GB2486452A - A wading indicator for a vehicle

Info

Publication number: GB2486452A
Application number: GB1021268.6A
Authority: GB
Inventors: Thuy-Yung Tran; Edward Hoare
Original assignee: Land Rover UK Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2010-12-15
Filing date: 2010-12-15
Publication date: 2012-06-20
Also published as: GB201021268D0

Abstract

A wading indicator for a vehicle 10 comprises an ultrasonic parking distance control sensor 13 on the front bumper of the vehicle 10. The parking sensor has a diaphragm which vibrates in use, there being a control unit (not illustrated) which is adapted to measure the diaphragm settling time between successive pulses thereof. Wading is detected by sensing the difference in the settling time in water and in air. Another way of detecting wading is by sensing the difference in time of flight of an ultrasonic signal in water and in air. Other embodiments are disclosed.

Description

Improvements in Detection Systems of Vehicles This invention relates to detection systems of vehicles, and in particular to detection of water at wading depth.

Road vehicles are designed to travel through a body of water to a finite depth.

Beyond this limit there is a danger of injury to occupants and the possibility of the vehicle being carried by the water. The vehicle engine and electronics may be vulnerable to damage if the prescribed maximum wading depth is exceeded.

WO-A-03/002378 discloses the use of uhrasonic parking distance control sensors to sense the presence of water. In use the vibration of the sensor diaphragm is attenuated when in the presence of water, and the change in response is detected by an electronic control unit. This document recognizes that attenuation of the sensor diaphragm may be due to other reasons, and accordingly discloses methods of increasing confidence in a positive indication of wading.

According to a first aspect of the invention there is provided a wading indicator for a vehicle, said indicator comprising an ultrasonic parking distance control sensor, said sensor having a diaphragm which vibrates in use, and a control unit adapted to measure the diaphragm settling time between successive activations thereof Such an arrangement allows the settling time in air to be distinguished from the settling time in water, the latter being significantly faster. The interval between successive activations, or signal pulses, is selected to be greater than the settling time of the diaphragm. Accordingly the control unit can provide an input to a vehicle data bus indicative of the sensor being underwater. Typically such parking sensors are mounted on a vehicle at bumper height, which is a suitable height for detecting wading.

The measurement of settling time better allows the presence of water at the diaphragm to be distinguished from mere mechanical pressure on the sensor. Detecting settling time for several sensors gives increased confidence that the vehicle is partly immersed.

According to a second aspect of the invention there is provided a wading indicator for a vehicle, said indicator comprising a plurality of ultrasonic parking sensors and a control unit adapted to measure the time of flight of an ultrasonic signal from one sensor to another.

Such an arrangement allows the time of flight in air to be distinguished from the significantly faster time of flight in water, and accordingly the control unit can provide a suitable input to the vehicle data bus indicative of the flight path being underwater.

In a preferred embodiment, one or more pairs of sensors is successively pulsed in order to obtain two-way time of flight information, and thereby increase confidence of an underwater indication. In the alternative one or more sensors is operated at a different frequency from one or more other sensors so as to permit an ultrasonic signal in one direction to be distinguished from an uhrasonic signal in another direction.

It will be appreciated that muhiple parking distance control sensors can be used both for parking distance control and in the aspects of the present invention, so as to give an indication of vehicle wading at minimal additional cost. Moreover, the described aspects of the invention can be electronically enabled whilst the parking distance control system is also enabled, thus obviating any switching system. Nevertheless, the vehicle driver may be provided with a means of enabling or disabling a wading indicator according to the invention. The outputs from a distributed sensor array can indicate whether a portion of a vehicle is partly immersed, and thus the approximate inclination thereof The first and second aspects may further include a vehicle tilt sensor indicative of fore and aft vehicle inclination whereby the control unit is adapted to give a predictive indication of water depth at a point ahead of the vehicle. Thus upon first sensing of water, the control unit will assume a constant angle of vehicle advance, and thus be able to give advance warning of the distance beyond which the safe wading depth of the vehicle will be exceeded, for example by message or graphic on the driver display.

The control unit may also be adapted to prepare or enable other vehicle systems for deeper water. Similarly prediction of a vehicle leaving water may be made by this means, and thus give an appropriate indication to a driver, and/or prepare, and/or enable vehicle systems for dry land.

In this adaptation, a change in vehicle fore and aft inclination may also be detected by continual sampling of tih sensor output(s), so that the control unit is adapted to give predictive information of a likely change in slope, and thus whether the slope is increasing or decreasing.

According to a third aspect, the invention provides a method of indicating wading of a vehicle fitted with a uhrasonic parking distance control sensor, the method comprising the steps of: determining the sensor diaphragm settling time in air; repeatedly checking said settling time when the sensor is enabled; detecting a substantially reduced settling time; and provided an input to the vehicle control system indicative of said substantially reduced settling time, so as to indicate immersion of the sensor diaphragm.

It will be appreciated that the settling time may be repeatedly checked whilst the sensor is indicating wading, and further that the method may include the step of providing an input to the vehicle control system indicative of a resumption of normal settling time, which is substantially greater in air. It will further be understood that inputs may be delayed until a pre-determined number of successive checks have indicated a substantial change in sealing time.

According to a fourth aspect of the invention, there is provided a method of indicating wading of a vehicle fitted with a plurality of ultrasonic parking distance control sensors, the method comprising the steps of: determining the time of flight in air of an ultrasonic signal from one sensor to another sensor; repeatedly checking the time of flight when said sensors are enabled; detecting a substantially reduced time of flight; and providing an input to a vehicle control system indicative of said substantially reduced time of flight, so as to indicate partial immersion of the vehicle.

As for the third aspect, this method can also provide an input indicative of a resumption of normal time of flight, and include a delay so that a plurality of successive checks indicate a change of state. A typical time of flight in water will be three times faster than a time of flight in air, and thus readily distinguishable.

It will also be appreciated that many pairs of sensors may be linked in the method of the fourth aspect, so as to indicate with confidence whether a vehicle is partly immersed in water, and to indicate which portions of the vehicle are immersed.

In the third and fourth aspects, it will be appreciated that the step of determining the normal (air) diaphragm settling time and/or time of flight, may be performed repeatedly -for example upon tuning of the vehicle ignition switch -or may be pre-determined and stored in a look-up table of a vehicle control system. Likewise the settling time and time of flight in water may be similarly pre-determined and held in a look-up table. Other arrangements for storing and comparison of the sensed values are possible.

The means and methods of the first to fourth aspects may provide a suitably enabled parking distance control sensor or sensors, and be used in conjunction with a tilt sensor to give predictive information to the driver, and to prepare or enable vehicle systems.

According to a fifth aspect of the invention, a wading indicator of a vehicle consists of one or more appropriately enabled parking distance control sensors, a downwardly facing sensor of the same kind adapted for mounting high on a vehicle, and a control unit adapted to measure that the output of said downwardly facing sensor is within a prescribed range.

Such a downwardly facing sensor may be for example be mounted on the vehicle bonnet, tailgate or boot lid at a distance above the parking sensors -which are typically at vehicle bumper level -and can detect the surface of water in which the vehicle may be partly immersed. The downward facing sensor(s) may be enabled only when the bumper mounted sensors indicate immersion in water, so as to avoid false positive signals, for example from an animal passing beneath the downward facing sensor. The downward facing sensor is preferably mounted above the maximum wading depth of the vehicle, so as to avoid potential immersion thereof It will be appreciated that once enabled, the maximum distance between the high mounted sensor and the water surface will be known, and accordingly the output of the high mounted sensor can be considered highly reliable if falling within prescribed distance limits.

The control unit of the fifth aspect may further be adapted to calculate the distance from the downwardly facing sensor to the surface of the water, thereby to allow the depth of water to be calculated.

It will be appreciated that the latter step requires the arithmetical step of subtracting the measured distance from the known heights of the downward facing sensor above ground. This height may be stored in a look-up table of a vehicle control system.

According to a sixth aspect of the invention, there is provided a method of determining the depth of water in which a vehicle is partly immersed, and comprising the steps of: determining that a vehicle is at wading depth by the use of one or more ultrasonic parking detector sensors; enabling a downwardly facing ultrasonic sensor mounted high on the vehicle; determining that the distance sensed by said downwardly facing sensor is within a prescribed range; and providing an input to a vehicle control system indicative of said distance falling within said range.

The method may include the alternative steps of: determining the distance sensed by said downwardly facing sensor; calculating the depth of water by reference to the height of said sensor above ground; and providing an input indicative of water depth to a vehicle control system.

In this specification reference to vehicle control systems, controllers and control units is intended to include any suitable electronic vehicle system or systems, typically including memory and processor functions.

According to a seventh aspect of the invention, there is provided a vehicle having an uhrasonic parking distance control sensor, a means of indicating when said sensor is immersed, and a switching device to re-calibrate the output of said sensor between operation in air and in water.

Such an arrangements permits a conventional parking distance sensor to be used when immersed to detect underwater objects and the distance thereof from the sensor. It is well-known that the time of flight of an ultrasound signal is faster in water than in air, and accordingly re-calibration is required for the correct distance to be indicated.

This aspect of the invention permits underwear use of the sensor at minimal additional cost, and may be a substantial benefit in avoiding contact with underwater obstructions.

More than one parking distance sensor of a vehicle may be enabled according to this aspect, including both front and rear mounted sensors.

According to an eight aspect of the invention, a method of detecting underwater objects from a vehicle having an ultrasonic parking distance control sensor comprises the steps of: detecting that said sensor is underwater, and recalibrating the output of said sensor for operation in water.

The method may further include the step of recalibrating the sensor output for operation in air when the sensor re-surfaces.

Calibrations may of course be held in a control unit of the vehicle, for example in a

look-up table.

In a preferred embodiment, the ultrasound sensor is itself the means of indicating that the sensor is immersed, using for example the means and methods described according to the first to fourth aspects of the invention. A downward facing sensor may provide the means of indicating immersion, by suitable water depth calculation.

Confidence in correct detection of partial immersion can be increased by reference to other vehicle systems, in particular electronic sensors indicative of vehicle attitude and movement.

Thus, for example, electronic inputs from vehicle sensors indicative of pitch and roll, such as downward firing sensors at the vehicle corners, may be combined and/or compared with signals indicative of partial vehicle immersion so as to gain increased confidence of signal accuracy, and to further modify vehicle response.

It will be understood that the dynamic response of a vehicle in water may be quite different from the dynamic response in air. Roll and pitch characteristics will significantly change due to the additional damping effect of water.

According to a ninth aspect of the invention, there is provided a vehicle having a movement sensor indicative of one of roll and pitch of the vehicle body, a wading sensor indicative of the vehicle being in one or air and at wading depth in water, and a comparator to indicate whether vehicle body movement is within a range associated with the output of said wading sensor.

This arrangement allows confirmation that vehicle movement (roll, pitch or a combination of both) is within a predetermined band, which may be contained with a look-up table of a vehicle control system. In the event that outputs from the sensors cannot be correlated, a warning may be indicated to the driver, or other vehicle actions may be automatically initiated.

In a development of this aspect, the vehicle may further include a sensor indicative of wading depth, and the comparator may select a permissible range according to the sensed wading depth.

In yet a further development, the vehicle may include a means of adjusting roll and/or pitch, and a controller thereof said controller adjusting the response of the vehicle body according to the output of the wading sensor and/or the depth of water sensed.

Such an arrangement may improve comfort and safety of persons with in the vehicle when wading, and improve vehicle traction.

Ultrasonic parking distance control sensors, as described above, can provide a suitable indicator of wading and wading depth.

In a tenth aspect there is provided, a method of determining whether movement of a vehicle body is within a prescribed range, and comprising the steps of: sensing whether the vehicle is in air or is wading, sensing body movement by detecting one of roll and pitch, comparing body movement with a range associated with movement in air and at wading depth, and indicating whether or not body movement is appropriate.

Movement in roll and pitch may be sensed to give an appropriate vector, and associated ranges may be provided for comparison.

The method may include the step of sensing wading depth above a minimum, and determining whether body movement is within a range associated with the sensed depth.

In an eleventh aspect, the invention provides a vehicle having an attitude sensor indicative of a vehicle body angle with respect to a horizontal plane, a wading sensor indicative of the vehicle being in one of air and at wading depth in water, and a comparator to indicate whether vehicle attitude is within a range associated with the S output of said wading sensor.

Such a comparator may be used to confirm that the vehicle is at a safe attitude when wading, the permissible range of attitudes being for example much less than when on dry land. The attitude sensor may comprise a mathematical combination of the outputs of two or more individual sensors, for example fore and aft, and side to side tilt sensors.

A sensor indicative of wading depth may be included, the permissible range of attitudes being different according to the detected wading depth.

Detected wading depth may be an average of depths detected around the vehicle, or may be the maximum detected depth.

The permissible range(s) may be determined in advance, and retained in a look-up table of a vehicle control system.

In a twelfth aspect, the invention provides a method of determining whether attitude of a vehicle body is within a prescribed range, and comprising the steps of: sensing vehicle attitude, sensing whether the vehicle is in air or is wading comparing vehicle attitude with a range associated with permissible attitude in air and at wading depth, and indicating whether vehicle attitude is appropriate.

The method may further include the step of sensing wading depth above a minimum, and determining whether vehicle attitude is within a range associated with the sensed depth.

An ultrasound parking distance control sensor or sensors, as described above are preferably used as sensors of wading and wading depth. Conventional vehicle devices such as low-g accelerometers and gyroscopes can be adapted to give information about instant vehicle attitude, for example fore and aft tilt, and side to side lean.

The aspects of the present invention relate to uhrasonic sensors, vehicles and methods of use. It will however be appreciated that the inventions may be retrofitted to existing vehicles as a combination of hardware and software. Such means may adapt an existing vehicle with parking sensors to detection of wading or wading depth. In this specification use of the term wading depth' indicates wading at a depth sufficient to be detected by appropriately mounted parking sensors, but does not indicate any particular depth, nor that any vehicle with parking sensors can be adapted to wade merely by adaptation of the sensor controller. As is well understood, many aspects of a vehicle may require modification to ensure successful wading, but the present invention provides a convenient and economical way of establishing wading and the depth of wading.

Reference in this specification to control unit' includes reference to any suitable controller for interpreting, translating and acting upon signals of a sensor. The control unit may comprise a distributed system and/or may be incorporated within a vehicle control system. Signals may be analogue or digital.

Other features of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a schematic illustration of predictive vehicle depth estimation using an ultrasonic parking sensor; Fig. 2 corresponds to Fig. 1 and shows a variation in vehicle slope; Fig. 3 illustrates graphically the change in slope of Fig. 2; Fig. 4 illustrates on a depth sensor for use in predictive vehicle depth estimation; Figs. S & 6 illustrate front mounted downward facing ultrasonic detectors.

Fig. 1 illustrates a vehicle (10) entering water having a surface (11) and on an inclined slope (12). An ultrasonic parking distance sensor (13) on the front bumper exhibits a change in response when entering water, and thus is an indicator of wading.

Within the vehicle a tilt sensor (14) gives to the vehicle control system an indication of fore and aft inclination (cx) (15).

The vehicle control system can predict water depth ahead of the vehicle, assuming a constant angle of inclination using the formula: D=RJancx +h where D is the estimated depth; R is the distance to the point of estimation (16) -for example 1 metre; cx is the angle of inclination; and h is the approximate mounting height of the sensor. It will be appreciated that the value of h may be fixed in relation to actual sensor height above ground in the horizontal vehicle condition, or according to a vehicle suspension height setting. A more accurate calculation of h may take into account vehicle inclination cx so as to give the true vertical dimension when the vehicle is inclined.

Fig. 2 illustrates a case where the angle of inclination (isa) increases to give an increased slope (22). The control system of the vehicle may monitor a change in angle of inclination so as to indicate increasing slope, and thus a more imminent point at which the vehicle may reach maximum wading depth.

Fig. 3 illustrates graphically the path estimation of the vehicle according to successive increasing angles of inclination (23, 24) and a maximum wading depth (25) of 0.6 m.

Fig. 4 illustrates a vehicle having a device (31) (shown schematically) for measuring depth of water. Any suitable device may be used, in particular a bonnet mounted downward facing ultrasonic parking sensor.

S

Thus the continual measurement of actual immersion depth may be compared with the estimated immersion depth h to predict the depth of water D ahead of the vehicle.

Depth estimation may be for a single distance ahead of the vehicle, for example 1 m, or at a number of discrete points, for example 50 points at 100 mm intervals.

The distance to maximum wading depth may be presented to the driver in the form of a dashboard waming (40), in analogue or digital form.

Fig. 5 illustrates schematically a vehicle (10) having a bonnet mounted downward facing parking sensor (50) adapted to sense the surface of the water and having a target range (51). Knowing the mounting height (52) of the sensor, the depth of water (53) can be calculated. A look-up table may give a mounting height associated with a vehicle suspension height setting. A test mode may be provided for calibrating the mounting height on dry land, notwithstanding that the sensor (50) is enabled only whilst wading is detected.

Fig. 6 illustrates a vehicle not level but on an incline (12). In this case information from a fore and aft tih sensor provides vehicle inclination, and thus a correction factor (54) for the water depth calculation.

In both Fig. S and Fig. 6, information concerning water depth, tilt angle can be broadcast on a vehicle Bus system.

The arrangements of Figs. S and 6 apply equally to forwards and reverse movement, using sensors at the leading edge of the vehicle.

A downward facing uhrasonic parking sensor may be provided at the front of the vehicle, for example centrally in the radiator grill or on the bonnet, or at the side so long as it has an output cone projecting ahead of the vehicle front wheels. Thus a sensor may be provided at the side and/or within the external body panels so long as a clear forward and downward line of sight is maintained. The height of the downward facing sensor is determined by vehicle body design and the maximum wading depth for which the sensor is intended to be operable.

The wading depth sensor may be activated automatically, or on demand by the driver.

A driver override may be provided. The system of wading and/or depth sensing may be operational only below a pre-determined wading speed, and the vehicle speed may be limited to a pre-set maximum during wading.