WO2009022968A1

WO2009022968A1 - Cruise control system and method for a vehicle

Info

Publication number: WO2009022968A1
Application number: PCT/SE2008/050819
Authority: WO
Inventors: Magnus GRANSTRÖM
Original assignee: Scania Cv Ab (Publ)
Priority date: 2007-08-16
Filing date: 2008-07-02
Publication date: 2009-02-19
Also published as: BRPI0813864B1; SE531431C2; BRPI0813864A2; SE0701889L; DE112008002174T5

Abstract

The present invention relates to a cruise control system for a vehicle, said vehicle comprising accelerator means wherein a power take-off is controlled by the vehicle driver by manoeuvring said accelerator means, said accelerator means being movable in a movement region between a first position and a second position, wherein said movement region is separated into a first movement region and a second movement region, wherein the second movement region is arranged to control power take-off of the vehicle, and wherein said power take-off is arranged to be dependent on the position of the accelerator means in said second movement region. The system includes means for providing a braking action when said accelerator means is in said first movement region, and the cruise control is activated when said accelerator means is in a third movement region between said first region and said second region.

Description

Cruise control system and method for a vehicle

Field of the invention

The present invention relates to a cruise control system for a vehicle, and in particular to a cruise control system according to the preamble of claim 1.

Background of the invention

Modern vehicles, especially heavy vehicles such as lorries and busses, are often provided with a plurality of driver aiding systems, such as, for example, one or more cruise control systems.

The driver often uses cruise control systems in order to avoid lengthy stationary stress. When driving on, for example, motorways, the geography can be such that, e.g., the accelerator pedal is, by means of the driver's foot, kept in substantially the same position for a considerable time. The use of a cruise control system can reduce such static stress to a large extent.

Cruise control systems can, e.g., consist of Autonomous intelligent Cruise Control (AICC) systems, which include means for measuring distance and/or speed of vehicles or obstacles in front of the vehicle. An AICC system can, for example, use radar or laser technology to estimate the speed of a vehicle in front, and, based on the estimated speed, control the speed of a system vehicle such that the system vehicle follows the vehicle in front with a predetermined distance there between.

Another example of a cruise control system is a system which, when activated, maintains a set speed irrespective of whether the vehicle is travelling uphill, downhill or on level ground. Such systems can also, where appropriate, such as in vehicles having an automatic transmission, control gear changing to increase the ability to maintain a set speed. Most cruise control systems of the above kinds have in common that the controlled speed and/or distance generally is activated and deactivated by the driver, e.g., by operating a control means such as a conventional push-button located on or in the vicinity of the steering wheel. This can, for example, be accomplished by accelerating the vehicle to the desired speed and/or distance to a vehicle in front by means of the accelerator pedal, and, when the desired speed and/or distance has been reached, manoeuvre said button to activate the cruise control.

If, for some reason, there is a desire to temporarily override the cruise control, e.g., in order to overtake a slower vehicle, the set speed/distance generally can be overridden by depressing the accelerator pedal in a conventional manner. When the driver subsequently releases the accelerator, e.g., when said slower vehicle has been overtaken, the vehicle resumes its previously set speed (or distance to another vehicle in front) .

Further, the speed/distance control according to the above is usually deactivated when the driver by manoeuvres (depresses) the brake pedal, and after such disengagement, the activation procedure has to be performed once again.

For this reason, systems of the above kind are generally most useful when used on motorways, or roads with light traffic where little or no braking is required and wherein periods of activated cruise control often are lengthy. If the traffic load is heavy, as often is the case in urban environments, the traffic rhythm is often of such kind that braking and accelerating operations are alternately and frequently required, and in such situations, use of a cruise control system is not equally comfortable to the driver, since the cruise control constantly would have to be deactivated, e.g., when stopping at traffic lights or turning corners, with following frequent re-activations, which often results in the cruise control not being used at all in such environments.

This is particularly true for constant-speed cruise control systems, but is also valid for constant-distance cruise control systems.

Consequently there exists a need for an improved cruise control system for use in more varying traffic conditions, such as when traffic load is heavy. An example of a cruise control system of such kind is described in US 6,675,923 Bl. The described system comprises means for separating a movement region of an accelerator pedal into a first region and a second region, wherein depression of the pedal in the first region engages the automotive cruise control system, and wherein the depression resistance experienced by the driver is smaller in the first movement region as compared to the second movement region. If, when the cruise control has been activated, further acceleration is required, this can be accomplished by pushing the accelerator pedal into said second movement region, wherein the position of said accelerator pedal in said second movement region determines the acceleration.

Although the system described in US, 6, 675, 923 Bl provides a system that is more suitable for use in situations with heavier traffic, since activation and deactivation of the cruise control in a simple manner can be controlled by the accelerator pedal and brake pedal, respectively, there still exists a need for a cruise control system that is even more suitable for varying traffic conditions, and especially for use in situations such as when traffic load is heavy and/or when travelling at low speeds.

Summary of the invention It is an object of the present invention to provide a method that solves the above mentioned problem. This object is achieved by a system according to the characterising portion of claim 1. According to the present invention, a cruise control system for a vehicle is provided. The said vehicle comprises driver controllable accelerator means for requesting a power takeoff, said power take-off being controlled by the vehicle driver by manoeuvring said accelerator means, said accelerator means being movable in a movement region between a first position and a second position, wherein said movement region is separated into a first movement region and a second movement region, wherein the second movement region is arranged to control power take-off of the vehicle, and wherein said power take-off is arranged to be dependent on the position of the accelerator means in said second movement region. The said system further includes means for providing a braking action when said accelerator means is in said first movement region, and said cruise control is arranged to be activated when said accelerator means is in a third movement region, said third movement region being a movement region between said first region and said second region.

This has the advantage that a cruise control that is suitable for various kinds of traffic, and in particular in environments with heavier traffic, such as urban environments, in which starts and stops often are frequent, is obtained. No other manoeuvring than operating the accelerator pedal is required and this simplicity in activating/deactivating the cruise control makes it possible to set the cruise control also for only short distances while the use of the cruise control still is being comfortable to the driver. Further characteristics of the present invention, and advantages thereof, will be evident from the following detailed description of preferred embodiments and appended drawings, which are given by way of example only, and are not to be construed as limiting in any way.

Brief description of the drawings

Fig. 1 shows an exemplary vehicle with which the present invention can be utilised.

Fig. 2 discloses the movement region of an accelerator pedal. Fig. 3 discloses an exemplary embodiment of the present invention .

Fig. 4 discloses an example of an acceleration procedure according to the invention.

Detailed description of exemplary embodiments Fig. 1 discloses an example of a vehicle 100 with which the present invention advantageously may be utilised, and which, for example, can constitute a heavy vehicle such as a truck.

The vehicle 100 is powered by a motor, which in this exemplary embodiment consists of an internal combustion engine 101, such as a diesel engine. The engine is, by means of suitable transmission (not shown) connected to the vehicle's driving wheels in a conventional manner.

Fig. 1 also discloses part of a vehicle control system. Vehicle control systems in modern vehicles usually consist of a communication bus system consisting of one or more communications buses 110 to interconnect electronic control units (ECUs) and various components located on the vehicle. Examples of such control units include Gearbox Management System (GMS) 111, which controls the gearbox functions of the vehicle, Engine Management System (EMS) 112, which controls the engine functions of the vehicle, and Brake Management System (BMS) 113, controlling the brake functions of the vehicle. A Driver Assistance System (DAS) control unit 114 is also disclosed, which controls, e.g., cruise control system functions of the vehicle. The shown positions of the control units are only exemplary, and not representative. For example, the disclosed control units can all be arranged in the front portion of the vehicle.

As was mentioned, the DAS 114 controls the automatic cruise control functions of the vehicle. The DAS 114 sends control signals to the EMS 112 and the BMS 113, and, where appropriate, GMS 111, in order to control engine/brake/gearbox functions according to current cruise control settings.

Cruise control functions controlled by DAS 114 can, for example, consist of constant speed cruise control, wherein a set-speed obtained from the vehicle driver is used for calculating appropriate control signals for transmission to, e.g., EMS 112, BMS 113. The cruise control functions can also include more advance functions, and one such function is the ability to maintain a constant distance to a vehicle in front. In order to achieve this, the vehicle 100 comprises means for determining the location and distance to other vehicles or obstacles surrounding the vehicle 100. These means are arranged in the front of the vehicle and can, for example, consist of a radar, laser radar, photographic camera or any other suitable sensor type. In the disclosed exemplary embodiment, the sensor consists of a laser radar such as a LIDAR (Light Detection And Ranging) 120, the function of which being known to persons skilled in the art and, in principle, functioning much the same way as a conventional radar. The

LIDAR 120 transmits light towards a target, such as a vehicle in front, and the transmitted light interacts with, and is altered by, the target. A part of the transmitted light will be re-reflected to the LIDAR 120, where the re-reflected light or a representation of the re-reflected light is received.

The vehicle also comprises accelerator means, such as an accelerator pedal 130, by means of which the vehicle driver can apply a desired motor torque to accelerate the vehicle and/or maintain a current speed. Further, the vehicle comprises cruise control manoeuvring means, such as push buttons 131, by means of which the driver can activate the cruise control when a desired speed (or distance to a vehicle ahead) has been reached. The cruise control manoeuvring means can further comprise means (such as, e.g., + and - buttons among said push buttons 131) for adjusting the set speed/distance while the cruise control is active. The cruise control can often be deactivated either completely by a push button or completely or at least partially by applying the brakes of the vehicle.

As was stated above, a constant speed cruise control, or constant distance cruise control for that matter, can have a satisfactory function in many situations, such on highways or motorways with light traffic. However, when travelling in urban areas having, for example, low speed limits and/or frequent traffic lights, or on highways or motorways wherein cut-ins, i.e., vehicles in neighbour lanes performing a lane change right in front of the system vehicle, are frequent, the cruise control system is often too inconvenient to use due to frequent use of the brake pedal, which thereby deactivates the set cruise control.

According to the invention, however, these drawbacks of current cruise control systems are at least alleviated by a system wherein the accelerator means, such as the accelerator pedal, is used in a manner that now will be described with reference to figs. 2 and 3.

As is shown in fig. 2, the accelerator pedal is movable in a movement region between a first end position A, which is a spring back position to which the accelerator pedal returns when relieved from a force applied by a driver's foot, and in which no power take-off is requested by the driver, and a second end position B, which is the position wherein a maximum power take-off from the engine is requested. With regard to a conventional accelerator pedal, the requested power take-off is increasingly dependent on the change on position from A towards B.

According to the present invention, however, the movement region from A to B is used in a completely different manner. This is disclosed in the graph of fig. 3, in which the movement s from A to B is given on the x axis as angular change from α_A to α_B. As can be seen in the figure, the movement region from α_A to α_B is divided into three subregions, I, III, and II. Region III, i.e. the middle region, is a "cruise control" region, that is, when the accelerator pedal is kept in this region, the cruise control is activated with the current speed (or, if applied, current distance to the vehicle ahead) when entering the region as a set value for the cruise control. Consequently, the cruise control can be activated in a simple manner using only the accelerator pedal. In region III, the system is preferably arranged such that vehicle engine power take-off and/or braking action is controlled so as to maintain a set speed or distance, i.e., if the driving resistance (i.e., the resultant of the head wind, the rolling resistance and the gravity that accelerates/decelerates the vehicle) increases, an increase in power take-off is requested to meet the increase in driving resistance .

Further, if additional power take off from the vehicle engine is required by the driver, and the cruise control consequently must be overridden, the additional power take-off can be requested by depressing the pedal beyond region III and into the acceleration region II.

The acceleration region is preferably arranged such that when entering the region II, i.e., at the boundary between region III and region II, this position of the accelerator pedal will precisely, or at least substantially, correspond to the current power take-off from the engine. That is, the power take-off at this position will vary depending on the set speed, and, consequently, there is no physical coupling between accelerator position and power take-off from the engine. Instead, the power take-off is electronically controlled such that the power take-off request in region II will always correspond to 0 to 100 % of the remaining power take-off that the engine is capable of delivering. For example, if the current power take-off requested by the cruise control is, e.g., 25% of the power that the engine is capable of delivering, this take-off is set as "zero" level for region III, and this is also what is indicated by the y axis in fig. 3. This arrangement has the advantage that a smooth acceleration from the set speed can be obtained without undesired snatches and shocks within the power train. The position of said accelerator pedal is preferably arranged to be measured by a sensor, whereby the sensor signals then can be used to determine the position of said accelerator means. This has the advantage that the different movement regions of the accelerator pedal according to the invention in a simple manner can be determined by different ranges of the sensor signal .

Further, the minimum power take-off in said second movement region, i.e., at the boundary to region III, should preferably be controlled such that it at all times substantially corresponds to the current power take-off, i.e., the power take-off that is required to maintain the current speed.

The reason for this will be exemplified with reference to fig. 4. In fig. 4 an exemplary torque characteristic 400 of a vehicle engine is disclosed. If the vehicle is currently driving at a point A in the figure with the accelerator in region III, and the driver decides to request 50% of the remaining torque, i.e. point B in the figure, by entering the accelerator pedal into region II, the operating point will eventually move to point C, i.e. to the point where the driving resistance corresponds to the requested torque. This, however, has the disadvantage that if, at point C, the driver decides to return to region III, a release of the accelerator pedal will subject the vehicle to a braking action, since the requested torque during the release of the accelerator pedal is lower than required for as long as the pedal till is in region II.

If, on the other hand, the power take-off in region II is regularly adjusted so that the torque take-off at the boundary to region III corresponds to the current power take-off, the same action as described above will, instead, result in a transition to point D, i.e., the requested power take-off is at all times 50% of the remaining torque during the acceleration, with the result that when releasing the accelerator pedal, no braking action will occur since the minimum torque take-off in region II will never go below the required to maintain the current speed at the current driving resistance .

However, in an alternative embodiment, the region II could be arranged such that it always corresponds to the same power take-off. For example the accelerator pedal can be, or act as being, physically coupled to fuel injection devices of the engine. In another alternative embodiment, the region II can be arranged such that it always provides zero to 100 % of the power that the engine is capable of delivering. These latter embodiments, however, has the disadvantage that depression of the accelerator pedal from region III into region II can, apart from undesired deceleration, give rise to undesired snatches and shocks within the power train.

Back to fig. 3, if the accelerator pedal is released such that it by spring-back force enters into region I, the cruise control, or at least the speed/distance control is deactivated and a braking action is applied. In a first exemplary embodiment, this braking action corresponds to motor braking, i.e., releasing the accelerator pedal will have a similar effect as when releasing the accelerator pedal when driving in a conventional manner with no cruise control activated. This is indicated in the figure by the torque going negative in region I (it is to be understood that the indicated levels are not intended to be representative, since the negative torque with respect to motor-brake can be in the order of 100-200 Nm, while the positive torque that the engine can deliver, with regard to a truck, can be in the order of 3000 Nm) . The maximum motor-brake can, as is shown in the figure, be arranged to be obtained already at a point s_m at which the accelerator pedal is not fully released, and/or be arranged such that it is obtained precisely when the accelerator pedal is fully released. Consequently, the invention has the advantage that it provides a cruise control that can be used in various kinds of traffic, and with no other manoeuvring than operating the accelerator pedal in substantially a conventional manner as described above. Further, due to the simple activation and deactivation, a driver can choose to set the cruise control for only a short distance since the cruise control is immediately deactivated when releasing the accelerator pedal.

In one embodiment of the present invention, the accelerator is arranged to always function according to the above. In another embodiment, however, the cruise control system can be arranged such that it can be put into operation, i.e. the described behaviour of the accelerator pedal can be activated, e.g., by operating an on/off switch on the dashboard/steering wheel. When the on/off switch is in the off position, the accelerator pedal has its "normal" function, that is, controlling the engine torque throughout its travel (movement region) . This solution has the advantage that the driver can choose freely whether to operate the accelerator pedal in a fully conventional manner, with no cruise control, or a conventional cruise control, or with the accelerator pedal working according to the present invention.

The invention further has the advantage that as soon as the driver releases the accelerator pedal either by removing the foot, or releasing the applied force to the extent that it enters into region I, the cruise control is immediately deactivated and a braking action is started, with the result that a braking distance in a crisis situation can be somewhat shortened compared to conventional cruise control systems. In one embodiment of the invention, the pull-back force of the accelerator pedal is no different from conventional accelerator pedals, in which case, e.g., an indicator such as a lamp can be used to indicate for the driver that the accelerator pedal is in region III and the cruise control thereby is activated.

As can be seen in fig. 3, the various portions of the total movement region of the accelerator pedal for the respective regions I, III and II can vary. For example, region II can be apportioned a larger part of the total movement region, while the cruise control regions I and III can be made smaller. The disclosed proportions, however, are therefore only exemplary, and any suitable proportion can be used. For example, region I can be in the order of 20-50% of the total movement region of the accelerator pedal, but also larger or smaller.

Further, in one embodiment of the invention, the pull-back force that is associated with movement region I can be arranged such that it is smaller than the pull-back force associated with the movement region II. This change in pull- back force should preferably be effectuated in region III. This has the advantage that the driver in a simple manner using his foot can detect when the cruise control is activated. This also has the advantage that the driver can rest his foot, by applying a force greater than the pull-back force of region I, but still lower than the pull-back force of region II since during periods of automatic driving, the change in pull-back force will function as an intermediate stop of the accelerator pedal at which the driver's foot can rest .

As stated above, region II enables acceleration beyond the set speed (distance) of the cruise control system, and by using different pull back forces, it is easy for the driver to know when the accelerator pedal enters into region II, e.g., to accelerate the vehicle to a higher speed, and then return to region III to set the new speed. Similarly, the driver can release the accelerator pedal into region I on order to slow down the vehicle, whereafter the slower speed can be set by returning to region III. The pull-back force is preferably appreciably greater in region II to enable for the driver to sense the change in a simple manner.

Instead of using an extended region (III) wherein the cruise control is activated as above, this region can be arranged to only comprise the position of the boundary between the lower and the greater pull-back forces of the accelerator pedal. Alternatively, the region III can be made to consist of a small portion of the movement regions of either sides of the force transition point. This has the advantage that proper operation can be ensured in a simple manner and that some movement of the driver' s foot is possible without unintentionally deactivating the cruise control.

So far, only motor-brake is applied when the accelerator pedal is in region I. It is, however, also possible to apply a further brake force, e.g., exhaust, brake in this region to obtain a greater braking action without releasing the accelerator pedal. This has the advantage that a more noticeable braking action can be obtained, in particular for diesel engines where the normal motor-brake power is considerably smaller as compared to a petrol engine of corresponding power. Further, said accelerator pedal is preferably arranged such that it returns to said first position when no force is exerted on the accelerator pedal by the vehicle driver.

Further, in the above description, the relation between power take-off and pedal position has been disclosed as substantially linear. Naturally, this relation can be of any suitable kind, such as, e.g., exponential or logarithmic. In fig. 4 the control unit 114 is shown more in detail. The control unit 114 comprises means 401 for receiving various signals from, e.g., the LIDAR 120 and/or other control units. These signals can be received, e.g., via messages transmitted on the CAN bus 110 or by direct links from, e.g., LIDAR 120 to control unit 114. The received signals, together with other information, such as data transmitted from other control units, can then be used in a data processing unit 402. The data processing unit 402 can, using the received sensor signals and data, and by means of a computer program, which, e.g., can be stored in a computer program product in form of storage means 403 in, or connected to the processing unit 402, perform cruise control calculations for controlling engine, braking system and, where appropriate, gearbox operation, and generate control signals for transmission, by means of output means 404, to, e.g., engine control unit and brake management system so as to obtain operation according to the above. The storage means can, for example, consist of one or more from the group: ROM (Read-Only Memory), PROM (Programmable Read- Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), hard disk drive.

In the above description, the movement of the accelerator means has been described as a rotary motion. It is, of course, also possible to use accelerator means having a linear motion. Further, the rotation has been described as having an arc length consisting of only a portion of a circumference of a circle. The movement can consist of a considerably larger portion of the circumference of a circle, e.g. if the present invention is used for a motorcycle throttle.

Claims

1. Cruise control system for a vehicle, said vehicle comprising driver controllable accelerator means for requesting a power take-off, said power take-off being controlled by the vehicle driver by manoeuvring said accelerator means, said accelerator means being movable in a movement region between a first position and a second position, wherein said movement region is separated into a first movement region and a second movement region, wherein the second movement region is arranged to control power takeoff of the vehicle, and wherein said power take-off is arranged to be dependent on the position of the accelerator means in said second movement region, characterised in

- that said system includes means for providing a braking action when said accelerator means is in said first movement region, and

- that said cruise control is arranged to be activated when said accelerator means is in a third movement region, said third movement region being a movement region between said first region and said second region.

2. System according to claim 1, characterised in that said third movement region connect said first movement region and said second movement region.

3. System according to claim 1 or 2, characterised in that movement of said accelerator means into said first and/or second movement region from said third movement region is arranged to deactivate said cruise control.

4. System according to any of the claims 1-3, characterised in that said transition region consists of a distinct position, said distinct position separating said first movement region from said second movement region.

5. System according to any of the claims 1-4, characterised in that said first position is a first end position of said movement region, and that second position is a second end position of said movement region.

6. System according to any of the preceding claims, characterised in that said accelerator means is an accelerator pedal, arranged to be operated by a foot of a driver.

7. System according to claim 6, characterised in that the pull-back force when depressing said accelerator pedal is lower in said first movement region than in said second movement region.

8. System according to claim 1, characterised in that said the position of said accelerator means is arranged to be measured by a sensor, wherein the sensor signals are used to determine the position of said accelerator means.

9. System according to claim 1, characterised in that the power take-off at the boundary of said second movement region towards said third movement region is controlled such that this position of the accelerator means substantially correspond to the current power take-off from the engine when entering said second movement region from said third movement region .

10. System according to any of the preceding claims, characterised in that in said second movement region, the power take-off is arranged to increase toward said second position .

11. System according to any of the preceding claims, characterised in that in said first movement region, the braking action is arranged to increase towards said first position from the boundary of said first movement region towards said third movement region.

12. System according to any of the claims 1-11, characterised in that the portion said first movement region encompasses of the said total movement region is arranged to be 5-60% of the total movement region from said first position to said second position.

13. System according to any of the claims 1-12, characterised in that it further comprises pull-back means for ensuring return to said first position when no force is exerted on said accelerator means by said vehicle driver.

14. System according to any of the claims 1-13, characterised in that, when said accelerator means is in said third movement region, said system is arranged to control said power take-off and/or braking action so as to maintain a set speed or distance .

15. System according to any of the claims 1-14, characterised in that, in operation, the minimum power take-off in said second movement region is controlled such that it substantially corresponds to the current power take-off.

16. Cruise control method for a vehicle, said vehicle comprising driver controllable accelerator means for requesting a power take-off, said power take-off being controlled by the vehicle driver by manoeuvring said accelerator means, said accelerator means being movable in a movement region between a first position and a second position, wherein said movement region is separated into a first movement region and a second movement region, wherein the second movement region controls power take-off of the vehicle, and wherein said power take-off is dependent on the position of the accelerator means in said second movement region, characterised in that the method comprises the steps of: - providing a braking action when said accelerator means is in said first movement region, and

- activating said cruise control when said accelerator means is in a third movement region, said third movement region being a movement region between said first region and said second region.

17. Computer program product, characterised in code means, which when run on a control unit in a vehicle and connected to an internal communication system in said vehicle causes the control unit to execute the method according claims 16.

18. Computer program product including a computer readable medium according to claim 17, wherein the code means are included in the computer readable medium.

19. Vehicle, characterised in that it includes a system according to any of the claims 1-15.