GB2486453A - A vehicle control system including a wading sensor - Google Patents

Abstract

A vehicle 10 has a wading sensor, typically taking the form of parking sensors 11, 12, 16, 17 and may include a control unit adapted to implement an alternative or modified vehicle control strategy once wading has been sensed. The wading strategy may change many vehicle functions, alone or in combination, and may be further responsive to depth of wading.

Description

Vehicle Control System This invention relates to a vehicle control system, and particularly to a system adapted to a wading vehicle.

Road vehicles are designed to wade through water at a prescribed depth, according to the vehicle make and model Vehicles with off-road capability may be designed to wade at a considerable depth of water (e.g. 750 mm), and are typically provided with appropriate protection of the vehicle engine, electrical systems and the like.

It may be advantageous to take some actions consequent upon detection of wading, so as to place the vehicle in a state better suited to wading. WO-A-03/002378 discloses closing of ventilation flaps to prevent ingress of water to an engine compartment, switching off an engine cooling fan and/or raising the vehicle ride height when partial vehicle immersion is detected.

According to the present invention there is provided a control system of a vehicle having a wading sensor adapted to indicate wading above a predetermined depth of water, said control system being adapted to automatically implement one or more of the following vehicle control strategies upon detection of wading by said sensor: -change of Terrain Response mode -change of throttle mapping -change of gear selection mode -change of highllow range mode -activate headlights -select higher air intake path -adapt tyre pressures to wading -change steering response/feel -change differential control -change torque-vectoring control -activate hydraulic lock sensor of engine -change hybrid vehicle drive mode -activate heating, ventilation and air conditioning system (HYAC) -dc-activate engine fuel saving mode -delay regeneration of exhaust particle filter -partially flood vehicle -dc-activate door locks -open sun roof The vehicle control system is further adapted to re-implement a standard control strategy upon a failure to detect wading by said sensor. A plurality of wading sensors may be provided, and may operate individually or in conjunction to indicate wading.

In this specification a standard control strategy includes any control strategy appropriate to vehicle operation when wading is not indicated.

The control strategies implemented by the control system are typically retained in a memory of the vehicle control system, and may be in a look-up table with reference to other vehicle control inputs. Thus, for example, a change of control strategy may be dependent upon the depth of wading, for which purpose a wading depth sensor of any suitable kind may be provided on the vehicle. The wading depth sensor may be enabled only whilst wading is indicated by a wading sensor.

A change of control strategy may be implemented immediately or progressively.

Progressive implementation allows a driver to become familiar with, for example, a change in response to a given driver input.

A change in control strategy may also be implemented with delay according to the parameters retained in a memory, or according to other vehicle control inputs. Thus for example the HVAC system may remain enabled for a period after a failure to detect wading. Such an arrangement may be useful in passage through successive stretches of shallow water, or to allow the effects of wading to be fully cleared before resumption of a standard control strategy.

Each aspect of the invention is now described independently of each other aspect.

The aspects may be combined, as desired.

Change of Terrain Response Mode A vehicle with off-road capability may have a driver switchable control for automatically placing the vehicle in best operating mode according to the terrain over which the vehicle is travelling. Thus a driver may be able to switch between road, mud and snow, sand, and rock crawl modes, each of which will modify the vehicle response so as to enable the vehicle to best perform within the full available operating envelope.

According to this aspect of the invention, upon detection of wading, the control system may automatically implement a Terrain Response mode, such as rock crawl.

This arrangement provides better vehicle performance for the inexperienced driver, and may protect the vehicle from damage. The cost of implementation is minimal where Terrain Response is already provided on the vehicle.

In an enhancement, the control system may present the driver with a choice of modes, for example rock crawl and sand, or default to the best mode indicated by other vehicle sensors. For example wheel slip sensors may provide information on wheel grip, and thus whether rock climb mode or mud and snow mode is appropriate. The control system may include a driver override.

Change Throttle Mappiqg Upon detection of wading, the control system may implement a throttle map better suited to driving in water. Thus, to permit better control of engine revolutions, the throttle map may limit maximum engine revolutions and/or increase throttle pedal travel for a given engine response.

Change Gear Selection Upon detection of wading the control system may inhibit the selection of certain gear ratios, alter the speeds at which automatic ratio changes occur, or select an appropriate (low) ratio. This arrangement can avoid loss of drive as gear ratios change, or are changed, during wading, and also promotes driver confidence. An indicator to the driver may show, for example, a locked or selected gear ratio.

HighlLow Range Mode Similarly a manual or automatic change of speed range may be inhibited or prohibited, or a range may be automatically selected, typically low range in a dual range transmission.

Headlight Activation Headlights may be activated upon detection of wading.

Select Higher Intake Path Upon detection of wading, a higher air intake path may be selected for the engine and/or HYAC system. The intake path may for example comprise upper and lower paths and an electronically controlled flap or butterfly valve to select one or other path on demand.

Adapt Tyre Pressure to Wading Tyre pressure may for example be reduced upon detection of wading so as to improve traction and footprint. The electronic tyre pressure monitoring system (TPMS) provides an electronic signal of real time tyre pressure, and a suitable release valve operated by e.g. radio or infrared signal may be provided on each vehicle wheel.

Change Steering Response/Feel Many vehicles can in whole or in part adapt steering response and feel electronically.

For example electric power assistance may be increased upon detection of wading, and or steering damping rates may be changed. This arrangement permits the vehicle to provide an unchanged steering response notwithstanding the commencement of wading. In other words the steering response and feel may resemble that of driving on dry land. Alternatively it may be desirable to deliberately introduce a variation of response and/or feel in order for example to prevent sudden or large steering wheel inputs.

Where wireless steering is provided, the angle of steering vehicle input and or rate of turning may change in relation to road wheel movement so as to improve driver control in water.

S

Change of Differential Control Upon detection of wading, the control system may lock or provide limited slip in one or more differential gears of the vehicle in order to improve traction. Such locking may be in conjunction with a limitation of vehicle speed.

Torque Vectoring Control Torque vectoring, that is to say wheel to wheel differentiation of driving torque, may be altered upon detection of wading to counter side slip of the vehicle or drift in a stream path. The control system may for example switch to an alternative torque vectoring map. Torque vectoring may be provided between wheels of each axle, or between individual wheels of each axle, or differentiate each wheel individually so as to best apply available drive torque.

Engine Lock Sensor When wading there is a danger of water ingestion in the engine air inlet, and consequent damage due to a hydraulic lock in the engine cylinders. Upon detection of wading, an engine lock sensor may be enabled so as to switch off the engine upon detection of moisture in the engine inlet tract. Any suitable moisture sensor may be used, typically in the air filter housing and preferably on the upstream side thereof The moisture sensor will be able to distinguish from damp or humid air, and be sensitive to a threshold indicative of wading. The moisture sensor may detect accumulation of liquid in a trap within the air inlet tract. The engine lock sensor preferably re-enables the engine upon the moisture level falling below a pre-determined level.

Hybrid Vehicle Drive Mode Upon detection of wading, the control system may be enabled to switch off an internal combustion engine, and so that the vehicles relies upon an alternative drive, such as an electric drive. Such an arrangement avoids the risk of water ingestion to the engine, whilst maintaining drive to the vehicle wheels. Suitable waterproofing of the alternative drive is of course required.

The control system may disable the intemal combustion engine so that the altemative drive automatically takes over without further measures, or the control system may actively enable the alternative drive in a wading mode, which may for example limit vehicle speed, engage an alternative throttle map and make other desirable changes to vehicle response.

HVAC System Upon detection of wading the HYAC system may start or switch to a wading mode which is best suited to air with a high moisture content. Thus the HVAC system may immediately enable electrically heated screens, in particular the windscreen, and may blow air over the screens in de-misting mode. The air-conditioning system may be engaged or enabled to blow a high volume of dry air over the interior of the screens, so as to prevent misting and to clear the screens of moisture.

The HVAC system may also switch to a higher level air inlet, so as to limit the risk of moisture/water ingestion.

Engine Fuel Saving Mode Upon detection of wading, an engine fuel saving mode may be deactivated so as to minimize the risk of stranding in water. Thus a vehicle may have a fuel saving mode which normally turns off a vehicle engine when the vehicle is stationary, and for example restarts the engine automatically upon throttle pedal movement. This strategy can be temporarily disabled during wading so as to avoid any risk of the vehicle engine failing to re-start in water, and to give confidence to the driver that control of the vehicle is being maintained.

Particle Filter Regeneration Many internal combustion engines have a particle filter in the exhaust system, which is periodically re-generated by raising the temperature thereof to cause combustion of the contents. Regeneration occurs when required, for example by reference to increasing back pressure, and may be temporarily suspended upon detection of wading. The control system for example flags the engine control unit to block regeneration during the wading event, and thereby avoid the engine working in a temporarily adjusted mode, avoid unnecessary thermal shock to the particle filter and/or exhaust system, and avoid the risk of incomplete regeneration. Regeneration is generally indicated when the particle filter is at rather less than full capacity, and accordingly there is no significant disadvantage in delaying regeneration during a wading event.

Partially Flood Vehicle Sealed vehicles may become dangerously buoyant when wading as the water level reaches the underside of the vehicle body. Accordingly it may be desirable to raise the vehicle body with respect to the wheels upon detection of wading, and this is a useful solution where adjustable height suspension is fitted to the vehicle.

The buoyancy effect may also be countered by partially flooding the vehicle upon detection of wading, in particular detection of wading at a pre-determined depth of water. The vehicle may for example be fitted with actuators to open flaps to admit water into normally closed compartments of the vehicle, such as a spare wheel well.

One or more vehicle doors may be unlatched to admit water into the interior of the vehicle body -for example to allow flooding of the vehicle floor.

Unlock Doors and Open Sunroof Upon detection of wading the control system may also automatically unlock one or more vehicle doors and open the or each sunroof (if fitted) so as to permit the occupants a ready means of escape in the event of difficulty. For example upon sudden entry of deeper water there may be a risk of an unpredicted engine malfunction, loss of traction and the like, as a consequence of which the occupants may require to escape quickly. This aspect of the invention places the vehicle in escape ready mode, without substantially increasing the risk of water entering the vehicle body in an uncontrolled manner.

In all of the aforementioned aspects, the control system will re-enable the relevant vehicle protocols when wading is no longer detected. Tmplementation may be partial or progressive depending upon the control strategy. Thus for example headlights may be immediately returned to normal operation, where the HYAC system may resume normal operation gradually.

In some cases the severity of the control system protocol may be dependent upon the sensed wading depth. Thus upon sensing a minimum wading depth some changes of vehicle state will automatically be implemented, for example unlocking doors. Other vehicle states may progressively move to a more altered state depending on water depth, for example change of steering response and feel.

Not all actions need be implemented at the same wading depth, provided that several wading depths can be indicated to the control system. Thus partial vehicle flooding will not be implemented until deep water is encountered, whereas change of throttle mapping may occur at a much lower depth of water.

In each case an action consequent upon wading may be indicated to the driver via the HMI (Human-Machine Interface). This may be in the form of a graphic, for example headlights-on indicator, or in the form of a message, for example low range engaged'.

Fig. 1 schematically illustrates a vehicle having a wading sensor and a wading depth sensor.

With reference to Fig. 1, a vehicle (10) has ultrasonic parking distance sensors (11,12) mounted in the front and rear bumpers and having respective output cones (13, 14).

The sensors both transmit and receive, and are accordingly capable of being used in a system for detecting obstructions, for example bollard (15).

If immersed, the response of such a sensor will change, and can accordingly be used to sense wading at the depth of the sensor (11, 12). Upon detection of wading, different vehicle control strategies may be implemented.

A high mounted parking distance sensor (16, 17), for example mounted on a bonnet or tailgate can be used to detect the ground surface by means of a downwardly directed output cone (18, 19).

The downward facing sensors (16, 17) also receive a reflection from the surface of water, and can thus be used to indicate depth of water since the mounting location on the vehicle is known.

Front and rear mounted sensors allow detection for both forward and rearward vehicle motion, and can also give an indication of vehicle inclination.

Other means of detecting wading and depth of wading may be used.