GB2350699A

GB2350699A - Setting the controlled speed of a vehicle

Info

Publication number: GB2350699A
Application number: GB0012972A
Authority: GB
Inventors: Thorsten Ott
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-06-02
Filing date: 2000-05-26
Publication date: 2000-12-06
Anticipated expiration: 2020-05-26
Also published as: JP2001001792A; JP4416919B2; DE19925369A1; DE19925369B4; GB0012972D0; GB2350699B

Abstract

The target speed at which the speed of a vehicle is controlled is determined from a signal GP indicative of actuation of an accelerator pedal of the vehicle, and the target speed is returned to a predetermined minimum value on release of the accelerator pedal, and/or is determined by evaluation of a signal BP indicative of actuation of a brake pedal of the vehicle. The target speed Vsoll is set initially to speed Vsollstart as is a preset minimum target speed value Vsollmin. Actuation of the accelerator 104 causes increase of the controlled speed Vsoll and the minimum target speed Vsollmin to new values 108 which are maintained until the accelerator pedal is released, when the controlled speed returns to Vsollmin. Actuation of the brake pedal 120 reduces the controlled speed Vsoll and the minimum target speed value Vsollmin 122. A minimum possible value MIN may be preset for minimum target speed value Vsollmin.

Description

2350699 METHOD AND MEANS FOR CONTROLLING THE SPEED OF A VEHICLE The

present invention relates to a method and means for controlling the speed of a vehicle.

An example of a method and device for controlling vehicle speed is disclosed in DE-A 27 01 567 (US 4 169 437). There, the drive unit of a vehicle is controlled on the basis of a preset target speed subject to consideration of the actual speed of the vehicle, wherein the actual speed of the vehicle is assimilated to the preset target speed. The target speed is derived from the actuation of an operating element which is operable by the driver and which comprises at least three setting ranges for the presetting: one for retardation, one for constant speed and one for acceleration of the vehicle. Consequently, a completely different pedal characteristic results by comparison with conventional vehicles and a vehicle travel behaviour of the vehicle to which the driver is unaccustomed. The known method therefore has only limited suitability for a practical use.

There is therefor a need for a method in which the target speed for speed control of a vehicle can be structured to be comfortable and transparent for the driver without substantially changing the travel behaviour and the pedal characteristics of the vehicle by the driver.

According to a first aspect of the present invention there is provided a method for the control of the speed of a vehicle, wherein at least one setting element, which influences the speed of the vehicle, is actuated in dependence on a target speed preset by the driver, the target speed being derived in dependence on the actuation of at least one operating element, characterised in that the target speed is derived from the actuation of the accelerator pedal of the vehicle, wherein a minimum target speed is preset, to which the target speed is led back on release of the accelerator pedal, and/or wherein the actuation signal of a brake pedal is evaluated and the target speed is ascertained in dependence thereon.

Preferably, that the target speed is reduced in dependence on the actuation of the brake pedal. For preference, the increase or reduction in the target speed is dependent on the magnitude of the deflection of the accelerator pedal and/or of the brake pedal, 2 Expediently, the minimum target speed is increased by the accelerator pedal actuation and lowered by the brake pedal actuation between a lower limit and a maximum value. For preference, the target speed is not variable to below the lower limit of the minimum target speed by actuation of the brake pedal and/or is, however, variable to above the upper limit of the minimum target speed by actuation of the accelerator pedal.

Preferably, the speed control is a speed limiter which is activatable by the driver and, on activation, presets a standard target speed, preferably the maximum value of the minimum target speed, as target speed value. For preference, the target speed is limited to a lower minimum value.

According to a second aspect of the invention there is provided means for controlling the speed of a vehicle, with a control equipment which comprises at least one microcomputer, with an output circuit, by way of which the microcomputer produces at least one drive control signal in dependence on a preset target speed for the actuation of at least one setting element influencing the speed of the vehicle, with an input circuit, by way of which the microcomputer receives an actuating signal of at least one operating element of the driver of the vehicle, characterised in that the microcomputer comprises at least one program which ascertains the target speed in dependence on the actuation signal of an accelerator pedal by the driver and which returns the target speed to a preset minimum target speed on release of the accelerator pedal and/or which evaluates the actuation signal of a brake pedal and ascertains the target speed in dependence thereon.

Preferably, the target speed is limited to a lower minimum value by the program.

A method exemplifying the invention may permit the speed setting of the vehicle by way of at least one operating element, which is controlled by the driver, in a manner which is comfortable and transparent for the driver. In that case, the conventional pedal characteristics and the travel behaviour of the vehicle are maintained to a large extent. If the speed setting is effected by way of an accelerator pedal and a brake pedal, the driver is relieved of the presetting of the speed just as he is accustomed to in the case of currently used travel speed regulators with separate switches.

It is particularly advantageous that the presetting of speed is comprehensible for the driver, and independent of the respective vehicle type, due to association of a change in speed 3 with actuation of the accelerator pedal and due to the association of a reduction in speed with actuation of the brake pedal. It is also independent of whether the vehicle is equipped with automatic transmission or manual transmission.

It is additionally advantageous that a low constant target speed can be preset, which can be adapted in simple mode and manner by the driver. This advantage has particular significance in the case of off-road vehicles, as the driver can adapt the target speed to different terrain in simple mode and manner. Moreover, an increase in travel safety and comfort is achieved through a standard target speed being set again after release of the accelerator pedal or a reduction in the target speed being set by actuation of the brake pedal.

Examples of the method and embodiment of the control means of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram of control means embodying the invention; Fig. 2 is a flow chart illustrating the steps of a method exemplifying the invention; Fig. 3 is a diagram illustrating speed relationships applicable to the method; and Figs. 4a, b and c are diagrams showing speed changes in association with actuations of acceleration and brake pedals.

Referring now to the drawings, there is shown in Fig. 1 a block diagram of control equipment 10 for the control of the speed of a vehicle. In a preferred embodiment, this control equipment comprises, inter alia, a travel speed regulator or limiter and includes an input circuit 12, at least one microcomputer 14 and an output circuit 16, These elements are connected together for data exchange by way of a communication system 18. The input circuit 12 is connected at its input side to an input line 36 from a measuring device equipment 38 for detection of the speed of travel of the vehicle, an input line 40 from a measuring device 42 for detection of the actuation of the vehicle accelerator pedal and an 4 input fine 50 from a measuring device 52 for detection of the actuation of the vehicle brake pedal. In addition, further input lines 20 to 24 from measuring devices 26 to 30 for the detection of further operational magnitudes of the vehicle, which can be evaluated by the control equipment 10, are led to the input circuit 12. Operational magnitudes of that kind include, for example, the wheel brake pressure, the engine torque, the transmission ratios in the drive train and a signal from a switching element actuable by the driver for activation of the speed control.

The microcomputer 14 disposed in the control equipment 10 influences the braking force at at least one wheel brake of the vehicle by way of at least one output line 44 and at least one setting element 46, for example a brake installation with ABS/ASR elements, within the scope of the speed control (travel speed regulation or limitation). In one example, the power of the drive unit of the vehicle is additionally influenced by way of at least one output line 32 and at least one setting device 34, for example an electronic engine control device.

In the microcomputer 14, programs are implemented which control the speed of the vehicle in dependence on a target speed value preset by the driver, the actual speed of the vehicle being made to approach the preset target speed. In the preferred embodiment, a speed limiter, which through action on at least one wheel brake of the vehicle and/or by reduction of the engine torque limits the speed of the vehicle to the target speed preset by the driver, represents the speed control. In other cases of application, the speed control can be a travel speed regulator which maintains the target speed preset by the driver in that the speed of the vehicle is increased if the target speed is fallen below, for example by release of the brake and/or increase in the driving power, and lowered if the target speed is exceeded, for example, by brake action and/or reduction in the driving power. In the described embodiment, the travel speed limiter or regulator is used mainly in the off-road range, for which purpose, particularly in the case of downhill travel, the speed of the vehicle is limited to the preset target speed value by reduction in the engine power and/or by the building-up of braking force at selected wheel brakes. In the case of such an application, and also in the case of other limiting and regulating applications, it is desirable for the target speed to be preset as low and constant as possible and for the driver to be able to adapt the target speed simply to different situations, in particular different terrain situations. The presetting should also be comprehensible for the driver and should relieve the drivers workload analogously to conventional travel speed regulators.

It is therefore provided to undertake setting of a target speed for the speed control by actuation of the brake pedal and the accelerator pedal by the driver. When the speed control is activated, for example by an appropriate activation switch, a predetermined standard target speed has effect. This, can be, for example, in the range of 10 kilometres per hour, but other values are, of course, possible. By actuation of the brake pedal or accelerator pedal, the driver can vary the target speed steplessly (within the scope of the resolution). When the driver thus actuates the accelerator pedal, the target speed is increased, preferably to a magnitude corresponding with the accelerator pedal setting. Correspondingly, the target speed is lowered on reduction in the accelerator pedal setting.On complete release of the accelerator pedal, a minimum target speed is set. On release of the accelerator pedal, a continuous transition of the target speed to this minimum target speed takes place. The minimum target speed is at most the standard target speed preset on activation of the speed control. The minimum target speed is increased according tothe target speed, which forms the basis of the speed control, by actuation of the accelerator pedal as long as it lies below its maximum value. Moreover, a minimum value, which is, for example, in the range of a few kilometres per hour, for example 5 kilometres per hour, is provided for the minimum target speed. By actuation of the brake pedal and braking of the vehicle to below the standard target speed, the standard target speed and the minimum target speed are reduced, for example, both to their minimum value. On actuation of the accelerator pedal, the target speed and the minimum target speed are raised again, in which case the minimum target speed is raised to, at most, the standard target speed. The raising of the target speed by accelerator pedal actuation takes place linearly by a constant factor proportional to the accelerator pedal setting. This proportionality constant should be so dimensioned that the vehicle speed, which results on acceleration of the vehicle in dependence on the accelerator pedal setting, lies below the preset target speed. This relationship is shown by Fig. 5, in which the accelerator pedal setting is entered as a function of the target or actual speed. It is ascertained by application. The raising of the target speed is, however, possible only up to a maximum accelerator pedal setting GPmax. Beyond that, the target speed remains constant.

A possible relationship between target speed and minimum target speed is illustrated in the diagram of Fig. 3, in which the minimum target speed Vsollmin is recorded as a function of the target speed Vsoll forming the basis of the speed control. Also shown are the standard target speed Vsolistart and the minimum value MIN of the minimum target speed. In the range between minimum value MIN and standard target speed Vsollstart, 6 the minimum target speed varies in accordance with the target speed Vsoll. Another embodiment is also feasible, in which, for example, the vehicle speed actually present on the release of the accelerator pedal is utilised as a new target speed insofar as it still lies below the standard target speed Vsolistart. When the target speed is increased beyond the standard target speed, the minimum target speed remains limited to the standard target speed. The same applies at the lower limit for the minimum value. On reduction of the minimum target speed by brake pedal actuation, the vehicle speed, which was present on the release of the brake pedal, is used as new minimum target speed. This must, however, lie below the maximum value of the minimum target speed Vsollstart.

A preferred example of a method utilising the procedure explained above is illustrated by the flow diagram of Fig. 2, which shows actions performable by the microcomputer 14 in execution of a program. It is initiated when the speed control is activated by, for example, actuation of a switch by the driver, as denoted by 'Start'. In a first step 100, the target speed VSOLL is set to the standard target speed Vsollstart. Accordingly, the minimum target speed Vsolimin is set to this value. In a next step 102, the vehicle speed Vf7-, accelerator pedal setting GP and brake pedal setting BP are read in. The vehicle speed, in the preferred example, is derived from at least one selected wheel speed. in other examples, it is measured directly. The accelerator pedal setting is detected by detection of the setting of the accelerator pedal, for example by way of the angle of the throttle flap, whilst the brake pedal setting is ascertained either by detection of the deflection of the brake pedal, the actuating force on the brake pedal or a pressure value, for example bias pressure, influenced by the driver in the brake system. In other examples, it is sufficient, instead of ascertaining the brake pedal setting, to interrogate merely one switch for the states "actuated" and "not actuated". In an interrogation step 104 following the step 102, it is checked whether the driver has actuated the accelerator pedal, i.e. whether the accelerator pedal setting exceeds a minimum value, for example zero. If this is the case, the target speed Vsoll is varied in a following step 108 as function of the accelerator pedal deflection and the minimum target speed (f(GP, Vsolimin)), whilst the minimum target speed experiences a corresponding change in dependence on the accelerator pedal setting subject to limitation to the standard target speed (f(GP, Vsolistart)), as illustrated in Fig. 3. After the step 108, the setting magnitude or magnitudes undertaking the speed control are computed in a step 110 on the basis of target speed Vsoll and vehicle speed Vfz. In the preferred example, a setting magnitude determining the driving torque of the drive unit of the vehicle andlor a setting magnitude determining the braking action at 7 selected wheel brakes is produced in dependence on the difference between target speed and vehicle speed in such a manner that the travel speed is caused to assimilate to the target speed at least when the [after is exceeded. The setting magnitude or magnitudes is or are issued to the corresponding setting device or devices. In a next interrogation step 112, it is checked whether the speed control is for example switched off by the driver. If this is the case, the program is terminated atEnd'; otherwise, it is repeated from step 102. If it is ascertained in the step 104 that the accelerator pedal is not actuated, it is checked in a step 120 whether the brake pedal is actuated. This takes place, for example, by comparison of the signal BP indicating the brake pedal actuation with a minimum value, for example zero, or by evaluation of a switch. If the brake pedal is not actuated, the step I 10 follows with the computation of the setting magnitude or magnitudes in dependence on the actual magnitudes, whilst in the case of the brake pedal having been actuated, the target speed is reduced in a step 122, on the basis of the actuating signal and the minimum target speed is reduced, in a given case to a minimum value MIN, in dependence on the brake pedal actuation.

The effect of the procedure explained above is illustrated with the aid of time diagrams shown in Figs. 4a to c. In that case, Fig. 4a shows the course, in terms of the target speed Vsoll (solid lines), that of the actual speed Vfz (in dashed lines) and that of the minimum target speed Vsollmin (in chain-dotted lines). In addition, the deflection of the accelerator pedal GP as a function of time is entered in Fig. 4b and that of the brake pedal BP in Fig. 4c. After activation of the speed control, the speed control according to Fig. 4a is operated at the standard target speed Vsollstart. The actual speed Vf:z is correspondingly set to this target speed. The brake pedal is actuated at the instant tO (see Fig. 4c) and released at the instant t1. This means that a reduction in the vehicle speed takes place from the instant tO to the instant t1, which has the consequence of a corresponding reduction in the minimum target speed and in the target speed. Between the instants t1 and t2, the target speed present at the instant t1 is made to form the basis of the speed control so that the vehicle speed Vf:z substantially corresponds with the target speed in this range (see Fig. 4a). The accelerator pedal is actuated at the instant t2 and released again at the instant t3. This means that the target speed is increased at the instant Q and the vehicle speed is made to follow correspondingly (see Fig. 4a). The minimum target speed is increased to, at most, the standard target speed Vsollstart. The target speed Vsoll is now increased to the maximum accelerator pedal setting GPmax and then kept constant. Shortly before the instant t3, the accelerator pedal is released (see Fig. 4b), so that the target speed is 8 reduced to the minimum target speed, here the standard target speed. The vehicle speed is reduced to the standard target speed (see Fig. 4a). Between the instants M and t5, the brake pedal is actuated again so that the target speed is reduced from the instant M onward. At the instant t5, the accelerator pedal is released. The minimum target speed remains at the minimum value, as does the target speed, on the basis of which the speed control is then undertaken.

In another example, the maximum value does not correspond with the standard value Vsollstart, but is fixed at another value.

9

Claims

1 A method of controlling the speed of a vehicle, comprising the step of actuating speed-influencing setting means of the vehicle in dependence on a target speed which is determined from a signal indicative of actuation of an accelerator pedal of the vehicle and which is returned to a predetermined minimum value on release of the accelerator pedal and/or which is determined by evaluation of a signal indicative of actuation of a brake pedal of the vehicle.

2. A method as claimed in claiml, wherein the target speed is reduced in dependence on the actuation of the brake pedal.

3. A method as claimed in claim I or claim 2, wherein the target speed is increased or reduced in dependence of the degree of actuation of at least one of the pedals.

4. A method as claimed in any one of the preceding claims, wherein the minimum value for the target speed is increased in response to actuation of the accelerator pedal and reduced in response to actuation of the brake pedal between a lower speed limit and an upper target speed limit.

5. A method as claimed in any one of the preceding claims, wherein the target speed is inhibited from reduction below a lower limit of the minimum value of the target speed and/or is permitted to rise above an upper limit of that minimum value.

6. A method as claimed in any one of the preceding claims, wherein the setting means is a speed limiting device activatable by the driver of the vehicle to set the target speed.

7. A method as claimed in claim 6, wherein the speed limiting device is activatable to set a maximum value of a target speed range as the target value.

8. A method as claimed in any one of the preceding claims, wherein the target speed is limited to a lower minimum value.

9. A method as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

10. Control means for controlling the speed of a vehicle, comprising microprocessing means arranged to receive at least one of a signal indicative of actuation of an accelerator pedal of the vehicle and a signal indicative of actuation of a brake pedal of the vehicle and operable to determine a vehicle target speed which is dependent on the signal indicative of accelerator pedal actuation and which is returned to a predetermined minimum value on release of the accelerator pedal and/or which is dependent on evaluation of the signal indicative of brake pedal actuation, output means to produce a control signal in dependence on the target speed and speed-influencing setting means controllable by the control signal.

11. Means as claimed in claim 10, wherein the microprocessor is operable to limit the target speed to a lower minimum value.

12. Control means for controlling the speed of a vehicle and substantially as hereinbefore descdbed with reference to the accompanying drawings.