METHOD OF CONTROLLING A VEHICLE TO ADAPT DYNAMIC PERFORMANCE OF THE VEHICLE TO THE PSYCHO-PHYSICAL STATE OF THE DRIVER

TECHNICAL FIELD

The present invention relates to a method of controlling a vehicle.

The present invention may be used to advantage in a car, to which the following description refers purely by way of example.

BACKGROUND ART

To make driving safer, modern cars are equipped with various electronic driving aid devices, such as an ABS (Anti Block System, to prevent the wheels locking when braking) , ESP (Electronic Stability Program, to control stability of the vehicle) , ASP (Anti Skid Program, to prevent the drive wheels from skidding) , and electronic suspension control (to adjust mechanical response of the suspensions to external stress) .

Some cars are also equipped with a selection device for the driver to communicate a given dynamic performance of the car to a central control unit, which accordingly

adjusts the intervention parameters of the electronic driving aid devices to match dynamic performance of the car as closely as possible to the driver's choice. The selection device enables dynamic performance of the car to be adapted to the driver's own personal driving style and to current weather conditions, thus greatly improving driving safety, especially in severe weather conditions (heavy rainfall, snow, or ice) .

One example of a selection device of the above type is described in Patent Application WO2004087484A1, in which the selection device comprises a switch integrated in the steering wheel of the car, and which can be turned to five settings, each corresponding to a respective dynamic performance of the car. Drivers, however, frequently miscalculate - in particular, overestimate - their own driving skill and, above all, their own psycho-physical state, with the result that the dynamic performance selected by the driver simply represents the driver's preference, and bears no relation to the driver's actual psycho-physical state or skill. In which case, the dynamic performance selection by the driver actually reduces driving safety, by placing the driver at the wheel of a car that does not respond suitably to the driver's actual psycho-physical condition.

The problem of accurately assessing the driver's psycho-physical state is dealt with widely in technical literature, much of which proposes determining various

psycho-physical parameters of the driver, by which to assess the driver's psycho-physical state and accordingly emit warning signals, by acting on on-vehicle systems, to keep the driver alert, and/or stop the vehicle in the event of the driver passing out. The following are examples of documents dealing with precise assessment of the driver's psycho-physical state.

Patent Application US2005015016A1 describes a method which analyzes the driver's brain waves to determine the driver's mental condition and stress level.

Patent Application US2003146841A1 describes a method of determining the driver's stress level using various biomedical sensors, so that appropriate steps can be taken when the stress level exceeds a predetermined alarm threshold.

Patent Application GB2394288A describes a steering wheel fitted with various sensors for determining various physical characteristics of the driver, by which to assess the psycho-physical state of the driver. Patent Application WO02096694A1 proposes monitoring the driver's psycho-physical state and accordingly acting on on-vehicle control units to ensure the safety of the driver. More specifically, in the event of the driver passing out, the correct vehicle trajectory is maintained, by acting on electric control of the power steering system, and the vehicle is slowed down and eventually stopped, by acting on the cruising control.

Patent US5942979A1 proposes determining the driver's

physical condition. In an emergency situation, the driver is warned by visual or sound signals, and the vehicle can be stopped automatically by acting on the brake and/or injection system. All the proposed solutions in existing literature, however, relative to assessing the driver's psychophysical state, deal with determining and controlling imminent hazard situations, in which the driver is drowsy or unconscious. And nowhere is any mention made of the possibility of employing biomedical parameters to enhance driving pleasure and reduce driving fatigue.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a vehicle control method designed to enhance driving pleasure and reduce driving fatigue.

According to the present invention, there is provided a vehicle control method as recited in the accompanying Claims.

BRIEF DESCRIPTION OF THE DRAWINGS A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a schematic plan view of a car implementing the method according to the present invention;

Figure 2 shows a larger-scale view of a detail in Figure 1 ;

Figure 3 shows a graph illustrating, schematically,

various transfer functions employed in interpreting the driving commands of the Figure 1 car.

BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates a car having two front wheels 2, two rear drive wheels 3, and a front internal combustion engine 4 which produces a drive torque transmitted to rear drive wheels 3 by a power train 5.

Power train 5 comprises a clutch 6 housed in a casing integral with engine 4, and which connects the drive shaft of engine 4 to a propeller shaft 7 terminating in a mechanical power transmission 8 at the rear. A self-locking differential 9, with electronic lock percentage control, is cascade-connected to transmission 8, and from which extend two axle shafts 10, each integral with a respective rear drive wheel 3.

Car 1 also comprises an electronically controllable brake system, which acts on wheels 2 and 3; and a known suspension system (not shown in detail) designed to electronically control suspension response.

The car also comprises a passenger compartment 11 housing a steering wheel 12 for imparting a steering angle to front wheels 2; a brake pedal 13 for controlling the brake system; an accelerator pedal 14 for controlling the drive torque of engine 4; and a device 15 for controlling transmission 8 and fitted to steering wheel 12.

Car 1 comprises a central control unit 16 for

controlling operation of the active parts of car 1, and which is connected to a number of sensors 17 distributed inside car 1 to real-time acquire respective dynamic parameters of car 1, such as the speed of car 1, the steering angle of car 1, the yaw speed of car 1, lateral acceleration of car 1, longitudinal acceleration of car 1, the rotation speed of each wheel 2, 3, and the drive torque generated by engine 4. Central control unit 16 may obviously comprise a number of physically separate processing units connected, for example, by a data BUS. Moreover, as opposed to a physical sensor 17, an estimation algorithm, implemented by central control unit 16, may be employed to determine one or more parameters of car 1. Central control unit 16 internally performs the functions of various electronic driving aid devices, and, in particular prevents blocking of wheels 2 and 3 when braking (ABS function) , prevents skidding of rear drive wheels 3 (ASP function) , controls the stability of car 1 (ESP function) , electronically controls suspension response, electronically controls power operation of transmission 8, and electronically controls the lock percentage of self-locking differential 9. Moreover, central control unit 16 also adjusts the operating parameters of the active parts of car 1 (typically engine 4 and the electronic driving aid devices described above) to adjust dynamic performance of car 1.

To allow the driver to actively select the dynamic

performance of car 1, a selection device 18 (shown more clearly in Figure 2) is provided in passenger compartment 11 of car 1, and can be operated by the driver to communicate a personally selected dynamic performance of car 1 to central control unit 16. As shown in Figure 2, selection device 18 may assume five settings (indicated A-E for simplicity) , each corresponding to a respective dynamic performance of car 1.

Passenger compartment 11 is also equipped with a number of biometric and psychometric sensors 19

(preferably non-invasive) for acquiring and communicating to central control unit 16 a number of psycho-physical parameters of the driver of car 1, which are employed by central control unit 16 to assess the driver's psycho- physical state. It should be stressed that the psychophysical parameters are both physiological and non- physiological, i.e. psychological and emotional.

Biometric and psychometric sensors 19 may, for example, comprise a facial television camera to monitor the facial expression, and so determine the mood, of the driver (relaxed, happy, sad, worried, tense, etc.); another television camera monitor the driver's gestures and movements in the driving seat; a piezoelectric measuring device to measure the driver's respiration rate and intake; a device for measuring the driver's blood pressure and heartbeat (electrocardiogram) ; a device for monitoring the driver's eyes (blink rate) to determine alertness of the driver; a device for monitoring the

driver's electrical brain activity (electroencephalogram) ; a device for determining the driver's surface temperature; a device for determining the conductivity of the driver's skin; and a device for determining the driver's grip on steering wheel 12.

Given the assessment of the driver's psycho-physical state, central control unit 16 adjusts dynamic performance of car 1 to adapt it accordingly. That is, central control unit 16 adjusts dynamic performance of car 1 as a function of the assessment of the driver's psycho-physical state and/or as a function of the driver's choice expressed by means of selection device 18.

In a preferred embodiment, adjusting the dynamic performance of car 1 as a function of the driver's psycho-physical state comprises determining whether the dynamic performance of car 1 is suited to the driver's psycho-physical state, and adjusting the dynamic performance of car 1 if it is not suited to the driver's psycho-physical state. To determine whether the dynamic performance of car 1 is suited to the driver's psychophysical state, dynamic performance of car 1 is assessed on the basis of the current values of a number of operating parameters of active parts of car 1, and the assessment of the dynamic performance of car 1 is compared with the assessment of the driver's psychophysical state. In other words, the dynamic performance of car 1 is adjusted by feedback control, in an attempt

to reduce the difference between the assessment of the dynamic performance of car 1 and the assessment of the driver's psycho-physical state.

For example, to adjust the dynamic performance of car 1 as a function of the assessment of the driver's psycho-physical state, a first group of operating parameters of active parts of car 1 is first adjusted, and a check is made to determine whether the change in the dynamic performance of car 1 produces a significant change in the difference between the assessment of the dynamic performance of car 1 and the assessment of the driver's psycho-physical state. If the change in the dynamic performance of car 1 produces no significant change in the difference between the assessment of the dynamic performance of car 1 and the assessment of the driver's psycho-physical state, the dynamic performance of car 1 may be adjusted further by either acting more forcefully on the first group of operating parameters of active parts of car 1, or acting on a second group of operating parameters of active parts of car 1.

In a preferred embodiment, central control unit 16 also determines the context in which car 1 is being driven (e.g. driving in city traffic, cruising on main roads or motorways, racing on main roads or motorways, racing on track), and the driver's psycho-physical state is assessed as a function of both psycho-physical parameters and the context in which car 1 is driven. In other words, the context in which car 1 is driven has

been found to have a significant effect on the driver's psycho-physical state. For example, minor stress is normal when driving in city traffic, but not when cruising along main roads or motorways; stress is normal immediately after emergency action (e.g. sharp braking when cruising along main roads) or in a prolonged traffic jam on a motorway; or a high state of alertness is normal when racing on track, but not when cruising along main roads or motorways. In other words, knowing the context in which car 1 is being driven helps to establish whether a stress condition is physiological and caused by external circumstances, or is rather a sign of some sort of driver disorder.

The context in which car 1 is driven is determined as a function of the performance time pattern of car 1 and/or the location of car 1, which performance and/or location are/is determined by central control unit 16. That is, given the location of car 1 (city, main road, motorway, track...) and its performance (slow, fast, racing drive mode, queuing...) , the context in which car 1 is being driven can be determined accurately. For example, sharp braking followed by a prolonged stop of the car clearly indicates an emergency situation quite capable of severely stressing the driver. As stated, dynamic performance of car 1 is adjusted by adjusting the operating parameters of active parts of car 1, e.g. engine 4, the electronic driving aid devices described above, and the driving commands imparted to the

control devices (i.e. steering wheel 12, brake pedal 13, accelerator pedal 14, and device 15 controlling transmission 8).

In a preferred embodiment, adapting dynamic performance of car 1 to the driver's psycho-physical state comprises making the dynamic response of car 1 to the driving commands imparted by the driver more direct and faster, as the driver's psycho-physical condition improves; and, conversely, making the dynamic response of car 1 to the driving commands imparted by the driver less direct and slower, as the driver's psycho-physical condition deteriorates.

In other words, the driver imparts driving commands by physically operating a number of control devices (steering wheel 12, brake pedal 13, accelerator pedal 14, and device 15 controlling transmission 8), the positions of which are determined by respective sensors (not shown) and transmitted to central control unit 16, which interprets the positions by means of corresponding transfer functions. Making the dynamic response of car 1 to the driving commands imparted by the driver more or less direct and more or less fast comprises increasing or decreasing the gain of the transfer functions interpreting the driving commands. An example of this is shown in Figure 3, which shows, schematically, four transfer functions, which assign a corresponding control (OUTPUT) to a given physical position of a control device (INPUT); the steeper the transfer function is, the more

direct and faster the response to a driving command is.

In a preferred embodiment, adapting the dynamic performance of car 1 to the driver's psycho-physical state also comprises delaying and/or reducing intervention of the electronic driving aid devices, as the driver's psycho-physical condition improves; and, conversely, accelerating and/or increasing intervention of the electronic driving aid devices, as the driver's psycho-physical condition deteriorates. Central control unit 16 therefore provides for adjusting and adapting the dynamic performance of car 1 to the driver's psycho-physical state, i.e. automatically and independently of the driver's conscious choice, and as a function of the driver's psycho-physical state. It should be stressed that the dynamic performance of car 1 may be adjusted to enhance driving safety, in the case of fatigue or sluggish response on the part of the driver, but also for enhancing driving pleasure and/or performance, in the case of an alert, responsive driver.