SE516091C2 - Assisting method for driver of vehicle involves allowing driver to override influence of actuator when determining that applied force on one of pedals is greater than predetermined threshold value - Google Patents

Abstract

At least one actuator influences the accelerator or braking pedal (3) of the vehicle when an engine or a braking system is controlled by a control system (2) on the basis of a speed set point. The driver (4) of the vehicle is allowed to override the influence of the actuator when determining that the driver applies a force on one of the pedals that is greater than a predetermined threshold value. The accelerator performs the acceleration of the engine when being stepped by the driver. A braking operation is performed when the driver steps on the braking pedal. A speed profile for driving distance comprising the relationship between the speed set point and position is determined by considering the division of a specific driving distance into shorter segments. An Independent claim is also included for a driver assisting device.

Description

s ø 10 15 20 25 30 35 516. (191 2 when using such a speed profile be able to keep the timetable.

OBJECTS OF THE INVENTION The object of the present invention is to solve the above problems, and to provide a method for determining a speed profile, in order to promote a smoother driving style with lower emission levels and lower fuel consumption.

Another object of the invention is to further develop the above concept of an “advisor”, and to implement this concept in a vehicle.

Summary of the Invention To achieve the above objects, the invention provides a method of the above kind, which is characterized by the steps of creating a first profile by associating each segment with a highest, appropriate velocity level, smoothing discontinuities that occur between segments with different speed, calculate how long it takes to drive the mileage according to the determined profile, compare this time with a predetermined time, if said estimated time is less than said predetermined time, lower the speed levels included in the profile, until said times substantially correspond.

The method means that the speed profile is adapted, possibly through an iterative procedure, to correspond to a driving time on the relevant section that corresponds as closely as possible to the timetable. In the first stage, a speed profile is developed which in all probability would result in too short a driving time. Only then does the adaptation begin. This leads to a very rational handling of the speed profile, and good conditions for implementation in automatic systems.

According to a first embodiment of the invention, the entire velocity profile is multiplied by a scale factor, said highest, suitable velocity being reduced proportionally in all segments. By this method, the speed setpoint is reduced proportionally equally by the entire distance.

According to a second embodiment, a maximum permitted speed is introduced, and the speeds included in the profile which are higher than said introduced maximum speed are reduced to this latter speed. Through this procedure, the maximum speed setpoint of the distance is thus reduced, much like a speed limit for the vehicle is introduced.

The information used by the method is firstly related to the current mileage, which is suitably divided into segments, each of which is associated with a number of factors regarding, for example, road conditions and speed limits, as well as to the timetable and the planned stops along the distance. This information is completely independent of the vehicle, and can thus be included in a common information package that is linked to a specific mileage.

Secondly, the method continuously uses information from the vehicle's internal information system, such as speed, position and time. In modern commercial vehicles, this is already common information, and it does not involve any technical problems to retrieve it.

Brief Description of the Drawings The present invention will be described in more detail below with reference to the accompanying drawings, which, by way of example, show preferred embodiments of the invention.

Fig. 1 shows an overview of a control system for a vehicle.

Fig. 2 shows a flow chart for a part of the method according to the invention.

Fig. 3 shows a velocity profile. Fig. 4 and 5 show the velocity profile in Fig. 3, which with a method according to the invention is adjusted with regard to a timetable.

DESCRIPTION OF PREFERRED EMBODIMENTS The embodiments of the invention described below, which are to be seen by way of example only, are intended to be applied in an automatic bus which operates a route with a plurality of stops according to a specific timetable. Of course, the invention can be advantageously utilized in a variety of other situations.

Figure 1 shows an overview of a system where the method according to the invention can be applied. The engine and brake system of the bus 1 is controlled by one or more control systems 2, which are actuated by the driver's 4 instructions via accelerator and brake pedal 3. If the vehicle is of the hybrid type, the brake system includes means, such as a generator, to recover the brake energy . A device called advisor 5 is further arranged to actuate the pedals via a regulator 6.

The advisor 5 comprises a database 7 with information which will be described below, as well as means 8 for determining the speed profile. The advisor further comprises a memory unit 9. The controller 6, which consists of substantially known hardware or software, is arranged to convert signals from the advisor 5 into turns of the pedals 3.

The advisor's task is to decide how the vehicle is to be driven from the current position to the next stop, which for example consists of a stop. A flow chart of how the advisor works is shown in Fig. 2. The input data for each call is position, time and speed. The result of each call is a speed profile that describes how the vehicle is to be driven to the next planned stop. The velocity profile includes a relationship between speed setpoint and position, which can of course be converted into a relationship between speed and time with simple mathematics. The routine of Fig. 2 is called regularly during driving, since unforeseen events, such as sudden 5.16 (19-1 5 red lights or decelerations) can cause an adjustment of inappropriate speed profile.

The database 7 contains information on a division of the current mileage into a plurality of segments with a respective length of, for example, 10-100m, as well as on a maximum suitable speed along each segment. In order to determine said highest suitable speed along each segment, a number of factors are taken into account, such as, for example, speed limits, road quality, pedestrian crossings, intersections, etc.

Furthermore, the database 7 contains information on factors associated with each segment that affect acceleration, such as slope and curves. The database 7 also contains information on where on the route the planned stops, such as the stops, are located, as well as timetable information.

All this information, which is completely independent of the vehicle, can preferably be provided from a central database (not shown), and updated regularly. In this way, all vehicles that travel the same distance can have access to the same information, and a vehicle that changes lanes can be updated with new information. An update of this kind can easily be achieved with known technology, for example wireless transmission with a suitable communication protocol.

The database 7 also contains information on a number of vehicle-specific factors, such as weight, power transmission, inertia, engine power, etc. This information is thus the same regardless of the mileage that the vehicle is currently traveling. Several factors, such as engine-specific factors, are updated only in connection with, for example, service and maintenance, while other factors, such as weight, can be affected by processes while driving, such as the number of passengers. The level of detail of this latter type of information is in principle limited only by the vehicle's information system. 10 15 20 25 30 35 5-16 091 '6 The first step 10 marks the call of the routine, with the parameters time, position and speed. These parameters are taken from the vehicle's internal information system, which is suitably equipped with some form of positioning system, for example GPS. Information systems of this kind are generally known, and are becoming more common in all types of vehicles.

In the next step 11, information is retrieved from the database about suitable maximum speeds on the current mileage.

In step 12, the first speed profile is determined on the basis of this information, which is defined by the fact that the vehicle along each road segment follows the highest suitable speed. This speed profile is shown for an example of mileage in Fig. 3. Since it is not possible to momentarily change the speed of the vehicle, as marked in Fig. 3, the program control in steps 13 - 15 causes an adjustment of the first speed profile to actual acceleration conditions. .

In step 13, the previously mentioned acceleration-related factors associated with each road segment are retrieved, and in step 14, the vehicle-related factors are retrieved from the database. In step 15, it is then calculated how the speed can change between the different segments.

The algorithm in step 15 can utilize information about several segments going forward, in order to achieve a better agreement with the original velocity profile. It is conceivable, for example, that a speed reduction between two segments will be followed by a further, more powerful speed reduction. It may then be necessary to completely omit the intermediate speed level, in order to be able to brake to the lowest level in time.

In step 16, a somewhat smoothed speed profile has thus been obtained, and the travel time corresponding to this profile is calculated and compared in step 17 with the timetable read from the database 7. If the vehicle followed this first speed profile, there is a risk that the travel time would be f »M ox x L f f. .B 10 15 20 25 30 35 sm rm 7 is too short, and there is therefore a need for an algorithm according to the invention which reduces the speed in a systematic manner so that achieved. After this reduction in step 18 of one or more of the speed levels in the profile, steps 13 - 15 are repeated, and the process is repeated until a good conformity with the timetable is achieved in step 17.

The reduction of the speeds according to the invention can take place in a number of ways conceivable for the person skilled in the art, and here only two preferred methods will be presented for exemplary purposes.

A first method is to multiply the entire speed profile by one scale factor, thereby reducing the highest speed proportionally in all segments. Through the iteration of steps 13 - 15, the scale factor that gives a velocity profile that satisfactorily meets the timetable is determined. The result of a scale shift and smoothing of the velocity profile in Fig. 3 is shown in Fig. 4.

A second method involves introducing a new maximum speed limit, and adapting the speed profile to this. In each segment that has a maximum suitable speed that is higher than the introduced maximum permitted speed, the speed is reduced to the latter. Through the iteration of steps 13 - 15, the maximum permitted speed is determined which satisfactorily meets the timetable. The result of such a truncation and smoothing of the velocity profile in Fig. 3 is shown in Fig. 5.

After step 18, a speed profile has thus been determined which covers the distance from the current position to the next stop, and which keeps the vehicle as well as possible according to the timetable.

If something has happened which makes it impossible to reach the stop from the current position in the allotted time, this is immediately detected by the adviser, already at the first comparison in step 17. Examples of such incidents are queues, unusually many red lights, or u .. v 10 15 20 25 30 35 sis o91 8 other disturbances in traffic. The driver can be informed of the expected delay, and a message can also be sent to a traffic information system.

The speed profile thus determined is stored in step 19 in the memory unit 7, and each bunch of the speed profile is updated (after each call of the routine in Fig. 2), thus a new speed profile will be stored.

If the advisor is implemented in the form of software, or programmed IC circuits, the routine in Fig. 2 can be performed in an instant. It is therefore no burden for the vehicle's control system to call the routine relatively often, for example every second. In this way, the risk of sudden changes giving rise to the need for excessive changes in successive speed profiles is minimized. It can be said that the vehicle does not unnecessarily follow an incorrect speed profile.

The controller 6 continuously reads a current speed setpoint from the latest speed profile that the advisor 5 has stored in the memory unit 7, and compares this with the actual speed of the vehicle which is fed back to the controller. The engine and brake system control systems are then actuated in accordance with this difference. As for the throttle, the regulator works much like the corresponding software, in a so-called "cruise control", which regulates the throttle according to a speed specified by the driver. the different physical course.

The speed setpoint can be converted to a setpoint for pedal position and brake pressure, which then conveniently takes place in two steps. The first step generates a setpoint regarding acceleration (positive or negative) based on the speed setpoint in relation to the vehicle's current speed. A number of different possible control strategies can be implemented by the person skilled in the art. The setpoint for acceleration is then converted to the setpoint for throttle or braking action, depending on whether the acceleration setpoint - -..- v. U »10 15 20 25 30 35 516 091 9 is positive (acceleration) or negative (deceleration).

The setpoint for accelerator, which is intended to control the accelerator pedal, is expressed as a pedal position, and the setpoint for braking action, which is intended to control the brake pedal, is expressed as a brake pressure.

The controller also controls power tools, for example stepper motors (not shown), which directly affect the vehicle's accelerator and brake pedal 3 in relation to the control of the engine and brake system. It can be said that the power devices influence the pedals to reflect the influence of the engine and brake system that the controller produces. Thus, if a vehicle equipped with a device of the type described above is left without external influence, the pedals 3 move as if an optimally driving “ghost driver” was handling them.

The controller can control the vehicle's engine and brake system only by directly acting on the accelerator and brake pedals. The effect of a "ghost driver" then becomes even more noticeable.

The driver has the opportunity to override the pedals controlled by the advisor, by applying by means of the foot a pressure on one of the pedals 3 which exceeds a predetermined threshold value. The driver is allowed to override the impact of the power unit only if a force greater than a predetermined threshold value is applied to any pedal.

For example, each pedal may be provided with a resilient member 20, which forces the driver to first move the pedal against the spring action some distance before the movement affects the vehicle's control system (throttle or braking action).

In a simple example, the resilient member 20 is constituted by a helical spring or the like, which is arranged between the foot plate of the pedal and the link arm of the steering system of the vehicle. A sensor (not shown) can be arranged to sense when the foot plate has been moved a certain distance, and if necessary give a signal to disconnect the power devices, thereby releasing the pedals completely from the influence of the advisor, or at least reducing the force that the power devices applies. å »z - s ..-» v 10 15 20 51.6 o91 10 Another possibility is to arrange a piezoelectric element on each pedal, which senses which pressure the driver applies to the pedal. At sufficiently high pressure, the power tools are overridden as above.

Furthermore, a body can be arranged to give the driver an opportunity to notify the advisor of a related external influence, for example an obstacle on the road. This possibility implies a kind of “feed forward” of the regulation, and gives the adviser the opportunity to take into account the new obstacle in the next call of the routine in Fig. 2. This “feed forward” body can be made more or less sophisticated, and for example have the driver indicate a distance assessment of the obstacle.

It is to be understood that the present invention is not to be construed as limited to the above description of preferred embodiments. Several variations obvious to those skilled in the art are conceivable within the scope of the appended claims. For example, a vehicle may be equipped with other devices for controlling throttle and braking action than pedals. Furthermore, the factors mentioned for determining the velocity profile are only to be considered as examples, and several other factors may be relevant.

Claims (5)

10 15 20 25 30 516 0911 ll PATENT REQUIREMENTS A method for determining a speed profile for a mileage divided into segments, which speed profile comprises a relationship between a speed setpoint and position, characterized by the steps of creating a first profile (step 12) by associating each segments with a maximum, appropriate speed level, smooth out discontinuities that occur between segments of different speeds (step 15), calculate how long it takes to drive the distance according to the determined profile (step 16), compare this time with a predetermined time (step 17 ), and if said estimated time is less than said predetermined time, lower the velocity levels included in the profile (step 18), until said times substantially correspond. A method according to claim 1, wherein the entire velocity profile is multiplied by a scale factor, whereby said maximum, appropriate velocity is reduced proportionally in all segments. A method according to claim 1, wherein a maximum permitted speed is introduced, and the speeds included in the profile which are higher than said introduced maximum speed are reduced to this latter speed. Method according to one of the preceding claims, wherein factors that are taken into account include traffic-related factors, for example speed limits and expected queuing. A method according to any one of the preceding claims, wherein factors considered include acceleration-related factors, such as the slope and curves of the road.