DE102022209045A1 - Method for tracking a vehicle, control device, vehicle and computer program - Google Patents

Abstract

The invention relates to a method for tracking a vehicle (1), wherein a manipulated variable is determined by a lateral control (7) depending on a lateral offset error (4) of the vehicle (1) relative to a predetermined target trajectory (5), wherein a Transverse position of the vehicle (1) is adjusted to the desired trajectory (5) as a function of the manipulated variable, wherein the manipulated variable is additionally subjected to at least one calibration value, the calibration value being determined at least partially as a function of a temporal integration of the transverse positioning error by at least one calibration function (12). becomes.

Description

The invention relates to a method for tracking a vehicle, wherein a manipulated variable is determined by a lateral control as a function of a lateral offset error describing a lateral offset of the vehicle from a predetermined target trajectory, a transverse position of the vehicle being adjusted to the target trajectory depending on the manipulated variable. The invention further relates to a control device, a vehicle and a computer program.

Vehicles can be equipped with systems or functions for automatic lane guidance. These make it possible to automatically adjust the lateral position of the vehicle while driving according to a predetermined trajectory. The lateral position of the vehicle, i.e. the lateral position of the vehicle in a lane, can be changed, for example, by automated steering movements or adjusted to a target position.

Such lane keeping functions generally use environmental data, which was obtained using sensors for detecting the vehicle's surroundings, for example cameras, radar, or lidar systems, and/or using a navigation system, for example a GPS, in order to guide vehicles along a planned trajectory lead. For example, the trajectory is designed for a high level of driving comfort and therefore does not contain any strong or rapid changes in the vehicle's transverse position. The guidance of the vehicle along such a trajectory is usually carried out as a control in which at least the lateral deviation of the vehicle from the planned trajectory is continuously determined, with control commands of suitable size and direction being sent to an electric steering assistance system depending on the deviation, for example vehicle. Criteria for assessing the control quality of such systems include, for example, the amplitude and dynamics of the lateral control deviation and the frequency of jerky movements on a vehicle steering wheel. Ideally, the lateral control error is zero for all driving situations, so that the steering interventions due to the lane guidance or the resulting steering wheel movements are solely determined by the course of the planned trajectory.

The performance of such tracking depends on the quality and quality of the sensors and actuators used in the vehicle. To a certain extent, the performance of an overall system can generally be increased by using several sensors or several actuators and/or by using suitable software measures. This applies in particular to driver assistance systems, such as those that provide lane keeping support functions.

Nevertheless, sensor errors of the sensors, i.e. any deviation of a sensor signal from its physical counterpart, influence the character of the control and thus also the control quality of the vehicle's tracking, in particular due to the error propagation that occurs. Depending on the sensor information, sometimes different and sometimes overlapping effect chains come into play.

An imaging error in the camera detecting the lane markings can, for example, lead to the determined curvature of the road deviating from the real curvature, which represents a so-called ground truth error. The lane guidance generally includes at least one controller and/or at least one pilot control, which adjusts the lateral vehicle position depending on the determined road curvature. Curvature information describing the road curvature, often determined in a look-ahead point of the vehicle, can be used to calculate the steering angle required for the respective curvature using an inverted vehicle model and to use this as a target steering angle, for example as part of a pilot control. Switch component to a steering angle controller.

If the curvature information now has an offset in comparison to the actual curvature due to an error, the pilot-controlled target steering angle also contains an offset component, which acts like a disturbance to the lateral control. This has the effect that when lane keeping assistance is activated, the vehicle does not follow the trajectory as expected, but instead has a permanent lateral offset from the planned trajectory, or at least depending on the design of the lateral control or a trajectory following controller - i.e. use of controller types with or without stationary accuracy a transient swerve occurs before the vehicle then follows the planned trajectory after a compensation process has subsided. The permanent or transient lateral offset can impair driving comfort, which can have a detrimental effect on the driver's acceptance of the driving assistance system.

The degree of imaging errors in the camera usually varies over the operating period of the driver assistance system, since calibration routines of the camera are typically carried out continuously. This means that, depending on the status of the camera calibration, the height of an offset of the curvature pre-control and thus also the degree of impairment of the vehicle lateral guidance vary over time, although the transmission properties of the camera and thus also the offset of the curvature do not change suddenly, but rather band-limited or gradually change.

The steering angle usually represents a significant auxiliary or controlled variable within a track-guided assistance system, so routines are often used to calibrate a steering angle offset. The steering angle offset determined in this way always has an uncompensated portion due to the finite accuracy of the calibration routines. This remaining offset error in a steering angle signal can have several causes. Typical calibration routines rely, for example, on the signal from a yaw rate sensor or a wheel speed sensor. Errors in these sensors, such as an offset and/or a linearity error, or in the case of wheel speed sensors, speed differences due to different pressures on the tires on an axle, then propagate to the determined steering angle offset. The effects of steering angle offsets are comparable to the case of a curvature offset described above: Here, too, when lane keeping assistance is activated, the vehicle does not follow the specified trajectory as expected, but instead has a permanent or transient lateral offset depending on the design of the lateral control or the trajectory following controller on the planned trajectory with the adverse effects on the comfort and acceptance of the driver assistance system.

This applies equally to an uncompensated offset of a front axle steering angle and a rear axle steering angle.

The sensor signals for the yaw rate, the front and rear axle steering angles as well as for lateral acceleration can in particular also be used for other functions within the vehicle, which can also influence a lateral position or the lateral guidance of the vehicle. For example, these sensor signals can also be used to estimate disruptive forces and load moments acting on the vehicle as well as to estimate a slip angle of the vehicle, for example as a result of a road inclination and/or crosswind. In such a case, the determined variables then also contribute to the vehicle lateral guidance as a target steering angle component in the course of a disturbance variable feed-in, with in particular corresponding offsets of the sensor signals also propagating as errors on the target steering angle and thus the lateral position of the vehicle. Here too, the result is an undesirable transient or permanent lateral displacement of the track-guided vehicle.

Out of DE 10 2008 026 233 B4 a method for offset compensation of a steering angle in a motor vehicle using a vehicle model is known. A yaw rate is calculated depending on a detected steering angle, a vehicle speed and an assumed steering wheel angle offset. Furthermore, the calculated yaw rate is compared with a measured yaw rate, the difference between which forms an error equation, from which a steering wheel angle offset is then determined, which is fed back into the vehicle model in order to iteratively determine and compensate for the steering wheel angle offset.

Such an offset calibration of a yaw rate or a lateral acceleration has a finite accuracy and always lags behind the real offset, which can result in additional, undesirable steering interventions even in the presence of this.

The invention is based on the object of improving the accuracy of the tracking of a vehicle and thus the driving comfort and the acceptance of the assistance system by the driver, even under the influence of offset errors.

To solve this problem, in a method of the type mentioned at the outset, it is provided according to the invention that the manipulated variable is additionally subjected to at least one calibration value, the calibration value being determined by at least one calibration function at least partially as a function of a temporal integration of the transverse offset error.

The vehicle transverse position is adjusted using the sum of the manipulated variable and the at least one calibration value. Depending on the design of the lateral control and/or the tracking, it is possible for further components to be applied to the manipulated variable in addition to the at least one calibration value.

The manipulated variable to which the calibration value is applied influences the transverse position of the vehicle. The manipulated variable can be, for example, a target steering angle. This can be specified, for example, at a steering angle interface to an electric power steering (EPS). Alternatively, it is also possible to specify the manipulated variable at a torque interface of an EPS that causes a steering torque or a steering angle.

The calibration value is determined by the calibration function, in particular depending on the sign and the amplitude of the integrated transverse offset error, in such a way that the calibration value is always aimed at reducing the current transverse offset error when the manipulated variable is applied. By applying the calibration value to the manipulated variable, it is achieved that the target steering angle is corrected or compensated for by the time-integrated transverse offset error.

The transverse storage error describes the lateral or lateral offset of the vehicle, i.e. an offset in the transverse direction of the vehicle, to the specified target trajectory. The transverse offset error can therefore also be referred to as lateral offset or lateral deviation. In other words, the transverse positioning error expresses the current deviation of an actual vehicle position from a desired vehicle target position described by the target trajectory. The determination of the lateral offset of the vehicle relative to the target trajectory can be based on an agreed point along the longitudinal axis of the vehicle. The lateral offset can advantageously be related to the geometric center of the rear axle or the front axle or to any other look-ahead point along the vehicle's longitudinal axis.

The transverse storage error can be continuously determined, for example, depending on sensor data from at least one environment sensor of the vehicle. The environment sensor can be, for example, a camera, a lidar sensor, a radar sensor and/or an ultrasonic sensor. Additionally or alternatively, the transverse offset error can also be determined depending on position data from a navigation system. The transverse offset error has a time-dependent value, which is integrated by the calibration function.

The lateral controller used for lateral control can be, for example, or include a trajectory sequence controller. The calibration function, which can also be referred to as centering calibration or centering function, is present in addition to the trajectory tracking control and thus forms a secondary or higher-level control loop, which also influences the manipulated variable and thus also the lateral position of the vehicle. In particular, the dynamics of the calibration function is significantly lower than the dynamics of the lateral control, so that the temporally integrated lateral offset error only very slowly influences the manipulated variable.

For example, an integrator with a comparatively small integration coefficient can be used as a calibration function or as a basic calculation rule for determining the calibration value, which results in an integration of the transverse offset error with low dynamics and thus also an influence of the calibration value with low dynamics.

According to the invention, the at least one calibration function can each be designed as an I element or as a PT1 element. A PT1 element also has an integrating property compared to a pure I element, but as an advantage it does not require any of the measures necessary for I elements to limit the integrator state. This advantage must be weighed up against the disadvantage of the non-stationary, exact compensation of the offset variables in the respective application by making use of the parametrization degrees of freedom of the PT1 element.

The adaptation dynamics of the calibration value is in particular dimensioned such that it is of the order of magnitude of the change dynamics of the offset errors. One measure for this is, for example, the largest expected, temperature-related offset drift of the sensors used for lateral control, converted to the corresponding steering angle level. This has the advantage that no overshooting of the lateral control occurs, which, for example with a higher dynamic of the calibration function, would lead to an intervention of further compensation functions acting on the steering angle, such as compensation for a road side inclination and/or crosswind compensation.

By using the at least one calibration function or by applying the at least one calibration value to the manipulated variable, it is advantageously achieved that offset errors that continuously affect the tracking are partially or completely reduced over time. these offset errors are partially or completely compensated over time. Compensation functions that affect the steering angle are often not continuously active. For example, a lane keeping function usually only becomes effective after activation by the driver. If the compensation functions derive a supposed control error due to the offset errors at the time of their activation, the compensation functions will output manipulated variables in an attempt to reduce the control error. Depending on the dynamics of the compensation functions, this can lead to jerky steering movements. By compensating for the offset errors in advance, the occurrence of jerky steering movements in order to correct a built-up lateral offset can advantageously be avoided, thereby improving the comfort for an occupant when lane guidance is activated. This also improves the acceptance of the lane guidance or the driver assistance system that effects the lane guidance.

In summary, the basic idea of the higher-level calibration function can also be interpreted as a fixed value control of low dynamics with a setpoint of zero for the transverse offset error. In terms of its effect, it reduces the sum of all direct and indirect offset influences of the sensors used in the network on the lateral offset of the vehicle during automatic lateral or lane guidance.

According to the invention, it can be provided that the time constant of the calibration function is larger, in particular by at least a factor of 2, than the dominant time constant of the lateral control. Preferably, the time constant of the calibration function can also be greater than the dominant time constant of the lateral control by at least a factor of 5, at least a factor of 10, at least a factor of 100 or at least a factor of 1000. In principle, even larger differences between the time constants are conceivable. A calibration function implemented, for example, as an I-term can, for example, have an integration coefficient between 0.01 degrees/(m*s) and 0.00005 degrees/(m*s).

In a preferred embodiment of the invention, it can be provided that an integration value of the calibration function is determined by the temporal integration of the transverse offset error, the integration value being retained when the tracking is deactivated and used as the starting value of the temporal integration of the transverse offset error when the tracking is reactivated.

The integration value describes the total value that was formed by the temporal integration of the transverse offset error up to a point in time assigned to the integration value. The integration value therefore represents the result of the temporal integration of the transverse offset error up to this point in time for a specific point in time. If several calibration functions are used, an integration value assigned to the respective calibration function is formed in particular for each of the calibration functions separately. The at least one integration value can be stored, for example, in a storage device of a computing device executing the method, such as a control device, in a retrievable manner.

The state of the calibration function, i.e. the state of an integrator forming the calibration function or a comparable functional unit, is not reset, for example, in the current ignition run of the vehicle, but is maintained even when the driver assistance is repeatedly deactivated and activated or during driver interventions. However, a reset of the integrator in the event of a detected implausible activity, for example in the event of a detected or communicated jump in the output of one or more offset calibrations of the vehicle sensors, or in the event of a request via a diagnostic interface of the vehicle, can also be provided. It is possible for the integration value to be maintained even beyond one ignition run of the vehicle, i.e. over several trips.

According to the invention, it can be provided that the lateral control includes a pilot control, wherein the pilot control determines a pilot control variable depending on a measured and / or predicted curvature value of a road traveled by the vehicle, the manipulated variable containing the pilot control variable as a component.

A measured curvature value and/or a predicted curvature value can be determined in particular from the sensor data from one or more of the vehicle's surroundings sensors. The pilot control can, in particular, use the measured curvature value and/or the predicted curvature value to calculate the steering angle required for the respective curvature via an inverted vehicle model and switch this as a pilot control variable, for example to the manipulated variable of a trajectory follower controller of the lateral control. The vehicle model changes its transmission behavior depending on the vehicle speed. This shows that an error in the measured curvature value has an influence on the lateral guidance of the vehicle that is dependent on the vehicle speed.

According to the invention, it can be provided that the pre-control takes place as a function of a vehicle model describing a self-steering gradient of the vehicle, the self-steering gradient being adjusted during operation of the vehicle as a function of at least one vehicle parameter, in particular a vehicle mass and/or a tire stiffness.

When the vehicle is cornering, the transverse positioning error due to a pilot control error depends not only on an offset error in the curvature, but also on the inaccuracy of the stored vehicle parameters, in particular on uncertainties of a self-steering gradient used in the vehicle model. An error or a deviation in the self-steering gradient has the effect of a disturbance on the lateral control of the vehicle and therefore also causes an additional lateral positioning error, which leads to an incorrect deflection of the calibration value generated by the calibration function. In such a case, the calibration value does not only react to sensor offset sizes. However, as long as the errors or deviations in the self-steering gradient are limited, their impact is only small due to the low dynamics of the calibration function.

In order to avoid the influence of larger errors and/or deviations in the self-steering gradient, this can be adjusted, in particular continuously, depending on at least one vehicle parameter. The adaptation can take place, for example, depending on a current vehicle mass, a current tire stiffness of one or more tires of the vehicle and/or other parameters of the vehicle.

In a preferred embodiment of the invention, it can be provided that the temporal integration of the transverse offset error takes place with a weighting factor, in particular an integrating coefficient, which depends on a speed of the vehicle and/or increases as the magnitude of the transverse offset error increases.

For example, while the use of a constant integration coefficient can represent an easy-to-implement compromise for the entire speed range of the vehicle, using a speed-dependent integration coefficient or a comparable integration weighting factor has the advantage that better compensation of speed-dependent offsets is possible. The influence of offset variables on the lateral offset error can arise, for example, due to the commonly used setting of the control parameters of the lateral control depending on the driving speed of the vehicle. This also changes the interference compensation properties of the transverse control and thus also the effect of sensor offset variables on the transverse offset error. In order to take this circumstance into account, the temporal integration can also be made dependent on the driving speed by using a speed-dependent weighting factor, such as a speed-dependent integration coefficient. Advantageously, an ideal, individually adapted calibration dynamic can be achieved for each driving speed range.

Additionally or alternatively, it is possible for the weighting factor to also be made dependent on the amount of the transverse offset error, i.e. on the value of a transverse offset error to be integrated and/or a previously integrated transverse offset error, with greater weighting being carried out for larger values of the transverse offset error. For this purpose, for example, an assigned weighting factor or integration coefficient can be determined for the current transverse offset error depending on a non-linear assignment rule and/or one or more threshold values for the transverse offset error and used in the temporal integration of the transverse offset error. The calibration speed can be effectively increased by progressively weighting the amount of the transverse offset error, i.e. by increasing the weighting factor or integration coefficient as the amount of the transverse offset error increases.

For this purpose, for example, the integration coefficient and thus the adaptation rate of the calibration function can be switched between two or more values, with the integration coefficient being chosen higher for larger absolute values of the transverse offset error. Advantageously, doubling the integration coefficient or the integration constant for an amount of the transverse offset error of more than 0.2 m leads to an effective, faster initial adjustment to the existing offset situation when the driver assistance function is started.

Even in the case that the vehicle has an additional sensor offset calibration function, which corrects a detected offset drift of at least one sensor of the vehicle after a confirmation time or a debounce time has elapsed with a sudden correction of the respective offset, an increase in the adaptation rate can be achieved The centering calibration, depending on the amount of the transverse offset error, ensures a quicker adjustment to the new offset situation. This becomes all the more important the longer the debounce time of the sensor offset calibration functions is, since during this period the calibration function increasingly compensates due to the temporal integration of the transverse offset error, which returns again after a signal update of the sensor offset calibration functions needs to be integrated. Advantageously, the speed of the equalization process can be increased by using a larger weighting or a larger integration value.

Since sudden corrections of a sensor offset calibration function of the vehicle directly lead to a lateral jerk of the track-guided vehicle, which depends on the jump height, it can be provided for a vehicle which includes a control device designed to carry out a method according to the invention that all sensor The offset calibration functions in the vehicle do not change the respective offset suddenly, but only within a band.

• - der oder ein durch die zeitliche Integration des Querablagefehlers ermittelte Integrationswert der Kalibrierfunktion einem vorgegebenen Grenzwert entspricht,
• - der oder ein gemessener und/oder prädizierter Krümmungswerts der oder einer von dem Fahrzeug befahrenen Fahrbahn einen vorgegebenen Schwellwert übersteigt,
• - ein Krümmungswert der Solltrajektorie einen vorgegebenen Schwellwert übersteigt,
• - das Produkt aus dem Quadrat der aktuellen Fahrzeuggeschwindigkeit und dem Krümmungswert der Fahrbahn einen vorgegebenen Schwellwert übersteigt, und/oder
• - das Produkt aus dem Quadrat der aktuellen Fahrzeuggeschwindigkeit und dem Krümmungswert der Solltrajektorie einen vorgegebenen Schwellwert übersteigt.

According to the invention, it can be provided that the temporal integration of the transverse offset error is stopped by the calibration function if:

• - the or an integration value of the calibration function determined by the temporal integration of the transverse offset error corresponds to a predetermined limit value,
• - the or a measured and/or predicted curvature value of the or a road traveled by the vehicle exceeds a predetermined threshold value,
• - a curvature value of the target trajectory exceeds a predetermined threshold value,
• - the product of the square of the current vehicle speed and the curvature value of the road exceeds a predetermined threshold value, and / or
• - the product of the square of the current vehicle speed and the curvature value of the target trajectory exceeds a predetermined threshold value.

The contribution of the calibration value to the manipulated variable can be limited to a limit value by at least temporarily stopping the temporal integration of the transverse offset error in the calibration function, or by limiting an overall value of the integration to the limit value. The limit value represents a maximum amplitude and can, for example, be based on a sum of the maximum influences of all offset variables on the steering angle setpoint and the actual steering angle value. This procedure advantageously allows the provision of measures to avoid integrator windup effects in the calibration function to be dispensed with.

As an alternative to limiting the integrator value to a limit value, the calibration function can also include a low-pass filter function, for example a PT-1 filter. This can also avoid windup effects. Although a sensor offset cannot be completely compensated for, the centering accuracy achieved through the calibration function can still be sufficient.

Additionally or alternatively, it is possible for the temporal integration of the transverse offset error to be stopped by the calibration function if the or a measured and/or predicted curvature value of the or a road traveled by the vehicle exceeds a predetermined threshold value and/or if a curvature value of the target trajectory exceeds the specified threshold value.

When the vehicle is cornering, the transverse positioning error due to a possible error in the pilot control depends not only on an offset error in the curvature, but also on the inaccuracy of the stored vehicle parameters, in particular on uncertainties in the vehicle's own steering gradient. Incorrect curvature pre-control of the vehicle can have the effect of disrupting the lateral control of the vehicle and thereby proportionally cause an additional lateral positioning error. This additional transverse placement error can lead to incorrect intervention by the calibration function, which can advantageously be avoided or reduced by suspending the calibration function or at least the temporal integration of the transverse placement error by the calibration function.

The effect of an error in the curvature precontrol on the driving operation or the lateral position of the vehicle can depend in particular on the vehicle speed. To take into account This speed dependence can therefore be provided that the temporal integration of the lateral offset error is stopped by the calibration function when the product of the square of the current vehicle speed and the curvature value of the road exceeds a predetermined threshold value, and / or when the product of the square of the current vehicle speed and the curvature value of the target trajectory exceeds a predetermined threshold value.

In a preferred embodiment, according to the invention, the temporal integration of the lateral positioning error is stopped and/or the application of the calibration value to the manipulated variable is suspended when a steering intervention by a driver of the vehicle generates a steering torque above a predetermined threshold value and/or a steering torque that increases the current lateral positioning error. This can advantageously prevent transverse offset errors, which arise as a result of a conscious driving intervention, from finding their way into the calibration value determined by the calibration function, since these transverse offset errors are not due to an offset of a sensor or the like that needs to be compensated. An influence on the calibration value of a lateral offset from the target trajectory, which is deliberately caused by a driver and has no origin in the lane guidance function, is thus advantageously avoided.

According to the invention, it can be provided that in the event of a steering intervention by a driver of the vehicle, who generates a steering torque that reduces the current lateral positioning error, the temporal integration of the lateral positioning error takes place at least for a predetermined period of time with an increased weighting, in particular with an increased integration coefficient.

If the driver himself makes a steering intervention that generates a steering torque that acts in the same direction as the calibration value generated by the calibration function, this can be viewed as a confirmation of the adaptation direction of the calibration function. Using an increased weighting or an increased integration value in this case advantageously enables improved calibration dynamics through the calibration function. From the driver's perspective, this means that he can shift the vehicle's course laterally more towards the center of the lane and the course will remain there in the future, even if he reduces the corrective steering torque.

In a preferred embodiment, it can be provided according to the invention that several integrating functions are used, with the integrating functions each being assigned a different speed interval, the integrating functions each integrating the transverse offset error in time at a speed of the vehicle that lies within the speed interval assigned to them, the calibration value of the Integration function, the speed interval of which includes the current speed of the vehicle, or a total calibration value determined depending on this calibration value is applied to the manipulated variable.

As described above, the effect of offset sizes on the lateral offset error is partially dependent on the speed of the vehicle. This applies, for example, to the offset errors that are contained in an output variable of a sensor interference compensation, or to the offset error that is part of a curvature precontrol. In order to keep the transverse offset error as low as possible, the calibration value switched to the manipulated variable can also be determined depending on the speed. Particularly due to the high integration time constants and the associated low dynamics, the adaptation of the calibration value of an individual calibration function to the changed driving speed can take a relatively long time, during which the accuracy of the tracking can be reduced.

In order to take this circumstance into account, it is advantageous to use a plurality of calibration functions instead of a single calibration function for the entire vehicle speed range. Each of the calibration functions can determine its own calibration value and, in particular, store it separately from the other calibration values. The ability to store the calibration values separately, for example by storing them in a non-volatile memory, ensures that they can then be continuously expanded through temporal integration during continued operation or that all states of the plurality of calibration functions are initialized separately when the vehicle is restarted can.

The entire range of possible vehicle speed can in particular be divided into several sub-intervals, each of which only covers a limited speed range and each of which is assigned a dedicated calibration function. The manipulated variable is assigned the calibration value of the calibration function, which is assigned to the speed interval in which the current speed of the vehicle. This means that only a single calibration function is always active, while the remaining calibration functions, in particular the temporal integration of the transverse offset error by the other calibration functions, are stopped or an input signal from zero is switched to their inputs. The currently active calibration function can, however, be supplied with the current transverse offset error. The transverse offset error can be weighted with a constant weighting factor or integrating coefficient or via a weighting factor or integrating coefficient that depends on the driving speed. The calibration value of the integration function, the speed interval of which includes the current speed of the vehicle, or a total calibration value determined depending on this calibration value is then applied to the manipulated variable. The advantage of using a plurality of calibration functions or a bank of calibration functions compared to using a single calibration function is particularly evident when accelerating or braking and thus when the speed ranges of the vehicle change frequently.

According to the invention, the total calibration value can be determined from two or more of the calibration values generated by the integrating functions in such a way that the total calibration value is continuous over time even when changing between two or more of the speed intervals. In this way, jerky changes in the calibration value switched to the manipulated variable and thus jerky interventions when changing the calibration functions due to a change in the speed of the vehicle are avoided.

In a preferred embodiment, an integration value of the calibration function assigned to the calibration function can be determined by the calibration functions through the temporal integration of the transverse offset error, wherein the integration values of the one or more integration functions in which the current speed lies outside the respective speed interval, continuously, in particular with a constant or a vehicle speed-dependent rate, to the integration value of the calibration function, in whose speed interval the current speed of the vehicle lies.

In order to avoid that when using the function for automatic tracking, primarily in a narrow speed range, only a few or only a single calibration function is charged with the lateral offset error and therefore only these ultimately correctly map the current offset situation, the current ones can also be used Speed, inactive calibration functions continue to integrate the current transverse offset error over time. The integration values, i.e. the integrator states of the calibration functions, which are each assigned to a region adjacent to the current speed range, are limited to a maximum of the value of the integration value of the calibration function assigned to the current speed range. In addition, the weighting factors or the integrating coefficients of the calibration functions assigned to non-current speed ranges can advantageously be reduced compared to the active case, since if the integrating coefficients remain unchanged, the advantage of subdividing into several integrator states would disappear. The extent to which the neighboring integration coefficients are reduced depends on the expected maximum sensor drift sizes and is, for example, in the order of 10% to 20%. This can prevent the typical drift of the offset variables for curvature, yaw rate and lateral acceleration from causing the states of the inactive calibration functions to increasingly lose their relevance and thus temporarily leading to a larger lateral offset error and reduced driving comfort when entering an adjacent speed range, until the Adaptation to the current offset situation is complete.

The continuous adjustment of the integration values of the one or more integration functions, in which the current speed lies outside the respective speed interval, in particular at a constant or a vehicle speed-dependent rate, to the integration value of the calibration function, in whose speed interval the current speed of the vehicle lies, can be considered that Implementing a forgetting factor can be considered. The states of the inactive calibration functions approach the state of the currently active calibration function, for example with a uniform or predetermined gradient that is individually defined for the respective speed range.

For a control device according to the invention for generating a manipulated variable for at least one lateral guidance actuator of a vehicle, it is provided that the control device is set up to carry out a method according to one of the preceding claims. The control device can also be set up to carry out lateral control, to determine the target trajectory and/or to carry out curvature pre-control. Alternatively, the control unit can only implement some of these functions. The control device can be connected to at least one sensor of the vehicle, in particular at least one environmental sensor that at least partially detects the vehicle's surroundings and/or at least one speed sensor that detects the speed of the vehicle, and/or a navigation system of the vehicle.

For a vehicle according to the invention it is provided that it comprises at least one lateral guidance actuator and a control device according to the invention, the control device being set up to control the at least one lateral guidance actuator with the manipulated variable. The transverse guidance actuator can be, for example, a steering actuator, for example an electric motor servo drive of a front axle steering and/or a rear axle steering.

A computer program according to the invention is intended to include instructions which cause a control device to carry out a method according to the invention. The control device can in particular be a control device that can be connected to at least one transverse guidance actuator of a vehicle.

All of the advantages and refinements described above in relation to the method according to the invention also apply to the control device according to the invention, the vehicle according to the invention and the computer program according to the invention and vice versa.

• 1 ein Ausführungsbeispiel eines erfindungsgemäßen Kraftfahrzeugs,
• 2 ein Blockdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens zur Spurführung eines Fahrzeugs, und
• 3 ein Blockdiagramm mehrerer Kalibrierfunktionen des Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Further advantages and details of the invention emerge from the exemplary embodiments described below and from the drawings. These are schematic representations and show:

• 1 an embodiment of a motor vehicle according to the invention,
• 2 a block diagram of an exemplary embodiment of a method according to the invention for tracking a vehicle, and
• 3 a block diagram of several calibration functions of the exemplary embodiment of the method according to the invention.

In 1 an exemplary embodiment of a vehicle 1 is shown. The vehicle 1 can be, for example, a motor vehicle such as a passenger car or a truck. Furthermore, the vehicle 1 can also be a vehicle combination, which has, for example, a towing vehicle and one or more trailers. Alternatively, the method can also be used for other types of vehicles 1.

The vehicle 1 includes a control device 2, which is set up to carry out a method for tracking the vehicle 1. Furthermore, the vehicle 1 comprises at least one transverse guidance actuator 3, via which the transverse position of the vehicle 1 can be adjusted.

The transverse guidance actuator 3 is designed, for example, as a steering actuator, by means of which a front axle steering angle of the vehicle 1 can be adjusted automatically. The steering actuator can be designed, for example, as an electric servo motor. Additionally or alternatively, the or a further transverse guidance actuator 3 can also be a steering actuator for automatically adjusting a rear axle steering angle.

The control device 2 is set up to determine a manipulated variable by means of a transverse control depending on a lateral offset error 4 of the vehicle 1 relative to a predetermined target trajectory 5 (shown in dashed lines) and to adjust a transverse position of the vehicle 1 to the target trajectory 5 as a function of the manipulated variable . For this purpose, the control device 2 controls the transverse guidance actuator 3 with the manipulated variable. The lateral offset 4 describes, for example, the deviation between the target trajectory 5 related to the center of the vehicle 1 and the actual direction of movement 6 of the center of the vehicle in the transverse direction of the vehicle.

The deviation from the target trajectory can, as in 1 is shown, at a defined distance from the front edge of the vehicle 1 (look-ahead length), but also at other reference points. Other possible reference points are, for example, at the height of the rear axle or the front axle of the vehicle 1. The reference points are preferably on the longitudinal axis of the vehicle, but other reference points of the vehicle 1 that are locally fixed during the observation period are also conceivable.

In 2 is a block diagram of the exemplary embodiment of the method for automated lane guidance of the vehicle 1 carried out by the control device 2. The automatic lane guidance includes a lateral control 7, which regulates the lateral position of the vehicle 1 in order to maintain the target trajectory 4. The lateral control 7 generates a manipulated variable delta_setpoint for the lateral guidance actuator 3, which can be controlled, for example, directly or via an intermediate steering angle controller (not shown).

The lateral control 7 includes a trajectory sequence controller 8 for generating the manipulated variable delta_setpoint, a curvature precontrol 9, one or more interference compensators 10, for example for compensating for crosswinds, road inclinations and/or other effects, and a steering angle offset calibration 11. Using the trajectory sequence controller 8, a Control variable component delta_controller determined.

The curvature precontrol 9 determines a precontrol variable delta_vorst depending on a measured and/or predicted curvature value of a road traveled by the vehicle 1, the manipulated variable delta_soll containing the precontrol variable delta_vorst as a manipulated variable component. Accordingly, the one or more interference compensators 10 generate one or more manipulated variable components delta_komp and via the steering angle offset calibration 11 a manipulated variable component delta_offset.

Furthermore, at least one calibration function 12 is provided, which determines a calibration value delta_kalib. The calibration value delta_kalib is applied to the manipulated variable delta_soll generated by the lateral control 7. Through signal processing 13, a yaw rate g and a lateral acceleration a_lateral of the vehicle 1 are communicated to the at least one interference compensator 10 as input variables. For this purpose, the signal processing 13 can evaluate measured values recorded by different sensors of the vehicle 1, which describe a yaw rate and/or a lateral acceleration.

A transverse offset error delta_y is supplied to the calibration function 12 and the trajectory sequence controller 8 by a position detection and trajectory planning unit 14. The transverse offset error delta_y describes the in 1 shown lateral offset 4 between the target trajectory 5 and the actual direction of movement 6 or the actual position of the vehicle 1.

The position recognition and trajectory planning unit 14 further provides the curvature precontrol 9 with at least one measured and/or predicted curvature information kappa, which describes the curvature of the target trajectory 5 in a section of the target trajectory 5 lying in front of the vehicle 1 in the direction of travel. The position detection and trajectory planning unit 14 determines the target trajectory 5 and correspondingly also the curvature information kappa depending on surroundings data which are provided by an surroundings detection unit 15 of the vehicle 1. The surroundings detection unit 15 generates the surroundings data depending on surroundings measurement data, which are generated in particular by at least one surroundings sensor (not shown) which detects at least a partial area of the surroundings of the vehicle 1.

The functionality of blocks 8 to 15 can be implemented entirely or partially in the control device 7. The output variables of blocks 8 to 11 all represent components of the manipulated variable delta_soll. Furthermore, the manipulated variable delta_soll is supplied with the at least one calibration value delta_calib of the calibration function 12.

The individual components of the manipulated variable delta_setpoint and the at least one calibration value delta_kalib have different effects on the tracking of the vehicle 1, which are described below.

wobei der Parameter I dem Radstand und EG dem Eigenlenkgradienten des Fahrzeugs 1 entspricht. Der Eigenlenkgradient hängt über $$\text{EG}=\text{m}*\left(\text{ch}*\text{lv}-\text{cv}*\text{lv}\right)\text{/}\left(\text{ch}*\text{cv}*(\text{lh}+\text{lv}\right))$$

von dem Abstand des Schwerpunkts von einer Vorderachse Iv bzw. einer Hinterachse Ih des Fahrzeugs 1, von der Fahrzeugmasse m des Fahrzeugs 1 und den Schräglaufsteifigkeiten der Reifen vorne cv und hinten ch ab.The target steering angle component delta_vorst of the curvature precontrol 9 is calculated, for example, as $$\text{delta\_vorst}=\text{kappa}*\left(\text{I}+\text{EC}*\text{v}2\right),$$

where the parameter I corresponds to the wheelbase and EG corresponds to the self-steering gradient of vehicle 1. The self-steering gradient hangs over $$\text{EC}=\text{m}*\left(\text{ch}*\text{lv}-\text{cv}*\text{lv}\right)\text{/}\left(\text{ch}*\text{cv}*(\text{lh}+\text{lv}\right))$$

from the distance of the center of gravity from a front axle Iv or a rear axle Ih of the vehicle 1, from the vehicle mass m of the vehicle 1 and the lateral stiffness of the tires at the front cv and rear ch.

gegeben ist. Die Folge des mit delta_vorst_kappaoff fehlerbehafteten Vorsteuerwerts delta_vorst ist, dass dieser quasi wie eine Störung auf die Querregelung 7 wirkt und das Fahrzeug 1 bei Aktivierung einer Spurhalteassistenz nicht wie erwartet der Solltrajektorie 5 folgt, sondern je nach Ausführung des Trajektorienfolgereglers 8 - d.h. Verwendung von Reglertypen mit oder ohne stationäre Genauigkeit - einen permanenten lateralen Versatz 4 zur geplanten Solltrajektorie 5 aufweist oder zumindest eine transientes Ausscheren bedingt, bevor das Fahrzeug 1 dann nach Abklingen eines Ausgleichsvorgangs der geplanten Solltrajektorie 5 folgt.If the curvature information kappa now has an offset kappa_offs compared to the actual curvature due to an error, the pilot-controlled target steering angle also contains an offset component delta_vorst_kappaoff, which is due to $$\text{delta\_vorst\_kappaoff}=\text{kappa\_offs}*\left(\text{I}+\text{EC}*\text{v}2\right)$$

given is. The consequence of the pre-control value delta_vorst, which is faulty with delta_vorst_kappaoff, is that it acts like a disturbance on the lateral control 7 and the vehicle 1 does not follow the target trajectory 5 as expected when a lane keeping assistance is activated, but depending on the version of the trajectory sequence controller 8 - ie use of controller types or without stationary accuracy - has a permanent lateral offset 4 to the planned target trajectory 5 or at least causes a transient departure before the vehicle 1 then follows the planned target trajectory 5 after a compensation process has subsided.

The degree of imaging errors of a camera used as an environment sensor, which supplies environment measurement data to the position detection and trajectory planning unit 14, usually varies over the operating period of the driver assistance system, since calibration routines of the camera are typically carried out continuously. This means that, depending on the status of the calibration, the height of the offset of the curvature precontrol 9 and thus the degree of impairment of the vehicle lateral guidance varies over time, although the transmission properties of the camera and thus also the offset of the curvature usually do not change suddenly, but rather in a band-limited manner.

It is possible for the steering angle to be used as an auxiliary or controlled variable within a lane guidance driver assistance system. This steering angle can be influenced or corrected by the steering angle calibration routine 11. A steering angle offset delta_offset determined in this way usually has an uncompensated portion due to the finite accuracy of the steering angle calibration routine 11.

A remaining offset error delta_offset_error in the steering angle signal can have several causes. Typically, a steering angle calibration routine 11 is usually based on the signal from a yaw rate sensor of the vehicle 1 and/or a wheel speed sensor system of the vehicle 1. Errors in these sensors, such as offset and linearity errors, can thus propagate towards the determined steering angle offset. The effects of steering angle offsets are comparable to the case of a curvature offset described above; here too, when the lane guidance driver assistance system is activated, the vehicle 1 does not follow the target trajectory 5 as expected, but instead has a permanent or transient lateral one, depending on the design of the trajectory follower controller 8 Offset 4 to the planned target trajectory 5, which can have adverse effects on the comfort and acceptance of the driver assistance system.

mit und den geschwindigkeitsabhängigen Reglerfaktoren Kp(v) und Kd(v), so ergibt sich mit dem den lateralen Versatz 4 beschreibenden Querablagefehler delta_y als Eingangsgröße und delta_regler als Ausgangsgröße des Trajektorienfolgereglers 8 $$\text{delta\_reglers}\left(\text{s}\right)=\text{Gr}\left(\text{s}\right)*\text{delta\_y}\left(\text{s}\right).$$

For example, a PD controller with the transfer function is used as the trajectory sequence controller 8 $$\text{Gr}\left(\text{s}\right)=\text{Kp}\left(\text{v}\right)+\text{s}*\text{Kd}\left(\text{v}\right)\text{/}\left(1+\text{s}*\text{T}\right),$$

with and the speed-dependent controller factors Kp(v) and Kd(v), the transverse offset error describing the lateral offset 4 results in delta_y as the input variable and delta_regulator as the output variable of the trajectory sequence controller 8 $$\text{delta\_controllers}\left(\text{s}\right)=\text{Gr}\left(\text{s}\right)*\text{delta\_y}\left(\text{s}\right).$$

zu $$\text{delta\_y}=\text{delta\_offset\_error}/\text{Kp}\left(\text{v}\right)$$

im Zeitbereich. Der Reglerfaktor Kp kann beim Entwurf nicht beliebig groß gewählt werden, wodurch sich bei einem unkompensierten Lenkwinkeloffset delta_offset_error ungleich null stets ein lateraler Versatz 4 des Fahrzeugs 1 zu der Solltrajektorie 5 ausbildet. Ein nicht kompensierter Offset eines Hinterachslenkwinkels bei einer Hinterachslenkung des Fahrzeugs 1 hat dabei eine vergleichbare Auswirkung auf den lateralen Versatz 4 des Fahrzeugs 1 wie ein unkompensierter Offset des Vorderachslenkwinkels.Consequently, the trajectory sequence controller 8 will output the uncompensated steering angle offset delta_offset_error in the stationary equilibrium state when driving straight ahead, that is, with a physical steering angle of zero degrees, and neglecting lateral disturbing forces on the vehicle 1. The lateral offset 4 required for this results from $$\text{Delta\_y}\left(0\right)*\text{Gr}\left(0\right)=\text{Delta\_offset\_error}\left(0\right)$$

to $$\text{delta\_y}=\text{delta\_offset\_error}/\text{Kp}\left(\text{v}\right)$$

in the time domain. The controller factor Kp cannot be chosen to be as large as desired during the design, which means that if the steering angle offset delta_offset_error is unequal to zero, a lateral offset 4 of the vehicle 1 to the target trajectory 5 is always formed. An uncompensated offset of a rear axle steering angle during rear axle steering of the vehicle 1 has a comparable effect on the lateral offset 4 of the vehicle 1 as an uncompensated offset of the front axle steering angle.

The sensor signals for the yaw rate, the front and rear axle steering angle and also the lateral acceleration are used in particular to estimate disruptive forces and load moments that act on the vehicle 1, for example as a result of a road inclination and/or crosswind acting on the vehicle 1. The determined forces and moments then contribute proportionately to the steering angle setpoint delta_soll in the course of the delta_comp disturbance variable input.

Furthermore, these sensors can also be used to estimate a slip angle of the vehicle 1, which can also be used as an auxiliary variable in the load estimates. Offset errors in the yaw rate g, the steering angle or the lateral acceleration a_lateral often have, in a stationary case, an impact on the estimated variables and thus also on the disturbance variable input that is proportional to the respective offset. Consequently, offset errors in the yaw rate g, the steering angle and also the lateral acceleration a_lateral are propagated to the disturbance-compensating portion of the steering angle setpoint delta_soll. The result here too is an undesirable transient or permanent lateral offset of the track-guided vehicle 1 from the planned target trajectory 5. Disturbance compensators 10 for the yaw rate g and the lateral acceleration a_lateral also generally have a finite accuracy, analogous to the steering angle compensation 11, and can therefore correspond to the real offset lag, which means that the previously described adverse effects on the driving comfort of the vehicle 1 can occur even in the presence of these when using the lane guidance driver assistance system.

These effects are addressed and at least partially compensated for by the at least one calibration function 12, resulting in improved driving comfort of the vehicle 1. The calibration function 12 is superimposed on the lateral control 7 and generates the at least one calibration value delta_calib applied to the manipulated variable delta_soll. The calibration value delta_kalib is determined by the at least one calibration function 12 at least partially as a function of a temporal integration of the transverse offset error delta_y.

Depending on the sign and amplitude of the transverse offset error delta_kalib, the calibration function 12 determines a calibration value delta_kalib for the target steering angle delta_soll, which is always aimed at reducing the transverse offset error delta_y, particularly with regard to the effective direction. This calibration value delta_kalib is then finally added to the manipulated variable delta_soll from the manipulated variable components of the trajectory sequence controller 8, the curvature precontrol 9, the one or more interference compensators 10 and the output of the steering angle offset calibration 11 and as a calibrated manipulated variable delta_soll_kalib, for example, to a target steering angle interface of the lateral guidance actuator 3 switched on. Alternatively, it is also possible to connect the calibrated manipulated variable to a torque interface of the transverse guidance actuator 3.

The calibration function 12 can, for example, be designed as an integrator or as an I-term with a comparatively small integration coefficient ki, so that the calibration function 12 integrates the transverse offset error with a low dynamic. Alternatively, it is also possible to implement the calibration function as a PT1 element or as a different type of function with at least partially integrating behavior.

ausgedrückt werden.The determination of the calibration value delta_kalib by the calibration function 12 can therefore be carried out when the calibration function 12 is executed as an integrator with the integrating coefficient ki, for example as $$\text{Delta\_calib}=\text{Delta\_y}*\text{ki}/\text{s}$$

be expressed.

The time constant of the calibration function 12 is in particular greater by at least a factor of 2, at least a factor of 5, at least a factor of 10, at least a factor of 100 or at least a factor of 1000 than the dominant time constant of the lateral control 7 or . of the trajectory sequence controller 8. The integration coefficient ki is, for example, in the order of magnitude of 0.001 degrees/(m*s), so that the gradient of the calibration value 12 is only 0.0002 degrees/s with a transverse offset error delta_y of 0.2 m, assumed as an example for purposes of illustration.

The adaptation dynamics of the calibration value 12 is preferably dimensioned such that it is in the order of magnitude of the change dynamics of the offset errors described above. A measure for this is, for example, the largest expected, temperature-related offset drift of the sensors used for the lateral control 7, for example converted to the corresponding steering angle plane. If the dynamics were to be chosen to be significantly larger, a typical overshoot would occur in the signal for delta_calibre, since the calibration would then partially compete with the transient behavior of the compensation functions 10 for road side inclination or crosswind. However, this could again have a limiting effect on the increase in comfort through the calibration function 12.

The calibration function 12 determines an integration value of the calibration function 12 through the temporal integration of the transverse offset error delta_y. This integration value represents the result of the temporal integration of the transverse offset error delta_y at a specific point in time. The integration value is retained when the tracking guidance is deactivated and when the tracking guidance is reactivated used as the starting value of the renewed temporal integration of the lateral offset error delta_y. The state of the calibration function 12, for example designed as an integrator, is not reset in the current ignition run, but is maintained even when the driver assistance is repeatedly deactivated and activated, when the journey is ended and/or when driver interventions overwrite the automatic lane guidance.

The use of a constant integration coefficient ki in the calibration function 12 can represent a compromise for the entire speed range that can be reached by the vehicle 1, since the influence of offset variables on the transverse offset error delta_y can depend on the driving speed. This can be due, for example, to the commonly used controller parameter control of the trajectory sequence controller 8 depending on the driving speed. This also changes the interference compensation property of the trajectory sequence controller 8 and consequently also the effect of sensor offset variables on the transverse offset error delta_y.

In order to take this circumstance into account and expand the potential of the calibration function, it can be provided that the temporal integration of the transverse offset error delta_y takes place with a weighting factor, in particular the integration coefficient ki, which depends on a speed of the vehicle. The integration coefficient ki can therefore be made dependent on the current speed of the vehicle 1 as ki(v). This advantageously results in an individually adaptable calibration dynamic of the calibration function 12 that is ideal for every driving speed range.

Additionally or alternatively, it can be provided that the weighting factor or the integrating coefficient ki increases as the magnitude of the transverse offset error delta_y increases. The calibration speed of the calibration function 12 can be effectively increased by an additional non-linear or progressive weighting of the amount of the transverse offset error delta_y.

For example, the integration coefficient ki and thus the adaptation rate are switched between two or more values, with the integration coefficient ki being chosen higher for larger absolute values of the transverse offset error delta_y. For example, doubling the integration constant ki for an amount of the lateral offset error delta_y of, for example, greater than 0.2 m can lead to a faster initial adaptation to an existing offset situation when the driver assistance function is started.

Even if the sensor compensators 10 and/or other sensor offset calibration functions in the vehicle 1 finally correct a detected offset drift of a sensor after a debounce time has elapsed with a sudden correction of the respective offset, a definition of the adaptation rate of the calibration function 12 can be made depending on the The amount of the transverse offset error delta_y ensures a faster adjustment to the new offset situation. This is particularly advantageous for comparatively long debounce times of the sensor compensators 10 or other sensor offset calibration functions, since during such a debounce time the calibration function 12 increasingly carries out compensation, which returns again after a signal update of the sensor compensators or sensor offset calibration functions needs to be integrated.

Since sudden corrections of a sensor offset directly lead to a lateral jerk of the vehicle 1, which depends on the jump height, it can be provided as an advantageous extension that all sensor offset calibration functions in the vehicle 1 do not change the respective sensor offset abruptly, but only in a band-limited manner. The offset compensations for the vehicle happen sensors, for example, with a maximum of a defined maximum gradient, which the output of the centering calibration delta_calibre can always follow with a small tracking error of the order of 0.03 degrees, then the non-linear or progressive weighting of the amount of the transverse offset error delta_y in the calibration function 12 can also be dispensed with as a measure to increase dynamics.

The contribution of delta_kalib to the overall manipulated variable delta_soll_kalib is advantageously further limited in the maximum amplitude by a limitation of the integrator state in the calibration function 12. For this purpose, it can be provided that the temporal integration of the transverse offset error delta_y is stopped by the calibration function 12 when the or an integration value of the calibration function 12 determined by the temporal integration of the transverse offset error delta_y corresponds to a predetermined limit value.

The limit value or the maximum amplitude of the integrator or the calibration function 12 depends, for example, on the sum of the maximum influences of all offset variables on the steering angle setpoint delta_soll and the actual steering angle value. For example, if delta_komp, delta_vorst and delta_offset each have a maximum offset error of 0.05 degrees, then delta_kalib must be limited to an interval of +/- 0.15 degrees. The angle information refers to the steering angle of the vehicle, for example a steering angle on the front wheels of the vehicle. With this procedure, the otherwise necessary measures to avoid integrator windup effects in the calibration function 12 can advantageously be omitted.

As an alternative to limiting the integrator state, a low-pass filter function can also be used, for example a PT-1 filter. This can also avoid windup effects. Although the offset situation cannot be completely eliminated, the centering accuracy achieved can still be sufficient.

When cornering, the lateral positioning error due to a pilot control error depends not only on an offset error in the curvature, but also on the inaccuracy of the stored vehicle parameters, in particular on uncertainties in the self-steering gradient EG. The proportion of incorrect pre-control due to errors in the self-steering gradient EG is obtained by applying the total differential to equation (1) and evaluating for EG or its error EG_err as $$\begin{array}{l}\text{delta\_vorst\_EG\_err}=\left(\text{d delta\_vorst/d EG}\right)*\text{EG\_err}\\ =\left(\text{d}(\text{kappa}*\left(\text{I}+\text{EC}*\text{v}2\right)\right)\text{/ d EC})*\text{EG\_err}\\ =\text{kappa}*\text{<figure-callout id="2" label="v" filenames="DE102022209045A1\_0012.png,DE102022209045A1\_0013.png" state="{{state}}">v</figure-callout>}2*\text{EG\_err}\end{array}$$

Contributions from delta_vorst_EG_err have the effect of a disturbance on the lateral control of vehicle 1 and proportionally cause a lateral positioning error delta_y, which leads to an incorrect deflection of delta_kalib. The delta_kalib signal does not only react to sensor offset sizes. As long as EG_err is limited, the effect of EG_err on the vehicle level is only small due to the large integration time constant of the centering calibration. The integration time constant is defined as the reciprocal of the integration factor ki.

This also applies because incorrect deflection of delta_kalib in curves on the straight-ahead sections of the road is corrected. If EG_err varies significantly, the value for EG in the vehicle can be continuously adapted to the current circumstances such as vehicle mass m or tire stiffness using an adaptation algorithm, which reduces EG_err and thus also the contribution of delta_vorst_EG_err.

Furthermore, with a larger variation of EG_err, the calibration function 12 can be suspended at high values for the product kappa * v^2. It can therefore be provided that the temporal integration of the lateral offset error delta_y is stopped by the calibration function 12 when the product of the square of the current vehicle speed v and the curvature value kappa of the target trajectory 5 and / or the curvature value of the roadway exceeds a predetermined threshold value.

For this purpose, the curvature kappa is advantageously first low-pass filtered, for example using the PT-1 algorithm, and then the absolute value is subjected to a threshold value comparison that depends on the driving speed v. If the filtered curvature is above this threshold, the calibration function 12 is temporarily stopped.

Furthermore, it can be provided that the temporal integration of the transverse offset error delta_y is stopped by the calibration function 12 if the or a measured and / or predicted curvature value kappa of the or a road traveled by the vehicle 1 exceeds a predetermined threshold value and / or if a curvature value of the Target trajectory 5 exceeds a predetermined threshold value.

If the curvature temporarily has a larger offset error until the camera calibration has compensated for this error, this can temporarily reduce the calibration activity of the calibration function 12 for higher driving speeds. However, the adaptation range only shifts by the amount of the curvature offset, so that the calibration activity does not come to a complete standstill. In addition, if the driving speed v is reduced and the product kappa * v^2 is reduced, the calibration is carried out again more intensively.

Disturbances in the calibration can in particular also be caused by the driver intervening, who can directly influence the transverse positioning error delta_y, for example by steering on a steering wheel of the vehicle 1. As a remedy, the calibration function 12, i.e. the integration of the transverse offset error delta_y, can be stopped when the driver intervenes on the steering wheel. In particular, it is possible for the temporal integration of the transverse offset error delta_y to be stopped and/or for the control variable delta_soll to be subjected to the calibration value delta_calibre to be suspended if, due to a steering intervention by a driver of the vehicle 1, a steering torque M is above a predetermined threshold value and/or a current one Lateral offset error delta_y increasing steering torque M is generated.

However, higher availability and thus faster convergence of the calibration function 12 can be achieved by only stopping the calibration function 12 when the driver steers in the direction of an increase in the transverse offset error delta_y. This can be done by comparing the sign of the driver's steering torque M and the lateral positioning error delta_y. If, for example, the counting arrow of the driver's steering torque M is defined in such a way that steering to the left in the direction of travel requires a positive torque and a positive lateral positioning error means the positioning of the vehicle in the direction of travel to the right of the planned target trajectory 5, then the stop condition of the calibration function must be the sign of Driver steering torque M and lateral positioning error may be different.

The integration coefficient ki is initially made as a basic design for the execution of the lane assistance for steering interventions by the driver below a defined intensity, evaluated for example based on the level of the measured driver steering torque M. Additionally or alternatively, it can be provided that when a driver of the vehicle 1 makes a steering intervention, which generates a steering torque M that reduces the current lateral position error delta_y, the temporal integration of the lateral position error delta_y is carried out at least for a predetermined period of time with an increased weighting, in particular with an increased integration coefficient , he follows. This means that the integration coefficient can be specifically increased compared to the basic design if a driver intervention is detected and the driver simultaneously steers in the direction of reducing the transverse offset error delta_y. The driver's steering can be viewed as a confirmation of the calibration process of the calibration function 12, which justifies an increase in the calibration dynamics by increasing the integration coefficient ki.

As described, the effect of offset variables on the transverse offset error delta_y is partly dependent on the driving speed v. This applies, for example, to the offset errors that are contained in the output of the interference compensators delta_komp, or the offset error that is part of the curvature precontrol delta_vorst. When the driving speed changes, delta_calib must always change in order to keep the lateral positioning error low, although the offset variables in yaw rate g, lateral acceleration a_lateral and pilot control curvature kappa that cause the lateral positioning error are assumed to be constant in the analysis. Due to the high integration time constant of the calibration function 12 and thus the low dynamics of the calibration function 12, the adaptation to the changed driving speed v takes a relatively long time, during which the accuracy of the tracking is reduced.

In order to take this circumstance into account, it is advantageous to use an arrangement of several integrators or memories instead of a single integrator as a memory for delta_kalib for the entire vehicle speed range, as is the case, for example, in 3 is shown.

In 3 the use of several integrating functions 12_1 to 12_N is shown. Furthermore, an interpolation unit 16, an initialization unit 17, an integration coefficient determination unit 18 and a sequence control unit 19 are shown as part of the control device 2.

The integrating functions 12_1 to 12_N are each assigned a different speed interval, with the integrating functions 12_1 to 12_N each temporally integrating the transverse offset error delta_y at a speed of the vehicle 1 that lies within the speed interval assigned to them. The entire vehicle speed range is therefore subdivided into N>1 subintervals, each of which only covers a limited speed range and to which a calibration function 12 or a dedicated integrator is assigned. Thus, only a single calibration function 12 is active at a time, while the remaining calibration functions 12 are stopped or an input signal from zero is switched to their inputs. The active calibration function calibration function 12_1 to 12_N, on the other hand, is supplied with the weighted transverse offset error delta_y and each integrator generates its own delta_kalib_v(k), k = [1...N]. The calibration value delta_kalib_v(1) to delta_kalib_v(N) of the respective calibration function 12_1 to 12_N, whose speed interval includes the current speed of the vehicle 1, can be connected directly to the manipulated variable delta_setpoint as the resulting delta_kalib. The weighting of the transverse offset error delta_y can be done with a constant integration coefficient ki or via a factor ki(v) that depends on the driving speed.

The integration coefficient ki or ki(v) can be determined for the individual calibration functions 12_1 to 12_N by the integration coefficient determination unit 18. For this purpose, the integration coefficient determination device 18 can receive as input variables, for example, the vehicle speed v, the steering torque M of a driver of the vehicle 1, the current lateral offset error delta_y and the measured or predicted curvature kappa.

The centers of the N vehicle speed intervals essentially represent the support points for the output values delta_kalib_v(k). In order to obtain a resulting delta_kalib from the individual contributions delta_kalib_v(k), an additional or alternative one can be used by the interpolation unit 16 from the calibration values delta_kalib_v(1). The total calibration value delta_kalib_ges determined up to delta_kalib_v(N) is applied to the manipulated variable delta_soll. The overall calibration value delta_kalib_ges is determined from two or more of the calibration values delta_kalib_v(1) to delta_kalib_v(N) generated by the integrating functions 12, in particular in such a way that the overall calibration value delta_kalib_ges is continuous over time even when changing between two or more of the speed intervals. This can be implemented by the interpolation unit 16, for example, via linear interpolation, with the interpolation unit receiving the vehicle speed v as an input variable.

mit $$\text{a}=\left(\text{v}-\text{v}(\text{k}\right))/\left(\text{v}(\text{k}+1\right)-\text{v}\left(\text{k}\right)),\text{ v}>\text{v}\left(\text{k}\right)),\text{ v}<\text{v}\left(\text{k}+1\right)$$

For this purpose, for example, depending on the two distances between the current driving speed and the two centers of adjacent speed ranges, delta_kalib_ges is linearly combined from delta_kalib_v(k) and delta_kalib_v(k+1). It applies $$\text{delta\_kalib\_ges}=\text{delta\_kalib\_v}\left(\text{k}\right)*\text{a}+\text{delta\_kalib\_v}\left(\text{k}+1\right)*\left(1-\text{a}\right)$$

with $$\text{a}=\left(\text{v}-\text{v}(\text{k}\right))/\left(\text{v}(\text{k}+1\right)-\text{v}\left(\text{k}\right)),\text{v}>\text{v}\left(\text{k}\right)),\text{v}<\text{v}\left(\text{k}+1\right)$$

An interpolation between the individual integrator states delta_kalib_v(k) is also advantageous because no jump in delta_kalib_ges occurs when changing from one speed range to another. Jumps in the steering angle setpoint delta_soll_kalib lead to a lateral jerk of the vehicle 1 and should be avoided for reasons of driving comfort. The advantage of using a bank of calibration functions 12_1 to 12_N or a bank of integrators compared to using a single integrator is particularly evident when accelerating or braking and thus the frequent change of speed ranges.

If the driver assistance function is primarily operated in a narrow speed range, the case may arise that only one of the calibration functions 12 is charged according to the transverse offset error delta_y, so that only this calibration function 12 correctly reflects the current offset situation. Due to the typical drift of the offset variables for curvature kappa, yaw rate and lateral acceleration a_lateral, the states of the remaining integrators increasingly lose their relevance.

When entering a neighboring speed range, a larger lateral offset error delta_y could temporarily occur and at the same time reduced driving comfort until the adaptation to the current offset situation is completed. A forgetting factor can be an advantageous remedy be implemented. For this purpose, it can be provided that an integration value of the calibration function 12_1 to 12_N assigned to the calibration function 12_1 to 12_N is determined by the calibration functions 12_1 to 12_N through the temporal integration of the transverse offset error, the integration values of the one or more integration functions in which the current speed is outside of the respective speed interval is, continuously, in particular at a constant or a vehicle speed-dependent rate, adapted to the integration value of that calibration function 12_1 to 12_N in whose speed interval the current speed of the vehicle 1 lies.

Here, for example, all integrator states or integration values of the inactive calibration functions 12_1 to 12_N strive for the state or integration value of the currently active calibration function 12_1 to 12_N with a uniform or predetermined gradient that is individually defined for the respective speed range. This gradient can, for example, depend on the dynamics of change in the offset sizes. In the application, it can advantageously be dimensioned so that it corresponds to 25% of the resulting gradient for delta_kalib_v(k) for a transverse offset error of 0.2 m. If the equalizing gradient is chosen too high, the advantage of using a bank of calibration functions 12_1 to 12_N compared to using a single calibration function 12 disappears.

As an alternative to the gradient method carried out, the calibration functions of the currently irrelevant speed ranges can be continued with integration coefficients reduced to, for example, 10% to 20%. With this approach, the integrator states are prevented from exceeding the integrator state of the currently active speed range through appropriate limitations.

Depending on the dynamics of the offset influences, it may be advantageous to write the state of a single calibration function 12 or all states of a plurality of calibration functions 12_1 to 12_N into a non-volatile memory, for example a memory of the control device 3, in order to be able to do so when the ignition is restarted Vehicle 1 to be able to set up the already calibrated states of the one or more calibration functions 12 or 12_1 to 12_N. This is particularly advantageous if the majority of the offset errors have no or only a small time drift.

The states or the integrating values of the one or more calibration functions 12_1 to 12_N can be saved by the initialization unit 17. The initialization unit 17 can also initialize the calibration functions 12_1 to 12_N and carry out a status comparison between the calibration functions 12_1 to 12_N or their current integration values.

The sequence control unit 19 can, for example, activate and/or deactivate the automatic tracking, the occurrence of a condition for stopping a temporal integration and/or for applying the manipulated variable delta_setpoint to the at least one calibration value delta_calib, the change between the speed intervals and/or other events understand and accordingly effect operation of the at least one calibration function 12.

In its basic function, the calibration function 12 can also be viewed as a form of an integral component in the trajectory sequence controller 8, but preferably has the essential properties or the essential differences that the integration coefficient or another weighting factor used for the temporal integration of the transverse offset error delta_y contrary to the design criteria typical for a transverse control 7, is very low and/or that the calibration function 12 or the temporal integration of the transverse offset error delta_y is not initialized with zero when the assistance system is restarted, but is based on or adopts the last state reached. The advantage of this is that the vehicle 1 has virtually no lateral transient response when the driver assistance function is activated, but can travel directly along the planned target trajectory 5. The extensions of the at least one calibration function 12 described above also represent further differences to a classic integral component of a lateral control controller.

The at least one calibration function 12 can be carried out as a separate function or, alternatively, can be implemented in addition to an already existing integral component in the trajectory sequence controller 8. The at least one calibration function 12 will in particular only carry out an adaptation in the activation phases of the driver assistance system until the integral component of the trajectory sequence controller 8 has reduced the transverse offset error delta_y to zero or whenever the integral component of the trajectory sequence controller 8 is reset and resets itself must build. This can occur, for example, for a Level 2 autonomous driving system when the driver turns.

In general, the calibration dynamics of the calibration function 12, ie the time required until the lateral offset 4 of the vehicle 1 has been adapted to the current offset situation, can be greater than in a driver assistance system without an integral component in the trajectory sequence controller 8. This Circumstances can be at least partially addressed by increasing the integrating coefficient or coefficients when using the one or more calibration functions 12 with a trajectory sequence controller 8 without an integral component. Furthermore, when using an integral component in the trajectory sequence controller 8, one or more of the interference compensations 10 for crosswind and/or road inclination can be dispensed with. The result of this is that a significant source of offset errors is eliminated and therefore fewer offset effects have to be taken into account by the calibration function 12, which advantageously results in a lower requirement for the calibration dynamics of the at least one calibration function 12.

QUOTES INCLUDED IN THE DESCRIPTION

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Cited patent literature

• DE 102008026233 B4 [0012]

Claims (16)

Method for tracking a vehicle (1), wherein a manipulated variable is determined by a lateral control (7) depending on a lateral offset error (4) of the vehicle (1) relative to a predetermined target trajectory (5), wherein a lateral position of the vehicle ( 1) is adjusted to the desired trajectory (5) depending on the manipulated variable, characterized in that the manipulated variable is additionally subjected to at least one calibration value, the calibration value being determined by at least one calibration function (12) at least partially as a function of a temporal integration of the transverse offset error . Procedure according to Claim 1 , characterized in that the time constant of the calibration function (12), in particular by at least a factor of 2, is greater than the dominant time constant of the lateral control (7). Procedure according to Claim 1 or 2 , characterized in that an integration value of the calibration function (12) is determined by the temporal integration of the transverse offset error, the integration value being retained when the tracking is deactivated and used as the starting value of the temporal integration of the transverse offset error when the tracking is reactivated. Method according to one of the preceding claims, characterized in that the lateral control (7) comprises a pilot control (9), wherein the pilot control (9) determines a pilot control variable depending on a measured and / or predicted curvature value of a road traveled by the vehicle (1). , where the manipulated variable contains the input control variable as a component. Procedure according to Claim 4 , characterized in that the pre-control takes place as a function of a vehicle model describing a self-steering gradient of the vehicle, the self-steering gradient being adjusted during operation of the vehicle as a function of at least one vehicle parameter, in particular a vehicle mass and/or a tire stiffness. Method according to one of the preceding claims, characterized in that the temporal integration of the transverse offset error takes place with a weighting factor, in particular an integrating coefficient, which depends on a speed of the vehicle (1) and/or increases as the amount of the transverse offset error increases. Method according to one of the preceding claims, characterized in that the temporal integration of the transverse offset error is stopped by the calibration function (12) if: - the or an integration value of the calibration function (12) determined by the temporal integration of the transverse offset error corresponds to a predetermined limit value, - the or a measured and/or predicted curvature value of the or a road traveled by the vehicle (1) exceeds a predetermined threshold value, - a curvature value of the target trajectory (5) exceeds a predetermined threshold value, - the product of the square of the current vehicle speed and the curvature value the roadway exceeds a predetermined threshold value, and/or - the product of the square of the current vehicle speed and the curvature value of the target trajectory (5) exceeds a predetermined threshold value. Method according to one of the preceding claims, characterized in that the temporal integration of the transverse positioning error is stopped and/or the application of the calibration value to the manipulated variable is suspended if a steering intervention by a driver of the vehicle (1) results in a steering torque above a predetermined threshold value and/or a steering torque that increases the current lateral positioning error is generated. Method according to one of the preceding claims, characterized in that in the event of a steering intervention by a driver of the vehicle (1), who generates a steering torque that reduces the current lateral positioning error, the temporal integration of the lateral positioning error is carried out at least for a predetermined period of time with an increased weighting, in particular with an increased one Integrating factor takes place. Method according to one of the preceding claims, characterized in that several integrating functions (12) are used, the integrating functions (12) each being assigned a different speed interval, the integrating functions (12) each being at one within the The speed of the vehicle (1) based on the speed interval assigned to them can integrate the lateral offset error over time, with the calibration value of the integration function (12), whose speed interval includes the current speed of the vehicle (1), or a total calibration value determined depending on this calibration value being applied to the manipulated variable . Procedure according to Claim 10 , characterized in that the total calibration value is determined from two or more of the calibration values generated by the integrating functions (12) in such a way that the total calibration value is continuous over time even when changing between two or more of the speed intervals. Procedure according to Claim 10 or 11 , characterized in that an integration value of the calibration function (12) assigned to the calibration function (12) is determined by the calibration functions (12) through the temporal integration of the transverse offset error, the integration values of the one or more integration functions in which the current speed is outside the respective speed interval, continuously, in particular at a constant or a vehicle speed-dependent rate, to the integration value of the calibration function (12), in whose speed interval the current speed of the vehicle (1) lies. Method according to one of the preceding claims, characterized in that the at least one calibration function (12) is each designed as an I element or as a PT1 element. Control device for generating a manipulated variable for at least one lateral guidance actuator (3) of a vehicle (1), the control device (2) being set up to carry out a method according to one of the preceding claims. Vehicle includes at least one lateral guidance actuator (3) and a control device (2). Claim 14 , wherein the control device (2) is set up to control the at least one transverse guidance actuator (3) with the manipulated variable. Computer program comprising instructions which cause a control device to carry out a method according to one of the Claims 1 until 14 to carry out.

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