GB2489558A

GB2489558A - Evaluating driver behavior by classifying pairs of speed and acceleration into quality ranges

Info

Publication number: GB2489558A
Application number: GB1204193.5A
Authority: GB
Inventors: Michael Wagner; Eduardo De Bacco Cenci
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-03-30
Filing date: 2012-03-09
Publication date: 2012-10-03
Also published as: GB201204193D0; DE102011015528A1

Abstract

A method for evaluating the driving behavior of a driver, comprising the following steps: Detection of value pairs 10 of speed and acceleration of a vehicle; Classification of each value pair 10 into one of at least two quality ranges 16 to 20, with the limit acceleration 12 to 15, in which two adjacent quality ranges 16 to 20 border one another being a decreasing function of speed; Evaluation of the driving behavior on the basis of the relative frequency of value pairs 10 in the various quality ranges 16 to 20. The driverâ s behavior is evaluated to highlight areas of economical driving. The result may be displayed to the driver. The driver behavior may be monitored over a trip or over a specific period of time.

Description

A METHOD AND APPARATUS FOR EVALUATING THE DRIVING BEHAVIOR

Description I0

The present invention relates a method and apparatus for evaluating the driving behavior of a driver of a motor vehicle, especially with respect fuel con-sumption.

is Instruments for measuring and displaying the fuel consumption of a motor vehicle have long been known. They are mostly not based on the direct measurement of fuel throughput in a supply line leading to the engine, but on the measurement of a hydrostatic pressure which changes depending on consumption.

Such a change in pressure in a fresh-air intake port of the engine for example inevi- tably responds with a delay to the changing consumption and it is subject to disturb- ing influences, for the suppression of which low-pass filtering of the measured pres- sure signal is required. These two items lead to the consequence that even a real-time display of the consumption can respond only with a considerable delay to a change in consumption. Since the driver of the vehicle is unable to monitor the con-sumption meter continuously, the driver is not provided with any useful information on the quantity of fuel that is required for an acceleration maneuver and whether or not there are more rational alternatives to his or her driving style.

It is also known to record consumption values over a prolonged pen-od of time such as a complete trip for example and, on the basis of such data, to display a consumption value determined over this entire period of time. Although such an average long-term value allows the drivers to compare their own consump- tion values with the ones specified by the vehicle manufacturer, they will not be pro- vided with any information as to how they might optionally change their driving be-havior in order to reach the specified consumption values more closely.

Many drivers have the tendency to blame differences in the con- sumption values as specified by the manufacturer and those achieved by them-selves on allegedly unrealistic conditions during the tests with which the specified consumption figures are measured and accept their own higher consumption values

as inevitable.

It is the object of the invention to provide methods and means which help the driver of a motor vehicle to recognize driving situations which contribute disproportionately to fuel consumption and optimize his or her driving style by avoid-to ing such situations.

This object is achieved by a method with the following steps: a) Detection of value pairs of speed and acceleration of the vehicle; b) Classification of each value pair into one of at least two quality ranges, with the limit acceleration in which two adjacent quality ranges border one another being a decreasing function of speed; c) Evaluation of the driving behavior on the basis of the relative fre-quency of value pairs in the various quality ranges.

The method is based on the understanding that the fuel input re-quired for accelerating the vehicle increases not only with acceleration, but is the larger under given acceleration the higher the speed of the vehicle. An acceleration value which at a low vehicle speed can still be economical can lead to a dispropor-tional consumption at higher speed. When the driver is provided by the method with the information that his or her driving behavior has produced relatively many value pairs in a less economic one of the quality ranges, the driver can simultaneously also draw the conclusion that with moderate acceleration an improvement of con-sumption can be achieved.

In order to quantify the economic viability of the driving behavior, a quality factor can be assigned to each quality range and the sum total of the relative frequencies of the value pairs weighted with the quality factors can be assumed as the measure for economic viability. Within the scope of a longer series of measure-ments1 a high-resolution evaluation of the driving behavior is possible even when differentiation is merely made between two different quality ranges.

It is preferable in practice however that the number of the quality ranges is at least three in order to enable a differentiated evaluation already on the basis of a small number of pairs of values.

The result of step c) should be displayed in the vehicle so that the driver is provided with information at any time on the economic viability of his or her driving behavior and is able to optimize this behavior continuously.

It is also appropriate to determine and display a change tendency of the result of step c), so that the driver can recognize quickly and effortlessly wheth-er his or her efforts concerning an economic driving style are successful.

The relative frequency can be determined with relation to a trip or from a point in time chosen by the driver. Alternatively, the relative frequency can is also be determined in a preferably cumulative manner relating to a time interval of fixed duration which ends in the present. As a result, the driver can be provided at any time during or after an acceleration maneuver with information on its economic viability.

The limit acc&eration which separates two adjacent quality ranges from one another is preferably a linear function of the speed.

When the limit acceleration is both a decreasing and also a linear function of the speed then a speed must exist in which the limit acceleration has the value of zero. Even the maximum acceleration of the vehicle, i.e. the acceleration that can be achieved when the accelerator has been fully applied, is a decreasing function in the speed which can be approximated by a straight line. Preferably, said latter straight line and the limit acceleration have the value of zero at the same speed. In other words, the zero point of the limit acceleration lies at the maximum speed which the vehicle is capable of achieving. This maximum speed is generally not the one with the best fuel efficiency. It is clear therefrom that the method in ac-cordance with the invention shall not condition the driver in a one-sided manner to drive at the most economical speed, but rather helps the driver to move in a freely chosen speed range with the lowest possible consumption.

The object is further achieved by an apparatus for performing the method as described above, comprising a speed sensor, an acceleration sensor, a computing unit for evaluating the driving behavior on the basis of data supplied by the sensors and a display instrument for displaying the results of the evaluation.

Such a display instrument wilt generally be arranged as a scalar instrument or a digital instrument for displaying at least a relative frequency or the sum total of the weighted relative frequencies. A graphical display instrument for displaying detected pairs of values in a two-dimensional diagram can also be considered.

Subject matter of the invention is further a computer program product with a program code means which enable a computer to perform the method as described above.

Further features and advantages of the invention will be exptained below in closer detail by reference to the following description of embodiments by using the enclosed drawings. This description and the drawings will also disclose features of the embodiments which are not mentioned in the claims. Such features can also occur in combinations other than those specficatly disclosed herein. The fact that several such features are mentioned in the same sentence or in another kind of context with respect to each other therefore does not permit the conc'usion that they are only able to occur in the specifically disclosed combination. It shall principally be assumed instead that individual features of several such features can be omitted or modified insofar as this does not question the usability of the inven-tion. The drawings show as follows: Fig. 1 shows a diagram with two exemplary acceleration curves of a motor vehicle, entered as a function of its speed; Fig. 2 shows consumption curves corresponding to the ac-celeration curves of Fig. 1, also entered as a function of the speed; Fig. 3 shows a diagram of an apparatus for evaluating the driving behavior according to the present invention; Fig. 4 shows an exemplary set of pairs of acceleration/speed values of an economical driver, entered in a diagram in analogy to Fig. 1, and the classification of these value pairs into quality ranges; Fig. 5 shows a diagram of a moderately economical driver in analogy to Fig. 4; Fig. 6 shows a diagram of an uneconomical driver in analogy to Fig. 4; Fig. 7 shows a simple display instrument for displaying the evaluation of a driver.

Fig. I shows the measuring curves 1, 2 of the interrelationship be-tween acceleration and speed during acceleration of a motor vehicle, once (curve I) at maximally available engine power and once (curve 2) at a lower engine power which under the aspect of fuel efficiency is appropriate and is adjusted to a normal traffic flow. Local minima of the measuring curves 1, 2 are caused by shifting pro-cesses and the resulting interruption in propulsion.

Curves 3, 4 in Fig. 2 show the progressions of fuel consumption cor- responding to the acceleration progressions of the curves 1 and 2, also as a func- tion of speed. The similarity of the curve pairs I and 3 as well as 2 and 4 which re- spectively correspond to equal engine power is obvious. A measuring curve 5 indi-cates consumption depending on the speed at constant speed. The consumption values are considerably lower and their dependence on the vehicle speed is consid-erably lower than during accelerated driving.

An apparatus that utilizes this interrelationship between acceleration and consumption in order to evaluate the driving style of the driver or to provide the driver with objective information about his or her driving style can substantially be based on components which are present in modern motor vehicles as a standard and can therefore be realized with minimum cost expenditure. The apparatus schematically shown in Fig. 3 comprises a speedometer 6 which is present in every motor vehicle, an acceleration sensor 7 which is usually already a component of various driver support and security systems, and a processor 8 which can be pro-grammed to perform known control and driver support functions in addition to the evaluation process in accordance with the invention. A display instrument 9 con-nected with the processor 8 can be a scalar instrument or also a screen instrument.

In the latter case, it can be used for displaying an evaluation result or any other op-erating quantity of the vehicle depending on the settings made by the driver. For performing the invention it is only necessary to provide suitable programming of the processor 8. The required hardware is either provided in a conventional vehicle or can replace the existing hardware with minimal costs.

Fig. 4 shows an example of a display image which could typically be shown on a screen of the display instrument 9. The screen shows a two-dimensional diagram, the axes of which contain the speed and the acceleration of the vehicle according to the illustration of Fig. 1. Value pairs of speed and accelera- tion which are recorded in regular intervals by the speedometer 6 and the accelera-tion sensor 7 will provide one respective measuring point 10 in the diagram.

The diagram is subdivided by a plurality of descending boundary lines 11 to 15, which in this case are the straight lines 11 to 15 and which intersect the B line of the acceleration at the same speed value of approximately 190 km/h in this case. The uppermost boundary line 11 corresponds to an idealized progression of the measuring curve 1 at maximum engine power, corrected from all drops in connection with the shifting of gears. The lowest straight line 15 corresponds to a similar idealized progression of the measuring curve 2. The boundary lines 11 to 15 subdivide the area of the display screen into a plurality of triangular quality ranges 16 to 20 which taper to a point towards high speeds, and an area 21 in which no measuring points 10 can be disposed and which consequently can be used for housing a numerical display 22.

In the case of Fig. 4, nearly all measuring points 10 are situated in the lowermost quality range 20 of the diagram, which corresponds to a highly eco-nomic driving style, and a few in the next higher quality range 19. The number of the measuring points 10 in the other quality ranges 16 to 18 can be disregarded.

A numeric value which is representative for the evaluation of the driv-ing behavior and which is shown on the display 22 can be calculated according to the following formula for example: q = iO wherein n is the total number of considered value pairs and n is the respective number of value pairs in the quality range i. The weighting factor a(i) is in the sim-plest of cases equal 0 for the most economical quality range 20 and increases by I from bottom to top at each of the boundary lines 12 to 15. In order to achieve high weighting of measuring points in the uneconomical quality ranges, the increase can also rise from bottom to top, e.g. from 1 at the boundary lines 15, 14 to 2 at the boundary line 13 and 3 at the boundary line 12.

The closer inspection of the diagram of Fig. 4 shows that there are groups of measuring points 10 which seem to come to lie on an arc as in reference numeral 23 for example. Such measuring points 10 are mostly caused by meas-urements recorded in a directly successive manner, i.e. in the event of the arc 23 by a single, relatively strong acceleration maneuver for example. In order to provide the driver with short-term information on the economic viability of his or her driving style1 it is therefore advantageous to not only display the evaluation value which is displayed in the display 22 and is averaged over all data pairs recorded during a trip, but to further calculate a second average value which is based exclusively on data pairs, the age of which does not exceed a predetermined limit of a few se-conds for example. Such an evaluation value which is displayed on a further display 24 of the area 21 allows the driver to recognize, while driving the acceleration ma-neuver of arc 23, that this acceleration maneuver is less economical than his or her normal driving style and will optionally correct the same.

Fig. 5 shows measuring points 10 of a moderately economical driver in a diagram which is in analogy to Fig. 4. The density of the measuring points lOis hardly lower in the quality ranges 17 to 19 than in the quality range 16 and visibly decreases only in the uppermost quality range 20 of the diagram. It is obvious that with the formula as stated above a considerably higher numerical value is obtained than in the case of Fig. 4 which value indicates a considerably lower economical acceleration behavior.

Fig. 6 shows a data record resulting from an uneconomical driving style. The acceleration values lie on average even higher than in the case of Fig. 5 and the density of the measuring points decreases only slightly from the quality range 18 to the quality range 19. This results in a repeatedly higher evaluation val-ue.

It is obvious that an evaluation of the driving behavior on the basis of the aforementioned formula or a comparable formula would also be possible on the basis of a higher or lower number of quality ranges, and in the most extreme of cases of only two quality ranges. A larger number of quality ranges allows a consid-erably more differentiated evaluation because if the quality ranges 17 to 20 were combined into one quality range then the evaluation values in the case of Figs. 4 and 5 would differ only very little, and in the case of combining the quality ranges 16 to 19 there would also be an only slight difference between the evaluation values of Figs. 5 and 6.

In order to save space on the dashboard of the motor vehicle or keep such space available for displaying other operating parameters of the motor vehicle it is also possible to omit the display of the complete diagram as shown in Figs. 4, 5 and 6 and to merely show the display 22 and/or 24.

When the complete diagram is displayed it is possible to further im-prove the information value and thereby the possible learning effect for the driver in that the most recent respective measuring points 10 are displayed more prominently in the diagram, e.g. in that they are connected by an arc 25 as is shown by way of example in Fig. 6. In order to make the development direction of the arc 25 visible, its respectively most recent part 26 can be illustrated mast strongly and the oldest part 27 most weakly, e.g. by different brightness and/or boldness of lines. It is also possible to vary the color of the arc 25 depending on the quality range through which it passes, e.g. red in the parts extending in the most uneconomical quality range 16 and green in the parts extending in the most economical quality range 20, and to assign the interposed quality ranges 17 to 19 with shades varying from red over yellow to green. A respective graduation in colors depending on the result of the evaluation can also be assigned to the displays 22, 24, so that in the case of Fig. 4 the driver is able to recognize when he or she performs the acceleration ma- neuver corresponding to the arc 23 in a green color of the display 22 and a yellow-green color of the display 24 that on average he or she generally drives in a highly economical way but that his or her current maneuver is less economical.

in accordance with a simple embodiment, merely one display 28 as shown in Fig. 7 is provided on the dashboard. The display comprises a plurality of elements 29, 30, 31 such as LEDs which can be switched between at least one idle state and an active state. The number of elements in the active state, i.e. the acti- vated LEDs, is representative of the result of the evaluation of the driver. As a re- suIt, one to two activated LEDs can stand for an economical driving style, three ac- tivated LEDs for a moderately economical driving style and more than three activat-ed LEDs for an uneconomical driving style.

The elements or LEDs 29 can be differentiated in color in order to improve the suggestiveness of the display image. As a result, the LEDs 29 which are active during economical driving can be green, the LEDs 30 which are addition-ally activated in a moderately economical driving style will be yellow, and the LEDs 31 which are only activated under an uneconomical driving style will be red.

The display 28 can be switchable in order to selectively display as in display 22 an evaluation result based on long-term averaging or as in display 24 the resuit of a short-term averaging. A tendency display 32 in form of several LEEDs vi- gnetted in form of arrows for example can be provided alternatively or in a supple- mentary fashion, which LEDs indicate on the basis of a comparison between long- term averaging and short-term averaging or between successively obtained short-term averagings whether the driving behavior is developing within the terms of an improved or deteriorating economy. Such a tendency display can also be provided in the area 21 of the display 9, although not shown in Figs. 4 to 6.

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List of reference numerals 1 Measuring curve 2 Measuring curve 3 Measuring curve 4 Measuring curve S Measuring curve tO 6 Speedometer 7 Acceleration sensor 8 Processor 9 Display instrument Measuring point 11 Straightilne 12 Straight line 13 Straight line 14 Straight line Quality range 16 Quality range 17 Quality range 18 Quality range 19 Quality range 21 Area 22 Display 23 Arc 24 Display Arc 26 Part 27 Part 28 Display 29 Display element Display element 31 Display element 32 Tendency display

Claims

II -CLAIMS: 1. A method for evaluating the driving behavior, comprising the following steps: a) detection of value pairs (10) of speed and acceleration of a vehicle; s b) classification of each value pair (10) into one of at least two quality ranges (16 to 20), with the limit acceleration (12 to 15) in which two adjacent quality ranges (16 to 20) border one another being a decreasing function of speed; c) evaluation of the driving behavior on the basis of the relative frequency of value pairs (10) in the various quality ranges (16 to 20).
2. A method according to claim 1, characterized in that a quality factor (i) can be assigned to each quality range (16 to 20) and the sum total of the relative frequencies (n1/n) weighted with the quality factors (i) is assumed as the measure for economic viability of the driving behavior.
3. A method according to claim 1 or 2, characterized in that the result of step c) is displayed in the vehicle.
4. A method according to one of the preceding claims, characterized in that a change tendency of the result of step c) will be determined and displayed.
5. A method according to one of the preceding claims, characterized in that the relative frequency will be determined relating to one trip or from a point in time chosen by the driver.
6. A method according to one of the claims 1 to 4, characterized in that the relative frequency will be determined relating to a time interval of fixed dura-tion which ends in the presence.
7. A method according to one of the preceding claims, characterized in that the number of the quality ranges (16 to 20) is at least three.
8. A method according to one of the preceding claims, characterized in that the limit acceleration (12 to 15)is a linear function of the speed.

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9. A method according to claim 8, characterized in that a straight line (11) ap-proximating the dependence (3) of the maximum acceleration of the vehicle on the speed and the limit acceleration (12 to 15) in the same speed have the value 0.
10. An apparatus for performing the method according to one of the preceding claims, comprising a speed sensor (6), an acceleration sensor (7), a compu- ting unit (8) for evaluating the driving behavior on the basis of data (10) sup-plied by the speed sensor (6) and the acceleration sensor (7), and a display instrument (9) for displaying the result of the evaluation.
11. A computer program product with program code means which enable a computer to perform the method according to one of the claims I to 9.