DE102004023580A1 - Load control procedure for motor vehicle involves determining target acceleration and traction resistance based on different sets of operating parameters - Google Patents

Abstract

The traction resistance of the motor vehicle is determined based on some of the fixed operating parameters of the motor vehicle and the engine. The target acceleration is determined based on the remaining operating parameters and the traction resistance which indicates if the motor vehicle is headed e.g. on an even roadway, uphill. An independent claim is also included for a controller.

Description

The The present invention relates to a method of controlling the load an engine in a motor vehicle and a control device for performing a such method, in which a target acceleration of the engine based on the values of a given set of operating parameters set the motor vehicle and the engine driven becomes the setpoint acceleration set in this way to realize.

control devices and methods in which a deviation of the actual speed of a motor vehicle is determined by a desired speed and the load is controlled by its engine to the deviation to minimize are under the designations cruise control or cruise control known. A conventional control device of this type allows it to the driver of a motor vehicle, without own accelerator pedal operation Driving constant speed by looking for deviations from the target speed by automatically correcting the position of a throttle. In the simplest case leads e.g. a PID controller to the throttle position, by at a Drop of the actual speed of the vehicle below the set speed the throttle opening slight elevated and with an increase in the actual speed over the target speed the throttle opening is reduced. As a rule, such a control device has control elements, which a driver can operate to change the setpoint of the speed and thus accelerate targeted or to delay, or by a previously set target speed after a temporary interruption of automatic speed control to resume.

A abrupt change Throttle position can cause a violent reaction of the vehicle to lead, which can be perceived by the driver as inappropriate or annoying, especially when in a low gear, the change of the throttle position to a short-term, clearly noticeable acceleration thrust leads, or if at higher Speed, in a higher gear, a clearly noticeable or audible Engine response to a small percentage, subjective from the driver hardly perceived speed deviation occurs, especially then if the acceleration process even with an automatic temporary switchback connected to a lower gear.

From the US 6,278,931 B1 An improved speed control device is known, which calculates an offset proportional to the speed deviation address parameter for the correction of speed deviations and adjusts a value assigned to the thus obtained address parameter position on a throttle valve of the engine.

In the DE 102 08 155 A1 a method is described which determines a desired acceleration from an accelerator pedal position set by the driver and controls the engine such that this desired acceleration is implemented independently of the engaged gear or other influences.

At the Practical driving with these sophisticated systems becomes common complains that the perfect adherence to a constant speed at the uphill and Downhill driving is subjectively perceived by the driver as unpleasant. This stirs Part, therefore, that during the transition from a flat to a rising lane a quick response the control device causes that the driver suddenly a gravity component in the longitudinal direction of the vehicle get to feel him against the backrest of the seat presses and feels the same way like a sudden acceleration. The thus created illusion of a not controlled by the driver Acceleration is unsettling and unpleasant.

at a vehicle without automatic cruise control occurs this effect does not occur, because if such a vehicle suddenly from If you get on a level track on a level track, it slows down first, and an acceleration component that pushes the rider against the backrest of the driver Seat pushes, only then becomes tangible, when the driver depresses the accelerator pedal to the initial deceleration to compensate. But then he expects to feel such power, and the feeling of lacking control over the vehicle stays off.

Another problem of the known speed control devices and methods is that vehicle crews tend to reduce speed on inclines due to the fact that drivers of vehicles that do not have such a control device tend to transition into an uphill section to increase the engine power only with a considerable delay. A driver traveling in a convoy of predominantly conventional, non-automatic, speed-controlled vehicles will therefore often find that he is undesirably close to a preceding vehicle because he / she is decelerating over a longer time but not his / her own. As a result, he is forced to counteract what is actually the purpose of the speed control device is.

task The present invention is a method and an apparatus for controlling the load of an engine in a motor vehicle indicate that the abovementioned disadvantages are avoided.

The Task is solved by a method with the features of claim 1 and a control unit with the Features of claim 11.

The Detecting the driving resistance of the vehicle allows a road gradient to recognize and the impression of a not controlled by the driver Avoid acceleration by setting the target acceleration with the in the case of a discrepancy between the target and the actual speed the actual value is corrected, the smaller the higher the Travel resistance, i. the slope is. This measure will the driving behavior of the vehicle that of conventional, not automatic speed-controlled vehicles made more similar, so too the need for uphill convoy driving in the control intervene is reduced.

Preferably, the target acceleration a _{soll of} the engine is determined based on a function of the shape a should = f (W) g (p 1 , ..., p n ) wherein W denotes the determined driving resistance and p ₁ ,..., p _n denotes the further parameters of the given parameter set. By the determined driving resistance W or its function f as a correction factor f enter into the determination of the target acceleration, the number of required to represent the dependency of a _is required by their various parameters characteristic curves is kept low.

It is further preferred that f (W) has a constant value below a limit value W _{0 of} the driving resistance and decreases above the limit value W ₀ with the driving resistance. By setting this limit value approximately equal to the running resistance of the vehicle when driving on a level road, it is achieved that the target acceleration is not influenced by a slope of the road, while it is smaller with increasing slope of the road. This ensures that when the invention is used in the context of a cruise control or cruise control system, the acceleration, with which a deviation between the actual and target speed is corrected, when driving downhill is relatively high and independent of the gradient, while It is smaller when driving uphill and decreases with increasing slope, so as to achieve a better adaptation to the driving style of non-cruise-controlled vehicles.

The Function f should be positive even with high values of the driving resistance be.

In the simplest case, the limit value W ₀ , which is to correspond to the driving resistance when driving on a level road, may be a typical value or an estimated value which is fixed and corresponds to a driving resistance value expected for the relevant motor vehicle. This limit value should be specified as a function of the actual speed and possibly of the gear currently engaged in a transmission of the vehicle.

A improved flexibility However, the control is achieved when the value of the driving resistance when driving on a level road during of driving is measured. So can also external influencing factors such as the type of tires, the payload, the nature of the tires road surface etc. are taken into account when setting the limit value.

If the motor vehicle in usual Way has a multi-step transmission, also belongs in the step transmission inlaid gear to the for the determination of the target acceleration to be considered Parameter set. You will get the target acceleration at the same time Values of the rest The higher the parameter, the lower the parameter pickled gear is.

To The parameter set should also have a deviation between the setpoint and the Actual speed of the vehicle belong. Then the target acceleration preferably set at the same values of the other parameters, the higher, the stronger the Target speed exceeds the actual speed. In particular, a minimum value for the difference between actual and target speed be given, which exceeded must be, so at all a nonzero nominal acceleration of the vehicle is determined.

Further Features and advantages of the invention will become apparent from the following Description of exemplary embodiments with reference to the attached Characters. Show it:

1 a diagram of a motor vehicle, on which the present invention is realized;

2 a diagram for illustration the determination of the target acceleration as a function of the driving resistance; and

3 a flowchart of a load control method according to the invention.

This in 1 schematically illustrated vehicle includes an internal combustion engine 1 and one over a crankshaft 3 the engine 1 driven step transmission 4 in which is under the control of a control circuit 5 Different gears are adjustable to the torque of the engine 1 on wheels 6 transferred to. The control circuit 5 has a manual mode of operation in which they load the engine 1 as specified by the driver according to the position of an accelerator pedal 7 controls, and an automatic operating mode in which it controls the speed of the vehicle based on a setpoint speed set by the driver. In the control circuit 5 a number of characteristic curves are stored, which depend on a desired output torque of the engine 1 and its speed one or more load control parameters such as fuel injection quantity, ignition timing, air-fuel ratio, etc. of the engine for the various gears of the stepped transmission 4 specify that must be adjusted to realize the desired output torque.

The control circuit 5 also has an acceleration sensor for measuring the acceleration of the vehicle in the direction of travel or means for indirectly determining the acceleration by forming the time derivative of a speedometer 8th measured speed.

The following description deals only with the automatic operation mode of the control circuit 5 in which this is the engine 1 controls to maintain a predetermined target speed of the vehicle.

For this purpose, the control circuit cyclically performs the in 3 shown method. In step S1, a series of parameter values p ₁ ,..., P _{n are} determined, which are relevant for a decision of the control circuit about the load of the engine to be controlled. Among other things, these parameters include the actual speed v _{ist of} the vehicle, the difference between the actual speed and the setpoint speed v _soll set by the driver, which is currently in the transmission 4 pickled gear, etc ..

In step S2, it is compared whether the difference between the target and actual speeds is greater than an allowable difference Δ. If not, obviously, the currently set load is appropriate to keep the vehicle at the target speed v _soll , and the process goes directly to step S11, in which the internal combustion engine 1 is driven with the same set of values of its load control parameters as in the previous run of the method. This is generally the case as long as the vehicle is moving on a flat lane or lane with a constant grade.

As the road gradient changes, the load of the internal combustion engine required to maintain the target speed also changes 1 or as long as it is not adapted to the changed road conditions, the vehicle speed changes. Consequently, if in step S2, the difference between the target and actual speed exceeds the limit Δ, an adjustment of this load is required.

In order to control this load adaptation, the current driving resistance of the vehicle is first determined. For this purpose, the actual acceleration of the vehicle is first determined in step S3 by direct measurement or by forming the time derivative of the speed measured by a speedometer. An idealized acceleration is obtained in step S4 by the output torque of the engine 1 at the level of the crankshaft with the current gear of the stepped gearbox 4 multiplied and by the radius of the driven wheels 6 and the mass of the vehicle is divided. The acceleration value thus obtained corresponds to the value that would result when driving without external driving resistance (rolling resistance, aerodynamic drag, gradient resistance) if the transmission and chassis were free of friction and other losses. The output torque can be obtained by directly measuring a torsional load of the crankshaft or by calculating from the load control parameters of the engine using a mathematical model.

The difference between the actual acceleration and the idealized acceleration is composed of the deceleration caused by losses in the drivetrain and the rolling friction of the wheels, and the downhill acceleration acting on the vehicle and the air resistance acting on the vehicle. The acceleration deviation due to driveline losses, air resistance and rolling friction is a clear function of the speed of the vehicle and the engaged gear, of which a mathematical description, for example in the form of one or more characteristic curves, in a memory of the control circuit 5 is stored.

In step S6, the value of the running resistance W calculated in the preceding step S5 is set to one of the actual speed of the driving and the gear engaged limiting value W ₀ (v _ist ) compared. According to one embodiment, this limit value is the value of the above-mentioned characteristic curve or characteristic curves for the actual speed v _ist . If it is determined in step S6 that W is less than or equal to W ₀ (v _is ), it means that the vehicle is moving on a flat or sloping road; In this case, the process branches to step S7, in which f (W) = 1 is set as the value of a function f (W) of the running resistance whose function will become more apparent later. The course of the function as a function of the driving resistance W is in 2 shown; Step S7 corresponds to the constant course of this function with arguments ≤ W ₀ .

If it is determined in step S6 that the calculated actual running resistance W is greater than the limit value W ₀ (v _is ), then in step S8, for example, the value of the function f (W) = exp (c (v _ist ) (W ₀ - W)) is set, wherein a positive function of the actual speed v c _is. This corresponds to the exponential decline in 2 shown function f (W) for arguments greater than W ₀ . For large driving resistances, f (W) can be close to zero, but never becomes negative. c _(v) is a is connected to the actual velocity v _is increasing function, that is the decrease of f (W) above the limit value W ₀ is, the higher the actual velocity v _is steeper.

Alternatively, the function f (W) could also have the form f (W) = 1 - d (v _ist ) (W ₀ - W), where d is a positive function of v _, chosen to be f for each Value of the driving resistance below the full load remains positive.

In step S9, a target acceleration of the vehicle a _{soll is} calculated according to the formula a _soll = f (W) × g (p ₁ ,..., P _n ), where g is a predetermined function of the above-mentioned parameters p ₁ ,. .., p _n.

There are a variety of ways to set the function g. One possibility is, for example, that the amount of g is a constant dependent only on the engaged gear and the sign of g corresponds to the velocity deviation v _soll - v _ist . In this case, as the target acceleration a _soll, a value is obtained whose sign corresponds to that of the speed deviation, so that the speed deviation is actually reduced by accelerating with the target acceleration, but the amount of the target acceleration is smaller in each case , The higher the gear is a set, and moreover by the influence of the factor f when driving uphill with increasing road resistance continues to decrease. That is, if, as a result of a transition of the vehicle on a downhill route, the actual speed exceeds the target speed, fixed for correcting this deviation (negative) target acceleration depends only on the engaged gear. In the case of falling below the target speed due to a transition to a rising road, it also decreases with increasing road resistance. Thus, the behavior of the vehicle is better adapted to that of conventional, manually speed-controlled vehicles.

It can also be provided that the function g v _soll for a speed deviation - v _is proportional term includes; In this case, the target acceleration increases in deviations from the target speed, both up and down in proportion to the amount of deviation, but is again smaller when driving uphill with high driving resistance than when driving on a flat or sloping track.

Taking into consideration the running resistance calculated in step S5, a target torque T _{soll of} the engine becomes in step S10 1 which it must generate, in order to achieve the target acceleration a _{soll of} the vehicle, and the parameter values of the load control parameters of the engine required for generating this torque are determined.

In Step S11, the control of the engine with the respective applicable values of the load control parameters.

In the embodiment described above, the threshold value W ₀ (v) was assumed to be exactly the value of the driving resistance when driving on a level road with the speed V v. However, the limit value can also be assumed to be slightly greater than this driving resistance, in order to avoid a slowdown of the speed reduction for small gradients.

The description or characteristic curve of the driving resistance as a function of the speed and the engaged gear can be specified unambiguously and immutable in the simplest case. According to a further development, the driver can be offered a choice between several descriptions which can correspond to different driving situations, such as driving with or without payload, with summer tires or with winter tires, etc. It is also possible to provide the possibility that the description of the running resistance during the operation of the vehicle is dynamically adjusted by averaging values of the running resistance calculated for a given value of the vehicle speed and the engaged gear in step S5 over a long period of time, and the average value is assumed as driving resistance on a level roadway, where assuming that the averaging period is so long that the slope-dependent component of the driving resistance is determined.

 1

combustion engine

 2

 3

crankshaft

4

step transmission

 5

control circuit

6

bikes

7

accelerator

8th

speedometer

Claims (12)

Method for controlling the load of an engine ( 1 ) in a motor vehicle in which a desired acceleration of the motor vehicle is determined on the basis of the values of a predefined set of operating parameters of the motor vehicle (S8) and the engine ( 1 ) is driven (S11) to realize the target acceleration, characterized in that the driving resistance of the vehicle belongs to the predetermined set of operating parameters, that the driving resistance is determined (S3-S5) and that the target acceleration at the same values The lower the determined value of the driving resistance, the lower is set for the other parameters (S6-S9). A method according to claim 1, characterized in that the target acceleration a _{is to} be determined by a function of the form a should = f (W) g (p 1 , ..., p n ) where W denotes the determined driving resistance and p ₁ ,..., p _{n designate} further parameters of the given set. Method according to Claim 2, characterized in that f (W) has a value independent of the driving resistance W below a limit value W ₀ (S) and decreases above the limit value W ₀ as the driving resistance W increases (S8). A method according to claim 3, characterized in that the limit value W ₀ corresponds to the value of the driving resistance W when driving on a level road. Method according to claim 4, characterized in that that the value of the driving resistance when driving on a level road while of driving is measured. Method according to one of the preceding claims, characterized in that in a motor vehicle with a manual transmission ( 4 ) in the manual transmission ( 4 ) engaged gear belongs to the parameter set. Method according to Claim 6, characterized that the target acceleration at the same values of the other parameters the lower the higher the gear engaged. Method according to one of the preceding claims, characterized characterized in that the parameter set a deviation between Target and actual speed of the vehicle heard. Method according to claim 8, characterized in that that the target acceleration at the same values of the other parameters the higher is set, the stronger the set speed exceeds the actual speed. Method according to one of the preceding claims, characterized in that the actual speed of the Vehicle belongs. Method according to claim 10, characterized in that that the target acceleration at the same values of the other parameters the lower the higher the actual speed is. Control unit ( 5 ) for the engine ( 1 ) of a motor vehicle which is set up, the load of the engine ( 1 ) with a method according to any one of the preceding claims.