WO2011025443A1

WO2011025443A1 - System and method for maintaining driving times

Info

Publication number: WO2011025443A1
Application number: PCT/SE2010/050903
Authority: WO
Inventors: Oskar Johansson; Jörgen HANSSON; Henrik Pettersson
Original assignee: Scania Cv Ab
Priority date: 2009-08-24
Filing date: 2010-08-23
Publication date: 2011-03-03
Also published as: RU2510344C2; SE0950603A1; CN102481932A; BR112012003326A2; SE534023C2; EP2470406A4; RU2012111338A; EP2470406B1; EP2470406A1; CN102481932B

Abstract

The invention refers to a system and a method for maintaining driving times with an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator. The system for maintaining driving times comprises: an input unit for indicating desired speed values v _set for the adaptive cruise control; a computing unit adapted to identify a section S_jof a driven run S during which the driving time is to be determined; to calculate the time t _cc it would have taken to drive the section S_j when using a conventional non-adaptive cruise control; to determine the time t _adapt actually taken to drive the section S _i with the adaptive cruise control; to calculate the time difference between t _cc and tadapt _,' and to calculate an adjusted control signal v _setkorr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey; v _setkorr being used as control signal to the adaptive system's cruise control regulator.

Description

Title

System and method for maintaining driving times

Field of the invention

The present invention relates to a system and a method for maintaining driving times according to the introduction to the independent claims.

Background to the invention

Many vehicles today are equipped with a cruise control to make it easier for the driver to drive the vehicle. The desired speed can then be set by the driver, e.g. via a control device in the steering wheel console, and a cruise control system in the vehicle acts thereafter upon a control system so that it accelerates and brakes the vehicle in order to maintain the desired speed. If the vehicle is equipped with an automatic gear change system, the vehicle's gears are changed so that it can maintain desired speeds.

Cruise controls which vary current set-speed (the set-point value for the cruise control's speed regulator), e.g. according to the surrounding traffic situation or the topology of the road, are becoming increasingly common. There are different reasons for wishing to vary vehicle speed. The following may be cited as examples of adaptive cruise controls:

AICC (Autonomous Intelligent Cruise Control), on the basis of measuring the distance from a vehicle in front, attempts to match the speed of the vehicle in which it is fitted to that of the vehicle in front. This means that if the driver tries to drive faster than the vehicle in front, AICC will limit the speed of his/her vehicle to maintain a constant time gap between them.

Scania Ecocruise ® varies the speed according to current vehicle speed and road gradient with a view to minimising fuel consumption for a given driving assignment. Ecocruise does not use information about the road ahead but instead makes certain assumptions about its nature based on information about the current stretch of road. By varying the vehicle's speed in hilly terrain, it is therefore possible to save fuel as compared with a conventional cruise control. If an upgrade is calculated, the system accelerates the vehicle up the hill. Towards the end of the climb, the system is

programmed to avoid acceleration until the gradient has levelled out at the top, provided that the vehicle's speed does not drop below a certain level. By lowering the speed at the end of an upgrade we can regain it on a subsequent downgrade without using the engine to accelerate. When the vehicle approaches the bottom of a dip, the system endeavours to use the kinetic energy to embark on the next upgrade at a higher speed than an ordinary cruise control. The system accelerates slightly at the end of the downgrade in order to maintain the vehicle's momentum. In undulating terrain, this means that the vehicle starts the next climb at a higher speed than normal. Avoiding unnecessary acceleration and utilising the vehicle's kinetic energy makes it possible to save fuel.

If the topology ahead is made known by the vehicle having map data and GPS, such a system can be made more robust and can also change the vehicle's speed in anticipation. An example of such a system is:

"Look-Ahead", a system that uses GPS (Global Positioning System) and a map database containing information about, for example, road gradients, bend radii, speed limits, etc. The GPS position can be used to detect the vehicle's location and direction of movement. Information about the nature of the road ahead can then be generated from the map database and be used to vary/optimise the vehicle speed so as to achieve a safe and comfortable speed at bends and minimise fuel consumption. A problem with this type of cruise control is that varying the speed of the vehicle also affects the time taken to drive a given distance as compared with an "ordinary" traditional cruise control which attempts to maintain a constant speed selected by the driver.

Cruise controls that attempt to minimise fuel consumption (Ecocruise, Look- Ahead etc., referred to below as ECC, Economic Cruise Control) have a greater influence on the average speed than an "ordinary" cruise control, assuming of course that the same set- speed is preselected. The consequences of the driving time not being the same are not usually a problem, but time differences that are too great may be a cause of irritation for the driver. If they also result in the average speed with ECC being higher than with conventional non-adaptive cruise control, the fuel saving will be cancelled out by the increased speed. This may lead to the driver drawing the incorrect conclusion that the adaptive cruise control does not deliver the promised saving.

WO 2005/062276 refers to a system for a vehicle whereby the average speed is compared with limit values indicated for desired average speed for the run concerned. The location of the vehicle is included in the comparison. However, this system is intended to help the driver maintain the recommended speed during a run on which he/she wishes to avoid having to stop because of red lights. KR 1020070066168 refers to a method for calculating the exact average speed of a vehicle from starting point to destination. The actual driving time is calculated by subtracting standstill times from the total driving time. However, there is no mention of whether the vehicle is under cruise control. The object of the present invention is to increase the acceptance of an adaptive cruise control system in a vehicle by whoever drives the vehicle.

Summary of the invention

According to an aspect of the invention, the object described above is achieved by a system for maintaining driving times with an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator. The system for maintaining driving times further comprises:

-an input unit for indicating desired speed values v_set for the adaptive cruise control; and -a computing unit adapted to

-identify a section Sj of a driven run S during which the driving time is to be determined; -calculate the time t_cc it would have taken to drive the section S₁ when using a conventional non-adaptive cruise control;

-determine the time t_adapt actually taken to drive the section S₁ with the adaptive cruise control;

-calculate the time difference between t_cc and

-calculate an adjusted control signal v_setkorr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey; v_setkOrr being used as control signal to the adaptive system's cruise control regulator.

The object of the invention is achieved according to another aspect by a method for maintaining driving times with an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator, said method comprising the steps of:

A) indicating desired speed values v_set for the adaptive cruise control;

B) identifying a section S₁ of a driven run S during which the driving time is to be determined;

C) calculating the time t_cc it would have taken to drive the section S₁ when using a conventional non-adaptive cruise control;

D) determining the time t_adapt actually taken to drive the section S₁ with the adaptive cruise control;

E) calculating the time difference between t_cc and t_adapi, and

F) calculating an adjusted control signal v_setk_Orr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey, v_setk_On being used as control signal to the adaptive system's cruise control regulator.

The problem described above is therefore solved, according to the present invention, by introducing an estimate of the driving time the vehicle would have achieved if the run had been driven with a traditional non-adaptive cruise control. This driving time is then compared with the driving time achieved with the ECC. If the driving times differ, the desired average speed for the ECC is adjusted to reduce the difference, see figure 2. The difficulty with this method is in making a correct estimate of the driving time. For a light vehicle, this is trivial, since its engine capacity will in principle be sufficient to maintain the set-speed selected by the driver, and the driving time will therefore be equal to the distance divided by the set-speed.

For heavy vehicles and/or in extremely undulating terrain, this is not the case since the engine output will be insufficient to maintain the set-speed throughout the driving assignment, see figure 1. In such cases, if the set-speed selected by the driver as the average speed for the driving assignment were used as the traditional cruise control's average speed, the result would be a large over-estimate.

In the present invention, a driven run is identified on which to carry out the time comparison. According to an embodiment, the time is then calculated for those sections where the maximum available engine output was not utilised. In those cases, the average speed for the ordinary cruise control according to an embodiment may correspond to the set-speed selected by the driver. According to another embodiment, a conventional cruise control is simulated for the identified run and the time for the run is calculated. For corresponding sections, the time with ECC is then calculated. These driving times are then used to make the driving time adjustment.

By adapting the vehicle's future speed in order to absorb the time difference, the driver will not notice that the adaptive cruise control system sometimes differs in terms of time from a conventional cruise control system. Thus his/her acceptance of the adaptive cruise control system increases and he/she will hopefully continue to use it, generating the greater fuel savings provided by an adaptive cruise control system compared with a conventional cruise control system.

Preferred embodiments are described in the dependent claims and in the detailed description. Brief description of the attached drawings

The invention is described below with reference to the attached drawings, in which:

Figure 1 depicts an example of a speed profile for a vehicle travelling over a hill under a traditional cruise control according to an embodiment of the invention.

Figure 2 depicts an example of a speed profile for a vehicle travelling over a hill under an adaptive cruise control and compensating thereafter for a time difference according to an embodiment of the invention.

Figure 3 depicts a system according to an embodiment of the invention.

Figure 4 depicts a flowchart for the method according to an embodiment of the invention.

Detailed description of preferred embodiments of the invention

Figures 1 and 2 will now be described to explain how the invention functions according to an embodiment. Figure 1 depicts an example of how a vehicle behaves when driven with a traditional cruise control. At the top of the illustration is a road profile with a hill. Below the road profile is a graph of how the vehicle's speed changes over time as it travels over the hill. Figure 2 illustrates the behaviour of a vehicle driven with an adaptive cruise control on the same road as depicted in figure 1. In the same way as in figure 1, the bottom of figure 2 shows how the vehicle's speed changes over time as it travels over the hill. On steep upgrades such as depicted, the vehicle will not always be able to maintain desired speed, since it will be in engine output deficit. This may be due to various factors, e.g. vehicle weight, engine capacity and hill gradient. This is illustrated at subsection S2 in figure 2, where the vehicle's maximum available engine output is therefore used. Figure 2 also illustrates a subsection S3 on which the vehicle's adaptive cruise control causes its speed to drop further to avoid braking on the coming downgrade. During subsections Sl, S3 and S4 the maximum available engine output is therefore not utilised. These sections are depicted in figure 1, and by calculating how much time sections Sl, S3 and S4 should have taken with a traditional cruise control and comparing it with how long they took with the adaptive cruise control, a time difference is arrived at. This time difference can thereafter be eliminated by future increase or decrease in the control value to the adaptive cruise control. In the example in figure 2, the vehicle's speed is thus increased over the distance "S_T" or the time "T" to cause the time difference to disappear. The sections S1-S4 shown here are merely examples, and it should be appreciated that the number of sections may differ from what is depicted.

Instead of eliminating those subsections where the maximum available engine output is not sufficient to maintain the vehicle speed, the whole run S may be identified by registering information about the distance travelled. Driving with a conventional non- adaptive cruise control can thus be simulated, and the time for the whole run S in figures 1 and 2 be determined. According to an embodiment illustrated in figure 3, the invention comprises a system for an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator. The system comprises an input unit for indicating desired speed values v_set for the adaptive cruise control, and a computing unit. The computing unit is adapted to identify a section S₁ of a driven run S during which the driving time is to be determined. This identification may be made in various ways, as will be explained in more detail further on in the description. The computing unit is also adapted: to calculate the time t_cc it would have taken to drive the section S₁ when using a conventional non-adaptive cruise control; to determine the time t_adapt actually taken to drive the section S₁ with the adaptive cruise control; and to calculate the time difference between t_cc and t_adapt, and calculate an adjusted control signal v_setkorr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey; v_setkOrr being used as control signal for the adaptive system's cruise control regulator. The result is a system which eliminates the time difference that may arise between a traditional non-adaptive cruise control and an adaptive cruise control, thereby increasing driver acceptance of the adaptive cruise control system.

According to an embodiment, the system comprises a computing unit adapted to identify the section S₁ by identifying the subsections Sl-Sn of the driven run S where an engine output smaller than or equal to the maximum available engine output is sufficient to maintain the vehicle speed when using the adaptive cruise control, which section S₁ consists of the identified subsections Sl-Sn. The subsections can be identified by, for example, measuring the distance travelled and at the same time detecting the engine output. The sections where the maximum available engine output is detected are eliminated. According to an embodiment, the computing unit is adapted to estimate the time t_cc by integration across the identified sections Sl-Sn. The time it should have taken to drive the vehicle with a traditional cruise control is thus reliably calculated.

According to another embodiment, the system is adapted to register information about the run S and the computing unit is adapted to identify the section S₁ by using the information about the run S. The system may for example use map data and position data to identify the driven run S, or sensors in the vehicle may continuously read road gradient, distance travelled etc. in order to provide information about the run S. In this way, the whole run S can be identified and driving with a conventional cruise control can be simulated, arriving at the total time t_cc for the run S with a conventional cruise control. The system is preferably adapted to be able to calculate continuously an adjusted control signal v_Setkorr to the cruise control regulator. New calculated time differences can thus be eliminated continuously as the journey proceeds, and the difference between the driving times with the different cruise controls can be kept to a minimum or may disappear entirely by the time the vehicle reaches its final destination.

Detected signals, calculated values etc. are usually sent via CAN in the vehicle. CAN (controller area network) is a serial bus system specially developed for use in vehicles. The CAN data bus enables digital data exchange between sensors, regulating components, actuators, control devices etc. and ensures that two or more control devices can have access to the signals from a given sensor in order to use them to control components connected to them.

According to an embodiment, the computing unit is adapted to calculate the adjusted control signal v_setkOrr so that the time difference t^ disappears over a predetermined time t_x. The driver or the system may for example set a desired time by which the time difference is to be eliminated. The computing unit then works out how much the adaptive system's reference speed has to increase to achieve this, and increases it by the required amount. We now cite an example of how the adjusted control signal v_setkorr can be calculated. The time difference tώff may be said to correspond to a distance Sjφ so S_dlff = t_ώff ^■ v_set . This means that during the time t_x the vehicle has to travel a distance equal to S_s + S_dlff instead of S₈. It is assumed that S_s = v_set - t_x , so the adjusted speed should be:

_ (S, + S_ώff ) _ (v_set ^■ t_x + t_ώff ^■ v_set ) _ t_dlff

^Vsetkorr ~ ^{" ~ "} ~ I¹ + ~~~) ^{" V} set \^l)

According to another embodiment, the computing unit is adapted to calculate the adjusted control signal v_setkon so that the time difference disappears over a predetermined distance S_x. The driver or the system can then, as described above, set a desired distance over which the time difference should be eliminated. The computing unit then works out how much the adaptive system's reference speed has to increase to achieve this, and increases it by the required amount. This may for example be done using the formula

setkorr set \ ) fdiff v_set is therefore the reference speed which the driver sets and which, during the journey, the vehicle's control system is expected to hold within a range bounded by two speeds v_mm and v_max which may be set manually by the driver or be set automatically by calculations of suitable ranges in the system. According to an embodiment of the invention, the computing unit is adapted to adjust the control signal v_setkorr within the desired speed value limits v_mn and v_max. There is thus no risk of exceeding the limits set. According to an embodiment, the computing unit is adapted to calculate an adjusted control signal v _setkorr to an ECC system in the vehicle so that said time difference disappears, which ECC system uses map data and position data concerning the itinerary. Thus the system according to the invention can also be used when an ECC system is used to regulate the vehicle's speed. The computing unit can then receive information from the ECC system in order to correctly calculate v_setkorr to the ECC system.

When an ECC system uses advance information (e.g. a "look-ahead" system), the vehicle is provided with a positioning system and map information, and position data from the positioning system and topology data from the map information are used to construct a horizon that describes the nature of the itinerary. For example, GPS (Global Positioning System) may be used to determine position data for the vehicle, but it should be appreciated that other kinds of global or regional positioning systems are also conceivable to provide the vehicle with position data, e.g. systems which use a radio receiver to determine the vehicle's location. The vehicle may also use sensors to scan the

surroundings and thereby determine its location. The horizon is divided into route segments, and by classifying coming segments, e.g. by gradient, and then regulating the vehicle's speed according to rules controlled by the classification and a number of other parameters, e.g. vehicle-specific parameters, an intelligent, comfortable and fuel-saving cruise control of the vehicle is achievable.

The invention also relates to a method for maintaining driving times for an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator. The method will now be described with reference to the flowchart in figure 3. The method comprises the steps of A) indicating desired speed values v_set for the adaptive cruise control; B) identifying a section S₁ of a driven run S during which the driving time is to be determined; C) calculating the time t_cc it would have taken to drive the section S, when using a conventional non-adaptive cruise control; D) determining the time t_adapt actually taken to drive the section S₁ with the adaptive cruise control; E) calculating the time difference between t_cc and t_adaP{, F) calculating an adjusted control signal v_setkorr to be used as control signal to the cruise control regulator, so that said time difference disappears as the vehicle continues its journey; v_setkorr being used as control signal to the adaptive system's cruise control regulator. Using the method described provides a way to increase the acceptance of an adaptive cruise control system, by eliminating any difference in driving time. As a result, the driver will presumably continue to use the adaptive cruise control, and a fuel saving resulting from use of the adaptive cruise control system can be made.

According to an embodiment, the method comprises identifying the section S₁ by identifying the subsections Sl-Sn of the driven run S where an engine output that is smaller than or equal to the maximum available engine output is sufficient to maintain the vehicle speed when using the adaptive cruise control, the section S₁ consisting of the identified subsections Sl-Sn. A section S₁ can thus be arrived at and be used to correctly calculate a time t_cc which it should have taken to drive the section S₁ with a conventional cruise control. The time t_cc is estimated according to an embodiment by integration across the identified sections Sl-Sn.

According to another embodiment, the method comprises registering information about the run S and identifying the section S₁ by using the information about the run S. For example, map data and positioning information can be used to obtain information about the run S, or else information about the run S may be registered by using sensors in order to detect road gradients, distance travelled, etc. The entire run S can then be identified and a conventional cruise control can be simulated during the run. The time t_cc actually taken to drive the vehicle for the distance S can then be calculated.

The method according to the invention is preferably repeated continuously in order to be able to calculate an adjusted control signal v_Setkorr to the cruise control regulator. In this way, new calculated time differences can be continuously eliminated as the journey proceeds, and the difference between the driving times with the different cruise controls can be kept to a minimum or may disappear entirely by the time the vehicle reaches its final destination.

According to an embodiment of the method according to the invention, the adjusted control signal v_setk_orr is calculated so that the time difference disappears over a

predetermined time. According to another embodiment, the adjusted control signal v_setkorr is calculated so that the time difference disappears over a predetermined distance. The driver or the system can set a time or a distance over which the time difference is to disappear, and after that time or distance the control signal to the adaptive system's cruise control regulator will no longer be adjusted unless a new time difference is calculated.

The control signal Vsetkorr is preferably adjusted within the desired speed value limits v_mn and v_max. As a result, the vehicle's speed will not vary beyond the limits, which might otherwise both irritate the driver and result in speed limits being exceeded.

Using an ECC system to regulate the vehicle's speed makes it possible for the nature of the coming topology to be taken into account when the speed is to be determined. The method according to the invention can then, according to an embodiment, calculate a control signal v_setkoπ to the ECC system in the vehicle so that said time difference disappears. An ECC system such as a "look-ahead" system uses in a conventional way map data and position data for the itinerary, which can be obtained in various ways. The invention relates also to a computer programme product which comprises computer programme instructions for enabling a computer system in a vehicle to perform the steps according to the method described above when the computer programme instructions are run on said computer system. According to an embodiment the computer programme instructions are stored on a medium which is readable by a computer system.

The present invention is not limited to the embodiments described above. Various alternatives, modifications and equivalents may be used. The aforesaid embodiments therefore do not limit the scope of the invention, which is defined by the attached claims.

Claims

1. A system for maintaining driving times with an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator, c h a r a c t e r i s e d in that the system for maintaining driving times comprises:

-identify a section Si of a driven run S during which the driving time is to be determined;

-calculate the time t_cc it would have taken to drive the section S₁ when using a conventional non-adaptive cruise control;

-determine the time t_ad_apt actually taken to drive the section S₁ with the adaptive cruise control;

-calculate the time difference between t_cc and t adapt,

-calculate an adjusted control signal v_setkorr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey; v_setk_On being used as control signal to the adaptive system's cruise control regulator.

2. A system according to claim 1, in which the computing unit is adapted to identify the section S₁ by identifying the subsections Sl-Sn of the driven run S where an engine output smaller than or equal to the maximum available engine output is sufficient to maintain the vehicle speed when using the adaptive cruise control, which section S₁ consists of the identified subsections Sl-Sn.

3. A system according to claim 1 , in which the system is adapted to register information about the run S and the computing unit is adapted to identify the section S₁ by using the information about the run S.

4. A system according to any one of claims 1 to 3, in which the computing unit is adapted to calculate the adjusted control signal v_setk_Orr so that the time difference disappears over a predetermined time.

5. A system according to any one of claims 1 to 3, in which the computing unit is adapted to calculate the adjusted control signal v_setkorr so that the time difference disappears over a predetermined distance.

6. A system according to any one of the foregoing claims, in which the computing unit is adapted to adjust the control signal v_setkOrr within the desired speed value limits v_mm and v_max.

7. A system according to any one of the foregoing claims, in which the computing unit is adapted to calculate an adjusted control signal v_Setkorr to an ECC

(Economic Cruise Control) system in the vehicle so that said time difference disappears, which ECC system uses map data and position data about the itinerary.

8. A system according to any one of the foregoing claims, in which the computing unit is adapted to estimate the time t_cc by integration across the identified sections Sl-Sn.

9. A method for maintaining driving times for an adaptive cruise control comprising a cruise control regulator in a motor vehicle whose control system is regulated by the cruise control regulator, c h a r a c t e r i s e d by the steps of:

A) indicating desired speed values v_set for the adaptive cruise control;

B) identifying a section S, of a driven run S during which the driving time is to be determined;

D) determining the time t _adap_t actually taken to drive the section Sj with the adaptive cruise control;

E) calculating the time difference between t_cc and t_adapt; and

F) calculating an adjusted control signal v_setkorr to be used as control signal to the cruise control regulator so that said time difference disappears as the vehicle continues its journey; v_setk_On being used as control signal to the adaptive system's cruise control regulator.

10. A system according to claim 9, in which the method comprising identifying the section S₁ by identifying the subsections Sl-Sn of the driven run S where an engine output smaller than or equal to the maximum available engine output is sufficient to maintain the vehicle speed when using the adaptive cruise control, which section S₁ consists of the identified subsections Sl-Sn.

11. A method according to claim 9, in which the method comprises registering information about the section S₁ by using the information about the run S and identifying the run S.

12. A method according to any one of claims 9 to 11, in which the adjusted control signal v_setkorr is calculated so that the time difference disappears over a

predetermined time.

13. A method according to any one of claims 9 to 11 , in which the adjusted control signal v_setkorr is calculated so that the time difference disappears over a

predetermined distance.

14. A method according to any one of claims 9 to 13, in which the control signal Vsetkorr is adjusted within the desired speed value limits v_mm and v_max.

15. A method according to any one of claims 9 to 14, in which a control signal

Vs_et_korr to an ECC (Economic Cruise Control) system in the vehicle is calculated so that said time difference disappears, which ECC system uses map data and position data about the itinerary.

16. A method according to any one of claims 9 to 15, in which the time t_cc is estimated by integration across the identified sections Sl-Sn.

17. A computer programme product comprising computer programme instructions for enabling a computer system in a vehicle to perform the steps according to the method according to any one of claims 9 to 16 when the computer programme instructions are run on said computer system.

18. A computer programme product according to claim 17, in which the computer programme instructions are stored on a medium which is readable by a computer system.