Motor Vehicle Driving Style Estimating System And Method

Abstract

A motor vehicle driving style estimating system comprises: a measuring apparatus of a motion quantity of the motor vehicle; a processing apparatus connected to the measuring apparatus and configured to: define a value of a space corresponding to a measuring path; calculate, based on the motion quantity, an estimate of an energy consumed by the motor vehicle along the measuring path; calculate a reference energy associated to a reference behavior of the motor vehicle along the measuring path; and calculate an indication of the driving style dependent on: a difference between the consumed energy and reference energy, and on the space value.

Description

TECHNICAL FIELD

The present invention refers to techniques for estimating the driving style of a motor vehicle adopted by a driver.

PRIOR ART

Different techniques of estimating the driving style of motor vehicle drivers to be used with reference to an estimate of the fuel consumption, safety of the driver behavior, or for generally evaluating his/her driving capabilities, are known.

Document WO-2011-101713 describes a method of estimating the driving style based on calculating an index obtained by the ratio between the difference of an energy consumed by the motor vehicle and a reference energy, and the reference energy itself.

Application EP-A-1780090 describes a method for defining the driving style of a motor vehicle driver, which comprises monitoring different magnitudes, among them: how many times the horn is used, the speed variation, the accelerator position variation, the angular speed obtained by the movements of the driving wheel. Then, the estimate is based on calculating the differences between these monitored magnitudes and predetermined threshold values.

Patent application EP-A-0777071 describes a method of controlling the automatic transmission of a vehicle as a function of the driving style of the driver based, among the other things, on the following information: opening of the fuel valve, vehicle speed, angular speed of the engine.

Patent application EP-A-1498297 describes a method of estimating the fuel consumption which instrumental in monitoring different magnitudes, among them there are: a signal of the rotation speed of the motive wheel, a signal of the rotation speed of the driving shaft, a cooling temperature signal, a fuel temperature signal.

SUMMARY

The Applicant has noted that the standard techniques of estimating the driving style are not satisfying because sometimes they do not enable to distinguish possible different behaviors of the drivers of a vehicle.

The object of the present invention is to provide a technique for estimating the driving style of motor vehicles which is adequately reliable.

The object of the present invention is met by a system for estimating the driving style as defined in claim 1. Preferred embodiments are defined in the dependent claims from 2 to 9. It is also an object of the invention a method of estimating the driving style as defined in claim 10.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will result from the following description of a preferred embodiment and variants thereof illustratively given with reference to the attached drawings, wherein:

FIG. 1 schematically shows an example of a system for estimating the driving style of a driver of a motor vehicle;

FIG. 2A shows the trend of the measured speed and reference speed with respect to a first driving example of a motor vehicle;

FIG. 2B shows the trend of the measured speed and reference speed with respect to a second driving example of a motor vehicle.

DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 shows an example of a system 100 for estimating the driving style of a driver of a motor vehicle. Particularly, the estimating system 100 comprises a measuring apparatus 1 and a processing apparatus 2 adapted to communicate with each other. Specifically, the estimating system 100 is also provided with a gateway device 3 (GTW) and with at least one presentation or report device 4 showing the results of the performed estimate.

Preferably, the measuring apparatus 1 is mounted on the motor vehicle and enables to provide electric signals, particularly digital signals, representative of cinematic magnitudes associated to the motion of the motor vehicle itself. The digital signals supplied by the measuring apparatus 1 can be a signal of the speed of the motor vehicle and, for example, also an acceleration signal of the motor vehicle itself. As an alternative, the measuring apparatus 1 can supply electric signals in an analog form which can be digitally converted for enabling, for example, numerical processings executed by a software.

According to a particular embodiment, the measuring apparatus 1 can comprise a speed transducer and acceleration transducer of the motor vehicle. To this purpose, the signals acquisition apparatus 1 is provided, for example, with an inertial measuring system 5 (IMU), per se known (known in the field as “inertial platform”), which comprises a computer and motion sensors adapted to supply the acceleration and speed signals (in terms of direction, sense and amplitude) of the motor vehicle.

Moreover, advantageously, the measuring apparatus 1 can be also provided with a positioning device 6 (GPS) such as a receiver operating in a satellite positioning system such as, particularly, the GPS (Global Positioning System). The receiver GPS 6 is capable of supplying, in addition to the motor vehicle position, also an associated speed signal.

With reference to the processing apparatus 2, this is, according to an embodiment, a data processing unit or a computer (provided with memories, computing units and interfaces communicating with the outer environment) adapted to receive the signals from the measuring apparatus 1 and to execute computing and processing operations for estimating the driving style of a particular driver of the motor vehicle. The processing apparatus 2 particularly comprises a microcontroller.

According to the schematic view in FIG. 1, the data processing unit 2 comprises the following modules (of a software type, for example): a space computing module 7 (SP-MOD), a consumed energy computing module 8 (E_U-MOD), a reference energy computing module 9 (E_REF-MOD), and an index computing module 10 (IDX-MOD).

Particularly, the space computing module 7 is configured for calculating the space (i.e. a distance) traveled by the motor vehicle along a measuring path. The consumed energy computing module 8 is configured for estimating an energy E_U consumed by the motor vehicle along the measuring path.

Moreover, the reference energy computing module 9 is configured for estimating a reference energy E_REF associated to a reference (or ideal) behavior of the motor vehicle along the measuring path.

The index computing module 10 is configured for providing an index IND of the driving style of the motor vehicle. Particularly, the index computing module 10 calculates such index IND based on a difference between the used energy E_U and reference energy E_REF and considering the traveled space.

Moreover, the data processing unit 2 comprises, for example, a measured data memory 11 (MEM) and a low-pass filtering module 12 (LPF).

The data processing unit 2 can be mounted in the vehicle or can be remote from it and placed, for example, in a monitoring station.

Particularly, the data processing unit 2, measuring unit 1 and gateway 3 can be integrated in a single apparatus 200 which, preferably, implements a control unit mounted to the motor vehicle.

The gateway 3 ensures the communication between the apparatus 200, particularly the data processing unit 2, and the one or more report modules 4. For example, if the report module 4 is a smartphone or another mobile device, the gateway 3 ensures the communication by using a short range transmission (wireless based on the Wi-Fi, Bluetooth technology, for example). Particularly, when the report module 4 is a web-console, it exchanges data/information with the apparatus 200 by using a long range transmission (based on the GPRS, UMTS, LTE technologies, for example). According to another example, if the report module 4 is a device mounted to the motor vehicle, it can be connected by wiring to the apparatus 200. The estimating system 100 can comprise more than one report module 4: at least one smartphone and/or at least one web-console and/or at least one device mounted to the motor vehicle.

In any case, the report device 4 comprises, preferably, a display adapted to show information enabling the driver or other users to know the result of the estimate of the driving style.

According to another example, when the data processing unit 2 is placed remotely from the measuring unit 1, the connection between the measuring unit 1 and data processing unit 2 can be ensured by the gateway 3, by using a low range or long range transmission technology according to the distance between the two apparatuses.

An example of an operation of the driving style estimating system 100 will be now described. A threshold value of the space S_th for estimating the driving style is defined. The index IND representative of the driving style preferably will be calculated by considering values of the consumed energy E_U and of the reference energy E_REF corresponding to a path traveled by the motor vehicle, equal to the space threshold value S_th.

The space computing module 7 detects, based on signals from the measuring apparatus 1, when the motor vehicle has traveled a space equal to the threshold value S_th. The threshold value S_th can be of 2 km, for example.

Particularly, for this evaluation, the space computing module 7 uses a first speed signal v_gps(t), provided by the GPS 6. For example, the space computing module 7 periodically integrates over time the first speed signal v_gps(t) for obtaining a current value of the space s(t).

The calculation of the current space value s(t), in the Laplace domain, can be expressed by:

S(s)=1/s V_gps(s)  (1)

Particularly, formula (1) can be calculated by the data processing unit 2 by a Tustin transformation (per se known to the person skilled in the art) on signals sampled, for example, at 10 Hz.

When the current space value s(t) is equal to the threshold value S_th, the space computing module 7 communicates such event, for example, to the index computing module 10, as an alert signal SP-AL.

The consumed energy computing module 8 performs an energy estimate E_U(t) consumed by the motor vehicle along a path of length S_th by using a speed signal v(t). For example, the speed signal v(t) is obtained by the measuring apparatus 1.

With reference to the estimated energy E_U(t), it is observed that the longitudinal force F_engine provided by the motor vehicle engine, can be expressed, for example, by:

F _engine(t)=Ma(t)+F_res  (2)

wherein:

• • M: is the motor vehicle mass;
  • a(t): is the longitudinal acceleration of the motor vehicle;
  • F_res: is the sum of the resisting forces, which are the force of the aerodynamic drag, the force of the rolling friction and the component of the gravity due to the slope of the road;
  • the term Ma(t) is the inertial force of the motor vehicle.

The power P_engine provided by the engine is given by:

P _engine(t)=Ma(t)v(t)+F_resv(t)  (3)

The first term of formula (3) is the inertial power, while the second term is the power generated by the resisting forces.

According to a preferred embodiment, it is considered only the inertial term for calculating the consumed energy E_U(t), so that the formula (3) has the following form:

P _engine(t)=Ma(t)v(t)  (4)

Indeed, the Applicant has observed that by considering only the inertial factor when calculating the driving style, uniform indexes of the driving style are obtained both in an urban environment and in the suburban one. Indeed, in an urban environment, the driving sessions are characterized by continuous brakings and accelerations, which account for the main portion of the consumed energy. By contrast, in a suburban environment, the energy contribution for overcoming the frictions, takes an importance comparable to the inertial contribution. Since the object of the index consists of evaluating the driver driving style, it makes sense considering only the component of the energy on which the driver has a real decisional power, in other words managing the speed and acceleration.

The estimated consumed energy E_U(t) is given by the integration over time of the power in the measurement range 0-t1:

$\begin{array}{cc}{E}_U\left(t\right)=\underset{0}{\overset{t1}{\int }}P_{\mathrm{engine}}\left(t\right)\mathrm{dt}& \left(5\right)\end{array}$

wherein the time instant t1 is when the motor vehicle travels a space equal to the threshold value S_th. Therefore, the value of the time instant t1 can be provided to the consumed energy computing module 8 by the space computing module 7.

The consumed energy computing module 8, based on formulas (3) and (5) or, preferably, (4) and (5), performs a numerical processing of the available digital data and estimates the inertial energy E_U consumed by the engine of the motor vehicle.

Particularly, if the formulas (3) and (5) are used for this calculation, besides the speed signal v(t) obtained by the measurement, it is also used an acceleration signal representative of the acceleration a(t) which can be provided by the inertial measurement system 5 or can be obtained by a time derivative of the speed signal v(t), in turn provided by the receiver GPS 6.

The reference energy computing module 9 estimates the reference energy E_REF(t) which represents the energy the motor vehicle engine could consume when the motor vehicle is driven according to a reference trend.

For example, such reference trend of the motor vehicle is associated to a reference trend of a cinematic magnitude. Particularly, such reference cinematic magnitude can be the motor vehicle speed. Preferably, it is selected as motor vehicle speed a filtered speed v_F(t) obtained by low-pass filtering the measured speed v(t) obtained as a function of values provided by the receiver GPS 6.

The reference energy computing module 9 uses, for example, the following formula of the reference force:

F _REF-engine =Ma _F(t)+F_REF-res  (6)

Alternatively, considering only the inertial contribution (based on considerations similar to the ones given with reference to formula (4)), is obtained:

F _REF-engine(t)Ma_F(t)  (6a)

Therefore, the reference inertial power is expressed by the following formula:

P _REF-engine(t)Ma_F(t)v_F(t)  (7)

In such formulas (6), (6a) and (7), besides the already defined parameters, there is the above cited filtered speed signal v_F(t), and the derivative thereof a_F(t) (i.e. an acceleration signal).

Therefore, the reference energy computing module 9 calculates the reference energy according to this formula:

$\begin{array}{cc}{E}_{\mathrm{REF}}\left(t\right)=\underset{0}{\overset{t1}{\int }}P_{\mathrm{REF}\text{-}\mathrm{engine}}\left(t\right)\mathrm{dt}& \left(8\right)\end{array}$

Wherein, the time instant t1, as already defined, is the one in which the motor vehicle travels a space equal to the threshold value S_th. Therefore, the value of the time instant t1 can be supplied to the reference energy computing module 9 by the space computing module 7.

The index computing module 10 calculates the index IND based on the difference between the consumed energy E_U(t1), reference energy E_REF(t1) and threshold value S_th. Particularly, the index computing module 10 calculates the difference between the consumed energy E_U(t1) and reference energy E_REF(t1) and divides this difference by the threshold value of the space S_th:

$\begin{array}{cc}\mathrm{IND}=\begin{array}{c}\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)\\ S_{\mathrm{th}}\end{array}& \left(9\right)\end{array}$

It is noted the index IND is a force, actually:

$\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{S_{\mathrm{th}}}\frac{\left[\mathrm{KW}\right]}{\left[\mathrm{km}\right]}=\frac{\left[W\right]}{m}\stackrel{0}{=}\left[N\right]$

(10)

The index IND expressed by the formula (9), therefore supplies the average “wasted” force for travelling a space S_th in the interval [0-t1]. Therefore, the higher such index IND it is, the “worst” is the driving style of a driver.

The processing unit 2 can make available this index IND to the report device 4 so that it can be shown also to the driver.

With reference to the timings for presenting to the driver or another observer of the estimate of the driving style, different standards can be adopted. For example, the values of the index of the driving style IND can be calculated every time the space S_th is traveled and at each stop of the motor vehicle, the worst value (in other words the highest) among the ones obtained, is supplied.

Referring again to the style index IND given by the formula (9), it is observed that this has the advantage of expressing in a way particularly reliable, the driving style of the driver.

As a comparison, it is considered an index IND_PA obtained by another mode for calculating the driving style, expressed by the following formula:

$\begin{array}{cc}{\mathrm{IND}}_{\mathrm{PA}}=\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{E_{\mathrm{REF}}\left(t1\right))}& \left(11\right)\end{array}$

According to the formula (11), the numerator is the difference between the inertial energies (consumed energy E_U(t1) and reference energy E_REF(t1)) and the denominator is the reference energy E_REF(t1).

For example, the cases shown in FIGS. 2A and 2B are considered. FIG. 2A shows a first curve C1 regarding the trend of the measured speed v(t) by which a motor vehicle is driven. The second curve C2 instead is the trend of the reference speed v_REF(t), obtained by low-pass filtering the measured one.

FIG. 2B shows a third curve C3 corresponding to another trend of the speed v(t) by which a motor vehicle is driven. The force curve C4 is the trend of the reference speed v_REF(t) obtained by low-pass filtering the speed of the third curve C3.

The driving style maintained by the driver in FIG. 2B seems more correct from the point of view of the wasted energies than the one of the driver in FIG. 2A.

By calculating the index IND_PA according to the formula (11) for the two exemplifying cases in FIG. 2, according to the example, the following formulas are obtained:

$\begin{array}{cc}{\mathrm{IND}}_{\mathrm{PA}}=\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{E_{\mathrm{REF}}\left(t1\right)}=\frac{60.2\mathrm{kW}}{62\mathrm{kW}}=0.1& \left(\mathrm{FIG}.2A\right)\\ {\mathrm{IND}}_{\mathrm{PA}}=\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{E_{\mathrm{REF}}\left(t1\right)}=\frac{0.2\mathrm{kW}}{2\mathrm{kW}}=0.1& \left(\mathrm{FIG}.2B\right)\end{array}$

Therefore, the index IND_PA according to the formula (11), has the same result in both cases, so that does not enable to distinguish the two behaviors.

The calculation of the index IND according to the formula (9) for the two exemplifying cases, enables to obtain:

$\begin{array}{cc}\mathrm{IND}=\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{S_{\mathrm{th}}}=\frac{60.2\mathrm{kW}}{2\mathrm{km}}=0.6& \left(\mathrm{FIG}.2A\right)\\ \mathrm{IND}=\frac{\left(E_U\left(t1\right)-E_{\mathrm{REF}}\left(t1\right)\right)}{S_{\mathrm{th}}}=\frac{0.2\mathrm{kW}}{2\mathrm{km}}=0.1& \left(\mathrm{FIG}.2B\right)\end{array}$

Therefore, the index of the driving style IND, according to the formula (9), supplies different results in the two cases, so that the driving style in FIG. 2B is better than the one shown in FIG. 2A.

According to a particular embodiment, the speed signal v(t) used for calculating the consumed energy E_U(t) and also, for example, for the reference energy E_REF(t) (by low-pass filtering) can be obtained by the frequency separation technique in order to construct a speed signal which takes account of the information contents provided both by the receiver GPS 6 and the inertial accelerometer 5. Document WO-2011-101713 describes, with reference to the associated FIG. 5, a possible frequency separation technique. This frequency separation technique can be implemented by an associated software module present in the processing unit 2.

Now it is made reference to the low-pass filtering of the speed signal v(t) obtained by the measuring apparatus 1, and performed by the filtering module 12. Such low-pass filtering can be implemented by a low-pass filter of the first digital order with signals sampled at 10 Hz.

According to a particular embodiment, the processing unit 2 comprises an index correcting module 13 (CR-MOD) configured to modify the value of the index IND calculated by the index computing module 10 based on a correction value which takes account of the average slope associated to a path traveled by the motor vehicle. As it will be understood from the following description, the index correction module 13 is particularly advantageous when the motor vehicle moves in a mountain environment.

More particularly, the index correcting module 13, during the operation, receives from the measuring apparatus 1 (particularly from the device GPS 6) a signal representative of the altitude alt(t) of the motor vehicle.

Advantageously, this altitude signal alt(t) is low-pass filtered to obtain a filtered altitude signal alt_F(t). Filtering enables to cancel the noise and can be performed by the index correcting module 13 itself, in the same way as was described with reference to the low-pass filtering module 12.

Moreover, from the filtered altitude signal alt_F(t) the index correcting module 13 calculates an “unwrapped” altitude value A_UNW indicating when the traveled path comprises altitude variations.

For example, the unwrapped altitude A_UNW can be calculated by the following formula:

$\begin{array}{cc}{A}_{\mathrm{UWR}}=\int \left|\frac{d({\mathrm{alt}}_F\left(t\right)}{\mathrm{dt}}\right|& \left(12\right)\end{array}$

Formula (12) shows the unwrapped altitude A_UNW obtained by the integration of the absolute value of the derivative of the filtered altitude alt_F(t). Using the absolute value of the derivative does not enable the ascending and descending paths (having derivatives of opposite sign) to supply contributions which cancel with each other without concurring to the calculation of the unwrapped altitude A_UNW. The integration of formula (12) is extended between two time intervals (a time window) which can be coincident with the time interval wherein the values of the estimate index IND are given.

Moreover, the index correcting module 13 places the traveled space value S_P of the vehicle between the time instants corresponding to the ones of the unwrapped altitude A_UNW calculation. For example, the traveled space S_P coincides with the space threshold value S_th. The traveled space S_P can be obtained by the space computing module 7, as described with reference to formula (1).

Therefore, the index correcting module 13 performs the calculation of an average slope P_M given by the ratio of the unwrapped altitude A_UNW to the corresponding traveled space S_P:

$\begin{array}{cc}{P}_M=\frac{A_{\mathrm{UNW}}}{S_P}& \left(13\right)\end{array}$

The average slope P_M (which can be also expressed as a percentage) is used by the index correcting module 13 for modifying the calculated value of the estimate index IND for taking account of the fact the motor vehicle is driven in an environment with altitude variations.

Therefore, based on the value obtained by the average slope P_M, the index correcting module 13 modifies the index value IND calculated by formula (9), for obtaining a corrected index IND_CR. This modification is done for reducing the value of such index as the average slope P_M increases.

For example, modifying the index IND based on the average slope P_M is made according to the following law:

IND _CR =IND·θ·P _M  (14)

wherein:

• • θ: is a tuning parameter enabling to weigh the incidence of the road slope.

With reference to the integrations of formulas (5), (8), and (12), the same considerations given with reference to formula (1) and the associated implementation by a Tustin transformation on signal sampled, for example, at 10 Hz, are still valid.

It is observed that the driving style adopted on a mountain is different from the one adopted on a flat land. Indeed, when ascending, it is more difficult to hold a uniform speed and, when descending, even though the engine brake is used, the speed variations are greater.

Correcting the driving style index, as hereinbefore described, enables to take account of the effective driving conditions and, therefore, enables to obtain a particularly reliable indication. For this reason, the Applicant observed that the index IND_PA expressed by formula (11) in a mountain environment, is not very meaningful because it often takes values similar to each other, independently from the real behavior of the driver.

As hereinbefore discussed, the results of the estimate are also available to a monitoring station wherein further calculations and statistics are made, and reports regarding the driver behavior are generated.

It is observed that the described teachings can be applied to the field of buses transporting passengers but also to other surface motor vehicles (taxis, rented cars or lorries, for example) or to see vehicles (ships or hydrofoils, for example) or to vehicles (airplanes or helicopters, for example) for transporting passengers and/or goods.

The described system for estimating the driving style is particularly advantageous because enables to obtain an index of the driving style (IND) more realistically expressing the behavior of a driver, than what is obtainable by means of the prior art systems. Moreover, obtaining the corrected index IND_CR enables to provide a reliable evaluation of the driving style also in a mountain environment.

Claims

1. A Motor vehicle driving style estimating system comprising: a measuring apparatus of a motion quantity of the motor vehicle;a processing apparatus connected to the measuring apparatus and configured to:define a value of a space corresponding to a measuring path;calculate, based on the motion quantity, an estimate of an energy consumed by the motor vehicle along the measuring path;calculate an energy reference associated to a reference behavior of the motor vehicle along the measuring path;calculate an indication of the driving style dependent on a difference between the consumed energy and the reference energy and on the space value.

2. System according to claim 1, wherein the processing apparatus comprises: a calculating module of an index of the driving style of said indication, configured to execute the ratio between said difference and the space value.

3. System according to claim 1, wherein the processing apparatus comprises: a space calculating module configured to detect, based on the motion quantity, a measuring interval during which the motor vehicle has traveled a distance equal to said space value.

4. System according to claim 3, wherein: the measuring apparatus comprises a receiver of a satellite positioning system capable of supplying a speed trend of the motor vehicle;the space calculating module is configured to detect the measuring interval based on said motor vehicle speed trend.

5. System according to claim 3, wherein the processing apparatus comprises: a consumed energy calculating module configured to estimate the motor vehicle energy consumed in said measuring interval;a reference energy calculating module configured to estimate the motor vehicle reference energy in said measuring interval.

6. System according to claim 1, wherein the processing apparatus is configured to: calculate the consumed energy based on an inertial contribution and neglecting a contribution of resistant forces;calculate the reference energy based on a relative inertial contribution and neglecting a relative contribution of the resistant forces.

7. System according to claim 5, wherein: the processing apparatus further comprises a low-pass filter configured to filter a motor vehicle speed signal supplied by the measuring apparatus and return a filtered speed signal;the reference energy calculating module is configured to estimate the reference energy based on said filtered speed signal.

8. System according to claim 1, wherein the processing apparatus further comprises: an index correcting module configured to modify said indication of the driving style based on a correction value dependent on an average slope associated to a path traveled by the motor vehicle.

9. System according to at least claim 8, wherein the index correcting module is configured to: receive an altitude signal representative of an altitude trend corresponding to a motor vehicle path;calculating an altitude variation value from said altitude signal;calculating the correction value obtained by a ratio between the altitude variation value and a value of a space traveled by the motor vehicle;modifying said driving style indication based on the correction value, and obtaining a corrected index value.

10. Method of estimating the style of driving a motor vehicle, comprising: measuring a vehicle motion quantity;defining a value of a space corresponding to a measuring path;calculating, based on the motion quantity, an estimate of an energy consumed by the motor vehicle along the measuring path;calculating a reference energy associated to a reference behavior of the motor vehicle along the measuring path;calculating an indication of the driving style dependent on a difference between the consumed energy and the reference energy and on the space value.