WO2013139625A1

WO2013139625A1 - Method and device for controlling the speed of a motor vehicle

Info

Publication number: WO2013139625A1
Application number: PCT/EP2013/054733
Authority: WO
Inventors: Jens Gröger; Kay Hohenböken; Jan Linsel
Original assignee: Ford Global Technologies, Llc; Ford-Werke Gmbh
Priority date: 2012-03-22
Filing date: 2013-03-08
Publication date: 2013-09-26
Also published as: DE102012204596A1

Abstract

In a method for controlling the speed of a motor vehicle, a current fuel consumption FC_act of the motor vehicle is determined and the speed of the motor vehicle is controlled by intervention in an engine control in order to adhere to a predeterminable fuel consumption target value FC_soll, wherein a minimum speed v_min that is maintained as a minimum can be predetermined. The invention further relates to a device for controlling the speed of a motor vehicle.

Description

Method and device for controlling the speed of a

Motor vehicle description

The invention relates to a method and a device for regulating the speed of a motor vehicle. To increase the comfort and relieve the driver, motor vehicles are nowadays often equipped with speed controls. In this case, a respective current speed of the motor vehicle is determined and intervened upon detection of a deviation from a predefinable setpoint speed in the engine control to minimize the deviation. Such speed controls are usually designed to keep the speed of the motor vehicle as constant as possible at the desired speed, regardless of external conditions, such as inclines, inclines, wind conditions or the nature of the road surface. However, this often results in increased fuel consumption.

In order to control an engine of a vehicle so that it consumes as little energy as possible, DE 10 2010 018 335 A1 proposes a cruise control system whose control is designed so that it keeps the speed of the vehicle at an adjustable setpoint speed, provided the noise - Output of the vehicle engine does not exceed an adjustable maximum target power, and that it reduces the speed of the vehicle, if necessary, so far that the maximum target power is not exceeded. As a result, however, a reduction in fuel consumption is achieved only to a limited extent. For motor vehicles with hybrid drive, a speed control device is described in EP 2 010 423 B1, in which the controller is configured to set a nominal acceleration of the vehicle within a value range of permissible setpoint values. to calculate accelerations, wherein the upper limit for the acceleration is set so that the required drive power can be provided by the electric drive. As a result, it can be achieved in a hybrid motor vehicle that the internal combustion engine does not need to leave its optimum operating point. This method is not applicable to motor vehicles without hybrid drive.

According to EP 1 888 900 B1, an actual value of the fuel consumption of a motor-driven motor vehicle is detected, a value of the fuel consumption given to a fuel consumption regulator as the desired value and the actual value of the fuel consumption used to control the setting of the engine power. In one mode, the fuel consumption value is an upper limit, and a set speed is maintained if the predetermined fuel consumption value is not exceeded. However, it has been shown that such a regulation with a fuel consumption value as desired value in certain situations can lead to undesired reactions of the motor vehicle, which complicate the operability of the motor vehicle.

It is therefore an object of the present invention to provide a method and a device for regulating the speed of a motor vehicle, wherein the above-mentioned disadvantages are avoided. In particular, it is an object of the present invention to provide a method and an apparatus of the type mentioned, wherein both a reduction in fuel consumption and pollutant emissions and an increase in ease of use or traffic safety are made possible.

This object is achieved by a method and by a device as specified in the independent claims. The inventive method for controlling the speed of a motor vehicle relates in particular to motor vehicles with a drive motor which is designed as an internal combustion engine, for example as a gasoline or diesel engine. In each case a current fuel consumption of the motor vehicle is determined. Methods for determining the fuel consumption, for example from the signal of a flow and / or a pressure sensor or from a characteristic map of the engine are known per se. By the term "fuel consumption" is meant here and below a distance-related fuel consumption, for example given in liters per 100 km, which can be determined for example from a time-related fuel consumption by taking into account the detectable via a speed sensor current speed of the motor vehicle.

By engaging in an engine control of the motor vehicle, the speed of the motor vehicle is regulated in accordance with the invention in such a way that a predefinable fuel consumption target value is maintained as far as possible. For this purpose, the deviation of the current fuel consumption from the fuel consumption target value can be determined and the speed of the motor vehicle can be adjusted to minimize the deviation. Since, as a rule, at least above a lower limit speed, the fuel consumption increases with increasing speed, in particular when the fuel consumption target value is exceeded, a reduction of the speed and an undershooting of the fuel consumption desired value causes an increase in the speed. For this purpose, an intervention in the engine control, which corresponds to a reduced or increased operating angle of the accelerator pedal.

According to the invention, a minimum speed of the motor vehicle can be predetermined, which is at least maintained. Thus, to maintain the minimum speed, if necessary, a higher actual fuel consumption than the fuel consumption target value is allowed.

As a result of the fact that a minimum speed can be predetermined which is at least held independent of the fuel consumption, a drop in the speed of the motor vehicle below the minimum speed can be avoided, even in situations which increase the consumption considerably, for example on a steep slope or in the case of strong head wind. This will improve both the quality of serviceability of the motor vehicle as well as an increase in traffic safety possible. In particular, this can avoid an unexpected behavior of the motor vehicle, which differs substantially from the behavior that would be chosen by a driver of the motor vehicle due to the situation. In this way, a low fuel consumption with high ride comfort can be achieved.

According to a preferred embodiment of the invention, a consumption-independent regulation of the speed of the motor vehicle to the predetermined minimum speed in the event that the current fuel consumption of the motor vehicle exceeds the fuel consumption setpoint even when the speed drops to the minimum speed. In particular, in cases where, for example, due to an increase in fuel consumption increases and the speed of the motor vehicle is therefore reduced to maintain the fuel consumption target value, then engages when the minimum speed is reached, a speed control on the minimum speed. Such a speed control, in which the deviation is detected by the minimum speed set in this case as a set speed and is minimized by intervention in the engine control, is known per se. In this way, a particularly comfortable behavior of the motor vehicle can be achieved and at the same time avoided that the minimum speed is exceeded. Depending on the design of the speed control, it may also be permissible that the minimum speed is undershot by one control deviation. As soon as the current fuel consumption falls below the fuel consumption setpoint in the regulation to the minimum speed, the consumption-independent control is terminated to the minimum speed, and the speed of the motor vehicle is increased to maintain the fuel consumption setpoint. According to a preferred embodiment of the invention, not only a minimum speed, but also a maximum speed can be predetermined, which is kept at most independent of the current fuel consumption. hereby a further improvement of the operability and traffic safety of the motor vehicle is made possible.

In particular, it is advantageously provided that when the current fuel consumption at the maximum speed falls below the fuel consumption target value, the speed is regulated to the maximum speed. Thus, if the current fuel consumption of the motor vehicle is particularly low, for example on a downslope or with strong tail wind, the speed of the motor vehicle is regulated such that the maximum speed is not exceeded or, depending on the design of the control, at most by one control deviation. In this way, an unexpected increase in the speed of the motor vehicle in such situations can be avoided, whereby the operability and road safety of the motor vehicle are further improved.

According to a particularly preferred embodiment of the invention, the minimum speed can be predetermined as a function of the maximum speed. It can thus be provided, for example, that the maximum speed is predetermined, for example by manual input of the driver or by actuation of an operating element for taking over a current speed as the maximum speed, and the minimum speed as a function of the maximum speed, for example in a fixed ratio to the maximum speed determined is. In particular, the minimum speed may be about 80% of the maximum speed. It has been found that in this way a particularly simple and safe operation of the motor vehicle can be made possible, which can correspond in particular to a conventional cruise control system.

Furthermore, it is preferable that the fuel consumption target value is specified at a start time. The start time can be in particular the time of specification of the maximum speed. In particular, the fuel consumption target value can be determined from a current consumption at the start time and may, for example, be equal to the current consumption at the start time. As a result, the feasibility of the method according to the invention and thus the operability of the motor vehicle is further improved. As current fuel consumption, for example, the instantaneous fuel consumption can be used, which can be determined in particular from a sensor signal or from a map based on the current operating parameters of the engine including the instantaneous speed of the motor vehicle. However, the respective current fuel consumption is preferably determined from a current fuel consumption of the motor vehicle averaged over a minimum time or a minimum driving distance. As a result, not only can measurement accuracies be compensated, but even if the motor vehicle is temporarily in a deceleration or acceleration phase at the start time, a fuel consumption setpoint suitable for regulation can be determined.

An inventive device for regulating the speed of a motor vehicle comprises data acquisition means for acquiring data at least on the current fuel consumption and the current speed of the motor vehicle. Furthermore, the device according to the invention comprises input means for inputting a fuel consumption setpoint or establishing a start time, to which a desired value of the fuel consumption and possibly a minimum speed are taken or set. The device according to the invention further comprises processor means, which are set up for determining a manipulated variable for maintaining the fuel consumption setpoint and consumption independently for maintaining the minimum speed, and actuator means for corresponding intervention in the engine control. The device according to the invention is designed in particular for carrying out the above-described method for regulating the speed of the motor vehicle.

The invention will be explained in more detail by way of example with reference to the drawing. It shows: Fig. 1 shows an embodiment of a method according to the invention as

Flow chart. As can be seen from FIG. 1, the method according to the invention for regulating the speed of a motor vehicle is activated at a starting time, for example by actuating an actuating element by the driver. At this time, the maximum speed v _max and the fuel consumption target FC are set _so n, for example, the current speed of the motor vehicle as the maximum speed v _max and the instantaneous fuel consumption FC _ac t of the motor vehicle is taken as setpoint fuel consumption FC _so n. For this purpose, in particular the current speed v _{act of} the motor vehicle is detected continuously; Similarly, the current fuel consumption FC _{act of} the motor vehicle is continuously detected, for example by averaging a continuously detected instantaneous fuel consumption over a predefinable time span or driving distance. The data necessary for this purpose are usually already present in the context of other systems of the motor vehicle, for example in a motor vehicle information system or in a travel computer. Furthermore, a minimum speed v _{min is} set, for example as 80% of the maximum speed v _max or the current speed at the start time. It may be provided that a different, higher or lower percentage of the maximum speed is specified as the minimum speed, or that the minimum speed otherwise depends on the maximum speed.

The current fuel consumption FC _act is now compared with the predetermined fuel consumption target value FCsoii. If the actual fuel consumption FC _{act is} not greater than the desired value FC _so n of the fuel consumption, then it is determined whether the current speed v _{act is} greater than or less than the maximum speed v _max or equal to this. If the current speed v _{act is} less than the maximum speed v _max , which in this case is the set value of a cruise control circle is used, the engine power is increased by increasing the manipulated variable a _t , which represents the operating angle of the accelerator pedal. For this purpose, a _{t is} increased by a predetermined increment. If, on the other hand, the current speed v _{act is} greater than the maximum speed v _max , then a _t is reduced by one increment. If the described speed control method has not been completed, as well as in the case that the current speed v _{act is} equal to the maximum speed v _max , the actual fuel consumption FCact is again compared with the fuel consumption setpoint FC _S0 n.

If the current fuel consumption FC _ac t is greater than the desired value FC _so n of the fuel consumption, it is determined whether the current speed v _{act is} less than or greater than the minimum speed v _min . If the current speed v _act lies below the minimum speed v _min , which in this case serves as the setpoint of a speed control loop, then a _t is incremented by one increment so that the resulting increased power output of the motor increases the speed to reach the minimum speed v _min . On the other hand, if the actual speed v _{act is} greater than the minimum speed v _min , then a _t is lowered by one increment. This reduces the speed of the motor vehicle and the current fuel consumption FC _a ct decreases. If the described control method is not completed, and in the case that the current speed v _ac t already corresponds to the minimum speed v _min , a new comparison of the current fuel consumption FCact with the target value FC _so n of the fuel consumption. The speed of the motor vehicle is thus regulated to maintain the fuel consumption target value FCsoii between the minimum speed ν _ηι , _η and the maximum speed Vmax. When the maximum speed v _ma x is reached, the current speed v _ac t is regulated to the maximum speed v _ma x, wherein the current fuel consumption FC _ac t may be less than the setpoint value FC _so n of the fuel consumption; when the minimum velocity ν _ηι , _η is reached, the current velocity v _ac t is controlled to the minimum velocity ν _ηι , _η , where an increase in fuel consumption FC _ac t is exceeded beyond the setpoint value FC _so n.

Depending on the situation, in particular depending on the increase or decrease in the gradient, the counter or tailwind or the change of other fuel consumption influencing factors, despite an increase in a _t, the current speed v _{act may} remain constant or even decrease further, or vice versa For example, despite a decrease in a _t, the current speed v _{act may} remain unchanged or continue to increase. In this case, in the next comparison of the actual fuel consumption FC _ac t with the desired value FC _so n of the fuel consumption, a correspondingly increased or unchanged deviation of the current speed v _act from the maximum speed v _max or the minimum speed v _{min will be} determined. Such an increase of the deviation may be permissible as a control deviation. However, the control loop can also be designed such that, depending on the size of the deviation, the manipulated variable a _{t is changed} by a different large increment. Furthermore, further known refinements of the speed or fuel consumption control, for example as PID controllers, are possible.

The automatic speed or fuel consumption control example described according to the invention can be activated in a similar manner as known cruise controls by operating a corresponding actuation element, thereby automatically the fuel consumption setpoint FC _so n, the maximum speed v _max and the minimum speed are set v _min. The described control method can be deactivated by actuating a corresponding actuating element by the driver; Preferably, it is provided that the control method according to the invention by pressing the brake pedal, possibly also by pressing the accelerator pedal is terminated.

Claims

claims

1. A method for controlling the speed of a motor vehicle, wherein a current fuel consumption FC _ac t of the motor vehicle is determined and the speed of the motor vehicle is controlled by engaging in an engine control to maintain a predetermined fuel consumption target value FC _so n,

characterized in that

a minimum speed v _{min is} predetermined, which is at least held.

2. The method according to claim 1,

characterized in that

if on reaching the minimum speed V _min, the current fuel consumption FC _ac t fuel consumption FC setpoint _so n exceeds the current speed v _act on the minimum speed v _min is regulated.

3. The method according to claim 2,

characterized in that

a maximum speed v _{max can be} predetermined, which is held at most.

4. The method according to claim 2 or 3,

characterized in that

when on reaching the maximum velocity v _max of the current fuel consumption FC _act fuel consumption Setpoint FC _as n below, a control of the actual speed v _act to the maximum speed v _max occurs.

5. The method according to claim 2 or 3,

characterized in that the minimum speed v _{min is given} as a function of the maximum speed v _max .

6. The method according to any one of the preceding claims,

characterized in that

the minimum speed v _{min is} 80% of the maximum speed v _max .

7. Method according to the preceding claim,

characterized in that

the fuel consumption target value FC is set _so n at a start time.

8. The method according to claim 6 or 7,

characterized in that

the fuel consumption target value FC _so n is determined from the current fuel consumption FCact at the start time.

9. The method according to any one of the preceding claims,

characterized in that

the current fuel consumption FC _ac t is determined from a current fuel consumption averaged over a minimum time span and / or a minimum driving distance.

10. An apparatus for controlling the speed of a motor vehicle, comprising data acquisition means for detecting at least one actual fuel consumption FCact and a current speed v _{act of} the motor vehicle, input means for inputting a fuel consumption target value FC _so n and / or establishing a start time for taking over the fuel consumption target value FCsoii and a Minimum speed v _min , processor means for determining a manipulated variable to maintain the fuel consumption setpoint FCsoii, but at least the minimum speed v _min are set up, and actuator means for engagement according to the determined manipulated variable in the engine control.